AS03-A002
Cloud Water Resource in North China in 2017 Simulated by the CMA-CPEFS Cloud Resolving Model: Validation and Quantification
Chao TAN1+, Yuquan ZHOU2#
1The University of Hong Kong, Hong Kong SAR, 2China Meteorological Administration Weather Modification Center, China
Based on the concept of cloud water resource (CWR) and the cloud microphysical scheme developed by the Chinese Academy of Meteorological Sciences (CAMS), a coupled mesoscale and cloud-resolving model system is developed in the study for CWR numerical quantification (CWR-NQ) in North China for 2017. The results show that (1) the model system is stable and capable for performing 1-yr continuous simulation with a water budget error of less than 0.2%, which indicates a good water balance. (2) Compared with the observational data, it is confirmed that the simulating capability of the CWR-NQ approach is decent for the spatial distribution of yearly cumulative precipitation, daily precipitation intensity, yearly average spatial distribution of water vapor. (3) Compared with the CWR diagnostic quantification (CWR-DQ), the results from the CWR-NQ differ mainly in cloud condensation and cloud evaporation. However, the deviation of the net condensation (condensation minus evaporation) between the two methods is less than 1%. For other composition variables, such as water vapor advection, surface evaporation, precipitation, cloud condensation, and total atmospheric water substances, the relative differences between the CWR-NQ and the CWR-DQ are less than 5%. (4) The spatiotemporal features of the CWR in North China are also studied. The positive correlation between water vapor convergence and precipitation on monthly and seasonal scales, and the lag of precipitation relative to water vapor convergence on hourly and daily scales are analyzed in detail, indicating the significance of the state term on hourly and daily scales. The effects of different spatial scales on the state term, ad- vection term, source–sink term, and total amount are analyzed. It is shown that the advective term varies greatly at different spatiotemporal scales, which leads to differences at different spatiotemporal scales in CWR and related characteristic quantities.
AS03-A005
Aerosol Susceptibilities on the Wintertime Stratocumulus Clouds Over the Northwest Pacific Ocean
Chung-Kai WU+, Jen-Ping CHEN#
National Taiwan University, Taiwan
Aerosol indirect effects, including the Twomey and Albrecht effects, remain a major uncertainty in current weather and climate studies. Such effects are found to vary with cloud types, and the vulnerability is often evaluated with a metric called susceptibility -- the derivatives of the measured variable to aerosol concentration. In this research, the Weather Research and Forecasting model v4.3.1 combined with the NTU microphysical scheme is used to investigate the aerosol susceptibility of marine boundary-layer clouds over the NW Pacific Ocean during cold-air outbreak events. These clouds are often found in mixed-phase upstream and liquid-phase downstream of the cold air trajectory. We found distinctive features of aerosol susceptibility in both cloud types. In the liquid-phase stratocumulus clouds, most cloud properties (e.g., liquid water path, optical depth, and cloud albedo) have positive susceptibilities to the aerosol effects, consistent with earlier studies. However, the cloud fraction showed a negative susceptibility when drizzle is active. In the mixed-phase stratocumulus clouds, on the other hand, the cloud and ice water paths, as well as cloud fraction, are found to increase in the low-end and high-end aerosol concentrations but decrease when the aerosol concentration is between 102 and 104 cm-3. Such a nonlinearity is likely associated with the transition of precipitation formation from drizzle-dominated in low aerosol concentrations to ice-dominated at high aerosol concentrations.
AS03-A006
Role of Cloud Subgrid-scale Structure in Modulating Clouds Viewed by ISCCP, MODIS, and MISR Simulators
Xiaocong WANG#+
Chinese Academy of Sciences, China
The role of cloud subgrid-scale structure in modulating satellite views of clouds was investigated. This was realized by implementing a stochastic cloud generator into the CFMIP (Cloud Feedback Model Intercomparison Project) Observation Simulator Package together with surrogate clouds produced by a cloud- resolving model (CRM). The subgrid-scale structural parameters are decorrelation length for overlapping cloud fraction (Lcf), decorrelation length for overlapping cloud condensate (Lcw), and the shape parameter v for measuring cloud inhomogeneity. With the use of median values of Lcf, Lcw, and v derived from CRM, the simulated satellite views bear close resemblance to those using CRM-inherent clouds. Varying these parameters in the range of lower and upper quartiles leads to differences that are about one-fifth of those caused by changing cloud microphysics in CRM. While Lcf influences clouds throughout the whole troposphere, Lcw and
v result in changes mostly within the upper layers. Increasing (decreasing) cloud inhomogeneity or overlapping degree leads to decreased (increased) occurrence of clouds, except for high-topped clouds viewed by Multiangle Imaging Spectroradiometer. Care must then be exercised when interpreting model biases in comparison with different instruments. Sensitivity tests show changing condensate distribution from gamma to lognormal makes little impact on final results. Although the differences induced by any of the parameters alone are much limited, they are getting comparable to those seen between models and observations when all parameters are synergistically altered. This brings encouraging results to the modeling community that simulator-diagnosed clouds can be potentially improved by tuning cloud subgrid-scale parameters.
AS03-A012
A Critical Evaluation of Top-hat Approximation in Shallow Convection at Different Horizontal Scales
Zhao YAXIN1#+, Xiaocong WANG2, Yimin LIU2, Guoxiong WU2
1University of Chinese Academy of Sciences, China, 2Chinese Academy of Sciences, China
The top-hat approximation, which is widely used in the mass flux type convection, is verified at different horizontal scales, especially those at the limit of vanishing cloud fraction, with the aid of large eddy model simulations (LES). Three shallow convection cases in the Global Energy and Water Cycle Experiment (GEWEX) Cloud System Study (GCSS) programs are conducted, including BOMEX, RICO and ATEX. Results show that convective cloud fraction increases with the increase of horizontal resolution, consequently resulting in errors of cloud component in the decomposition of scalar flux increase. These errors are however largely compensated by the decrease of errors in the environment, leading to the error of top-hat approximation almost unchanged. For either cloud or environment component, there exists an inversed relationship between convective fraction and the covariance between vertical velocity and conserved tracer. This brings encouraging results to the modeling community that the mass-flux method in parameterizing convection still works at high resolutions. However, the closure remains a big problem at the limit of vanishing cloud fraction, which is not covered in this study.
AS03-A014
Comparison of ERA-5, JRA-55 and MERRA-2 on Diurnal Cycle of Precipitation and Associated Physical Processes
Yanjie LIU1#+, Xiaocong WANG2, Yimin LIU2
1University of Chinese Academy of Sciences, China, 2Chinese Academy of Sciences, China
Convective parameterization in numerical models remains an important source of model uncertainty, as evidenced in the deficiency in simulations of the diurnal cycle of precipitation (DCP). In this study, the behaviors of the phase and amplitude of DCP in China in three commonly used reanalysis products, including ERA-5, JRA-55 and MERRA-2, are compared against GPM (Global Precipitation Measurement) and CMORPH (Climate Prediction Center Morphing Technique). Results show while JRA-55 and ERA-5 produce DCP that are closely consistent with observation, MERRA-2 shows 1- to 3-hour shifts in phase and significantly underestimates the amplitude. Further analysis is performed by comparing 3-D cloud fraction, apparent heating (Q1) and apparent moisture sink (Q2) against cloud-resolving model (CRM) simulations. Only ERA-5 captures the evolution of clouds in association with convective precipitation as in CRM simulations, while the other two fail to reproduce such characteristics. This implies the need to link DCP with subgrid-scale processes besides convection and to treat physical parameterizations as an integrated system.
AS03-A015
Effect of the Low-level Jets on the Movement of the Mei-yu Front
Mu-Qun HUANG#+, Pay-Liam LIN
National Central University, Taiwan
The Mei-Yu front heavy rainfall event occurred in northern Taiwan on 2 June 2017. The largest daily accumulated rainfall was 645.5 mm at the north tip of Taiwan. The frontal system becomes quasi-stationary in northern Taiwan, and it lasts for 10 hours. A strong barrier jet over the northwest coast of Taiwan is present when the Mei-Yu front approaches northern Taiwan. The strong low-level jet brings abundant moisture to Taiwan and causes strong convergence along the frontal zone. The strong convection produces more than 600 mm of rainfall when the system becomes stationary. In order to examine how the barrier jet over northwestern Taiwan affects the movement of the Mei-Yu front, this study uses the WRF model to reproduce this heavy rain event. Meanwhile, three sensitivity tests are conducted in the numerical experiment. In the removing Taiwan terrain test, the front moves southward quickly. The accumulated rainfall was only 200 mm and the barrier jet is much weaker than the CTRL, showing that the orographic can obstruct the frontal movement. In the replacing southern Taiwan mountain test, northern Taiwan terrain provides part of the blocking effect, but the front still moves southward quickly without a strong barrier jet. In the enhanced barrier jet test with the same topography as CTRL, the barrier jet is slightly stronger than CTRL. The position of the stationary Mei-Yu front is further north than the CTRL. The strong southerly wind also enhanced the convergence, resulting in more rainfall, however, the rainfall did not fall over the land. The results show that the orographic effect contributed to part of the blocking effect for the frontal movement in northern Taiwan, and caused the barrier jet to form in northwestern Taiwan. The slow movement of the Mei-Yu front is significantly influenced by the barrier jet.
AS05-A009
Synoptic Control and Surface Condition of Hail Events Over the Beijing Metropolitan Region During the Warm Seasons of 2011–2021
Mingxin LI#+
Chinese Academy of Meteorological Sciences, China
The fine spatial characteristics of hail events over Beijing metropolitan region (BMR) is performed using direct observation from quality-controlled disaster information dataset during the year of 2011-2021. Hail is concentrated in urban and northeast mountain region which is highly related with both synoptic circulations and the underlying surface. Four synoptic circulation patterns: the northwest flow in front of ridge (NWP), straight westerly flow (SWP), cold vortex (CV), and pre-trough (PT) are investigated and the hail generation is found differs under these patterns. SWP favors local hail events with the largest convective available potential energy and PT favors systematic hail events with the highest vertical wind shear. With weak low level background flows under NWP and CV, hail events concentrate over the BMR’s plains with obvious surface warm center and wind convergence near urban region which favor storm initiation and enhancement. When the low-level background flow is larger in SWP and PT, the more dominated mountain-plain circulations lead to the hail events center changing to the BMR’s northeast mountains rather than the urban region. These results suggest the potential influences of urban environment and mountain-plain circulations on the distribution of hail events under different synoptic circulation patterns.
AS07-A005
Objective Climate Predictions of Summer Temperatures in South Korea Based on CNN and GNN
Jinyoung RHEE#+, Uran CHUNG, Kyoungwon PARK, Soo-Jin SOHN
APEC Climate Center, Korea, South
We explored the use of modern deep learning models of Convolutional Neural Networks (CNN) and Graph Neural Networks (GNN) for objective climate predictions of summertime air temperatures in South Korea. In order to design deep learning models more appropriate for climate predictions, the CUTMIX data augmentation technique was modified and applied to climate observations and APCC Multi-Model Ensemble (MME) data. The 3-dimensional CNN model performed much better with data augmentation for validation (accuracy > 0.6 for all summer months and folds) as well as test data for June (LT1) and July (LT2). Class activation maps were examined and the contributions of the data augmentation could be observed in some cases of the test data, e.g., in July 2018 and July 2021, when the northern Pacific are and northern polar region are activated and improved the predictions respectively. Graph Convolution Network models were developed for node classification (years as nodes) and graph classification (geographical grids as nodes and years as multiple graphs). Predictions for July (LT2) of the node classification model were improved with the month-agnostic approach, where all months of data are used for training. Predictions for June (LT1) of the graph classification model were improved with the month-agnostic approach (Heidke Skill Score > 0.35 for all folds) and predictions for July (LT2) were also improved with the aforementioned data augmentation. ※ This research was supported by APEC Climate Center.
AS07-A010
A Wind-dependent Parameterization for Ocean Sea Surface Albedo in FIO-ESM V2.0 Simulations
Xueyi JING1#+, Lanning WANG2, Zhenya SONG3
1College of Global Change and Earth System Science, Beijing Normal University, China, 2Beijing Normal University, China, 3Ministry of Natural Resources, China
Ocean surface albedo (OSA) is essential to the ocean and climate energy balance. It is usually considered as the constant or just a simple function of the solar zenith angle (SZA) in the climate model. However recent research suggests that the OSA can be significantly affected by low-level wind, and play an important role in climate simulation, especially in high-resolution simulation. In this work, we incorporated an improved OSA parameterization scheme into the First Institute of Oceanography-Earth System Model (FIO-ESM) V2.0. The revised parameterization scheme takes into account the sea surface roughness and whitecaps induced by surface wind and simplified water volume scattering. Numerical experiments indicate that the improved scheme leads to an increase in OSA of roughly 40% at the global scale. It is remarkable that the effects of foams or whitecaps are noticeable in areas with strong winds, such as the Southern Hemisphere westerly zone. The model bias in sea surface net shortwave radiation has been reduced by an average of 3 W/m2, and over the subtropical and Antarctic oceans by up to 8 W/m2 and 14 W/m2. The enhanced OSA parameterization also reduces the global annual mean error of sea surface temperature by up to 0.87°C.
AS07-A012
Optimization of Air Mass Factor Calculation for GOSAT-GW Satellite NO2 Observation
Ayano NAKAMURA1#+, Tomohiro SATO1, Tamaki FUJINAWA2, Yasuko KASAI3
1National Institute of Information and Communications Technology, Japan, 2National Institute for Environmental Studies, Japan, 3Tokyo Institute of Technology, Japan
The Global Observing Satellite for Greenhouse gases and Water cycle(GOSAT-GW) satellite is planned to be launched in 2024 as the successor to the GOSAT-1 and GOSAT-2 greenhouse gas observation missions. The GOSAT-GW satellite challenges to simultaneously observe greenhouse gases and nitrogen dioxides (NO2), major air pollutants. The grating spectrometer is equipped, and more than three million points are observed per day.
The air mass factor (AMF) is used to convert from the NO2 slant column density to the vertical column density, and is one of the largest error sources in retrieving NO2 vertical column from the observation spectrum. High speed calculation of AMF is required because of large number of observation points of GOSAT-GW. The AMF values for all observation cases are pre-calculated by radiative transfer model and saved in the look-up table (LUT).
This study discusses the optimization of LUT, i.e, how to select the nodes of input variables in LUT. We used SCIATRAN version 4.6.1 for radiative transfer calculation. The node of each input variable, such as solar zenith angle, viewing zenith angle, albedo, and terrain height, are selected by AMF gradients for the variables. Our algorithm showed 45% lower error than conventionally-made LUT. In this presentation, we show the results of all LUTs used in the NO2 retrieval data processing of the GOSAT-GW.
AS07-A013
Predicting Ambient NH3 Concentrations Based on the Extra Trees with Time Lag and Parcel Tracking Functions
Chin Yu HSU#+
Ming Chi University of Technology, Taiwan
Ambient NH3 plays an important role in forming particulate matter (PMs), and therefore, it is crucial to comprehend NH3's properties in order to reduce PMs. However, it is not easy to achieve this goal due to the lack of monitoring data on ambient NH3 concentrations in typical air quality stations. Nor are we aware of any study that has looked into NH3 predictions as of yet. This study thus offers the first inquiry into applying machine learning and an auto hyperparameter optimization approach to estimate NH3 concentrations. To obtain more crucial data about NH3 concentration, we additionally created time lag and parcel tracking routines. To analyze feature importance, we applied the SHAP (SHapley Additive exPlanations) function. From 2016 to 2018, Taichung's hourly average NH3 values were about 16.9 ppb. Such NH3 concentrations were predicted using an optimized extra trees model that has the potential to account for up to 96% of the total variance. Agriculture activity was the most significant factor (main source) to affect NH3 concentrations in Taichung among all the characteristics.
AS07-A016
Role of the Spring Southeastern Indian Ocean Warming in Bridging the Indian Ocean Dipole and Subsequent ENSO
Yue ZHONG+, Wenshi LIN, Tuantuan ZHANG#, Shuyan WU
Sun Yat-sen University, China
A significant relationship between the Indian Ocean Dipole (IOD) and the following year’ s El Niño-Southern Oscillation (ENSO) has been reported in recent decades. Nevertheless, uncertainty exists regarding the associated mechanisms. Based on the statistical analysis and numerical experiments, our study proposes that the spring southeastern Indian Ocean warming (SEIOW) plays a bridging role in the teleconnections of the IOD and subsequent ENSO. A positive IOD could induce a positive tendency of sea surface temperature (SST) in the southeastern Indian Ocean from autumn to winter, primarily through the cloud-radiation-SST feedback, forming an anomalous SEIOW in the subsequent spring. As a Gill-model response to this SEIOW, an anomalous anticyclone appears over the western North Pacific, accompanied by easterly wind anomalies in the western equatorial Pacific which generate eastward propagating upwelling Kelvin waves. As a result, anomalous cooling appears over central-eastern tropical Pacific in the following seasons, manifesting as a La Niña mode. The process is vice versa for the teleconnections of the negative IOD and following year’s El Niño. Additionally, role of the ocean channel (i.e., the Indonesian Throughflow) in connecting the spring southeastern Indian Ocean and the subsequent winter eastern Pacific SSTs is also discussed.
AS07-A020
Major Factors Governing the Trends and Interannual Variability in the Occurrences of Mixed Rossby-Gravity Wave Events
Mehak N.A.#+, Shreya KESHRI, Suhas ETTAMMAL
Indian Institute of Science Education and Research Pune, India
Mixed Rossby-Gravity (MRG) waves are westward propagating synoptic scale equatorial disturbances, which play a crucial role in the formation of tropical cyclones and tropical depressions. They constitute a significant part of various modes of tropical variability, like Madden-Julian Oscillation (MJO) and Quasi-Biennial Oscillation. This study investigates the trends and Inter Annual Variability (IAV) in the occurrence of upper tropospheric MRG events using ERA-I reanalysis data for the period 1979-2018. The MRG events are identified by projecting the 200hpa meridional winds onto the theoretical spatial structure of MRG waves. A steady increasing trend is observed in the MRG events, which is contributed by the MRG events associated with intrusion of extratropical disturbances. Possible factors governing the observed trend and IAV in MRG events are El-Nino Southern Oscillation (ENSO), MJO and extratropical forcing. The MRG events over the central and eastern Pacific contribute maximum to IAV. ENSO explains about 25% of IAV and exhibits a positive correlation with non-intrusion MRG events and a negative correlation with intrusion MRG events. These observations have been investigated by exploring the properties of the westerly duct at 200hPa and Outgoing Longwave Radiation during El-Nino and La-Nina years over the central-eastern Pacific. The convectively active state of MJO over the western Pacific explains 20% of IAV. The antisymmetric heating with respect to the equator, associated with MJO, enhances non-intrusion MRG events by forbidding the intrusion of extratropical disturbances through subtropical easterlies. The increasing trend in the intrusion of extratropical disturbances explains the observed trend in MRG events.
AS07-A025
Diagnosis of Data Assimilation Effect on East Asian Forecast of the Global NWP Model Through OSSE
Hyerim KIM+, Kyung-Hee SEOL#, In-Hyuk KWON, Hui-Nae KWON, Hyun-Jun HAN
Korea Institute of Atmospheric Prediction Systems, Korea, South
The global atmosphere NWP system – named the Korean Integrated Model (KIM) – developed by the Korea Institute of Atmospheric Prediction Systems (KIAPS) was made operational at the Korea Meteorological Administration (KMA) in April 2020. The global data assimilation (DA) system is based on a hybrid-4DEnVar system consisting of KVAR (KIM VARiational data assimilation) and LETKF (Local Ensemble Transform Kalman Filter). Although it provides a good forecast skill within the performance range of the world’s leading NWP centers, the prediction has some systematic bias over East Asia. Forecast skill of the forecast system including DA system is sensitive to initial data and assimilated observation data. Thus, improving the model itself is important, but the performance of observation data used for DA is also important in order to improve forecast skill. An Observing System Simulation Experiment (OSSE) has been conducted to understand the model prediction sensitivity according to DA. If we consider a global gridded virtual Sonde observation network and assume that the ERA5 analysis is true of the OSSE system, simulated observations with globally 1-degree intervals can be generated from ERA5. In this study, the difference between forecasts fields assimilated with the existing observation data and the virtual Sonde data is examined for cases chosen when KIM’s East Asia forecast skills are significantly low. Through these experiments and analysis, we would like to examine the following two. First, this system will be used to investigate the effect of the initial condition and the virtual Sonde data as the observation data on the 5-day prediction accuracy of the East Asia. Second, we plan to conduct sensitivity experiments for diagnosing regions where affect the improvement of East Asia’s forecast performance to improve 5-day forecast skill.
AS07-A027
Development of Global Observing System Simulation Experiment (OSSE) System Using Korean Integrated Model (KIM) : Description and Preliminary Result
Hyun-Jun HAN#+, Jeon-Ho KANG, In-Hyuk KWON
Korea Institute of Atmospheric Prediction Systems, Korea, South
Observing system simulation experiment (OSSE) provide a rigorous, cost-effective approach to evaluating the potential impact of new observing systems and alternate deployments of existing systems and to optimizing observing strategies (Hoffman and Atlas, 2016). One of most advantageous thing in OSSE is that researcher can verify the result of Numerical Weather Prediction (NWP) with respect to the truth (called as nature run (NR)). Furthermore, observation can be simulated for any proposed (for example, making new type of sensor, appling realistic forward operator and method, specifying the locations, and error characteristics of the observation). To use such advantage of OSSE, we developed the prototype of global OSSE system used Korea Integrated Model (KIM).
In this study, we will introduce the theoretical background of OSSE (OSSE is generally consist of the NR, simulated observation, DA and forecast, and calibration and verification), KIM forecast system, and what i done to develop the OSSE system used KIM, briefly. Finally, to verify the OSSE system used KIM, we performed the denial experiments for aircraft, not only in OSSE but also performed in OSE. In comparison result between OSE and OSSE aircraft denial experiments, OSE/OSSE showed similar performance in most atmospheric variables of analysis field. So, we evaluated the OSSE system used KIM is well made enough to simulate the real case.
AS07-A034
Estimation of Planetary Boundary Layer Height Based on Radiosonde Data
Junsik KIM+, Junshik UM#
Pusan National University, Korea, South
The planetary boundary layer (PBL) is the lowest part of the atmosphere and interacts directly with the Earth's surface, playing an important role in weather, climate, and air quality. It also plays an important role in the exchange of aerosols, heat, humidity, and other atmospheric gases. Therefore, it is vital to understand the spatial and temporal variations of the PBL height (PBLH). Radiosonde launching has been used to determine the vertical profile of the PBL. The Korea Meteorological Administration(KMA) has been launching radiosondes twice a day (00 and 12 UTC or 9 and 21 LST) at ten different stations in Korea. In this study, the PBLH was calculated using the bulk-Richardson method with the KMA radiosonde data. The bulk Richardson method calculated the PBLH using the ratio of thermally generated turbulence generated by the vertical shear. The used variables were virtual potential temperature, wind speed, gravity, altitude, and humidity. When the bulk Richardson method reached the threshold, two types of thresholds, 0.25 and 0.5, were commonly used. In this study, 0.25 was used as the threshold. The altitude when the threshold of the bulk Richardson method calculated from the ground exceeded 0.25 was determined as the PBLH. The calculated PBLH was also compared with those determined based on the ceilometer measurements.
AS07-A035
A 4DIAU Scheme for the KIM Data Assimilation System
Wonho KIM#+, Adam CLAYTON, In-Hyuk KWON
Korea Institute of Atmospheric Prediction Systems, Korea, South
Currently, the operational Korean Integrated Model (KIM) Numerical Weather Prediction system at the Korea Meteorological Administration (KMA) uses 3DIAU to add deterministic analysis increments to the model. The weights are based on a Dolph filter, but with the first and last weights modified to remove discontinuities, producing a “modified Dolph filter”. Hybrid-4DEnVar scheme used for deterministic analyses produces a total of 7 analysis increments – one every hour within data assimilation window. Thus, it is possible to replace the 3DIAU scheme with a 4DIAU scheme that makes use of the hourly analysis increments. We have experimented with a 4DIAU scheme that adds each analysis increment over a 2-hour period, again using modified Dolph weights. For increments that are, the response is determined by the weighting function used for the individual increments, giving relatively light time-filtering. For increments that are not, such as the stationary increments related to the static covariance, the response is determined by the sum of the weights across all increments, giving relatively heavy time-filtering similar to that obtained with the 3DIAU scheme. Thus, for balanced increments that are consistent in time, such as increments associated with rapidly-moving features like tropical cyclones, 4DIAU should be better than 3DIAU at retaining the increments. We compared analysis and forecast performance of the new 4DIAU scheme with the original 3DIAU scheme. In analyses, there was relatively little impact on T and Q, but U and V were improved. In the Northern Hemisphere, overall forecast performance was improved, and the performance improvement of geopotential height was significant. The performance improvement in the Northern Hemisphere is particularly noticeable in Asia. In a tropical cyclone case experiment, the 4DIAU scheme gave a slightly deeper central pressure than the 3DIAU scheme, and expressed the change in tropical cyclone position over time better than 3DIAU.
AS07-A036
Introduction of Research Performance During 2017-2021 in NIMS/KMA
Youngmi KIM#+, Jinyoung KO, Heon Woo KIM, Ha-Kwom LIM
National Institute of Meteorological Research/Korea Meterological Research, Korea, South
NIMS works for meteorological science research and policy support for people’s safety and happiness and has been doing lots of research under the research project, called the “Research and Development for KMA Weather, Climate, and Earth System Services”.
NIMS has developed technologies needed to improve forecasting for KMA such as a medium-term forecast guideline and marine weather forecasting system. Initialization and ensembles of climate prediction system were improved for more accurate and reliable climate predictions. Due to climate change, damages caused by heavy rains in summer have increased and rainfall forecasting has become difficult. So, NIMS has developed diagnostic factors for heavy rainfall through synoptic analysis of severe weather.
There was challenged study using advanced observation equipment meteorological observation vehicles, meteorological aircraft, and meteorological drones. For understanding and analyzing of a meteorological phenomenon, NIMS observed heavy rainfall, black ice, and so on. These data are used to understand the mechanisms of severe weather. Black ice prediction based on these data has been developed to decrease winter traffic accidents. The technologies of weather modification are constantly evolving using advanced equipment. Also, Korea Cloud Physics Experimental Chamber (K-CPEC) was conducted in 2021. We expect to develop better technology and understand cloud physics.
To support national climate change response policy, NIMS produced new future projections based on New Green House Gases (GHG) and published climate change reports. Also, NIMS continuously monitors GHG. For expanding renewable energy, NIMS provides high-resolution meteorological resource maps.
In addition, NIMS has been producing convergence weather information such as airport weather prediction, health weather, and agricultural weather. More detailed results will be shown at the conference.
AS07-A037
Hydrothermal Factors Influence on Spatial-temporal Variation of Evapotranspiration-precipitation Coupling Over Climate Transition Zone of North China
Ze Su YANG#+
Chengdu University of Information Technology, China
As a land-atmosphere coupling “hot spot”, the northern China climate transition zone has a sharp spatial gradient of hydrothermal conditions, which plays an essential role in shaping the spatial and temporal pattern of evapotranspiration-precipitation coupling, but whose mechanisms still remain unclear. This study analyzes the spatial and temporal variation of land-atmosphere coupling strength (CS) in the climate transitional zone of northern China and its relationship with soil moisture and air temperature. Results show that CS gradually transitions from strong positive in the northwest to negative in the southeast and northeast corners. The spatial distribution of CS is closely related to climatic hydrothermal conditions, where soil moisture plays a more dominant role: CS increases first, and then decreases with increasing soil moisture, with the threshold of soil moisture at 0.2; CS gradually transitions from positive to negative at soil moisture between 0.25 and 0.35; CS shows an exponential decreasing trend with increasing temperature. In terms of temporal variation, CS is strongest in spring and weakens sequentially in summer, autumn, and winter, and has significant interdecadal fluctuations. The trend of CS shifts gradually from significantly negative in the west to a non-significant positive in the east. Soil moisture variability dominates the intra-annual variability of CS in the study regions, and determines the interannual variation of CS in arid and semi-arid areas. Moreover, the main reason for the positive and negative spatial differences in CS in the study area is the different driving regime of evapotranspiration (ET). ET is energy-limited in the southern part of the study area, leading to a positive correlation between ET and lifting condensation level (LCL), while in most of the northern part, ET is water-limited and is negatively correlated with LCL.
AS07-A039
Evaluation of High-resolution Crop Model Meteorological Forcing Datasets at Regional Scale: Air Temperature and Precipitation Over Major Land Areas of China
Qiuling WANG1+, Wei LI2#, Chan XIAO2, Wanxiu AI2
1National Climate Center, China Meteorological Administration, China, 2China Meteorological Administration, China
Air temperature and precipitation are two important meteorological factors affecting the earth’s energy exchange and hydrological process. High quality temperature and precipitation forcing datasets are of great significance to agro-meteorology and disaster monitoring. In this study, the accuracy of air temperature and precipitation of the fifth generation of atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ERA5) and High-Resolution China Meteorological Administration Land Data Assimilation System (HRCLDAS) datasets are compared and evaluated from multiple spatial–temporal perspectives based on the ground meteorological station observations over major land areas of China in 2018. Concurrently, the applicability to the monitoring of high temperatures and rainstorms is also distinguished. The results show that (1) although both forcing datasets can capture the broad features of spatial distribution and seasonal variation in air temperature and precipitation, HRCLDAS shows more detailed features, especially in areas with complex underlying surfaces; (2) compared with the ground observations, it can be found that the air temperature and precipitation of HRCLDAS perform better than ERA5. The root-mean-square error (RMSE) of mean air temperature are 1.3 ◦C for HRCLDAS and 2.3 ◦C for ERA5, and the RMSE of precipitation are 2.4 mm for HRCLDAS and 5.4 mm for ERA5; (3) in the monitoring of important weather processes, the two forcing datasets can well reproduce the high temperature, rainstorm and heavy rainstorm events from June to August in 2018. HRCLDAS is more accurate in the area and magnitude of high temperature and rainstorm due to its high spatial and temporal resolution. The evaluation results can help researchers to understand the superiority and drawbacks of these two forcing datasets and select datasets reasonably in the study of climate change, agro-meteorological modeling, extreme weather research, hydrological processes and sustainable development.
AS07-A040
The Effect on the Wind of Coastal Urban Buildings Using LES Model
Jiseon KIM1#+, Soon-Hwan LEE1, Soon-Young PARK2, JungWoo YOO1
1Pusan National University, Korea, South, 2Daegu National University of Education, Korea, South
Due to concentrated buildings, low vegetation, and road paving materials, cities are likely vulnerable to weather environments such as heat waves and floods. In addition, in complex urban structures, it is difficult to predict wind changes caused by high-rise buildings, making it challenging to analyze the thermal environment and pedestrians' thermal comfort in the city.
This study attempts to simulate and analyze wind changes in complex urban environments using a PALM(Parallelized Large-Eddy Simulation Model). Haeundae Marine City in Busan, Korea, located on the coast, was selected as the study target area. This area is where concentrated high-rise residential and commercial buildings are and where light reflection by the outer walls of the building glass and damage by strong winds occur.
Simulate the actual urban structure of Marine City with a large-eddy simulation (LES)-based PALM model to identify changes in surrounding winds due to the height difference of the high-rise buildings inside the city and compare environmental changes such as pedestrian thermal comfort.
AS07-A042
Predictability of the Western Pacific Pattern in the APCC Multi-model Ensemble
Joong-Bae AHN1#+, Eung-Sup KIM2, Vladimir KRYJOV3
1Pusan National University, Korea, South, 2National Institute of Agricultural Sciences, Korea, South, 3Hydrometcenter of Russia, Russian Federation
In this study, the predictability of the Western Pacific (WP) pattern is evaluated using five seasonal prediction models the Asia-Pacific Economic Cooperation (APEC) Climate Center (APCC) multi-model ensemble (MME) for the winters from 1982/1983 to 2021/2022. The temporal correlation coefficient (TCC) between the observed and MME-predicted WP indices was 0.61 (0.37–0.54 for individual models) for the entire series. However, when only three Super El Niño (SEN) years (Niño3.4 ≥ 2.0) out of the 40-year series were excluded, the TCC dropped down to 0.54 (0.27–0.42). During the SEN years, the WP was strongly affected by the SEN-excited anomalies via the PNA. In observations from non-SEN years, the WP pattern was strongly related to the dipole pattern in Northwestern Pacific SST (TCC = 0.8), for the description of which we suggested a Northwestern Pacific (NWP) index, and it was significantly weakly related to the ENSO and IOD, whereas in the model simulations, the main role was played by the ENSO (TCC = 0.6). The NWP index was well predictable in MME (TCC = 0.73) and individual models (0.56–0.71). We showed that the prediction of the WP index polarity is reliable when both predicted WP and NWP anomalies are significant and indicate the same WP sign that has implications for the seasonal forecasting. Acknowledgment: This work was carried out with the support of the Research Fund of Research Institute for Basic Sciences, Pusan National University, Korea.
AS07-A045
A Survey of Mixed Rossby-gravity Waves and Quantification of Their Association with Extratropical Disturbances
Shreya KESHRI#+, Suhas ETTAMMAL
Indian Institute of Science Education and Research Pune, India
In this study we have conducted a survey of Mixed Rossby-Gravity (MRG) wave events in the upper troposphere and quantified their association with the intrusions of extratropical disturbances for the period 1979-2019. MRG events are identified by projecting the equatorial meridional winds at 200 hPa onto the meridional structure of theoretical MRG waves. 2390 MRG events are identified and majority (61%) of them occurred during May-October months, and 65% of the total MRG events occurred over the central-east Pacific and Atlantic Ocean domains. Not only the frequency of occurrence but also the amplitude, wavenumber and trapping scale of the MRG events are found to exhibit a clear seasonality. MRG events associated with intrusions of extratropical disturbances are identified as when the potential vorticity on the 350K isentropic surface at 15° latitude exceeded 1 PVU in the vicinity of the MRG events. We find that 37% of the MRG events are intrusion MRG events and a large majority (88%) of such events occurred over the central-east Pacific and Atlantic Ocean domains. It is also noteworthy that nearly 70% of such intrusions occurred in the winter Hemisphere where the westerly wind ducts are well developed. Over the central-east Pacific during Northern Hemispheric (NH) winter, it is observed that the amplitude of intrusion MRG events are larger and have a larger meridional extent compared to non-intrusion MRG events. They also exhibit a similar spatial scale as the extratropical disturbances implying that resonant interactions may be a primary mechanism for the genesis of MRG events. During NH summer, on the other hand, MRG events are primarily triggered by convective processes and the extratropical disturbances may be instrumental in amplifying their amplitude.
AS07-A053
Impact of Changes in Ice Microphysical Processes on Predictability of the Korean Integrated Model
Jeong-Ock LIM#+, Jeong-Hyun PARK, Hyun-Joo CHOI, Seonghoon CHEONG
Numerical Modeling Center/Korea Meteorological Administration, Korea, South
Korean Integrated Model (KIM), developed by Korea Institute of Atmospheric Prediction System (KIAPS), has been in operation at Korea Meteorological Administration (KMA) since April 2020. It has been continuously improved its performance through five updates (v3.5a (2020.06), v3.6a (2021.4), and v3.7 (2021.12), v3.8 (2023.2)) including data assimilation and physics.
One of the major systematic errors of the KIM is the cold biases in the lower Arctic atmosphere in summer, which degrades KIM’s prediction performance in the northern hemisphere. The radiative cooling effect by clouds, especially, over-estimated cloud ice, is analyzed as one of the main factors.
In this study, we will examine the possibility of improving the above-mentioned systematic errors through sensitivity test to changes in parameters related to ice crystals of WSM5, cloud microphysics scheme adopted by KIM.
AS08-A005
Size Distribution of Atmospheric Aerosols Considerably Impacts Radiative Effects Over the Himalayas by Modulating Aerosol Single-scattering Albedo
Zeren YU#+, Pengfei TIAN, Lei ZHANG, Jiening LIANG
Lanzhou University, China
The single-scattering albedo (SSA) of atmospheric aerosols is a key parameter that controls aerosol radiative effects. The variation of SSA is thought to be mainly regulated by aerosol absorption in the Himalayas and South Asia, but observations contradict this idea. In situ field campaigns conducted over two Himalayan sites revealed that SSA was strongly dependent on scattering but weakly correlated with absorption. Observational results combined with the Mie theory further illustrated that SSA was primarily modulated by size distribution rather than absorption. Aerosol Robotic Network (AERONET) data showed similar impacts of size distribution on SSA and that aerosol radiative forcing efficiencies were significantly dependent on SSA. Aerosol size distribution therefore considerably affects radiative forcing by modulating aerosol SSA over the Himalayas. This study highlighted the influence of aerosol size distribution on radiative forcing over the Himalayas, which has important implications for understanding aerosol radiative effects globally.
AS08-A006
Polarized Adding Method of Discrete Ordinate Approximation for Visible and Near-infrared Radiative Transfer
Kun WU1#+, Feng ZHANG2, Wenwen LI2
1Nanjing University of Information Science & Technology, China, 2Fudan University, China
Polarization characteristics of the atmospheric scattering is important and not to be ignored in radiative transfer simulation. A new polarized radiative transfer method is developed for visible and near-infrared spectra, which is suited for use in remote sensing applications and can calculate the polarized radiation emerging from an atmosphere. The single-layer polarized radiative transfer equation and inhomogeneous multi-layer connection are solved by the discrete ordinates method and adding method, respectively. Monte Carlo model (MYSTIC, as the benchmark) and PolRadtran/RT3 are used to evaluate the new method in both accuracy and computational efficiency under different atmospheric conditions and view angles. Judging from the results, the accuracy of Stokes vector (I-, Q-, U-, V-component) calculated by the new method is a good agreement with the results by PolRadtran/RT3 except where near solar incident zenith angle and anti-incident zenith angle. The relative root mean square errors (RMSE) of Stokes vector for test cases between MYSTIC and the new method or RT3 can also prove the good accuracy of new method. Meanwhile, the new method has a higher computational efficiency compared to RT3, especially for the atmosphere with large scattering optical depth. As differ from RT3, the computing time of the new method cannot increase with increasing optical depth.
AS08-A007
A Study on Changes in Particle Characteristics Depending on Relative Humidity Using LiDAR Data
Sohee JOO1+, Youngmin NOH1#, Dukhyeon KIM2, Juseon SHIN1, Naghmeh DEHKHODA1, Juhyeon SIM1, Jaewon KIM1, Yuseon LEE1, Gahyeon PARK1, Jihyeon YUN1
1Pukyong National University, Korea, South, 2Hanbat National University, Korea, South
In this study, the Extinction coefficient(α) was calculated using lidar data installed at Seoul National University and divided by the mass concentration of fine particles to confirm the Mass Extinction Efficiency(MEE). This study used lidar data from January 2015 to June 2020 for analysis and compared the mass concentration of fine particle at the AirKorea Gwanak-gu station and relative humidity data(RH) at the Metropolitan Meteorological Administration. RH was divided into 7 sections, and we checked the change in the particle's characteristics. As a result, as the RH increased, MEE tended to increase, and it was confirmed that the PM2.5/PM10 ratio also increased. However, the α ratio observed by lidar appears different from the mass concentration. The α Fine/Total ratio rather decreased as the RH increased. Conversely, the α Coarse/Total Ratio showed an increase. We thought to be caused by differences between observation equipment. Airkorea's station method is a Beta-radiation attenuation monitor method that uses a heater to remove some moisture to lower the RH. However, in the case of LiDAR, the effect of RH is not removed by directly observing particles distributed in the atmosphere. Particles corresponding to PM2.5 in a dry atmosphere can increase to a particle size larger than PM2.5 as the RH increases, so they can be classified as coarse particles in LiDAR. However, in mass concentration measurement, the effect of humidity is partially removed, and It is classified as PM2.5. This work was supported by a grant from the National Institute of Environment Research (NIER), funded by the Ministry of Environment (MOE) of the Republic of Korea (NIER-2023-01-02-084).
AS08-A012
Real-time LiDAR Ratio Calculation Using Nighttime Camera and Laser
Juhyeon SIM1+, Dukhyeon KIM2, Juseon SHIN1, Sohee JOO1, Jaewon KIM1, Yuseon LEE1, Gahyeon PARK1, Jihyeon YUN1, Youngmin NOH1#
1Pukyong National University, Korea, South, 2Hanbat National University, Korea, South
When atmospheric information is analyzed through LiDAR, backscattering coefficients and extinction coefficients are calculated through LiDAR signals. The LiDAR ratio represents the ratio of the extinction coefficient and the backscattering coefficient. The LiDAR ratio is a variable that varies depending on the size distribution of particles in the air, the refractive index of particles, etc. Still, in most studies, it is fixed as a constant, and the extinction coefficient is calculated from the backscattering coefficient, or the backscattering coefficient is calculated from the extinction coefficient. In this study, LiDAR using a 532 nm wavelength laser and a camera attached to the lidar were utilized. The relationship between the extinction coefficient and the backscattered signal was examined by calculating the backscattered signal proportional to the backscattered coefficient with the pixel value of the laser taken in the picture while obtaining the extinction coefficient by LiDAR. Using these two variables, it was confirmed that the optimized lidar ratio could be calculated according to each atmospheric condition. In addition, in the case of LIDAR, because of the field of view (FOV), a short-range signal of about 0.5 km cannot be calculated. However, since the camera can also obtain pixel values at a short distance, the near-field extinction coefficient can also be restored by using the previously obtained LiDAR ratio and the backscattered signal received from the photograph. Through this study, it was confirmed that if the pixel signal of the camera is used, it is possible to calculate the extinction coefficient more accurately by using the LiDAR ratio optimized for each atmospheric situation, and the overlapping LiDAR short-range signal can be restored.This work was supported by a grant from the National Institute of Environment Research (NIER), funded by the Ministry of Environment (MOE) of the Republic of Korea ( NIER-2023-01-02-084).
AS08-A013
Geometric Factor Correction in the Horizontal Scanning LIDAR System
Juseon SHIN1#, Gahyeon PARK1+, Dukhyeon KIM2, Youngmin NOH1
1Pukyong National University, Korea, South, 2Hanbat National University, Korea, South
We tried to use scanning Light Detection and Range (LIDAR) to measure PM mass concentration as a three-dimension. The scanning Lidar system can detect PM mass concentration in an area with a radius of 5 km using 1064 nm and 532 nm wavelengths. Furthermore, the time resolution of the scanning LIDAR is as short as 10 sec, so it can apply to the timely monitoring of specific aerosol emissions. In the experiment for emissions of aerosols, we faced some problems; the laser was blocked at 2500 m by mountain, and the overlap distance of the 1064 nm laser was longer than that of the 532 nm laser. For the former problem, we neglected the signal from blocking and found the reference extinction coefficient through measured signals over 10 min to increase SNR. In the case of the overlap problem, the range-corrected signal contributed to increasing the slope, which made the reference signal overestimated. Therefore, we need to correct the LIDAR signal by the geometric factor in blind-zone, in which the backscattered signal cannot reach the field of view on telescope. For those reasons, 1) we have theoretically calculated geometric factor from experimental system parameters, such as laser beam divergence, FOV, distance between laser and telescope, and others. 2) We also experimentally considered the relationship signals between 1064 nm and 532 nm lasers to find the signal loss with the assumption of constant Angstrom Exponent. 3) We have corrected geometric factors iteratively from theory to experiment. This work was supported by a grant from the National Institute of Environment Research (NIER), funded by the Ministry of Environment (MOE) of the Republic of Korea ( NIER-2023-01-02-084).
AS08-A014
Determined Spatial and Temporal Variability of Mixing Layer Height Using Aerosol Backscatter Data of Ceilometer
Hyunkyoung KIM1+, Heejung JUNG1, ChangHoon JUNG2, Junshik UM1#
1Pusan National University, Korea, South, 2Kyungin Women's University, Korea, South
A mixing layer height (MLH) is an important factor that controls air pollution concentrations. Thus, it is necessary to determine MLH accurately and to understand its spatial and temporal variability. One of the common methods for determining MLH is to calculate MLH using the vertical profiles of aerosol backscatter measured by a ceilometer. Originally, a ceilometer has been developed to detect the cloud base height. However, its measurement has also been used to determine the MLH, and several ceilometer measurement networks have been emerged across the world. The Korea Meteorological Administration (KMA) has installed ceilometers to observe cloud amount and cloud base height, and two different types of ceilometers, Vaisala CL31 and Eliasson CBME80B have been operating at 64 stations in Korea. Since 23 December 2022, the National Institute of Environmental Research (NIER) in Korea also has deployed nine Lufft CHM 15k ceilometers to determine the MLH and they are in operation now.
In this study, the MLH was determined based on a gradient method using the aerosol backscatter data measured by KMA and NIER ceilometers, and the spatial and temporal variability of MLH were quantified. The spatial and temporal variability of MLH was further examined as a function of the distance between ceilometers. All correlation analyses were also separated for daytime (06:00 LST to 18:00 LST) and night-time (18:00 LST to 06:00 LST), which had also compared each other. Based on these analyses, the impacts of temporal and spatial variability of MLH on the determined MLH were examined.
AS08-A016
Prediction Algorithms for the Rapid Changes of Visibility According to the Radiation Fog Events
Jaewon KIM1+, Dukhyeon KIM2#, Youngmin NOH1, Juseon SHIN1, Sohee JOO1, Juhyeon SIM1, Yuseon LEE1
1Pukyong National University, Korea, South, 2Hanbat National University, Korea, South
Fog is defined as a case where the visibility distance is less than 1 km by atmospheric water droplet, and it is known that fog is difficult to predict because it is caused by various causes depending on the seasons and locations. However, the extinction coefficient of water droplet at a given wavelength of 550 nm is exactly determined by the product of the volume concentration of a water droplet with a given refractive index of 1.33 and the volume extinction efficiency defined at the given size and wavelength. So the rapid change of visibility can be simply explained only by the rapid changes of the volume extinction efficiency by particle size or the rapid changes of water droplet concentration. The volume extinction efficiency sequentially reaches the maximum value following the wavelength for the constantly increasing particle size. In this study, we developed the algorithms on how to predict the occurrence of radiation fog by measuring the growth rate of particles using the relative change in extinction coefficient that occurs sequentially at the three wavelengths of RGB (449nm, 534nm, 597nm). Based on the particle growth theory, when particles grow in various ways, how the extinction coefficient changes at three wavelengths was studied, and how the relative value of the extinction coefficient at each wavelength changes with the growth of the particle size. Based on these theoretical results, we checked the changes of the extinction coefficient obtained from the 3 wavelengths at the radiation fog events and predicted the fog disappearing in the Daecheong area around Daecheong Lake where actual radiation fog often occurs. This work was supported by the “Graduate school of Particulate matter specialization.” of Korea Environment Industry & Technology Institute grant funded by the Ministry of Environment, Republic of Korea.
AS10-A003
Impact of Tropical Intraseasonal Oscillation on the 2015 Indian Heatwave
Tukaram ZORE#+, Kiranmayi LANDU
Indian Institute of Technology Bhubaneswar, India
It is well known that tropical intraseasonal oscillation (ISO) modulates the weather in the tropics. The ISO’s importance in cyclogenesis, extreme precipitation events, and heatwave events is established in the literature. Hence understanding and simulating these oscillations can tremendously improve the extended-range predictions of weather extremes. With changing climate, the frequency and intensity of heatwaves are known to be increasing and becoming one of the primary weather catastrophes. In May 2015 southeastern states of India faced the deadliest heatwave in its history which claims to take 2500 lives. The atmospheric circulation and role of surface fluxes in forming this heatwave were studied in the recent past but the underlying physical mechanism is not known. In this study, we investigated the impact of the tropical intraseasonal oscillation (ISO) in forming the May 2015 heatwave over the southeastern regions of India. The observations show that the occurrence of a heatwave is attributed to north-eastward propagating ISO circulation which results in persistent high-pressure anomaly with anomalous downward motion favoring clear skies, adiabatic heating, and horizontal warm advection. The 2m maximum temperature anomaly shows that 60% to 75% contribution in maximum surface air temperature (SAT) during heatwave period is from ISO-related temperature anomalies. Further numerical analysis using the WRF model confirms that this heatwave event was caused by Propagating ISO. The model output shows a difference of 1.5 to 2 ℃ in maximum SAT between the control and sensitive experiment. Indicating the substantial role of ISO in the development and intensification of the heatwave. This analysis emphasizes that improving the forecasting skills of ISO may facilitate the sub-seasonal forecast of local heatwave events.
AS10-A016
Comparison and Application of Gap-filling Algorithm for Extreme Climate Analysis of Vanuatu Observation Data
Imgook JUNG+, Kyungwon PARK, Jong Ahn CHUN#
APEC Climate Center, Korea, South
The weather observation data collected over a long period of time can be used as important data as the basis for showing the long-term climate characteristics and extreme weather of an area. Meanwhile, in the case of developing countries, it is difficult to collect high-quality weather observation data due to the lack of installation and management system of weather observation equipment. Through the Van-KIRAP (Vanuatu Klaemet Informesen blong Redy, Adapt mo Protekt, in Bislama) project, APCC (APEC Climate Center) wanted to provide observational data that could be useful in the Vanuatu region by adding the gap-filling of observational data to the OSCAR (tailored System of Climate services for AgRiculture) system. Through a comparative analysis conducted by applying various existing gap-filling algorithms to observation data, an algorithm technique suitable for precipitation and temperature, which are the target variables of this study, was selected. The performance of the gap-filling algorithm was compared using the standard statistical indicator CC (Correlation Coefficient) and RMSE (Root Mean Squared Error), and an algorithm that shows compliance performance was selected. It is expected to be used in various applied studies, including long-term climate analysis and extreme climate analysis, through correction observation data through the OSCAR system.
AS10-A017
Development of Long-term Climate Products Using Remote Sensing Data
Kyungwon PARK#+, Imgook JUNG, Jong Ahn CHUN
APEC Climate Center, Korea, South
Long-term climate data is one of the main data used for climate analysis, but in developing countries, the development of observation data is insufficient compared to developed countries. We tried to build observation data for long-term climate analysis using satellite remote sensing as the data needed for climate analysis. Precipitation datasets were constructed using GridSat and GPM-IMERGE, and the temperature was constructed based on AQUA, TERRA on installed MODIS sensor and AIRS satellite products. The results of the 10km spatial resolution of the satellite output were developed using the IGISRM technique to construct the entire Vanuatu area with high-resolution grid datasets of 5km. It is expected that climate analysis of high-resolution grid data produced in this project will be used as data for agriculture and various applications.
AS10-A019
The Latitudinal Position of the Westerly Jet Stream Modulated by the Tropics-Extratropics Boundary and Sea Surface Temperature Fronts
Mari MUTO#+, Tsubasa KOHYAMA
Ochanomizu University, Japan
Large-scale dynamics in the tropics and midlatitudes are governed by two different dominant physical processes. The tropics is governed by the weak temperature gradient system where temperature gradient is constrained to be moderate, whereas the midlatitude area is governed by the quasi-geostrophic system where the Coriolis force and pressure gradient force are nearly balanced. Presumably, for these two different governing equations to be simultaneously valid in large scales, the boundary between these two regions must be connected by phenomena with small spatial scales. Therefore, in this study, we investigate the atmospheric behavior at the tropics-extratropics boundary in the Northern Hemisphere.
The 5800 meter height line at 500 hPa is defined as the tropics-extratropics boundary. This line serves as a proxy for the northern edge of the tropical region. Next, we focus on the strong wind axis of the westerly jet stream, which moves meridionally at mid-latitudes, because the jet stream can supply vortices with small spatial scales. Then, we investigate the positional relationship between the jet stream and the tropical mid-latitude boundary.
By measuring the mean latitudinal distance between the jet stream and the boundary, it is shown that the jet stream flows near tropics-extratropics boundary in most seasons. However, only in seasons when a sea surface temperature (SST) front exists near the boundary, the westerly jet stream is anchored by the SST front and temporarily leaves tropics-extratropics boundary. In boreal spring and autumn, when the westerly jet stream is trapped above the SST front, the existence of mesoscale phenomena such as the Meiyu-Baiu front may be required to connect the tropical and midlatitude solutions in place of the westerly jet stream.
AS10-A023
Development of Composite Hydrological Drought Index for Northern Thailand Watershed
Duangnapha LAPYAI1#+, Chakrit CHOTAMONSAK1, Somporn CHANTARA1, Atsamon LIMSAKUL2
1Chiang Mai University, Thailand, 2Environmental Research and Training Center, Thailand
This research aims to assess the effectiveness of hydrological drought indicators in describing characteristics of drought events and to develop a composite hydrological drought index (CHDI) to better characterize the drought conditions in the northern watershed of Thailand, where hydrological droughts frequently occur as a result of climate change and land use. The study utilizes the WRF-CESM climate model and land cover data from MODIS (IGBP) as inputs for the VIC hydrological model to analyze the drought indicators. The VIC model includes surface soil moisture, runoff, precipitation, baseflow, first-layer soil moisture, evaporation, and second-layer soil moisture. The results showed that all parameters have moderate to high correlations with runoff gauge station data, respectively. The CHDI was further developed by combining the indicators using weights derived from the principal component analysis (PCA) technique. The CHDI showed a better correlation (r= 0.45-0.73) with the observed data and was closest to the low-volume water events declared by the Upper Northern Region Irrigation Hydrology Center.
AS10-A026
Footprints of Atlantic Multidecadal Oscillation in the Low-frequency Variation of Extreme High Temperature in the Northern Hemisphere
Miaoni GAO#+
Nanjing University of Information Science & Technology, China
The frequency and intensity of extreme high temperature (EHT) in the Northern Hemisphere exhibit remarkable low-frequency (LF) variations (longer than 10 years) in summer during 1951–2017. Five hotspots featuring large LF variations in EHT were identified, including western North America–Mexico, eastern Siberia, Europe, central Asia, and the Mongolian Plateau. The probability density functions show that the higher EHT occurrences over these hotspots in recent decades is consistent with the shifted average and increased variances in daily mean temperature. The common features of the LF variation in EHT frequency over all domains are the remarkable increasing trends and evident decadal to multidecadal variations. The component of decadal to multidecadal variations is the main contribution to the LF variations of temperature in the last century. Further analysis shows that the coherent variability of decadal to multidecadal temperature variations over western North America–Mexico, eastern Siberia, Europe, and the Mongolian Plateau are the footprints of a dominant natural internal signal: the Atlantic multidecadal oscillation. It contributes to the variations in temperature over these hotspots via barotropic circumglobal teleconnection, which imposes striking anomalous pressure over these regions. This study implies that natural internal variability plays an important role in making hotspots more vulnerable to EHT.
AS10-A029
Recent Changes and Related Factors of Tropical Night in the South Korea Metropolitan Area
TaeHun KANG1#+, Donghyuck YOON2, Junseo PARK1, Dong-Hyun CHA1
1Ulsan National Institute of Science and Technology, Korea, South, 2Princeton University, Korea, South
To investigate the recent change of tropical night in South Korea, we analyzed the duration and intensity of tropical nights (daily minimum temperature, Korea Meteorological Administration; KMA) for 40 years (1979-2018) quantitatively. Spatiotemporal analysis showed that the tropical nights in the Seoul metropolitan area were more intense and longer-lasting as compared to other South Korean regions. Specifically, the tropical nights over this region increased more prominently in intensity, frequency, and duration. The tropical night event in the metropolitan area was classified into pure-TN (no heatwave prior to tropical night) and HWTN (tropical night following heatwave). The composite analysis was conducted for two types of tropical night events, pure-TN, and HWTN, based on 40-year ERA5 reanalysis data. Pure-TN mostly occurred when the edge of western North Pacific subtropical high (WNPSH) was present over the Korean Peninsula with the southwesterly wind, leading to a positive temperature advection anomaly in the metropolitan area. Furthermore, a positive low cloud cover anomaly with enhanced downward longwave radiation also prevailed. On the other hand, HWTN mainly occurred when the WNPSH expanded northwestward until its center was located over the Korean Peninsula with a positive downward shortwave radiation anomaly. Moreover, a descending motion anomaly induced adiabatic heating over the metropolitan area was presented. The significant increasing trends in tropical night events (pure-TN: 0.143 day/year, HWTN: 0.077 day/year) were observed at 95% confidence level. To investigate these trends, the regression analysis was performed on the synoptic factors for three sub-analysis periods with 10 days (21-31 July;P1, 1-10 August;P2, 11-20 August;P3). As a result, the favorable atmospheric conditions for HWTN (pure-TN) have been frequently constructed during P2 (P1 and P3).
AS10-A034
Examining Taiwan's Extreme Rainfall Changes from an Event Perspective
Pin-Yu CHAO+, Cheng-Ta CHEN#
National Taiwan Normal University, Taiwan
Understanding the changes in extreme rainfall has raised a lot of attention since it is one of the major exposures in terms of climate risk. In Taiwan, extreme rainfall usually occurs with the unique environmental condition such as tropical cyclone or Mei-yu front. While Extreme indices has been widely used for analyzing extreme rainfall, the data sample is based on each grid instead of the extreme rainfall event itself. Therefore, investigating the extreme rainfall from the event perspective can provide a new insight for the changing extremes. Here we apply the event-tracking method by using Depth-First Search algorithm on high-resolution gridded observation data to track the extreme rainfall events from 1980 to 2019 in Taiwan. Two different thresholds (80mm and 200mm) are then selected for analysis due to their potential threats to river flood and flash flood. Our results show that the extreme rainfall events have increased significantly in both frequency and intensity. Frequency changes in extreme rainfall events indicate a 16.84% increase for 200mm-event and a 10.95% increase for 80mm-event. Mean changes of total rainfall volume also show a larger increase for 75.40% in 200mm-event than 33.03% in 80mm-event. Within all the contributors to the change of total rainfall volume, mean affected area contributes the most even without the effect of increasing rainfall intensity to the threshold. Furthermore, the increasing frequency of extreme rainfall events is larger in southern Taiwan than in northern Taiwan.
AS10-A037
Intense Western Disturbance Associated Extreme Precipitation Events Over Western Himalayas as Simulated by WRF Model
Nischal SHARMA+, Raju ATTADA#
Indian Institute of Science Education and Research Mohali, India
Extreme precipitation events (EPEs) associated with intense extratropical cyclonic storms (Western Disturbances; WDs) during the winter season (December through March) have the potential to induce catastrophic damages to life, infrastructure, environment and agricultural sustainability over the western Himalayas (WH). However, a sparse in-situ observational network in this region conjugated with complex topography highlights the uncertainties in available coarse resolution precipitation products and emphasizes the necessity of finer grid scaled regional climate models for accurate simulation of precipitation variability, specifically EPEs with highly localized characteristics as well as underlying synoptic dynamics. The present study is an effort to investigate the performance of a ultra-resolution Weather Research and Forecasting (WRF) model through the evaluation of its sensitivity to various microphysical schemes and their ensemble for the simulation of intense episodes of WDs and associated extreme precipitation events over the WH. The sensitivity of precipitation extremes (identified using percentile approach) to different microphysics (~3 km resolution), in the WRF model configured on two two-way nested domains (9km and 3km), has been validated using multi-source rainfall datasets including gauge-based (IMD) and satellite (IMERG) observations as well as with the latest regional reanalysis dataset, IMDAA. Different rainfall skill scores (CSI, ETS, BSS, HSS, POD and FAR) provided insight into how well WRF mimicked intense WDs and the accompanying rainfall. Furthermore, the corresponding dynamics and physical processes in the model has been elucidated through a composite analysis for the simulated EPEs using the reanalyses, IMDAA and ERA5. Our findings underpin the sensitivity of model-simulated winter precipitation extremes associated with intense WDs over WH to different microphysical parameterizations. Detailed results will be discussed.
AS13-A003
Historical Fidelity and Future Change of Amundsen Sea Low Under 1.5°C-4°C Global Warming in CMIP6
Miaoni GAO#+
Nanjing University of Information Science & Technology, China
The realistic simulation and projection of the Amundsen Sea Low (ASL) are essential for understanding the Antarctic climate and global climate change. Using 14 models that participated in phase 6 of the Coupled Model Intercomparison Project (CMIP6), this study evaluates the climatological characteristics of ASL with comparison to the ERA5 reanalysis and their CMIP5 versions and assesses the future change of ASL under 1.5℃-4℃ global warming. The climatological spatial distribution of ASL is captured reasonably but with underestimated intensity by CMIP6 multi-model ensemble (MME). Among the CMIP6 models, EC-Earth3 has most accurate representation of ASL according to the pattern correlation and biases. The seasonal variation of the ASL depth and location are found to be reasonably reproduced by the CMIP6 models. Compared with CMIP5, CMIP6 MME exhibit evident reduced uncertainties and overall improvement in simulating absolute depth and location of the ASL center, which might be attributed to models’ capability of representing westerlies, while the biases in relative depth become even large in CMIP6 MME. In response to future warming from 1.5℃ to 4℃ above pre-industrial levels, the absolute depth of ASL will very likely deepen with larger amplitude in all seasons, while the relative depth might enhance only under high-level warmer world in austral autumn to winter. The CMIP6 MME also projects that the ASL will shift poleward constantly in austral summer and migrate southwestward during austral autumn with the rising global mean temperature. The enhancement and poleward movement of ASL could also be identified during the Ross Sea ice advance season under 1.5℃-4℃ global warming. The results reveal the potential of CMIP6 models in the ASL study and the impact of ASL on Antarctic climate under different global warming levels.
AS13-A005
Two-way Interactions Between Storm Tracks and Sea Ice in the Southern Hemisphere
Xihui MAO#+, Li ZHANG
Ocean University of China, China
Using the lagged maximum covariance analysis (MCA), the present study investigates the interannual variability of the storm track in the Southern Hemisphere and the Antarctic sea ice throughout the year. The results show that the two are most tightly coupled in the austral cold seasons. Specifically, storm track anomalies in June and July are associated with a zonal dipole structure of the sea ice concentration (SIC) anomalies in the western Hemisphere, with centers in the Antarctic Peninsula and the Amundsen-Bellingshausen Seas. The storm track can modulate the large-scale atmospheric circulations, which induces anomalous meridional heat transport, downward longwave radiation, and mechanical forcing to further influence the SIC anomalies. The resultant SIC anomalies can last for several months and have the potential to feed back to the storm track. According to the MCA, the influence of the SIC anomalies to the storm track is most evident in August. The SIC dipole along with the SIC anomalies in the Indian Ocean sector have large impact on the storm track activities downstream. The SIC anomalies alters the near-surface temperature gradient and subsequently atmospheric baroclinicity. Further energetic analysis suggests that the enhanced atmospheric baroclinicity facilitates the baroclinic energy conversion from mean available potential energy to eddy available potential energy, and then to eddy kinetic energy, strengthening the storm track activities over the midlatitude Indian Ocean.
AS13-A010
Seasonal and Interannual Variations of Poleward Moisture Transport by Atmospheric Rivers in the Southern Hemisphere
Kyu-Myong KIM1#+, Alexa HENNY1,2
1NASA Goddard Space Flight Center, United States, 2NASA Postdoctoral Program, United States
Atmospheric Rivers (AR) accounts for more than 90% of poleward moisture transport across midlatitudes of both hemispheres and has a crucial impact on hydrological cycle and surface mass balance over the Antarctic ice sheets. Here we investigate the seasonal and interannual variations of the poleward moisture transport by AR using 43-year MERRA-2 reanalysis data. Integrated water vapor transport (IVT) is used to detect AR with latitude dependent thresholds of IVT to better detect AR-like features in the polar regions. Based on 3-hourly AR statistics, four main AR genesis regions in the southern hemisphere (i.e., southern Africa and southwestern Indian Ocean, southern Pacific Ocean, South America monsoon region, and Australia) are identified. In this talk, the variations of AR frequency and intensity at each genesis regions and associated patterns of atmospheric circulations and its impact on the poleward moisture transports will be discussed on intraseasonal, seasonal, and interannual timescales.
AS13-A011
Cause of the Extreme Warming Event on February 9, 2020, in Seymour Island, Antarctic Peninsula
Hyo-Jun BAE1+, Seong-Joong KIM2,3#, Baek Min KIM1, Ha-Taek KWON4
1Pukyong National University, Korea, South, 2Korea Polar Research Institute, Korea, South, 3University of Science and Technology, Korea, South, 4Seoul National University, Korea, South
In early February 2020, two consecutive extreme warming events occurred within three days of each other at the same location in the Antarctic Peninsula (AP). The second event on February 9, 2020, saw the temperature reach 15.5°C at Marambio station on Seymour Island, northeast of the AP, the second-highest recorded temperature. To understand the cause of the extreme warming event, observational data from Marambio station and the European Center for Medium-Range Weather Forecasts Reanalysis v5 (ERA5) data were analyzed to examine extreme warming events that had occurred on Seymour Island during February over the past 40 years. The analysis revealed that the extreme warming event on February 9, 2020 was caused by foehn winds and large-scale horizontal advection, which are associated with a strong blocking high in the upper and lower atmosphere. Unlike typical extreme warming events in February over the past 40 years, the event in 2020 occurred not only in the AP but also throughout the entire West Antarctica.
AS13-A014
Teleconnection of the El Niño-southern Oscillation Impacts on the Antarctic Sea Ice Under the Near Future Condition
Jihae KIM1+, Daehyun KANG2, Myong-In LEE1#
1Ulsan National Institute of Science and Technology, Korea, South, 2Korea Institute of Science and Technology, Korea, South
The El Niño–Southern Oscillation (ENSO) is well-known climate variability in the tropics that has the potential to affect the Antarctic sea ice. The sea ice concentration pattern induced by ENSO is primarily linked with an anticyclonic circulation anomaly in the Amundsen-Bellingshausen Sea (ABS) that modulates atmospheric poleward temperature advection and longwave radiation forcing via poleward moisture advection. In the current climate, the remote influences between the tropics and the Antarctic are strongest during Austral spring (September-October-November, SON). However, this seasonality can change in future conditions. Comparing the remote influences from the tropics to the Antarctic between the present (1982-2014) and the near future (2015-2050) using the CMIP6 historical and SSP585 experiments, the positive geopotential heights at 500 hPa in the ABS regressed onto the ENSO index becomes stronger in Austral winter (June-July-August, JJA). This results in a more extended melting period of sea ice by the remote forcing from the tropics. The stronger response in the upper-level geopotential height anomalies in JJA is suggested by the increased forcing in the tropics and strengthened jet stream. The global model experiments with a dynamical core only support well these changes in the dynamical mechanisms related to the Antarctic sea ice condition in the future.
AS14-A005
Subseasonal Forecasts of Precipitation Over Maritime Continent in Boreal Summer and the Sources of Predictability
Yang LYU#+, Xiefei ZHI, Yan JI
Nanjing University of Information Science & Technology, China
The current paper investigates the weekly forecasts skills on precipitation in boreal summer over Maritime Continent (MC), which is an area featured by complex topography, warmest oceans, and characterized by great vulnerabilities to high-impact precipitation events, for the models of European Centre for Medium-Range Weather Forecasts (ECMWF) and China Meteorological Administration (CMA) derived from the S2S Project. Results indicate that the ECMWF model shows generally superior forecast performances than CMA, which is characterized by lower errors and higher correlations compared with the observations. Meanwhile, ECMWF tends to produce wet biases with increasing lead times, while the mean errors of CMA are revealed to be approximately constant throughout lead times of 2–4 weeks over most areas. Besides, the temporal correlations between model outputs and observations obviously decrease with growing lead times, with a high-low distribution presented from north to south. In order to detect the sources of predictability, the roles of large-scale drivers like ENSO and BSISO in modulating subseasonal precipitation forecast skills are also assessed in the models. Both ECMWF and CMA can reasonably capture the ENSO related precipitation anomalies for all lead times, while their capabilities of capturing BSISO related precipitation anomalies decrease with growing lead times, which is more obvious in CMA. The enhanced subseasonal precipitation forecast skills mainly respond to the BSISO associated precipitation variability. For most MC areas such as southern Indochina, western Indonesia, Philippines and the eastern ocean, the forecast skills of both ECMWF and CMA can be improved to a great extent by enhancing the capture of BSISO related precipitation anomalies, with the temporal correlations for both ECMWF and CMA increased by about 0.15 for lead times of 3–4 weeks. It provides an opportunity window for the models to improve precipitation forecasts on the subseasonal timescale.
AS14-A006
Improved MJO Prediction Using a Multi-member Subseasonal to Seasonal Forecast System of NUIST (NUIST CFS 1.1)
Jiye WU1,2#+, Yue LI3, Jing-jia LUO1, Xianan JIANG4, Takeshi DOI2, Toshio YAMAGATA2
1Nanjing University of Information Science & Technology, China, 2Japan Agency for Marine-Earth Science and Technology, Japan, 3New South Wales Government, Australia, 4University of California, Los Angeles, United States
The Madden-Julian Oscillation (MJO) provides an important source of global subseasonal-to-seasonal (S2S) predictability, while its prediction remains great challenges. Based on an atmosphere-ocean coupled model and the widely-used nudging method, suitable initialization and ensemble schemes are explored toward an improved MJO prediction. It is found that strong but not excessive relaxation strength for the divergence and vorticity, and a mild relaxation for the air temperature are appropriate to generate good atmospheric initial conditions. Additionally, the ensemble strategy with perturbed atmospheric nudging coefficients conduces to adequate ensemble spread and hence improves the prediction skill.Here, an 18-member ensemble subseasonal prediction system called NUIST CFS1.1 is developed. Skill evaluation indicates that the NUIST CFS1.1 can extend the MJO prediction to 24 days lead, which outperforms a majority of current models in the S2S project but is far from the estimated potential predictability (~47 days). The limited skill at longer lead times corresponds to forecast errors exhibiting slower propagation and weaker intensity, which are largely owing to the model’s shortcoming in representing MJO-related physical processes. The model underestimates the diabatic heating of enhanced convection and fails to reproduce the suppressed convection within the MJO structure, collaboratively weakening the Kelvin/Rossby waves. This causes weaker horizontal winds and ultimately reduces the horizontal moisture advection on the two flanks of MJO convection. Furthermore, the underestimated Kelvin wave induces insufficient planetary boundary layer (PBL) convergence and thereby results in poor simulation of PBL premoistening ahead of MJO convection. These biases limit the MJO prediction in the NUIST CFS1.1, prompting further efforts to improve the model physics.
AS14-A008
Predictability Limit of Monsoon Intraseasonal Precipitation and its Prediction in S2S Models: An Implication of Central Indian Ocean Mode
Jianhuang QIN1#+, Lei ZHOU2, Baosheng LI3
1Hohai University, China, 2Shanghai Jiao Tong University, China, 3Ministry of Natural Resources, China
The prediction of monsoonal precipitation during Indian summer monsoon (ISM) remains difficult. Due to the high correlation between the Central Indian Ocean (CIO) mode index and the ISM precipitation variability, the predictability limit of the CIO mode index is investigated by the non-linear local Lyapunov exponent (NLLE) method in observations. Results show that the predictability limit of the CIO mode index can reach 38 days during boreal summer (from June to September), which is close to the upper predictability limit of intraseasonal precipitation (up to 40 days), and higher than the predictability limits of dynamical monsoon indices (under 3 weeks) and boreal summer intraseasonal oscillation (BSISO) indices (around 30 days). Such high predictability limit of the CIO mode index is mainly attributable to the long predictability limits from the intraseasonal sea surface temperature (SST) and intraseasonal zonal wind, which are the components of the CIO mode. However, the prediction skill of the CIO mode in the subseasonal-to-seasonal (S2S) air–sea coupled models is still an issue. The ECMWF and UKMO models display significantly higher skills for up to about 2 and 3 weeks, respectively, which are longer than other S2S models. The decline of the CIO mode prediction skill is due to the reduced signal of subseasonal zonal winds at 850 hPa over the tropical central Indian Ocean (especially along the equator; 5°S–5°N, 70°E–85°E). Therefore, a better simulation of tropical subseasonal zonal winds is required to improve the CIO mode prediction in models, and the improvement will benefit a better MISO simulation and a higher prediction skill during the ISM.
AS14-A010
Machine Learning Based Subseasonal to Seasonal (S2S) Forecasts for Warm Season Predictability
Venkatesh BUDAMALA+, Rajarshi DAS BHOWMIK#
Indian Institute of Science, India
S2S forecast has significant potential to aid decision-makers in mitigating extreme weather risks. Efficient S2S forecasts employ a central component between Weather and Climate predictions (for two weeks to less than a season). S2S models can yield adequate information based on the probability of the occurrence of extreme events within sufficiently larger areas through the prediction of complex, large-scale predictors. However, one of the significant challenges for S2S forecast is to develop a robust relationship for warm season predictability. A warming climate amplifies extreme events, making them a greater societal threat. Therefore, the current study develops an adaptive machine learning approach to predict the weekly frequency of intense warm days and 14-day standardized precipitation index (SPI) during the warm season for the Mahanadi River basin, India. The framework incorporates the multiple S2S global forecast models and ensembles across a continuum of S2S timescales to characterize the deterministic predictability of warm season atmospheric teleconnection patterns. The current skillful S2S forecasts of extreme heat and precipitation in warm season greatly benefit multiple sectors, including water management, public health, and agriculture, in mitigating the impact of extreme events.
AS14-A012
Key Regions in the Modulation of Seasonal GMST Variability by Analyzing the Two Hottest Years: 2016 vs. 2020
Kexin LI1+, Fei ZHENG2#, Deyang LUO2, Cheng SUN3, Jiang ZHU2
1Institute of Atmospheric Physics, Chinese Academy of Sciences, China, 2Chinese Academy of Sciences, China, 3Beijing Normal University, China
As an important parameter to measure the exchange of surface fluxes and climate sensitivity, the surface temperature is used to reflect specific responses to climate changes. The global mean surface temperature (GMST) justifiably became a primary indicator of climate volatility on a global scale to evaluate the intensity of climate change. However, the GMST peaked in 2020 under the background of moderate La Niña and even beat the highest record of GMST in 2016 when a strong El Niño occurred. The phenomenon overturned the conventional idea that the highest GMST occurs with strong El Niño. Our work used several datasets of surface temperature and adopted the ensemble empirical mode decomposition (EEMD) algorithm to distinguish the sources of direct contribution to the highest GMST of 2016 and 2020 at different timescales, especially focusing on the subseasonal-to-interannual variations. The results show that high GMST in 2016 was controlled by secular trend (SCT) and annual variability (ANV). However, the dominator of the sharp GMST rise in 2020 was SCT alone because the ANVs in different seasons canceled each other out in 2020, contributing little to the annual mean GMST. We further revealed two prominent patterns of seasonally varying ANVs, one is induced by atmospheric internal variability and the other is related to ENSO. The two patterns mainly located in Eurasia, North America, the Arctic Ocean, and the tropical eastern Pacific Ocean. Dominance by surface temperatures over the four crucial regions on the subseasonal-to-seasonal (S2S) GMST variations was also observed in nearly 80% of the years during 1982-2021, indicating a potential opportunity to improve the S2S GMST forecast by ameliorating the forecast in the four areas. Whether the contribution of ANV will become weaker and weaker in a warmer future world will be the concern of follow-up work.
AS14-A013
PISSARO: A Collaborative and User-oriented Project on the Monthly Forecasting of Extreme Events in the Southwest Indian Ocean
Sylvie MALARDEL1#+, Helene VEREMES1, Francois BONNARDOT2, Keunok LEE3
1Université de La Réunion - CNRS, France, 2Meteo-France, Reunion, 3CNRS - Université de La Réunion - Météo-France, Reunion
The PISSARO project focuses on atmospheric and oceanic forecasting at the subseasonal scale for applications over the southwest Indian Ocean basin. It is a collaborative academic research project, developed and conducted in partnership with stakeholders from Reunion and Seychelles and a panel of scientific experts in tropical forecasting. We have exploited the IFS monthly forecast ensemble for the development of future S2S-derived forecast products to provide probabilities of tropical cyclone trajectory scenarios, rainfall anomalies and to follow the ITCZ migration in the southwest Indian Ocean. The products which have been designed and calibrated with the S2S data are now tested in real time during the 2023 austral summer by the forecasters of the Seychelles Meteorological Authority and at the Regional Specialised Meteorological Centre - Tropical Cyclones of La Réunion. A co-creation approach between scientists, forecasters and humanitarian stakeholders has also enabled the development of products to anticipate the cyclone hazard in the southwest Indian Ocean region to support the tropical cyclone disaster risk management. The PIROI is testing this product under operational conditions for the 2022-2023 cyclone season. At the end of the TC season, all these prototypes will be evaluated and the best products will be selected for an operational implementation. We will provide an overview of these products at the workshop.
AS14-A015
The Role of Sea Surface Temperature Anomalies in Latent Heat Transport in the Northern Hemisphere
Kyungmin KWAK1+, Hajoon SONG1#, Myung-Seo KOO2, Eunjeong LEE2, Jun-Seong PARK2
1Yonsei University, Korea, South, 2Korea Institute of Atmospheric Prediction Systems, Korea, South
The heat transfer through atmospheric circulation is vital in determining local weather patterns. In the boreal summer, latent heat transport is the main contributor to the moist static energy transport from the equator to high latitudes. Using a global coupled atmosphere-ocean model (KIM-NEMO), we analyze the impact of ocean coupling on the subseasonal-to-seasonal (S2S) prediction of latent heat transport. The results showed that the highest latent heat transport in the boreal summer was along the eastern part of the continent. The simulations in July 2017 revealed the significant differences between KIM and KIM-NEMO, particularly over the Western North Pacific Ocean. These changes were triggered by the cold SST anomalies (SSTA) in KIM. The improvement of cold SSTA through ocean coupling influenced the regional wind patterns, leading to modifications in moisture transport. Consequently, latent heat transport is simulated more realistically, when considering air-sea interactions.
AS14-A019
Comparison of Monthly Rainfall Predictions Over Singapore for Improved Climate Services
Thea TURKINGTON#+, Wee Leng TAN, Chen SCHWARTZ, Shipra JAIN
Centre for Climate Research Singapore, Singapore
Situated in the deep tropics, Singapore experiences considerable intra- and interannual variability of rainfall. Therefore, improving rainfall predictions, including the 1-month rainfall outlook, is an important component of improving climate services for Singapore. Traditionally, seasonal prediction models were used as the basis for predicting rainfall for the next month and next season. These seasonal predictions were also combined with additional information, such as the status and outlook of climate drivers such as ENSO (El Nino Southern Oscillation) and MJO (Madden Julian Oscillation) to produce an expert-based outlook. However, for users who do not require outlooks prior to the end of the month, S2S predictions can be used instead, with S2S predictions issued towards the end of the month showing improved skill compared to the seasonal predictions for the 1-month rainfall outlook. This work compares the 1-month rainfall outlook for Singapore from various sources including seasonal models (single models and multi-model ensemble), the ECWMF extended range model as well as along with expert judgment for the period 2020 – 2022. The benefits of the various types of outlooks will also briefly be discussed as part of improving climate services for the country.
AS14-A020
The Winter North Pacific Teleconnection in Response to ENSO and the MJO in Operational Subseasonal Forecasting Models is Too Weak
Chen SCHWARTZ1+, Chaim GARFINKEL2#, Wen CHEN3, Yanjie LI4, Daniela I.V. DOMEISEN5
1Centre for Climate Research Singapore, Singapore, 2Hebrew University of Jerusalem, Israel, 3Yunnan University, China, 4Chinese Academy of Sciences, China, 5ETH Zurich, Switzerland
Teleconnection patterns associated with the Madden–Julian oscillation (MJO) and El Niño–Southern Oscillation (ENSO) impact weather and climate phenomena in the Pacific–North American region and beyond, and therefore accurately simulating these teleconnections is of importance for seasonal and subseasonal forecasts. Systematic biases in boreal midwinter ENSO and MJO teleconnections are found in eight subseasonal to seasonal (S2S) forecast models over the Pacific–North America region. All models simulate an anomalous 500-hPa geopotential height response that is too weak. This overly weak response is associated with overly weak subtropical upper-level convergence and a too-weak Rossby wave source in most models, and in several models there is also a biased subtropical Pacific jet, which affects the propagation of Rossby waves. In addition to this overly weak response, all models also simulate ENSO teleconnections that reach too far poleward toward Alaska and northeastern Russia. The net effect is that these models likely underestimate the impacts associated with the MJO and ENSO over western North America, and suffer from a reduction in skill from what could be achieved.
AS14-A021
Evaluation of a Spatial Approach to the Verification of Gridded S2S Wind Forecasts for Southeast Asia
Wee Leng TAN#+, Thea TURKINGTON, Shipra JAIN, Chen SCHWARTZ
Centre for Climate Research Singapore, Singapore
Weather and climate in Southeast Asia are heavily influenced by the Monsoon, with the Monsoon traditionally characterised by the seasonal change in wind directions along with seasonal changes in precipitation. Wind observations or reanalysis data are commonly used for defining the Monsoon period and therefore having wind forecast for the region can provide information on the upcoming onset and cessation of the Monsoon. A spatial approach to the verification of gridded S2S wind forecasts for Southeast Asia is investigated and analysed. The approach uses the fractional skill score (FSS), a neighbourhood spatial verification method commonly used for verifying high resolution precipitation forecast. This spatial approach verification method avoids the problems of conventional local grid-based verification metrics, such as double-penalty when predicting the correct pattern of wind but at the wrong position, and can highlight the spatial displacement of the wind patterns in the forecast. The score for the ECMWF Extended Range wind forecast for Southeast Asia region will be evaluated and compared with the conventional local grid-based verification metrics for the added information using the spatial approach. The possibility of the usage of sub-seasonal wind forecast for the Monsoon onset and cessation forecast in the region will also be discussed.
AS14-A022
MJO-related Rainfall in Southeast Asia: How Well is it Represented by Subseasonal Operational Forecasting Models?
Chen SCHWARTZ#+, Thea TURKINGTON
Centre for Climate Research Singapore, Singapore
The Madden-Julian Oscillation is the dominant source of rainfall variability in the tropics on subseasonal timescales. As such, the MJO plays a significant role in forecasting tropical rainfall on 2-3 weeks timescales, and previous studies have shown an improvement in extreme rainfall prediction skill when an MJO event was present. Southeast Asia (SEA) is greatly affected by intraseasonal rainfall variability associated with the MJO, and improvement of subseasonal prediction skill of MJO-related rainfall could benefit both stakeholders and the vast population in the region. In this work, we assess the representation of MJO-related rainfall in subseasonal forecasting models. Specifically, we will explore how well the commonly used MJO monitoring indices can represent rainfall associated with MJO in SEA, both in observations and the models. The skill of the models to simulate MJO-related rainfall in sub-regions in SEA where different MJO phases show the largest subseasonal variability will be examined, as well as the seasonality in prediction skill of MJO-related rainfall in these sub-regions.
AS14-A023
Influence of Compound Zonal Displacements of the South Asia High and the Western Pacific High on Meiyu Subseasonal Variation
Zhiwei ZHU#+, Shanshan FU
Nanjing University of Information Science & Technology, China
Meiyu shows substantial subseasonal variation at periods of 10–30 days and 30–60 days, which often leads to extreme precipitation and disastrous flooding over the Yangtze River Basin. Monitoring and prediction of the subseasonal variation of Meiyu is crucial for disaster prevention and mitigation. Here, we proposed two sets of novel indices for Meiyu real-time monitoring and prediction based on the compound zonal displacements of the South Asia high (SAH) and the western Pacific high (WPH) at 10–30-day and 30–60-day period. For the 10–30-day period of Meiyu, the zonal displacement of the SAH is associated with a mid-latitude Rossby wave train, whereas the WPH is related to the second mode of the boreal summer intraseasonal oscillation. On the 30–60-day timescale, the zonal displacement of the SAH and the WPH are both associated with the first mode of the boreal summer intraseasonal oscillation. The subtle differences in zonal displacement of the SAH and the WPH determine eight type configurations, corresponding to distinct influences on Meiyu. Meiyu subseasonal variation can be well reconstructed by using the relationship between these two indices and rainfall anomalies pattern over China. Given that the ECMWF S2S model is more skillful in forecasting upper- and lower-level circulation than that in directly forecasting precipitation, a hybrid dynamical–statistical model is conducted to predict the Meiyu subseasonal variation with the ECMWF model forecast indices. The hybrid model outperforms the ECMWF model in predicting the Meiyu subseasonal variation at 17–40-day lead times.
AS15-A009
Assimilation of Aerosol Optical Depth from Geostationary Environmental Monitoring Spectrometer to Improve a Prediction of Asian Dust Storm
Ebony LEE1+, Milija ZUPANSKI2, Seon Ki PARK1#
1Ewha Womans University, Korea, South, 2Colorado State University, United States
In the spring season, Korea suffers from the Asian dust storms (ADSs) sometimes originated from the Gobi Desert and Inner Mongolia. Since the ADSs are known to deteriorate respiratory or eye health as well as visibility, it is important to predict the occurrence and the intensity of ADSs through numerical prediction and satellite observations. In this study, we assimilate aerosol optical depth (AOD) retrieved from Geostationary Environmental Monitoring Spectrometer (GEMS) observing East Asia. The ADSs are affected by various atmospheric (e.g., wind, temperature, planetary boundary layer, etc.) and land surface conditions (e.g., land use, soil temperature, soil moisture, etc.). Therefore, we employ a coupled meteorology-chemistry model --- the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) --- in order to consider the complex interactions among the atmospheric and land surface variables simultaneously. The Maximum Likelihood Ensemble Filter (MLEF) is adopted to assimilate AOD. For an ADS case in March 2021, it is shown that the GEMS AOD assimilation improves the analysis and prediction of AOD and is useful for ADS prediction in the East Asia region.
AS15-A012
Identifying Sensitive Areas for Targeted Observations to Improve Numerical Prediction of Asian Dust Storms Over South Korea
Seungyeon LEE1+, Xiaohao QIN2, Seon Ki PARK1#
1Ewha Womans University, Korea, South, 2Chinese Academy of Sciences, China
In air quality prediction, initial conditions are essentially required for a coupled atmosphere-chemistry model which is based on both atmospheric and aerosol/chemistry observations. In general, a higher amount and quality of observations produce more accurate model results; however, forecast errors in a region of interest may grow from an initial error in a specific upstream region, primarily due to the lack of observations therein. Therefore, it is a milestone to find the upstream areas from which a small initial error can grow into large forecast errors in the region of interest. The conditional nonlinear optimal perturbation for initial conditions (CNOP-I) is a suitable tool for adaptive (targeted) observations. To calculate the CNOP-I, several variables are included in defining multiple energy equations (e.g., kinetic energy, dry energy, moist energy, etc.). In particular, the previous studies on improving the Asian dust storms (ADSs) prediction mainly considered the kinetic energy calculation, which included only two variables (u-wind and v-wind). The goal of this study is twofold: finding variables that strongly affect the ADSs and identifying sensitive areas for the adaptive observations. We collected and examined the ADS events that occurred during the last 32 years (1990—2021) over South Korea. Through the principal component analysis, we first recognized top variables—temperature, vertical velocity, divergence, specific humidity, ozone mass mixing ratio, and eastward wind—which affect origination and translocation of the ADSs; for example, strong downdraft and divergence make ADSs finally land on the Korean Peninsula. We are applying the CNOP-I to identify the sensitive areas for adaptive observations in air quality prediction. We expect to improve air quality forecasts by classifying the synoptic situations that brings about severe ADS outbreaks in South Korea and by identifying the upstream areas for adaptive observations to which we can enhance observations, potentially through international collaborations.
AS16-A001
Changes in the SST-precipitation Relationship Over the Indo-pacific Warm Pool Under a Warming Climate
Hye-Ryeom KIM+, Kyung-Ja HA#
Pusan National University, Korea, South
The Indo-Pacific warm pool (IPWP) is a region with one of the strongest atmospheric convections on Earth and deep convection over the IPWP plays a key role in global climate. In recent decades, it has experienced human-induced warming. In addition, it has been observed to have a non-linear relationship between Sea Surface Temperature (SST) and precipitation. Even though SST is increasing, the increase in precipitation is limited up to a specific SST, defined as saturation threshold SST (STT). Existing STT indicates that a completely different state occurs before and after STT showing a non-linear response of precipitation to SST. However, how warmer climates affect changes in the SST-precipitation relationship as well as STT is yet to be unexplored. To investigate future changes in the relationship between SST and precipitation, we used a joint distribution of the two variables with the historical data as well as three Shared Socioeconomic Pathway (SSP) scenarios (SSP2-4.5, SSP3-7.0, and SSP5-8.5) during the near future (2041-2060), and far future (2081- 2100). The results demonstrate that with the shift of mean state, the STT rises due to the involvement of atmospheric stratification in all three scenarios in both future periods, but the largest increase is observed in the SSP5-8.5 scenario during the far future. In the warming climate, greater warming in the upper troposphere compared to the surface leads to stabilization of the troposphere, supporting an increase in STT through Moist-Adiabatic Lapse Rate (MALR) adjustment. This study suggests a change in the SST-precipitation relationship and a possible mechanism for a limited increase in precipitation, and thus provides a background for a better understanding of a non-monotonic precipitation response to SST in the context of climate change.
AS16-A004
Convectively-coupled Kelvin Waves: Moist Static Energy and Gross Moist Stability Analyses
Yi-Bin HORNG+, Jia-Yuh YU#
National Central University, Taiwan
Convectively-coupled Kelvin wave (CCKW) is one of the important large-scale oscillations in the equatorial area. It is an eastward-propagating mode that constantly causes fluctuations in pressure and winds, and thus, CCKW takes part in shaping the weather and climate through bringing countless rainfall events to countries in tropics. CCKW is relatively active in the Pacific and the Indian basins due to the absence of obstruction from topography, and yet it shows distinct properties over these two regions, including the intensity, active season, symmetry, and propagation speed. The vertical profiles also suggest the differences in tilting angle and the extent of low-level pre-moistening at the leading edge of the convection. It is hypothesized that the differences arise from the mechanisms in triggering the convection associated with CCKW. We conduct a detailed moist static energy (MSE) budget analysis to uncover the dominant factors in driving the energy recharge-discharge process of CCKW. The results indicate that the key factors might lie in the horizontal advection and moisture profile, especially within the boundary layer. The gross moist stability, a measure of development of moist convection, is also tested over the two regions. It is speculated that the background environmental conditions play a major role in determining the structures of CCKW.
AS16-A011
Climatology and Environmental Conditions of Two Types of Quasi-linear Convective Systems with Extremely Intense Weather in North China
Jie SHENG#+
National Meteorological Center of China, China
In this work, the spatial and temporal distribution characteristics of 171 QLCS cases in North China identified by an objective identification method for the period 2013—2018 are analyzed. According to the statistics of intense weather produced by them, at least two types of QLCSs exist: one type with strong thunderstorm wind gusts and the other with extreme heavy rainfall. Furthermore, the characteristics of circulation pattern, environmental condition, terrain effect, and surface cold pool as a key type of mesoscale system are given for the two types of QLCSs. The findings are presented as follows. The spatial distribution of QLCSs in North China. There are significant differences in the month of occurrence, the spatial scale, the moving speed, the formation time and maintenance period between the two types of QLCSs. The circulation background, environmental conditions and cold pool are also obviously different. The atmospheric baroclinicity is relatively obvious for QLCSs with strong thunderstorm wind gusts. The large value area of BCAPE and DCAPE caused by the dry middle layer and large temperature reduction rate are important environmental conditions for the generation of strong convective wind gusts. The strong cold pool and vertical wind shear within the layer of 0—3 km altitude play an important role in the forward propagation of the QLCSs. Extreme precipitation caused by QLCSs with heavy rainfall is more prominent for this type of QLCSs than that for the previous type. The second type of QLCSs usually occur in weak synoptic-scale forcing systems with sufficient water vapor supply. The back propagation maintained by the interaction between the weak cold pool or the windward slope and the low level southerlies is the main mechanism for the development and slow movement of the QLCS, which is also directly responsible for extreme heavy rainfall.
AS17-A011
Validation, Analysis, and Comparison of MISR V23 Aerosol Optical Depth Products with MODIS and AERONET Observations
Ruonan FAN+, Yingying MA, Shikuan JIN#
Wuhan University, China
The latest Multi-angle Imaging Spectro Radiometer (MISR) V23 aerosol optical depth (AOD) products were released, with an improved spatial resolution of 4.4 km, providing an unprecedented opportunity for the refined regional application. To ensure the reliability of their applications and build a scientific reference for the further optimization, it is imperative to conduct a comprehensive evaluation, especially for the unique size-resolved AOD products: small-size AOD (AODS, representing the contribution of fine-mode aerosols), medium-size AOD (AODM), and large-size AOD (AODL), and AODM+L represents the AOD part of coarse-mode aerosols. AErosol RObotic NETwork (AERONET) and MODerate-resolution Imaging Spectroradiometer (MODIS) C6.1 aerosol products from 2001 to 2020 are utilized for the validation, analysis, and inter-comparison, considering three spatial scales and four key factors. In general, MISR V23 aerosol products show a good accuracy compared with AERONET. The best performance for all AOD products appears in forest units (the highest R ~ 0.93, data percentage within Expected Error bounds, %EE > 93), related to the inactive human activity and dark underlying surface. Dependences of retrieval deviations illustrate that the performance of MISR AOD deteriorates as aerosol loading increases. Namely, with the increase of aerosols, total AOD (AODT) and AODS show increasing negative deviations, while increasing positive deviations are observed for AODM+L. This suggests that the Empirical Orthogonal Functions do not perform well in this situation, since numerous aerosol particles can obstruct the underlying reflection and reduce the surface spectral contrast. In addition, AODT and AODS often exhibit anomalous positive deviations in areas with low vegetation cover, such as deserts, revealing that MISR will overestimate aerosol content over bright surfaces and in environments dominated by coarse-mode particles. The above findings not only deepen the understanding of MISR aerosols products from multiple perspectives, but also provide useful information for the product improvement.
AS17-A012
Toward a Versatile Spaceborne Architecture for Immediate Monitoring of the Global Methane Pledge
Pengfei LI#+
Hebei Agricultural University, China
The global methane pledge paves a fresh, critical way toward Carbon Neutrality. However, it remains largely invisible and highly controversial due to the fact that planet-scale and plant-level methane retrievals have rarely been coordinated. This has never been more essential within a narrow window to reach the Paris target. Here we present a two-tiered spaceborne architecture to address this issue. Using this framework, we patrol the world, like the United States, China, the Middle East, and North Africa, and simultaneously uncover methane-abundant regions and plumes. These include new super-emitters, potential leakages, and unprecedented multiple plumes in a single source. More importantly, this framework is shown to challenge official emission reports that possibly mislead estimates from global, regional, to site scales, particularly by missing super-emitters. Our results show that, in principle, the above framework can be extended to be multi-tiered by adding upcoming stereoscopic measurements and suitable artificial intelligence, thus versatile for immediate and future monitoring of the global methane pledge.
AS17-A017
A Case Study of Extreme Precipitation Forecast Based on Satellite Data Assimilation in North China
Jiexia WU#+, Jiawen CUI, Xiangze JIN, Fangyuan PING, Shiyu ZHUANG
PIESAT, China
This study used Weather Research and Forecasting model (WRF) 4.4 and Weather Research and Forecasting model data assimilation system (WRFDA) 3D-var assimilation system to analyze and predict two extreme precipitation events in North China during summer 2022. Based on the system, different satellite data were assimilated in the initial field to improve the accuracy of the model forecast. The satellite data used in this study are NOAA AMSU-A/B, FY-3D MWHS-II/MWTS-II, FY-4A AGRI and Himawari-8 AHI. Artificial intelligence algorithm was applied to these satellite data to retrieve atmospheric temperature and moisture profiles, and these results were used for data assimilation in the system. In this study we have designed three experiments: 1 control run and 2 experiments. The control run only assimilated conventional data to the initial field. Besides the conventional data, the first experiment assimilated AI retrieved atmospheric temperature and moisture profiles and the second experiment assimilated brightness temperature from these sensors. We conducted 72 hours forecast for all the experiments and evaluated the precipitation amount and area with observed data. The results showed that the AI algorithm that we have developed in this study performed well in atmospheric temperature and moisture profile retrieval and the temperature and moisture profiles had positive contributions to precipitation forecast. According to TS, FAR and POD sores, the second experiments showed high accuracy in 0-6 hour precipitation forecast.
AS17-A020
Retrieval of Total Precipitable Water from Gk2A/AMI Data Using Machine Learning Approach Over Korea
Hyejin MOON1#+, Jae-Young BYON2, Myoung-Hee LEE1
1Korea Meteorological Administration, Korea, South, 2National Institute of Meteorological Research, Korea, South
Total precipitable water (TPW), a column of water vapor content in the atmosphere, is an important meteorological factor and play a critical role in the occurrence of precipitation and atmospheric river. Traditionally TPW has been calculated from using vertical profiles of temperature and humidity. But operational TPW derived from GK2A provides under only clear sky conditions and TPW calculated from radiosonde observations provides in several stations at 4 times in a day. To overcome temporal and spatial limitation of these TPW, this study proposes a retrieval algorithm based on convolutional neural network (CNN) model to retrieve TPW from geostationary Korea multi-purpose satellite 2A (GEO-KOMPSAT 2A, GK2A) equipped with the Advanced Meteorological Imager (AMI). The TPW is prepared by integrating the water vapor profiles from radiosonde observations over Korea. The algorithm performances are assessed using radiosonde observations for other period as the reference data. Through statistical verification, the results show that the CNN model performs with a root mean square error (RMSE) of 9.42 (5.32) mm, a bias of 0.02 (-0.76) mm, and a correlation coefficient of 0.88 (0.94) under all (clear) sky conditions. This study addressed the availability of satellite-derived TPW to resolve the limitations of in situ measurements and cloudy sky conditions. Both the quantity and the quality of data are important in machine learning approach. We will expand training data like as GNSS and numerical weather forecast model to improve retrieval of TPW.
AS17-A022
Development of Atmospheric Profile Retrieval Algorithm for FY-4A/B GIIRS
Hye-In PARK#+, Byung-il LEE, Junhyung HEO, Myoung-Hee LEE
Korea Meteorological Administration, Korea, South
The National Meteorological Satellite Center of the Korea Meteorological Administration has developed an algorithm to retrieve the atmospheric profiles for Geostationary Interferometric Infrared Sounder (GIIRS) onboard FengYun-4A/B (FY-4A/B). Hyperspectral infrared sounder with thousands of channels has a high vertical resolution, so it can estimate more accurate atmospheric temperature and humidity profiles and is useful for monitoring severe weather such as typhoons and heavy rainfall because it highly depends on atmospheric instability and water vapor information. To develop the algorithm for GIIRS of FY-4A/B, channel selection, and systematic bias correction were performed. The channel was chosen to consider the vertical distribution of the weighting function, except for the channel with strong trace gas absorption and channels with large observation error among 1650 channels of FY-4A GIIRS and 1682 channels of FY-4B GIIRS. The retrieved temperature and humidity profiles with GIIRS/FY-4 for the summer of 2022 were compared with radiosonde and the profiles of the GK2A AMI. The validated results of GIIRS/FY-4 were similar to the GK2A even though more channels were used. So it is needed various sensitivity tests to get more accurate temperature and humidity profiles using hyperspectral infrared sounder such as the number of channels and wavelength selection used by the algorithm. The detailed results and plans are presented at the conference. This work was funded by the Korea Meteorological Administration’s Research and Development Program “Technical Development on Weather Forecast Support and Convergence Service using Meteorological Satellites” under Grant (KMA2020-00120)
AS17-A024
Radial Distribution of Deep Convective Clouds Preceding Rapid Intensification of the Tropical Cyclones in the Western North Pacific
Chian-Yi LIU1#+, Jason Pajimola PUNAY2
1Academia Sinica, Taiwan, 2Bicol University, Philippines
This study investigates the radial distribution of deep convective clouds 24 hr prior to the rapid intensification (RI) of the tropical cyclones (TCs) in the Western North Pacific. TCs are categorized according to the 24 hr future intensity (Vmax) change (ΔVmax), as follows: non-RI (ΔVmax < 30 kt), short RI (RI-S, ΔVmax > 30 kt for less than a day), and long RI (RI-L, ΔVmax > 30 kt continuously for at least 1 day). RI-S TCs have the strongest intensity and shortest RMW within 24 hr prior to RI, whereas non-RI TCs have the weakest intensity and longest RMW within 24 hr prior to its lifetime maximum Vmax. In all categories, highest DCC percentage (DCC-P) and coldest temperature (DCC-T) are found within 3 RMW from the storm’s center. Non-RI has the lowest DCC-P and warmest DCC-T anywhere within 10 RMW, whereas RI-L has the highest DCC-P and coldest DCC-T within 2 RMW especially at the onset of RI. DCC-P starts to increase 12 hr prior to RI with sharpest 3-hr increase of 17% at 2-3 RMW in RI-L. DCC-T within RMW is always colder than that within 2-3 RMW, 9 hr prior to RI. Sharpest DCC-T difference of 3oC is found in RI-L, at least 3 hr prior to RI. Results in the study can be used to identify the TCs that are more likely to undergo prolonged RI even before the RI onset.
AS17-A025
Update of Global Maps of Alisov's Climate Classification Using an Unsupervised Machine-learning Algorithm
Ryu SHIMABUKURO1#+, Tomohiko TOMITA1, Ken-ichi FUKUI2
1Kumamoto University, Japan, 2Osaka University, Japan
Alisov's climate classification was proposed in 1954, and it focuses on the January–July changes in large-scale air mass zones and their fronts. In this study, data clustering by machine learning was applied to global reanalysis data assimilated from some satellite data to quantitatively and objectively determine air mass zones, which were then used to classify the global climate. The differences in air mass zones between two half-year seasons were used to determine climatic zones, which were then subdivided into continental or maritime climatic regions or according to east–west climatic differences. This study began by questioning whether the global climate can be divided into four air mass zones as Alisov did in the 1950s. The results showed that Alisov's four air mass zones from the 1950s were supported from a modern data-driven perspective using high-quality global reanalysis data. In addition, the clustering technique accurately captured frontal precipitation between air mass zones in the mid-and high latitudes. This study, thus, renews Alisov's climate classification for the first time in almost 70 years and applies data-driven machine learning to establish a standard for air-mass-based climate classification. This paper has been peer-reviewed once in Progress in Earth and Planetary Science (PEPS) and a revised manuscript is in preparation.
AS19-A001
Statistical Post-processing of Week 3-4 Precipitation Forecasts Over Taiwan
Joyce JUANG1#+, Hui-Ling CHANG2,3, Shih-Chun CHOU4, Chih-Yung Feng FENG5, Han-Fang LIN5, Jing-Shan HONG2
1Central Weather Administration, Taiwan, 2Central Weather Bureau, Taiwan, 3National Central University, Taiwan, 4International Integrated Systems, Inc., Taiwan, 5Manysplended Infotech Ltd, Taiwan
Numerical prediction models cannot correctly predict the extended-range (10-30-day) precipitation amount and pattern over Taiwan due to the low predictability. However, demand for extended-range precipitation forecasts by users in different sectors has grown significantly. In this study, a statistical post-processing technique combining Analog Post-processing (AP) and Probability-Matched mean (PM), called APPM, is used to perform bias correction and downscaling for week 3-4 precipitation forecasts in Taiwan. The purpose is to provide users with more accurate Quantitative Precipitation Forecasts (QPF) and more reliable Probabilistic Quantitative Precipitation Forecasts (PQPF). Previous study shows that 1-14-day post-processed precipitation forecasts using APPM, including QPF and PQPF, are promising. Here we want to confirm that the APPM method also works for the week 3-4 forecast range, which was thought to be a “predictability desert” with little forecast skill. Forecast evaluation shows that the raw ensemble is under-dispersive, while the calibrated ensemble distribution well represents the observation variability. Compared to the raw forecasts, the AP-based probabilistic forecasts have better reliability and higher skill in discrimination. Users with a much wider spectrum of cost/loss ratio can benefit more from the calibrated forecasts in decision making as compared to the raw forecast. In addition, the calibrated QPF removes most bias and displays obviously higher correlation and reduced error.
AS19-A003
Precipitation Characteristics of Tropical Cyclones During Summer Monsoon Season in the North Indian Ocean
Surya Pramod JALAKAM1+, Pay-Liam LIN1#, Wei-Yu CHANG1, Balaji Kumar SEELA1,2, Jayalakshmi JANAPATI1
1National Central University, Taiwan, 2Academia Sinica, Taiwan
This study examines the environmental conditions that influences the tropical cyclone (TC) occurrence frequency (TCOF) as well as the rain microphysics of TCs over the North Indian Ocean (NIO) during major monsoon stages (pre-monsoon, monsoon, and post-monsoon) in 2014-2021. Two regions in NIO domain are a particular focus, namely, the Arabian Sea (AS) and the Bay of Bengal (BOB). TCs that formed within the NIO domain and reached at least the tropical storm stage were selected. High TCOF is attributed to the combined presence of warm sea surface temperature and cyclonic wind or positive 850-hPa relative vorticity. Moreover, high reflectivity and heavy rainfall are found within the 50 km radius from the storm’s center. Monsoon season TC Vayu (2019) have the heaviest rainfall and highest reflectivity within the inner band region, as compared to pre-monsoon TC Fani (2019) and post-monsoon TC Kyaar (2019). The probability density functions of the rain microphysics parameters vary with the season (pre-monsoon, monsoon, and post-monsoon) and the mode of rain (total, stratiform, and convective). In all season, the breakup process is found to be dominant in total and stratiform precipitating clouds, whereas the break-up and coalescence processes are comparable in convective precipitating clouds.
AS19-A010
A Study on Microphysical Characteristics of Mei-yu Season Rainfall Over Taiwan
Jayalakshmi JANAPATI1+, Balaji Kumar SEELA1,2, Pay-Liam LIN1#
1National Central University, Taiwan, 2Academia Sinica, Taiwan
The Mei-yu season over Taiwan, mainly associated with frontal systems, is a transition period (May and June) between the winter and summer seasons. The interactions of Mei-yu season frontal systems with the complex topography of Taiwan lead to heavy precipitations across the island. The present study investigates rain and microphysical attributes of the Mei-yu season over Taiwan using Global precipitation measurement mission dual-frequency precipitation radar (GPM DPR). To analyze the regional and intra-seasonal characteristics of the Mei-yu season, May and June are segregated into pre-Mei-Yu (5/15-5/31), mid-Mei-Yu (6/1-6/15), post-Mei-Yu (6/16-6/30). There are clear distinctions in the raindrop size distributions among pre-, mid-, and post-Mei-yu seasons, with abundant large drops in the post-Mei-yu. Furthermore, raindrop size distributions also showed apparent differences among four regions (north, south, central, and eastern part) of Taiwan, with relatively bigger drops in central Taiwan. The contoured frequency by altitude diagrams of rain rate, radar reflectivity, mass-weighted mean diameter, and normalized intercept parameters are used to understand the microphysical processes responsible for the regional and intra-seasonal variations.
AS19-A012
Roles of Marine Boundary Layer Jet on Heavy Rainfall Over Taiwan During Early Summer Rainy Season
Chuan-Chi TU1#+, Chung-Hsiung SUI2, Mong-Ming LU2, Pay-Liam LIN1, Ching-Hsuan WU2
1National Central University, Taiwan, 2National Taiwan University, Taiwan
From the climatological views, 20-yr (1999-2018) June CFSR Dongsha wind vertical profiles are used to define the MBLJ days. It is found that when MBLJ occurs at Dongsha, the above 90/95-percentile extreme rainfall occurrence frequency over low land (< 1km) of western Taiwan and northern Taiwan is larger than that of NoTC days, with the peak values occur over southwestern slope of the Snow Mountains and the Central Mountain Range, and southwestern Taiwan. It is similar that the above 90/95-percentile extreme rainfall occurrence frequency over high land (> 1 km) of Taiwan is larger during MBLJ days than NoTC days, with peak values occur over southwestern slope of the Snow Mountains and the Central Mountain Range. During early summer rainy season (June) over the South China Sea, there are six CMBLJs (Coastal MBLJs) with occurrence frequency peaks (> 35 %). Their formation mechanisms are related to terrain. (1) and (2) BLJ-East and BLJ-West (East and West of Hainan Island over South China); (3) and (4) Orographic enhanced southwesterly (southwesterly flow impinging on southeastern tip of Vietnam and Taiwan); (5) Barrier jet off the northwestern Taiwan; (6) Gap wind flow through mountain gap over central eastern Vietnam.
AS19-A013
The Interdecadal Change of Relationship Between Ocean-atmospheric Thermal Environment and Typhoon Intensity in the Northwest Pacific Ocean
Chieh CHANG#+, Pay-Liam LIN
National Central University, Taiwan
Under climate change, the number of typhoons in the Northwest Pacific region will decrease and the proportion of strong typhoons will increase. In order to understand whether the interdecadal changes in the ocean and atmospheric environment affect the development of typhoon intensity. This study compares the changes in the ocean and atmospheric environment from June to November in the past two decades (1980-1999) and the current twenty years (2000-2019), and discusses the relationship between changes in the ocean and atmospheric environment and the typhoon intensity. Compared with the past, the sea surface temperature has increased by an average of 0.42°C, the ocean mixed layer depth has deepened by an average of 2.7 meters, and the ocean heat content (OHC) has increased by 9.89 kJ/cm2. The results show that under climate change, the thermal environment of the upper ocean will be more conducive to the development of typhoon intensity. In terms of atmospheric environment, the Pacific subtropical high strengthened and extended westward, and the monsoon trough also tended to retreat westward compared with the past. Under climate change, atmospheric environment has both positive and negative contributions to the development of typhoon intensity, and changes in the Pacific subtropical high, monsoon trough, and vertical wind shear will be unfavorable for the formation of typhoons. Using the observed maximum wind speed of typhoon and potential intensity to analyze the relationship between ocean and atmospheric environment and typhoon intensity. The results show that compared with the atmospheric environment, the ocean environment has a more direct relationship with typhoon intensity. Compared with sea surface temperature, OHC has a higher relationship with typhoon intensity. Moreover, the correlation between OHC and stronger typhoon is even more higher than that of weak typhoon. In conclusion, among all variables, OHC has highest correlation with typhoon intensity.
AS19-A014
Influence of COVID-19 Pandemic on Rain Microphysics Over Taiwan
Balaji Kumar SEELA1,2+, Jayalakshmi JANAPATI1, Pay-Liam LIN1#
1National Central University, Taiwan, 2Academia Sinica, Taiwan
The coronavirus disease 2019 (COVID-19) is responsible for the worldwide disorder in livelihood and enormous loss of human lives. To curtail the COVID-19 spread, the government of China imposed a lockdown over most of its provinces from 23 January to 25 March 2020. The effects of the COVID-19 lockdown on public health, transport, aviation, and meteorological parameters were well documented globally; however, its influence on rain microphysics is not fully understood. In the present study, we tried to report the distinction in precipitation microphysics, especially the raindrop size distribution between the COVID-19 lockdown (23 January to 25 March 2020) and non-lockdown (23 January to 25 March: 2015- 2029) periods over Taiwan. The raindrop size distributions between the lockdown and non-lockdown periods showed clear distinctions, with more mid- and large-size drops during the lockdown periods. Furthermore, possible microphysical differences between the lockdown and non-lockdown periods are explored using reanalysis and remote-sensing data sets.
AS19-A017
Using ISCA GCM with Dry Dynamical Core Examine to Simulate the Glacial Climate in Taiwan
Pin-Hsiu KUO1#+, Yu-Hsiang HUANG1, Po-Yu CHUANG1, Chien-Chung KE1, Kai-Chih TSENG2
1Sinotech Engineering Consultants, Inc., Taiwan, 2National Taiwan University, Taiwan
Studying the glacial climate provides opportunities to examine the change in climate systems in response to external forcing, e.g., solar radiation, greenhouse gases and the abrupt change in cryosphere. In addition, the climate is one of its external conditions which impacts the development of safety assessment scenarios, such as glacial and interglacial conditions causing sea level variations and the surface system changes. For example, the change in sea level in glacial and interglacial periods strongly determines the groundwater system and the ecosystem. The groundwater system dominates the flow rate which influences the hydrogeological condition in the near field and the potential release path from underground facility to the ecosystem in the far field. Also, the landform controls the release location of radioactive and how it will influence the biosphere. To have a better picture for the processes above and the potential risks, we leverage a GCM for simulating the glacial climate and downscale to the regional states of Taiwan. Specifically, we use ISCA, an idealized global circulation modelling framework, to simulate the glacial climate since 12,000 B.P. (last glacial maximum, LGM) until the present day. Following the standard of Held–Suarez experiment, we modulate the global energy budget through changing TOA radiation, solar zenith angle and proxy surface temperature (due to changed terrain in Taiwan and adjacent region) to mimic different climate states. Our study demonstrates the potential for safety assessment of spent nuclear fuel disposal repository based on model outputs from the idealized GCM along with the regional model downscaling.
AS19-A020
Analysis of Microphysics Process of Afternoon Thunderstorm Using Raindrop Size Distribution Retrieval from Polarimetric Radar Measurements
Chen-Hau LAN#+, Pay-Liam LIN
National Central University, Taiwan
The afternoon thunderstorm event is the common nature disaster in Taiwan area. Because of the short life cycle and high variety, it is difficult to observe the microphysics feature for whole system, especially the Drop Size Distribution (DSD), one of the fundamental microphysical parameters. Using dual-polarimetric radar to retrieve DSD is useful to obtain the variation of microphysical processes for the entire weather system. In general, the retrieved method is based on gamma distribution to reduce the degree of freedom and get the DSD parameter, such as shape parameter (µ), slope parameter (Λ), and intercept parameter (N0). However, the shape of DSD is incompatible with the gamma distribution if the specific microphysical processes are dominated. There is a new method with the moment-based operator to convert the dual-polarimetric variables to the moments of DSD which can avoid the model error. In this study, the new retrieved method is used to study DSD during different life period of the afternoon thunderstorm in Taipei area. Moreover, we try to categorize the feature of DSD under the influence of collisional coalescence, breakup, or drop settling processes. Base on the results of retrieved DSD, the evaporation and coalescence are the main microphysics processes in initial stage and mature stage respectively.
AS19-A023
Evaluation of Probabilistic Forecasts of Consecutive 5 Days Without Measurable Rainfall Over Taiwan
Shih-Chun CHOU1#+, Hui-Ling CHANG2,3, Tsun-Wen LO2, Chih-Yung Feng FENG4, Han-Fang LIN4
1International Integrated Systems, Inc., Taiwan, 2Central Weather Bureau, Taiwan, 3National Central University, Taiwan, 4Manysplended Infotech Ltd, Taiwan
In Summer, high temperatures and humidity are suitable for forage planting, but long days of sunshine are needed for hay preparation in this period to cope with the lack of fresh forage in autumn and winter over Taiwan. Therefore, the livestock industry has a demand for probabilistic forecasts of consecutive days without rainfall. However, due to the complex topographic distribution in Taiwan, rainfall forecast has high uncertainty in space and time and it is very difficult to capture the fine information from model output with low resolution. The purpose of this study is to provide users with reliable and skillful forecasts, which help users obtain more economic benefits in decision making. In this study, Analog post-processing (AP) is applied in 20-year re-forecasts of the National Centers for Environmental Prediction (NCEP) Global Ensemble Forecast System version 12 (GEFS v12) to produce calibrated and downscaled probabilistic forecasts of consecutive 5 days without measurable rainfall over Taiwan. The evaluation results show that (1) The under-dispersion of the raw forecasts is effectively improved through the AP method. (2) The probabilistic forecasts calibrated by AP method have better reliability, brier skill score and discrimination (potential usefulness) than raw forecasts. (3) The calibrated probabilistic forecasts can provide higher relative economic values compared to the raw forecasts, and it indicates the enhancement of forecast value.
AS19-A025
The Application of 3D Motion Fields in Radar Extrapolation Nowcasting: Case Study of Meiyu Front and Autumn Precipitation
Yu Chiao HSU#+, Kaoshen CHUNG, Yi-Hao ZHOU
National Central University, Taiwan
Radar echo extrapolation utilizes the observed composite reflectivity to estimate the motion fields of radar echoes and provide advection and rotation information for extrapolation. The uncertainty of motion fields is one of the major error in radar extrapolation. In addition, the weather system may have different moving directions at different heights. In this study, 3-Dimension motion fields is estimated by the entire volume scanned data and applied to MAPLE (McGill Algorithm for Precipitation nowcasting using Lagrangian Extrapolation) nowcasting system. With autumn precipitation events in the Yilan area and the Meiyu front events in Taiwan, the characteristic of 3D motion fields in space and time are analyzed. The results show that u-velocity changes a lot in both time and vertical levels in Mei-yu front event. As for autumn precipitation, the standard deviation and mean of u-velocity are similar to v-velocity. Then, the added value of 3D motion fields for the nowcasting is evaluated by continuous and categorical verification. It is found that when applying 3D motion fields in radar extrapolation nowcasting, it can capture more complete advection and rotation due to orographic effect over Taiwan area. Overall, the improvement of the nowcasting with 3D motion fields can be up to 3-h.
AS19-A027
Use Wind Profiler and Disdrometer to Analyze the Circulation and Rainfall Microphysics of Typhoons
Jun-Yan LI#+, Pay-Liam LIN, Chuan-Chi TU, Siang-Yu ZHAN, Chen-Hau LAN
National Central University, Taiwan
This study mainly discusses the synoptic environment, observed wind speed, wind direction and raindrop size distribution (DSD) when typhoon Maria (2018) and Lekima (2019) approach Taiwan. When typhoon Maria moves westward approaching northern Taiwan coastal ocean, the near surface wind speed strengthens to > 17 m/s which is observed by wind profiler at National Central University (NCU) over northwestern Taiwan. In addition, the observed wind direction using profiler gradually changes from northwesterly to southwesterly. The mass-weighted mean diameter in millimeters (Dm), observed by NCU impact-type Joss-Waldvogel disdrometer (JWD), gradually decrease to ~ 1.5 mm. On the other hand, typhoon Lekima moves northwestward from east of Taiwan. The NCU wind profiler observed near surface wind speed is smaller than 17 m/s and wind direction changes gradually from northeasterly to southwesterly. The Dm observed by NCU JWD changes irregularly as time processes. Research results show that wind speed and wind direction have impacts on DSD. Moreover, observed radar reflectivities show that the principal rainband of typhoon Maria passes northern Taiwan. At that time, the NCU JWD observations show that Dm is large (~ 2.5 mm) and the continuous rainfall > 12 hr. On the other hand, only the distant rainband of typhoon Lekima passes northern Taiwan and the observed Dm is small. The rainfall maintains less than 4 hr. Research results show that if principal rainband passes Taiwan or not influences DSD and the duration of rainfall.
AS19-A028
Analysis and Simulations of a Heavy Rainfall Event Associated with the Passage of a Shallow Front Over Northern Taiwan on 2 June 2017
Chuan-Chi TU1#+, Yi-Leng CHEN2,1, Pay-Liam LIN1, Mu-Qun HUANG1
1National Central University, Taiwan, 2University of Hawaii at Manoa, United States
From 0200 to 1000 LST 2 June 2017, the shallow, east–west-oriented mei-yu front (<1 km) cannot move over the Yang-Ming Mountains (with peaks ∼1120 m) when it first arrives. The postfrontal cold air at the surface is deflected by the Yang-Ming Mountains and moves through the Keelung River and Tamsui River valleys into the Taipei basin. The shallow northerly winds are anchored along the northern side of the Yang-Ming Mountains for 8 h. In addition, the southwesterly barrier jet with maximum winds in the 900–950-hPa layer brings in abundant moisture and converges with the northwesterly flow in the southwestern flank of the mei-yu frontal cyclone. Therefore, torrential rain (>600 mm) occurs over the northern side of the Yang-Ming Mountains. From 1100 to 1200 LST, with the gradual deepening of the postfrontal cold air, the front finally passes over the Yang-Ming Mountains and arrives at the Taipei basin, which results in an east–west-oriented rainband with the rainfall maxima over the northwestern coast and Taipei basin. From 1300 to 1400 LST, the frontal rainband continues to move southward with rainfall over the northwestern slopes of the Snow Mountains. In the prefrontal southwesterly flow, the orographic lifting of the moisture-laden low-level winds results in heavy rainfall on the southwestern slopes of the Snow Mountains and the Central Mountain Range. With the terrain of the Yang-Ming Mountains removed in the high-resolution model, the mei-yu front moves quickly southward without a rainfall maximum over the northern tip of Taiwan.
AS20-A010
Global Cloud-resolving Simulations with NICAM on the Supercomputer Fugaku
Chihiro KODAMA1#+, Hisashi YASHIRO2, Tamaki SUEMATSU3, Daisuke TAKASUKA1, Yuki TAKANO1, Ryusuke MASUNAGA1, Yohei YAMADA1, Shuhei MATSUGISHI4, Takashi ARAKAWA4, Masuo NAKANO1, Hiroaki MIURA4, Tatsuya SEIKI1, Akira NODA1, Masaki SATOH4, Tomoki OHNO5, Tomoe NASUNO1, Tomoki MIYAKAWA4
1Japan Agency for Marine-Earth Science and Technology, Japan, 2National Institute for Environmental Studies, Japan, 3RIKEN, Japan, 4The University of Tokyo, Japan, 5Meteorological Research Institute, Japan
Global cloud-resolving climate simulation is believed to promote our understandings of the atmospheric phenomena with multi-scale nature and also improve reliability of their climate projections such as tropical cyclones and cloud feedback. With this background, the Nonhydrostatic ICosahedral Atmospheric Model (NICAM) has been developed and used for more than two decades. The first realistic global cloud-resolving (here, 3.5 km mesh) simulation was published in 2007, and its extension toward climate scale is now in sight with the supercomputer Fugaku, the latest flagship machine of Japan. The value of such climate simulation is guaranteed by a series of recent model improvements to better simulate both mean state and disturbances. We are also revealing the climatological performance of the ocean-coupled version of NICAM through a series of seasonal to decadal simulations. Other important challenges include a global O(103) ensemble prediction experiments with 14 km mesh and a global 220 m experiments toward an era of global large-eddy simulation. The above challenges on the supercomputer Fugaku would be harder without an effective co-design activity with the application developers. In terms of post-processing, we recently modified our MPI-based remapping tool and confirm its applicability to a global 870 m mesh data.
AS20-A016
Mesoscale Convective Systems Simulated by a High-resolution Global Nonhydrostatic Model Over the United States and China
Ying NA1#+, Qiang FU2, L. Ruby LEUNG3, Chihiro KODAMA4, Riyu LU5
1Beijing Municipal Climate Center, China, 2University of Washington, United States, 3Pacific Northwest National Laboratory, United States, 4Japan Agency for Marine-Earth Science and Technology, Japan, 5Chinese Academy of Sciences, China
Mesoscale convective systems (MCSs) contribute a large fraction of warm-season precipitation and generate hazardous weather with substantial socio-economic impacts. Uncertainties in convection parameterizations in climate models limit our understanding of MCS characteristics and reliability of future projection. We examine MCSs simulated by the global 14-km Nonhydrostatic ICosahedral Atmospheric Model (NICAM) without cumulus parameterization against satellite observation from Global Precipitation Measurement (GPM) during 2001-2008. We focus on MCSs over the central U.S. and eastern China where MCSs are prevalent from March to August. A process-oriented tracking method incorporating both cloud and precipitation criteria is used to identify and track MCSs. About 140/100 MCSs initiate in the central U.S./eastern China per warm season and most of them initiate east of high mountains and in coastal regions. The frequency distribution of MCS lifetime is well captured by NICAM. However the simulated MCSs have stronger precipitation, smaller precipitation area, and larger cold cloud system than observed in both regions, which may be caused by weak entrainment as it is not well resolved at 14 km resolution. The simulated MCS number is also underestimated in summer. By examining the climatological and MCS large-scale environments, the significant underestimation of MCS number in summer over the central U.S. may be attributed to the large climatological dry bias in the atmosphere. For China, mean moisture in summer is well simulated but deficiency in capturing the dynamic condition related to the coastal topography for triggering convection may have contributed to underestimation of MCS even in a sufficiently moist environment.
AS20-A020
On-the-fly Data Streaming from Climate Simulations for Training the Data-driven Surrogated Models
Hisashi YASHIRO1#+, Takashi ARAKAWA2, Kengo NAKAJIMA2
1National Institute for Environmental Studies, Japan, 2The University of Tokyo, Japan
Machine learning technology has recently been applied to weather and climate simulations. Compared to atmospheric models that include various algorithms, data-driven models can reduce the amount of computation (= elapsed time) and achieve significant speedups. A data-driven model for weather forecasting is being developed using datasets such as weather reanalysis (e.g., ERA5) and multi-model intercomparison (e.g., CMIP6). However, for meteorological/climate researchers who want to elucidate processes and mechanisms, data-driven models shouldn't be used as complete black boxes. We need high-speed, on-demand "surrogate models" to imitate the physical models that algorithms are based on understanding processes and continuously developed.
We developed a coupling library h3-Open-UTIL/MP (Arakawa et al., 2022) to bridge legacy weather/climate models and modern machine learning tools. This library was initially designed to connect each component of the earth system model. We extract the necessary training data from the part of the model code written in Fortran and pass it to ML frameworks in Python on-the-fly. The proposed system enables the creation of the necessary surrogate models step-by-step using a large amount of simulation data. We will present an overview of the library and initial experimental results.
AS20-A022
Application of Deep Learning with Physical Constraints in Precipitation Nowcasting
Hongxu ZHU#+, Ji CHEN
The University of Hong Kong, Hong Kong SAR
Nowadays, extreme precipitation has brought very serious losses. How to timely and accurately forecast precipitation has become the top priority of disaster prevention. The emergence of deep learning technology has provided a new idea for the precipitation nowcasting, and achieved good results in the short forecast period, but there is still a problem that as the forecast period becomes longer, the forecast effect becomes worse. On the basis of deep learning technology, this study attempts to introduce additional physical information and simulate the future information of numerical model forecast to improve the accuracy of precipitation nowcasting. This study uses precipitation data, and two-dimensional water vapor flux data in the input and forecast stages respectively. Because there are errors in the real forecast, random errors are introduced when additional future data is added into the forecast stage. The results show that, compared with the simple application of precipitation data, the introduction of more physical information in the input stage can improve the prediction effect by 4.75%, while the introduction of predicted future physical information in the forecast stage can improve the effect by 16.69%, showing a strong application prospect.
AS22-A003
Does the Expansion of Urban Areas Aggravate Air Pollution in North China Plain (NCP)?
Qian JIANG#+, Guohui LI
Chinese Academy of Sciences, China
Urban expansion has been rapid in North China Plain (NCP) since 2000, and the metropolitan area of 2015 increased by 4.92% compared with 2000. The change in Land-Use and Land-Cover (LULC) directly affects the meteorological conditions, impacting the atmospheric pollutant concentrations. Therefore, based on the MERIS300 LULC product of 2015, this study simulates a continuous heavy pollution incident from 05 December 2015 to 02 January 2016 in NCP, to explore whether the urban expansion causes LULC changes that will worsen the atmospheric environment. The T2 increases by 0.19 ℃ while the relative humidity (RH) decreases by 1.28%. Urbanization aggravates the pollution of O3 but reduces the other four concentrations of pollutants. The concentration of PM2.5 increased significantly. In addition, the trends of PM2.5 and O3 are significantly negatively correlated in vertical distribution. Therefore, it is necessary for PM2.5 and O3 to cooperate in emission reduction.
AS22-A004
Impacts of Changes in Land Use and Land Cover Between 2001 and 2018 on Summertime O3 Formation in North China Plain and Surrounding Areas - A Case Study
Jiaoyang YU1+, Weijian ZHOU2, Guohui LI2#, Qian JIANG2, Xuexi TIE2, Suixin LIU2, Xia LI2,3, Guohui LI2, Ruonan WANG2, Lang LIU2
1Institute of Earth Environment,Chinese Academy of Sciences, China, 2Chinese Academy of Sciences, China, 3University of Chinese Academy of Sciences, China
Changes in land use and land cover (LULC) influence meteorological fields and biogenic emissions, further affecting the atmospheric chemistry and air quality. Combing the satellite measurements and WRF-Chem model simulations, we evaluate impacts of the LULC change between 2001 and 2018 on the summertime ozone (O3) formation in North China Plain and surrounding areas (NCPs). Satellite measurements have revealed that from Taihang to Yanshan Mountain, the fraction of broadleaf and needle forest coverage has increased by 5%-20% and the urban area has increased by up to 25% in the NCP. Additionally, the vegetation density has increased significantly in the NCPs except for urban areas. The LULC change generally enhances biogenic volatile compounds emissions in the NCPs, particularly over Taihang and Yanshan mountain, but the O3 variation is divergent. The maximum daily 8-hours average (MDA8) O3 concentrations are reduced by 1%-7% over Taihang and Yanshan Mountain because the raised vegetation density increases O3 dry deposition velocity to accelerate the O3 loss. The raised vegetation density enhances the evapotranspiration to decrease the near-surface temperature by 0.1 ℃ ~ 1.5 ℃, which also generates a divergence in the low-level atmosphere in the NCPs, causing secondary northerly or easterly winds in the NCP. The O3 enhancement along the coastal areas of the NCP is attributed to the perturbation of wind fields and photolysis induced by the LULC change. The divergent variation of the MDA8 O3 concentrations in the NCP is generally caused by the variations of biogenic emissions and photolysis.
AS22-A005
Understanding How Solar Farms Modify Radiation Budget and Regional Climate Based on Satellite-observation Constrained Climate Modeling
Chongxing FAN#+, Xianglei HUANG
University of Michigan, United States
Solar farms consist of arrays of solar panels to convert solar energy to electricity. Building solar farms has become an acknowledged approach to mitigate global climate change. Meanwhile, solar farm deployments change the surface radiative properties and, thus, can impact the local surface radiation budget and climate. So far, global modeling studies have primarily focused on simulating the impact caused by surface albedo changes due to large-scale solar farm deployments. Such modeling studies lack long-term observational constraints and do not consider complex atmosphere-panel-surface interactions. Using Moderate Resolution Imaging Spectroradiometers (MODIS) aboard the NASA Aqua satellite, we have quantified the change of surface spectral reflectances, spectral emissivities, and land surface temperature over six solar farms commissioned in the southwestern U.S. Results suggest a 20-25% reduction of surface reflectance over the seven MODIS shortwave bands due to the solar panel installation, leading to a ~23% decrease in the surface upward shortwave broadband flux and a ~14-18% decrease in the clear-sky reflected shortwave flux at the top of the atmosphere. Despite the uncertainty and disagreement in current surface retrieval algorithms, results show that the outgoing longwave radiances over the MODIS infrared window channels are reduced. Based on these observations, we will implement a more realistic representation of solar farms in global climate models. Specifically, we will put a translational layer in the Community Terrestrial System Model, the land component in CESM. This layer will modify the radiative and momentum fluxes given solar panels’ geometrical and radiative properties on top of the natural surfaces. The new scheme can output panel temperature to be compared to and explain in-situ and satellite observations. It will help us understand the potential impact on the climate system if an increasing number of solar farms are deployed in the future.
AS22-A006
Effects of Irrigation on the Local and Regional Climate with a New Groundwater Scheme Using Couple Model Simulations
Ren-Jie WU1#+, Min-Hui LO1, Yadu POKHREL2, Agnès DUCHARNE3
1National Taiwan University, Taiwan, 2Michigan State University, United States, 3Institut Pierre-Simon Laplace, France
The critical zone (CZ), extending from the bottom of groundwater to the top of the lower atmosphere, plays a crucial role in shaping the environment and human well-being (Brantley 2007). The CZ and climate systems are affected by various natural and human-driven processes. In this study, we utilized a modified version of CESM2 that incorporated data on groundwater, irrigation, and human water use. The groundwater scheme has also been enhanced to simulate lateral flow and aquifer pumping. To assess the impact of irrigation on climate, we conducted two experiments spanning from 1901 to 2014: one with a fixed irrigation demand in 1901, and the other with a changing irrigation demand (Sibert 2015). Our results indicate that irrigation is concentrated in India, China, and North America. In India, the irrigation effect leads to increased soil moisture, latent heat, and decreased sensible heat, resulting in a cooling effect. Rainfall is also seen to increase, particularly in the Ganges river region. Conversely, the west coast of the USA experiences contrasting feedback with decreased rainfall and soil moisture. References: Brantley SL, Goldhaber MB, Ragnarsdottir KV. (2007). Crossing disciplines and scales to understand the Critical Zone. Elements 3: 307-314. Siebert S, Kummu M, Porkka M, et al. A global data set of the extent of irrigated land from 1900 to 2005[J]. Hydrology and Earth System Sciences, 2015, 19(3): 1521-1545.
AS22-A009
The Impact of Regional and Global Groundwater Pumping on Sea Level Changes
Ren-Jie WU1+, Min-Hui LO1, Yuwen FAN2, Eun-Soon IM2#
1National Taiwan University, Taiwan, 2The Hong Kong University of Science and Technology, Hong Kong SAR
Severe groundwater depletion due to intensive irrigation has begun to emerge and has been clearly detected by satellite-based estimates in major agricultural areas, particularly the North China Plain. The effects of groundwater overexploitation are not restricted locally, but an incursion of dormant groundwater into the active hydrological cycle can critically affect the hydroclimatology of remote places and the global water budget, which eventually leads to terrestrial contributions to rising sea levels. This study explores how much groundwater depletion as a result of intensive irrigation will contribute to accelerating global sea level rise. For this, the long-term simulations with/without groundwater pumping are performed using the fully coupled configuration in Community Earth System Model (CESM). The groundwater-fed irrigation is activated in the North China Plain, the entire China, and global scale to discern different responses to the locations of the irrigation forcing. A comparative analysis of a suite of sensitivity experiments can facilitate identifying the obscure effect of groundwater pumping from the background climates. In particular, the quantification of the contributions of groundwater pumping to sea level changes will be focused, which will strengthen our understanding of the nonlinear climate processes that occur when the atmosphere, land surface, and subsurface are perturbed by groundwater pumping. [Acknowledgements]This research was supported by project GRF16309719, which was funded by the Research Grants Council (RGC) of Hong Kong.
AS22-A010
Relationship of Land-use Changes with Wildfire Risks Under Global Warming Based on CMIP6 Multi-model Projections
Yan HE+, Subin HA, Eun-Soon IM#
The Hong Kong University of Science and Technology, Hong Kong SAR
Wildfire hazards have witnessed a substantial increase in frequency, extent, and severity globally. While wildfire outbreaks and spread are strongly affected by non-climatic factors such as campfires, forest management, and monitoring capacity, there is a growing scientific consensus that increasing temperatures and resultant dryness may be responsible for a favorable environment for wildfires. A potential escalation of wildfires under global warming could result in changes to the land cover and carbon emissions, which may in turn have an impact on regional climate. However, complex climate-soil-vegetation-interacting processes leave numerous uncertainties in wildfire projections and their impacts under the acceleration of global warming. In this study, Forest Fire Danger Index (FFDI) and Fire Weather Index are calculated based on the Coupled Model Intercomparison Project (CMIP) multi-model projections in order to investigate future changes in fire weather danger under different emission pathways. The regional hotspots which are expected to face a heightened risk of fire weather are then focused on to further comprehend the wildfire and land cover feedback. (Acknowledgements: This study was supported by the Special Research Support Scheme from the Hong Kong University of Science and Technology (R9055), which was funded with the donation from the Chau Hoi Shuen Foundation.)
AS25-A003
Fast Response of East Asian Precipitation to Local and Remote Aerosol Emission Reductions During COVID-19
Weiyi WANG1+, Xiaohong LIU2#, Chenglai WU1, Guangxing LIN1, Yong WANG3, Zheng LU2, Xi ZHAO2, Linyi WEI3
1Chinese Academy of Sciences, China, 2Texas A&M University, United States, 3Tsinghua University, China
In this study, the fast response of East Asian summer precipitation to COVID-induced aerosol emission reductions is examined using the Community Earth System Model version 2.2 (CESM2.2). The emission reductions decreased aerosol optical depth and cloud cover over northern China in June 2020. The troposphere became warmer, strengthening the land-sea thermal contrast and anomalous southerly winds. The subtropical westerly jet accelerated and shifted southwards, favoring the low-level convergence, upward air motions, and subsequent condensational heating over the Yangtze River Basin (YRB). The feedback of condensational heating in return strengthened the convergence and ascent. The western North Pacific Subtropical High was intensified, which further enhanced the moisture advection and convergence over the YRB. Both the enhanced moisture convergence and ascent increased precipitation over the YRB during June 2020. Furthermore, local and remote emission reductions show different impacts on convection and moisture transport over the YRB. The emission reductions over China caused stronger convective precipitation (1.15 mm/day versus 0.63 mm/day), but weaker larger-scale precipitation (1.17 mm/day versus 2.24 mm/day) than the emission reductions outside China did.
AS25-A006
Correlation Between the Number of Patients with Allergic Rhinitis and the Concentrations of Airborne Particles in Northern Beijing, China
Sun AIZHI1#+, Sun XIAOLI2, Zhang HAIHONG2, Li XUEYIN1, Wu SHUANGSHUANG1
1University of Chinese Academy of Sciences, China, 2Beijing Huairou Hospital, China
The presence of biological (airborne pollen) and non-biological (PM2.5, PM10, O3, CO, NO2, SO2, etc.) particles in the atmosphere is associated with the incidence of adverse allergenic reactions affecting human health. Considering all the probable effects of air pollutants and airborne pollen on allergic reactions, the present study mainly examines the relationship between the daily concentrations of airborne pollen, PM2.5, PM10, O3, CO, NO2, SO2, and the number of patients with allergic rhinitis (AR) at the same time in northern Beijing, China by statistical analysis. The results showed that the daily visiting number of AR patients was positively associated with the concentration of airborne pollen, as well as the pollutants NO2 and PM10 particles, while, it was negatively associated with the concentrations of O3 and CO. Airborne pollen and part air particles (e.g., NO2, PM10) had a significant impact on the morbidity of AR patients. Thus, public health and clinical approaches are needed to anticipate and reduce the morbidity of allergic disease caused by airborne pollen and non-biological particles.
AS25-A007
Effects of Different Types of Aerosols on Deep Convective Clouds and Anvil Cirrus
Jinming ZHANG1+, Bin ZHAO2, Xiaohong LIU3#
1Chinese Academy of Sciences, China, 2Tsinghua University, China, 3Texas A&M University, United States
Deep convective clouds and associated anvils exert opposite radiative effects. The impact of different aerosol types on these two categories of clouds remains a major challenge in understanding aerosol-cloud interactions. Using 11-year satellite retrievals, we find that cloud top height (CTH) and ice cloud fraction of deep convective clouds and anvil cirrus identified by Cloud-Aerosol Lidar with Orthogonal Polarization increase with small aerosol loadings and level off or even decrease with further aerosol increase. Compared with continental aerosols, CTH affected by marine aerosols starts to decrease at smaller aerosol loadings. Moreover, cloud optical depth (COD) of deep convective clouds decreases with aerosol loadings. COD of anvil cirrus increases with increased loadings of most aerosol types but decreases with smoke aerosol. These relationships are mainly attributed to the aerosol effect rather than the meteorological effects. Our findings contribute to the development of models and better assessment of aerosol-cloud radiative forcing.
AS25-A015
The Effect of Aerosols on Surface Ozone Through Meteorology Feedbacks Over China
Yawei QU#+
Jinling Institute of Technology, China
Interactions between aerosols and gases in the atmosphere have been the focus of an increasing number of studies in recent years. Here, we focus on aerosol effects on tropospheric ozone that involve meteorological feedbacks induced by aerosol–radiation interactions. Specifically, we study the effects that involve aerosol influences on the transport of gaseous pollutants and on atmospheric moisture, both of which can impact ozone chemistry. For this purpose, we use the UK Earth System Model (UKESM1), with which we performed sensitivity simulations including and excluding the aerosol direct radiative effect (ADE) on atmospheric chemistry, and focused our analysis on an area with a high aerosol presence, namely China. By comparing the simulations, we found that ADE reduced shortwave radiation by 11 % in China and consequently led to lower turbulent kinetic energy, weaker horizontal winds and a shallower boundary layer (with a maximum of 102.28 m reduction in north China). On the one hand, the suppressed boundary layer limited the export and diffusion of pollutants and increased the concentration of CO, SO2, NO, NO2, PM2.5 and PM10 in the aerosol-rich regions. The NO/NO2 ratio generally increased and led to more ozone depletion. On the other hand, the boundary layer top acted as a barrier that trapped moisture at lower altitudes and reduced the moisture at higher altitudes (the specific humidity was reduced by 1.69 % at 1493 m on average in China). Due to reduced water vapour, fewer clouds were formed and more sunlight reached the surface, so the photochemical production of ozone increased. Under the combined effect of the two meteorology feedback methods, the annual average ozone concentration in China declined by 2.01 ppb (6.2 %), which was found to bring the model into closer agreement with surface ozone measurements from different parts of China.
AS25-A019
Spatiotemporal Variation of the Burned Area and its Relationship with Climatic Factors in Central Kazakhstan
Yongfang XU1#+, Zhaohui LIN2, Chenglai WU2
1National Meteorological Information Centre, China Meteorological Administration, China, 2Chinese Academy of Sciences, China
Central Asia is prone to wildfires, but the relationship between wildfires and climatic factors in this area is still not clear. In this study, the spatiotemporal variation in wildfire activities across Central Asia during 1997–2016 in terms of the burned area (BA) was investigated with Global Fire Emission Database version 4s (GFED4s). The relationship between BA and climatic factors in the region was also analyzed. The results reveal that more than 90% of the BA across Central Asia is located in Kazakhstan. The peak BA occurs from June to September, and remarkable interannual variation in wildfire activities occurs in western central Kazakhstan (WCKZ). At the interannual scale, the BA is negatively correlated with precipitation (correlation coefficient r = –0.66), soil moisture (r = –0.68), and relative humidity (r = –0.65), while it is positively correlated with the frequency of hot days (r = 0.37) during the burning season (from June to September). Composite analysis suggests that the years in which the BA is higher are generally associated with positive geopotential height anomalies at 500 hPa over the WCKZ region, which lead to the strengthening of the downdraft at 500 hPa and the weakening of westerlies at 850 hPa over the region. The weakened westerlies suppress the transport of water vapor from the Atlantic Ocean to the WCKZ region, resulting in decreased precipitation, soil moisture, and relative humidity in the lower atmosphere over the WCKZ region; these conditions promote an increase in BA throughout the region. Moreover, the westerly circulation index is positively correlated (r = 0.53) with precipitation anomalies and negatively correlated (r = –0.37) with BA anomalies in the WCKZ region during the burning season, which further underscores that wildfires associated with atmospheric circulation systems are becoming an increasingly important component of the relationship between climate and wildfire.
AS25-A021
Seasonal and Diurnal Variations of Carbon Dioxide and Energy Fluxes Over Three Land Cover Types of Nepal
Bharat JOSHI1#+, Yaoming MA2
1Kathmandu Centre for Research Education, CAS-TU, Nepal, 2Chinese Academy of Sciences, China
This study examines the seasonal and diurnal variations of carbon dioxide and energy fluxes over three land cover types of Nepal by using the eddy covariance method from March to November 2016. The surface energy balance closures were moderate with the values of about 56%, 61%, and 64% closure at Kirtipur, Simara, and Tarahara sites respectively. The monthly average values of net radiation flux and latent heat flux peaked in August at Kirtipur and Tarahara sites whereas in June at the Simara site respectively. The maximum monthly average measured sensible heat flux was 37 W m⁻², 43.6 W m⁻², and 36.3 W m⁻² in April for all the sites whereas soil heat flux was 5.1 W m⁻² and 2.9 W m⁻² in April for Kirtipur and Simara sites and 6.2 W m⁻² in June for the Tarahara site. The magnitude of diurnal peak of net ecosystem CO2 exchange (NEE) reached up to 11.04 μmol m⁻² s⁻¹ at Kirtipur, 15.04 μmol m⁻² s⁻¹ at Simara, and 10.44 μmol m⁻² s⁻¹ at Tarahara sites respectively. Among the three study sites, the ecosystem at the Kirtipur site was a good carbon source; the ecosystems at Simara and Tarahara sites were low and good carbon sink in the growing season. In addition, all three different land cover ecosystem were carbon source when accounted for the measurement period.
AS25-A022
A Study on the Spatial Difference of PM2.5 Concentration in Similar Synoptic Fields
DaEun CHAE1+, Soon-Hwan LEE1#, EunJi KIM2
1Pusan National University, Korea, South, 2Pusan University, Korea, South
In this study, we performed a synoptic analysis to investigate the reason for the spatial difference in PM2.5 concentration despite a similar synoptic pattern. Synoptic pressure patterns associated with high PM2.5 episodes (greater than 35 ㎍/㎥) were classified into three sub-groups related to high concentrations occurring only in Busan and Seoul metropolitan areas using K-means cluster analysis, based on the 900 hPa geopotential height of NCEP FNL data. Although the synoptic patterns of high PM2.5 episodes that occur independently in Busan and Seoul metropolitan areas were similar, there was a difference in the intensity of pressure gradient and its direction, which tends to be an important factor determining the movement time of pollutants. The spatial difference in PM2.5 concentration in the Korean Peninsula is due to the difference and direction of the atmospheric pressure gradient that develops from southwest to northeast direction.
AS25-A027
Environmental Impacts of Haze Pollution and Urbanization and Their Interactions Over the Beijing-Tianjin-Hebei City Cluster
Zilin WANG#+, Xin HUANG, Aijun DING
Nanjing University, China
With fast economic development, urban expansion and haze pollution are two main eco-environmental challenges confronting China. Though their individual impacts on urban climate and environment are investigated by multiple studies, the synthetic effect and intricate interaction of these two effects have not been fully understood. Here, based on in-situ measurements and numerical simulations at the densely populated and heavily polluted Beijing-Tianjin-Hebei (BTH) city cluster, the respective impact of aerosol and urbanization is quantitatively identified. Under polluted conditions, the aerosol radiative effect dominates with 3 oC cooling at ground surface and 1 oC warming in the upper boundary layer. In contrast, urban heat island (UHI) effect is more prominent during clean days, leading to over 1 oC warming in the lower atmosphere. Furthermore, aerosols are found to enhance UHI via confining the dispersion of anthropogenic heat and perturbing longwave radiation budget. Since the implement of China’s Clean Air Action in 2013, aerosol reduction contributes to a decreasing trend of both aerosol radiative effect and UHI intensity in BTH city cluster. The study highlights a comprehensive understanding of air pollution and urbanization as well as their interactions over megacities.
AS25-A029
The Global Environmental Measurement and Monitoring Initiative: Driving Global to Local Solutions
Mark SHIMAMOTO1#+, David LANG2, Daniel KLINGENBERG2, Janice LACHANCE1
1American Geophysical Union, United States, 2Optica, United States
The Global Environmental Measurement and Monitoring (GEMM) Initiative is an international project of Optica and the American Geophysical Union seeking to provide precise and usable environmental data for local impact. The Initiative brings together science, technology, and policy stakeholders to address critical environmental challenges and provide solutions to inform policy decisions on greenhouse gases (GHGs) and air and water quality. GEMM Centers are currently established in Scotland, Canada, New Zealand, and the United States. These Centers represent partnerships with leading institutions that are actively working toward developing or deploying new measurement technology and improved climate models. Additional Centers are under development in India and Australia with plans to expand to Asia and Africa. In addition to establishing monitoring centers worldwide, GEMM actively engages with other sectors (including industry, standards organizations, and regional or national governments) to support the incorporation or adoption of these evidence-based approaches into decision making processes. For example, Glasgow, Scotland is piloting the GEMM Urban Air Project, deploying a low-cost, real-time, ground-based network of devices that continuously monitors GHGs and air pollutants at a neighborhood scale. The sensor network in Glasgow is increasing the precision of local models that can provide the city with information to assess current policies and support future action. Here we will share the progress and outputs of the GEMM Initiative to date and highlight paths forward to grow the network.
AS26-A003
Influence of Tropical Atlantic Meridional Dipole of Sea Surface Temperature Anomalies on Antarctic Autumn Sea Ice
Xuya REN1+, Li ZHANG1#, Wenju CAI2,3, Xichen LI4, Chuan-Yang WANG1, Yishuai JIN1, Lixin WU1
1Ocean University of China, China, 2Ocean University of China and Qingdao National Laboratory for Marine Science and Technology, China, 3Commonwealth Scientific and Industrial Research Organisation, Australia, 4Chinese Academy of Sciences, China
Antarctic sea ice plays an important role in polar ecosystems and global climate, while its variability is affected by many factors. Teleconnections between the tropical and high latitudes have profound impacts on Antarctic climate changes through the stationary Rossby wave mechanism. Recent studies have connected long-term Antarctic sea ice changes to multidecadal variabilities of the tropical ocean, including the Atlantic Multidecadal Oscillation and the Interdecadal Pacific Oscillation. On interannual timescales, whether an impact exists from teleconnection of the tropical Atlantic is not clear. Here we find an impact of sea surface temperature (SST) variability of the tropical Atlantic meridional dipole mode on Antarctic sea ice that is most prominent in austral autumn. The meridional dipole SST anomalies in the tropical Atlantic force deep convection anomalies locally and over the tropical Pacific, generating stationary Rossby wave trains propagating eastward and poleward, which induce atmospheric circulation anomalies affecting sea ice. Specifically, convective anomalies over the equatorial Atlantic and Pacific are opposite-signed, accompanied by anomalous wave sources over the subtropical Southern Hemisphere. The planetary-scale atmospheric response has significant impacts on sea ice concentration anomalies in the Ross Sea, near the Antarctic Peninsula, and east of the Weddell Sea.
AS26-A009
The Delayed Impact of ENSO on Generation of the Amundsen Sea Low (ASL) Anomaly
Hyunju LEE#+, Emilia Kyung JIN
Korea Polar Research Institute, Korea, South
The El Niño-Southern Oscillation (ENSO) influences West Antarctica via atmospheric teleconnection, but it is delayed by one season because the Amundsen Sea Low (ASL) response to the ENSO has the strongest intensity in May. However, the mechanism related to the delay has not been fully discovered yet. This study investigates the formation mechanism of the ENSO-driven teleconnection in each month by examining the kinetic energy conversion (CK), total wavenumber, and wave activity flux. The perturbation induced by the ENSO gains energy from the basic state as the ENSO appears, however it does reach high latitudes only in May. Although the ENSO becomes weak in May, the developed subtropical jet makes waves to move further south, resulting in the strong ASL anomaly. Numerical experiments considering the decay of the ENSO forcing also show that the ENSO-related teleconnection is the strongest in May. The results demonstrate that the basic state is essential for the ENSO teleconnection to extend to West Antarctica.
AS29-A008
Study on the Movable Rain Belt in Lanyang Plain Under the Strong Northeast Monsoon
Jou-Ping HOU#+, Chih-Yi CHEN
National Defense University, Taiwan
In November 2020, Taiwan implemented a 5-day intensive observation experiment on the Lanyang Plain in the northeast, which we call the Yilan Experiment for Severe Rainfall (YESRain). The reason for this project is that according to the statistics of the Taiwan Central Meteorological Bureau over the years, when the northeast monsoon occurs, the Lanyang Plain often receives the most precipitation in Taiwan, and this precipitation is even higher than the Keelung area on the windward side.In order to analyze the reasons for the rainfall in the Lanyang Plain under the strong northeast monsoon, this study analyzed and simulated the moveable rain belt, rainfall time and rainfall intensity caused by the strong northeast monsoon on November 23, 2020. In addition, various observation tools such as laser wind profiler are used to analyze the relationship between the wind field and the rain belt after the interaction between the bell mouth terrain in Yilan area and the wind field at different heights, and to verify each other with the WRF numerical simulation results. It was found that the northeastern part of Taiwan was affected by the strong northeast monsoon on the 23rd, and the severe rainfall in the Yilan area not only appeared on the south windward side, but also occurred in the Lanyang Plain and the outer sea. The precipitation distribution is highly related to the direction and speed of the wind field, while The surface flux has a considerable contribution to the severe rainfall in Yilan.
AS29-A012
The Spatial and Temporal Character Analysis of Complex Terrain Rainfall in Northeastern Taiwan with Northeasterly Condition in 1961-2020
Chin-Hsiang WU, Wen-Wei TSENG, Shih-Hao SU#+
Chinese Culture University, Taiwan
There are typical spatial rainfall patterns in the northeast Taiwan area (Yi-Lan) under the northeasterly in wintertime. Such rainfall features are related to the interaction of large-scale background mean flow and complex topography. According to the climatology of rainfall, most precipitation hot spots occur on the windward side of the terrain and decrease toward the plain area. However, the difference in large-scale environmental conditions can lead the variations in spatial rainfall characteristics. By analyzing the gridded rainfall data in the Yilan area in the past 60 years, we noticed that the average rainfall has an increasing trend. The increasing trend was more significant in the southern mountain region on the windward side. The rainfall increase in winter was more extensive than in autumn and spread to the plains in coastal areas. We have also noticed that there will still be heavy rain (HR, >80mm/day) events in the Yilan area in autumn and winter when Taiwan has less rainfall. The probability of HR events has increased significantly in the past 30 years, and HR events also occurred in plain areas. On the other hand, although the probability of occurrence was low, there still were torrential rain (TR, >200mm/day) events in the mountainous areas of Yilan. The frequency and extent of occurrence of these types of extreme rainfall events have significantly increased during 2016-2020 compared with 1961-2015. According to the reanalysis data, the background large-scale circulation field has also changed in the past 60 years. The change in the background circulation led to changes in the frequency of occurrence and hot-spot locations of convection initiation, which also caused variations in the spatial distribution of rainfall.
AS29-A013
Characteristics of Mountain-wave Occurrence in the Taebaek Mountain Range Based on GK-2A
Dabin YEOM+, Jinyeong KIM, Myoung Hwan AHN#
Ewha Womans University, Korea, South
Mountain-waves, also known as Lee wave, can generate strong rotational forces or up and down air currents that can affect aircraft operations. If mountain-wave clouds exist during the calculation of atmospheric motion vectors using satellite data, the vector may become inaccurate. Therefore, it is important to analyze the atmospheric flow characteristics and generation mechanisms of mountain-wave formation. In this study, we present a satellite-based characteristics of mountain-wave events in the Taebaek Mountain range in Gangwon-do, Korea. Our analysis was based on detailed visual inspection of infrared satellite imagery in the ch13 (10.5㎛) of the GK-2A satellite during 2020-2022. Two analysts independently inspecting the same satellite images using visual inspection methods, and cross-verifying the results. If there are enough moisture in the incoming airstream, mountain-wave clouds are generated parallel to the mountain range from the ridge of mountain-wave that have the characteristics of normal waves. Therefore, we detected clouds whose positions did not change over time and observed the duration of their occurrence. Previous research used visible satellite imagery in 15-min intervals during daylight hours. This had limitations as it could not identify mountain-wave cloud that occurred or lasted at nighttime hours and the 15-min interval was too long to detect the exact duration. But, using the infrared imagery from the GK-2A satellite with 2-min intervals, we were able to overcome these limitations and achieve more accurate observations. The maximum number of mountain-wave events occurred in winter season, with the largest number in February. Conversely, the minimum number of mountain-wave events occurred in summer season, with the fewest number in July. The average duration of mountain-wave events was longest in October and shortest in June. The maximum duration is 2268-min, while the minimum is 48-min.
AS29-A018
Numerical Simulation of Boundary Layer Characteristics in the Taipei Basin and Yilan Region Under Northeast Monsoon Conditions
Pei-Di JENG#+, Jou-Ping HOU
National Defense University, Taiwan
As the latitude of the continental cold high-pressure center was higher and gradually moves eastward to the sea, the environmental wind field in northern Taiwan was mostly northeasterly or easterly winds introduced by continental high-pressure peripheral circulation. Though the distance between the Taipei Basin and the Yilan of northern Taiwan were closed, the local wind fields were quite different. In order to understand the relationship between the environmental wind field (northeast monsoon), local circulation, and complex terrain effects, this study applied the Weather Research and Forecasting Model, simulating the change of local circulation in the Taipei Basin and Yilan under the northeast monsoon on October 25 and November 26, 2022.It was found that when the wind field in the Taipei Basin is weak northeasterly, local circulation will be generated after noon due to the influence of the terrain, and the wind field will gradually change to easterly or southeasterly easterly. With such airflow characteristics, and the weather tended to be stable. When the wind field of the same environment passed through the Lanyang Plain, it was affected by the terrain effect, and the area where the wind field convergence zone was formed in the Lanyang Plain has Nimbostratus and indirect precipitation. In addition, a northwest-southeast trending wind direction convergence zone was formed in the vicinity of Sansing. As the terrain blocking and local circulation became more obvious, the wind direction gradually turned to westerly and went out to ocean. When the northeast monsoon was strong, the large-scale ambient wind field would directly change the boundary layer structure of the Taipei Basin and the Lanyang Plain. However, under the same northeast monsoon environment, there would still be obvious differences in the boundary layer wind field characteristics between the Taipei Basin and the Lanyang Plain.
AS29-A021
Preliminary Analysis of the Autumntime Heavy Rainfall Event Over Northeastern Taiwan Related to the Typhoon Nesat and Northeasterly Wind
Siang-Yu ZHAN#+, Pay-Liam LIN, Chen-Hau LAN
National Central University, Taiwan
The rain gauges over Yilan observed the heavy rainfall during 15 Oct 2022 to 17 Oct 2022 with maximum accumulated rainfall is 972.5 mm within 40 hours. During 14 Oct 2022 to 18 Oct 2022, typhoon Nesat carrying abundant moisture moved westward, passing through the sea south of Taiwan. After Nesat moved into South China Sea, the northeasterly wind enhanced. In this case, the maximum moisture flux exceeded 300 g kg-1 m s-1 near 950-hPa level. Typhoon Nesat provided abundant moisture when it was on southeast and south of Taiwan. The northeasterly wind played an important role in moisture transport after Nesat passed by Taiwan. The wind profile radar at Dongshan observed that during 1600 UTC 15 Oct to 0800 UTC 16 Oct, the low-level wind over Yilan was consistent easterly wind with the maximum wind speed ~20 m s-1. After 2000 UTC 16 Oct, the northeasterly wind advanced into Yilan, and the thickness of northeasterly wind was ~3 km. The maximum wind speed of northeasterly wind was near 1 km height, and the wind speed exceeded 20 m s-1. After 1600 UTC 17 Oct, the northeasterly wind weakened, and the westerly winds were present in the planetary boundary layer. In this case, the characteristics of drop size distribution over southern Yilan plain showed two different types. One was affect by typhoon circulation mainly (during 1200 UTC 15 Oct to 1200 UTC 16 Oct), the rain rate was stronger with larger diameter (Dm) and smaller number concentration (Nw). The other type was under northeasterly wind, and the rain rate was smaller with smaller Dm and larger Nw.
AS29-A022
Statistical Characteristics of Sounding-derived Parameters of Mesoscale Convective Systems Over South Korea
Si-Hyeon SON1+, Kwonil KIM2, Kyuhee SHIN1, Gyu Won LEE1#
1Kyungpook National University, Korea, South, 2Stony Brook University, United States
The heavy rainfall caused by Mesoscale Convective Systems (MCS) has been increasing recently. As a result, there is a growing emphasis on studying MCS. The formation and development of MCS are associated with the thermodynamic and dynamical environment, which has been mostly investigated using a numerical model. There have been limited attempts to utilize in situ rawinsonde measurements, which provide an accurate and high-resolution thermodynamic and dynamic profile, to characterize the MCS over South Korea. In this study, the sounding-derived parameters of the MCS occurring on the Korean Peninsula were presented using the data obtained in the summer of four years (2018–2021).
We classified the MCS cases into four types: convective cells (CC), mesoscale convective complex (MCC), diagonal squall line (SLD), and parallel squall line (SLD). The results show that CC was generated by thermal instability and had the largest convective potential available energy at 470.8 m2 s-2. The total Richardson number had 27.0, exhibiting a distinctly large value compared to other types, but mechanical instability was the smallest in the MCS types. MCC had a considerable convective inhibitory energy of 174.5 m2 s-2 and a large low-layer shear of 7.8 m s-1. SLD and SLP had a large vertical wind shear, with mechanical instability contributing to formation and development. Sounding-derived parameters during the formation, development, and extinction cycles of MCS suggested that the thermodynamic values gradually increased until they reached their highest values at the peak of convective system development, followed by decreasing trend during the dissipating stage. This study will present the favorable environmental condition for each MCS type to identify the key parameters in determining the MCS type and the development stage.
ACKNOWLEDGEMENT
This work was supported by the National Research Foundation of Korea grant funded by the Korea government (MSIT) (No. 2021R1A4A1032646).
AS29-A024
Radar-based Precipitation Growth and Decay Patterns During the Summer Season in South Korea
Kwonil KIM1+, Chia-Lun TSAI2, Gyu Won LEE3#
1Stony Brook University, United States, 2Chinese Culture University, Taiwan, 3Kyungpook National University, Korea, South
Improving the predictability of precipitation requires a comprehensive understanding of precipitation growth and decay (GD). Investigating the precipitation GD has mostly relied on the Eulerian approach, which examines the physical characteristics in a fixed coordinate. On the other hand, Lagrangian approach follows the precipitation system motion and enables capturing its temporal evolution. This study quantitatively retrieves radar-based GD of precipitation in South Korea in a framework of semi-Lagrangian advection. This study is followed by the investigation of the dependence of GD on the following factors: flow direction, flow speed, and relative geographical location to the topography and land–ocean boundary. The results indicate that the flow direction determines the spatial distribution of GD. The growth generally tends to occur on the windward side of the mountain range and vice versa on the lee side. The flow speed affects the intensity of GD. The study further explores the diurnal variability of the GD. Under the strong orographic forcing on the diurnal variation, unique geographical features of South Korea created interesting diurnal patterns near Seoul by land–ocean breeze circulation and on the windward side of the mountain ranges (inland) by solar heating. The GD in South Korea shows two diurnal peaks of growth: the early morning peak over the ocean and the afternoon peak in the land areas. In addition, the GD in South Korea exhibits a monthly variation with the most intense growth occurring in August.
ACKNOWLEDGMENT
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A4A1032646).
AS29-A025
Snow Cover Change in Mountain Regions
Manuel Tobias BLAU1,2#+, Pratik KAD3,4, Kyung-Ja HA2
1IBS Center for Climate Physics, Korea, South, 2Pusan National University, Korea, South, 3NORCE Norwegian Research Center, Norway, 4Bjerknes Centre of Climate Research, Norway
The mountains have been getting warmer in recent years. Special interest was put on mountain snow cover change as their environment was accounted to the cooler alpine climate zone. Snow cover is expected to reduce in response to global warming and is most evident in mountainous regions. Using available reanalysis and observation data, a decline in snow cover and snow depth was detected over the last 43 years. Our study considers the relationship between global warming and changes in snow persistence. We found that the mean global warming rate is higher than mountain warming. In addition, polar amplification and global warming do not play a significant role in snow cover changes on individual snow persistence mountains. However, local processes can influence snow cover, and long-term changes in these radiation budgets are significant drivers of the changes being observed. We conclude that regional radiation imbalance is a major contributor to the decline in snow cover. The results reveal new insights into the course of snow cover changes and their implication on the mountain climate. Understanding the impact of changing snow cover patterns is critical for informing sustainable development and preparing for the potential consequences of these changes.
AS30-A008
Analysis of Phase Change in Solid Precipitation in the Yeongdong Region of Korea: Episode Analysis of Ice Pellet and Graupel
Ji Yun KIM1+, Younggil CHOI1, Han JINHEON1, Kim TAE YEON1, Byung-Gon KIM1#, Kwonil KIM2, Gyu Won LEE3
1Gangneung-Wonju National University, Korea, South, 2Stony Brook University, United States, 3Kyungpook National University, Korea, South
The Yeongdong region (the eastern mountainous region of Korea) is frequently vulnerable to heavy snowfall. By virtue of a lot of previous efforts on the snowfall study, snowfall forecast has been significantly improved, but the phase change of solid precipitation is still hard to predict since its time scale is very short (a couple of hours) and spatial dimension is very limited, which is largely attributable to Taeback mountains and East Sea effect. For instance, two ice pellet (IP) episode (1 March 2021 & 14 March 2018) occurred along with a rapid cooling by strong cold advection during the transition period of winter to spring, when a reversed S profile of temperature was identified in both rawinsonde soundings and model reanalysis. Another episode of phase change was observed on 19 March 2022 when dramatic change of precipitation occurred in the process of rain to snow. Precipitation started on 17 March in the rain phase and persisted 3 days when the Low-pressure system passed over the Korean peninsula. Phase changed from rain to aggregate of dendrites in the morning of 19 March, and melting snow and graupel around noon in the condition of low-level cooling together with surface warming explained by thermodynamic soundings. Later, the habit of snow crystal returned to aggregates. The dramatic change of phase and habit occurred within several hours, which was observed by multi-angle snowflake camera and PARSIVEL together. The results emphasize that cold air intrusion with barrier wind plays an important role in phase change of solid precipitation such as ice pellet (or freezing rain) with a help of cold air blocking by the mountains during the transition period of winter to spring. It is necessary to examine other phase change episodes, and to understand the various roles of cold air advection along the mountains in precipitation.
AS30-A009
Observed Kinematics and Microphysics of Orographic Precipitation Associated with a Landfalling Typhoon Rainband
Tsubaki HOSOKAWA#+, Cheng-Ku YU
National Taiwan University, Taiwan
This study used Doppler radar observations, a dense rain gauge network, and disdrometers to investigate the kinematic and microphysical characteristics of orographic precipitation over Da-Tun (DT) Mountain of northern Taiwan associated with an outer rainband of Typhoon Chanthu (2021). The outer rainband, located about 100 km from the typhoon center, approached and made landfall on DT and brought a maximum rainfall of 57 mm h-1 at 0600 UTC on 12 September. A significant precipitation enhancement of 25 mm h-1 over DT was confirmed as compared to rain gauge observations over coastal and plain areas. The rainband was characterized by a broad area of strong reflectivities (> 40 dBZ) with a vertically extending feature, and its echo patterns were less organized with weak bright-band signatures. The upward motions (~1.5 m s-1) and near-zero vertical motions existed at mid-levels and lower levels, respectively. The low-level horizontal winds impinging on the DT barrier intensified with time and could reach about 20 m s-1, causing upslope lifting (~2.0 m s-1) and a corresponding local reflectivity maximum over mountain slopes. Averaged polarimetric vertical profiles calculated over the DT area indicated a significant increase in ZHH, ZDR, and KDP toward the ground below 3 km MSL, implying that the microphysical process contributing to the rainfall enhancement was primarily related to the collision-coalescence. These results were also supported by disdrometer observations, showing an increase in mass-weighted mean diameter and liquid water content during the passage of the rainband. In addition, as evident from the drop-size distribution (DSD) analysis, the observed heavy rainfall was mostly due to the presence of a numerous number concentration of midsize drops. This study demonstrated the important roles of orographic effects in modulating kinematic and microphysical characteristics and contributing to the heavy precipitation over DT.
AS30-A021
Assessment of Wind and PM2.5 Prediction with Lidar Data Assimilation in Taiwan
Fang-Yi CHENG#+, Cheng-Pei YANG, Shu-Chih YANG, Sheng-Hsiang WANG, Chia-Hua HSU, Lian-Jie WANG
National Central University, Taiwan
A lidar data assimilation system was developed based on the Weather Research and Forecasting-Local Ensemble Transform Kalman Filter (WRF-LETKF) framework coupled with the Community Multiscale Air Quality (CMAQ) model. The objective was to investigate the impact of lidar data assimilation on PBL prediction and the subsequent influence on PM2.5 prediction for a high-air-pollution event. The fine particulate matter (PM2.5) profiles retrieved from two micropulse lidar observations were assimilated in the WRF-LETKF system. Three numerical experiments, BASE (with a nudging strategy), CTRL (with an ensemble framework), and LDA (with assimilation of lidar-retrieved PM2.5 profiles), were conducted for a high-air-pollution episode. The BASE simulation overestimates the wind speed, leading to PM2.5 underestimation. The CTRL and LDA simulations can improve the wind fields and enhance the PM2.5 accumulation. With a strong error correlation between the lidar-retrieved PM2.5 concentration and the wind fields, the LDA simulation effectively corrects the wind flow from the surface to the PBL top, further adjusting the PM2.5 transport processes.
AS30-A022
Evaluation of Precipitation Type Based on Spectral Bin Model and LDAPS
Wonbae BANG1+, Kwonil KIM2, Carlin JACOB3,4, Alexander RYZHKOV3,4, Sanghun LIM1, Gyu Won LEE1#
1Kyungpook National University, Korea, South, 2Stony Brook University, United States, 3NOAA Oceanic and Atmospheric Research, United States, 4NOAA National Severe Storms Laboratory, United States
The Spectral Bin Model (SBM) is a 1-dimensional microphysics model that includes various thermodynamic processes such as melting, freezing, evaporation, and sublimation. The SBM determines precipitation type (PT) based on the simulated rainfall rate (RR), snowfall rate (SR), and input environmental profile. When the sounding observation is used as the input environmental profile, it has been shown that the PT produced by the SBM have relatively higher accuracy compared to different traditional prediction methods. The sounding, however, suffers from limited spatiotemporal resolution. The question that arises is whether the high-resolution thermodynamic fields of the operational numerical weather prediction model yield satisfactory results in determining the spatial distribution of PT. Local Data Assimilation and Prediction System (LDAPS) has been developed by the Korean Meteorological Administration (KMA) and has meteorological variables (Temperature [T], Relative humidity [RH], Pressure [P]) with a 1.5 km horizontal resolution and 70-71 layers. Prior to the joint utilization of SBM and LDAPS, we need to understand the impacts of errors in LDAPS on the performance of the SBM. The T, RH, and wet-bulb T (Tw) profiles of LDAPS will be compared with those of the sounding. Additionally, we will compare the accuracy of PT produced by the SBM when the input is either sounding or LDAPS.
Acknowledgment
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A4A1032646). This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2022-00310.
AS30-A023
The Study of Overall Physical Characteristics for Precipitation Types Using Observation Datasets
Choeng-Lyong LEE1+, Wonbae BANG1, Chia-Lun TSAI2, Ji-Hye JUNG1, Gyu Won LEE1#
1Kyungpook National University, Korea, South, 2Chinese Culture University, Taiwan
Different rainfall systems such as stratiform and convection evolve in different developing mechanisms. The characteristics study of precipitation types are important in order to understand their differences in terms of physical, dynamic, thermodynamical and micro-physical processes. Therefore, we investigated the whole properties of various rainfall systems after identifying precipitation types using newly developed classification algorithm. Categorization of precipitation types is performed using the combined algorithms composed of 1) the SL3D (storm labeling in three dimensions) and 2) classification algorithm based on feature parameters. The feature parameters are derived from VIL (vertical integrated liquid water contents) and mean reflectivity. The precipitation types are divided into 8 categories (precipitation stratiform, non-precipitation stratiform, convection, updraft, deep system, shallow system, low cloud and anvil). The vertical structures of different precipitation types are explored to compare the physical (dynamic) peculiarities using dual-polarization radar observation (WISSDOM attributes). In the addition, the generalized microphysical parameters (N0’, Dm) and the latent heat (LH) acquired directly from GPM product are also investigate to analyze the microphysical and thermodynamical characteristics respectively. The N0’ and Dm are obtained using polynomial regressions consisting of ZDR and reflectivity. The bright band appeared at 4.5~5.5 km altitude in stratiform and deep system as shown in the vertical profiles of reflectivity and ZDR. The convergence (divergence) patterns, one of WISSDOM attributes, are distinctive in lower (higher) atmospheric layers for convection and updraft regions. Both Dm and log (N0’) of updraft are relatively higher than those of stratiform. Similar to several previous studies, the mean LH profile of convection is higher than one of stratiform at all heights.
Acknowledgment: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A4A1032646).
AS32-A003
Relationship Between Strength of the Walker Circulation and Dominant Equatorial Waves
Ryoko ARAI1#+, Tamaki SUEMATSU2, Tsubasa KOHYAMA1
1Ochanomizu University, Japan, 2RIKEN, Japan
The Walker circulation is the most prominent tropical zonal circulation on a planetary scale, which is influenced by sea Surface temperature fluctuations at a time scale longer than the intraseasonal time scale. Previous studies have theoretically suggested that equatorial waves accelerate or decelerate the large-scale zonal flow of the upper troposphere in the tropics. Therefore, this study investigates the relationship between the Walker circulation and equatorial waves to clarify which equatorial waves are dominant depending on the strength of the Walker circulation. By sorting the strength of the downward branch of the Walker Circulation above the western Indian Ocean, we make composite maps of outgoing longwave radiation. The results imply that prominent equatorial waves vary depending upon the seasonality. In boreal winter when the Walker circulation is strong, some signals presumably associated with mixed Rossby-gravity waves are hinted, whereas in boreal spring when the Walker circulation is weak, Kelvin wave-like features are exhibited. Interannual variability of the aforementioned relationship will also be discussed.
AS32-A006
Contrasting the Convective Energy Recharge-discharge Cycle Between Propagating and Eastward-decaying Madden-Julian Oscillation Events
Jia-Yuh YU#, Yu-Cian TSAI+
National Central University, Taiwan
In this study, we contrast the distinct energy recharge-discharge cycle between propagating and eastward-decaying Madden-Julian Oscillation (MJO) events during the boreal winter season (November – April) from 1979 to 2018 using the moist static energy (MSE) budget and gross moist stability (GMS) plane analyses. A total of 41 MJO events are selected during the 40-year period, including 16 strong propagating (SP), 13 weak propagating (WP) and 12 eastward-decaying (ED) types of MJOs. The column-integrated MSE budget shows that, depending on the phases, vertical and horizontal advection terms take turns leading the role in discharging or recharging the MSE. In the phase when the net flux heating reaches the maximum, vertical advection plays the lead role in discharging the MSE. In the subsequent phases when the net flux heating gradually weakens, horizontal advection becomes the dominant factor in discharging the MSE. A similar situation occurs during the recharge phases to balance the net flux cooling. The SP MJO exhibits a stronger energy recharge-discharge cycle compared to the WP and ED MJOs, and the contrast significantly enlarges from the Indian Ocean to the Maritime Continent. The GMS plane analysis further reveals that four different types of convection attribute to the recharge-discharge process. During the wet phases, the top-heavy ascending motion and negative shallow convection jointly stabilize the atmosphere by exporting the MSE; while during the dry phases, the top-heavy descending motion and the positive shallow convection together destabilize the atmosphere through importing the MSE. Moreover, the recharge (discharge) phase leads the amplifying (decaying) phase by a quarter cycle is essential to maintain a robust energy recharge-discharge cycle to drive the eastward propagating MJOs.
AS32-A008
Machine Learning Parameterization of the Multi-scale Kain-Fritsch (MSKF) Convection Scheme in Grey-zone
Xing YU1+, Xiaohui ZHONG2#
1Shenzhen Institute of Artificial Intelligence and Robotics for Society, China, 2Fudan University, China
Numerical weather prediction (NWP) models are running at finer grid spacings from 1 to 10 km with increasing computational resources. However, as the grid spacing becomes comparable to the length scales of convection, known as the grey zone, the turbulent eddies in the atmospheric boundary layer are partially resolved and parameterized. Whether a convection parameterization (CP) should be used in the grey zone remains controversial. Scale-aware CP schemes are designed to improve the representation of convective transport within the grey zone. For example, the multi-scale Kain-Fritsch (MSKF) scheme introduces modifications, such as tuning convective adjustment time scale and adding linear mixing of updraft vertical velocity with grid-scale vertical velocity so that it can be implemented successfully at grid resolution as high as 2 km. However, the scale awareness is empirical and, to some extent, remains tunable. In recent years, more and more machine learning (ML) models have been applied to different domains of atmospheric sciences, including using ML models as substitutions for physical parameterizations. In this work, we proposed to use bidirectional long short-term memory (Bi-LSTM) models to replace the scale-aware MSKF CP scheme. The Weather Research and Forecast (WRF) model is used to generate training and testing data over South China at a horizontal resolution of 4 km. Torrential rainfall often occurs along the coast of South China, with the background of a frontal rain band over northern South China or the Yangtze River basin. It is called warm sector heavy rainfall and is usually associated with convective, localized, torrential, and long-lasting; thus is challenging to predict. In addition, the Bi-LSTM based CP scheme is coupled with the WRF model. The preliminary results demonstrate that the Bi-LSTM model is able to achieve good accuracy, showing the potential substitution of the MSKF scheme by ML models in grey zone.
AS32-A009
Surface Thermodynamic Gradients and ITCZ Properties in Idealised Simulations Over an Aquapatch
Maxime COLIN#+, Jan O. HAERTER
Leibniz Centre for Tropical Marine Research, Germany
Monsoons are often considered as ITCZ migrations into the land. Monsoon theories also consider the main control on precipitation properties to be the moist static energy near the surface. This study attempts to further clarify the role of surface thermodynamic gradients in determining precipitation outcome.
We run a series of idealised ITCZ simulations at 30-km grid spacing with the WRF model, in an aquapatch domain from 63S to 63N. The model is forced by a meridional contrast of surface temperature, with comprehensive physics, rotation, and symmetric boundary conditions at the North and South boundaries.
Summer solstice equilibrium simulations capture the main general circulation features and the main spatial organisation of convection. Turning on or off the convective parameterization does not impact the mean precipitation latitudinal distribution, but it does impact the eddies at smaller spatiotemporal scales, which shows a non-negligible but limited influence of convection on the summer ITCZ properties. By varying the forcing, we show that monsoon intensity follows a highly non-linear (logarithmic) relationship with surface temperature gradient, and that a finite temperature contrast is necessary to generate any cross-equatorial flow.
Simulations with an additional seasonal cycle forcing capture the abrupt and delayed monsoon onset. We also compare seasonal cycle simulations over ocean and over an idealised land to tell apart the influence of land in the delayed ITCZ migration.
AS33-A002
Real-time, Online Monitoring of Ammonia and Greenhouse Gas Emissions in Livestock with Cavity Ring-down Spectroscopy
Jinshu YAN1#+, Thomas GOTTSCHALK1, Xiaojing ZHANG2, Ryan QIN3, Magdalena E. G. HOFMANN1
1Picarro Incorporated, United States, 2Picarro Incorporated, China, 3No organization, China
Agricultural activities and processes emit greenhouse gases like CO2, CH4 and N2O, as well as NH3. While greenhouse gas emissions affect the global climate, ammonia can be a toxic pollutant to human health and biosphere environments. To reduce the impact of livestock production and fertilizer on the environment, it is vital to quantify greenhouse gases as well as ammonia emissions. However, accurate monitoring of NH3 emissions from barns, livestock, fertilization, and industry can be challenging at low levels (ppb to ppm) due to the high reactivity of ammonia and its tendency to adsorb to surfaces. Here, we present the new Picarro G2509 Cavity Ring-Down Spectroscopy (CRDS) analyzer that is optimized for continuous measurement of ammonia, while also reporting concentrations of greenhouse gases CO2, CH4 and N2O. The measurement response time of NH3 is sped up with low-reactivity internal materials and a high flow rate. The CH4 concentration range of the analyzer has been extended to 800 ppm to account for large variations in barns. The G2509 analyzer adapts the excellence of the G2508 that is commonly used to study greenhouse gas fluxes from soils by implementing key design of the G2103 analyzer which is dedicated to low level ammonia monitoring at air quality stations. Researchers studied ammonia production from livestock in cattle barns using G2103, and G2509 has been proved to be optimized for ammonia abatement measurement at dairy barns. Methane and nitrous oxide emissions have great influence on crops production and impacts of temperature and moisture on carbon and nitrogen cycling has been investigated by G2508. The effect of nitrogen and carbon modification on soil and plants has also been widely studied among Asia regions. Therefore, it is worthwhile to understand the emissions, transport, fate, and impact of greenhouse gas and ammonia pollutants via continuous gas monitoring techniques.
AS33-A004
Establishment of National Soil Nitrous Acid Emissions Network in China: Parameterization and its Application in Model
Yanan WANG1#+, Xiao FU2, Tao WANG1
1The Hong Kong Polytechnic University, Hong Kong SAR, 2Tsinghua University, China
Nitrous acid (HONO) is a key precursor of the highly reactive hydroxyl radical (OH). OH is a major oxidant to remove many gases emitted into the atmosphere and produces secondary air pollutants. Previous studies have revealed that the HONO emitted from soil is an important source of atmospheric HONO. As an agricultural country with a huge amount of fertilizer application, the effects of N fertilizers on HONO emissions have not been studied. In addition to HONO emissions introduced by fertilizers, emissions from unfertilized soils also accounted for a large part of total soil emissions due to their long duration. However, there has been limited research to quantify the HONO emissions for different soil types, thus lacking corresponding parameterization schemes to assess their impact on air quality. Here, we measured background (unfertilized) HONO and NO emission fluxes of soil samples collected from diverse soil types across China, and observed post-fertilization soil HONO emissions after applying three common fertilizers. The results show much higher emissions of HONO than those of NO, especially for samples from northern China. In terms of the fertilization effects, high HONO emissions from soils at 75%–95% WHC were founded, which contrasts with previous lower predictions at high soil moisture. Based on the results of laboratory experiments, the parameterization schemes for HONO emissions from fertilized and unfertilized soils were developed and implemented in a chemistry transport model. The inclusion of the soil HONO emissions improved simulations of atmospheric HONO and revealed a significant impact of this HONO source on air quality.
AS33-A005
Wet Deposition and Long Range Transport of Total Nitrogen and Total Organic Carbon at Two Sites in Mithila Region of Bihar (India)
Akanksha ROY+, U.C. KULSHRESTHA#
Jawaharlal Nehru University, India
Wet deposition of reactive nitrogen in the form of NH4+ and NO3- has become a major concern for scientists. The excess amount of such nitrogen species poses a threat to the environment and human health. NH3 and NO3- which primarily represent a major fraction of Total Nitrogen (TN) are contributed from the emissions from transport, agricultural and industrial sectors. N containing fertilisers, N fixation and livestock are the major sources of NH3 in the atmosphere while vehicular emissions and biomass burning contribute NO2 and further NO3- in the atmosphere. This study reports the measurements of Total Nitrogen (TN), Dissolved Organic Carbon (DOC) and Inorganic Carbon (IC) in the wet deposition at a sub-urban site (Saharsa) and a rural site (Purnia) during July 2018 - September 2019 in the Mithila region of highly enriched alluvial plains of Bihar. Total 63 samples were collected from Saharsa and 29 samples were collected from Purnia using a polypropylene bottle-fennel assembly placed at a height of 20m from the surface of ground. The concentration of TN was determined by using Shimadzu TOC-TN analyser (Shimadzu model-TOC-LCPH E200 ROHS) The volume weighted mean of TN was comparatively high at the sub-urban site (1.72 mg/L) than the rural site (1.32mg/L) suggesting a greater contribution of NOx and NH3 at the sub-urban site. The annual wet deposition fluxes of TN were calculated as 13.45 kg N ha−1 yr−1 at the sub-urban site and 5.73 kg N ha−1 yr−1 at the rural site. The airmass trajectory analysis carried out using NOAA data suggested that part from local sources, both the sites also had an influence of trans-boundary and long-range transport of air pollution. Keywords: Reactive Nitrogen, Total N, Wet deposition flux, Airmass trajectory.
AS34-A002
The Characteristics of the Equatorial Waves Caused a Record Torrential Rain Event Over Sumatra Island
Pei-Ming WU1#+, Yoshiki FUKUTOMI2, Kazuyoshi KIKUCHI3
1Japan Agency for Marine-Earth Science and Technology, Japan, 2Nagoya University, Japan, 3University of Hawaii at Manoa, United States
This study examined the cause of a record torrential rain event over the western coast of Sumatra Island in March 2016. The influence of atmospheric equatorial waves (EWs) and the characteristics of the EWs were investigated. Analysis of the Japanese 55-year Reanalysis data (JRA-55) and precipitation data from the Global Precipitation Measurement (GPM) satellite showed that the event was caused by the combined effects of Kelvin waves, equatorial Rossby waves, and westward inertio-gravity (WIG) waves. An examination of the characteristics of the EWs revealed that the Kelvin waves had longitudinal scales of ~6,000 km, with a period of ~6 days and phase speed of ~12 m s-1, which was typical of the convectively coupled Kelvin waves in this region. The WIG waves had a scale of ~2,500 km, with a period of 2.5 days and a relatively fast phase speed of 12~13 m s-1. Heavy precipitation occurred when an eastward Kelvin wave from the Indian Ocean encountered a westward inertio-gravity (WIG) over Sumatra Island. It was concluded that along with the Kelvin and equatorial Rossby waves, the WIG waves might have played a major role in the formation of the extreme precipitation event.
AS34-A006
Indian Ocean Dipole Variations During the Last Millennium in PMIP3 Simulations
Charan Teja TEJAVATH1#+, Karumuri ASHOK2, Supriyo CHAKRABORTY3, Sreenivas PENTAKOTA2
1National Center for Earth Science Studies, India, 2University of Hyderabad, India, 3Indian Institute of Tropical Meteorology, India
Proxy-observational studies, and a sole model study, suggest that the Indian Ocean Dipole (IOD), an important global climate driver, exhibited multi-scale temporal variability during the Last Millennium (LM; CE 0851-1849, with relatively high number of strong positive IOD events during the Little Ice Age (LIA; CE 1550-1749), and strong negative IOD events during the Medieval Warm Period (MWP; CE 1000-1199). Using nine model simulations from the PMIP3, we study the IOD variability during the Last Millennium after due validation of the simulated current day (CE 1850-2005) IOD variability. Majority of the models simulate relatively higher number of positive IOD events during the MWP, and negative IOD events in the LIA, commensurate with simulated background conditions. However, higher number of strong positive IOD events are simulated relative to the negative IODs during the LIA, in agreement with proxy-observations, apparently owing to increased coupled feedback during positive IODs.
AS35-A011
A Regime-based Investigation Into the Errors of CMIP6 Simulated Cloud Radiative Effects Using Satellite Observations
Hao MIAO1#+, Xiaocong WANG2, Yimin LIU2, Guoxiong WU2
1Nanjing Joint Institute for Atmospheric Sciences, China, 2Chinese Academy of Sciences, China
Using a variety of CloudSat/CALIPSO products, this study synergistically examines the performance of clouds and their radiative effects (CRE) for models participating in CMIP6. Results show virtually all models overestimate the net cooling effect of clouds, which is caused by the overestimation of shortwave CRE and the underestimation of longwave CRE. By dividing clouds into regimes jointly sorted by cloud water path and cloud cover, we found models commonly underestimate the relative frequency of occurrence (RFO) for clouds that are geometrically thick, and the bias of RFO is dominant over that of within-regime CRE in an error decomposition of total CRE. This results in underestimations of CRE in geometrically thick clouds, which are partially offset by overestimations in the remaining cloud regimes, leading to the globally averaged CRE being less biased. The consideration of regime-based CRE gives important information that could be used for correction of cloud parameterization in models.
AS35-A014
Exploring Aerosol-cloud Interactions Over Eastern China and its Adjacent Ocean Using the WRF-SBM-MOSAIC Model
Jianqi ZHAO1+, Xiaoyan MA1#, Johannes QUAAS2, Hailing JIA2
1Nanjing University of Information Science & Technology, China, 2Leipzig University, Germany
This study aims to explore aerosol-cloud interaction over eastern China (EC) and its adjacent ocean (ECO) in boreal winter by coupling of a spectral-bin cloud microphysics (SBM) and an online aerosol module (MOSAIC) in WRF-Chem, with the support of four-dimensional data assimilation. The evaluation shows that assimilation has an overall positive impact on the simulation, and the coupling system reproduces the satellite-retrieved cloud parameters while exhibiting significantly improved simulation ability compared to the original SBM scheme as well as the bulk microphysical and MOSAIC coupling system. Differences in aerosol composition and physical processes lead to clear discrepancies in the aerosol-cloud interactions of EC and ECO during the simulation period. In EC with the gradual increase of aerosol number concentration (Naero), cloud droplet number concentration (Nd) first increases then decreases and fluctuates around 800 cm-3, while Nd in ECO increases faster initially, but soon its activation is suppressed by aerosol hygroscopicity and high activation threshold of numerous small particles, and almost no additional cloud droplets are produced. In terms of rapid adjustments, more bursty atmospheric supersaturation and lack of subsequent water cause cloud liquid water content (CLWC) in EC to increase explosively with Nd when there are few cloud droplets, but only maintains a low increase rate with further increasing Nd. ECO exhibits a fast increase in CLWC with Nd at high proportion of naturally emitted large aerosol particles, but its CLWC increase gradually stagnates as Nd increases. For non-precipitating clouds with less water content, CLWC in EC increases slowly with Nd, but can maintain a stable trend. While ECO, which relies mainly on large scale water and temperature variations to reach supersaturation, the increase in Nd leads to a decrease in CLWC.
AS35-A015
Effect of Aerosols in an Extreme-rain Producing Convective Storm in Eastern China
Yuxing YUN1#+, Da-Lin ZHANG2, Jinfang YIN1, Wenhua GAO1, Chun ZHAO3, Jiawei LI4, Hongli LIU1, Jianping GUO1
1Chinese Academy of Meteorological Sciences, China, 2University of Maryland, United States, 3University of Science and Technology of China, China, 4Chinese Academy of Sciences, China
We use the WRF-Chem model to simulate the extreme precipitation event in Guangzhou on May 7th, 2017, and investigate the effect of aerosols during this event. It is found that under polluted conditions, more latent heat is released through the condensational growth of droplets, which increases the updraft speed and ice-phase hydrometers. Precipitation is increased due to the melting of snow and graupel. However, in the latter stages of MCS development, the instantaneous extreme rain rate is lower in the polluted experiment, while the accumulated precipitation is higher. This study explains the evolution of extreme precipitation in the MCS and how the different microphysics, dynamics, and thermodynamics processes contribute to the evolution.
AS35-A016
Cloud Removal Using Machine Learning for BRDF/albedo Retrievals in the Arctic
Vikas HANASOGE NATARAJA#+
University of Colorado Boulder, United States
Since the late 1990s, NASA’s Earth Observing System constellation of satellites has provided continuous, long-term observations of atmospheric and surface processes on Earth, which has advanced our knowledge of our planet’s radiation budget. Imagery-based surface properties such as surface albedo and Bidirectional Reflectance Distribution Function (BRDF) are generated as an operational product using cloud-cleared, multi-angle surface reflectances from multiple overpasses over several days. The BRDF is central to imagery-based cloud and aerosol retrievals, while the surface albedo is a fundamental Earth energy budget parameter. Yet, this product is currently unavailable at higher latitudes such as the Arctic where (1) the low contrast between clouds and snow/ice poses a challenge for cloud detection and clearing, and (2) ice floes are drifting over time, which is currently not accounted for in the operational products. As a result, there is a significant gap in our understanding of the Arctic radiation budget and the influence of melt events on the ice-albedo feedback, cloud-radiative effects, etc. To address this gap, we propose the development of a BRDF/albedo product for moving sea ice floes and snow called the Sea Ice Floe and Snow Albedo Tracker (SIF-SAT). By leveraging multi-overpass, multi-angular satellite data, SIF-SAT will retrieve BRDF and albedo under low contrast and moving surface conditions. We combine existing cloud masks with machine learning (ML) models to produce cloud-cleared scenes in the Arctic. These scenes are then fed to a segmentation algorithm to identify individual moving sea ice floes and their reflectances are tracked over time to obtain BRDF and albedo. The focus of this presentation will be on the cloud-clearing model which has implications for radiation science in polar regions. SIF-SAT will enhance our capabilities in the challenging conditions of the Arctic and enable more accurate estimates of the cloud-radiative effect and ice-albedo feedback.
AS35-A017
Determined Characteristics of Particulate Matters and Precipitations and the Impacts of Wet Removal Based on Long-term Surface Measurements in Seoul, Korea
Suji HAN1+, Junshik UM1#, Seoung Soo LEE2, ChangHoon JUNG3
1Pusan National University, Korea, South, 2Earth System Science Interdisciplinary Center, United States, 3Kyungin Women's University, Korea, South
Precipitation is an important process that modulates the water cycle and also contributes to controlling the concentration of atmospheric pollutants by washing out particulate matters (PMs) (i.e., wet removal or below-cloud scavenging). Previous studies showed the spatial and temporal characteristics of the concentration of PMs or precipitation. Although several studies attempted to quantify the impact of the wet-removal mechanism on the concentration of surface PMs, they were limited to a few events-based case studies. Thus, this study determined the impact of the wet-removal mechanism on the concentration of surface PMs (i.e., PM2.5 and PM10) by many events (over 10 thousand) based on long-term measurements in Seoul, Korea. Twenty-one years (2001-2021) surface measurements of precipitation and PM10 made at 25 stations in Seoul were used, while PM2.5 measurements were only available for seven years (2015-2021). All measurements were made with a one-hour resolution. The statistical analyses (i.e., monthly, seasonal, and yearly averages) for the variability of precipitation and mass concentrations of PMs were performed. The precipitation events were identified when the threshold time interval (i.e., 2 hours) existed between hourly precipitation data. The characteristics of precipitation events were quantified based on the precipitation duration, precipitation intensity, and accumulated amount of precipitation. The variation in PM concentrations during the precipitation events and the rate of wet removal were calculated as functions of the characteristics of precipitation events. The optimal duration, intensity, and accumulated amount of precipitation for the maximum wet removal were determined and the influence of precipitation properties on the wet-removal mechanism was also evaluated.
AS35-A018
Impact of Aerosols on Clouds with Different Weather Patterns in Northwestern Pacific
Keying LI1#+, Tianyi FAN1, Chuanfeng ZHAO2, Xin YANG1
1Beijing Normal University, China, 2Peking University, China
Aerosols are one of the crucial factors that impact regional and global climate. Dust and anthropogenic aerosol from East Asia contribute to the change of radiative fluxes and climate by modifying the cloud regimes in Northwestern Pacific (NWP). In this study, we attempt to find the role of aerosols on cloud properties in various cloud regimes under the control of differential weather systems in NWP. Using the cloud products obtained from Himawari-8 satellite combined with the Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals for comparison, we classified the cloud regimes in NWP using the "k-means" clustering algorithm. The characters of the cloud regimes are described by analyzing their spatio-temporal distributions of the occurrences. Using the principal component analysis in T mode (T-PCA) for classifying weather patterns, we discussed the association between cloud formation and weather systems. We assessed the sensitivity of cloud properties to the perturbation of aerosols of different types in the main cloud regimes under the dominant weather patterns. This study helps to improve our understanding of the aerosol-cloud-radiation interactions in NWP.
AS35-A020
Vertical Distribution and Source Apportionment of Aerosol in Typical Areas of China
Dongyang PU#+, Hao WU
Chengdu University of Information Technology, China
The typical areas of aerosol distribution in China include three mega-city regions (BTH, YRD, PRD) and the background area of the Qinghai-Tibet Plateau. To compare the distribution and source of aerosol particles in these regions which have large differences in natural conditions and population density. In this research, we observed the aerosol particle number concentration continuously from July 2017 to September 2020. The conclusions can be deduced: 1. Aerosol-sounding observations conducted on the Qinghai-Tibet Plateau from June to September 2020 found that there is a high concentration level ( > 165 #/cm3) of fine particle layer (N < 300nm) near 15km in the upper air. 2. Due to the Northwest airflow in the upper air on the Qinghai-Tibet Plateau in September, the concentration is the lowest value of the four times observations. 3. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model is used to analyze the 96h back trajectories of particles on the Qinghai-Tibet Plateau. It is found that in the late summer and early autumn, there are 29.3%~57.3% of the aerosols were transported from the southwest of the observation site. 4. According to the analysis of aerosol trajectories and particle size distribution characteristics, the source of aerosol in megacities is mainly attributable to human activities. We first investigate the aerosol differences under the influence of natural atmospheric conditions and human activities. But there are some deficiencies in the current research: further research is needed on the vertical distribution of aerosols and their climatic effects in megacities and the remote background region.
AS35-A022
Contrasting Influence of Nitrogen Oxides on the Cloud Condensation Nuclei Activity of Monoterpene-derived Secondary Organic Aerosol in Daytime and Nighttime Oxidation
Chenqi ZHANG1+, Yindong GUO1, Hongru SHEN1, Hao LUO1, Iida PULLINEN2, Sebastian SCHMITT2, Mingjin WANG3, Hendrik FUCHS2, Astrid KIENDLER-SCHARR2, Andreas WAHNER2, Thomas MENTEL2, Defeng ZHAO1#
1Fudan University, China, 2Forschungszentrum Jülich, Germany, 3Hefei University of Technology, China
Anthropogenic nitrogen oxides may influence the cloud condensation nuclei (CCN) activity of biogenic secondary organic aerosols (SOA) in both daytime photooxidation and nighttime NO3 oxidation, which has significant implications for the climatic impact of SOA. However, the influence remains unclear. In this study, we investigated the CCN activity of monoterpene-derived SOA formed from photo-oxidation of two monoterpenes (α-pinene and limonene) at different NOx levels, as well as BSOA generated in the dark by reaction of limonene and NO3. And we use the hygroscopicity parameter κ to characterize the CCN activity of MT-SOA. In daytime OH oxidation, NOx had little influences on the CCN activity of MT-SOA. In nighttime NO3 oxidation, MT-SOA had much lower CCN activity compared with those formed via OH or O3 oxidation. And we report the κ of monoterpene-derived organic nitrates (0.029-0.052) for the first time to our knowledge, which may be used to improve model simulations of CCN concentrations.
AS35-A023
Air Pollution Characteristics and Source Tracking in Megacity Chengdu Based on Cruise Observation
Hancheng HU#+
Chengdu University of Information Technology, China
This study researched the distribution characteristics of air pollution in Shuangliu District, Chengdu, the main persistent aerosol pollutants and ozone concentration in Shuangliu District from December 21, 2022 to February 5, 2023 were comprehensively analyzed by using the results of cruse observations. The sources of pollutants were analyzed by combining the meteorological data provided by Shuangliu Meteorological administration The Portable Optical Particle Profiler (POPS), ozone detector, hand-held weather station and wind lidar were integrated on the vehicle and made the cruse observation around the Baihe Park site, Yong'an Primary School site and their surrounding area in Shuangliu District. Three-dimensional spatial and temporal changes of areosol size distribution and ozone were obtained. The results showed that the average daily total particle number concentration was 5000~18000 #/m3/15000~18000#/m3 in haze weather, 5000~8000#/m3 after rain, respectively. coarse particles (272nm~473nm) accounted for 45%~60% in the whole observation period. Results showed that pollution was more likely to form the north wind, mainly due to industrial emissions and human activities in the upper wind direction region. The total particle number concentration decreased by 3%~8% when arriving at the park, but increased significantly, around 3%~10%, when passing by construction sites and driving close to trucks. Results of the cruse observation provide a scientific basis for particle and ozone control in Shuangliu District, which is conducive to the subsequent targeted pollution prevention and control of relevant departments, and can also provide reference for other urban areas.
AS35-A032
North Atlantic Oscillation Associated Variation in Cloud Phase and Cloud Radiative Forcing Over the Greenland Ice Sheet
Haotian ZHANG1#+, Chuanfeng ZHAO2, Jie YANG1, Yikun YANG2
1Beijing Normal University, China, 2Peking University, China
The Greenland ice sheet (GrIS) has been losing mass at an accelerating rate in recent decades due to warming, and understanding the underlying mechanisms, such as the impacts of clouds, is essential. Using space-borne data, this study investigates the spatial distribution of ice clouds and liquid-bearing clouds (LBCs) over the GrIS and their surface radiative forcing effects during summer daytime from 2006 to 2017, along with their characteristics during the North Atlantic Oscillation (NAO) events. Due to the perennial high-albedo surface, both ice and LBCs have a less important shortwave radiative cooling effect than in other environments. Based on the spatial variation pattern of clouds with the NAO index, the GrIS can be divided into three regions: the western, central, and eastern GrIS. During the positive NAO, the westerly wind strengthens in the western region, which causes the fraction of both ice clouds and LBCs to increase, and the cloud radiative effect at the surface increases by 2.07 W/m2; the temperature decreases in the central region, the fraction of ice clouds increases, the fraction of LBCs decreases, and the net radiative forcing is −2.05 W/m2; and sinking airflow is generated in the eastern region, both ice cloud and LBCs decrease, and the net cloud radiative effect at the surface is −1.34 W/m2. The spatial and temporal variations in clouds in different phases over the GrIS are closely related to the NAO, and the response of clouds to changes in the atmospheric circulation field during the NAO varies in different regions of the GrIS.
AS35-A033
Impacts of Dust on the Cloud Formation Time Over the Badain Jaran Desert Region
Xin ZHAO1+, Chuanfeng ZHAO2#, Yikun YANG2, Yulei CHI1, Yue SUN1
1Beijing Normal University, China, 2Peking University, China
To explore the influence of dust aerosols on cloud formation via radiative effect, this study takes the Badain Jaran desert area as the research area where cloud formation is less disturbed by human activities compared to other densely populated areas such as the North China Plain. We first identify 469 cases with cloud formation after 03:00 UTC (11:00 Beijing time) by manual method (checking every cloud image to identify the temporal evolution of clouds) using the high temporal resolution Himawari-8 satellite data. Through the analysis of individual cases, we find that the cloud formation time is mainly dependent on the low tropospheric stability (LTS) when the total precipitable water (TPW) is less than about 18.5 kg/m2, and greatly affected by the TPW when it is larger than 18.5 kg/m2. Dust aerosols near the ground absorb shortwave solar radiation, making the atmospheric structure unstable (decreased LTS) and conducive to cloud formation. Statistically, for every 0.1 increase in AOD, the cloud formation time is advanced about 138 minutes. Further analysis shows that dust aerosols actually inhibit the formation of convective clouds through microphysical processes when the TPW is small, while promote the formation of convective clouds through radiative processes when the TPW is large. This study reveals the effects of dust aerosols on the time of cloud formation along with the underlying mechanisms, which provides observational support for improving cloud parameterization in numerical models.
AS36-A001
Future Changes in Monsoon Precipitation Over the Indonesian Region Obtained by Bias Correction and Statistical Downscaling Methods: Including the Differences Between CMIP5 and CMIP6 GCMs
Motoki NISHIMORI1#+, Michihiko TONOUCHI2, Hiroshi SATODA2, Kadarsah 3, Agus SABANA HADI3, Dodo GUNAWAN3
1National Agriculture and Food Research Organization, Japan, 2Japan Meteorological Business Support Center, Japan, 3Indonesian Agency for Meteorology, Climatology and Geophysics, Indonesia
The climate of Indonesia located under the equator is predominated by the monsoon of both the northern and southern hemispheres. Climate changes in Indonesia would affect agricultural production and the whole economy. The future climate changes were projected by GCM simulation, but the geographical features of Indonesia are very complicated. Therefore, various downscaling methods involving RCM simulations are necessary to find detailed changes in the monsoon climate over Indonesia. Our previous work showed that precipitation over Java Island generally decreased in the onset season and increased in the dry season deduced by the bias-corrected CMIP5-GCMs output. In this study, CMIP6-GCMs are added as boundary conditions, the time scale of the analysis is varied from daily, 10-day, and monthly scales, and a downscaling method is also applied to account for the monsoonal atmospheric field and its changes. Preliminary analysis results using two CMIP6 GCMs (MIROC6 and MRI-ESM2) indicated that in each model group (MIROC5:MIROC6 and MRI-CGCM3: MRI-ESM2-0) seasonal monsoonal precipitation shift and wind system of historical runs (1995-2014) is similar. That is the onset of the monsoon is relatively postponed and the total amount of precipitation is small in MRI-ESM2-0. Future precipitation changes in the onset season would also decrease in MRI-ESM2-0. Multiple bias correction and statistical-downscaling methods are also being applied to the CMIP6 dataset to further analyze the seasonality and model dependence of future changes in precipitation in Indonesia.
AS36-A002
Climate Change Projection Over Mainland Southeast Asia and the Lancang-Mekong River Basin Based on a Set of RegCM4 Simulations
Yuanhai FU1#+, Xuejie GAO1, Ying XU2, Filippo GIORGI3
1Chinese Academy of Sciences, China, 2National Climate Center, China, 3The Abdus Salam International Centre for Theoretical Physics, Italy
We investigate the projected climate change over Mainland Southeast Asia (also known as the Indochina Peninsula) and the Lancang-Mekong River basin, a region with complex topography and unique weather and climate systems, but limited availability of published high-resolution regional climate model (RCM) studies. The study is based on an unprecedented ensemble of 21st century projections with the RegCM4 RCM driven by five different general circulation models (GCMs) at a grid spacing of 25 km under the representative concentration pathways RCP4.5 and RCP8.5. We focus on mean temperature and precipitation in the dry season November–March (NDJFM), the wet season May–September (MJJAS), and the whole year. Intercomparison between the RegCM4 simulations with the driving GCMs is provided to illustrate the added value of the RegCM4 experiments. RegCM4 reproduces greater and more realistic spatial detail of the present day temperature and precipitation distribution compared to the driving GCMs, but some biases are found, such as an overestimation of precipitation over high topography regions. The spatial pattern of biases shows some consistencies across the GCMs and, for NDJFM the RegCM4, although weak correlation is found between the GCM and nested RegCM4 biases. A generally lower warming is projected in the future by the RegCM4 in different seasons and the whole year. For precipitation, while prevailing increases are found in the GCM projections, large areas of decrease occur in the RegCM ones, in particular during the wet season, possibly due to the more detailed topographical representation. The change patterns of precipitation show consistencies across the GCMs and the RegCM4, especially in MJJAS. The projected changes of extreme indices indicate a general decrease/increase of extreme cold/warm events. Drought events are projected to be more frequent over southwestern, while a general increase of heavy rain events prevails over most parts of the region.
AS36-A006
Projection of Future Photovoltaic Potential in South Korea Based on High-resolution SSP Scenarios
Jinuk KIM#+, Do-Hyun KIM, Tae-Jun KIM, Young-Hwa BYUN
National Institute of Meteorological Sciences, Korea, South
Policies for carbon neutrality are being implemented around the world. To achieve carbon neutrality, renewable energy production must be increased. Solar energy is a representative renewable energy and is known to be significantly affected by climate change. In this study, based on high-resolution climate change scenarios, future Photovoltaics potential (PVpot) changes in South Korea was predicted. According to the four SSP scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5), at the late 21st century, surface down-welling shortwave radiation, which has a major impact on PVpot, is expected to increase (by about +0.8 ~ +3.6 W/m2) compared to the present. However, PVpot is expected to increase (by about +1.3%) in the low-emissions scenario (SSP1-2.6) and decrease (by about -0.7 ~ -2.0%) in the high-emissions scenarios (SSP3-7.0, SSP5-8.5) at the end of the 21st century compared to the present. Because as the temperature increases significantly, the temperature of the solar cell panels increase, and performance ratio of PVpot decreases. Seasonally, PVpot is expected to increase (by about +2.3 ~ +4.0%) in summer and decrease (by about -3.6 ~ -7.1%) in winter.
AS36-A012
Assessing the Feasibility of Wind Energy Development in South Asia Through an Analysis of Land Surface Wind Speed Trends Using Reanalysis and In Situ Observations
Muhammad Abid KHAN#+, Koji DAIRAKU, Saurabh KELKAR
University of Tsukuba, Japan
Reanalysis metadata are a critical resource for examining meteorological changes and evaluating wind energy potential. Observed wind speed studies reveal a global decline in land surface wind speed since the 1960s, known as terrestrial stilling, but with a reversal around 2010. The extent to which the decline in trend and turning point of land surface wind speed has been captured by reanalysis products is currently unknown. To address the research gap, a systematic evaluation of climatological winds and trends in three reanalysis products (ERA5, JRA-55, and NCEP/NCAR) was conducted by comparing 10-m wind speed time series from grid cells with observational data from 32 in situ meteorological stations for the period 1973-2005. To measure the accuracy of the reanalysis products, a range of statistical metrics were employed, including standard deviation (STD), mean absolute error (MAE), percent bias (PBIAS), correlation coefficient (R), M-K test and Sens slope estimation. Based on the evaluation of climatological winds, JRA55 proves to be the most accurate reanalysis product compared to the observations. Despite this, considerable deviations were discovered between the simulated wind speeds and the observations. The JRA55 reanalysis product was found to reflect changes observed in the Subcontinent, with the NCEP/NCAR product following closely behind. The JRA55 reanalysis demonstrated agreement with observations m/s, with a high R of 0.93, a PBIAS of -10.70, and a low MAE of 0.28. further, NCEP/NCAR showed lower standard deviation levels of 0.54. The Subcontinent's wind energy industry is experiencing growth and expansion, with opportunities for the development of offshore wind farms and the expansion of existing land wind farms. This study aims to highlight the discrepancy between observed and simulated land surface wind speeds, emphasizing the importance of careful use of reanalysis products for wind assessment and forecasting in the subcontinent region.
AS36-A013
Dynamical Downscaling Over Southeast Asia: Perfect vs Imperfect Boundary Conditions
Venkatraman PRASANNA1#+, Xin Rong CHUA2, Chen CHEN2, Gerald LIM1, Sandeep SAHANY2, Muhammad Eeqmal HASSIM2,1, Aurel MOISE2
1Meteorological Service Singapore, Singapore, 2Centre for Climate Research Singapore, Singapore
In dynamical downscaling, biases in lateral boundary conditions obtained from coarser models can play an important role in the dynamically downscaled simulations. As a part of Singapore’s Third National Climate Change Study, dynamical downscaling has been carried out over Southeast Asia (SEA; 79E-160E;16S-24N), using the Singapore Regional Climate Model (SINGV-RCM; an adapted version of Singapore’s operational NWP model) using perfect boundary conditions (ERA-5) and four CMIP6 GCM (ACCESS, EC-Earth, MPI & UKESM) at 8km horizontal resolution. The SINGV-RCM is forced with ERA-5 reanalyses data for a 36-year period (1979-2014) at 8km resolution over SEA with regular update of the sea surface temperature at 6-hr interval; further, a similar simulation is carried out using four CMIP6 GCM (ACCESS, EC-Earth, MPI & UKESM) forcing data for a 60-year period (1955-2014). The last 20-year period (1995-2014) from the five simulations with reliable high-resolution observation (merged in-situ and satellite) is selected for evaluation. Rainfall characteristics including the diurnal cycle and extremes from the five simulations evaluated against observations will be presented.
AS36-A021
Future Projections of Bioclimatic Indicators on Korean Peninsula Using SSP Scenarios
Chansung OH1+, Jina HUR2, Sera JO2, Seung Beom SEO3, Jaepil CHO1#
1Integrated Watershed Management Institute, Korea, South, 2National Institute of Agricultural Sciences, Korea, South, 3University of Seoul, Korea, South
Climate change due to global warming affects various areas such as agriculture, ecosystem, water resources, and forest in different ways. Climate change scenarios have been used as a scientific basis for establishing climate change adaptation policies to preemptively minimize damage by assessing future impacts due to climate change. In this study, downscaled data with 1 km resolution for the Korean Peninsula was produced using the SSP (Shared Socioeconomic Pathways) scenario used in the AR6 report. In order to consider the uncertainty of the future outlook that may occur depending on the selection of a specific Global Climate Model (GCM) when using only a single climate model, a total of 18 climate model data were used to analyze the future projections based on multiple model ensemble (MME). First, the downscaled data was produced using a non-parametric quartile mapping (QM) technique that does not use a distribution formula in estimating the bias between the observed data and the GCM data. Then, the characteristics of future fluctuations of 19 bioclimatic indicators were analyzed. The future projections were analyzed for each of the 30-year periods of the near-future (2011-2040), mid-future (2041-2070), and far-future (2071-2100) compared to the past 30-year period (1981-2010). In the case of annual precipitation and annual average temperature, the rate of change tended to be higher during the far-future compared to the near-future period. Within the same future period, SSP5-8.5 showed the highest change rate while SSP1-2.6 showed the lowest change rate. In the case of bioclimatic indicators, bio4 and bio15, which represent seasonal variability in precipitation and temperature, also showed the highest increase rates in the far-future and SSP5-8.5 scenarios.
AS36-A024
Domain Shift Problem in Deep Learning-based Downscaling Models: Daily Precipitation
Hae Soo JUNG+, Sungmin O, Seon Ki PARK#
Ewha Womans University, Korea, South
Extreme precipitation events, causing tremendous socio-economic damage, are among the most disastrous phenomena. Nowadays, many studies address the localization of extreme events and their intensification throughout climate change; thus, the demand for high-resolution and reliable atmospheric data is increasing. Downscaling of model output is one of the efficient ways to produce detailed data, and it simultaneously draws attempts to increase its efficiency through deep learning (DL) methods. Although DL methods have the advantages of less demand for long-term observation data and lower calculation costs, there are limitations, too: in particular, the performance of downscaling through DL methods heavily depends on the amount of the training data set. The enormous amount of atmospheric data is suitable for training DL-based downscaling models; however, high-quality atmospheric data with appropriate resolution and reliability are restricted. Considering various features of regional climate, investigation of the domain-shifting problem is crucial in order to apply the learned DL model to other regions excluded from the training data. Accordingly, the performance differences among the DL-based downscaling models, trained with differently distributed data, are investigated by comparing the cross-applying results. In addition, the DL model with integrated learning data is also investigated. This study lays the foundation for the smooth application of a deep-learning model for detailed daily precipitation.
AS37-A003
Cold Surge Impacts on the South China Sea Boundary Layer
Chung-Hsiung SUI#+, Kuan-Yun WANG, Mong-Ming LU
National Taiwan University, Taiwan
Episodic cold surges associated with the East Asia (EA) winter monsoon can penetrate deep into the South China Sea (SCS), enhance consequent tropical rainfall, and further strengthen the EA meridional overturning circulation (MOC). These cold surges can promote strong surface fluxes and lead to a deeper marine planetary boundary layer (PBL). In this study, we use high resolution radiosonde data of temperature and humidity profiles over Dongsha Island to identify the PBL height (PBLH), mixed layer height (MLH), cloud base, and cloud top for the period of December-January-February (DJF) from 2010 to 2020. We combined ERA-5 meteorological variables and surface fluxes, MERRA-2 cloud radiation data, and radiosonde-derived PBL parameters to perform an energy budget analysis and turbulent diagnostics from the mixed-layer model from Nicholls (1984). Here we show a strong turbulent flux convergence of both heat and moisture over the SCS during cold surges, which leads to a lifting of the MLH to ~1.0 km and PBLH to ~2.0 km and associated cloud development over Dongsha Island (116.69E, 20.70N). The cold and dry horizontal advection is balanced by this vertical turbulent flux convergence in the energy budget. Overall, at post-surge the PBL is stable but mixed layer is unstable, which contrasts with the pre-surge stage that features a stable mixed layer and a conditionally unstable PBL.
AS37-A004
Intraseasonal Oscillations and the Subseasonal Peak Rainfall Event in the Eastern Philippines During 2017/18 Winter and S2S Prediction Evaluation
Wayne Yuan-huai TSAI#+, Mong-Ming LU, Yin-Min CHO, Chung-Hsiung SUI
National Taiwan University, Taiwan
From December 13, 2017 to January 2, 2018, three tropical cyclones (TCs) successively made landfall in Mindanao and led to the most extreme wintertime (December - February) subseasonal peak rainfall event (SPRE) over the eastern Philippines (9°-14°N, 122°-127°E). The SPRE is defined by the maximum 15-day accumulated rainfall amount within the region during a time span of 90 days. The 15-day rainfall extremes over the eastern Philippines are associated with the environmental low-level cyclonic vorticity, which can be contributed to La Niña condition, Madden-Julian Oscillation (MJO), and equatorial Rossby (ER) waves. During the 15-day period of 2017/18 winter SPRE, the cyclonic vorticity phase of the westward propagation ER waves from the North Pacific occurred twice and the second episode occurred simultaneously with an MJO from the Indian Ocean across the Maritime Continent to the western Pacific. Favored by anomalous cyclonic vorticity and humidity produced by La Niña and MJO, the two ER waves enhanced and resulted in two TCs and led to the extreme SPRE. Based on the hindcast data in the S2S database, the 2017/18 SPRE and associated MJO and ER waves in ECMWF and NCEP models show skillful forecasts up to the extended range (11-day lead). For the SPRE in 2017/18 winter, the ECMWF model performs better than the model’s hindcast skill, whereas the NCEP model performs worse. The model with a better representation of SPRE timing and intensity has smaller phase and amplitude biases of tropical waves in the medium (5-10-day lead) and extended ranges. The forecast skill of the MJO and ER linked to ENSO phases will be discussed. The analysis procedure proposed in this study can be applied to monitor and predict the SPREs and their associated large-scale drivers in other regions.
AS37-A005
The Impact of Scale-aware Parameterization on the Next-generation Global Prediction System in Taiwan for Front Predictions
Chang-Hung LIN1#+, Ming-Jen YANG2, Ling-Feng HSIAO1, Jen-Her CHEN1
1Central Weather Bureau, Taiwan, 2National Taiwan University, Taiwan
In order to improve the precipitation forecast of the next-generation Global Prediction System with the Finite-Volume Cubed-Sphere Dynamical Core in Taiwan’s Central Weather Bureau (TFV3), this study modified the convective processes in New Simplified Arakawa-Schubert scheme (NSAS) based on the methodology of scale-aware parameterization developed in Kwon and Hong (2017) and investigated its impacts on a front event, which propagated across Taiwan and produced heavy rainfall in late May of 2020. Results show that the modified scale-aware parameterization has significantly improved the intensity and the spatial distribution of frontal precipitation forecasts due to the proper definition of convective updraft fraction. However, the synoptic-scale features perform a larger warm bias with the modified scale-aware parameterization. To understand the reason for the warm bias, the vertical profiles of zonal mean temperature, cloud cover and the heating rate from each physical parameterization were investigated to reduce the biases. The result of verification shows that the occurrence of a larger warm bias in low-to-mid levels is attributed to the decrease in subgrid-scale water vapor consumption by the deep convection process and the increase in grid-scale condensation heating resulting from the consumption of environmental instability by microphysical processes. Therefore, further modification of the scale-aware capability of convective cloud water detrainment is proposed to reduce the heating from microphysical processes and result in a better overall performance for the medium-range weather forecasts.
AS37-A006
Weather and Climate Analysis of Tropical Cyclone Genesis Clustering Events in Western North Pacific Extended-weather Analysis
Jian-Hung LIAO1#+, Chung-Hsiung SUI1, Jau-Ming CHEN2, Hsu-Feng TENG3
1National Taiwan University, Taiwan, 2National Kaohsiung University of Science and Technology, Taiwan, 3National Center for Atmospheric Research, United States
In the boreal warm season (May-September), tropical cyclone genesis (TCG) is active in the West North Pacific (WNP) region. TCG occurs in WNP monsoon trough that are influenced by active weather and climate oscillations. In addition, TCG tends to cluster in a short period and absent at other times. In this study, we investigate the weather (or extended weather) disturbances responsible for the extreme TCG clustering and how the weather disturbances are influenced by low-frequency climate oscillations including QBWO, ISO, and ENSO. We first calculate the maximum number of TCG per 10 days in each JJASO season from 1990 to 2019 to determine the most extreme TCG cases. Four cases with 5 TCGs in 10-days are selected. By analyzing the extended weather disturbances of the four periods, we find that 15 out of 20 TCs occurred in positive vorticity phase of QBWO and 4 TCs formed following a preexisting mature TC suggesting Rossby wave energy dispersion within positive vorticity region of QBWO. A further analysis of the climate conditions shows that, three of the four extreme TCG-clustering events occurred in late July-August during La Niña developing summer with inactive BSISO, while the other occurred in El Niño developing July with active BSISO in WNP.
AS37-A007
Characteristics of the South Asian High Intraseasonal Variability and its Influence on the Precipitation Over the South China Sea and Surrounding Region
Po-Chia CHEN#+, Mong-Ming LU
National Taiwan University, Taiwan
The South Asian High (SAH) is the most important upper tropospheric summer system over Asia as its intensity and shape variation are closely linked with Indian and East Asian summer monsoon rainfall variability. However, SAH intraseasonal variability and its impacts on precipitation has not been fully untangled. In this study, we used the empirical orthogonal function (EOF) to analyze the 200-hPa daily geopotential height (GPH) during June-August in 1979-2020 over 20°-120°E, 10°-50°N. The first three leading modes are all significant at the intraseasonal time-scale. The regression patterns of 200hPa wind and GPH in the Northern Hemisphere show the first two modes are associated with different types of midlatitude circumglobal teleconnection patterns. The spatial pattern of EOF3 shows a negative sign over the Black Sea, a positive sign over the North China and another negative sign over the north of Indian and Indochina Peninsula, suggesting a possible north-south shift of the SAH center location. The regressed precipitation on PC3 shows negative correlation with the precipitation over the Yangtze River and Japan and positive correlation with the precipitation over the South China Sea (SCS) and Philippine. The PV tendency equation is used to diagnose how the SAH variations influence the precipitation anomalies over the SCS. The extreme cases in June and July 1998 are selected for detailed analysis. In June and July 1998, the SAH was extended eastward to the South China, and the Western Pacific subtropical high (WPSH) was extended westward to the SCS. Due to the anomalous descending motions associated with the WPSH, the rainfall over the SCS (110°–120°E, 10°–20°N) was the fewest during 1979-2020. The process of how the upper tropospheric circulation affects the lower tropospheric circulation and precipitation will be discussed.
AS37-A013
Sub-seasonal Rainfall Extremes and Extended-range Forecast Opportunity in Taiwan and the Philippines Revealed in the S2S Database
Mong-Ming LU1#+, Wayne Yuan-huai TSAI1, Sheng-Fong HUANG1, Yin-Min CHO1, Chung-Hsiung SUI1, Ana Liza Solmoro SOLIS2, Meng-Shih CHEN3
1National Taiwan University, Taiwan, 2Philippine Atmospheric, Geophysical and Astronomical Services Administration, Philippines, 3Central Weather Bureau, Taiwan
During the first half month of April 2022 the Philippines experienced severe disasters associated with the weak but deadly tropical storm Megi that caused 214 deaths and the sinking of two ships. This prompted us to investigate the predictability of the springtime Philippine sub-seasonal scale rainfall extremes and to identify the forecast opportunity in the S2S prediction database. The results suggest that ENSO is the most influential climate driver for the sub-seasonal scale springtime (February-April) rainfall variability in the Philippines. MJO and equatorial Rossby (ER) waves can modulate the sub-seasonal rainfall extremes. The 15-day accumulated rainfall amount of the sub-seasonal peak rainfall events (SPRE) is higher during a La Niña spring, so is the occurrence probability of a extremely wet event. The wet extremes can be enhanced by strong MJO or equatorial Rossby (ER). For the April 2022 case, the S2S multi-model ensemble mean (MMEM) can successfully predict the extremity of the SPRE at least 10 days ahead, although both MJO and ER were weak during the occurrence period of the deadly SPRE. Thus the successful prediction was interpreted as a result of the predictability rooted in the rainfall variability driven by the La Niña event. Since the S2S prediction is built on the ENSO foundation, it is proposed to include the SPRE in the real-time extended-range forecast items to exploit the benefits of S2S prediction and applications.
AS38-A008
LSM Perturbation Experiment and Impact on Afternoon Thunderstorm Ensemble Forecast
YuTze HONG#+, Jen-Ping CHEN
National Taiwan University, Taiwan
This study examines the sensibility of WRF simulation to different options of the Noah land surface model (LSM) with multiple parameterization options (Noah-MP) and the feasibility of using LSM perturbation for the ensemble forecast of afternoon thunderstorms over the Taiwan area. Five land surface processes in Noah-MP were tested, and the results showed that the sensitivity of the processes in descending order are: surface layer exchange coefficient, canopy radiation geometry, canopy stomatal resistance, surface resistance to evaporation, and soil moisture factor for stomatal resistance. Based on the sensitivity analysis, we designed an LSM perturbation method for WRF based ensemble system by applying various Noah-MP configurations and land surface initial conditions. Two ensemble experiments, each with 24 members, were conducted to assess the impact of LSM perturbation on afternoon thunderstorm rainfall simulations. One applied perturbation on initial atmospheric conditions and the other with additional LSM perturbations. The preliminary results from the 24-hour forecast of five afternoon thunderstorm cases showed that the LSM perturbation scheme could effectively improve the spread-skill performance of atmospheric variables near the surface, and the probability match of precipitation is also improved. Further details of the probability forecast analysis will be presented.
AS38-A010
Evaluation of Multi-scale Sampling Performance of Ensemble Perturbations in the NCEP Global Ensemble Forecast System and Mechanisms
Li MA#+, Jie FENG
Fudan University, China
The key to ensemble forecasting is the generation of initial ensemble perturbations which is aimed at sampling the probability distribution of analysis errors. Most studies assess the prediction skill of the ensemble forecasts, which, however, is simply an indirect reflection of the quality of initial ensemble conditions. This study will evaluate the performance of ensemble perturbations in sampling forecast errors at multiple spatial scales through the entire forecast lead times. The projection of ensemble perturbations onto forecast errors at multi-scales and different lead times is the major metric used in this study. The variations of the projection as a function of spatial scale, lead time, and vertical levels will be carefully investigated. How these perturbation-error relationships can influence the control and perturbed forecast skill will also be explored.
AS38-A019
Spatiotemporal Estimation of Analysis Errors in the Operational Global Data Assimilation System at the China Meteorological Administration Using a Modified Safe Method
Jie FENG#+
Fudan University, China
Quantification of the uncertainties in initial analyses against the real atmosphere (“reality”) provides a fundamental reference for the evaluation and development of operational data assimilation (DA) systems. Due to the unknown reality, most existing methods for analysis error estimation use reanalysis datasets or observations as a proxy for reality, which are empirical, nonobjective, and biased. Unlike these methods, our study adopted a modified Statistical Analysis and Forecast Error (SAFE) estimation method to objectively and directly quantify spatiotemporal errors in analyses compared to reality based on unbiased assumptions. In the present study, the SAFE method was first applied to estimate the annual variation and spatial distribution of analysis errors in the Global Forecast System of Global/Regional Assimilation and PrEdiction System (GRAPES_GFS) at the China Meteorological Administration since the beginning of its operational implementation (i.e., 2016–2021). Qualitative comparison to analysis error estimations in previous studies showed that SAFE can provide more reasonable spatial-mean analysis error profiles than can the estimation with the ERA-5 reanalysis as a reference (the approach hereafter called “ERAv”). Moreover, ERAv overestimates (underestimates) the spatial-mean analysis error below (above) ~500 hPa compared to SAFE because it neglects the uncertainties inherent in reanalysis. Overall, the SAFE estimation reveals that relative reductions of about 12.5%, 29%, and 24.5% were achieved for the spatial-mean analysis errors of wind, temperature, and geopotential height, respectively, in the GRAPES_GFS throughout the six-year study period. These results can largely be attributed to the DA scheme being upgraded from 3D-Var to 4D-Var. SAFE can also provide more reasonable and accurate point-wise analysis errors than ERAv can.
AS38-A023
Status and Plan of Ensemble Forecast System in Korea Meteorological Administration
Eun-Jung KIM#+, Sora PARK, Hyun-Cheol SHIN, Jong Im PARK, Jong-Chul HA, Young-Cheol KWON
Korea Meteorological Administration, Korea, South
The ensemble forecast system based on the Korea Integrated Model (KIM), which is developed for Korea’s own numerical weather prediction (NWP) model, has been in operation at Korean Meteorological Administration (KMA) since October 2021. KMA ensemble forecast system consists of 50 perturbation members (25 members for long-range forecast) and 1 control simulation. Four-dimensional LETKF (Local Ensemble Transform Kalman Filter) with additive and RTPS inflation scheme is used to make initial perturbation.
Evaluation of forecast scores shows that our operational ensemble forecast system is generally more skillful compared to the deterministic simulation as forecast time is longer. We also tested ensemble forecast with increased ensemble size which is planned to be operated this summer. Increased ensemble size produces better representation of atmospheric fields especially in higher latitudes. Details of results from operational ensemble system and impacts of increased ensemble size will be discussed with introducing a brief overview of our ensemble forecast system and development plan in future.
AS39-A005
The Tables of Aerosol Optics (TAO) Project
Greg SCHUSTER1#+, Bastiaan VAN DIEDENHOVEN2, Richard MOORE3, Elisabeth ANDREWS4,5, Joshua SCHWARZ4, Masanori SAITO6, Ping YANG6, Snorre STAMNES3, Benjamin JOHNSON7, Arlindo DA SILVA8, Mian CHIN8
1NASA Langley Research Center, United States, 2SRON Netherlands Institute for Space Studies, Netherlands, 3National Aeronautics and Space Administration, United States, 4National Oceanic and Atmospheric Administration, United States, 5University of Colorado Boulder, United States, 6Texas A&M University, United States, 7University Corporation for Atmospheric Research, United States, 8NASA Goddard Space Flight Center, United States
The Table of Aerosol Optics (TAO) project is a community repository of optics computations (extinction, absorption, single-scatter albedo, lidar ratio, etc) that are useful for global models and remote sensing applications. TAO expands upon historical efforts (e.g., Hess et al., 1998) by building an open database that uses recent measurements and new computational techniques for non-spherical particles. The ‘open’ aspect of TAO is important, since the size distributions, hygroscopicities, refractive indices, and morphological recommendations of today will undoubtedly yield to different values in the future; the open framework of TAO allows scientists to keep adding new computations to the database as the science evolves.
TAO is meant to be a community repository where specialists can put their computations for other scientists to use. So for instance, some groups are advancing new techniques that can accommodate complex fractal aggregates of black carbon, other groups are working on realistic irregular shapes for mineral dust, and different groups are updating the hygroscopicity of various aerosol types using new techniques. The TAO database gives these scientists a place to distribute their products. As TAO grows, modelers and remote sensing specialists will look to TAO as a place to find a wide variety of choices for testing. Meanwhile, global modelers can also use TAO to lobby for new tables that accommodate their needs.
Eventually, TAO will provide mass extinction coefficients, mass absorption coefficients, lidar ratios, etc., at popular remote sensing and global modeling wavelengths (0.25-40 µm) for all pertinent species (sulfate, sea salt, BC, OC, BrC, dust, etc.). Multiple tables may be created for each species or type to account for the multiple valid size distributions, hygroscopicities, complex refractive indices, and shapes that can be found in the literature.
Hess, M., P. Koepke, and I. Schult (1998), Bull. Am. Meteorol. Soc.
AS39-A010
Comparison of GOCI 6km-AOD and 500m-AOD in Estimating Ground-level PM2.5 Concentrations Over Metropolitan City Busan in South Korea Using Machine Learning Method
Juhee LEE1+, Yeseul CHO1, Seoyoung LEE1, Kwang-min MYUNG2, Young-doh KIM3, Ja-Ho KOO1#
1Yonsei University, Korea, South, 2Data Intelligence Lab, Inc., Korea, South, 3Weatheri, Inc., Korea, South
Since the airborne particulate matter (PM) affects the respiratory health of human significantly, the monitoring of its quantity in a high spatial resolution is requested. But it is not an easy task because the installation of qualified surface monitoring station is expensive. The satellite monitoring can be an alternative but its spatial resolution is still sparse. To get over these limitations, we can estimate of PM2.5 (PM having a diameter < 2.5 μm) based on the machine-learning system with the consideration of both surface in-situ and satellite measurements. In this study, we develop the PM2.5 estimation platform based on the random forest (RF) algorithm using the Geostationary Ocean Color Imager (GOCI) 6km-AOD products and 500m-AOD products with surface PM2.5 measured by KT company cheap sensor networks from June 2018 to December 2019. Our target region is Busan in South Korea. In addition to AOD, we use other 11 physical values such as the meteorological parameters (e.g., temperature, wind speed, etc.) from the ERA5 reanalysis dataset of the European Centre for Medium-Range Weather Forecasts. For the validation, we use two methods, which are the 10-fold cross validation and the comparison with the surface PM2.5 observed by the Korean government monitoring system. In conclusion, the quality of our RF-based PM estimation is reliable, showing R2 = 0.45 for the case to use AOD at 6 x 6 km2, and R2 = 0.71 for the case to use AOD at 0.5 x 0.5 km2, showing that the usage of high resolution AOD enables us to have better PM2.5 estimation. Our study clearly shows the advantage of high AOD resolution for the regional air quality monitoring, related to the machine-learning system. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2020R1C1C1011624).
AS39-A011
Comparison of PM2.5 Concentration Between the Surface Measurement and MERRA-2 Reanalysis Dataset in South Korea
Dayeong LEE, Juhee LEE+, Ja-Ho KOO#
Yonsei University, Korea, South
Reanalysis data prepared by the aerosol data assimilation was developed to compensate for the limitations of ground observation data, satellite data, and modeling. Since The second version of Modern-Era Retrospective analysis for Research and Applications (MERRA-2) reanalysis data including AOD assimilation provides the gridded PM2.5 for the long-term period, it can be widely used for the analysis of regional aerosol pollution. To do this work, the validation of MERRA-2 PM2.5 is strongly required. In South Korea, however, this evaluation research is still insufficient. In this study, from 2015 to 2021, the PM2.5 concentration of MERRA-2 is evaluated by surface PM2.5 observed by the Korean national intensive monitoring sites (NIMSs). We found some difference between the MERRA-2 and NIMSs PM2.5. First, the monthly variation is different. While NIMSs PM2.5 is highest in winter but lowest in summer, MERRA-2 PM2.5 shows a maximum in April and minimum in winter. In other words, MERRA-2 PM2.5 is largely overestimated in summer but underestimated in winter generally. Among the components used in the MERRA-2 PM2.5, sulfate, black carbon, dust, and sea salt is overestimated but organic carbon is underestimated compared to the aerosol component of NIMSs. However, total MERRA-2 PM2.5 is much lower than the PM2.5 of NIMSs, especially in the urban area. This feature seems due to the absence of nitrate component in the MERRA-2 data. When we consider the amount of nitrate based on the empirical estimation suggested by some previous studies, we confirm that the quantity of MERRA-2 PM2.5 becomes much closer to the NIMSs PM2.5. Understanding of MERRA-2 PM2.5 characteristics for each region is still required in future studies. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2020R1C1C1011624).
AS39-A013
Satellite-assisted Particulate Matter (SAPM) for the Models, In Situ, and Remote Sensing of Aerosols (MIRA) Working Group
Travis TOTH1#+, Greg SCHUSTER1, Alexander MATUS2, Mian CHIN2, Meloë KACENELENBOGEN3, Edward NOWOTTNICK2, Melanie FOLLETTE-COOK2
1NASA Langley Research Center, United States, 2NASA Goddard Space Flight Center, United States, 3NASA Ames Research Center, United States
Particulate matter with aerodynamic diameters smaller than 2.5 microns (PM2.5) is a major contributor to air pollution worldwide and negatively impacts human health. For the past few decades, researchers have developed a variety of approaches to estimate surface PM2.5 from satellite observations, due to a lack of ground station in situ PM2.5 coverage in many regions globally. A well-documented technique is the use of column-integrated aerosol optical depth (AOD) retrievals from passive sensors to obtain surface PM2.5 proxies. Active sensors, like lidars, provide aerosol vertical distribution, and thus can be used to scale column AOD to the surface to improve the proxies. In addition to this synergistic passive/active sensor approach, near-surface aerosol extinction retrievals from lidar measurements can also be used independently to derive PM2.5 concentrations. Furthermore, researchers have used aerosol models to convert satellite AOD to surface PM2.5, and data assimilation methods can be employed to improve forecast PM2.5 model simulations. Benefits of space-based/model-assisted PM2.5 estimates include helping to approximate PM2.5 concentration levels for those areas lacking in situ ground station coverage, providing nighttime characterization of air quality, and assessing spatial and temporal variations of PM2.5 pollution on both regional and global scales. For this Models, In situ, and Remote sensing of Aerosols (MIRA) Topic, we aim to provide inter-comparisons of various methods and techniques for retrieving surface PM2.5 assisted by satellite remote sensors, global aerosol models, and in situ aerosol measurements. These comprehensive PM2.5 estimates can be useful for current and future efforts in air quality research, modeling, forecasting, and applications. We seek international in situ datasets (e.g., mass scattering/absorption coefficients and aerosol hygroscopic properties) for various aerosol species to develop more robust PM2.5 estimates. We also seek international ground-based in situ PM2.5 datasets to validate the PM2.5 concentration estimates.
AS39-A017
Characteristics of PM2.5 at the Ground-level and Top of POSCO Tower, Incheon, Korea
Yongjoo CHOI1#+, Jeonghoon LEE2, Saehee LIM3, Jiyoung KIM4, Yong Jae LIM4, Jongbyeok JUN1, Giyeol LEE1, Ilkwon NAM4, Sumin KIM4
1Hankuk University of Foreign Studies, Korea, South, 2Korea University of Technology and Education, Korea, South, 3Chungnam National University, Korea, South, 4National Institute of Environmental Research, Korea, South
Since 2019, the Korean government has been implementing a PM2.5 Seasonal Management Policy during wintertime (December to March in next year) to protect public health by mitigating the frequency and concentration of high PM2.5 events. To investigate the difference in the chemical composition of PM2.5 at ground-level and mid-upper planetary boundary layer (PBL) during winter (January to March) in 2023, 24-h PM2.5 filter samplings were conducted at both the ground-level and top of POSCO Tower (37.39°, 126.64°, 305 m a.s.l) along with co-located air quality monitoring stations (AQMS) which provide hourly concentrations of PM10, PM2.5, CO, NO2, SO2, and O3. POSCO Tower is the sixth-highest building in Korea thus the Korean first AQMS at high altitude was established in 2023. Using low volume sampler (16.7 LPM), filter samples were collected on the 47 mm Teflon filter (PTFE Filter with support ring, 2.0 μm; MTL) for mass and trace metal concentration, and the quartz fiber filter (Tissuquartz™ 2500QAT-UP, Pall Pallflex) for water-soluble ions and carbonaceous concentration. The concentration of chemical components (ion, trace metal, and carbon) will be analyzed to utilize the input into a positive matrix factorization (PMF) analysis, which will allow us to identify different emission sources between two vertical sites by combining the backward trajectory analysis. We believe that this study will be contributed to not only identifying the major emission sources at two vertical sites, but also enhancing the accuracy of vertical PM2.5 prediction in the chemical transport models and remote sensing techniques.
AS39-A021
Retrieval of Aerosol Optical Depth from Geostationary Environment Monitoring Spectrometer (GEMS) Using Machine Learning Approaches
Hyunyoung CHOI+, Seohui PARK, Jungho IM#, Audrieauna BEATTY
Ulsan National Institute of Science and Technology, Korea, South
Aerosols are not only air pollutants that are linked to human health, but also an important factor in understanding earth radiation and climate change. As aerosol optical depth (AOD) is a quantitative estimate of aerosols present in the atmosphere, it can be used as a proxy of air quality. Satellite-based AOD is mainly obtained through a radiative transfer model, demanding heavy computation and having uncertainties. To overcome these challenges, this study proposed a machine learning-based model to estimate hourly AOD from the Geostationary Environment Monitoring Spectrometer (GEMS) over Asia-Pacific regions (5°S–45°N, 75°E–145°E). The model was constructed using light gradient boosting machine, which has top-of-atmosphere (TOA) reflectance and observation angle data obtained by the GEMS satellite sensor, meteorological variables from the numerical model, and other auxiliary variables as independent variables. Aerosol Robotic Network (AERONET)-measured AOD data were used as a dependent variable. The proposed model was evaluated using random, spatial, and temporal 10-fold cross-validation (CV) with in-situ data to examine the spatiotemporal generalization possibility. The results of the random and temporal CV showed good agreement with the reference data, resulting in the determination of coefficient (R2) of 0.87–0.90 and root-mean-square-error (RMSE) of 0.11–0.12. However, the spatial CV results yielded slightly lower accuracy, with an R2 of 0.67 and an RMSE of 0.19. This explains the low spatial transferability in areas where ground stations are rare or in low-latitude regions where input data for modeling are often unavailable due to frequent precipitation. However, it is confirmed that the accuracy of AOD estimation is comparable to or even better than the operational GEMS AOD product. Our results indicate that the proposed approach using TOA reflectance data from geostationary satellite sensors has great potential for estimating AOD for operational purposes.
AS40-A004
Impact of the Pacific Sector Sea Ice Loss on the Sudden Stratospheric Warming Characteristics
Yvan ORSOLINI1#+, Jiarong ZHANG2, Varavut LIMPASUVAN2, Jinro UKITA3
1Norwegian Institute for Air Research, Norway, 2Coastal Carolina University, United States, 3Niigata University, Japan
The extent of sea ice coverage over the Arctic Ocean has dramatically declined over the past few decades. The anomalously warm Arctic surface associated with the Arctic sea ice loss has been linked to the mid-latitude surface cooling in the subsequent boreal winter. Several studies have suggested that this linkage could involve the wintertime stratospheric circulation by enhancing the upward planetary wave (PW) activity and weakening the polar vortex. Temperature anomalies induced by the vortex weakening could subsequently descend into the troposphere on time scales of weeks to months, potentially leading to cold air outbreaks (CAOs) over the continents. Cases studies based on observations or model simulations even suggested that the enhanced wave flux could be strong enough to cause the demise of the polar vortex associated with the sudden stratospheric warming (SSW) phenomenon. The atmospheric response to Arctic sea ice loss remains however a subject of much debate. Most studies have focused on the sea ice retreat in the Barents-Kara Seas and its troposphere-stratosphere influence. Here [1], we investigate the impact of large sea ice loss over the Chukchi-Bering Seas on the sudden stratospheric warming (SSW) phenomenon during the easterly phase of the Quasi-Biennial Oscillation through idealized large-ensemble experiments based on a global atmospheric model with a well-resolved stratosphere. Although culminating in autumn, the prescribed sea ice loss induces a near-surface warming that persists into winter and deepens as the SSW develops. The resulting temperature contrasts foster a deep cyclonic circulation over the North Pacific, which elicits a strong upward wavenumber-2 activity into the stratosphere, reinforcing the climatological planetary wave pattern. While not affecting the SSW occurrence frequency, the amplified wave forcing in the stratosphere significantly increases the SSW duration and intensity, enhancing cold air outbreaks over the continents afterward.
AS40-A006
Contributions of Equatorial Planetary and Small-scale Gravity Wave Modes to the 2015/16 QBO Disruption Revealed in ERA5
Hyun-Kyu LEE+, Hye-Yeong CHUN#
Yonsei University, Korea, South
Contributions of the equatorial planetary waves (Rossby wave (RW), mixed Rossby-gravity wave (MRGW), Kelvin wave (KW), Inertio-gravity wave (IGW)) and small-scale gravity wave (SSGW) to the 2015/16 QBO disruption are examined using the ERA5 data, which have finer horizontal and vertical resolutions than some other global reanalysis data sets used in previous studies. Each wave mode is selected by frequency and horizontal wavenumber criteria, based on theoretical studies, in each month for 1 year from July 2015 to June 2016. The contributions of planetary wave modes are evaluated by calculating Eliassen-Palm flux divergence (EPFD), while those of SSGW are evaluated by considering both the EPFD of IGW with horizontal wavenumbers larger than 20 and parameterized gravity waves (PGWs) calculated from an offline convective GW parameterization. It shows that RWs contribute mostly to decelerating the westerly winds at 40 hPa during the disruption, with stronger contribution by meridional-propagating components than vertical-propagating ones. MRGWs weaken the center of the westerly jet, which leads to a favorable condition for RW breaking. The negative forcing by IGWs is gradually increased since November 2016, and it is larger than RW forcing after March 2016. The negative forcing by IGWs is mostly from small scale waves with horizontal wavenumber larger than 20, which is much larger than that from some coarse-resolution reanalysis data. The PGW forcing using ERA5 is smaller than that using coarse-resolution reanalysis data in some previous studies, as more IGWs are resolved from ERA5. Accordingly, forcing by SSGWs including both small-scale IGWs and PGWs in the present study is similar to that using coarse-resolution reanalysis data. The positive forcing by KWs is prominent nearly all month and altitude, except that SSGWs provide stronger positive forcing in March 2016 at 20 hPa where strong westerlies sustain by additional support from the vertical advection.
AS40-A009
Cloud Radiative Effects on the Stratospheric Brewer-Dobson Circulation
Kai-Wei CHANG1#+, Tristan L'ECUYER2, David HENDERSON2, Yun HANG3
1Chinese Culture University, Taiwan, 2University of Wisconsin-Madison, United States, 3Emory University, United States
The Brewer-Dobson circulation (BDC) is driven by dynamics and balanced by diabatic heating, which is dominated by radiative heating above the tropopause. Clouds interact with radiation and cause radiative heating perturbations which in turn can influence the BDC. This study evaluates how the ERA5 and MERRA-2reanalyses and satellite data represent the effects of cloud-induced radiative heating perturbations on the BDC. The stratospheric residual circulation is diagnosed using all-sky and clear-sky radiative heating, and the difference between the two solutions is interpreted to be the cloud effect on the BDC. Above 70 hPa, clouds in reanalyses induce positive upward velocity anomalies near the summer hemispheric poles, suggesting that clouds tend to dampen the high-latitude subsiding branch of the BDC. Below 80 hPa, the three separate estimates show little agreement, with ERA5depicting weak cloud effects while the MERRA-2 and satellite-based results are larger in impact but opposing signs. Satellite-based estimates show that tropical cirrus strengthen equatorial upwelling as well as tropics-to-subtropics meridional transport, while the MERRA-2 solutions suggest the opposite. This discrepancy is attributed to significantly larger tropical tropopause-level cloud ice water content in MERRA-2 compared to satellite radar/lidar retrievals, suggesting that unrealistically thick high-altitude clouds result in unrealistic cloud effects on the BDC. Results suggest that the properties and frequency of tropopause-level clouds strongly influence representation of the cloud effects on the shallow branch of the BDC.
AS40-A019
Atmospheric Gravity Wave Derived from the Neutral Wind with 5-min Resolution Routinely Retrieved by the Meteor Radar at Mohe
Chi LONG1#+, Tao YU2, Yang-Yi SUN2, Jian ZHANG2, Jin WANG1, Na YANG2, Xiangxiang YANG2, Hailun YE3
1China University of Geosciences (Wuhan), China, 2China University of Geosciences, China, 3University of Science and Technology of China, China
Atmospheric gravity waves (GWs) in the mesosphere-lower thermosphere (MLT) are crucial for the understanding of general circulation. However, their dynamical characteristics are hardly retrieved due to the difficulty in the high-resolution observation of wind. Therefore, this paper uses eight years (2013–2020) of meteor radar measurements in the MLT region at Mohe station (53.5°N, 122.3°E), China, to retrieve high temporal-resolution mesospheric wind data and further evaluate the temporal variation of GW kinetic energy. As the detected meteor trails exceed 6, the wind velocity is recalculated using the least square algorithm method, significantly increasing the temporal resolution of wind from 1 h up to 5 min. This resolution is sufficiently high for the investigation of GW kinetic energy, which exhibits a high spatial-temporal variability. For instance, it is enhanced in the winter season during the period of 0200 1400 UT and in the spring season during the period of 0800–1300 UT. The similarity between the climatological characteristics of GWs in MLT and the seasonal variation of GW total energy in the troposphere, determined from high-resolution radiosondes near to Mohe station, suggests that the meteorology in the lower atmosphere could be an important source of GWs in the MLT region.
AS40-A021
Disentangling the Drivers of the Brewer-Dobson Circulation Long-term Changes
Petr SACHA1#, Petr PISOFT1+, Radek ZAJICEK1, Roland EICHINGER1, Ales KUCHAR2
1Charles University, Czech Republic, 2Universität Leipzig, Germany
The meridional overturning mass circulation in the middle atmosphere, i.e. the Brewer- Dobson circulation (BDC), was first discovered before decades based on the distribution of trace gases and a basic analytical concept of BDC has been derived using the transformed Eulerian mean equations. Since then, BDC is usually defined as consisting of a diffusive part, and an advective, residual mean circulation. Climate model simulations robustly show that the advective BDC part accelerates in connection to the greenhouse gas induced climate change and this acceleration dominates the middle atmospheric changes in climate model projections. A prominent quantity that is being studied as a proxy for advective BDC changes is the net tropical upwelling, which measures the amount of mass advected by residual circulation across a given level (the tropopause, the stratopause, 70 hPa, 100 hPa isobar) and upwards. Another robust aspect of the changes in greenhouse gas concentrations is the changing structure of the atmosphere across layers. Particularly, it was debated whether the increasing BDC is not driven by the vertical shift of the circulation. We developed an analytical method that allows us to attribute the changes in tropical upwelling to kinematic causative factors such as the accelerating residual mean circulation, changing density of air, vertical shift of the circulation and for the first time, changes in width and geometry of the upwelling region. Here we demonstrate that this is the complete set of kinematic factors influencing the net upwelling and that all these factors are important contributions to the net upwelling trend depending on the level, where the upwelling is analyzed. In our presentation we describe the method and show its utilization on ERA5 and CMIP6 data for the shallow BDC branch and on CCMI models for the deep BDC branch and the transport between the stratosphere and mesosphere.
AS41-A004
A NASA GEO Imager Research Algorithm Dataset for Cloud Optical Properties, Part I: GEO Algorithm Description
Steven PLATNICK1#+, Kerry MEYER1, Robert HOLZ2, Galina WIND3, Nandana AMARASINGHE3, Steve DUTCHER2, Andrew HEIDINGER4
1NASA Goddard Space Flight Center, United States, 2University of Wisconsin, United States, 3Science Systems and Applications, Inc., United States, 4National Oceanic and Atmospheric Administration, United States
As the NASA Earth Observing System (EOS) program ages, the new generation of advanced operational weather satellites are natural successors for extending important imager cloud climate data records begun by MODIS. In addition, many of these low-Earth orbit (LEO) observations are expected to be coupled with like observations from the new generation of advanced geostationary (GEO) imagers (e.g., ABI, AHI, etc.), allowing for the possibility of a consistent LEO/GEO cloud product Program of Record (PoR) that can enable enhanced climate and process studies by NASA investigators and the broader research community. Note that a cloud product PoR is desired to provide critical synergy with the NASA Atmosphere Observing System (AOS), which is currently in formulation and designed to address the Aerosols, Clouds, Convection, and Precipitation Designated Observables identified by the 2018 NASA Earth Science Decadal Survey. Here, we give an overview of a NASA research cloud optical property algorithm for GEO imagers that was developed to be consistent, to the extent possible, with NASA cloud continuity products from LEO imagers (Aqua MODIS MYD06, VIIRS CLDPROP for Suomi NPP and NOAA-20). Challenges and approaches the team has taken to-date to best allow for GEO/LEO continuity will be summarized (e.g., the need for common geophysical algorithms across the sensor records to account for instrument differences along with forward radiative models, ancillary data sources, and inversion approaches). We will also discuss the need for a flexible computational infrastructure that that can provide a robust and flexible science algorithm testing and intersensory evaluation tools (including colocation and combined inter-sensor match files for on-orbit evaluation).
AS41-A007
Aerosol Products from the Pandora Asia Network
Ukkyo JEONG1#+, Limseok CHANG2, Hyunkee HONG2, Hanlim LEE1, Si-Chee TSAY3
1Pukyong National University, Korea, South, 2National Institute of Environmental Research, Korea, South, 3NASA Goddard Space Flight Center, United States
For validation of the recently launched GEMS (Geostationary Environment Monitoring Spectrometer), the Korean government has supported expanding the Pandonia Global Network (PGN) over the GEMS field of view by donating over 20 instruments to Asian Countries. Currently, over 8 instruments were deployed in Thailand, Mongolia, Indonesia, and Cambodia and we are aiming to install the rest of the units by the end of 2023. As one of Asia's top air quality priorities is aerosols, the NIER (National Institute of Environmental Research) is developing an additional aerosol inversion algorithm that can be used for various types of Pandora measurements. This presentation aims to share recent updates of the PAN (Pandora Asia Network) including aerosol retrievals which will be publicly available on the NIER website. Merits of simultaneous retrievals of trace gases and aerosols will also be presented.
AS41-A008
Spatial Gap-filling of Geostationary Satellite-derived PM10 and PM2.5 Concentrations by Combining Real-time Learning and Hybrid-random Forest and Regression Kriging
Seohui PARK, Jungho IM#, Hyunyoung CHOI, Dongjin CHO+
Ulsan National Institute of Science and Technology, Korea, South
Particulate matter (PM) is one of the most harmful atmospheric aerosols which have influenced adverse human health such as respiratory and cardiovascular disease. Rapid industrial and economic growth has resulted in a significant increase in PM10 and PM2.5 in East Asia. The aerosol optical depth (AOD) from the geostationary satellite is actively used to estimate ground-level PM10 and PM2.5 concentrations due to their high temporal resolution. Since satellite-derived AOD, however, is provided under high-quality conditions, there are spatially missing values due to the bright surface, cloud contaminations, and shadows. In this study, I proposed a machine learning-based hybrid-random forest and regression kriging (Hybrid-RFK) approach for filling gaps in the geostationary satellite-based ground-level PM10 and PM2.5 concentrations over East Asia. The AOD from the Geostationary Ocean Color Imager (GOCI) was mainly used to estimate satellite-based PM concentrations by real-time learning (RTL) model, while the hybrid-RFK was developed using the meteorological and land-based products without GOCI AOD to represent full-coverage PM distributions. The estimated PM concentrations by hybrid-RFK and the RTL-based PM models have been combined with each other for better performance in the AOD available region through gaussian filtering (i.e., combined RFK-RTL). In the clear sky, in which the AOD product is available, the RTL models (R2=0.91, rRMSE=20.79% for PM10 and R2=0.90, rRMSE=26.56% for PM2.5) show more improved performance than hybrid-RFK (R2=0.56, rRMSE=45.89% for PM10 and R2=0.83, rRMSE=32.22% for PM2.5) during the cases study period (i.e., 23 May 2015). One of the main reasons is whether the AOD values were used or not. Although the hybrid-RFK is comparatively low performed than RTL-models, the hybrid-RFK also shows good agreement with observed PM concentration for all sky conditions (R2=0.77, rRMSE =44.52% for PM10 and R2=0.81, rRMSE=36.60% for PM2.5) during the same cases study period.
AS41-A010
| Invited
Clouds Induced Modulations of the Atmospheric Processes
Som Kumar SHARMA#+, Dharmendra KAMAT
Physical Research Laboratory, India
Clouds are a vital part of the hydrological cycle and play an important role in the weather and climate of the earth-atmosphere system and play a crucial role in the modulation of the Earth’s radiation balance, dynamics, and thermal balance of the atmosphere. The impact of clouds on the radiation budget of the atmosphere depends on the cloud properties, such as their frequency of occurrence, the number of cloud layers, cloud base height, cloud thickness, spatial distribution, and water/ice content. An excess surface radiative heating produces instability in the atmosphere, resulting in convection and transfer of energy from the surface and its subsequent cooling and it affects the atmospheric circulation pattern which initiates several processes and affects the meteorology of the regions. Understanding the vertical distribution of clouds, their properties, and temporal evolution is essential for understanding the origin and impact of clouds and their feedback on the above-mentioned processes and their parameterization in weather and climate models for improving forecasts. This is correspondingly essential for investigating the cloud-aerosol interaction, heterogeneous chemistry in the atmosphere, and other associated processes. Cloud properties can be investigated using in-situ observations, ground-based lidar and radar remote sensing, airborne detectors, and space-borne payloads (onboard satellites). These techniques and observing platforms are having their advantages and limitations. Lidar and Radar-based observations are having very good temporal and vertical resolution but have limited spatial coverage. Satellite observations have the advantage of providing global distribution of clouds. In this talk investigation of the atmospheric processes which are modulated due to clouds will be presented. Furthermore, the observation of clouds using various techniques and the implication of the advanced techniques in improving the understanding of atmospheric clouds will also be discussed and presented.
AS41-A012
Working Towards Dark Target Aerosol Product Synergy Among Geo and Leo Sensors
Yingxi SHI1#+, Shana MATTOO2,3, Pawan GUPTA3, Lorraine REMER1,4, Virginia SAWYER3, Yaping ZHOU1
1University of Maryland, Baltimore County, United States, 2NASA Science Systems and Applications, Inc., United States, 3NASA Goddard Space Flight Center, United States, 4Airphoton LLC, United States
Aerosols are one of the major components that affects climate and air quality. Being able to measure global aerosol comprehensively has been a major goal for the last several decades. Now with the increasing number of sensors that are capable of retrieving aerosols on both geostationary orbit (GEO) and low-Earth orbit (LEO), getting a complete picture of global aerosol distribution is more achievable than ever. However, how to use these data with various temporal and spatial resolution synergistically is one of the urgent questions that needs to be answered before combining products. Using a consistent Dark Target algorithm on three GEO sensors (two Advanced Baseline Imagers (ABI) on GOES-E and GOES-W and Advanced Himawari Imager (AHI) on Himawari-8) and three LEO sensors (Moderate resolution Imaging Spectrometers (MODIS) on Terra and Aqua and the Visible Near-Infrared Imaging (VIIRS) on Suomi-NPP), we evaluate six level 2 DT aerosol optical depth (AOD) products against Aerosol Robotic Network (AERONET) as well as Marine Aerosol Network (MAN) and investigated the similarity and differences among the products with a special focus on the two GEO and LEO common regions, namingly North America and East Asia. The error statistics of these products are generated against observing conditions with major uncertainty sources identified. Our results provide baseline evaluation results before synergy of DT aerosol products can be pursued.
AS42-A005
The Capability of X-band Radar for Diagnosing the Trigger and Developing Convective Rainbands in the Gap Area of a C-band and S-band Radar Network
Yabin GOU1#+, Haonan CHEN2
1Hangzhou Meteorological Observatory, China, 2Colorado State University, United States
It is cost-effective to use X-band polarimetric radar to fill the large gap between C-band or S-band radar networks for severe weather monitoring and nowcasting; however, X-band radar suffers more attenuation than C- and S-band due to its short-wavelength characteristics, particularly in convective situations. In this work, a combined utilization of a radar network, which includes a C-band radar in Hangzhou located on the top of a western mountain (1512 m), an S-band radar in Ningno near the East Sea (454 m), as well as an X-band radar (816 m) located in their vertical gap, is used to demonstrate the capability of X-band radar in analyzing the developing convective rainstorms, after the attenuation correction for horizontal reflectivity (ZH) of all three radar. The result shows that (i) after the significant attenuation on ZH is corrected based on the self-consistency approach, X-band radar exhibits finer and even larger ZH than S- and C-band radar when it captures the lowest part of the convective rainbands relative to the other two radars. (ii) The trigger and developing convective rainbands occurred on the lower atmospheric layers, which are insignificant in the view of S- and C-band radar because of longer distances, are all well captured by the X-band radar in their gap area. (iii) Benefiting from the nearest distance, S-band radar afterward captured the lowest developing part of another convective rainband with the most significant ZH, which is different from but similar to that captured by X-band radar. In these senses, the X-band radar effectively favors diagnosing the trigger and developing of convective rainstorms in the gap area of this S- and C-band radar network.
AS42-A007
Precipitation Microphysical Processes in the Tropical Cyclone Inner Rainband and Tropical Squall Line Revealed by Polarimetric Radar
Hepeng ZHENG#+, Yanqiong XIE, Yun ZHANG, Zuhang WU
National University of Defense Technology, China
Polarimetric radars provide new insights into the precipitation microphysical processes and characteristics in a tropical cyclone (TC, Kajiki 2019) inner rainband and a tropical squall line in the South China Sea. The precipitation of Kajiki is dominated by high concentrations and small (< 3 mm) raindrops, which contribute more than 98% to the total precipitation. The formation of precipitation in the inner rainband of Kajiki is dominated by warm-rain processes, and accretion and coalescence play a critical role in the formation of heavy rainfall. At the same time, the melting of different particles generated by the ice process has a great influence on the initial raindrop size distribution (DSD). The aloft DSD above heavy rain with the effect of graupel has a wider spectral width compared with the region affected by dry snow. A tropical squall line was also documented. The ZH is similar for both convective systems, while the ZDR (KDP) is higher (lower) at the front of the squall line, indicating a low concentration of large drops; the peak values of ZH, KDP, and ZDR in the inner rainband are all concentrated in the convention center. The trend of liquid water content toward the ground within the squall line is consistent with that of the inner rainband, while the mean value is lower, and is more affected by ice processes. This work may contribute to our understanding on cloud microphysics of tropical convective systems using polarimetric radars.
AS42-A011
Precipitation Structures and Convective Characteristics of MCSs Associated with Different Large-scale Circulations Over Southern China
Hao CHEN1#+, Weixin XU1, Jiaolan FU2, Nana LIU3, Jianhua SUN4, Lejian ZHANG5
1Sun Yat-sen University, China, 2National Meteorological Center of China Meteorological Administration, China, 3University of California, United States, 4Chinese Academy of Sciences, China, 5Meteorological Detection Center of China Meteorological Administration, China
Mesoscale convective systems (MCSs) are frequent in Southern China (SCH) during warming season and can result in severe weathers. While the large-scale circulations and precipitation patterns of MCSs over SCH have been well studied, studies on finer-scale (meso- and micro-) structures of MCSs are still limited, especially changes in MCS structures associated with different large-scale circulations. In this study, we first identify and track nearly three warm seasons of MCSs over SCH using operational radar network data in China. Multi-source observations are then collocated into MCSs to examine the precipitation intensity, horizontal organization, vertical structure, and ensemble microphysics of MCSs. MCSs are stratified by six types of large-scale circulations, including front (7%), southwest vortex (SW-Vortex, 15%), trough (10%), tropical cyclone (TC, 18%), South China Sea vortex (SCS-Vortex, 10%), and other (40%). Our results reveal significant variations in the precipitation structures and convective characteristics of MCSs developed under various large-scale circulations. For example, MCSs of SW-Vortex and trough types exhibit the strongest and deepest convection as indicated by radar and IR observations, but the trough-type MCSs have a much smaller precipitation area and a shallower column of ice particles (microwave-based) likely due to a drier troposphere. Interestingly, MCSs associated with TCs and SCS-Vortex have the weakest convective intensity and the least lightning density, although they produce heavier precipitation at the surface. Mechanisms responsible for the variations in meso- and micro-scale structures among MCSs produced by various types of large-scale circulations will be further investigated.
AS42-A017
Beam Blocking Mitigation of X-band Radar Data and its Application for QPE Improvement of S-band Radar Network
Daehyung LEE1, Choeng-Lyong LEE1, SeungWon BAEK1#+, Geunsu LYU1, Wonbae BANG1, Park HONG-MOK1, Alexander RYZHKOV2, Gyu Won LEE1
1Kyungpook National University, Korea, South, 2NOAA/OAR/National Severe Storms Laboratory, United States
Two X-band dual polarimetric radars were installed in the Seoul metropolitan area to supplement the limitation of low-level observation of the S-band radar network. High spatiotemporal resolution data of the X-band radar can be useful for flash flood monitoring and forecasting. However, there were unexpected beam blocking areas caused by artificial buildings, trees and terrain which cannot be detected using DEM (Digital Elevation Model) based on beam blocking simulation results and the real time beam blocking detection (consisting of the standard deviation of radar variables and co-polar cross-correlation coefficient). The frequency of occurrence of dual-polarization parameters (FOD) technique, an extended method of the frequency of occurrence of reflectivity technique (FOR, Chang et al. 2009) was used in this research to improve the beam blocking detection. This method is applied to the beam blocking detection and identifies ground clutter using feature parameters consisting of dual-polarization parameters (ZDR, ρHV), proxy quantity dubbed depolarization ratio (DR) and their statistical variation (horizontal and vertical standard deviation, average, texture, etc.). The blockage areas are categorized using fuzzy logic based on FOD parameters. Different types of HSR masks (beam blocking simulation with DEM, real time beam blocking, FOR and FOD) were applied to Hybrid Surface Rainfall (HSR, Lyu et al. 2015) estimation with various methods (R(ZH), R(ZH, ZDR), R(ZH, KDP), R(ZH, KDP_P) and R(ZH, AH)) to validate effect of FOD. QPE accuracy of the X and S-band radar was validated with rain gauges and compared with the QPE of S-band radar.
Acknowledgment
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A4A1032646). This work was funded by the KMA Research and Development Program “Observing Severe Weather in Seoul Metropolitan Area and Developing Its Application Technology for Forecasts” under Grant (KMA2018-00125).
AS42-A018
Improved Combination of Different Disdrometers Data for Complete Drop Size Distribution
Sanghun LIM1+, Wonbae BANG1, Kyuhee SHIN1, Kwonil KIM2, Viswanathan BRINGI3, Merhala THURAI3, Gyu Won LEE1#
1Kyungpook National University, Korea, South, 2Stony Brook University, United States, 3Colorado State University, United States
Raindrop Size Distribution (DSD) has been studied since the late 19th century by observing different disdrometers. Especially, the 2D-video disdrometer (2DVD) was widely used in many studies because the 2DVD has relatively high accuracy for the measurement of physical variables of drop by using two orthogonal optical cameras with high performance. However, the 2DVD data tends to underestimate the concentration of small raindrops, especially drop diameters below 0.7 mm. Against the underestimation issue, recent studies have tried to combine 2DVD data with Meteorological Particle Spectrometer (MPS) data showing a more realistic number concentration of small drops. Simply, the complete DSD is adding 2DVD DSD above 1.125 mm channel and MPS DSD less than 1.125 mm. Meanwhile, the complete DSD can be discontinuous when the number concentration difference between 2DVD and MPS nearby the binding point is too large. In this study, we propose an improved combination method based on the weighting factor. The new complete DSD was produced by applying the distance weighting factor between 2DVD and MPS about a specific drop channel range 1 mm to 1.25 mm. We compare the rainfall rate between the original complete DSD and the new complete DSD as a reference to Pluvio data. The comparison for summer rainfall events in 2022 in Incheon, South Korea shows the new complete DSD has relatively higher skill scores. We will also compare radar reflectivity between the two methods as a reference to Precipitation Occurrence Sensor System (POSS) data.
ACKNOWLEDGEMENT
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A4A1032646).
AS42-A019
Investigating the Potential Interaction Between Updraft and Microphysical Processes Near the Dendritic Growth Layer
Ji-Hye JUNG1+, Kwonil KIM2, Kyuhee SHIN1, Gyu Won LEE1#
1Kyungpook National University, Korea, South, 2Stony Brook University, United States
The dendritic growth layer (DGL) at an altitude of about -15 °C plays an important role in the production and growth of snowfall. In the DGL, the difference in saturated vapor pressure between ice and water is maximized, resulting in the rapid growth of dendritic ice particles and increasing ground precipitation. Despite the research efforts in previous studies, the microphysical characteristics of snowfall in the DGL and its role in the dynamical and thermodynamical processes are not yet fully understood. In particular, noticeable updrafts and bimodal particle size distribution in the vicinity of DGL are often observed, but their underlying mechanism remains unknown. Recently, Ye and Lee (2021) established a hypothesis that the generation of new small particles is favorable due to the supersaturation associated with the updrafts below.In this study, we will try to reveal the interaction between updrafts and snowfall microphysics in the DGL by using data from intensive observations during the ICE-POP 2018 (International Collaborative Experiments for Pyeongchang 2018 Olympic & Paralympic winter games). We analyzed the vertical profiles of polarimetric radar variables from surveillance radar, the Doppler spectrum of vertically pointing radar, and the 3-hr rawinsonde data. Furthermore, the vertical air velocity estimation technique was applied to the vertically pointing radar to quantify the updraft in the DGL. The three analyzed cases revealed the presence of the updraft around -15℃. There was an increase in reflectivity, a maximum value of differential reflectivity and specific differential phase, and a decrease in the cross-correlation coefficient in the region where the updraft was at its maximum intensity. We will suggest the possible mechanisms of the generation of small particles and updraft.
ACKNOWLEDGEMENT
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A4A1032646).
AS43-A001
Retrieving the Atmospheric Motion Vectors from the Geostationary Satellite Images by Using the Convolutional Neural Network
Renge ZHOU#+, Keyi CHEN
Chengdu University of Information Technology, China
Atmospheric motion vectors (AMVs) are of great significance for constructing initial fields of the numerical weather prediction and analyzing damaging weather processes such as typhoons and heavy precipitation. Based on the convolutional neural network (CNN) architecture, this study uses transfer learning in deep learning strategy to retrieve the AMVs from the infrared and water vapor images of the geostationary satellites Himawari and FY-4A respectively, and finally the output of the neural network model is stitched and merged to obtain the AMVs within the same observation area of the two satellites. The results show that CNN can effectively acquire the information from the satellite images and convert it into vector wind fields at various height layers. Compared with the traditional algorithms, AMVs retrievals with machine learning algorithms have the features of no requirements for the height assignment, the ability to display the complete atmospheric circulations at different height layers and the uniform AMVs distribution in the vertical direction.
AS43-A004
Enhancing Typhoon Precipitation Nowcasting via Spatial and Temporal Difference in Deep Learning
Hongyi YAO#+, Ji CHEN
The University of Hong Kong, Hong Kong SAR
Tropical cyclones (TCs) always bring torrential rains triggering loss of property, even lives. Nowcasting heavy rainfall from TCs within 2 hours is thus an important topic in meteorology and hydrology. Traditional numerical weather forecasting fails to provide accurate results due to spin up in such short lead time while deep learning-based extrapolation has proven its potential. In this work, we proposed a multi-tasking learning framework to forecast the rotating features of TCs. Spatial and temporal difference (STD) are coupled with structural similarity (SSIM) to better predict periphery rainfall bands and rotation. The framework adopted two different backbones namely convolutional long short-term memory (ConvLSTM) and U-Net neural network with fed of radar reflectivity composite. The results showed that: (1) the coupling of STD and SSIM could significantly increase performance matrix compared to traditional deep learning with SSIM loss function only. The average improvement of critical success index (CSI) of 30 dbZ are 84% and 8.9% in ConvLSTM and U-Net, respectively, and the decreasing of mean absolute error (MAE) are 7.1% and 4.6%. (2) The movement of TCs, including transformation and rotation are observed in our proposed framework, indicating the effectiveness of spatial and temporal difference. However, the blur issue exists, especially with lead time over 1 hour, which calls for physical driving coupled in deep learning.
AS43-A006
Application of ConvLSTM and Optical Flow Method Integration in Extreme Precipitation Nowcasting
Hongxu ZHU#+, Ji CHEN
The University of Hong Kong, Hong Kong SAR
In recent years, extreme precipitation has brought serious losses, accurate and timely forecasting of extreme precipitation has become more and more important. This study analyzes the radar echo data of some extreme precipitation in Shenzhen using Convolutional Long Short-Term Memory (ConvLSTM) network. Based on the radar echo data, our study calculates the optical flow field by variational echo tracking (VET) method, which is added to model input and prediction respectively. This study also explores why optical flow field can improve the performance of the model. The outcome shows that the total loss is reduced by approximately 7% compared with pure ConvLSTM when the optical flow field is added to model input, and 12% when it is also added to model prediction. It is also shown that the ConvLSTM model with optical flow field as additional input is equal to a more complex ConvLSTM model since optical flow field calculated by radar echo data can’t provide more real-world information. Meanwhile, when optical flow field is also added to model prediction, the model performs better because additional information is considered, which also provides the basis for combining with numerical weather forecast results.
AS43-A007
Hybrid Hydrodynamic-machine Learning Modeling-based Flood Susceptibility Analysis Under Climate Change
Weifeng WU+, Chia-Jeng CHEN#
National Chung Hsing University, Taiwan
Climate change will induce more extreme rainfall events, leading to less reliable flood susceptibility analysis based on the existing hydrological handbook. To better distinguish flood-prone areas in a more variable environment, this study aims to propose a hybrid assessment framework that uses a hydrodynamic model referred to as the Two-dimensional Runoff Inundation Toolkit for Operational Needs (TRITON) and three machine learning models, namely Convolutional Neural Networks (CNN), Random Forest (RF), and Support Vector Machine (SVM), for flood susceptibility analysis in Changhua county, Taiwan. TRITON, which makes use of graphics processing units to achieve high-performance computing, simulates Probable Maximum Precipitation (PMP) and Probable Maximum Flood (PMF) in various scenarios to identify flood susceptible sites that are adopted as the training and validation points for the machine learning models to develop flood susceptibility mapping. Preliminary results show that the “very high” flood susceptibility category accounts for 13% to 20% under the SSP5-8.5 scenario, suggesting a 6% increase compared to the baseline analysis. It is expected that the hybrid modeling framework can not only deal with data scarcity regarding historical flood susceptible sites but also produce flood susceptibility maps for disaster preparedness.
AS43-A008
A Comparative Study on Rainfall Nowcasting Using Deep Learning Methods
Xianqi JIANG+, Ji CHEN#
The University of Hong Kong, Hong Kong SAR
With the requirement of high accuracy and short responding time, rainfall nowcasting has become a significant challenge for weather authorities to provide timely and accurate alerts of floods to the public. Hence, three state-of-the-art deep learning models, the Convolutional Long Short-Term Memory (ConvLSTM), the Trajectory Gated Recurrent Unit (TrajGRU), and the Predictive Recurrent Neural Network (PredRNN), are trained and tested for rainfall nowcasting with a newly collected radar echo maps dataset provided by the Meteorological Bureau of Shenzhen Municipality in China. All three deep learning models outperform the traditional optical flow-based extrapolation method in all performance metrics, improving the performance by up to 63%. Performances of those models are further compared and discussed with three typical cases of different rainfall intensities in South China, showing the prediction accuracy for 0-2 hours nowcasting using deep learning. Data fusion between different cities in the same area is also tested for the building of high-quality rainfall dataset for nowcasting tasks. The difference is less than 5% when the model has multiple data sources which proves the robustness of the deep learning models. Analysis are carried out regarding the effectiveness of deep learning techniques on rainfall nowcasting, suggesting ways of improvement in the future.
AS43-A016
Whether Raises the Embankment is Enough for Future Climate Change - A Study to Predict River Water Level in Coastal Basins Using a Hybrid Machine Learning Model Framework
Shaoxu ZHENG1#+, Zhan TIAN1, Yingping ZHAO2, Qian KE3
1Southern University of Science and Technology, China, 2Pengcheng Laboratory, China, 3Erasmus University Rotterdam, Netherlands
Making sure of the safety of embankments, which are powerful measures to prevent river from flooding thus safeguarding people’s lives and property, is crucial, especially when human society is under rapid development and the impacts of climate change are becoming bigger and bigger. However, engineering measures previously constructed may not meet the risk resistance requirements at the time of embankments construction. This study evaluates the resilience of embankments against future risks of Maozhou River as a case study, which is a cross-border river connecting to the Pearl River Estuary. The modelling of water dynamics in coastal basins is very complex and challenging, for flood events in estuary areas are often compounded by extreme rainfall and tidal patterns. To overcome this challenge, this study uses the water level data of Maozhou River in Shenzhen, China and employs wavelet transform method to decompose the water level data into two time series parts: direct runoff related part and base flow related water level part, which correspond to the part influenced by precipitation and the part by tidal events, respectively. These two parts time series data are modelled separately using a hybrid machine learning model framework, and then combined together for the final composite water level analysis. This method preprocesses water level based on the rainfall-runoff process and can significantly improves model’s prediction performance when compared with models that simply uses rainfall and tidal events as covariates. Finally, with our method, using the rainfall data predicted from IPCC6, this study forecasts the future changes in water level with better accuracy, providing a scientific evaluation method for embankment safety.
AS44-A001
Atmospheric Contributions of Water-soluble and Water-insoluble Nitrogen and Phosphorus Species to the Southern East China Sea
Hung-Yu CHEN#+, Meng-Lun CHEN
National Taiwan Ocean University, Taiwan
From Oct-2019 to Sep-2020, a high-volume sampler was used to monitor atmospheric dry deposition over Mazu Island which is located at the southern end of the East China Sea. The collected samples were divided into coarse particles and fine particles using a six-stage particle size separator, and the nitrogen (N) and phosphorus (P) species were categorized as either water-soluble (WS) or water-insoluble (WI). In this study, WS-TN and WI-TN accounted for 74% and 26% of TN, while WS-TP and WI-TP accounted for 47% and 53% of TP, respectively. According to the historical literature, the proportions of WI-TN and WI-TP in TN and TP are 39-51% and 95% in inland areas, which are significantly higher than 8-26% and 53-63% observed in coastal atmospheres. Correlation analysis results showed that there was a high correlation between WS-TN and WI-TN (r = 0.79, p < 0.01) and a moderate correlation was noted among nss-K+, nss-Ca2+, and nss-SO42-. The results show that WS-TP and WI-TP may be derived from fossil fuel combustion and biomass combustion, respectively. In terms of particle size distribution, the ratios of the concentrations of WS-TN, WI-TN and WS-TP within fine particles are 72%, 93% and 72%, respectively. However, WI-TP displays the opposite pattern since the proportion of fine particles is only 37%. Flux calculation results show that the annual fluxes of TN and TP are 48.4 and 0.29 mmol m-2 yr-1, respectively. Both TN and TP had the highest average daily flux during winter; of these, up to 88% of the annual N flux consisted of WS species. On the other hand, approximately 69% of P was dominated by WI species. The above results show that N has a higher bioavailability than P in the areas, which may cause nutrient imbalances in adjacent ecology.
AS44-A008
Abundant Nitrogenous Secondary Organic Aerosol Formation Accelerated by Cloud Processing
Zhe LIU#+, Jianmin CHEN
Fudan University, China
Nitrogenous organics (CHONs) are one of the most important components of secondary organic aerosol (SOA). However, the formation mechanism of CHONs in clouds has rarely been studied. Here, we observed the evolution of CHONs during cloud processes (CPs) and found that CPs significantly enrich the diversity of CHONs, specifically generating CHONs with O numbers of 1–10 and double bond equivalent (DBE) values of 2–10, which can be described by the formula CnH(2n-16)–(2n)O1–10N1–4. We proposed that the CHONs formed during CPs are likely formed through aqueous phase reactions with CHO compound precursors via nucleophilic attacks by NH3. Nearly 77% of the CHONs in cloud water can be accounted for by this scheme, and 66% of all CHONs are formed through reactions between NH3 and carbonyl-containing biogenic volatile organic compound (BVOC) ozonolysis intermediates. This study provides the first insights into the evolution of CHONs during CPs and reveals the significant roles of CPs in the formation of CHONs.
AS44-A010
The Impact of Clean Heating Reform on the Size Distribution of Nitrated Phenols and its Association with Biomarkers of Homemakers in the Fenwei Plain, China
Rong FENG+, Hongmei XU#
Xi'an Jiaotong University, China
The clean heating renovation has been executed for improving particulate matter (PM) pollution in northern China since 2017. This study determined particle size distributions of nitrated phenols (NPs) in personal exposure (PE) samples and its associations with biomarkers in saliva and urine from homemakers in rural households of the Fenwei Plain, China. Remarkable reductions of 28.6–66.3% and 52.2–82.4% on PMs and total quantified NPs were found with the substitutions of raw coal chunk and biomass by advanced clean coal. 4-Nitroguaiacol (4NG) showed the largest reductions of 81.2% among individual NP. In addition, the clean coal efficiently reduced interleukin-6 (IL-6) and 8-hydrox-2'-deoxyguanosine (8-OHdG) in the urine and saliva by 12–72%. Furthermore, significant positive correlations between urinary 8-OHdG with most of NPs in all particle sizes, urinary IL-6 with 4NG for particles with Dp > 2.5 µm and Dp = 0.25–1.0 µm, salivary IL-6 with 4-nitrocatechol (4NC) and 4-methyl-5-nitrocatechol (4M5NC) for particles with Dp > 2.5 µm, Dp = 0.5–1.0 µm, and Dp < 0.25 µm were observed, but not for salivary 8-OHdG or PMs. The results provide scientific support for the clean energy reformation and demonstrate the strong particle size dependence between NPs and biomarkers.
AS44-A011
Modeling the Regional Nitrogen Cycle in the Atmosphere and its Response to the Future Emission Control Strategy
Qi FAN#+
Sun Yat-sen University, China
The characteristics of the regional nitrogen cycle have not been fully understood and its response to the future emissions control strategy is warranted. Here, we used the WRF-CMAQ model to reveal the regional nitrogen cycle (emissions, concentrations, and depositions) in the atmosphere in January (winter) and July (summer) 2015 and anticipate its changes under emissions control by 2030 in YRD. The model has reasonable simulations for the meteorological factors, chemical concentrations, and depositions in 2015. The results show that the nitrogen concentration (deposition) is generally higher (lower) in January than in July due to higher precipitation and dry deposition velocity in summer. Local emissions of YRD are the major contributors to the concentration in this region. For the deposition, HNO3, NH3, NO3-, and NH4+ are the major species. The depositions of oxidated nitrogen and reduced nitrogen account for 62% and 38% of the total nitrogen deposition in January, while their proportions are 51% and 49% in July. To achieve the carbon peak emission in 2030, the NOx and NH3 emission is projected to reduce by ~51% and ~22%, respectively. The concentration and deposition of oxidated nitrogen will decrease by ~50%, generally in consist with the reduction of NOx. However, the NO3- concentration is less responsive to the emission reduction in January because the contribution of NOx reduction will be offset by the increase of atmospheric oxidation capacity during nighttime. The lower reduction of NOx than NH3 results in a higher proportion of reduced nitrogen than oxidated nitrogen in deposition. In addition, the smaller reduction of reduced nitrogen wet deposition than sulfur wet deposition and oxidated nitrogen wet deposition can raise the pH of precipitation and help alleviate the acid rain problem, especially in July.
AS47-A001
Changes to the IMERG Algorithm from V06 to V07
George J. HUFFMAN1, David BOLVIN2, Eric NELKIN2, Robert JOYCE2, Jackson TAN3,1#+
1NASA Goddard Space Flight Center, United States, 2Science Systems and Applications, Inc., United States, 3University of Maryland, Baltimore County, United States
The Integrated Multi-satellitE Retrievals for GPM (IMERG) product from the U.S. Science Team of the Global Precipitation Measurement (GPM) mission provides estimates of surface precipitation rate at 0.1° every half-hour globally, with three different Runs to cater to various latency requirements. The latest version (V07) of IMERG, which involves a uniform reprocessing of the full 20+ years of record spanning the TRMM and GPM projects, includes numerous changes to the algorithm that are expected to improve the precipitation estimates in different ways. This poster will describe the major changes in the algorithm from the previous V06 to latest V07 and show examples of the associated improvements. One prominent issue with IMERG V06 is an overestimation of the satellite-only precipitation estimates, especially during the TRMM era; this poster will summarize the cause and the solution adopted in V07. Another issue that was identified in the development of V07 is a 0.1°-eastward spatial offset in the gridded microwave estimates and hence most of the inputs; this poster will demonstrate the improvement resulting from the correction. As well, changes to the Kalman filter in IMERG are expected to improve the distribution of estimated precipitation rates and mitigate the differences arising from the use of diverse types of sensors. Other changes in V07 include a modification of the motion vector source to address deficiencies in the precipitation propagation near orography, a modernized infrared precipitation algorithm, an update to the precipitation phase parametrization for improved consistency, and a renewed effort to implement climatological gauge adjustment to the near-real-time Runs. These enhancements in IMERG V07 are focused on the goal of providing the community with a long record of reliable high-resolution precipitation observations.
AS47-A004
GPCP Version 3.2 Products and Results
George J. HUFFMAN1#+, Ali BEHRANGI2, Robert ADLER3, David BOLVIN4, Eric NELKIN4, Guojun GU3, Mohammad Reza EHSANI2
1NASA Goddard Space Flight Center, United States, 2University of Arizona, United States, 3University of Maryland, United States, 4Science Systems and Applications, Inc., United States
The Global Precipitation Climatology Project (GPCP) products address the need for long-term precipitation products that emphasize homogeneity, following Climate Data Record (CDR) principles. The new-generation Version 3.2 provides key improvements over the operational Version 2.3 such as: finer spatial resolution of 0.5°x0.5°; wider geosynchronous infrared estimation (58°N-S) upgraded with the PERSIANN-CDR algorithm; upgraded retrievals from selected passive microwave sensors (GPROF algorithm) that calibrate the IR input; revised intercalibrations of TOVS and AIRS data (used at high latitudes); climatologies based on CloudSat, TRMM, and GPM to provide overall calibration by modern satellite estimates; the latest Global Precipitation Climatology Centre (GPCC) precipitation gauge analyses over land areas; regional modifications to the gauge undercatch correction; and IMERG half-hourly data input to the Daily V3.2 product. We will show sample analyses that demonstrate aspects of the Version 3.2 precipitation record, such as the global climatology, the time series for global land and ocean total precipitation and snowfall, and the time series of tropical land and ocean daily precipitation rate histograms. For selected analyses we will show improvements in both the Monthly and Daily products in Version 3.2 compared to the operational Version 2.3. In particular, the climatological zonal profile of precipitation in the Southern Ocean, extending south of 40°S, improves a suspected artifact in V2.3. Similarly, the Daily histograms over ocean in Version 3.2 lack the jump in the predecessor Version 1.3 Daily over ocean at the start of 2009, although a smaller jump is introduced in June 2014. The presentation will conclude with a prospectus for the future satellites/sensors and community datasets necessary to continue computation of a consistent CDR product on the one hand, while also potentially contributing to improvements in the historical record.
AS47-A005
Quantitative Evaluation of Graupel Shape Observed by Particle Imaging Radiosonde "Rainscope" in Baiu Convective Cloud
Yurika HARA1+, Kenji SUZUKI1#, Tetsuya KAWANO2
1Yamaguchi University, Japan, 2Kyushu University, Japan
A new balloon-borne precipitation particle imaging radiosonde named "Rainscope" has been developed. The decisive difference between the Rainscope from the ground-based disdrometer is that it can know the vertical distribution of microphysical parameters. In other words, from the liquid phase to the ice phase such as graupel and snowflakes that exist above the freezing level, their types, shapes, sizes, spatial concentrations, etc. in clouds are provided. It is a powerful tool for the ground validation of remote sensing techniques. For example, it can provide observational data useful for the validation of GPM DPR products such a "binHeavyIcePrecipTop", which was newly released in 2021 and shows the upper end elevation of strong solid precipitation in clouds below -10ºC. The Rainscope was first deployed in the intensive observation campaign, which was conducted in Kyushu region during the Baiu rainy season in 2022. It was launched into convective clouds with active lightning and gust on 25 June 2022. It transmitted images of ice particle in the process of melting just below 0ºC, and frozen particles with semi-transparent and smooth outlines around 0ºC. And white and irregularly shaped graupel were observed across all layers up to -30ºC level. The clear particle images captured by the Rainscope enable us to get more detailed information of particle shapes, surface conditions, and contours, making it easier to evaluate their shapes quantitatively. The circularity of graupel was smaller in upper layer. It has a longer circumference and more irregular shapes, suggesting an active riming process originated from ice crystals. On the other hand, graupel in lower layer with larger circularity was suggested to be originated from a frozen particle. The different graupel formation processes was considered to exist in convective clouds.
AS47-A009
Investigation of Moving Vector Calculation at High Latitudes Using NEXRA Data for Polar Extension of the GSMaP PMW-IR Combined Algorithm
Munehisa YAMAMOTO1#+, Takuji KUBOTA1, Ying-Wen CHEN2
1Japan Aerospace Exploration Agency, Japan, 2The University of Tokyo, Japan
The Global Precipitation Measurement (GPM) project leads the global distribution of precipitation by combining observations from multiple microwave radiometers (PMWs) onboard low Earth orbit satellite. Since temporal resolutions shorter than 3 hours cause sampling gaps only by PMW observations, a combined PMW-infrared (IR) combined algorithm has been developed to interpolate precipitation areas based on cloud areas and their moving vectors using IR images from geostationary meteorological satellites. It is difficult to accurately capture cloud areas at high latitudes due to radiometric effect at large zenith angle from the geostationary Earth orbits. Therefore, the coverage of major PMW-IR combined satellite precipitation map products has been limited to the equatorial region below 60 degrees latitude. The Global Satellite Mapping of Precipitation (GSMaP) product version 05 (algorithm version 8), released in December 2021, provides precipitation estimation up to the poles only in the PMW observation area. However, a polar extension of the PMW-IR combined algorithm has been expected to fill the remaining PMWs sampling gaps. This study examined the derivation of moving vectors using Nonhydrostatic Icosahedral Atmospheric Model-Local Ensemble Transform Kalman Filter (NICAM-LETKF) Japan Aerospace Exploration Agency (JAXA) Research Analysis (NEXRA), which is in regular operation together with GSMaP to extend the PMW-IR combined algorithm to the polar regions. The moving vectors of column water vapor and precipitation were calculated by modifying the current version of GSMaP moving vector calculation program to extend poleward and to allow the use of geophysical quantities other than IR. In this presentation, we will compare the results with other numerical weather forecast data used in previous studies and discuss issues for their use.
AS47-A011
Analysis of the Environment and Precipitation Characteristics of Widespread Extreme Rainfall Events During the Akisame Season
Yukari TAKAYABU#+, Aiko NARITA
The University of Tokyo, Japan
Akisame season is the autumn rainy season in Japan, with heavy rainfalls particularly recorded in eastern Japan. However, research on heavy rainfalls in the Akisame season is not as sufficient as those for the Baiu season. The objective of this study is to clarify the environment and precipitation characteristics of widespread heavy rainfalls during the Akisame season. We utilized gauge data collected by the Automated Meteorological Data Acquisition System (AMeDAS) stations for 1979-2020 to define the widespread heavy rainfalls. Japanese 55-year Reanalysis (JRA-55) and rainfall data from the Global Satellite Mapping of Precipitation (GSMaP) are utilized to analyze the environments and rainfall distributions. GPM/DPR data are utilized to examine the characteristics of rainfall events embedded in the widespread heavy rainfall events in Akisame season. Widespread extreme precipitation event cases in western Japan in Baiu season and in eastern Japan in Akisame season are compared. A northwest-southeast dipole structure in the geopotential height anomalies is found from the lower to upper level for the Baiu case, while a northeast-southwest dipole structure is found in the Akisame case. These different structures of anomalous field tend to enhance the water vapor flux associated with the different mean large-scale circulations in the two rainy seasons, preparing large precipitable water field. Next, three-dimensional rainfall characteristics are examined with the GPM/DPR overpasses for four representative cases of widespread extreme precipitation events in Akisame/Eastern Japan cases. Two of the four representative cases are associated with precipitation systems with strong convective precipitation. Other two cases are characterized as organized precipitation systems with very intense precipitation, but with moderate heights. The latter cases are similar to the precipitation system observed in the record-breaking extreme rainfall event in July 2018.
AS47-A013
What Do the Latest Global Oceanic Precipitation Estimates from GPM V7 and GPCP V3.2 Products Tell Us?
Ali BEHRANGI1#+, Yang SONG2
1University of Arizona, United States, 2Hohai University, China
Satellite observations have brought opportunities to quantify the amount and distribution of precipitation over the globe, critical to understand how the Earth system works. The amount and spatial distribution of oceanic precipitation from the latest versions (V7 and the previous version) of the Global Precipitation Measurement (GPM) core-instruments and the constellation of passive microwave sensors are quantified and compared with other products such as the Global Precipitation Climatology Project (GPCP V3.2), the Merged CloudSat, TRMM and GPM (MCTG), and ERA5. Results show that GPM V7 products have higher precipitation rate than the previous version, except for the radar-only product. For the ~ 65oS-N region, covered by all of the instruments, this increase ranges from about 9% for the combined radar-radiometer to about 16% for radiometer-only product. While GPM precipitation products still show lower values than MCTG (except over the tropics and Arctic Ocean), the V7 products (except radar-only) are generally more consistent with MCTG and GPCP V3.2 than V5. Precipitation products are found to be least consistent over the Southern Oceans, displaying the largest spread in mean precipitation rate and location of latitudinal peak precipitation. Over the tropics, (25°S-25°N) passive microwave sounders show the highest precipitation rate, and the highest increase (~19%) compared to their previous version, among all of the studied precipitation products. Furthermore, analysis showed that precipitation products are generally less consistent (larger spread) over lower and higher values of sea surface temperature and total precipitable water. Analysis of mean monthly precipitation variation (MPV) showed that MPV is relatively small when averaged over 90°S-90°N and 65°S-65°N (e.g., ~4-6% of the annual mean precipitation rate), but is large over the tropics (e.g., 9-11%) and high latitudes (~26-55%).
AS47-A015
Precipitation Characteristics of the Tropical Cyclone Over the Arabian Sea
Amit KUMAR1#+, Atul Kumar SRIVASTAVA1, Manoj K. SRIVASTAVA2
1Indian Institute of Tropical Meteorology, India, 2Banaras Hindu University, India
Over the Arabian Sea, the tropical cyclone (TC) formed during the post-monsoon season is investigated through the Global Precipitation Measurement (GPM) satellite level 2 observation. The precipitation characteristics of the TC developed between 2014 and 2021 are analyzed to understand the cyclonic rainfall's precipitation characteristics. 2-D distribution between the liquid water content (LWC) and non-liquid water content (IWC) shows considerable variations in the different precipitating cloud. In the convective cloud, the LWC is 0-800 g/m2, and IWC is about 0-300 g/m2. The amount of LWC is low, and IWC is higher in the stratiform cloud than in the convective cloud. In the stratiform (convective) cloud of the TC, the mean of normalized intercept parameter (Nw) and mass-weighted mean diameter (Dm) is 34.0 (35.54) mm-3m-1 and 1.27 (1.31) mm, respectively. Moving from the smaller to the bigger rain droplets, the value of Nw decreases, as observed in the 2-D distribution between Dm and Nw. The concentration of the bigger rain droplets is high in the convective cloud, and stratiform cloud is dominated by the smaller rain droplets. The contoured frequency altitude diagram (CFAD) of the Dm and reflectivity (Ze) for the stratiform and convective cloud of the TC indicate significant variation in the droplet's state above and below the melting layer. Ice particles and droplets in the supercooled liquid state dominate above the melting layer, and below it, a high concentration of rain droplets in the liquid form observed. Below the melting layer, the contribution of the various microphysical processes (size-sorting, evaporation, breaking-up and collision-coalescence process) in the rain droplets formation is different for the stratiform and convective cloud. The breaking-up process acts as the primary microphysical process in the stratiform cloud, and the collision-coalescence process is predominating in the convective of the TC.
AS51-A010
Numerical Simulation of Heavy Rainfall Events Over the Korean Peninsula During Summer of 2022
Sujeong CHO#+, Eun-Hee LEE, Keon-Hee CHO, Ji-Young HAN
Korea Institute of Atmospheric Prediction Systems, Korea, South
The Korean Integrated Model (KIM) is a global NWP model, which was developed in 2020 for the operational medium-range forecast at Korean Meteorological Administration. The Korea Institute Atmospheric Prediction Systems has a mission to improve KIM predictability for high-impact weather especially over the Korean Peninsula with an approach to increase resolution and advance physics parameterization. In this study, we evaluate heavy rainfall events simulated by KIM during summer 2022 by using both in-situ and remote sensing measurements. It is found that KIM simulates overall synoptic conditions for summer heavy rainfall events, which are characterized with upper level trough, low level jet, and migratory cyclones with North Pacific High located in the east of the Korean Peninsula. However, it also shows that precipitation prediction performance can be significantly affected by the simulated thermodynamic conditions by the model. Meanwhile, the model shows strong sensitivity to the cumulus parameterization scheme especially in events with an east-west rain belt passing from the West sea to the central part of Korea. The characteristics of the vertical structures of simulated rainfall events are further evaluated using remote sensing measurements to give comprehensive understanding to improve model predictability.
AS51-A011
Evaluation of the SMoothed Hybrid Sigma-pressure (SMH) Coordinate in KIM
Hae-Jin KONG1#+, Ja-Rin PARK1, Suk-Jin CHOI2, Hyun NAM1
1Korea Institute of Atmospheric Prediction Systems, Korea, South, 2Gangneung-Wonju National University, Korea, South
Various terrain-following vertical coordinates have been developed to mitigate the influence of the terrain structure in atmospheric numerical models. However, it still remains the problems in computing horizontal pressure gradients and advection along steep terrain surfaces. These small-scale structures can further promote artificial circulations as the model resolution increases. Choi and Klemp (2021) proposed the smoothed hybrid sigma-pressure (SMH) coordinate to reduce small-scale components more rapidly with height than basic sigma or hybrid sigma coordinates. The SHM coordinate is designed to flexibly control smaller scale of terrain influences with height by separating a reference surface pressure to smoothed and deviated parts. The performance of SMH coordinate was demonstrated in two-dimensional slice version of KIM through several idealized tests. Compared to the hybrid sigma coordinate, the SMH coordinate showed significant improvement in reduction of topographic features. This study examines the impact of the SMH coordinate in a full version of KIM. The SMH coordinate has potential to well control smaller scale of terrain features so that the model can be allowed to have less smoothing of the terrain in high resolution. With testing idealized experiments and real forecasts, the SMH performance will be discussed in terms of model stability and accuracy. Reference: Choi, S.-J., and Klemp, J. B., MWR, Vol. 149 (2021), 4077-4089. Acknowledgement: One of the authors, Suk-Jin Choi, wishes to acknowledge this study was supported by 2023 Academic Research Support Program in Gangneung-Wonju National University.
AS51-A012
Correcting Sub-daily Satellite Precipitation Based on GRU and TrajGRU in Taiwan
Hsiang-En TSOU+, Chia-Jeng CHEN#
National Chung Hsing University, Taiwan
The uneven spatiotemporal distribution of rain gauge data in Taiwan demands a need for a comprehensive gridded product that can be obtained from satellite observations, such as the Integrated Multi-satellitE Retrievals for Global satellite precipitation measurement (IMERG) product. However, IMERG still poses known biases and can sometimes be erroneous. In order to enhance the accuracy of satellite rainfall estimates, this study aims at applying two deep learning (DL) models, namely the Gated Recurrent Unit (GRU) model and the Trajectory Gated Recurrent Unit (TrajGRU) model, to correct IMERG Early and Final Run data in Taiwan at different sub-daily scales. Compared to traditional recurrent neural networks, GRU exhibits better model efficiency with a low memory usage, while TrajGRU incorporates a deformable convolution kernel able to effectively capture spatiotemporal features and improve predictive capabilities. Gauge data from Taiwan’s Central Weather Bureau are adopted as ground truth in the training and validation of DL models. Relative performance in the corrected IMERG products will determine the capabilities of the DL models as well as the limitation of time scales for such correction scheme.
AS51-A015
Pseudo Seeder-feeder Mechanism in Orographic Precipitation in a Typhoon Environment and its Response to Global Warming
Jianan CHEN#+, Xiaoming SHI
The Hong Kong University of Science and Technology, Hong Kong SAR
The intense winds in a Typhoon environment over mountainous regions can trigger strong convections and produce enhanced precipitation, yet few previous studies have been done in understanding how the orographic precipitation in a TC environment might respond to global warming. Here, we focus on this problem and use large-eddy simulation (LES) to estimate the global warming-induced response of precipitation over and near an idealized mountain with 10km half width and 1km height. Pseudo-global warming experiments are further conducted by adding mean thermodynamic structure changes predicted by a CMIP6 climate simulation. Two regions exhibit locally enhanced precipitation. One is over the mountain with rainfall maximum on the lee slope; the other is in the downstream region 30 to 50 km away from the mountain. Regression analysis suggests the enhanced precipitation in both regions are related to the seeder-feeder mechanism. Though the enhancement in the downstream regions differs from the conventional definition. Mountain waves generate an intense cloud formation center in the upper troposphere above the mountain, resulting snow and graupel drift downstream which intensify downstream convection when they fall into a proper height. This precipitation enhancement mechanism in the downstream region is called as Pseudo Seeder-Feeder Mechanism (PSF). Under global warming, the downstream enhanced region exhibits mean precipitation sensitivity ~18%/K which is significantly higher than the Clausius–Clapeyron (CC) scaling of ~7%/K of surface warming. This super-CC scaling in the downstream region is induced by both the precipitation efficiency and thermodynamic enhancement, of which the precipitation efficiency is the dominant factor. Additionally, the larger sensitivity in the downstream region is partially due to the upwind shift of the enhanced precipitation, which in turn is attributed to changes in the mountain wave patterns.
AS51-A017
Super-Clausius–Clapeyron Scaling of Tropical Cyclone Rainfall at Urban Scales
Xiaoming SHI#+
The Hong Kong University of Science and Technology, Hong Kong SAR
Accurate quantification of future extreme tropical precipitation is challenging because global climate models have insufficient resolutions to resolve convection. Yet reliable estimation is needed to prepare our society for the increasing risks of flooding and landslide as extreme rainfall is expected to intensify generally as the climate warms. Here, we combine deep learning (DL) and convection-permitting simulations to provide reliable estimations of the future change in extreme precipitation in South China. The DL model was trained to statistically downscale low-resolution climate model data and proved more effective in identifying extreme precipitation events than simply using global climate model rainfall. High-resolution (1km) downscaling simulations are conducted for DL-selected cases so as to verify DL prediction and provide a more accurate, physical modeling-based prediction of precipitation. We found that the sensitivity of extreme rainfall at the grid-point scale is close to the Clausius-Clapeyron (CC) scaling, around 7%/K. However, for large spatial scales and temporal accumulation, the sensitivity can be as high as 17%/K. Such accelerated response of extreme precipitation in the urban-relevant scales is found to result from more compact organizations of convective cores in tropical cyclones. Such super-CC scaling has important implications for future urban flooding and slope safety.
AS51-A021
Using Machine Learning to Analyze the Changes in Summer Extreme Precipitation in Southern China
Bojun WANG+, Wei WEI#, Zejiang YIN
Sun Yat-sen University, China
Convolutional neural network (CNN) is applied to identify the extreme precipitation in southern China in summer and the physical contributions are quantified for the interdecadal changes in the extreme precipitation. The CNN correctly identifies 93% of the observed extreme precipitation events based on the given large-scale atmospheric circulation through hyper-parameter optimization and model training. The discrimination made by the neural network is revealed by using the layer-wise relevance propagation method. The CNN is inclined to classify the circulation pattern as an extreme precipitation circulation pattern (EPCP) when the low pressure anomalies of sea level pressure and 500-hPa geopotential height appear in southern China. Both the extreme precipitation amount and the frequency of EPCP show significant interdecadal changes around the early-1990s. Result of the partition analyze indicates that the interdecadal increase in the extreme precipitation in the last three decades is mainly attributed to the dynamic influence of the increasing frequency of the EPCP. The thermodynamic effect of the increasing watervapor also plays an important role in the increase of both the extreme and non-extreme precipitation after the early-1990s.
AS52-A007
A Novel Hybrid Deep Learning Model for Predicting Ionospheric TEC Under Different Geomagnetic Conditions
Han WU1+, Ling HUANG1#, Hongping ZHANG2, Dezhong CHEN2, Yidong LOU2, Bin MA1, Xu LIU1
1Guilin University of Technology, China, 2Wuhan University, China
Aiming at the characteristics of high noise, nonlinearity and non-smoothness of ionospheric Total Electron Content (TEC) time series, this study constructs a combined short-term ionospheric TEC prediction model based on long short-term memory (LSTM) neural network model, incorporating singular spectrum analysis (SSA). The data of geomagnetic storm periods in high solar activity year and geomagnetic calm periods in low solar activity year are selected, and the trend component, period component and noise residual component of TEC time series are firstly extracted using SSA, and then the LSTM model is used to implement TEC prediction at different geomagnetic conditions and geographic latitudes. The results show that the relative accuracy of SSA-LSTM model is 91.17% and 95.46% respectively, which is 4.92% and 3.17% higher than that of single LSTM model, during the period of geomagnetic storm periods and geomagnetic calm periods.
AS52-A011
A Comparison of NmF2 Derived from Nighttime OI 135.6nm Emission to Ionosonde Measurements
Shixiang XUE, Chunhua JIANG#+
Wuhan University, China
It is well known that there is a strong correlation between the intensity of nighttime OI 135.6nm emission and the critical frequency of ionospheric F2 region (foF2). However, the relationship depends on the different longitudes and latitudes. In this study, an improved algorithm was developed to estimate foF2 from nighttime OI 135.6nm emission. The proposed method is suitable for different longitude, latitude, local time, season and solar activity. This study estimated foF2 from OI 135.6nm emission observed by the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instrument on board the Defense Meteorological Satellite Program (DMSP), and then the estimated results were compared with the results of ground-based ionosonde. Results show that the data with relative error less than or equal to 20% accounted for 92.99%, and the average relative error was about 7.08% during the high-solar activity year (2013). During the low-solar activity years (2017), the data with relative error less than or equal to 20% accounted for 80.76%, and the average relative error was about 12.64%. Furthermore, we discussed the possible reasons about the difference of retrieval accuracy of the algorithm during the high and low solar activity years.
AS52-A018
Estimation Model of Global Ionospheric Irregularities: An Artificial Intelligence Approach
Penghao TIAN#+, Jianfei WU
University of Science and Technology of China, China
The ionospheric sporadic E layer, the ionospheric irregularities of enhanced electron density, appears in the Earth’s ionosphere at altitudes between 90 and 120 km, which supports the real-world radio communication needs of many sectors reliant on ionosphere-dependent decision-making. The prediction of the occurrence of sporadic E layers has been extremely difficult due to the highly complex behavior. Conventional numerical methods are limited because of the inability to extract high-level information from data. Deep learning is a powerful tool for mining latent features from data, which can theoretically avoid assumptions constraining physical methods. Inspired by feature extraction, we applied deep learning to explore latent relationships between mapping observable lower atmospheric data and ionospheric data from limited observations. The proposed model was trained with high-resolution ERA5 data during Jan. 1, 2007-Aug. 30, 2018 as input and corresponding ionospheric sporadic E data collected from COSMIC RO measurements as output. The results show that the model can learn complex relevance as bridges connecting the input and the desired output and obtain excellent performance and generalization capability by applying multiple evaluation criteria. Additionally, we established several model architecture training methods to explore the performance of the model with different input data. The statistic results show that model inference performance is proportional to the abundance of input information and is impacted by intraseasonal variability. The inference capability of the model achieves the best performance in the Jun.-Aug. (JJA) and Dec.-Feb. (DJF) seasons, which is the exact period of sporadic E layer significant occurrence, although different models are evaluated.
AS56-A001
Impacts of Land Cover Changes on Biogenic Emission and its Contribution to Ozone and Secondary Organic Aerosol in China
Ma JINLONG1#+, Hongliang ZHANG1, Peng WANG2
1Fudan University, China, 2The Hong Kong Polytechnic University, China
The increase in vegetated areas in China led to increased biogenic volatile organic compounds (BVOC) emissions. As the important precursor for ozone (O3) and secondary organic aerosol (SOA), an increase in BVOC emissions will impact the formation of O3 and SOA. Thus, accurate estimation of BVOC emissions is critical to understanding their impacts on air quality. In this study, Model of Emissions of Gases and Aerosols from Nature (MEGAN) v2.1 was used to investigate the impact of different leaf area index (LAI) and land cover (LC) datasets on BVOC emissions in China in 2016 and the effects on O3 and SOA were evaluated based on the Community Multiscale Air Quality Modelling System (CMAQ). Three LAI satellite datasets of the Global LAnd Surface Satellite (GLASS), the Moderate Resolution Imaging Spectroradiometer (MODIS) MOD15A2H version 6 (MOD15), and the Copernicus Global Land Service (CGLS), as well as three LC satellite datasets of the MODIS MCD12Q1 LC products, the Copernicus Climate Change Service (C3S) LC products, and the CGLS LC products were used in five parallel experiments (cases: C1-C5). Results show that changing LAI and LC datasets of the model input has an impact on BVOC estimations. BVOC emissions in China range from 25.42 to 37.39 Tg in 2016. Changing the LC inputs for the MEGAN model has a more significant difference in BVOC estimates than using different LAI datasets. Besides the impact on BVOC emissions, changing the MEGAN inputs further impacts the concentrations of O3 and SOA. The highest O3 and biogenic SOA (BSOA) concentrations appear in the C1 (using GLASS and MCD12Q1 LC) simulation, which can reach 12 ppb and 9.8 μg m-3, respectively. Due to the effect of BVOC emissions, the relative differences between C1 and C4 are over 52% and 140% in O3 and BSOA in central China.
AS56-A007
Effects of Temperature on Biogenic VOCs Emissions and its Contributions to Ozone Formation in Pearl River Delta
Hao GUO1#+, Yanli ZHANG1, Xinming WANG2
1Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, China, 2Chinese Academy of Sciences, China
Ozone (O3) pollution is influenced by a combination of NOx and VOCs emissions. The biogenic volatile organic compounds (BVOC) emitted from plants could be an important source and the production is significantly impacted by temperature changes. This study will investigate the effects of temperature on Biogenic VOCs emissions and its contributions to ozone formation in Pearl River Delta in summer, 2022 using Model of Emissions of Gases and Aerosols from Nature (MEGAN) and the Community Multi-scale Air Quality (CMAQ) model. The meteorology will be generated using Weather Research and Forecasting (WRF) model version 3.9.1 and biogenic emissions will be generated based on MEGAN version 2.4 with two scenarios: base case and temperature increased 2K case. The differences in spatial variations of biogenic emissions, ozone concentrations and SOA concentrations between two scenarios will be analyzed. The results show a significant increase in BVOC emission (24%) and ozone concentrations (~2 ppb) with 2K increase of temperature in Pearl River Delta in summer, 2022. BVOC emissions are highly sensitive to the temperature changes, and we need to adjust our air pollution control strategy based on temperature effects especially in Pearl River Delta.
AS56-A011
Molecular Composition of Secondary Organic Aerosol from α-pinene Ozonolysis Affected by Relative Humidity
Hao LUO+, Yindong GUO, Hongru SHEN, Defeng ZHAO#
Fudan University, China
Biogenic volatile organic compounds (BVOC) can contribute a significant fraction to secondary organic aerosols (SOA) through atmospheric oxidation, which plays a critical role in climate change and human health. The ozonolysis of α-pinene, one of the most important BVOCs, is a canonical SOA system. At present, the effects of relative humidity (RH) on SOA composition from α-pinene+O3 reaction are still unclear. In this study, we report the SOA composition on molecular level formed in α-pinene+O3 reaction under various RH. The SOA components were measured by an Extractive ElectroSpray Ionization inlet coupled with a long Time-of-Flight Mass Spectrometer (EESI-TOF-MS). We observed RH-dependent SOA chemical composition, including larger contribution of monomer products with increasing RH, although the total O:C remained largely unchanged. The effect of RH may be attributed to the particle-phase reactions of SOA components. This study highlights the necessity of characterizing SOA composition on molecular level and of considering RH dependence of SOA chemical composition and it physicochemical properties in atmospheric models.
AS56-A013
Unexpected Significance of a Minor Reaction Pathway in Daytime Formation of Biogenic Highly Oxygenated Organic Compounds
Hongru SHEN1+, Luc VEREECKEN2, Sungah KANG2, Iida PULLINEN2, Hendrik FUCHS2, Defeng ZHAO1#, Thomas MENTEL2
1Fudan University, China, 2Forschungszentrum Jülich, Germany
Secondary organic aerosol (SOA), formed by oxidation of volatile organic compounds, significantly influence air quality and climate. Highly oxygenated organic molecules (HOM), particularly those formed from biogenic monoterpenes, play a key role in their formation and growth. As the most important daytime oxidant, hydroxyl radical (OH) initiated HOM from monoterpenes is believed to be mainly formed via the OH addition channel. However, for α-pinene, the most abundant atmospheric monoterpene, we found that the minor hydrogen abstraction channel is underappreciated in the HOM formation. We will present our observations and theoretical calculations, showing the role of hydrogen-abstraction and alkoxy radicals for fast autoxidation leading to HOM. We also provide a mechanism and yield, suggesting the non-negligible contribution of the hydrogen abstraction channel to ambient SOA, particularly in OH rich areas.
AS57-A002
A Method to Retrieve the Refractive Indices and Mineral Components of Dust Aerosols from Satellite Infrared Hyperspectral Data
Senyi KONG#+, Lei BI
Zhejiang University, China
Dust aerosols exert an enormous influence on human health, global weather, and climate due to their large mass loading and wide spatial distribution. A large uncertainty still exists in quantitatively assessing the impact of dust aerosols on radiative transfer and climate simulation, which can partly be attributed to the complex refractive indices of dust. The complex refractive indices of dust are related to mineral composition. However, the mineral composition of dust is manifold and varies with dust origins, which results in sampling limitations in the experimental measurement of the complex refractive indices of dust and the contents of mineral components. In response to this problem, this study has obtained the complex refractive indices and the contents of the mineral composition of dust aerosols from satellite data by utilizing the mineral composition characteristics in the infrared band. The results showed that the retrieved complex refractive indices were higher than the experimental reference values, while the retrieved contents of mineral components were in good agreement with the experimental measurements.
AS57-A004
Assessment of the Inhomogeneity and Nonsphericity Effect of Internally Mixed Aerosols in the Chemical Weather Prediction Model
Xuan WANG+, Lei BI#
Zhejiang University, China
In order to represent aerosols for radiative transfer simulations in the atmospheric model, we developed an internally-mixed aerosol scheme in which both particle nonsphericity and inhomogeneity effect were considered. In this scheme, black carbon was assumed to be fractal and soil dust was modeled as super-spheroid. These two insoluble aerosols (black carbon and soil dust) were partially coated with hygroscopic aerosols such as sulfate, nitrate, and aerosol water. The aerosol hygroscopic growth and composition variations were parameterized. Then, we built a database of the optical properties for the aforementioned models using the Invariant Imbedding T-Matrix Method(IITM). In addition, deep neural networks (DNN) were trained based on the database. We found that the DNN can predict the optical properties of aerosols efficiently and accurately. With these efforts, the aerosol-optics scheme was implemented into the Global/Regional Assimilation and Prediction System with Chinese Unified Atmospheric Chemistry Environment (GRAPES/CUACE). Two case studies were performed in East Asia on the summer and winter of 2020. Compared to the uniform and spherical aerosol scheme, the inhomogeneity and nonsphericity effect caused negative radiative forcing on the surface and positive radiative forcing on the top of atmosphere (TOA), enhancing the solar heating rate. The surface was cooler and the air beyond the boundary layer was warmer. Thus, the boundary layer was found to be more stable, leading to less precipitation and lower boundary layer heights. Finally, the meteorological and optical profiles computed from the GRAPES/CUACE were implemented in the RTTOV (Radiative Transfer for TOVS). The simulated solar reflectance on the TOA was compared with observations from the FY-4A satellite. We found that the comparisons were improved when the inhomogeneity and nonsphericity effect of aerosols were incorporated.
AS57-A005
Hourly Assimilation of Himawari-8 Cloud Optical Depth Using Four-dimensional Local Ensemble Transform Kalman Filter Over the Tibetan Plateau
Tianyu ZHANG#+
Aerospace Information Research Institute,Chinese Academy of Sciences, China
It is a challenge for improving the simulation effect of thick clouds over the Tibetan Plateau due to the rapidly and deeply cloud convection occurs frequently in summer. A cloud optical thickness assimilation system is developed by introducing Four-Dimensional Ensemble Kalman Filter theory (4D-LETKF) which establishing the covariance relationship between 2D cloud optical thickness and 3D cloud water content and taking advantage of the high spatial and temporal resolution of the next generation of geostationary satellites. A typical simulation case of convective clouds in summer is carried out over the Tibetan Plateau using the new assimilation system. The cloud optical thickness is assimilated hourly from the next generation data of Himawari-8 satellite to correct the cloud water mixing ratio in the WRF model. The assimilation significantly improves the simulation accuracy of cloud optical depth on thick clouds which solves the problem that the assimilation effect is weak on thick clouds in the existing cloud assimilation system. Using Himawari-8 satellite data as the true value for effect evaluation, the new assimilation scheme can improve the accuracy of cloud optical thickness correlation coefficient by 34% after the assimilation.
AS57-A006
A Machine-learning-based Cloud Top Pressure Retrieval by Synergistically Using Polarized and O2 A-band Measurements from GF-5 and PARASOL
Lesi WEI#+, Huazhe SHANG, Husi LETU
Chinese Academy of Sciences, China
Cloud top pressure (CTP) is a critical cloud property that significantly affects cloud radiation. Multi-angle polarization-based sensors can employ polarized bands (490 nm) or O2 A-bands (763 and 765 nm) to retrieve the CTP. However, the CTP retrieved by the two methods shows inconsistent results in certain cases, and large uncertainties in low and thin cloud retrievals may negatively affect subsequent applications. This study proposes a synergistic algorithm that appends both O2 A-bands and polarized bands using a random forest (RF) model. LiDAR CTP data are used as the sample true values, and polarized and non-polarized measurements are concatenated to train the RF model of CTP. Additionally, through analysis, we discovered that the polarized signal is saturated with increasing cloud optical thickness (COT), thus necessitating a special treatment for COT intervals <10 to improve the stability of the algorithm. We then applied the synergistic method to directional polarized camera (DPC) and Polarized and Directionality of the Earth’s Reflectance (POLDER) measurements for evaluation, and the validation accuracy and retrieval accuracy of the POLDER-based measurements (RMSE=121.431 hPa, R2=0.827 and RMSE=30.611 hPa, R=0.470, respectively) were higher than that of the MODIS and POLDER Rayleigh pressure measurements. Moreover, POLDER also showed good performance relative to DPC. This algorithm is expected to provide data support for atmosphere-related fields as an atmospheric remote sensing algorithm in the Cloud Application for Remote Sensing, Atmospheric Radiation and Updating Energy (CARE) platform.
AS57-A008
Characterization of the Size-resolved Morphology for Black Carbon Particles During Atmospheric Aging
Yan PENG#+, Xiaofeng HUANG, Jing WEI, Ling-Yan HE
Peking University Shenzhen Graduate School, China
The morphology of black carbon (BC) plays an important role in the determination of its aging scale and constraining its radiation effect. Therefore, it is urgent to characterize the distribution and evolution of observational-based morphology of BC-containing particles during atmospheric aging. In this study, a tandem differential mobility analyzer–single-particle soot photometer (DMA–SP2) system was used to estimate the size-resolved effective density (ρeff) of atmospheric BC-containing particles. The results show that there are differences in the morphology evolution with different BC core diameters (Dc) during the emitted-to-age process. With less coating materials, the small Dc particles (100-120 nm) tend to be spherical (ρeff = 1.31-1.33 g cm-3) while the large Dc particles (280-300 nm) are fractal (ρeff = 0.95-1.08 g cm-3). During atmospheric aging, the non-BC materials dominate the ideal growth of particle diameter for small Dc particles, while used to fill the void for large Dc particles and cause the collapse of the fractal branches. Furthermore, this study classified the BC-containing particles into two groups, i.e., near-spherical and non-spherical particles. For the first time, we calculated and parameterized the coating-to-BC mass ratio (MR) of the shape transition points as a function of Dc and the mean aging state of BC-containing particles. After considering this parameterization, compared with the core-shell prediction, there are ~ 18% reductions for calculated absorption cross section over the entire population. This study highlights that the strong dependence of the ρeff and shape transition MR point of atmospheric BC-containing particles on Dc can improve the representation of its morphology in the global climate model and reduce uncertainty in the evaluation of BC climate effects.
AS57-A014
A Precipitation Estimation Method by Considering Clouds Microphysical Parameters Based on Observations from Geostationary Satellite
Dabin JI#+, Husi LETU, Jiancheng SHI
Chinese Academy of Sciences, China
Real time precipitation is an important parameter in flood forecast. Geostationary satellites which have real time observations at visible and infrared bands with high spatial and temporal resolution provide a good way to estimate precipitation. A lots of precipitation estimation algorithms have been developed for geostationary satellites. Cloud top information which includes cloud top reflectivity, cloud top brightness temperature, gradient of cloud top brightness temperature and motion vectors of cloud top was usually used to retrieve precipitation in these precipitation estimation algorithms. However, it is hard to accurately select precipitation pixels from non-precipitation clouds only based on cloud top information. In this study, a new real-time precipitation estimation method for geostationary meteorological satellite Himawari-8 considering cloud microphysical parameters was proposed. Besides the cloud top information, the cloud microphysical parameters including cloud effective radius and cloud optical depth in both day and night were used in the new precipitation recognition method to improve the accuracy of precipitation identification. Based on the identified precipitation area, the cloud top brightness temperature and cloud liquid water path which was calculated from cloud effective radius and cloud optical depth were used to build a dynamic calibrating model to estimate the rainfall rate by taking the GPM-IMERG early run precipitation product as reference. The estimated rainfall rate was further calibrated using rain gauge observations on hourly scale. According to the validation using independent hourly rain gauges observations over Chinese mainland in summer, the probability of detection (POD) of the real-time estimated precipitation can reach up to 0.7, and the false alarm ratio (FAR) is lower than 0.6. From the aspect of precipitation identification, the accuracy of the newly developed precipitation algorithm has a obvious improvement compared with that of the GSMaP_NOW over Chinese mainland.
AS59-A003
Characteristics of Intracloud Lightning to Cloud-to-ground Lightning Ratio in Thunderstorms Over China
Yushu REN#+, Weixin XU
Sun Yat-sen University, China
The intracloud (IC) to cloud-to-ground (CG) lightning ratio (IC:CG ratio) provides not only essential information for extrapolating IC flashes from the continuously monitored CG activities but also important implications for the kinematic and microphysical structures of thunderstorms. This study examines the IC:CG ratio climatologies in China and seeks the underlying reasons responsible for regional variations on IC:CG ratios. Analyses are based on both grid-scale (2 degree) and thunderstorm-scale (convective feature), using coincident observations from TRMM LIS (total flash) and the China Lightning Detection Network (CG lightning) during 2009-2014. National mean IC:CG ratios in China are about 3-5, consistent to those reported in other regions around the world. However, Guangxi Province (GXP) and Sichuan Basin (SCB) have exceptionally high (> 10) and lower-than-average (< 2) IC:CG values, respectively. While the IC:CG in GXP significantly maximizes in the spring season and diurnally peaks in the morning, SCB exhibits virtually no seasonal nor diurnal variation on IC:CG. The contrasting IC:CG ratios between GXP (~7.5) and SCB (~2.5) are also found on the storm scale. Thunderstorms in GXP have a much lower CG flash rates than those in SCB, even though they share a similar total flash rate, resulting in a far higher IC:CG in GXP. All convective proxies indicate that SCB has a higher likelihood in producing CG flash than GXP under the same convective intensity. In addition, the CG flash rate in SCB increases much more rapidly with the increase of total flash rate or convective intensity. The underlying mechanisms for regional variations on IC:CG may be associated with storm morphology, microphysical property, and/or convective environments, which will be further investigated.
AS59-A004
A High-resolution Numerical Simulation of the “7.19” Extraordinary Heavy Rainfall in Henan Province Under Topographic Effect
Xinmin WANG#+
Xiamen Key Laboratory of Straits Meteorology, China
In this study, based on the ERA5 dataset, the orographic precipitation characteristics during an extraordinary heavy rainfall event in Henan Province on July 19, 2016 are analyzed. Besides, by using WRF, a high-resolution numerical simulation is carried out, including a series of sensitivity experiments on the Taihang Mountains, the Yunmeng Mountain and low-altitude areas. The distribution of observed precipitation shows that the precipitation over the Taihang Mountains in northern Henan during the daytime of July 19 is significantly enhanced due to the topographic effect compared with that over the plain on the east. The simulation results demonstrate that the distribution of simulated precipitation over the steep terrains on the east side of the Taihang Mountains is closer to the observational precipitation when SRTM-90m is introduced to the WRF model. When the altitude of the Taihang Mountains is lowered by 50%, the accumulated precipitation along the Taihang Mountains in the daytime of the 19th decreases by 26%, accompanied with the northward movement of the heavy precipitation center over the northern Taihang Mountains. Besides, the Yunmeng Mountain plays an important role in blocking or diverting the easterly and southeasterly low-level jet. When the terrain elevation of the Yunmeng Mountain is reduced, the convergence zone of the wind field in the low-level moves to the areas along the Taihang Mountains, which leads to the expansion of the area with heavy rainfall, with the average accumulated precipitation in mountain areas increasing by 7%. Besides, When the low-altitude terrain in the study region is reduced by 50%, the center of heavy precipitation moves westward obviously. Combined with the diagnostic analysis of the topographical forced vertical velocity, the results show that the uplift of low-level jet caused by the low-altitude terrain is one of the reasons that affect the location of heavy rainfall center.
AS59-A010
Analysis of Environmental Field Characteristics of Convective Initiation Triggered by Thunderstorm Gust Fronts in Beijing Area
Na HE1#+, Xiaoding YU2, Qinglan DING3, Xian XIAO2, Nan XING4, Ke LIU5
1Beijing Weather Forecast Center,Beijing Meteorological Service, China, 2China Meteorological Administration, China, 3Beijing Weather Forecast Center, China, 4Beijing Meteorological Service, China, 5North China Aviation Administration, China
In order to enhance the understanding of the environmental field characteristics of the convective regeneration triggered by thunderstorm gust fronts. Based on Beijing sounding observation, automatic stations, S-band Doppler radar and new detection data to analysis environmental field characteristics of two typical cases in which convection initiation triggered by thunderstorm gust fronts. The results show that: (1) One type is convection triggered by collision of multiple gust fronts or the encounter of gust fronts with other boundary layer convergence lines in the region with high Convective Available Potential Energy (CAPE) and sufficient water vapor (collision triggering). In this type, the vertical velocity of two collision gust fronts is much larger than that of a single gust front. Strong upward movement is easy to provide good lifting conditions for the triggering of convection, and convection is easy to trigger. (2)The other type is the gust front triggers convection in the unstable region (non-collision trigger). In this type, the low-level wind direction is perpendicular to the gust front, which is conducive to the strong convergence between the ambient wind near the ground and the gust front. Meanwhile, the updraft of the convection triggered by the gust front tends to be vertical, which is beneficial to convective initiation. (3)By comparing the environmental field of gust fronts trigger and non-trigger Convective Initiation (CI) cases, the results show that there are deep wet convection potential with high CAPE and low Convective Inhibition (CIN) of the environment field in these cases which CI are triggered by gust fronts. There are cold dry advection at the upper level and warm wet advection at the lower level in most cases CI triggered by the gust fronts, which also happened at the wind speed or wind direction convergence areas with high CAPE.
AS59-A013
Impact of Boundary Layer Jets on Cold Pool Characteristics During the Pre-summer Rainy Season in South China
Dong FU#+, Yu DU
Sun Yat-sen University, China
The South China Sea frequently experiences boundary layer jet (BLJ) events, which are closely related to the coastal rainfall of South China during the pre-summer rainy season. The gust front associated with the cold pool can interact with the low-level vertical wind shear, potentially affecting convection. The BLJ with a unique vertical wind shear may also interact with the cold pool, but the nature of this interaction is yet to be fully understood. The present study uses data from 356-m high Shenzhen Met-Tower to analyze the statistical characteristics of cold pools and investigate how these characteristics vary between BLJ- and nonBLJ- related cold pools. A total of 54 cold pools were observed by Shenzhen Met-Tower from April to June during 2018-2020, which included 26 BLJ-related cold pools and 28 nonBLJ-related cold pools. Results showed that the BLJ-related cold pools had a weaker temperature drop and less pressure increase compared to the nonBLJ-related cold pools, but their structure were deeper, greater specific humidity decrease and recovery was faster. The BLJ-related cold pools caused the decreases of relative humidity in the upper levels but increases in the lower levels. In contrast, both the upper and lower layers of the nonBLJ-related cold pools showed an increase in relative humidity. It is found that BLJ-related cold pools moved faster and were affected by the type of convective systems. The BLJ-related cold pools associated with mesoscale convective systems are deeper, longer-lasting, and had less pressure increase and more specific humidity reduction than those associated with convective cells.
AS59-A014
Using Polarimetric Radar Observations to Characterize First Echoes of Thunderstorms and Nonthunderstorms: A Comparative Study
Chuanhong ZHAO1#+, Yijun ZHANG2
1Chengdu University of Information Technology, China, 2Fudan University, China
This work compares the characteristics of the first echoes of thunderstorms and nonthunderstorms retrieved from S-band polarimetric radar observations. Observations of 57 (39) isolated thunderstorm (nonthunderstorm) cells with roughly equivalent aerosol and water vapor conditions but different convective available potential energy were obtained with a S-band polarimetric radar and three independent lightning location systems during 2016/2017 in southern China. Storms with the first echoes were divided into three types based on echo top heights, namely, type 1 (below 0°C layer), type 2 (0°C to −10°C), and type 3 (above −10°C layer). Our observations show median values of radar reflectivity (ZH) and differential reflectivity (ZDR) of type 1 and type 2 in warm phase layer (below 0°C layer) are obviously greater in nonthunderstorms than in thunderstorms, but this feature is not significant in type 3 storms. In the mixed 1 phase layer (0°C to −10°C), median ZH in type 2 is greater in nonthunderstorms while median ZDR in type 3 is slightly smaller. In the mixed 2 phase layer (−10°C to −38°C), median ZH is greater in thunderstorms while median ZDR is smaller, and ZDR values in nonthunderstorms are closer to zero. Although results of ZDR comparisons in the mixed phase are likely affected by random errors and/or residual bias errors, these different signatures suggest different characteristics of liquid or ice particles between thunderstorms and nonthunderstorms. This study is expected to advance our understanding of physical processes responsible for the generation of the first flash.
AS59-A016
Climatic Interactions Between Cold Surges and North Pacific Extratropical Cyclones—in the Perspective of Cold Surges
Lan XIA#+, JIalin ZHANG, Yao HU
Yunnan University, China
Cold surge events are divided into four types depending on their correlation with North Pacific extratropical cyclones. Climatologic relationships between the two phenomena reveal that 92% (39%) of all cold surges are accompanied by extratropical cyclones (explosive extratropical cyclones), while 31% of extratropical cyclones are accompanied by cold surges. The occurrence and development of extratropical cyclones favor eruptions of cold air from higher latitudes, which in turn produce conditions conducive to cold surges. In the North Pacific, extratropical cyclones travel in a northeastward direction, ultimately contributing to the Aleutian low. Meanwhile, the westerly jet is observed to strengthen following cold surge events. Both actions drive further extratropical cyclone activity, which in turn facilitates subsequent cold surges. Therefore, when extratropical cyclones occur before and after cold surges, the cold surge event itself tends to be relatively strong and long-lived. The transmission of energy by extratropical cyclones is a primary link between the high and middle latitudes, and contributes to the impact of cold surges on low latitudes. This study also explores the respective influences of the Siberia High and Aleutian Low on cold surges.
AS59-A022
Machine Learning Approach for Prediction of Lightning Probability in the Warm Season
Kyuhee SHIN1+, Kwonil KIM2, Si-Hyeon SON1, Gyu Won LEE1#
1Kyungpook National University, Korea, South, 2Stony Brook University, United States
Lightning affects significant hazards to society directly or indirectly, such as by striking individuals, causing damage to electrical infrastructure, and disrupting transportation systems. Accurate prediction of lightning is crucial for forecasters to respond effectively to its imminent occurrence. Lightning usually occurs in convective storms, which develop rapidly and occurs in a narrow area. This causes difficulties in predicting their location using numerical weather prediction (NWP). Lightning occurrence is often predicted by utilizing thermodynamic parameters (K index, CAPE, Lifted index, etc.). A high-resolution NWP model provides a prediction of thermodynamic variables at high spatiotemporal resolution with high accuracy for a few hours. However, a complicated algorithm is required to handle all the useful high-resolution variables from the NWP model. Recently emerging machine learning (ML) technique can solve this issue because it properly handles these “big data” without any model distributional assumption.
In this study, we have examined the capability of the use of “random forest” (RF) in the prediction of lightning probability for 3 years (2020–2022) of the warm season (June to August). The RF was trained by a lightning occurrence as a predictand and characteristic parameters from the NWP as predictors. The precision of RF was higher than 0.9 for lightning and higher than 0.85 for non-lightning, respectively. The trained RF was applied to the independent analysis and forecast fields and showed high agreement with the observation, suggesting that the trained model had the potential to assist forecasters in improving their lightning forecasting skills using real-time probabilistic forecasts from the trained model.
ACKNOWLEDGEMENT
This work was funded by the KMA Research and Development Program “Observing Severe Weather in Seoul Metropolitan Area and Developing Its Application Technology for Forecasts” under Grant (KMA2018-00125). This work was supported by the NRF of Korea grant funded by the Korea government (MSIT) (No. 2021R1A4A1032646).
AS01-A002
Intraseasonal Oscillation and the Taiwan Climate
Chih-Wen HUNG#+
National Taiwan Normal University, Taiwan
It is known that the eastward moving Tropical Intraseasonal Oscillation (TISO) has impact on the climate over the Asian-Australian monsoon region. This study summarizes that the TISO can have the impact on the Taiwan climate in the onset of the Meiyu season and the summer and winter monsoon rainfall. For the onset of the Meiyu in Taiwan, it is found that for almost half of the cases, the first transition of the Asian summer monsoon can be classified as a sharp onset, which is occurred with an eastward-propagating TISO from eastern Africa and the western Indian Ocean to the Maritime Continent. This efficient and persistent transport of moisture presumably provides a favorable condition for the maintenance of the Meiyu front and marks the onset of the Taiwan Meiyu season. Following the Meiyu, during the summer, the TISO can be represented by the boreal summer intraseasonal oscillation (BSISO) better. Our results found that the BSISO and the associated horizontal patterns of the western North Pacific typhoon frequency are closely related. Taiwan has larger rainfall when the major BSISO convection moves northwestward from the Philippine Sea to the Taiwan area. The anomalous low-level cyclonic flow and the increased typhoon frequency directly result in the larger rainfall in Taiwan. The enhanced low-level southwesterly flow which transports the moisture to Taiwan is responsible for more summer rainfall in Taiwan. On the other hand, during the winter season, the rainfall in Taiwan is also related to the TISO. The results show that Taiwan has larger rainfall when TISO reaching the Indian Ocean and the western part of the Maritime Continent, and less rainfall when it moves to the western Pacific warm pool area. The mechanisms suggested by this work are: (1) Tropics to mid-latitude wave train and (2) Increase of moisture supply from South China Sea.
AS01-A019
Influences of Tropical Pacific and North Atlantic SST Anomalies on Summer Drought Over Asia
Jianmin ZHANG+, Renguang WU#
Zhejiang University, China
Droughts can cause enormous damage to agriculture, ecosystems and socio-economics because of their longevity and widespread spatial extent. As a densely populated region in the world and with a large area of arid and semi-arid regions, Asia is largely affected by droughts, especially in summer. The drought variations are determined by precipitation that affects water supply and temperature that affects water depletion through surface evaporation. In this talk, we will present an analysis of contributions of precipitation and temperature to the spatial patterns and temporal variations of summer drought over Asia measured by 3-month Standard Precipitation Evaporation Index (SPEI03) in July and the factors for year-to-year variations of summer drought. We will perform numerical experiments with the Community Earth System Model (CESM) to explore the influences of different regional SST anomalies on summer drought in Asia. Our results show that the July SPEI03 displays a north-south dipole distribution across approximately 30°N, which is dominated by interannual component. Precipitation and temperature both contribute to the summer drought variations over Asia. Asian drought in summer is associated with both the tropical Pacific and North Atlantic SST anomalies. Preceding tropical Pacific SST anomalies influence the summer Asian drought via the large-scale divergent fows and soil moisture-evaporation feedback. The North Atlantic SST anomalies influence the Asian drought through atmospheric wave trains over the North Atlantic-Eurasia.
AS01-A029
Increase in Intraseasonal Rainfall Driven by the Arabian Sea Warming in Recent Decades
Baosheng LI1#+, Lei ZHOU2, Jianhuang QIN3
1Ministry of Natural Resources, China, 2Shanghai Jiao Tong University, China, 3Hohai University, China
The changes in the spatial distribution of Indian summer monsoon (ISM) rainfall pose significant risks of extreme weather events in the Indian subcontinent and Arabian Peninsula. Monsoon intraseasonal oscillation (MISO) plays a key role in the intraseasonal distribution of the ISM rainfall, and changes in MISO determine the ISM rainfall patterns in the warming climate as well. However, the trend in MISO remains unclear in recent decades. Here, we find that the variance of MISO has an increasing trend from 1982 to 2017 over the northeastern Arabian Sea (AS), accompanied by increasing intraseasonal rainfall. The enhancement in rainfall is mainly nourished by the increasing moisture supply. Accordingly, the intraseasonal moisture budget diagnosis suggests that the changes in vertical moisture advection dominate the increasing amount of moisture over the northeastern AS. In contrast, the horizontal moisture advection and moisture processes associated with condensational heating exhibit a decreasing trend. By further decomposing the timescales, the upward advection of background moisture by intraseasonal vertical wind velocity is the main contributor. Given sufficient moisture availability, the changes in the intraseasonal vertical velocity are more important than the background moisture, which is a response to the strengthening of intraseasonal convergence in the PBL. Moreover, the faster warming of the AS and the increasing cyclonic vorticity associated with the poleward movement of the summer mean low-level jet are responsible for the increasing trend in PBL convergence. Thus, the MISO accompanying the intraseasonal rainfall displays an increasing trend over the northeastern AS. This recent intensified intraseasonal rainfall has contributed to the trend in the mean and extremes over the central-western parts of the Indian subcontinent. The results could assist the understanding and better projections of spatial pattern of rainfall during the ISM.
AS01-A030
Connections Between ENSO and Tibetan Plateau Snow Cover
Zhibiao WANG#+
Chinese Academy of Sciences, China
El Niño–Southern Oscillation (ENSO) and the Tibetan Plateau snow cover are important factors in interannual climate variability. The relationship between ENSO and the Tibetan Plateau snow variation is still undetermined. While some studies suggested that ENSO is a key factor of changes in snow cover over the Tibetan Plateau, other studies noted independence between the two. The present study revealed a prominent interdecadal change in the relationship between ENSO and the spring Tibetan Plateau snow-cover variation in the early 2000s. There is a significant positive correlation between ENSO and the spring Tibetan Plateau snow-cover variation in the period 1988–2003, but an obvious negative relationship is detected in the period 2004–19. The interdecadal change in the ENSO–snow relationship is related to the distinct pathway of ENSO influence on the spring Tibetan Plateau snow-cover variation during the two periods. In the period 1988–2003, ENSO induces anomalous convection over the tropical western North Pacific that in turn causes atmospheric circulation and moisture anomalies over the Tibetan Plateau. The resultant winter snow anomalies over the central-eastern Tibetan Plateau persist to the following spring. In the period 2004–19, ENSO induces North Atlantic sea surface temperature (SST) anomalies in winter that are maintained to the following spring. The North Atlantic SST anomalies then stimulate the atmospheric circulation anomalies extending to the Tibetan Plateau that induce snow-cover anomalies there in spring. The different processes of ENSO influence lead to opposite anomalies of spring snow cover over the Tibetan Plateau in the two periods.
AS01-A033
The Role of C-shape Tropical Land in Forming Asian Summer Monsoon
Xinyu WEN#+, Junyu MEI
Peking University, China
The topographic effect of lands on monsoonal climate variability is one of the key topics in monsoon dynamics studies. Here, we re-visit the topographic effect of varying-shaped lands on Asian monsoon formation using a fast AGCM with a large number of experiments. It is found that the C-shaped continent located over the tropics and subtropics favors a distinct Asian summer monsoon pattern most. The preliminary results show that the C-shape land creates more evident monsoonal responses than other shape lands through three key processes, including intensified cross-equatorial winds, water vapor convergence along with subtropical monsoonal troughs, and one significant low-pressure departure near the southeast corner of the NH land. We would like to show more detailed results derived from our numerical experiments, which help to improve our understanding of monsoon formation and variability.
AS01-A038
Low-level Jet Observed Over the East China Sea During the Bai-u Season
Megumi NOGUCHI1, Noriyuki NISHI2#+, Atsuyoshi MANDA3
1Japan Meteorological Agency, Japan, 2Fukuoka University, Japan, 3Mie University, Japan
Water vapor flux in the lower troposphere controls the occurrence of heavy rain in the Bai-u season. The strong wind as well as enough humidity is essential to enhance the flux. We analyzed the remarkable south-westerly strong wind zones whose maxima are present below 900 hPa over the central East China Sea during the Bai-u season. Our definition of a “strong wind zone” is that the maximum wind speed within the layer below 900 hPa is greater than 15 ms-1 and the wind speed decrease is larger than 3 ms-1 from the 900-hPa level up to the 700-hPa level. The zones have a maximum occurrence rate from the end of June to the beginning of July over the central Eastern China Sea. We focused on the events in which the geostrophic component has remarkable shear above the wind speed peak below 900-hPa. Most of them are detected far from low-pressure systems and Bai-u front and are not directly included in them. We showed that warm air advected by the rather strong westerly inherent to this season over the heated Asian continent and cold air above the ocean made the steep zonal temperature gradient, which strengthens vertical shear through the thermal wind relation. The mechanism is similar to the coastal jet resulting from the land-sea thermal contrast (e.g. Tu et al. 2018) except for the large distance (several hundred kilometers) from the continent. The occurrence rate of the strong wind zone has a maximum (minimum) at 02LT (20LT); this diurnal cycle was synchronized with the strength of the southerly ageostrophic wind near the surface reported in some previous studies. The combination of the geostrophic component produced through thermal wind relation and ageostrophic one inherent to the East China Sea produces a very strong jet structure.
AS01-A039
Impact of Ural Blocking on Sub‑seasonal Siberian Cold Anomalies Modulated by the Winter East Asian Trough
Yuanyuan SONG1#+, Dehai LUO2, Fei ZHENG2, Yao YAO2
1Institute of Oceanology, Chinese Academy of Sciences, China, 2Chinese Academy of Sciences, China
This paper examines the impact of Ural blocking (UB) on winter sub-seasonal Siberian cold anomalies under the different background conditions of the winter East Asian trough (EAT). It is found that the meridional displacement and the strength of the winter EAT possibly modulate the persistence or lifetime of UB and associated sub-seasonal cold anomalies over Siberia through changing background circulation conditions. Statistical analysis reveals that UB events tend to occur more frequently in strong or southward EAT winters than in weak or northward EAT winters. A composite analysis of UB events further shows that UB has larger amplitude and longer lifetime in strong or southward EAT winters (especially the latter) than in weak or northward EAT winters, thus more likely leading to stronger sub-seasonal cold anomalies over Siberia. Moreover, the possible physical cause of why a strong or southward EAT favors UB is further investigated. It is found that winter zonal wind and meridional gradient of potential vorticity (PVy) tend to be weakened on the upstream side of Siberia near the Ural Mountains when the EAT is stronger or located more southward, favoring the maintenance of UB due to the strengthening (weakening) of the nonlinearity (energy dispersion) of UB. In contrast, when the EAT is weak or northward-displaced, a strengthening of winter zonal wind and PVy is more likely seen over the Ural Mountains and adjacent regions, which may suppress UB through enhancing its energy dispersion and reducing its nonlinearity.
AS01-A048
Characteristics of Atmospheric Circulation Patterns Associated with the Long-duration of Heat Waves in South Korea
Minjeong CHO+, Ha-Rim KIM, Yong-Sang CHOI#
Ewha Womans University, Korea, South
Global warming has contributed to the recent increase in heat waves, which have become more intense, frequent, and longer lasting. Furthermore, heat waves that last for a longer period of duration are more likely to cause socioeconomic damage. Therefore, to understand how heat waves are sustained, it is imperative to identify and predict their mechanisms. In this study, we categorized the summer heat waves in South Korea into two categories based on their duration: short-duration events (5-7 days) and long-duration events (≥16 days). Following that, we examined the associated atmospheric circulation patterns pertaining to the persistence of summer heat waves (June through August from 1973 to 2022) using local and synoptic atmospheric variables obtained from the JRA-55 dataset. During both events, South Korea’s upper and lower atmospheres are dominated by high-pressure anomalies, with weakened jet streams, sinking motion, and suppressed convection. In short-duration events, there is a predominant meridional wave propagation with low-pressure anomalies in the Russian region of Siberia. Compared to short-duration events, long-duration events are related to strong and zonally extended high-pressure anomalies in the southern region of the Kamchatka Peninsula, which have suppressed the movement of anticyclones, thereby prolonging the duration of heat waves. Long-duration of heat waves in South Korea may be linked with persistent anomalies in mid-latitude induced by changes in stationary waves with global warming. As a result of this study, we will be able to improve our understanding of how summer heat waves persist, as well as be able to diagnose and predict heat waves in the future.
AS01-A056
Synergistic Roles of La Niña and Tibetan Plateau Warming in the Extreme Southeast China Drought in Winter 2020/21
Zhuoyu ZENG+, Ziqian WANG#, Song YANG
Sun Yat-sen University, China
In the winter of 2020/21, an extreme and long-lasting drought affected Southeast China (SEC), exerting significant social and economic impacts. In this study, the synergistic effects of La Niña and Tibetan Plateau (TP) warming on the drought are emphasized. Moisture budget analysis reveals that the drought was mainly attributed to the negative anomalies in horizontal and vertical moisture advections, namely the weakened atmospheric dynamic processes. The negative anomalies in horizontal moisture advection were previously claimed to be caused by La Niña events, as noticed by previous studies; however, the La Niña in 2020/21 presented as a cold tongue mode that induced more westward-extended Walker circulation and significant convection suppression over the western equatorial Pacific. Compared to the canonical La Niña events, warmer sea surface and stronger cyclonic anomaly occurred in the western North Pacific, inducing stronger northeasterlies and negative horizontal moisture advection anomalies over the SEC region. On the other hand, significant warming appeared over the TP in winter 2020/21, and it consequently enhanced the tropospheric meridional temperature gradient and further accelerated the westerly jet stream. The accelerated westerlies over the TP led to air accumulation and sinking motions in the downstream region, weakening the vertical moisture advection and being unfavorable for heavy precipitation in the SEC region. We highlight that, besides the La Niña event, the abnormal TP warming played a synergistic role in the extreme SEC drought in winter 2020/21. This multifactorial mechanism deepens our understanding of the drought formation and potentially improves the prediction of extremes in SEC.
AS01-A069
Impacts of Regional SST Warming on the Western North Pacific Under Global Warming
Chao-An CHEN1#+, Huang-Hsiung HSU2, Hsin-Chien LIANG2, Yu-Len CHEN2, Ping-Gin CHIU3, Chia-Ying TU2
1National Science and Technology Center for Disaster Reduction, Taiwan, 2Academia Sinica, Taiwan, 3University of Bergen, Norway
The Western North Pacific (WNP) area is the main precipitation region with energetic typhoon activity in the boreal summer. A decreased precipitation and anomalous anticyclonic circulation in the WNP region are shown in the high-resolution atmospheric model (HiRAM) global warming simulation (RCP8.5_Ens). This study conducts a series of sensitivity experiments with various patterns of regional sea surface temperature warming (SST’spa) to explore the causes of the projected changes in the WNP in HiRAM. A slightly decreased precipitation and enhanced anticyclonic circulation in the WNP can be reproduced in experiments with 2-degree uniform warming, the spatial pattern of SST warming, warming over the Tropics, and the warming from greenhouse gases emission. More identifiable changes are shown in cases with Tropical Atlantic warming, the Tropical Indian Ocean, and the Pacific meridional mode-like pattern. These experiments, to some extent, reproduce the WNP response in HiRAM RCP8.5_Ens, indicating that most SST’spa can lead to decreased precipitation and enhanced WNP subtropical high. That might be because SST’spa reduces the spatial contrast of SST climatological distribution. On the contrary, the SST warming in WNP shows the opposite response to RCP8.5_Ens, revealing more precipitation and anomalous cyclonic circulation in the WNP. Contrasted responses are also detected in typhoon activity changes. The warming over the tropical eastern Pacific also generates an anomalous cyclonic circulation. These findings indicate that the forcing from remote SST warming has a more decisive influence in the WNP region than in situ warming, implying a high probability of decreased precipitation and enhanced subtropical high in WNP in the warmer future.
AS01-A070
Tropical Stratospheric Forcings Weaken the Response of the East Asian Winter Temperature to ENSO
Ruhua ZHANG1+, Wen ZHOU1#, Wenshou TIAN2, Yue ZHANG1
1Fudan University, China, 2Lanzhou University, China
The El Niño–Southern Oscillation (ENSO) plays a critical role in predicting the winter surface temperature over East Asia. Numerous studies have attempted to improve the seasonal forecasting skill in view of the combined effects of ENSO and oceanic–tropospheric factors. However, high uncertainty and notable challenges still exist in using the ENSO to predict the surface temperature. Here, we showed that tropical stratospheric forcings (Quasi-Biennial Oscillation, QBO) could disrupt the response of the surface temperature to ENSO. The response of the East Asian surface temperature to El Niño/La Niña events evidently weakened in winter during the westerly/easterly phase of the QBO. This disruption has shown an increasing trend in recent decades, limiting the usefulness of ENSO alone as a seasonal predictor of the surface temperature. The modulation of the QBO on the East Asian surface temperature is achieved mainly by affecting subtropical zonal winds and North Pacific wave activity. Our analyses suggest that the QBO is a nonnegligible predictor in improving seasonal forecasts of the East Asian surface temperature.
AS01-A071
Influence of Scandinavian Teleconnection Pattern on Summer Precipitation Over the Eastern Side of the Tibetan Plateau
Quan-Liang CHEN#+
Chengdu University of Information Technology, China
This study analyzes the relationship between the Scandinavian (SCA) teleconnection pattern and summer precipitation over the eastern side of the Tibetan Plateau (ESTP) between 1960 and 2020 and further studies the underlying physical mechanism. Statistical analysis showed that there is a significant and high negative correlation coefficient (around −0.59) between ESTP summer precipitation and the SCA teleconnection pattern over the period 1960–2020. When the SCA teleconnection pattern is in its negative phase, there is a significant increase in precipitation over most of the ESTP, and vice versa. Moisture budget analysis showed that vertical moisture advection makes a larger contribution to precipitation changes related to the SCA teleconnection pattern than evaporation and horizontal moisture advection. Specifically, positive precipitation anomalies related to the SCA teleconnection pattern are dominated by the enhanced dynamic component of vertical moisture advection, which is induced mainly by the significant ascending motion over almost the whole of the ESTP region. In summer, under the effect of SCA teleconnection pattern, the abnormal westerly wind transports the mean warm air from TP to ESTP and forms an abnormal warm advection over the ESTP, resulting in a significant vertical upward motion and more summer precipitation over the ESTP. This study reveals the possible physical mechanism of the impacts of SCA teleconnection pattern on summer precipitation over the ESTP region and provides a scientific basis for ecological protection and disaster mitigation measures associated with major projects such as the Sichuan–Tibet railway and the Chengdu–Chongqing Economic Circle.
AS01-A074
Analysis of Rainfall Generation Process in East Asia by Summer Cold Wave
Kwang-Hee HAN1+, Ho-Young KU1, Hayeon NOH1, Jee-Hoon JEONG2, Baek Min KIM1#
1Pukyong National University, Korea, South, 2Chonnam National University, Korea, South
On August 8th, 2022, Seoul experienced unprecedented rainfall with a record-breaking total of 381.5 mm/day, the highest amount in 115 years. Heavy rain is a prevalent and dangerous weather phenomenon in Korea, leading to many investigations and studies on its mechanism of occurrence. However, In the Summer of 2022, the pressure system surrounding the Korean Peninsula exhibited an atypical summer pressure pattern. Therefore, this study analyzed the specifics of the pressure system in the Korean Peninsula and the Eurasian continent to uncover the factors and mechanisms behind the heavy rain in August 2022. At the surface level, high pressure increased significantly near the Ural Mountains and Lake Baikal in Siberia during the beginning of August. In terms of temperature, the analysis focused on the advection of cold air with a temperature anomaly of below -5°C from high latitudes to the northwest of the Korean Peninsula via Siberia along the flow of the high-pressure system in the lower atmosphere. And at 500 hPa, blocking was evident in the Ural. The blocking over the Eurasian continent hindered the zonal flow and amplified the meridional flow, resulting in the transport of cold air from high latitudes to East Asia through the strengthened meridional flow. The movement of cold air towards East Asia encountered the rim of the North Pacific high pressure and established a stationary front, leading to heavy rainfall. This study defined the development of a summertime cold continental high pressure affecting the mid-latitude region as a "Summer Cold Wave" (SCW) and the formation of the front caused by the SCW as a "Summer Cold Front" (SCF). Furthermore, by examining previous instances of SCW, it was discovered that the formation of Ural blocking in summer played a role in the emergence of SCW.
AS01-A078
Evaluation of Performance of Atmospheric Simulations Using Community Atmospheric General Circulation Model Over Summer Monsoon Regions
Venkatraman PRASANNA1#+, Preethi BHASKAR2, Jai-Ho OH3, Inwon KIM4
1Meteorological Service Singapore, Singapore, 2Indian Institute of Tropical Meteorology, India, 3Nano C&W, Korea, South, 4Pukyong National University, Korea, South
This study evaluates the performance of the high-resolution atmosphere general circulation model (AGCM), namely the Community Atmospheric Model (CAM) in its representation of seasonal mean, interannual variability and global teleconnections over the south Asian summer monsoon region (SAM), Western North Pacific (WNP), Equatorial Indian Ocean (EIO), Maritime Continent (MC), and West & East Pacific Ocean basin (W-PAC & E-PAC). Based on the AGCM experiment conducted for CAM model with observed SST (similar to AMIP type experiment), the model’s skill in simulating summer monsoon rainfall over different domains (SAM, WNP, EIO, MC, W-PAC & E-PAC) is low for the climate period (1981–2008). The decreased skill of the model over the south Asian monsoon region is evident, when the model is compared with the tropical mid-Pacific regions (W-PAC & E-PAC) and MC, which indicates that the impact of atmospheric dynamics is more important than SST forcing alone over the Asian monsoon regions (SAM, WNP & EIO). Our result shows that the AGCM simulation over south Asia exhibit large uncertainty in capturing the anomalies associated with the large global forcing like El Niño and La Niña. The analysis clearly brings out the presence of large systematic biases in the model simulation. The lack of air-sea interaction processes limits the skill of the model forced with SST alone over the Asian summer monsoon regions (SAM, WNP & EIO). The improved skill over the tropical mid-Pacific regions (W-PAC & E-PAC) and MC may be attributed to the strong SST forcing over the Pacific and the better representation of upward and downward limb of walker cells. While reduced skills over the Asian summer monsoon regions (SAM, WNP, EIO) may be attributed to the lack of Air-Sea Interaction and lack of dynamical feed backs from the local effects.
AS01-A088
Unprecedented Extreme Temperature Variability of Inter-/intra-monthly Timescales in East Asia During the 2022/23 Winter Season
Ho-Young KU+, Hayeon NOH, Baek Min KIM#
Pukyong National University, Korea, South
During the winter of 2022/23, East Asia experienced extreme temperature fluctuations on both inter- and intra-monthly timescales. November 2022 was warmer than normal, while December was colder than normal, with the second-highest difference in monthly temperature anomaly between the two months over the past 44 years. This regime shift in monthly time-scale can be explained by the alteration of month-long dominance of warmer air from south and cold air from north-west. The long-lasting La Niña condition over three years contributed to near record-high sea surface temperatures in the western Pacific region, affecting the warm East Asian climate until November. In December, the WACE pattern emerged over Eurasia due to the amplified warming especially in the Barents-Kara Sea causing the East Asian region to be cold climate. In January 2023, East Asia experienced abrupt regime shift from warm to cold climate within in just a few days. This event was unprecedentedly largest temperature fluctuations, dropping 12.34℃ in 12 days, observed on an intra-monthly timescale during the winter. In early to mid-January, warm and moist air intruded into East Asia from the south driven by expansion of the North Pacific High leading to above normal warm climate in East Asia. Later in mid-January, blocking occurred in the Ural region, and the meandering of the jet stream caused cold air to flow into East Asia from the north, resulting in a cold wave at the end of January. The extreme temperature fluctuations in East Asia this winter on both inter- and intra-monthly timescales are attributed to the tug-of-war between tropical and polar air masses manifested by such as WACE patterns due to arctic amplification and equatorial warm and moist air intrusion partly explained by the long-lasting La Niña condition which contributes to the intermittent expansion of North Pacific warm High.
AS01-A093
Risk Assessments of Indian Summer Monsoon Rainfall Extremes Using a Max-stable Process Based Modelling Framework
Athira K1#+, Sarmistha SINGH1, Ash ABEBE2
1Indian Institute of Technology Palakkad, India, 2Auburn University, United States
The frequent incidence of extreme precipitation in India during the Indian Summer Monsoon (ISM) season has resulted in various devastating consequences such as flash flooding, crop destruction, loss of life, and damage to infrastructure. To mitigate the potential effects of extreme rainfall, it is essential to understand its impacts across the country. In this study a Maxstable process-based model has been used to model the Spatio-temporal variability of ISM rainfall extremes and the risk associated with various return levels. In addition to the spatial factors, the impact of large-scale climatic drivers, such as the El Niño Southern Oscillation (ENSO), has also been incorporated to demonstrate its influence on the extreme precipitation field. Due to the complexity of terrain across the country, spatial clustering has been implemented. The computational efficiency was substantially improved by the implementation of parallel computing on clusters. Twenty models with different combination of spatial and temporal covariates for location, scale and shape parameters have been selected and the best fit model was identified based on Takeuchi Information Criterion (TIC) values. Results indicates that the regions have noticeable spatial variabilities extreme precipitation and around 75% of the land area in India is under the risk of heavy rainfall for more than 50-year return period. Compared to the spatial extreme models, inclusion of climatic oscillations information (ENSO) in a model framework greatly improves the suitability of the model. The results of this investigation hold significant scientific and practical implications for monitoring and managing the risks associated with extreme rainfall. They can aid in the development of appropriate mitigation strategies and inform planning efforts for potential adverse effects caused by such extreme weather events.
AS01-A100
Oxygen Isotope Variability of Rainwater, Dripwater, and Modern Calcite Respond to ENSO Based on 11 Years’ Monitoring in Yuhua Cave, Southeast China
Wanyin QIU1,2+, Xiuyang JIANG2#, Xianfeng WANG1
1Nanyang Technological University, Singapore, 2Fujian Normal University, China
The scientific explanation of speleothem δ18O in the East Asian summer monsoon (EASM) domain is a crucial issue restricting stalagmite-inferred paleoclimate research. Long-term cave monitoring is an effective solution to deal with this issue. Here, we investigate the transfer mechanism of oxygen isotopic signals from rainfall to dripwater and modern calcite, using 11-year-long cave monitoring data from Yuhua Cave, southeast China, located in the frontal zone affected by the EASM. The δ18O in the precipitation (δ18Op) shows a high response to EASM activities associated with the intertropical convergence zone (ITCZ) migrations and the activities of West Pacific Subtropical High (WPSH) affected by El Niño Southern Oscillation (ENSO) activities. Upstream convection and rainout process play a crucial role during the transmission of the ENSO signal to the δ18Op in southeastern China. Affected by the mixing effect of the epikarst reservoir, the amplitude of δ18O in dripwater (δ18Od) is much smaller than δ18Op, and there is no obvious seasonal variation. The δ18Od reflected ENSO-related δ18Op during monitoring periods, with greater amplitude. The modern calcite δ18O (δ18Oc) series show significant seasonal variations controlled by the fractionation coefficient varied with cave temperature. At the interannual scale, the δ18Oc series can inherit the δ18Od ENSO-related variations. Our results suggest that high‐resolution stalagmite δ18O reconstructions from Yuhua Cave could characterize past ENSO‐related variability in the EASM on the annual-decade scale.
AS01-A101
The Spatio-temporal Pattern of Asian Summer Monsoon During Termination II Recorded by the Chinese Stalagmite δ18O
Wei JIA1#+, Pingzhong ZHANG2, Xianfeng WANG1, Shaoneng HE1, Shufang YUAN1, Guangxin LIU3
1Nanyang Technological University, Singapore, 2Lanzhou University, China, 3Yunnan University, China
The difficulty in constraining the large-scale Asian summer monsoon (ASM) variability in the Chinese monsoon region (CMR) during Termination II lies in our poor knowledge of the western part of the CMR largely due to the sparsity of the paleoclimate records. To get a better picture of the ASM during Termination II, we examined a precisely dated stalagmite δ18O record between 133.1 and 127.0 kyr B.P. from Wanxiang Cave in western China. In combination with published δ18O data from this cave, we have identified the ‘Weak Monsoon Interval’ (WMI) in the Wanxiang δ18O record and confirmed that the severe cold event in the North Atlantic caused the weakened ASM over the CMR via reorganization of the large-scale ocean-atmospheric circulation. However, the post-WMI change in δ18O is gradual, in contrast with the abrupt shift shown in the other cave records. The rapid northward migration of the westerly jet relative to the Qinghai-Tibet Plateau is probably responsible for such discrepancy. This northward migration prevents the more 18O-depleted moisture from reaching the study site and also causes the earlier northward movement of the East Asian summer monsoon (EASM) rainband that carries positive precipitation δ18O to obscure the possible abrupt decrease in our δ18O record. After the last interglacial onset, no obvious Younger Dryas (YD)-like event was recorded in Wanxiang Cave, which suggests a minimal impact of the YD-like event on the ASM variabilities. The relatively large amplitude of δ18O variation observed in Wanxiang Cave between the late penultimate glacial and the last interglacial corresponds to a dominant control of the Indian summer monsoon (ISM), whereas smaller δ18O amplitudes were recorded in those cave sites mainly under the influence of both ISM and EASM. Therefore, the hydroclimate change over the CMR during Termination II has resulted from a combination of multiple processes.
AS01-A112
Western Himalayan Extreme Precipitation Events in High Asia Refined Analysis: Climatology and Variability
Rohtash SAINI#+, Raju ATTADA
Indian Institute of Science Education and Research Mohali, India
The hydro-meteorological climate of the Himalayas is the lifeline for the most densely populated region in South Asia. Annual floods in the Himalayan rivers often occur during the monsoon season, affecting millions of people in the Himalayas and downstream regions. The Himalayan region is extremely vulnerable to the ramifications of extreme precipitation events (EPEs), such as flash floods, landslides, and agricultural and infrastructural damages during the Indian summer monsoon (ISM). Complex terrain, high meteorological diversity and uncertainty in observations over this region make it challenging to comprehend the precipitation disparities and predict the EPEs across the Western Himalayas (WH). Therefore, a better representation of EPEs characteristics over the WH using high-resolution data is crucial for precisely understanding the precipitation variability and mechanisms of climate-triggered localised natural disasters. This study investigates EPEs using Asia's first highest resolution (10 km), a regional atmospheric reanalysis, High Asia Refined analysis version 2 (HAR v2), during ISM. HAR v2 precipitation dataset has been generated by dynamically downscaling global ERA5 reanalysis data using Weather Research and Forecasting model (WRF). Majorly, heavy rainfall over the region during the ISM occurs by convection followed by orographically locked system. The intricate interaction of regional topography with moist airflow and temperature gradient accentuates the EPEs. The present study will investigate the dynamic and thermodynamic processes associated with EPEs over the study region. Overall, this study aims to provide scientific insights to investigate the potential impacts of climate change on extreme events, which in turn could help mitigate disasters in the Himalayan region. Detailed results of precipitation variability over the Himalayas, and mechanisms altering the atmospheric conditions attributed to the EPEs will be discussed.
AS01-A114
The Importance of the Orbital Parameters for the Indian Summer Monsoon During the Mid-holocene, as Deciphered from Atmospheric Model Experiments
Charan Teja TEJAVATH1#+, Karumuri ASHOK2, Supriyo CHAKRABORTY3
1National Center for Earth Science Studies, India, 2University of Hyderabad, India, 3Indian Institute of Tropical Meteorology, India
Proxy and model-based studies suggest multi-scale temporal variability in the Indian summer monsoon (ISM). In this study, using the CESM1 atmospheric general circulation model, we carried out multiple ensemble AGCM simulations for the Mid-Holocene (MH; ≈ 6 kyr BP), Medieval Warm Period (MWP; ≈ 1 kyr BP), Little Ice Age (LIA; ≈ 0.35 kyr BP), and Historical (HS; ≈ CE 2000) periods. We used the PMIP3/CMIP5 boundary conditions for this purpose. Our simulations indicate that the ISM during the MH was stronger compared to HS and the rainfall higher, in agreement with several proxy studies. The experiments also suggest that the ISM rainfall (ISMR) was higher during MWP relative to the LIA in agreement with our earlier results from the PMIP3 models. A relatively northward migration of the ITCZ over the Indian region and strengthening of the neighboring subtropical high over the northwestern Pacific, both associated with stronger insolation associated with the obliquity and precision during the MH, seem to be important reason Indian summer monsoon during the MH.
AS01-A116
Future Indian Ocean Warming Patterns
Sahil SHARMA1,2#+, Kyung-Ja HA2, Ryohei YAMAGUCHI3, Keith RODGERS2, Axel TIMMERMANN2, Eui-Seok CHUNG4
1IBS Center for Climate Physics, Korea, South, 2Pusan National University, Korea, South, 3Japan Agency for Marine-Earth Science and Technology, Japan, 4Korea Polar Research Institute, Korea, South
Most future projections conducted with coupled general circulation models simulate a non-uniform Indian Ocean warming, with warming hotspots occurring in the Arabian Sea (AS) and the southeastern Indian Ocean (SEIO). Although the corresponding spatial temperature gradients are associated with large-scale atmospheric circulation anomalies and rainfall trends with far-reaching societal implications, little is known about the underlying physical drivers. Here, we analyze a suite of large ensemble simulations conducted with the Community Earth System Model 2 to elucidate the causes of non-uniform Indian Ocean warming. Strong negative climatological air-sea interactions in the Eastern Indian Ocean are responsible for a future weakening of the zonal equatorial sea surface temperature gradient, resulting in a slowdown of the Indian Ocean Walker circulation and the generation of southeasterly wind anomalies over the AS. These contribute to anomalous northward ocean heat transport, reduced evaporative cooling, a weakening in upper ocean vertical mixing and an enhanced AS future warming. In contrast, the projected warming in the SEIO is related to a reduction of low-cloud cover and an associated increase in shortwave radiation. Therefore, the regional character of air-sea interactions plays a key role in promoting future large-scale tropical atmospheric circulation anomalies with implications for society and ecosystems far outside the Indian Ocean realm.
AS01-A117
Can Volcanos be Linked to Extreme Monsoons in Asian Countries?
Alvin WONG1, Amitava ROY2, Wyss YIM3, Indrani ROY4#+
1Volcanoes Study Group, Hong Kong SAR, 2SmartFlow Pneumatics, United Kingdom, 3The University of Hong Kong, Hong Kong SAR, 4University College London, United Kingdom
In recent years, extreme weather events have increased and in this work, we explore whether volcanic eruptions- subaerial, submarine or mixed, may have a role in or trigger, any of these extreme events. Volcanic materials (sulphur dioxide, water vapour and aerosols) released by volcanic eruptions can be carried by the wind and transported to a long distance and can affect the regions far away from the eruption sites. Based on location, the strength of eruptions and seasonal timings, volcanos have the potential to influence and alter atmospheric and oceanic circulation too. Hence, the impact of each volcanic eruption is different. Apart from circulation fields, related mechanisms that can modulate rainfall are the reduction of solar radiation, acting as condensation nuclei and complex interaction involving clouds among others. Strong volcanic eruptions can even alter ozone distribution in the stratosphere and hence can influence stratosphere-troposphere coupling. This study using observation from satellite data and rainfall records from Hong Kong Observatory revealed that volcanic eruptions have contributed to several extreme rainfall records in Hong Kong since 1963. The 1963 Agung eruption and the 1991 Pinatubo eruption can be linked to the driest year and 11th driest year of Hong Kong respectively. On the other hand, the 1982 El Chichón eruption and the 2008 Chaitén eruption could be linked to much excess precipitation in Hong Kong, the second and sixth wettest years on record respectively. Analyses of the recent strong submarine volcanic eruption Hunga Tonga in 2021 (December) that reached its peak in 2022 January is also explored in connection to the recent extreme monsoon rainfall in some east Asian countries. Such analyses and in-depth understandings of the impact of volcanic eruptions on climate will not only provide a useful direction for volcanic risk assessment but also lead to improved regional climate prediction.
AS02-A005
The Intensification of Consecutive Three Tropical Cyclones Passing Over a Warm Ocean Eddy in the South China Sea
Xi LUO1+, Wei YANG2, Lei YANG3, Dongxiao WANG1#
1Sun Yat-sen University, China, 2Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province, China, 3Chinese Academy of Sciences, China
An extremely strong and long-lasting (more than 8 months) oceanic warm core eddy existed in the South China Sea (SCS) from February–October 2010. From July–August 2010, three tropical cyclones (TCs; TC Conson, Chanthu, and Mindulle) consecutively passed over this eddy and sustained at least 21 h. The intensity change of all three TCs reached 20 kt within 24 h when they encountered this eddy. In mid-late July, tropical cyclone heat potential (TCHP) is overall stronger in the eddy region than in its surrounding region, thus TCHP plays an important role in the intensification of TC Conson and Chanthu. It is also found that the intraseasonal oscillation (ISO) and the quasi-biweekly oscillation (QBWO) can be important in favor of the further enhancement of TCs. The TCHP is too low to favor the intensity increase of TC Mindulle in late August, 2010, but weak vertical wind shear, ISO and QBWO act as key roles in the intensification of TC Mindulle.
AS02-A021
Long-term Trend of Tropical Cyclone Rapid Intensification Over the Western North Pacific
Haeun JO#+
Ulsan National Institute of Science and Technology, Korea, South
Most strong typhoons undergo rapid intensification (RI), and it is difficult to predict them. In that sense, the analysis was conducted to understand better the trends and characteristics of the rapid intensification of tropical cyclones (RITCs) that can cause significant damage. Although it is difficult to explicitly define the rapid intensification of typhoons, generally defined as a period during which the intensification rate is greater than 15.4 m/s within 24 hours. This study used JTWC best-track data from 1982 to 2020 for the northwest Pacific. As a first result, the time series of RITCs ratio and LMI intensity shows a clear trend of increase in the autumn TC period than in the summer. In addition, the longitude of occurrence and strongest point of tropical cyclones also showed a tendency to move westward, which was evident in the autumn, especially in September. Secondly, an analysis was conducted to find the reason for the tendency of occurrence and the LMI location to be biased toward the west. When the correlations between RI genesis and LMI longitude and the various oscillation indices in the autumn period were calculated, the possibility that PDO was most likely to have an effect was found. In addition, values of sea surface temperature and tropical cyclone heat potential increased in the recent RI increase zone during the autumn TC period. This may have influenced the recent increase in the RI ratio, and further analysis of several synoptic variables will be conducted.
AS04-A002
Aerosol High Water Content and Moderate Acidity Favorite Sulfate and Secondary Organic Aerosol Formation in Combustion-derived Soot-containing Particles
Xiaojuan HUANG#+
Fudan University, China
Fine particles pollution associated with high sulfate and secondary organic aerosol (SOA) still often occur in winter, despite efficient pollutants mitigation has been achieved in China. The fast SO2 oxidation mechanisms revealed recently are controversial but consistently recognized associating with aerosol water. Here we report that both multiphase oxidation of SO2 by N(Ⅲ) involving aged soot-containing/iron-rich particles, and aqueous hydroxymethanesulfonate formation dominated high sulfate yield in wet particles with pH of 4.0~4.5 under relative humidity >85% in wintertime of northern China. We also provide a new evidence in terms of single particles for enhanced SOA generated from combustion-derived primary organic aerosol (POA) under high humidity. High humidity benefits the water uptake of particles, and aerosol high water content buffers aerosol acidity, favorites sulfate formation and the aging of soot-containing particles, particularly facilitates the conversion of combustion-derived POA to SOA. This study highlights a co-reduction on reactive gases and particles those directly emitted from solid fuels combustion for mitigating sulfate and SOA under high humidity.
AS04-A015
Secondary Organic Aerosol Formation from Wood Burning Emissions: Contribution and Chemical Evolution
Kun LI#+, Lin DU
Shandong University, China
Organic vapors from biomass burning are a large source of secondary organic aerosol (SOA). Previous smog chamber studies found that the main SOA contributors in biomass burning emissions are volatile organic compounds (VOCs). Intermediate volatility organic compounds (IVOCs), thought to be efficient SOA precursors, are a considerable fraction of biomass emissions, but their contribution to SOA formation has not been directly observed. Here, by deploying a newly-developed oxidation flow reactor to study SOA formation from wood burning, we find that IVOCs can contribute ~70% of the formed SOA, i.e., >2 times more than VOCs. This previously missing SOA fraction is interpreted to be due to the high wall losses of semi-volatile oxidation products of IVOCs in smog chambers. The finding in this study reveals that SOA production from biomass burning is more than 3 times higher compared to previous studies, and highlights the urgent need for more research on the IVOCs from biomass burning and potentially other emission sources. In addition, by applying source apportionment and clustering methods, we are able to track the chemical evolution of SOA molecules. The results provide insights into the multi-generation chemistry when biomass burning emissions are transported in the atmosphere.
AS04-A021
Evolution of Indoor Cooking Emissions Captured by SESI-HRMS
Xue LI1#+, Sasho GLIGOROVSKI2, Jiafa ZENG3, Majda MEKIC4
1Jinan University, China, 2Chinese Academy of Sciences, China, 3University Children's Hospital Basel, China, 4Leibniz Institute for Tropospheric Research, Slovenia
Cooking emissions represent a major source of air pollution in the indoor environment and exhibit adverse health effects caused by particulate matter together with volatile organic compounds (VOCs). A multitude of unknown compounds are released during cooking, some of which play important roles as precursors of more hazardous secondary organic aerosols in indoor air. Here, we applied secondary electrospray ionization high-resolution mass spectrometry for real-time measurements of VOCs and particles from cooking peanut oil in the presence of 300 ppbv nitrogen oxides (NOx) generated by a gas stove in an indoor environment. More than 600 compounds have been found during and after cooking, including N-heterocyclic compounds, Oheterocyclic compounds, aldehydes, fatty acids, and oxidation products. Approximately 200 compounds appeared after cooking and were hence secondarily formed products. The most abundant compound was 9-oxononanoic acid (C9H16O3), which is likely the product formed during the heterogeneous hydroxyl (OH) radical oxidation of oleic acid (C18H34O2) or linoleic acid (C18H32O2). Real-time detection of an important number of organic compounds in indoor air poses a challenge to indoor air quality and models, which do not account for this extremely large range of compounds.
AS04-A022
The Combustion Conversion Coefficient for Constructing Open Biomass Burning Emission Inventory Based on Satellite FRE
Jian WU#+
China University of Geosciences, China
It is necessary to convert fire radiant energy (FRE) to biomass burning consumption by the combustion conversion coefficient, when adopting the satellite FRE to estimate the open biomass burning emission. To date, the combustion conversion coefficients are considered to be scalar constants, which ignores the influence of multiple factors during the combustion process and regional differences. This project aims to conduct a systematic analysis of combustion conversion coefficients, by the view of ground experiment measurement, satellite data verification and emission inventory improvement. Firstly, the combustion conversion coefficients of typical biomass sources in China are obtained and the effects of fuels type, combustion state, combustion scale and combustion temperature on the combustion conversion coefficient are revealed, based on the ground experiment. Then, the satellite data are used to estimate the regional combustion conversion coefficient, so as to verify the reliability of the ground experimental measurement results on the regional scale. Finally, the verified combustion conversion coefficients are applied to improve the accuracy of the emission inventory. The uncertainty of the emission inventory caused by the combustion conversion coefficient has been estimated. The research results provide a new parametric scheme for correcting the uncertainty caused by the combustion conversion coefficient and improving the accuracy of the open biomass burning emission inventory in China.
AS04-A023
Contribution of Household Stoves to Atmospheric Ammonia and Nitrous Acid: Insights from Isotopes
Yang ZENG#+
Shandong University, China
Household stoves are widely used in developing regions for cooking and heating purposes, but they also represent a significant primary emission source of gaseous pollutants. To investigate their impact on air pollution, we collected samples of ammonia (NH3) and nitrous acid (HONO), two important reactive nitrogenous gases, from various sources including the flue gas of typical household stoves. We measured their stable nitrogen and oxygen isotopic signatures (δ15N and δ18O) to identify their sources. In a year-long case study, we found that during autumn and winter, the stable isotopic compositions of atmospheric NH3 and HONO closely matched those of stove flue gas. This suggests that household stoves play an important role in the local budgets of NH3 and HONO. These findings underscore the need for targeted interventions to address the use of household stoves in developing regions as part of broader efforts to reduce air pollution and its associated health impacts.
AS04-A025
Cases Study of 2009 Australian Black Saturday and 2003 Siberian Taiga Fires as Seen by MIPAS Instrument
Alexandra LAENG#+
Karlsruhe Institute of Technology, Germany
We investigate the effect of forest fires on aerosol and gaze composition of the stratosphere, using the interferometric measurements of MIPAS instrument, that monitored the atmosphere from to 2002 to 2012 from ENVISAT platform. Two events are analyzed: 2009 Australian Black Saturday fires and 2003 Siberian Taiga fires. The impact on the composition of CO, aerosols, H2O, ozone and temperature are analyzed and the 3-dimensional plume trajectory is reconstructed, using the data of MIPAS scientific Processor run at IMK-ASF/IAA.
AS06-A008
Towards the Next Generation Real-time Retrieval of Precipitable Water Vapor – Algorithm and Performance Evaluation
Peng SUN1#+, Kefei ZHANG1, Suqin WU1, Moufeng WAN1, Dantong ZHU2, Longjiang LI1, Minghao ZHANG1
1China University of Mining and Technology, China, 2North China University of Water Resources and Electric Power, China
As is well known, water vapor is an important greenhouse gas in the atmosphere that plays a critical role in atmospheric dynamics process. It is closely related to weather and climate phenomena that affects our daily life. Therefore, precisely determining, mapping and monitoring water vapor contents has been a vital research concentration in deepening our understanding of atmosphere and our earth’s environment. Precipitable water vapor (PWV), which measures the contents of the water vapor in the atmosphere, is an essential parameter in climate and meteorological research. Among the PWV sensing methods, Global Navigation Satellite Systems (GNSS) is characterized by its remarkable accuracy, super capacity to operate under diverse weather conditions, and high ability to deliver real-time products. This contribution focuses on the algorithm, software development, and accuracy evaluation of the real-time PWV retrievals based on GNSS precise point positioning (PPP) algorithm. First, some advanced models were developed to determine high-accuracy zenith hydrostatic delay (ZHD) and weighted mean temperature (Tm). Then, an enhanced multi-GNSS real-time PPP software was developed to calculate the zenith tropospheric delay (ZTD) over the GNSS station. Finally, an exhaustive analysis was undertaken to assess the accuracy of real-time PWVs derived from the PPP-based ZTDs. The high-accuracy real-time PWV obtained is promising for time-critical meteorological applications. Additionally, our 20-years efforts towards GNSS meteorology were also summarized in this contribution.
AS09-A003
Convective and Microphysical Characteristics of Extreme Precipitation Over the Pearl River Delta at Monsoon Coast
Yali LUO1#+, Shuting YU2, Chong WU3, Yanyu GAO4, Mingxin LI3, Dong ZHENG3, Weixin XU5
1Nanjing University of Information Science & Technology, China, 2 Ji'nan Meteorological Bureau, China, 3Chinese Academy of Meteorological Sciences, China, 4China Meteorological Administration, China, 5Sun Yat-sen University, China
Using multisource data including 5-yr dual-polarization radar observations, convective and microphysical characteristics of extreme precipitation features (EPFs) over a monsoon coastal region in South China are investigated including dependence on rainfall extremity and subseasonal variations. The EPFs are sorted into three groups according to the extreme rainfall intensity: 84 – 126 mm hr-1 (ER1), 126 – 186 mm hr-1 (ER2), ≥186 mm hr-1 (ER3). The more extreme rainfall shows a notable increase and decrease in the fractions of “intense” convection (7.6%, 20.6%, 31.6%) and “weak” convection (41.3%, 22.9%, 18.9%), respectively, while that of the “moderate” convection remain about 50%. The higher rainfall extremity is accompanied by statistically significant increases in ice and liquid water contents and a slight decrease in the fraction of coalescence in liquid-phase processes. While the raindrop size distributions (RSDs) of ER1 to ER3 similarly feature a mean size larger than “maritime-like” droplets and a concentration much higher than “continental-like” raindrops, the mean size and concentration of raindrops tend to increase with the increasing rainfall extremity. During the pre-monsoon period, precipitation systems are the largest in area but their EPFs are the least frequent and have the lowest raindrop concentration, likely due to the colder, drier environment with large vertical wind shear (VWS). Onset of the summer monsoon increases the frequency and convective intensity of EPFs, leading to an increase in raindrop size, consistent with the substantial increases of CAPE and moisture during the active-monsoon period. EPFs share similar convective intensity and RSD between the post-monsoon and active-monsoon periods, although the post-monsoon EPFs are slightly less frequent and have a smaller horizontal scale related to the reduced 0–6-km VWS. EPFs associated with tropical cyclones have the weakest convective intensity but the most active warm-rain processes with the RSD being closer to the maritime regime.
AS09-A004
Synergistic Effect of El Niño and Negative Phase of North Atlantic Oscillation on Winter Precipitation in the Southeastern United States
Xinxin TANG1+, Jianping LI1#, Yazhou ZHANG1, Yanjie LI2, Sen ZHAO3
1Ocean University of China, China, 2Chinese Academy of Sciences, China, 3University of Hawaii at Manoa, United States
This study reveals that the significant increase of winter precipitation over the southeastern United States (SEUS) is associated with El Niño and negative phase of North Atlantic Oscillation (NAO-). Diagnosis of large-scale dynamics shows that El Niño and NAO- have a synergistic effect on the enhancement of transient eddies and stationary waves in the eastern Pacific, southern United States, and North Atlantic. These enhanced transient eddies are associated with subtropical jet stream acceleration and maintenance of subtropical low from the eastern Pacific to the Atlantic, influencing stronger stationary waves propagation from tropical Pacific to the SEUS and North Atlantic, and from the northwestern Atlantic to the SEUS and Pacific. This favors a positive phase of meridional dipole in geopotential height anomalies between the tropics and subtropics in the Western Hemisphere (WTSD) during the co-occurrence of El Niño and NAO-. The strong positive WTSD-like pattern, accompanied by a zonally extended and southerly shifted subtropical westerly jet, induces a northward tilted secondary circulation with ascending motion over the SEUS and Gulf of Mexico. Simultaneously, intensified trough over the SEUS promotes moisture and warm advection from the subtropical and tropical Pacific converging with cold advection from the northwestern North Atlantic in the adjacent Gulf of Mexico, which is beneficial for front and cyclone generation, and induces heavy precipitation in the SEUS. This study suggests that the synergistic effects of El Niño and NAO- help to understand the variability of winter SEUS precipitation.
AS09-A006
Differences in Hourly Heavy Rainfall Over the Southeastern Extension of the Tibetan Plateau Under the Topographic Impacts
Weihua YUAN#+
Institute of Atmospheric Physics, Chinese Academy of Sciences, China
The southeastern extension of the Tibetan Plateau (SETP) is distributed by the typical longitudinal mountains and has unique climate characteristics and significant regional differences. The diurnal cycles of rainfall amount, frequency, and intensity over the SETP in the warm seasons (May to September) were investigated using high-density hourly station rainfall data and the possible mechanisms were discussed by analyzing the ERA5 reanalysis and satellite data. The largest amounts of rainfall appeared on the southern and western margins of the SETP. Located at the southern margins of the SETP, the adjacent western (Reg_W) and eastern (Reg_E) regions presented a similar rainfall amount, frequency, and intensity, but the diurnal features of the two regions were quite different. The rainfall amount, frequency, and intensity had dominant peaks in the late afternoon in Reg_W, while in the early morning in Reg_E. A secondary peak in the early morning can be found in Reg_W. The diurnal features of the two regions were closely related with the low-level atmospheric conditions and the distribution of clouds. The enhanced convergence of the anomalous southerly winds and sufficient water vapor after midnight contributed to the nocturnal rainfall at the southern edge of the SETP. In the afternoon, the lower surface air temperature and more stable stratification in Reg_E, as compared with Reg_W, were relatively unfavorable for the occurrence of afternoon convection.
AS09-A009
Impact of the Prognostic Snow and Graupel Number Concentrations on the Simulated Precipitation
Juhee KWON+, Sun Young PARK, Kyo-Sun LIM#
Kyungpook National University, Korea, South
The Weather Research and Forecasting (WRF) Double-Moment 6-class (WDM6) microphysics scheme only predicts the number concentrations for liquid-phase hydrometeors. Even though Park and Lim (2023) recently revised the WDM6 scheme by implementing the prognostic number concentration of cloud ice, the precipitating solid-phase hydrometeors such as snow and graupel are still treated as the single-moment approach, in which only mixing ratio is prognosed. In this study, the new version of WDM6 microphysics scheme is introduced by adding the prognostic number concentrations of snow and graupel to the WDM6 (Park and Lim, 2023). Therefore, the new WDM6 scheme predicts the number concentrations of all hydrometeors. By introducing the double-moment approach for snow and graupel, several microphysical processes related to them are modified and added. The newly added processes include the processes of accretion of rain by snow, self-collection of snow, sublimation of snow and graupel, and evaporation of snow and graupel. The new scheme has been tested for four summer-precipitating (Kim et al., 2019) and seven winter-precipitating convection cases (Ko et al., 2022). The mixing ratio of snow tends to increase and that of graupel decreases in the new scheme. Both mixing ratio and number concentration of rain reduces. The new scheme improves the equitable threat score (ETS) and false alarm ratio (FAR) for eight cases and probability of detection (POD) for seven cases among 11 total cases. *This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government. (MSIT) (RS-2023-00208394)
AS09-A010
The New Version of Weather Research and Forecasting (WRF) Double-moment 6-class (WDM6) with the Revised Ice Microphysics
Sun Young PARK+, Kyo-Sun LIM#
Kyungpook National University, Korea, South
The Weather Research and Forecasting (WRF)-Double-Moment 6-class (WDM6) microphysics scheme treats the solid-phase hydrometeors as the single-moment approach. The scheme only predicts the mixing ratio of graupel, snow and cloud ice. In addition, each category of solid-phase hydrometeors is characterized by static parameters defining pre-defining density, diameter-mass relationship, and diameter-fall speed relationship. Previous studies have reported a considerable sensitivity of simulated precipitation systems according to these static parameters. This study revises the ice microphysics in the WDM6 scheme through the implementation of prognostic graupel density and cloud ice number concentration. The new version of WDM6 has been tested in the idealized squall line and winter-time snowfall cases. the simulations with the new WDM6 show better statistical skill scores such as Root Mean Square Error (RMSE) and Equitable Treat Score (ETS), relative to the ones with the original WDM6. It is also confirmed that the new WDM6 simulates a similar fall velocity-density relationship of graupel to the observation. More detailed analysis will be presented in the conference.* This work has been supported by the South Korean Ministry of Science and ICT (MSIT) and the National Research Foundation of Korea (NRF) (grant no.2021R1A4A1032646).
AS09-A013
A Convection‐permitting Numerical Study of Diurnal Cycles of Pre‐summer Rainfall Over Southern China
Xi LU#+
Sun Yat-sen University, China
In this study, the convection-permitting model (CPM) with 3-km horizontal resolution has been used to investigate the simulated ability on diurnal cycles of pre-summer rainfall over southern China with various subregions and rainfall systems. Compared with the observations, the model captures the peak time of nocturnal rainfall in the western inland related to the eastward-propagating rainfall system over the eastern slope of the Yungui Plateau. The simulated eastward-propagating rainfall system moves a short distance and has a short lifetime due to the weaker westerly-steering flow and southerly winds in the late night bringing less warm and moist air with the weaker upward flow of the mountain–plain solenoid circulation that is unfavorable for convection instability. Over the eastern inland, the model shows good performance on simulating the quasi-stationary rainfall system in the morning because of the high resolution of topography. However, the model cannot simulate the climatology of the secondary morning rainfall peak due to overestimation of the rainfall from noon to evening. On the other hand, the weaker simulated southwesterly winds especially on the north side of the Nanling Mountains with decreased upward movement and moisture convergence and the more stable atmospheric condition lead to the disadvantage of convective rainfall. The CPM reproduces the afternoon rainfall peak but with a lead of 2–3 hr and still cannot simulate the morning peak well over the coastal region. The main source of mode bias is the over estimation of the onshore winds in the boundary layer over the land with the reduced temperature difference between land and sea resulting in insufficient convergence in the coastal region.
AS09-A014
Characteristics and Origins of the Intraseasonal Precipitation in the Wintertime North Pacific
Jing HUANG1+, Yang ZHANG2#, Xin WANG3, Xiu-Qun YANG2, Xuejuan REN2
1South China Sea Institute of Oceanology, Chinese Academy of Sciences, China, 2Nanjing University, China, 3Chinese Academy of Sciences, China
High-resolution observations show that the intraseasonal precipitation variance accounts for 20-50% and 40-70% of the total daily precipitation variance in the wintertime western and eastern North Pacific, respectively, implying the indispensable ingredient of the intraseasonal precipitation for the hydrological cycle over the East Asia-North Pacific-North American region. In this study, using daily observational data, characteristics and origins of the intraseasonal precipitation in the wintertime western and eastern North Pacific are investigated. The changes of the intraseasonal precipitation in the western and eastern North Pacific are featured by the anomalous precipitation in the Kuroshio-Oyashio Extension (KOE) and eastern North Pacific along 30°N, respectively. The intraseasonal precipitation in the western North Pacific is associated with the migratory weather systems with anomalous anticyclone originating from Japan and the cyclone originating from Northwest Asia, accompanied with the upward draft in the KOE region. The instability conditions are different in the north and south of the KOE. The unstable static and baroclinic conditions are both responsible for the enhanced precipitation in the south of the KOE. The anomalous precipitation is mainly determined by the atmospheric baroclinic instability in the north of the KOE. The anomalous atmospheric circulations associated with the intraseasonal precipitation in the eastern North Pacific are characterized by a dipolar structure, in which the anomalous quasi-stationary cyclone in the eastern North Pacific plays a major role. The upward draft associated with the anomalous cyclone and atmospheric static instability induced by the anomalous southeasterly wind provide dynamic and instability conditions for the anomalous precipitation. Furthermore, the moisture sources of the intraseasonal precipitation in western and eastern North Pacific are both dominated by the anomalous water vapor transport by the atmospheric circulation and the change of the precipitable water.
AS09-A016
A Comparison of Precipitation Forecasts with Different Scale-aware Cumulus Parameterizations Over South Korea
Ji-Young HAN#+
Korea Institute of Atmospheric Prediction Systems, Korea, South
Scale-aware cumulus parameterizations and their precipitation forecast skill over South Korea are compared at different horizontal resolutions. A series of single-domain experiments are conducted at 3-, 9-, and 27-km spatial resolution with three different scale-aware cumulus parameterization schemes available in the Weather Research and Forecasting (WRF) Model, that is, the multiscale Kain-Fritsch scheme, the Grell-Freitas scheme, and a revised version of the simplified Arakawa-Schubert scheme developed by the KIAPS (KSAS). The results from the experiments are compared with each other and with those obtained with the cumulus parameterization scheme switched off and using conventional cumulus parameterization schemes with no scale-aware capability, particularly focusing on the contribution of parameterized convection, which is determined by the convective updraft fraction or scale-dependent parameter as a function of horizontal resolution in the scale-aware cumulus parameterization, and the short-range precipitation forecast skill over South Korea against automatic weather station rain gauge observations. Based on the results, the method of defining convective updraft fraction in the KSAS is revised to use a more physically-based method and its effect on the precipitation forecast skill at each spatial resolution is examined.
AS09-A017
Impact of Vertical Movement of Soil Liquid Water on an Extreme Precipitation Event in South China
Youyong XIE+, Huiling YUAN#
Nanjing University, China
Soil liquid water (SLW) has an important impact on near-surface soil hydro-thermodynamics and surface energy budget. A new term about vertical movement of SLW (VMSLW) was added to the soil heat conservation equation in Noah-MP coupled with WRF, and the effects of the local and upstream VMSLW on a heavy summer rainfall event during June 15-25, 2010 in South China were investigated. Results show that when precipitation intensity is ≥ 2 mm/day, the magnitude of the VMSLW term in the soil heat conservation equation is comparable to that of the original term due to soil thermal conduction. Local VMSLW (contribution rate: 5.88%) leads to high pressure anomalies in South China, which weakens precipitation and reduces the positive bias of precipitation. The upstream VMSLW (contribution rate: 9.24%) decreases water vapor transport in Indo-China Peninsula, causing reduced precipitation in South China. The modified soil heat conservation equation with the new VMSLW term improves the precipitation simulation in the coupled WRF-Noah-MP model and deepens the understanding of interactions between SLW and precipitation.
AS11-A004
Thermal Effects on Dispersion of Secondary Inorganic Aerosols in an Urban Street Canyon
Minjoong KIM1#+, Seungyeon LEE1, Seon-Young PARK1, Jae-Jin KIM2
1Myongji University, Korea, South, 2Pukyong National University, Korea, South
The surface heating in complex urban areas affects concentration of secondary inorganic aerosol (SIA) via flow and chemical environment changes. Previous studies on heating effects on pollutants have focused on effect of dispersion change. However, the heating of buildings also affects SIA concentration via chemical environmental changes, such as reaction rate and thermodynamic equilibrium changes. Accordingly, we investigated the effect of heating, by not only flow changes but also chemical environment changes, on SIA using a coupled chemistry-computational fluid dynamics (CFD) model. We investigated the change of temperature and wind in each scenario to separately identify the effects caused by the chemistry and dynamics of thermal heating on reactive aerosols. We found that both the chemical and dynamical effects reduce SIA concentration. The effect of heating caused by chemical environment changes on SIA was 49.4% larger than that of flow changes, suggesting the importance of chemical reactions in aerosol calculations in urban microscale aerosol simulations, which are not considered in most CFD-based models. We conclude that chemical speciation and detailed aerosol chemistry calculations, including an inorganic aerosol thermodynamic equilibrium model, should be considered for accurately accounting for the effect of heating on urban areas. This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2021-03312.
AS11-A008
Comparison of Emission Characteristics and Treatment Technologies of VOCs in Typical Pharmaceutical Enterprises
Wang XIUYAN#+
Nankai University, China
In order to obtain VOCs emission characteristics of different products in corresponding processes of pharmaceutical industry, and evaluate the impact of different treatment technologies on VOCs emission, this study took 11 typical pharmaceutical enterprises in Zibo City, Shandong Province as the research object, collected and analyzed VOCs samples of different processes and treatment technologies. The VOCs source spectra of different emission stages were compared using the coefficient of divergences (CD) method. The total non-methane hydrocarbon (NMHC) was used to characterize the overall emission of VOCs. The emission factors of pharmaceutical industry were calculated using the measurement method. The effects of different waste gas treatment technologies on VOCs emissions were evaluated according to the purification efficiency. The results show that the average VOCs emission factor of typical enterprises A and B in Zibo pharmaceutical industry is 7.97 ± 8.21 g/kg-product, which was 1/54 of the recommended value (430 g∙kg-1) provided by literature (Ministry of Ecology and Environment of the People's Republic of China, 2014). There are significant differences in VOCs emission characteristics among different processes. After RTO treatment, the proportion of aromatic hydrocarbon species increased from 49% to 58%, while the proportion of other species decreased. However, after water spraying +UV photo-oxygenation treatment, the proportion of alkane species decreased from 75% to 69%, and the proportion of other species increased. The VOCs discharged by chemical synthesis enterprises are mainly alkanes, and the proportion of each species has almost no change after the treatment of condensation, spraying and activated carbon adsorption (CSA). Different treatment technologies have different purification efficiency for different kinds of PAMs. UV photo-oxygenation + water spray is more suitable for the removal of VOCs and odor in sewage stations, and RTO is more suitable for the removal of VOCs with higher concentration.
AS11-A010
Aqueous Aging of Secondary Organic Aerosol Coating Onto Black Carbon at an Urban Site in Southern China
Liming CAO#+, Xiaohe LI
Peking University Shenzhen Graduate School, China
Secondary organic aerosol (SOA) in the atmosphere can be formed from the gas phase precursors and evolve in the particle phase. Compared to numerous studies on gas phase oxidation of volatile organic compounds (VOCs), the evolution of OA and corresponding mechanisms in the particle phase are still unclear. In this study, a thermodenuder (TD) was coupled with both a long time-of-flight aerosol mass spectrometer (L-ToF-AMS) and a soot particle aerosol mass spectrometer (SP-AMS) at an urban site in southern China during wintertime of 2018, to explore whether there is significant difference for OA evolution on black carbon (BC) aerosols. The average mass concentration of PM1 during the sampling period was 19.5±9.5 μg m-3, with OA as the most abundant chemical components. The OA measured by L-ToF-AMS and SP-AMS both were resolved into different primary and secondary factors, with the OA factors on BC particles showed different volatilities to that on the bulk aerosol. The BC-containing organics was more aged with a higher fraction of SOA contribution (83.3%) and higher O/C (0.63) compared with bulk OA. During the aging process of OA on BC particles, the fraction of BC-containing OA in total mass increased with the decreasing of volatility and correlation with BC. The more-oxidized oxygenated OA (MO-OOA, an agent of aged SOA) exhibited a unique preference on BC particles compared to other OA components. The abundant transition metals detected on BC particles was possibly the catalyser for the transformation from less oxidized OOA (LO-OOA, an agent of fresh SOA) to MO-OOA in aerosol aqueous-phase on BC particles and thus facilitates SOA formation. More studies are needed to further explore the potential role of BC and transition metals as catalysers for OA aging and the co-benefit of BC and transition metals pollution control on SOA reduction in the atmosphere.
AS11-A014
Fine Mode Atmospheric Arsenic Concentrations Over a Semi-urban Atmosphere in Eastern Indo Gangetic Plain: Very High Exceedance Over Indian Standard
Sauryadeep MUKHERJEE1#+, Adnan QADRI2, Tarun GUPTA2, Abhijit CHATTERJEE1
1Bose Institute, India, 2Indian Institute of Technology Kanpur, India
Arsenic (As) exposure is a worldwide public health issue. Inhalation of atmospheric particulate matter enriched with As is an important exposure route. Little research has been conducted for atmospheric As, especially in Indian context. This study has been conducted over Shyamnagar (22°50’N, 88°23’E, 8masl) a semi-urban station situated in the eastern part of IGP near Kolkata metropolis for an entire year (2019). 24hr samples of fine mode aerosols (PM2.5) were collected using a 5-channel aerosol sampler on every alternate day covering all the seasons. The Energy Dispersive X-ray Fluorescence technique was used to determine As concentrations along with other trace elements in PM2.5. The major elements observed were Chlorine, Sulphur, Potassium, Silicon, Aluminum, Zinc, Iron, Sodium, Calcium, Barium, and Lead along with Arsenic. The annual mean concentration of As was found to be 381.8 ngm-3 which is more than 60 times the Indian Standard (NAAQS; 6 ngm-3). The concentrations were highest during winter (~800 ngm-3) followed by postmonsoon (~ 630 ngm-3), premonsoon (~ 160 ngm-3), and monsoon (~ 80 ngm-3). This implies the constant emission of atmospheric As throughout the year. As showed very strong correlations with Lead (Pb) throughout the year (R2 = 0.99) suggesting some continuous stationary emission sources, e.g. battery industry. Low-grade coal containing arsenates (AsO43-) can also be a source of Arsenic as they are used in local eateries and domestic cooking purposes as easily affordable fuel. Irrespective of the source, this kind of high concentration of As in the atmosphere can be of huge adverse impact from the perspective of human health for the local residents. This study draws the serious attention of the scientific community as well as policymakers for regular surveillance and action plans for such overlooked semi-urban stations.
AS11-A016
Increases of Atmospheric Oxidation Capacity and Shifts of Formation Regimes Led to Ozone Increase in China from 2016 to 2019
Shengqiang ZHU1#+, Jinlong MA1, Peng WANG2, Hongliang ZHANG1
1Fudan University, China, 2The Hong Kong Polytechnic University, China
China is infronting severe ozone (O3) pollution although particulate matter reduced significantly, causing damages to public health and ecological systems. Here we utilized the comprehensive methods of ground-level observations, satellite data, and source-oriented chemical transport model to interpret O3 variations throughout China from 2016 to 2019. A remarkably worsened trend of O3 levels has been found both by observation and simulation in these years. Our results showed that the remarkable O3 elevation was found in the NCP and YRD (maximum daily 8h average O3 ~60 ppb) with an annual increasing rate of 10%. In addition, O3 formation regimes also changes obviously in the NCP, which shifted from VOC-limited to transition regimes (4.9%) and transition to NOx-limited regimes (9.6%). The elevation of MDA8 O3 was mainly attributed to the enhanced atmospheric oxidation capacity (AOC) in above regions. Particularly, the increasing ratios of OH and HO2 radicals (major oxidants) in NCP and YRD reached to ~15% and ~5%, respectively. The comprehensive study of long-term O3 changes, formation regimes, and AOC based on a multimethod approach should be considered when designing O3 control policies.
AS11-A017
Simulation of Global Aerosol Particle Number Concentration Considering the Volatility Distribution of Organic Aerosols
Xueshun CHEN#+
Chinese Academy of Sciences, China
The contribution of organic aerosol (OA) to particle formation, mass, and number concentration is one of the major uncertainties in current climate and air quality models. In this study, a global aerosol model considering the volatility distribution of organic components was developed to simulate detailed microphysical processes of organic species and other components. The model calculates the kinetic condensation of low-volatility organic compounds and equilibrium partitioning of semi-volatile organic compounds. Using this model, the response of particle number concentration to emission change was investigated. The model results strongly suggest the important role of OA volatility distribution in particle formation and the impacts of emission change on particle number concentration over the whole globe, especially over the areas influenced by anthropogenic sources.
AS11-A018
A Numerical Study on the Impact of Air Filter Equipped in the Vehicle on the Air Quality by Using WRF-CHEM with CAPSS Dataset
Chang KIM+, Yun Haeng JOE#, Hyun-Goo KIM
Korea Institute of Energy Research, Korea, South
The relationship between air quality and the pollutants generated by vehicles is of great concern in many cities around the world. In this research, we aim to understand the interaction between these two factors and the role of air filters in mitigating air pollution. To do so, we have used a combination of the Weather Research and Forecast model with a chemistry version 3.7.1 to study the impact of anthropogenic emissions from vehicles on air quality. In our study, we have used the CAPSS, Clean Air Policy Support System dataset as the source of anthropogenic emissions. The WRF-Chem model is used to the dispersion of these pollutants in the atmosphere and then predict the impact of these emissions on air quality. The simulation was executed from April 28 00 UTC, 2020 to May 30 00 UTC, 2020. Analysis data was made by the results 7 days after simulation began. This study prescribes that the mitigation of air pollutant emissions is valid only for the road emissions. i.e., line sources. Our results show that the use of air filters in vehicles can significantly reduce the concentration of air pollutants in the atmosphere by 5%. In conclusion, our study highlights the importance of considering the interaction between air quality and air pollutants generated by vehicles when developing air quality management strategies. The results of our research demonstrate the potential benefits of using air filters in vehicles to mitigate air pollution, and provide a basis for further investigation into the impact of air pollution on public health and the environment.
AS11-A022
Quantifying the Inter-city Transport of PM2.5 Using the Michaelis-Menten Equation in the Yangtze River Delta, China
Kangjia GONG#+, Jianlin HU
Nanjing University of Information Science & Technology, China
China began implementing the Air Pollution Prevention and Control Action Plan (APPCAP) in 2013 to improve air quality. Although the concentration of particulate matter in most areas has decreased significantly, some regions have yet to reach the second-level standard of China Environmental Air Quality Standards (CAAQS), such as Beijing-Tianjin-Hebei (BTH) and Yangtze River Delta (YRD). In this study, we used a source-oriented chemical transport model to quantitatively estimate the effects of inter-city transport on fine particulate matter (PM2.5) among the 41 cities in the YRD. And use the Michaelis-Menten equation to quantify the relationship between the cumulative contribution rate and the distance between cities in the YRD region. The results show that it is more appropriate to use the Michaelis-Menten equation to indicate the relationship between the cumulative contribution rate and distance, 71% of R2 values are greater than 0.9 in six regions and four seasons. The maximum contribution of regional transport (K1) and the distance where the regional transport contribution is half of the maximum contribution (K2) are different in different regions. The average value of K1 is 73.6, which is smaller in the northern part of the YRD and higher in central Jiangsu. K2 is larger in northern Jiangsu and central and southern Zhejiang. Primary PM2.5 and secondary organic aerosols (SOA) contribute more within the YRD, with 82.9% and 88.6%. The local contribution in autumn and winter in the northern part of the YRD is lower than that in spring and summer, especially in northern Jiangsu, where it is 90.4% in summer and 53.0% in autumn and winter. K2 is larger on polluted days, which means that it will be affected by a larger range on polluted days. The results can provide a scientific basis for regional joint prevention and control in the YRD region.
AS11-A027
On the Impact of Vertical Diffusion on Mesoscale Chemistry Transport Modeling
Lei JIANG#+
Nanjing University of Information Science & Technology, China
In this study, firstly, three first-order local closure vertical diffusion schemes used in multiple mesoscale chemical transport models (CTM) were embedded in the CHIMERE CTM model and tested over a one-year simulation covering the whole of France. Three model configurations present a fair reproduction of pollutant concentrations both in urban and rural areas, indicating it is an effective way to reproduce the dispersion of pollutants in chemistry transport modeling. However, it cannot be expected to significantly improve the vertical mixing under the first-order closure scheme. Secondly, a 1.5-order turbulence kinetic energy-based eddy diffusivity closure scheme called the new eddy diffusion (NED) is implemented in CHIMERE to describe more realistic diffusion processes near the surface. A fifteen-day simulation encompassing a winter pollution episode was performed for three major cities with a horizontal resolution of 1.67 km and the first layer height at 12 m, respectively. The NED scheme improved NO2 simulations at most urban sites compared to the initial Kz diffusion scheme (IKD). Taking the root mean square error as evaluation criteria, the average improvements are 18.8%, 24.5% and 9.5% for NO2 simulation in Paris, Lyon and Bordeaux respectively. For the model performance of PM2.5 and PM10 simulations in the urban areas of Paris, the improvements are 13.5% and 19.1%, respectively. Overall, preliminary outcomes of this study are encouraging. The simulation with more sophisticated and realistic eddy viscosities are better than for IKD that is widely used in CTMs, but we need to realize that this is only a fifteen-day simulation for three cities, for further research, longer periods are needed with a greater variety of meteorological situations to prove the universality of the NED scheme.
AS11-A032
Effects of Chemical Mechanism and Meteorological Factors on the Concentration of Atmospheric Pollutants in the Megacity Beijing, China
Li YUJIE#+
Beijing Normal University, China
In order to distinguishe effects of chemical mechanism and meteorological factors in the megacity Beijing, the sensitively experiments with the third-Generation Air Quality Modelling System is designed. The modelling system consists of the meteorological model (WRF), the emissions process model (SMOKE) and the air quality model CMAQ, and the experiments focus on the megacity Beijing for one year simulation in 2018. The baseline group experiment, named CB05_AER05 experiment, choses the gas-phase chemistry module CB05 and the aerosol mechanism AERO5, while the NOOP group experiment deactivates gas-phase chemistry module and the aerosol mechanism, and standing for the only meteorological factor without the chemical mechanism in the simulation. The results indicates that: 1) the modelling system plays well performance in the megacity Beijing in 2018. The correlation coefficient(R) of the simulated PM2.5 concentration and the observation value reaches to 0.7, which the normal mean bias (NMB) is -14%~32% in the 12 National Standard Air Quality (NSAQ) observation stations in Beijing. 2) The chemical mechanism has an effect on the concentration of PM2.5 up to 135% compared to the NOOP group results, while the PM2.5 concentration in NOOP group is 43.3 ug/m3, which stands for the influencing of the meteorological factor. The influencing factors of the pollutant concentration are complex, which also proves that the atmosphere is a complex system. 3) For the photochemical species, the peak frequency of NO2 concentration in the baseline group (CB05_AER05) and the NOOP group experiments are 26.9 ppbV and 2.2 ppbV, respectively. The numerical model is a good tool to quantify the effects of chemical mechanism and meteorological factors.
AS11-A038
Evaluation of Widely Utilized Emission Inventories in India Using the WRF-Chem Model and MODIS AOD Data
Diljit NAYAK#+, Gazala Habib HABIB, Sri KOTA
Indian Institute of Technology Delhi, India
To ameliorate the substandard air quality, a comprehensive national emission database is crucial for determining the aggregate emission reductions that are necessary to conform to air quality standards. Thus, it is imperative to assess the uncertainties associated with these emission inventories. This study endeavors to evaluate the accuracy of emission inventories in replicating the satellite-observed AOD for the Indian region, and to identify the most suitable emission inventory among the available options for the common baseline year of 2015. The study contrasts four databases (three global and one regional) that furnish emission estimates for air pollutants in India, which include EDGARv5, REASv3.2, and SMoGv1. Simulations were conducted for different seasons using WRF-Chem V3.8.1. The key finding of the study is that EDGAR emerged as the best performing emission inventory among all the databases across all seasons, with an average Root Mean Square Error (RMSE) of 0.38 for the entire year.
AS11-A041
Atmospheric Chlorine Chemistry in Urban Environment
Yee Jun THAM1#+, Shichun ZOU1, Lei YAO2
1Sun Yat-sen University, China, 2Fudan University, China
Chlorine chemistry play essential roles in tropospheric physicochemical processes, such as affecting the ozone (O3) level and secondary aerosol formation. Tropospheric chlorine chemistry was initially known to be important in the marine and polar atmosphere; however, more and more recent studies have indicated that chlorine chemistry was also active in inland areas. Various of gaseous chlorine species, such as nitryl chloride (ClNO2), molecular chlorine (Cl2), hydrochloric acid (HCl) and others, have been observed to be ubiquitous in the urban atmosphere, and were linked to the influence from anthropogenic sources like coal combustion and biomass burning activities. Upon photolysis, these chlorine species can release chlorine atom, which can react with O3 rapidly. The chlorine atom can also oxidize volatile organic compounds (VOC) with a reaction rate up to two order of magnitude faster than the reaction of hydroxyl radical (OH) with VOC. Despite the importance, a full understanding of the chlorine cycling and its impacts in the atmosphere remains unclear, particularly in urban environment. Our recent findings have shown that the presence of reactive halogen compounds (such as bromine and iodine) can change our understanding on the chlorine cycling in the atmosphere. Here, we will present the vital chlorine species observations and current understanding of reactive chlorine cycling in the urban atmosphere of China, and further discuss on the future challenges of reactive chlorine chemistry.
AS11-A044
Estimation of Tail Pipe and Non-tailpipe Emissions for Seven Non-attainment Cities in the Indian State of Punjab from the Ground-based Activity Data and their Comparison with the Existing Global Emission Inventories EDGAR and ECLIPSE
Arpit KATIYAR#+, Sri KOTA
Indian Institute of Technology Delhi, India
The global emission inventories of Emission Data Base for Global Atmospheric research (EDGAR) and Evaluating the Climate and Air Quality Impacts of Short-Lived Pollutants (ECLIPSE) uses top-down approach considers the total fuel consumed or the number of vehicles registered, to estimate vehicular emissions in India. However, this might not represent the actual traffic emissions in a city. Therefore, the following study aims to estimate the vehicular emissions for the year 2019 using bottom-up approach for seven cities in Punjab, India viz. Jalandhar, Patiala, Mandi Gobindgarh, Khanna, Dera Baba Nanak, Naya Nangal and Dera Bassi. The traffic volume data for two wheelers, three wheelers, four wheelers, light commercial vehicles, heavy commercial vehicles, buses, and others (tractors etc.) were calculated at twenty-five pre-identified locations in all the cities. Jalandhar which had the maximum traffic volume data, contributes to 8.02 kt/day PM10 and 3.54 kt/day PM2.5 vehicular emissions (tail pipe and non-tail pipe emissions combined) respectively. The silt loading value observed for the seven cities lie in the range of 0.89 to 9.86 g/m2. The study also compares the total estimated vehicular emissions with EDGAR and ECLIPSE global emission inventories. This study signifies the importance of bottom-up approach for the combined vehicular emissions. It is expected to provide an insight in the scientific community on the need for developing local emission inventories to devise city specific action plans for combating the air pollution.
AS11-A048
Seasonal Variation and Health Risk Assessment of PM2.5 Bound Heavy Metals: A Field and Comparative Study of Two Indian Cities
Yash JAIN#+, Sri KOTA, Vivek KUMAR
Indian Institute of Technology Delhi, India
Air pollution, especially PM2.5, is a significant environmental health concern globally, particularly in the Indian subcontinent. A minor proportion of PM2.5 is comprised of heavy metals, that can be toxic even at low concentrations, such as Cr, Cd, As, Pb, and Ni. Scientific evidence has illustrated that these metals can accumulate in adipose tissue and the circulatory system of the human body, leading to potential adverse effects on the digestive, cardiovascular, and central nervous systems, and may also act as a co-factor in the development of other diseases. This study focuses on the seasonal variation and health risk assessment of PM2.5 bound heavy metals in two north Indian cities, Alwar and Amritsar in the states of Rajasthan and Punjab respectively. The study was conducted through a combination of field measurements and comparative analysis. PM2.5 samples were collected during summer and winter seasons in both cities and analyzed for the presence of heavy metals using ICP-MS. The health risk assessment was carried out to understand the risk associated from the exposure to PM2.5 and heavy metals to the population, particularly in terms of respiratory and cardiovascular diseases.
AS11-A049
Atmospheric Assimilation Capacity of Non-attainment City in Southern India
Manuj SHARMA1+, Suresh JAIN2,1#
1Indian Institute of Technology Tirupati, India, 2Indian Institute of Technology Delhi, India
This study evaluated the Atmospheric Assimilation Capacity (AAC) of Vijayawada city in Andhra Pradesh, India. Emission inventory of 1 × 1 km2 resolution was used to estimate the emission load of PM10, PM2.5, SO2 and NOx under the Business as Usual (BAU) and Alternative (ALT) scenarios for the year 2030 compared to the reference year 2021. Subsequently, the emission load was fed into the AERMOD view v9.7.0 dispersion model to simulate the concentration of the pollutants in various scenarios for the city sources. The study reported the city's overall emission load of PM10~5648 tonnes/day, PM2.5~2131 tonnes/day, SO2~1378 tonnes/day and highest for NOx~8912 tonnes/day. PM10, PM2.5 and SO2 emissions were projected to increase by 36%, 22% and 11%, respectively, compared to a 14% decline in NOx emission load between the reference year and BAU 2030. For ALT 2030, the simulation of control and abetment measures resulted in a 16% decline in PM10 and a 23% decline in PM2.5. Implementing progressive measures in the transportation and industrial sectors also projected a significant decrease in gaseous emission load. Annual city average projected PM10 and PM2.5 concentrations reported the exceedance of Indian National Ambient Air Quality Standards (NAAQS) that resulted in reduced AAC due to an increase of 24% and 15% concentrations under the BAU 2030 scenario. However, the stringent implementation of ALT scenarios reported a high AAC with 16%, 24% and 38% decline in PM10, PM2.5 and NOx concentration, respectively. Among urban sources, construction and road dust were the prominent contributors to the city's PM10 emission load, whereas transportation and coal-burning industries contributed significantly to PM2.5, NOx and SO2, respectively. Such measures will help improve the air quality and livability of the city.
AS11-A050
Assessment of the Impact of Meteorological and Emission Variations on Winter PM2.5 Over the North China Plain in 2018-2020
Huiyun DU#+, Xueshun CHEN, Jie LI
Chinese Academy of Sciences, China
Air quality in Beijing-Tianjin-Hebei and its surrounding regions has been significantly improved during the Three-Year Action Plan for Winning the Battle Against Air Pollution from 2018 to 2020. The effectiveness of anthropogenic emissions reduction on PM2.5 over the North China Plain remains unclear. In this study, the Nested Air Quality Model System and observations were used to quantitatively examine the contribution of meteorological and emission variations to autumn-winter (November to February) PM2.5 concentrations in Beijing and its surrounding regions from 2018 to 2020. The model reproduced the temporal evolution of atmospheric pollutants and components well. The results showed that the observed mean PM2.5 concentrations during the winter were reduced by 15% and 29% in 2019 and 2020, respectively, compared with that in 2018. In 2019, the meteorological conditions over the Beijing-Tianjin-Hebei (BTH) region were poor, causing an increase of PM2.5 by 7.6% in BTH and 11% in Beijing; therefore, the control of air pollutant emission compensated for the unfavorable influence of meteorology and emission reduction was the decisive factor for PM2.5 reduction; In 2020, the meteorological conditions were relatively favorable, and the changes in meteorological factors and emission reduction led to a decrease in PM2.5 concentration by 18.6% and 10.5%, respectively, compared to 2018. Emission reduction also contributed to decrease in nitrate, ammonium, organic matter, element carbon and precursors. This work confirmed the obvious environmental benefit of pollution control measures from 2018 to 2020.
AS11-A052
Probabilistic Assessment of Spatiotemporal Air Quality in Taiwan Using Multivariate Indicator Kriging
Cheng-Shin JANG#+
Kainan University, Taiwan
Recently, because the fine particulate matter (PM2.5) concentrations monitored in Taiwan have substantially decreased due to less long-range transport of air pollutants in East Asia and the COVID-19 pandemic outbreak, many environmental groups have suggested that Taiwan’s Environmental Protection Administration should adjust the current regulatory standard for PM2.5 to an annual average of 12 μg/m3, which would accord with that of the United States. Thus, to determine whether such a regulatory adjustment is needed, assessing air quality on the basis of spatiotemporal PM2.5 distributions is critical for establishing risk maps and maintaining human health. This study spatiotemporally characterized the air quality in Taiwan by using multivariate indicator kriging (MVIK) according to current Taiwanese and US regulatory standards for annual average PM2.5 concentrations (i.e., 15 and 12 μg/m3, respectively). First, long-term PM2.5 concentrations were statistically analyzed to determine recent stable temporal PM2.5 data. Multivariate integration was implemented using the 2019-2021 and 2020-2022 PM2.5 data. MVIK was then adopted for modeling probabilities according to the two standards. Finally, compared with PM2.5 observations, quantile estimates based on the probabilities were employed to determine the optimal classifications for establishing risk maps of different PM2.5 standards. Suitable regulatory standards for PM2.5 are discussed according to risk classification maps. The results indicated that the multivariate integration of temporal PM2.5 data used in MVIK can effectively streamline the analytic process. The multivariate integration of 3-year PM2.5 data was suitable for the assessment of adjusting a regulatory standard for annual average PM2.5. The air quality in the Central, Yunchianan, and Kaoping air quality regions was found to pose high risks to human health due to long durations of high levels of PM2.5 concentrations. Adjusting the regulatory standard of annual average PM2.5 in Taiwan to 12 μg/m3 would be inappropriate at this time.
AS11-A053
The Optical Properties and CCN Activities of Black Carbon by Mixed Atmospheric Secondary Pollutants Coating
Cheng YUAN#+, Yan MA
Nanjing University of Information Science & Technology, China
Previous lab studies have suggested that other non-BC pollutants can promote the aging of black carbon (BC). However, most of the experiments were carried out with a single component mixed with BC, and the results obtained in previous studies under simple laboratory conditions may not be applicable to atmospheric relevant conditions. Here we will use a robust experimental system to perform a laboratory simulation of the internal mixing of flame-generated BC aggregates with atmospheric-relevant secondary pollutants in a smoke chamber. The impact on BC optical properties and CCN activities from the concentration of pollutants, coating sequence, as well as relative humidity, will be investigated. Variations in particle size, mass, coating thickness, effective density, dynamic-shape-factor, chemical composition, optical properties and CCN activities were determined online by a suite of instruments. Accordingly, this study will help to attain a comprehensive and clear understanding of the effects of coatings on the morphology, optical properties and CCN activities of BC and provide a foundation for accurately predicting the radiative forcing of BC as well as its role in air pollution control and climate change.
AS11-A057
Estimations of Indirect and Direct Anthropogenic Dust Emission at the Global Scale
Junyan CHEN#+, Siyu CHEN, Jianping HUANG
Lanzhou University, China
Dust emission acts as a crucial part in the dust cycle that determines dust related processes at both regional and global scale, such as long-range transport, dry/wet deposition, and radiation forcing. However, most dust emission simulations utilizing dust emission scheme merely investigate natural dust, neglecting the contributions of anthropogenic dust induced by direct or indirect anthropogenic activities, resulting in great uncertainties in estimating dust emissions by previous numerical modelling. To comprehensively reproduce the anthropogenic dust emissions process, both “indirect” and “direct” anthropogenic dust emission schemes were constructed to simulate anthropogenic dust emissions originated from diverse kinds of source regions in the study. Results showed that using both indirect and direct anthropogenic dust emission schemes show good performance on reproducing the spatio-temporal distributions of anthropogenic dust at the global scale during 2007–2010. The natural dust sources contributed 81.0%(6.34 ± 0.31 μg m−2 s−1) of the global dust emissions and the anthropogenic contributed 19.0%(1.01 ± 0.07 μg m−2 s−1) of the residual. The anthropogenic dust emissions concentrate in semi-arid, semi-humid and humid regions and generally fluctuated between 0.1 and 10 μg m−2 s−1. Anthropogenic dust accounted for about 42.99% of the total dust emission in the semi-arid areas. In semi-humid and humid areas, represented by cities, direct anthropogenic dust emissions are much higher in developing regions than in developed regions. This study provides a basis for accurately estimating dust emissions, further studying the radiation forcing and climate effects of dust.
AS11-A059
The Nord Stream Pipeline Gas Leaks Released Approximately 220,000 Tonnes of Methane Into the Atmosphere
Mengwei JIA#+, Fei JIANG, Fei LI
Nanjing University, China
Sudden mega natural gas leaks of two Nord Stream pipelines in the Baltic Sea (Denmark) occurred from late September to early October 2022, releasing large amounts of methane into the atmosphere. We inferred the methane emissions of this event based on surface in situ observations using two inversion methods and two meteorological reanalysis datasets, supplemented with satellite-based observations. We concluded that approximately 220 ± 30 Gg of methane was released from September 26 to October 1, 2022. This figure is about 0.08% and 85% of global and Danish annual anthropogenic methane emissions, respectively, and comparable to the annual anthropogenic methane emission in Austria. It surpasses the Aliso Canyon gas leak (100 Gg) that occurred in California in 2015, making the Nord Stream leak the largest gas leak ever reported.
AS11-A060
Observations of NOx, O3, CO, VOCs, and PM in an Urban Region in Taiwan During the Chinese New Year
Jonalyn MADRIAGA1,2#+, Charles CHOU1, Tse-Tsung HO1
1Academia Sinica, Taiwan, 2National Central University, Taiwan
Air quality especially in urban regions is known to be highly influenced by anthropogenic activities (e.g. vehicle engine combustion, industrial processes, solvent use, etc.). The Chinese New Year (CNY) is a well-celebrated festivity in Taiwan and anthropogenic behavior in the region changes during this time - people are on holiday vacation, there is a probable decrease in manufacturing operations, and some people celebrate it with fireworks and firecrackers. In this study, we investigated the effect of CNY on the air quality in the region particularly in terms of VOCs, PM, NOx, CO, and O3. The hourly ambient measurements were done at Urban Air Pollution Research Station, Taichung City, Central Taiwan from January 9 to February 8, 2023. The sampling period was subdivided into three periods, the pre-CNY (Jan 9-19), the CNY (Jan 20-29), and the post-CNY (Jan 30- Feb 8). Results showed a significant decrease in the concentrations of the measured CO and VOCs particularly of benzene, toluene, xylene/ethylbenzene, and trimethylbenzene during the CNY period. In particular, the sum of BTX average concentrations was 11.83 ppbv, 2.60 ppbv, and 10.97 ppbv for pre-CNY, CNY, and post-CNY, respectively. PM 2.5 concentrations also showed a huge decrease during the CNY period (20.46±3.48 µg/m3) as compared to pre-CNY (27.68±14.18 µg/m3) and post-CNY (25.70±5.58 µg/m3). NOx is also found to be lowest during the CNY period (6.28±2.56 ppbv), as compared to pre-CNY (15.26 ±7.32 ppbv) and post-CNY (15.38±9.12 ppbv). CO, BTX, and NOx are known to be tracers of vehicle emissions hence the decrease can be mainly attributed to the low traffic in the area during the CNY holiday. Meanwhile, ozone concentration did not vary that much which is subject to further analysis. Diurnal variations during each period will also be investigated to further understand the observed measurements.
AS11-A062
Atmospheric Dry Deposition of N-alkanes at an Urban Site in Indo-Gangetic Plain
Shweta SINGH+, Monika J. KULSHRESTHA #
CSIR-National Physical Laboratory, India
The present study investigated the seasonal trend and source attribution of n-alkanes in dry deposition during 2021 at an urban site in Indo-Gangetic Plain i.e., Delhi. Dry deposition samples (n=30) were collected weekly on 24 hourly basis (except COVID lockdown). The samples were extracted in methanol and analyzed for n-alkanes (C21-C40) using Gas Chromatograph-Mass Spectrometer. However, only C21-C31 n-alkane homologues could be quantified in the samples. The annual average dry deposition flux of total n-alkanes was 51.5±4.5 µg/m2/day following the seasonal trend as winter (75.6, n=9) > post-monsoon (61.8, n=7) > summer (34.3, n=6) > monsoon (28.4, n=8). The seasonal variability in deposition fluxes of total n-alkanes was more pronounced during winter and post-monsoon due to higher emissions arising from burning of woods for domestic heating and biomass burning respectively. The micrometeorology of the region also aids to the formation of shallow planetary boundary layer resulting in accumulation of the pollutants during this period. The drastic decline in the average dry deposition flux of total n-alkanes during summer could be due to volatilization of the n-alkanes at high temperature during summer season. The minimum deposition flux of total n-alkanes during monsoon provides the insights on the wet scavenging of the atmospheric pollutants. The molecular distribution of ≤C25 n-alkane homologues with maxima at C23 and C25 indicates the signature for vehicular emissions while the odd-even predominance of the >C27 n-alkanes homologues with maxima at C29 suggests the prevalence of biogenic sources. The annual CPI value (1.9±0.1) confirms the presence of mixed emission sources coming from fossil fuel burning and biogenic emissions at the sampling site. Concentration Weighted Trajectory (CWT) showed the prevalence of long-range transport from Arabian, Gulf, Myanmar and Indo-Gangetic Plains during summer and monsoon while prominent local and regional sources during winter and post-monsoon seasons.
AS12-A002
Eastward Propagating Planetary Waves Observed Using the SuperDARN Meteor Radar Network
Patrick ESPY1,2#+, Tina MIRZAAMIN1, Yvan ORSOLINI3, Christian RHODES4
1Norwegian University of Science and Technology, Norway, 2University of Bergen, Norway, 3Norwegian Institute for Air Research, Norway, 4Naval Research Laboratory, Space Science Division, United States
The SuperDARN network of meteor radars near 60o N have been used in a number of studies to characterize the climatology of planetary waves (PW) in the mesosphere and lower thermosphere (MLT). Classically, planetary waves are considered to propagate westward relative to the background flow due to planetary vorticity. However, instabilities in the zonal-mean flow produce vorticity gradients that provide a rich spectrum of PWs generated in-situ in stratosphere and mesosphere, including eastward propagating PW. Such instabilities are generally associated with sudden stratospheric warming (SSW) events, and eastward propagating planetary waves (EPW) have typically been associated with SSW. Here we present both super-posed epoch analyses of EPW during SSW as well as an extensive climatology of EPW during winter seasons from 2007 to 2019 using the SuperDARN meteor network. The details of the analysis to extract the EPW will be presented as well as the results showing that while EPW do occur during SSW events, their presence in the MLT is ubiquitous throughout the winter season.
AS12-A008
Particle Precipitation Effects on the Global Secondary Ozone Distribution
Lise E. MURBERG1, Tiril LØVSET2, Yvan ORSOLINI1, Jia JIA2,3#+, Patrick ESPY2,4, Cornelius Csar Jude SALINAS5,6, Jae LEE5, Dong WU5, Jiarong ZHANG7
1Norwegian Institute for Air Research, Norway, 2Norwegian University of Science and Technology, Norway, 3Birkeland Centre for Space Science, Norway, 4University of Bergen, Norway, 5NASA Goddard Space Flight Center, United States, 6University of Maryland, Baltimore County, United States, 7Coastal Carolina University, United States
The secondary ozone layer is a global peak in ozone abundance in the upper mesosphere-lower thermosphere (UMLT) around 90-95 km. The effect of energetic particle precipitation (EPP) from geomagnetic processes on this UMLT ozone has not been well studied. In this research we investigated how the secondary ozone response to EPP from the Microwave Limb Sounder (MLS) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Aura and TIMED satellites, respectively. In addition, the Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension and specified dynamics (SD-WACCM-X) was used to characterize the residual circulation during EPP events. By comparing ozone and circulation changes under High- and low-Ap conditions, we report regions of secondary ozone enhancement or deficit across low, mid and high latitudes as a result of circulation and transport changes induced by EPP.
AS12-A010
The “Keystone" Mission Concept for an Upper Atmosphere Explorer
Daniel GERBER1,2#+, John PLANE3, Franz-Josef LUEBKEN4, Patrick ESPY5,6, Christian VON SAVIGNY7, Dan MARSH3, David JACKSON8, Donal MURTAGH9, Ladislav REZAC10, Brian ELLISON1,2, Alexander VALAVANIS3, Neil BOWLES11
1UK Research and Innovation, United Kingdom, 2The Science and Technology Facilities Council-RAL Space, United Kingdom, 3University of Leeds, United Kingdom, 4Leibniz-Institute of Atmospheric Physics, Germany, 5Norwegian University of Science and Technology, Norway, 6University of Bergen, Norway, 7University of Greifswald, Germany, 8Met Office, United Kingdom, 9Chalmers University of Technology, Sweden, 10Max Planck Institute for Solar System Research, Germany, 11University of Oxford, United Kingdom
Keystone is a mission concept for a limb sounding satellite to explore the upper mesosphere and lower thermosphere, as well as the ionosphere. Keystone was a candidate missions for the ESA Earth Explorer 11 Call (EE-11). It’s a maturation of the EE-10 and EE-9 mission concept LOCUS. In its present form Keystone comprises of three instruments: A Supra-THz radiometer, an infrared radiometer, and a UVIS spectrometer.The infrared radiometer has four channels at 15um (CO2), 9.6um (O3), 5.3um (NO), and 4.3um (CO2). The UVIS spectrometer ranges from 230nm-780nm (O, O2, O3, O+, M/Mg+, Fe/Fe+, and Temperature). These two instruments are a continuation of upper atmospheric measurements such as MIPAS, HiRDLS or SABER, and OSIRIS, SCIAMACHY or ICON/GOLD, respectively. Keystone addresses the looming gap in upper atmospheric measurements at these wavelengths. The novelty of the Keystone mission is the heterodyne Supra-THz sounder with frequencies of 770GHz (O2), 1.1THz (NO,CO), 2THz (O), 3.5THz (OH), and 4.7THz (O). The THz instrument - made possible at these very high frequencies by novel quantum cascade laser (QCL) local oscillators - will provide vertical profiles of its target species. Prime among these is the elusive atomic oxygen (O), which is the kingpin of upper atmospheric chemistry and energy balance. Atomic oxygen is the missing keystone in the interpretation of both infrared and UVIS measurements. The unique combination of the three Keystone instruments presents a strong and novel synergy. By resolving age old questions - e.g., the conundrum of the quenching rate of CO2 with O - Keystone will significantly improve our understanding of the upper mesosphere and thermosphere, the least well-known region of the atmosphere, maybe the entire planet.
AS18-A003
On the Alleged Tropical Cyclogenesis Induced by a Pre-existing Tropical Cyclone
Kenji YAMAUCHI1, Kosuke ITO2#+
1University of the Ryukyus, Japan, 2Kyoto University, Japan
It has been believed that a strong pre-existing tropical cyclone (TC) can contribute to the genesis of another TC to the east or southeast in the western North Pacific through the Rossby wave dispersion (Ritchie and Holland, 1999; Li et al. 2006). However, these TCs are usually observed in the easterly wind where the stationary Rossby wave cannot exist, and a well-coordinated numerical experiment has not been conducted to elucidate the impact of a pre-existing TC. Therefore, we conducted a set of numerical simulations in which a pre-existing TC is removed sufficiently prior to the genesis of a subsequent TC. It turned out that a subsequent TC was generated even without a pre-existing TC in all 10 simulations for a pre-existing TC case according to the genesis environment database of Fudeyasu and Yoshida (2018). Also, the removal of a pre-existing TC hardly affects the intensity of a subsequent TC. This type of a TC is typically located south of a subtropical high, where the horizontal cyclonic shear prevails from west to east widely. Further analysis showed that these TCs were frequently observed in MJO phase 7, El Nino, and positive SST anomaly to the east of the western North Pacific. These are favorable for the genesis of a TC in the broad area of the western North Pacific. In other words, the characteristics are simply explained by the favorable condition in a broader area for the genesis of two TCs in which an eastern TC is generated later because the SST is lower in the east of the western North Pacific, not necessarily relying on the Rossby wave dispersion from a pre-existing TC.
AS18-A006
Are You Typhoon Ready? - Typhoon Ready System -
Woo-Sik JUNG#+, Hana NA
Inje University, Korea, South
Analysing the intensity of typhoons that have affected Korea over the past ten years revealed that half of them were very strong typhoons (with a maximum wind speed of 44 m or more per second). In particular, one of the four typhoons had a maximum wind speed of more than 55 m/s, which is the superpower level newly established in 2021. As such, the typhoons affecting Korea are gradually getting stronger. The World Meteorological Organization (2021) has highlighted that the world will be exposed to risks from complex weather disasters rather than single weather disasters. In particular, weather disasters caused by typhoons are not a single phenomenon, such as strong winds, heavy rains, and tsunamis, but natural disasters that can have simultaneous adverse effects on air quality; therefore, preparation and evaluation are required. Accordingly, the National Weather Service (NWS) declared a paradigm shift for Weather-Ready Nation (WRN), an influence-based weather information service to support decision-making. This is a national strategic plan to minimise damage by acting in advance against the effects of extreme weather events (such as heavy snow, tornadoes, hurricanes, floods, and droughts). Researchers have established partnerships with the NWS WRN and AMBASSADOR and are conducting research to predict the impact of typhoons in Korea. In line with this, this study intends to establish and introduce the Typhoon-Ready System (TRS), which produces pre-disaster information (risk) on complex weather disasters associated with typhoons across Korea and in each detailed area. We believe that this system can be used as a countermeasure to the typhoon climate crisis on the Korean Peninsula. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2020R1F1A1068738)
AS18-A014
Increase in Tropical Cyclone Rain Rate with Translation Speed
Shifei TU1#+, Johnny CHAN2,3, Jianjun XU1, Quanjia ZHONG4, Wen ZHOU5, Yu ZHANG1
1Guangdong Ocean University, China, 2Asia-Pacific Typhoon Collaborative Research Center, China, 3City University of Hong Kong, Hong Kong SAR, 4Chinese Academy of Sciences, China, 5Fudan University, China
In general, tropical cyclone (TC) rainfall accumulation usually decreases with faster TC translation speed but increases with heavier rain rate. However, how the TC rain rate changes with translation speed is unclear. Here we show that, in all TC basins, the average TC rain rate significantly increases with translation speed. On average, the rain rate in a fast-moving TC is 24% higher than in a slow one. This difference increases with TC intensity, with category 3–5 TCs having a 42% increase while tropical depressions exhibit only a 9% increase. The increase in the average TC rain rate with translation speed is mainly caused by the TC net inflow in the lower troposphere, as well as vertical wind shear. These findings have important implications not only for a deeper understanding of rain rate changes in a translating TC but also for short-term forecasts of TC rainfall and disaster preparedness.
AS18-A018
Simulation and Projection of Tropical Cyclone Activities Over the Western North Pacific by CMIP6 HighResMIP
Yulian TANG+, Jingliang HUANGFU#, Ronghui HUANG
Chinese Academy of Sciences, China
This study assesses the relative impacts of model resolutions, tropical cyclone (TC) trackers, and ocean coupling on simulating TC climatology over the western North Pacific (WNP) based on six Coupled Model Intercomparison Project phase 6 (CMIP6) High-Resolution Model Intercomparison Project (HighResMIP) models from 1979 to 2014. The HighResMIP multimodel ensemble (MME) analysis shows that the high resolution has a higher Taylor skill score II (S2) in both temporal and spatial patterns of TC genesis frequency and accumulated cyclone energy (ACE) than the low resolution. In contrast, the TempestExtremes tracker (coupled run) results in a higher S2 in temporal patterns but a lower S2 in spatial patterns than the TRACK tracker (uncoupled run). Among the three factors, increased resolution leads to the greatest improvement in S2 in both temporal and spatial patterns. Furthermore, this study investigates the projections of future TC activity over the WNP by HighResMIP under the SSP5–8.5 scenario. Overall, HighResMIP MMEs project a decrease in the genesis frequency, track density, and ACE of all TCs, with the high-resolution, TRACK tracker, and uncoupled run showing greater magnitude. The high-resolution MMEs, using both trackers, project an increase in the genesis frequency and ACE of intense TCs in the coupled run. Moreover, TC track density and ACE show a larger poleward migration in the coupled run than in the uncoupled run, consistent with the significant surface warming in the northern WNP.
AS18-A028
Effects of Megacities on Tropical Cyclone Precipitation Over Pearl River Delta, China
Yukun YANG#+
Nanjing University, China
Land cover changes and anthropogenic emissions cause by megacities can modulate convection and precipitation of the landfalling storms. In this study, we investigate the influence of megacity (the Pearl River Delta) on Typhoon Nida (2016) using the Weather Research and Forecasting model coupling with Chemistry (WRF-Chem). By changing the landuse type and initial anthropogenic emissions, the results suggest that megacity significantly enhances rainfall in outer-rainband in downstream area of the Pearl River Delta (PRD), with the land effect more significant than anthropogenic emissions. Urban land modifies the convection in the downstream area of PRD by enhancing vertical velocity, generating more sensible heat fluxes, and further promoting ice phase microphysical processes. The effect of anthropogenic emissions becomes evident after intensifying vertical convection, accelerating the conversion of hydrometeors into precipitation and further increasing precipitation in this region.
AS18-A029
An Observational Study of Quasi-Periodic Lightning Activity in the Inner Core of Super Typhoon Hato (2017) Before Landfall
Yuanyuan XU1#+, Hao HUANG1, Qingqing LI2
1Nanjing University, China, 2Nanjing University of Information Science & Technology, China
In 2017, Super Typhoon Hato was characterized by pronounced convective asymmetries in its inner core immediately before landfall in China. Together with the asymmetric convection, quasi-periodic lightning activities occurred concurrently, with a period of approximately 3 hours. This study discussed the characteristics of short-cycle lightning activity and corresponding polarimetric quantities in the inner core of Super Typhoon Hato (2017) before its landfall. Although the strongest inner-core convection was located persistently in the downshear and downshear-left quadrants, the lightning bursts behaved quasi-periodically with a cycle of about 3 hours. The analysis revealed that wavenumber-2 vortex Rossby waves (VRWs) were present in the inner core, propagating cyclonically and intensifying downshear left. When the positive perturbation of the VRWs was coupled with the VWS-forced convective enhancement, the local convection was significantly reinforced. Moreover, the slanted updrafts intensified by the phase-locking between VRW activity and convection strengthened by VWS can invigorate the growth of graupel, probably through riming processes, and further enhance the charge separation and lightning production immediately outside the eyewall. The invigorated graupel growth accompanied by lightning outbreaks can enhance surface precipitation and more efficient warm-rain growth below the melting layer. The radar observations demonstrated that when other VRWs were excited and propagated to the left side of the shear, the abovementioned phase-locking occurred again, leading to increased volumes of graupel and updrafts near the eyewall and short-cycle lightning bursts.
AS18-A033
Track Deflection of a Tropical Cyclone Past a Mountain Range as Explored by Idealized Simulations
Po-Chen LIN#+, Ching-Yuang HUANG
National Central University, Taiwan
An idealized WRF model is used to investigate the track evolution of a tropical cyclone approaching westward at different departure positions toward an elongated mesoscale mountain (mimicking Taiwan) at different orientation angles (denoted by A0 and A90 for south-north and east-west orientations herein). The track deflection is primarily controlled by the meridional departure position as well as the ratio of the vortex size and effective terrain length (the aspect ratio, or the nondimensional vortex size). For a lengthy mountain range (A0) with the smallest aspect ratio, the cyclone track will be significantly deflected counterclockwise (northward) when the cyclone is closing to the terrain. The counterclockwise deflection ahead of the mountain is much enhanced as the aspect ratio is much larger as in A90 (a shallow mountain range). However, the counterclockwise deflection is stronger as the mountain range of A0 is rotated by 45 degrees counterclockwise rather than clockwise despite the same aspect ratio. Due to such counterclockwise paths, the tracks at later times may turn southward to the leeside of the terrain and thus clutter near the same location. When departing south of the terrain, the upstream cyclone may somewhat be deflected southward before taking a counterclockwise path (thus northward). The degree of the track deflection is also reduced by increased meridional departure and basic flow intensity. Only when the terrain blocking becomes significant as in A0, the cyclone can be deflected northward but then rapidly southward near landfall, due to the channeling effect of the induced strong northerly jet along the mountain base. The wavenumber-1 vortex flow and potential vorticity (PV) budget analysis has helped explain the track deflection that is dominated by horizontal PV advection in comparison to both vertical PV advection and differential diabatic heating that somewhat modulate the tracks in the vicinity of the mountain.
AS18-A038
Statistical Seasonal Forecasting of Tropical Cyclone Utilizing Preseason Predictors
Chak Wai LO1+, Kelvin T. F. CHAN1#, Oscar Y. W. ZHANG2, Minglin ZHENG3, Lifeng XU1
1Sun Yat-sen University, China, 2The Hong Kong University of Science and Technology, Hong Kong SAR, 3National University of Defense Technology, China
Predicting tropical cyclone activities has been a topic of great interest and research. Nonetheless, most of the existing forecast models are closed-source, and the prediction performance is fair, especially the early prediction. Therefore, we employ statistical methods to develop “simpler, more open and accurate” (compared with the existing) seasonal forecast models and build an open-source operational platform for providing seasonal forecasting service, focusing on the western North Pacific (including South China Sea, East Asia and Southeast Asia). In this conference, we will promote 3 statistical seasonal forecasting models (namely SYSU models) to predict the number of tropical storms over the western North Pacific, and number of tropical storms that could make landfall on South China and East China by every mid of May using preseason factors as the predictors.
AS18-A039
Future Changes in Tropical Cyclone Activity Over the Western North Pacific by Chlorophyll Under Global Warming
Han-Kyoung KIM1+, Jong-Yeon PARK1#, Doosun PARK2, Sang-Wook YEH3, Jong-Seong KUG4, Jun-Hyuk SON5
1Jeonbuk National University, Korea, South, 2Kyungpook National University, Korea, South, 3Hanyang University, Korea, South, 4Pohang University of Science and Technology, Korea, South, 5Korea Power Exchange, Korea, South
Chlorophyll can significantly affect climate systems through changes in atmospheric and oceanic circulation, and therefore could impact tropical cyclone (TC) activity. Here, we use future ensemble simulations performed by an Earth system model to investigate the biological feedback by future chlorophyll change on the large-scale environmental conditions that affect TCs over the western North Pacific (WNP). For this investigation, two sets of global warming simulations are conducted with activated and inactivated marine ecosystem models. Compared to the inactivated simulation, the increased chlorophyll concentration over the tropical eastern Pacific is a crucial feature in the activated simulation. The increased chlorophyll concentration over the tropical eastern Pacific strengthens the upper ocean’s stratification, inducing shoaling of the mixed layer and intensification of the equatorial upwelling. These changes lead to a La Niña-like SST warming pattern, hence intensifying Walker and local Hadley circulations. The intensified local Hadley circulation derives upper-level westerly and lower-level easterly wind anomalies in the southeastern part of the WNP (SE-WNP), resulting in a significant decrease in the vertical wind shear and a significant increase in the genesis potential index (GPI) in that region. The enhanced GPI in the SE-WNP and further TC properties are reproduced using a high-resolution atmospheric model simulation, which supports our Earth system model results. Our results can contribute to the understanding of the projection of TC activity in other basins because the tropical Pacific SST variability can influence the climate conditions in other basins. Acknowledgments: This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (No. 2020R1A4A3079510).
AS18-A040
Estimation of Tropical Cyclone Intensity Based on Deep Learning Using Two Geostationary Satellite Data
Hye-Yoon JUNG1+, Il-Ju MOON2#, Dong-Hoon KIM2
1Interdisciplinary Postgraduate Program in Marine Meteorology, Korea, South, 2Jeju National University, Korea, South
One of nature's most violent and destructive occurrences, tropical cyclones (TCs) have a significant negative influence on society and the economy. Reducing TC damages requires precise TC intensity estimation and forecasting. The Geo-KOMPSAT-2A (GK2A) satellite images are used in this study to create the Convolutional Neural Network (CNN) model, which estimates the TC intensity in the western North Pacific (NWP). Given the insufficient GK2A data, the present study adapts a transfer learning technique, which uses information learned from available Communication, Ocean, and Meteorological Satellite (COMS) satellite images, to develop the model. When the two data are similar, the transfer learning technique performs well because it can enhance learning a new task by transferring knowledge from a task that has already been trained. The present CNN model based on transfer learning approaches lowered mean absolute error (MAE) by up to 27% compared to GK2A-only learning because COMS and GK2A satellite data use similar infrared channels. Our findings imply that transfer learning, combined with additional satellite data or artificial intelligence methods, will represent a significant advance in the estimation of TC intensity. Acknowledgement. This research was supported by Korea Institute of Marine Science & Technology Promotion(KIMST) funded by the Ministry of Oceans and Fisheries, Korea (20180447, Improvements of ocean prediction accuracy using numerical modeling and artificial intelligence technology) and the National Research Foundation of Korea(NRF) grant funded by the Korea government(Ministry of Science and ICT)(No. RS-2022-00144325)
AS18-A042
Utilizing a Causal Discovery to Identify Robust Tropical Cyclone Predictors Across the North Indian Ocean
Akshay kumar SAGAR1#+, Arun CHAKRABORTY1, Swadhin BEHERA2, Abhishek KUMAR1, Pankaj KUMAR1
1Indian Institute of Technology Kharagpur, India, 2Japan Agency for Marine-Earth Science and Technology, Japan
Each year, there are significant variations in both the activity of tropical cyclones (TC) and the damage they do. The reduction of wear and human loss brought on by tropical cyclones (TCs) depends heavily on the longer-term forecasting of TCs. In this study, the primary development regions and precursors responsible for the genesis and intensification of TC were identified using a Causal-network-based approach. However, there are numerous worldwide links that connect all of the severe occurrences. Therefore, using this Causal Effect Network (CEN) based algorithm, it is examined how tropical cyclone teleconnection and correlation with El Nino Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and North Atlantic Oscillation (NAO) during the satellite era (1980-2020) over the North Indian Ocean (NIO) basins. The most appropriate metric for cyclone energy is Accumulated Cyclone Energy (ACE); its correlation with the various factors is investigated. We examined the variation in TCs activity during all three phases (positive, negative, and neutral phases). The findings indicate an upward trend in ACE over the NIO region during that particular time period. The most intense cyclones last longer at this time, but they are less frequent overall. After 1997, ACE begins to change, and it continues to climb sharply. Analysis of the sea surface temperature (SST), and vertical wind shear (VWS) between 850 and 250 hPa is conducted, and it demonstrates ACE's positive changes and variability. Causal graphs show the contributing regions with a good significance level. These findings could lead to a better understanding of the teleconnections between the events in the atmosphere or the ocean, and better tropical cyclone forecasting could lessen the damage brought on by TCs and shows how other phenomena affect the different parameters.
AS18-A043
Diurnal Variations on the Initiation Time and Intensification Rate of Rapidly Intensifying Tropical Cyclones
Xinyan ZHANG#+, Weixin XU
Sun Yat-sen University, China
The outbreak of intense convection in the inner core of tropical cyclones (TCs) may promote the rapid intensification of TCs. It is well known that TC inner-core convection varies diurnally and usually peaks in the early morning. Recent studies found that TC intensification rate (INTRATE) also exhibits a diurnal cycle that is in phase with the inner-core deep convection. These studies further proposed that the nocturnally enhanced inner-core convection may simultaneously promote the TC INTRATE. However, the previously reported diurnal amplitude of INTRATE is just marginal (5-10%). It is unknown whether and how the diurnal cycle of the INTRATE varies among different TC intensifying periods. Also, whether the initial time of the TC intensification exhibits an evident diurnal signal? Based on the analysis of 30-year TC track data, this study investigates whether and how the INTRATE and initiation time of intensifying TCs vary diurnally. TC intensifying periods are classified into slowly intensifying (SI) and rapidly intensifying (RI) events. RI events last ~42 h on average, much longer than SI events. Interestingly, TC intensification including RI is the most likely to initiate at 00-06 LT. The INTRATE shows limited diurnal variations, especially for SI and RI events (amplitude of 6-8%), and the peak INTRATE time shifts from the morning in non-RI events to the late afternoon for RI events. Inner-core convection of all intensifying events maximizes in the early morning, in phase with the peak initiation time. However, the INTRATE and inner-core convection in RI TCs are diurnally out of phase, suggesting that the nocturnally enhanced inner-core convection may play a role in triggering TC intensification (e.g., RI), but not maximizing the INTRATE.
AS18-A046
Validation of Typhoon Forecasts Simulated by the Numerical Weather Prediction Models and Analysis of its Biases
Kyeong-Chan SHIN1#+, Hyun-Mi KIM2, Jung-Rim LEE1, Seong-Hee WON1, Hyun-Soo LEE1
1Korea Meteorological Administration, Korea, South, 2Korea Meteorological Administration , Korea, South
Typhoons are one of the deadliest natural disasters causing damage to human life and property so accurate forecasts of typhoons are crucial to reducing the risks. For the prediction of typhoons, forecasts from numerical weather prediction models (NWPs) are fundamental, and operational centers largely rely on NWPs. In the meantime, NWP techniques for the course and intensity of typhoons have been developed over many years, but prediction errors still exist so it is necessary to verify errors and analyze biases of the NWPs.
In this presentation, the prediction errors of the typhoon information from various kinds of NWPs were calculated compared to RSMC Tokyo's best track, and the tendencies of each NWP were analyzed for recent four years. The NWP used in the analysis were the global and ensemble models of KMA, NCEP, US Navy, ECMWF, and JMA.
As a result, DPEs show different validation scores every year due to the characteristics of typhoon phenomena. For example, there are many typhoons with unusual paths in 2021, so the accuracy is relatively low in all models. In this case, it is hard to predict both tracks and intensity so the model consensus didn't agree well. Also, the spatial distribution of biases such as along-track biases (ATBs), cross-track biases (CTBs), and biases of maximum wind speed are analyzed. NWPs tend to simulate typhoons' track leftward and slower, and intensity weaker. Moreover, some distinct biases are shown for the different regions in the western North Pacific area.
AS18-A060
The Effect of Low Salinity Water on Interaction Between Ocean and Typhoon Chaba (2016) Passing Over East China Sea
Woojin CHO#+, Jinyoung PARK, Dong-Hyun CHA
Ulsan National Institute of Science and Technology, Korea, South
The decreasing sea surface temperature with increasing latitude is one of the causes of the weakening of the intensity of typhoons moving to mid-latitudes. In 2016, the track of Typhoon Chaba passed over the East China Sea where the sea surface temperature (SST) was abnormally high; hence, Chaba maintained a relatively high intensity. The Changiang River discharge peaked in early July and gradually decreased before typhoon Chaba approached. Conversely, the salinity in the East China Sea was minimal in early August and increased. Moreover, the positive anomaly area of sea surface temperature in the East China Sea matched the negative anomaly area of sea surface salinity related to Changiang river discharge. Changiang freshwater inflow and sea surface temperature in the East China Sea had 30 days lagged positive correlation. Therefore, based on these, we determined that the increase in the East China Sea's sea surface temperature is associated with the outflow of the Changiang River. In this study, we investigated the sea surface temperature warming due to ocean stratification caused by Changiang diluted water and following typhoon-ocean interaction after warming and ocean stratification using a coupled atmosphere-ocean modeling system. The freshwater inflow caused ocean stratification in the East China Sea and formed a barrier layer, and this barrier layer inhibited the vertical mixing and energy transport between the surface and the thermocline and led to sea surface warming. As a result, the stabilized ocean structure restricted sea surface cooling induced by typhoon-forced upwelling and turbulent mixing. In conclusion, this study discovered the mechanism that maintains the intensity of TCs moving northward using ocean-atmosphere couple modeling, which may be used to improve the performance of ocean-atmosphere couple modeling in predicting the intensity of TCs.
AS18-A071
Multi-scale Characteristics of an Extreme Rain Event in Shandong Province Produced by Typhoon Lekima (2019)
Yi ZHANG#+
Nanjing University, China
Super typhoon Lekima (2019) is the 5th strongest typhoon to make landfall in mainland China since 1949. After its landfall, typhoon Lekima moved northward along the coastline, resulting in an extreme rain event in Shandong Province that makes the largest precipitation within the available meteorological records. A WRF model simulation that well produces the track and intensity of typhoon Lekima and the spatio-temporal evolution of the rainfall is used to analyze the multi-scale characteristics of the extreme rain event. Different from the typhoon precipitation occurred at low latitudes, the extreme rain event occurred in midlatitudes were influenced by the interactions of midlatitude synoptic systems and typhoon circulation, especially with five mesoscale rainbands. The midlatitude synoptic systems, mainly including the upper-tropospheric jet, the Western North Pacific Subtropical High, the mid-latitude trough, the low-level jets and typhoon Krosa (2019), allow typhoon Lekima to maintain its intensity after landfall and provide favorable kinematic, thermodynamic and moisture conditions for the heavy rainfall in Shandong. Based on the evolution of the mesoscale rainbands, the extreme rain event can be divided into three stages. The first stage can be classified as a distant rainfall, which was affected by two convective rainbands associated with boundary layer processes. The second stage had the largest precipitation, featured the formation of a frontal zone in Shandong interacting with typhoon Lekima. The third stage had weakened rainfall and was directly influenced by the spiral rainband of typhoon Lekima.
AS21-A003
Rate-dependent Hysteresis of Atlantic Meridional Overturning Circulation
Soon-Il AN1#, Hyo-Jeong KIM2, Soong-Ki KIM1+
1Yonsei University, Korea, South, 2City University of Hong Kong, Hong Kong SAR
AMOC is a typical density-driven thermocline circulation, featuring a clockwise basin-scale meridional overturning in the present climate. A freshwater hosing over a north Atlantic leads to slowing down or even collapse of AMOC, while in order to recover the typical state of AMOC, over-reduction of freshwater than that used for a collapse of AMOC is required. This indicates an existence of multiple equilibria state, which can be visualized by a hysteresis diagram showing a relationship between freshwater forcing (FWF) and AMOC intensity. Here, we explored AMOC hysteresis dependency on a frequency of FWF using a Stommel’s box model. Results showed that the abrupt transitions between typical state and collapse state were lagged as FWF changes faster. Furthermore, as the complexity of system increases, the detailed hysteresis feature was modified. Especially, the abruptness in transition during decreasing FWF phase was more distinct than that during increasing FWF phase. This asymmetric hysteresis response to FWF was attributed to nonlinear salt-advection feedback, which is mainly operating on a typical state but does not on a collapse state of AMOC.
AS21-A004
Hysteresis of ENSO Teleconnection in CO2 Removal Experiment
Su-Hyeon SHIN1#+, Soon-Il AN1, Jae-Heung PARK2, Jongsoo SHIN3, Chao LIU1
1Yonsei University, Korea, South, 2Seoul National University, Korea, South, 3Pohang University of Science and Technology, Korea, South
ENSO (El Nino – Southern Oscillation) is the most dominant mode on Earth, having tremendous impacts on nature and human society. Since the Earth’s climate is changing continuously by anthropogenic greenhouse gas emissions, understanding of the ENSO teleconnection in changing climate is needed. In this study, based on an idealized CO2 ramp-up and ramp-down climate model experiment, which increases CO2 concentration by 1% per year (ramp-up) and decreases symmetrically (ramp-down), we show how the ENSO teleconnection responds in the CO2 removal experiment and what factors induce the changes in ENSO teleconnection. ENSO teleconnection patterns in midlatitude 500hPa geopotential height anomalies show the systematic eastward-shift tendency during both the ramp-up and -down periods, and thus the ENSO teleconnection change shows significant hysteresis behavior. To investigate main cause of this hysteresis, we analyze the correlation between the changes in ENSO characteristics including standard deviation, skewness, phase shift, and its convection center, and the NINO3.4-500hPa geopotential height regression. The results reveal that the change in ENSO teleconnection in each region was correlated with the different factors. Especially, the ENSO skewness change was related to changes in ENSO teleconnections near North and South America, and the phase change in ENSO induces the change of ENSO teleconnection near Africa, the Aleutian region, and Australia. Through this study, it is expected that we could predict changes in ENSO teleconnection in each region according to changes in ENSO characteristics due to climate change.
AS21-A005
Future Projection of Arctic Sea Ice Constrained by Observed Sea Ice
Hyeonui CHOE+, Soon-Il AN#
Yonsei University, Korea, South
Arctic amplification refers the fastest warming of Arctic region due to Anthropogenic increase of greenhouse gases. The main cause of this fast warming is known as so-call ‘ice-albedo feedback’ especially associated with the reducing sea ice area over the Arctic. Therefore, in near future, the emergence of seasonal sea ice free would be expected. The prediction of sea ice free timing is challenging because of complexity in atmosphere-ocean-ice system. In particular, it is known that the fast disappearing of Arctic sea ice in early 21 centaury was not well simulated in most of the advanced climate models. Therefore, the correction of the future projection in Arctic sea ice using observations is necessary. Here, using 1979-2020 analysis data, we calibrate the present-day melting rate of Arctic sea ice of climate models participating CMIP6 and apply for the future projection. Results show that the sea ice free year obtained from this calibration is earlier than that without calibration. This study may provide more accurate information in future Arctic sea ice change.
AS21-A008
Hiatus of Near-surface Wind Speed in March Over China
Huishuang YUAN1+, Zhibo LI2, Youli CHANG1#
1Yunnan University, China, 2Peking University, China
Variability in near-surface wind speed (NSWS) has significant impact for understanding the hydrological cycle, environmental governance, and renewable energy development. Global NSWS shows the stilling and reversal phenomenon before and after 2011, but lacks the attention on the discrepancy of monthly NSWS annual changes. Our study employed daily observational data from the China Meteorological Administration to investigate changes in monthly NSWS across China. We found a consistent decline in NSWS before 2011, after which March was marked by a hiatus in increasing wind. The hiatus phenomenon was mostly attributed to the southern displacement and weakening of the East Asian subtropical jet in March, which weakened the meridional temperature gradient and decreased transient eddy activity at mid-latitudes over China. Furthermore, the decline in atmospheric baroclinity suppressed anticyclonic anomalies, leading to a breakdown in NSWS.
AS21-A011
Hysteresis of Southern Ocean Temperature in a Carbon Dioxide Removal Scenario Through Warm Water Upwelling and Sea Ice-albedo Feedback
Jongsoo SHIN1#+, Jong-Seong KUG2, Soon-Il AN3, Jae-Heung PARK4
1Woods Hole Oceanographic Institution, United States, 2Pohang University of Science and Technology, Korea, South, 3Yonsei University, Korea, South, 4Seoul National University, Korea, South
The Southern Ocean plays a crucial role in regulating global temperature through its interactions with the atmosphere, ocean, and sea ice. However, its thermostatic impact on greenhouse gas forcing is not well understood. This study conducted idealized CO2 ramp-up and -down experiments and found that the hysteretic behavior of the air-sea interaction through declining sea ice has a substantial impact on the hysteresis of the Southern Ocean temperature. The reduced sea ice due to increased CO2 supplies heat to the ocean through the sea-ice albedo feedback. In the Weddell Sea, where a large amount of sea ice exists, the reduction in sea ice makes open water, which leads to continuous heat release from the ocean to the atmosphere, thereby raising the temperature of the atmosphere. The loss of heat at the ocean surface is supplemented by accumulated heat in the ocean subsurface during the period of increased CO2, thus inhibiting the formation of sea ice. These feedback processes keep the Southern Ocean warm for a prolonged period, suggesting that once human-induced warming starts, it may take a long time for the Southern Ocean to return to its initial state, or irreversible changes may occur. Acknowledgments: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF-2018R1A5A1024958). The CESM simulation was carried out on the supercomputer supported by the National Center for Meteorological Supercomputer of Korea Meteorological Administration (KMA), the National Supercomputing center with supercomputing resources, associated technical support (KSC-2021-CHA-0030), and the Korea Research Environment Open NETwork (KREONET).
AS21-A012
The Relationship Between the Mass Term of Atmospheric Angular Momentum and Water Vapor Mass
Wirid BIRASTRI1,2#+, Tri Wahyu HADI1, Nining Sari NINGSIH1
1Bandung Institute of Technology, Indonesia, 2Institut Teknologi Sumatera, Indonesia
In this study, the relationship between atmospheric angular momentum's mass term (MΩ) and water vapor has been investigated using four reanalysis datasets for the years 1950–2020: ERA5, ERA-20C, JRA55, and NCEP/NCAR. The four reanalysis datasets revealed a consistent positive long-term trend in global MΩ anomalies, while also identified shifts in the trend from negative to more positive around 1970s. Meanwhile, analysis of global water vapor trends shows that there is an additional mass of water vapor, which results in variations in water vapor surface pressure (pw) of about ~0.3 mbar. Changes in the contribution of water vapor to MΩ after the 1970s were calculated based on the anomaly of MΩw (estimated from pw) relative to the climatology value of 1970-1979. It can be shown that the MΩw anomalies tend to be positive after the 1970s period. In addition, the ratio of the MΩw anomalies relative to MΩ suggests a change in the pattern of the contribution of water vapor to MΩ, which is indicated by the fluctuation of this percentage every ten years. The highest contribution of water vapor to MΩ occurred in the equatorial region during 2010-2020, with a ratio of MΩw to the global MΩ at 25-50%. The stability of the relationship between MΩ and water vapor is examined using the 20 year shifting window correlation. The relationship between MΩ and water vapor is more consistent on annual and interannual scales, especially in the equatorial region, but there are inconsistencies for longer time scales. Inconsistency in the interdecadal scale is characterized by a lower statistical coherence from the mid-1980s to the 2000s, which indicates a decrease in the contribution of water vapor to MΩ. These results suggest that water vapor alone is insufficient to account for the increase in MΩ over the period.
AS23-A013
Development of High-resolution Chemical Reanalysis System Over Northeast Asia and South Korea Based on the Korean Air Chemistry Modeling System (K_ACheMS RA)
Dogyeong LEE+, Chul Han SONG#
Gwangju Institute of Science and Technology, Korea, South
Chemical reanalysis data, produced by assimilating observations into numerical model backgrounds, can provide systematically best-estimated and spatiotemporally continuous information on atmospheric chemical components. Nowadays, the chemical reanalysis data have been actively released by several institutes such as Copernicus Atmospheric Modeling and Monitoring Service (CAMS) reanalysis from European Centre for Medium-Range Weather Forecasts (ECMWF) and Modern-Era Retrospective Analysis for Research and Applications Aerosol Reanalysis (MERRAero) from National Aeronautics and Space Administration Global Modeling and Assimilation Office (NASA-GMAO). However, because such datasets are produced by using global chemistry transport models (e.g., C-IFS and GEOS-5/GOCART), they could not be suitable for air quality studies on a regional scale due to low spatial resolutions and poor parameterizations for regional atmospheric environments. Therefore, in this study, a chemical reanalysis system has been developed based on the Korean Air Chemistry Modeling system (hereafter ‘K_ACheMS RA’) for regional air quality study over northeast Asia and South Korea with high resolutions of 15×15 km2 and 5×5 km2, respectively. The K_ACheMS RA mainly consists of the following: i) the Community Multi-scale Air Quality version 5.2.1 (CMAQ v5.2.1) model updated for atmospheric conditions over northeast Asia by Gwangju Institute of Science and Technology (GIST) science team (i.e., CMAQ vG model); ii) the Weather Research and Forecasting (WRF) model with high resolutions of topography, land cover, and forest type datasets over South Korea; and iii) an advanced data assimilation system based on an ensemble Kalman Filter (EnKF). Ground-based observations, such as PM2.5, CO, O3, NO2, and SO2 in South Korea, China, and Japan, are assimilated into the CMAQ vG model every 3 hours. The evaluations of the produced reanalysis data by comparison with AIR KOREA observations in South Korea will be shown in this presentation.
AS23-A020
Total Column Water Vapor Retrieval Over Asia From Geostationary Environment Monitoring Spectrometer (GEMS) Visible Spectra
Hyeji CHA1+, Jhoon KIM1#, Heesung CHONG2, Gonzalo GONZÁLEZ ABAD2, Dha Hyun AHN1, Sangseo PARK3, Ja-Ho KOO1, Won-Jin LEE4, Deok-Rae KIM4
1Yonsei University, Korea, South, 2Center for Astrophysics | Harvard & Smithsonian, United States, 3Ulsan National Institute of Science and Technology, Korea, South, 4National Institute of Environmental Research, Korea, South
Water vapor is one of the greenhouse gases which has strong impacts on the weather and climate. Despite of long-term observation by meteorological satellites, the physical/chemical process related to water vapor is not well understood. Therefore, continuous, accurate monitoring of atmospheric water vapor is essential for understanding its interaction with weather and climate. From this purpose, water vapor retrieval algorithm is newly developed in the visible channels (435.0 – 467.0 nm) for the Geostationary Environment Monitoring Spectrometer (GEMS) onboard the GEO-KOMPSAT 2B satellite. The algorithm is based on the direct fitting method, which is originally developed by Smithsonian Astrophysical Observatory (SAO). The GEMS Total Column Water Vapor (TCWV) algorithm conducts the two-step approach, which are comprised of spectral fitting of slant column densities (SCDs), and conversion of the retrieved SCDs to vertical column densities (VCDs) using air mass factors (AMFs). The TCWV retrieval algorithm is applied to GEMS observations for all months in 2021. The retrieval results show not only the monthly variations of water vapor but also its diurnal cycle over Asia. TCWV derived from GEMS observations are validated by comparing with AERONET precipitable water data. The results agree well with the reference data and the linear regression parameters tend to vary with time. If high quality water vapor product can be produced from this study, it is expected to improve our understanding of water vapor-related chemical and physical processes.
AS23-A021
Near-real-time PM2.5 Prediction Over East Asia Using Geostationary Aerosol Monitors of GOCI-II and Machine Learning
Jeewoo LEE#+, Jhoon KIM
Yonsei University, Korea, South
Air-suspended particulate matter under the size of 2.5 μm (PM2.5) has been known to be a potential cause of asthma and increase of mortality even when exposed in the short-term (U.S. EPA, 2019). East Asian countries, where concerns on PM2.5 has been high, have provided ground-based PM2.5 observation data, but is spatially confined to the monitoring site. To overcome this limitation, aerosol optical properties (AOPs) derived from space-borne satellites have been used to estimate PM2.5 concentrations over a broad area. In this study, we used a near-real-time random forest model with AOPs from a geostationary satellite, GEO-KOMPSAT-2B, to nowcast the ground-level PM2.5 in East Asia. Hourly AOPs of the second generation Geostationary Ocean Color Imager-II (GOCI-II) retrieved by Yonsei aerosol retrieval algorithm were used as a major input, while meteorological and atmospheric chemical composition data from numerical models, and spatially and temporally inverse-weighted PM2.5 were used as ancillary variables. AOPs of GOCI-II are provided in 2.5 km spatial resolution and 10 times hourly in the daytime, for which ancillary variables were collocated in terms of time and space. The synthetic minority over-sampling technique (SMOTE) was adopted to compensate for the low occurrences of high-PM2.5 cases. Validation against ground-based PM2.5 networks has shown a good model performance in terms of R2 and RMSE. Hourly validation yielded a high R2 in the daytime, and a higher R2 in the winter. The predicted hourly PM2.5 of this study can be used as an real-time indicator for outdoor air quality and public health.
AS23-A022
Estimating Emissions from Crop Residue Open Burning in Central China Using Statistical Models Combined with Satellite Observations
Rong LI#+
Hubei University, China
Crop residues open burning has significant adverse effects on regional air quality, climate change and human health. Accurate crop residues open burning emission inventory can provide an important basis for objective and comprehensive analysis of biomass combustion, strengthening biomass combustion control and improving air quality. In this study, based on the VIIRS 375 m thermal anomaly products, land use data and high-resolution remote sensing images of sky maps, the spatiotemporal characteristics of crop residues open burning in central China were extracted and analyzed. Based on statistical models and satellite data, the high-resolution emission inventory in central China was estimated. The results showed that the number of crop residues open burning points showed a significant downward trend from 2012 to 2020, and the number of fire points remained at a low level after 2015. The peak period of straw burning is mainly concentrated during the harvest season. However, under strict control measures, staggered burning in some areas has led to several scattered small peaks of straw burning in spring and winter. The black carbon (BC), organic carbon (OC), sulfur dioxide (SO2), nitric oxide (NOX), carbon monoxide (CO), carbon dioxide (CO2), fine particulate matter (PM2.5), coarse particulate matter (PM10), ammonia-ammonia (NH3), methane (CH4) and non-methane volatile organic compounds (NMVOC) emitted by crop residues open burning were 34.84, 149.72, 41.06, 90.11, 2640.97, 78094.91, respectively. 485.17, 481.05, 35.21, 246.38 and 499.59 Gg. Among them, the largest contributor was rice, followed by wheat, rapeseed and maize, with a contribution rate of 35.34–64.07%, 15.78–34.71%, 9.12–25.56% and 5.69–14.06%, respectively.
AS23-A023
Distribution and Trend of Surface Ozone Pollution in the South Korea
Taegyung LEE1, Ja-Ho KOO1#, Junsu GIL2, Donghee LEE1+
1Yonsei University, Korea, South, 2Korea University, Korea, South
Recently, we found that the ozone concentration in the South Korea is increasing rapidly. To examine the general pattern of this ozone increasing trend in South Korea, we conducted the Mann-Kendall trend analysis using the monthly 10th, 50th, and 90th percentile of ozone level for all monitoring sites in South Korea for the purpose to see the tendency of background, mean, and polluted cases. We used the long-term (2003-2021) observation of ozone provided from the Korea Air Quality Network Program of the National Institute of Environmental Research. There are numerous monitoring stations > 400 in South Korea, but here we only use ozone data at 122 stations, which have the large number of data enough (In case that 75% days in a year have a daily representative ozone value). As a result, we found that some spatiotemporal differences. First, ozone level in the coastal region is higher than the inland region. Second, surface ozone is highest in spring (March to May). Third, ozone peak occurs in the afternoon (14-16 local time). Fourth, all trends of 10th, 50th, and 90th percentile of ozone in whole South Korea show large increasing pattern: 0.11, 0.71, and 0.75 ppbv per year, respectively. The increasing trend of 50th and 90th percentile is significant in most of the stations. The reason of large ozone increase in coastal region will be more investigated in the future. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2020R1C1C1011624).
AS23-A024
The COVID-19 Lockdowns Improved Air Quality in Asia as Revealed by Observations and Model Simulations
Claire YU1#+, Mian CHIN2, Huisheng BIAN3, Qian TAN4, Peter COLARCO5, Hongbin YU2
1Richard Montgomery High School, United States, 2NASA Goddard Space Flight Center, United States, 3University of Maryland, Baltimore County, United States, 4Bay Area Environmental Research Institute, United States, 5National Aeronautics and Space Administration, United States
When the COVID-19 pandemic emerged in 2020, numerous countries across the world went into shutdowns, which caused an absence of frequent transportation, manufacturing, and other factors considered anthropogenic, or man-made, sources of aerosol emissions. Some cities in China, notably Shanghai, went through additional shutdowns from April to June 2022. This study investigates the hypothesis that the COVID-19 lockdowns in Asia resulted in large reductions in anthropogenic emissions, which may have improved air quality. We collected both satellite and ground-based observations to examine and compare levels of aerosol optical depth (AOD) and PM2.5 during pre-pandemic climatology and in the pandemic years; AOD data was taken from the MODIS Aqua satellite and PM2.5 data of nine sites from the US Embassies and Consulates in China and India. In comparison to the pre-pandemic climatology, MODIS data clearly demonstrated significant reductions of AOD, corresponding to their individual lockdown periods. Time series of PM2.5 data revealed that PM2.5 per lockdown period reached a record low. The level of PM2.5 during the lockdown was lower than the pre-pandemic average of the same period by 30-50%, depending on location. We also used AOD and PM2.5 data from NASA GEOS model to analyze simulations of pre-pandemic climatology (2010-2019), plus two simulations in 2020: the business as usual (BAU) run with 2019 anthropogenic emissions, and the COVID run with adjusted anthropogenic emissions accounting for COVID lockdowns. The relative differences in GEOS AOD and PM2.5 between the 2020 COVID run and pre-pandemic climatology were consistent with the observations but at a smaller magnitude, suggesting that the model may have underestimated lockdown-related emission reductions. These findings show strong indication that the effects of the COVID-19 lockdowns likely have left their mark in the atmosphere, improving the air quality.
AS23-A030
Interpretation of Daytime and Nighttime Difference in AOD Over China Based on CALIOP Observations and GEOS-Chem Simulation
Xiaodong JIANG1#+, Yi WANG1, Minghui TAO2, Lu GUI1
1China University of Geosciences, China, 2Chinese Academy of Sciences, China
Aerosols play a crucial role in climate change by absorbing and scattering radiation. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite sensor can provide aerosol extinction coefficient profile observations during daytime as well as nighttime, which helps us understand the horizontal and vertical distribution of aerosols throughout the day and night. CALIOP observes that nighttime AOD is up to ~0.2 larger than daytime during 2007-2019 over the populated North China Plain, Central China, Sichuan Basin and South China. CALIOP AOD at nighttime is significantly larger than daytime below 4 km, while the difference is much smaller above 4 km. We then use the GEOS-Chem chemical transport model to simulate aerosol distribution in 2019, the year with the largest relative CALIOP AOD difference between daytime and nighttime. The simulation results also show that nighttime AOD is greater than daytime. However, from the perspective of vertical distribution, nighttime AOD is greater than daytime only below 1 km, and nighttime and daytime AOD profiles almost coincide above 1 km. Meanwhile, the results of three sensitivity experiments show that higher relative humidity due to lower temperature at nighttime than daytime leads to hygroscopic growth enhancement, which plays a decisive role in the difference between daytime and nighttime AOD compared with the emission, chemical processes, and transport factors.
AS23-A042
Dust Emission Changes in Northern China from 2016-2029 Under SSP2-4.5 Scenario
Jianqi ZHAO+, Xiaoyan MA#, Rong TIAN
Nanjing University of Information Science & Technology, China
In this study, the WRF-Chem model is used to simulate the dust emission change in northern China from 2016-2029. We first evaluated the ability of the five dust emission parameterization schemes in WRF-Chem to simulate dust processes in the study area through real-case simulations. The evaluation indicates that among the five schemes, the Shao01 scheme performs better than the others in simulating the emission flux, the spatial pattern of source region and the spatiotemporal variation of dust mass concentration, while the Shao11 scheme fails to simulate the dust process on soils of types loam and clay loam since it omits the importance of the fully disturbed particle size distribution. Simulation based on the Shao01 scheme shows that from 2016 to 2029, the amount of dust emission in the northwestern dust source region is higher than that in the northern dust source region. In addition, differences in topography and climate lead to differences in dust emission processes and their seasonal variations in the two regions. Seasonal mean dust emission fluxes in the northwestern and northern dust source regions from 2016 to 2029 show general decreasing trends, whereas some seasons show increasing trends. The dust emission flux in the northwestern dust region shows a weak increasing trend in spring and decreasing trends in summer, autumn, and winter. The dust emission flux in the northern dust source region shows decreasing trends in spring, summer, and winter and a weak increasing trend in autumn. Variation trends of dust emission fluxes in the two regions are dominated by the near-surface wind speed, whereas the vegetation fraction, precipitation, and surface temperature have important effects on the interannual fluctuation of dust emission fluxes.
AS23-A057
Air Pollution Monitoring in Singapore Using Ground-based Observations and Satellite Data
Peng YUAN SNG1, Efthymia PAVLIDOU2#+, Santo V. SALINAS1, Fernando SANTOS1, Boon Ning CHEW3
1National University of Singapore, Singapore, 2Meteorological Service Singapore, Singapore, 3Centre for Climate Research Singapore, Singapore
Air quality in Singapore is regularly monitored by the ground-based network of NEA and reflected in a composite air quality index derived by the concentrations of PM2.5, PM10, O3, NO2, and SO2. We focus on O3, NO2, and SO2 and study emissions on days within the period 2020-2023 when high levels of these pollutants were recorded. We use ground-based observations and data from satellite instruments to assess estimates of pollutant concentration, their spatiotemporal distribution, and potential indications of interactions. Finally, we discuss on complementary use of different sources of information to support diurnal air quality monitoring and better understand the local dynamics of air pollution.
AS23-A058
Greenhouse Gases Monitoring Over the East Asia by Satellite-based Observation
Byung-il LEE1#+, Junhyung HEO1, Myoung-Hee LEE1, Yoonjae KIM2, Young-Suk OH2, Sangwon JOO2
1Korea Meteorological Administration, Korea, South, 2National Institute of Meteorological Sciences, Korea, South
Greenhouse gases emitted by humans are a major cause of global warming. The concentration of GHGs has increased rapidly compared to pre-industrial times. The world is making efforts to reduce greenhouse gases, the Korean government has also declared carbon Net-zero, and has enacted and enforced the Zero Carbon Act to achieve this. The National Meteorological Satellite Center, Korea Meteorological Administration has analyzed satellite-based greenhouse gases to monitor climate change and support government’s achievement of Net-Zero, because objectively monitoring the spatio-temporal variability of greenhouse gases is so important.
NMSC/KMA validated the accuracy of satellite-based greenhouse gas within situ and TCCON retrieved CO2 from 2014 to 2021 in Anmyeon, the South Korea which is a GAW site. Both ground- and satellite-based CO2 showed a good agreement in their increasing trends with seasonal variations. However, satellite-based CO2 observed total column appear smaller than in situ observations affected by local sources due to observe near the surface, but agree well with TCCON observed the total column. The RMSD of GOSAT, and OCO2 with in situ and TCCON is estimated about 9.78, 10.47 and 2.40, 2.11 ppmv for a 1.0 degree × 1.0 degree spatial resolution on a daily time scale from January 2014 to December 2021. The results show that satellite-based products could be used greenhouse gases monitoring, but it needs to be verified with other sites data. We will present the detailed methods and results in the conference.
This work was funded by the Korea Meteorological Administration’s Research and Development Program “Technical Development on Weather Forecast Support and Convergence Service using Meteorological Satellites” under Grant (KMA2020-00120).
AS23-A059
Pandora Asia Network (PAN) of Status and Future Plan
Soi AHN1#+, Limseok CHANG2, Donghee KIM2
1National Institute of Environmental Research(NIER), Korea, South, 2National Institute of Environmental Research, Korea, South
A continuous collaboration is required to combat air pollution and natural disasters in Asia. The UN General Assembly adopted resolution A/RES/74/212 on “International Day of Clean Air for blue skies” in 2019 to strengthen international cooperation at the global, regional and subregional levels in various areas related to improving air quality. In accordance with the UN resolution, the project of PAPGAPi (PAN-Asia partnership for Geospatial Air Pollution information) was launched in 2020 by Ministry of Foreign Affairs of Korea in order to establish a joint-utilization platform of environmental data through the Pandora Asia Network(PAN) and environmental satellite(GEMS) data utilization system. At present, 5 countries (Thailand, Indonesia, Mongol, Laos, Cambodia) have signed a record of discussion with KOICA to join the PAN officially, and 3 countries (Vietnam, Philippines, Bangladeshi) are awaiting government approval. In addition, it will trying to negotiate with Asian countries (Singapore, Nepal, Bhutan, India) within the GEMS area. The PAN will complete to install 20 Pandora sites until 2023 and enter into regular operation in 2023. A robust PAN operation system is essential for seamless data production and active utilization which follows. The ESC of NIER will provide an opportunity for member organizations to share PAN progress to date and discuss future directions for long-term operations and PAN groups establishment. Also, it will operate and maintain the Pandora instruments in Asia and facilitate the application of GEMS data on air pollution.
AS23-A062
Top-down Derivation of Biomass Burning Particulate Matter Emissions from Different Biomes Using Himawari Fire Radiative Power Observations in ASEAN
Phoebe JULIAN1,2#+, Efthymia PAVLIDOU1, Boon Ning CHEW3, Chee-Kiat TEO3, Zhong Yi CHIA3, Hannah NGUYEN4, Martin WOOSTER4
1Meteorological Service Singapore, Singapore, 2Nanyang Technological University, Singapore, 3Centre for Climate Research Singapore, Singapore, 4King's College London, United Kingdom
Forest fires are a common occurrence throughout the ASEAN nations, often resulting in transboundary haze incidents and degraded air quality. Emissions from fires can be retrospectively estimated following bottom-up approaches, which require information on biomass density, fraction of above-ground biomass and burnt area estimates. Top-down alternative methodologies have been developed to bypass the uncertainty of such estimates and allow for near real-time monitoring. They utilise satellite-based Fire Radiative Power (FRP) and Aerosol Optical Depth (AOD) to calculate biome-specific smoke emissions coefficients (Ce) linking FRP directly to Total Particulate Matter (TPM) emissions. We apply a Top-down methodology on Himawari-based products to utilise the high frequency and the spatial resolution of the sensor; namely, the FRP product available from EUMETSAT’s Land Surface Satellite Applications Facility, and for the first time the AOD L2 product available from JAXA. We compare the coefficients we extract with those obtained from published literature and from available global datasets. We present emission estimates for fire locations across the North and South of ASEAN during 2019-2020 and use model-derived TPM as reference to evaluate our findings. We further compare emission estimates of different biomes, in order to get insights on the impact of different fire types on haze. Finally, we discuss on the challenges and the advantages of utilising geostationary satellite products for retrospective studies and operational monitoring in the local context of Southeast Asia.
AS23-A072
Estimating the Columnar Concentrations of Black Carbon Aerosols in China Using MODIS Products
Fangwen BAO1+, Ying LI1,2#
1Southern University of Science and Technology, China, 2Southern Marine Science and Engineering Guangdong Laboratory, China
Black carbon (BC), the strongest light-absorbing particle, is believed to play substantial roles in regional air quality and global climate change. In this study, taking advantage of the high quality of Moderate Resolution Imaging Spectroradiometer (MODIS) products, we developed a new algorithm to estimate the BC columnar concentrations over China by simulating the BC and non-BC aerosol mixing states in detail. The results show that our new algorithm produces a reliable estimation of BC aerosols, in which BC columnar concentrations and their related parameters (aerosol absorption and BC surface concentration) show reasonable agreements and low biases compared with ground-based measurements. The uncertainties of BC retrievals are mainly associated with the surface and aerosol assumptions used in the algorithm, ranging from -14% to 44% at higher aerosol optical depth (AOD>0.5). The proposed algorithm can improve the capability of space-borne aerosol remote sensing by successfully distinguishing BC from other aerosols. The acquired BC columnar concentrations enable the spatial pattern of serious BC aerosol pollution over East China to be characterized, showing that it exhibits higher levels in winter. These nationwide results are beneficial for estimating BC emissions, proposing mitigation strategies for air pollution, and potentially reducing the uncertainties of climate change studies.
AS24-A002
Improving the Accuracy of O3 Prediction of CMAQ with a Random Forest Model in the Yangtze River Delta Region, China
Kaili XIONG#+, Xiaodong XIE, Jianjiong MAO, Lin HUANG, Jingyi LI, Jianlin HU
Nanjing University of Information Science & Technology, China
Due to inherent errors in the chemical transport models, inaccuracies in the input data, and simplified chemical mechanisms, ozone (O3) predictions are often biased from observations. Accurate O3 predictions can better help assess its impacts on public health and facilitate the development of effective prevention and control measures. In this study, we used a random forest (RF) model to construct a bias-correction model to correct the bias in the predictions of hourly O3 (O3-1h), daily maximum 8-h O3 (O3-Max8h), and daily maximum 1-h O3 (O3-Max1h) concentrations from the Community Multi-Scale Air Quality (CMAQ) model in the Yangtze River Delta region. The results show that the RF model successfully captures the nonlinear response relationship between O3 and its influence factors, and has an outstanding performance in correcting the bias of O3 predictions. The normalized mean biases (NMBs) of O3-1h, O3-Max8h, and O3-Max1h decrease from 15.8%, 20.0%, and 17.0.% to 0.5%, −0.8%, and 0.1%, respectively; correlation coefficients increase from 0.78, 0.90, and 0.89 to 0.94, 0.95, and 0.94, respectively. For O3-1h and O3-Max8h, the original CMAQ model shows an obvious bias in the central and southern Zhejiang region, while the RF model decreases the NMB values from 54% to −1% and 34% to −4%, respectively. The O3-1h bias is mainly caused by the bias of nitrogen dioxide (NO2). Relative humidity and temperature (T) are also important factors that lead to the bias of O3. For high O3 concentrations, the T bias and O3 observations are the major reasons for the discrepancy between the model and the observations.
AS24-A004
Clustering Analysis of 24-hour Indoor Air Quality According to Facility Types in South Korea
Sun-Kyong HUR#+, KyongTae KIM, Ju-Won LEE, Soo Joeng JOEN, Boo-Hun CHOI
Kweather, Korea, South
This study attempts to classify the timeseries pattern of indoor air quality levels which tends to be different according to facility types. Indoor air quality data are obtained from Kweather, which company uses its self-developed air quality monitors installed nationwide to collect real-time observation data. Using this data, K-mean clustering analysis derive four distinct patterns (Group A, B, C, and D) based on 24-hour timeseries of PM10, PM2.5, CO2, noise and temperature from 186 monitors located in 11 facilities (apartment, school, childcare, hospital, sports center, senior center, senior care, office, library, study café, government building) for the year 2021. Group A shows relatively low concentration of PM10 up to 18 ㎍/㎥ while other groups show higher values of PM10 up to 23 ㎍/㎥. In addition, PM10 in Group B and D shows only one positive peak during 10-11 am while Group C show two PM peaks during 10-11 am and 20-21 am. While CO2 show one peak during 15-17 am for both Group B and D, the peak level of CO2 is higher for Group B (843 ppm) than Group D (570 ppm). Similarly, temperature, and noise show different levels for each four groups. Interestingly, Group A include large portions of air quality data from senior cares (49%), libraries (44%), sports centers (59%), apartments (44%), schools (66%) and childcares (38%). Meanwhile, Group B consists of only small portions of data from all facilities (~34%). Group C are mostly from hospitals (51%). Group D show common air quality patterns in senior center (45%), government buildings (47%), offices (40%), and study cafés (42%). This work was supported by Korea Environment Industry & Technology Institute (KEITI) through Prospective green technology innovation project, funded by Korea Ministry of Environment (MOE) (RE2022011054).
AS24-A005
Prediction of PM2.5 Concentration in 24 Hours Based on Hybrid Depth Neural Network
Mengfan TENG#+, Siwei LI
Wuhan University, China
Accurate prediction of the future PM2.5 concentration is basis for human health and ecological environmental protection. In recent years, deep neural network models show advantages in the prediction of PM2.5 concentration, but few of the studies can be able to achieve a credible prediction of future longer term PM2.5 concentration(6~24 hours). To solve this problem, this study constructs a novel hybrid prediction model by combining the empirical mode decomposition (EMD) method, sample entropy (SE) index and bidirectional long and short-term memory neural network (BiLSTM) to reliably predict PM2.5 concentration at 24 future consecutive moment. The results show that the hybrid model has better performance on PM2.5 prediction in the future, with R2=0.987, RMSE=2.77μg/m3 at next hour and R2=0.904, RMSE=7.51μg/m3 in the sixth hours. Compared with other deep learning models, this model can improve the prediction accuracy of PM2.5 concentration in the short term (within 6 hours) by at least 50%, and better capture the change trend of PM2.5 concentration in 6 to 24 hours. It can be used as an effective tool for long-term prediction of PM2.5 concentration.
AS24-A006
The Impact of Air Pollution Control on Inter-provincial Trade-associated Environmental Inequality
Jiaxin DONG+, Siwei LI#
Wuhan University, China
Inter-provincial trade may cause transfer of air pollutants and associated health risks, contributing to the issue of environmental inequality. Strengthened air pollution control in China over the past years has gained considerable benefits in reducing the air pollution and related health damage, while its effect in modulating the trade-associated environmental inequality is still unknown. Here we explore the inter-provincial environmental inequality in China and analyze the impact of air pollution control on the inequality, not only by traditional emissions-based index, but also based on the perspectives of premature deaths and economic losses. Although the inter-provincial transfer of pollutant emissions were substantially reduced due to air pollution control, the imbalance in distribution of pollutant emissions and value added in different provinces existed and even further aggravated from 2012 to 2017. In particular, Shanxi, Ningxia, Guizhou and other provinces contributed more to emissions than to GDP. Moreover, the exposure-based index suggested that air pollution control reduced the absolute and relative environmental inequality associated with human health risks due to inter-provincial transfer. The provincial 100 million RMB value added came at the cost of 5.46 premature deaths in 2012, which fell to 3.91 deaths in 2017. The average proportion of economic losses to value added of all transfers was 5% in 2012 and dropped to 3.6% in 2017. This study can provide a reference for inter-regional economic cooperation and joint air pollution control, making accurate inter-provincial compensation possible.
AS24-A009
Quantify the Responses of Nitrogen and Sulphur Deposition on NH3 Control by Machine Learning
Zhaoxin DONG#+, Jia XING, Shuxiao WANG, Dian DING
Tsinghua University, China
NH3 emission control is proved of great importance in reducing PM2.5 concentrations in China, while how it affects nitrogen/sulphur (N/S) deposition is still unclear. The fast development of machine learning provides a new method for understanding the effect of NH3 on N/S deposition by the imitation of 3-D model. This study develops a new response surface model by using the machine learning technique to quantify the responses of N/S deposition to NH3 emission control in the Yangtze River Delta, China. It is found that NH3 control has higher efficiency in reducing the N/S deposition than NOx and SO2 alone. The reduced N deposition response to NH3 emission abatement is higher in the north part of the YRD region whereas oxidized N deposition decreases sharply in the region with low N critical load. An unexpected co-benefit is found in reducing N deposition when we control the NH3 and NOx emission simultaneously. Compared with the sum effect of individual NH3 and NOx emission abatement, the extra benefits from the synergy controls account for 4.4% (1.23 kg N·ha-1·yr-1) of the total N deposition, of which 81% comes from the oxidized N deposition. The YRD region could receive the largest co-benefits with a 1:1 ratio of NOx: NH3 emission reduction. The NH3 emission control also changes the ratio of wet S deposition to dry S deposition and mitigates the wet S deposition. These findings highlight the effectiveness of NH3 emission control and suggest a multiple pollutant control strategy for reducing N/S deposition, which may be also appropriate for other regions in China and other countries.
AS24-A010
Estimating Carbon Dioxide Emissions on Roads Based on Deep Learning
Myeong-Gyun KIM#+, Hyo-Jong SONG
Myongji University, Korea, South
Greenhouse gases(GHGs), a major factor in climate change, are emitted from various sectors. Among them, GHGs emitted from the transportation sector account for the third-highest proportion of the energy. In 2018, GHG emissions in the transportation sector in Korea were about 98 million tons, accounting for 13.5% of the total emissions. Therefore, it is urgent to reduce GHGs in the transportation sector to achieve the national carbon neutral goal. In order to efficiently reduce GHGs in the transportation sector, emissions by region/road must be accurately calculated. However, currently, emissions are only measuring at the national level, so calculating emissions for each road remains a problem. This study aims to estimate traffic volume through deep learning and develop a model obtaining road carbon dioxide emission. Seoul, which has good data provision, was selected as a pilot destination. First, the traffic volume missing link is estimated, and the model used for this uses the measured traffic volume as a dependent variable, and the traffic volume of the measured link, which is a dependent variable, and the traffic speed and road characteristics, which are explanatory variables, are composed of the data of the estimation model. These data are provided by the Seoul TOPIS and ITS. Traffic volume estimation is implemented using the LSTM+DNN model, and MAE and MSE are used for verification. As a result, MAE is 205, which shows that it is quite good performance even though there is no traffic volume data in the explanatory variable. Then, the traffic volume estimated through this model is used to calculate carbon dioxide emissions by road. Although it is an initial level result, it is expected that efficient carbon emission reduction can be supported if a better emission calculation algorithm is developed by upgrading deep learning technology in the future.
AS24-A011
Particulate Matter Prediction and Shapley Value Interpretation Through a Deep Learning Model
Youngchae KWON#+
Myongji University, Korea, South
The adverse effects of particulate matter (PM) on public health are well known and the public are cautious of exposure to these air pollutants. This has led to the need for accurate particulate matter predictions and clear explanations of the mechanisms involved. This study collected and analyzed data to predict particulate matter concentrations at regular intervals in Korea. Automated synoptic observation system data (ASOS), real-time atmospheric observation data from Airkorea (Air), and GEO-KOMPSAT-2A (GK-2A) data were used. We also used deep learning which is useful for particulate matter predictions. The deep learning model used a neural network to predict PM with diameter less than 2.5 µm (PM2.5) and PM with diameter less than 10 µm (PM10) concentrations. To illustrate the results of the nonlinear model, we calculated the Shapley value using eXplanable Artificial Intelligence (XAI) in the SHapley Additive exPlanations (SHAP) library. The difference in analysis according to the diameter of aerosols was explained. was most affected by the previous day's value, and was most affected by sea level pressure (SLP). Furthermore, to analyze the contribution of features for each grid, Shapley values were normalized. Normalized Shapley values (NSV) were clustered and represented visually. was classified into three clusters and was classified into four clusters. when predicting each grid, we also confirmed whether the data on the adjacent grid points had high feature importance. Overall, the study summarizes how much SHAP analysis fits with the characteristics of generally known PM mechanisms.
AS24-A012
Development of PM2.5 and PM10 Prediction Models Using Artificial Intelligence, CMAQ, and Meteorology
Seong-il LEE#+, Hyo-Jong SONG
Myongji University, Korea, South
Air pollution is a big problem all over the world. It is important not only to reduce air pollutants, which are the causes, but also to predict them because they can be prepared for and prevented by making accurate predictions. Therefore, research on air pollutants continues to be conducted. Among them, we developed a model that predicts PM2.5 and PM10, studied how to continuously improve performance, and compared and analyzed with previous models. For the data, calculated values and meteorological data obtained through CMAQ were used as input data, and observation values were used as target data. The prepared data were applied to the grid model to make predictions, and compared and analyzed with observations using the previous model and CMAQ. In order to improve predictive performance, appropriate data from meteorological data were selected, preprocessed, and applied together with the data obtained from CMAQ. These activities have improved performance.
AS45-A003
Long-term Effects of Siberian Wildfire on Vertical Distributions of Hydrocarbons in UTLS Over East-Asia
Donghee LEE1+, Ja-Ho KOO1#, Patrick SHEESE2, Kaley WALKER2
1Yonsei University, Korea, South, 2University of Toronto, Canada
In this study, we examined the seasonal vertical pattern of six hydrocarbons (C2H2, C2H6, CH3OH, HCOOH, HCN, and HCHO) and carbon monoxide (CO) in the East Asian upper troposphere and lower stratosphere (UTLS) from 2004 to 2020. We used satellite data from Atmospheric Chemistry Experiments (ACE) – FTS version 4.1 to investigate seasonal hydrocarbons vertical pattern over East-Asia, and MODIS Level 2 active fire data (MOD14 and MYD14, and MCD64A1) and land cover product (MCD12C1) to analyze fire information along with land cover type over Siberia: fire count (FC), fire radiative power (FRP) and Burned Area (BA). we divided forest regions into 3 parts based on the MODIS land cover percentage. Since East-Asia often suffered from Siberia wildfire plume for summer, it is likely to see the large enhancement of hydrocarbon in summer (June to August). As expected, we found the summertime enhancement of hydrocarbons and CO volume mixing ratio at 8.5 to 13.5km. Around 10-13 km altitude, FC and BA in Siberia shows the highest correlation coefficients with HCN and CO in Northern China (R = ~0.5 to 0.6). Moreover, BA and HCN, CO vertical correlation indicate also significant. (R = ~ 0.5 at 10.5 km to 12.5km of altitude), meaning that the wildfire effect is almost reaching to the northern hemispheric tropopause. Since the lifetime of HCN and CO is rather long (at least a month), the atmospheric chemistry in the upper troposphere is largely affected by the plume of Siberian wildfire. If the Sibrian wildfire becomes more frequent related to the global warming trend, this connection may be more intensified in the future, where the necessity of further research lies. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2020R1C1C1011624).
AS46-A003
Statistical Analysis of Aviation Turbulence in Middle-upper Troposphere Over Japan
Yoshiaki MIYAMOTO1#+, Ayako MATSUMOTO2, Soshi ITO1
1Keio University, Japan, 2ANA HOLDINGS, Japan
This study examined the statistics of aviation turbulence that occurred in Japan between 2006 and 2018 by analyzing the Pilot Report (PIREP). In total, 81,639 turbulence events, with moderate or greater intensity, were reported over this period. The monthly number of turbulence has an annual periodical variation as observed in different regions by previous studies. The number of turbulence cases is high from March to June and low in July and August. Higher number of turbulence cases are experienced along the major flight routes in Japan, especially around Tokyo, for the active period between 9:00 and 20:00 local time. The number of cases of turbulence peaks when the flight reaches an altitude of 33000 ft (FL330), while it reduces when the flight altitude is less above FL380 and below FL280. The statistical features are not largely different among the four seasons; however, there are some exceptions. For instance, the number of turbulence is large in high altitudes in summer and small in low altitudes in winter. Considering the number of flights, it is evident that the frequency of turbulence is higher in altitudes between FL200 and FL350, whereas the flight number is high below FL200 and above FL350. The number of convectively induced turbulence is relatively large during the daytime in summer compared with the other seasons. Large number of mountain wave turbulence is observed around the mountainous region in fall and winter when the jet stream flows over Japan.
AS46-A005
Multi-model-based In-flight Icing Forecast Based on the Simplified Forecast Icing Potential (SFIP) Algorithm
Eun-Tae KIM#+, Jung-Hoon KIM
Seoul National University, Korea, South
Multi-model-based in-flight icing forecast based on the Simplified Forecast Icing Potential (SFIP) algorithm has been developed using two operating global Numerical Weather Prediction (NWP) models: the Unified Model-Global Data Assimilation and Data Prediction System (UM-GDAPS) from the Korean Meteorological Administration (KMA) and the Global Forecast System (GFS) from the National Centers for Environmental Prediction (NCEP). The SFIP is a fuzzy-logic algorithm calculating icing potential from temperature, relative humidity, vertical velocity, and cloud water content (liquid + ice) predicted directly by NWP model. The most important components of the SFIP algorithm are the membership functions and weight combinations, which have been optimized using icing pilot reports (PIREPs) from Oct 2015 to Jul 2018 for the two NWP models. The time-lagged ensemble (TLE) method is applied to combine the two NWP model-based SFIPs with five forecast lead times from 12 to 36 hours (6-hourly). The multi-model-based TLE prediction system provides two types of forecasts: deterministic and probabilistic. The deterministic icing forecasts provide an ensemble mean of SFIPs from the 10 ensemble forecast members. The probabilistic forecasts provide the relative frequency of the number of ensemble members among total members that exceed a specific threshold of severe icing potential at given grid point. All single- or multi-model-based systems are evaluated using the icing PIREPs and several icing cases observed by the Nara (meaning a nation in a native Korean) research aircraft operated by the KMA/National Institute of Meteorological Sciences (NIMS) in South Korea.
AS46-A007
Numerical Study of Near-cloud Turbulence Encounters Associated with Convective Clouds Over East Asia
Soo-Hyun KIM+, Jung-Hoon KIM#
Seoul National University, Korea, South
Turbulence associated with convective clouds is termed convectively induced turbulence (CIT). The CIT occurs within the cloud as well as in cloud-free air above or near convective clouds (near-cloud turbulence, NCT). Because in-cloud CIT can be detected from a visible cloud boundary, predicting NCT in advance is more significant for a safe air travel. Although there have been investigated generation mechanisms of NCT using numerical simulations and observations in the world, further studies on NCT frequently occurred over East Asia have been required. In this regard, current study examines two clusters of moderate-or-greater (MOG)-level turbulence occurred over East Asia using convection-permitting scale simulation. On 2 December 2019, a commercial aircraft traveling across the northern Pacific Ocean encountered MOG-level turbulence near convective clouds developed along well-organized surface front. The numerical simulation is conducted using the Advanced Research Weather Research and Forecasting model v4.3.3 with five domains with horizontal grid spacings from 9 to 0.11 km. It is found that there are convectively induced modifications in large-scale flow near turbulence incident regions: 1) strong bulk vertical wind shear is evident near downstream regions of deep convection and 2) areas of moist static instability. In vertical cross sections, it is found that strong vertical wind shear and flow deformation below and above enhanced jet due to deep convection exist. The current simulated results indicate that a combination of vertical wind shear, flow deformation, and convective gravity waves and their breaking can be related to the southern cluster of NCT cases. On the other hand, shear instability due to strong vertical wind shear mainly induced by enhanced upper-level jet may be associated with the northern cluster of NCT cases. The additional nesting with the fifth domain is conducted for detailed analyses and results will be presented in the conference.
AS46-A008
Regional Real-time Weather Prediction System Over Incheon International Airport Using WRF Model
Yujeong DO+, Hyeon-Ji LEE, Kyo-Sun LIM#
Kyungpook National University, Korea, South
This study introduces the regional real-time weather prediction system using Weather Research and Forecasting (WRF) model to support the aviation safety and investigates the impact of initial/boundary conditions and horizontal resolutions on the model simulations, especially on the low-level weather variables such as 2-m temperature, relative humidity, and 10-m wind speed and direction. The 6-hour interval forecast fields, that are generated by National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) and Korea Meteorological Administration (KMA) Korean Integrated Model (KIM), are utilized for the real-time model simulations. For the Sea Surface Temperature (SST), National Oceanic and Atmospheric Administration (NOAA) daily Optimum Interpolation SST (OISST) climatology data are incorporated. Three nested domains are constructed centering on Incheon international airport and horizontal resolutions are set as 10-km, 1-km, and 100-m grid spacing. The numerical experiments are carried out during a period of 24 hours starting at 00 UTC on each day of April 2021 when the monthly averaged wind speed was strongest through the year. With the introduced configuration, we can provide the climatological evaluation results of the real-time weather prediction system based on WRF model. From the comparison of model simulations with available observations at the selected weather observation stations over Yeong-Jong island where Incheon international airport is located and adjacent areas, we figure out that the simulation with the finer horizontal resolution captures the diurnal variability of temperature better than the one with the coarser horizontal resolution. In addition, the simulated wind speed under the finer resolution shows better agreement with the observations. More detailed results will be presented at the conference. This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2022-00410 and the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (RS-2023-00208394).
AS46-A009
Seasonal Variation of Environmental Fields of Aviation Turbulence in the Upper Level Around Japan
Soshi ITO1#+, Yoshiaki MIYAMOTO1, Yoshiyuki KAJIKAWA2
1Keio University, Japan, 2Kobe University, Japan
Turbulence is a major factor that hinders the safe navigation of aircraft. Various organizations and researchers attempt to predict turbulence, but it is difficult to accurately predict the location and time of turbulence. This is because the mechanism of turbulence generation and the environmental field at the time of generation are not fully understood. Because environmental fields vary depending on where they occur, regionally focused studies are needed. In this study around Japan, which has not been done very often, the objective was to determine the environmental fields during the occurrence of clear-air turbulence of moderate intensity in the upper levels by season. In addition, to clarify the relationship with the Baiu front, the analysis will be conducted in five seasonal divisions, with summer and June as independent months. We used the Pilot Report (PIREP), which is data reported by pilots on meteorological phenomena they encountered in flight, and Japan Meteorological Agency Mesoscale Reanalysis data (MANAL). The analysis period was 8 years, from 2010 - 2017. Based on stellar and topographic data, the cases of mountain wave turbulence and convective induced turbulence were excluded from PIREP. The analysis showed that the environmental field at the time of the outbreak differed depending on the season. Especially, in winter, it occurs in a field with a weaker-than-average jet stream and smaller trough curvature. It was also a field of enhanced vertical wind shear rather than deformational motion. In June, there is a strong moist convergence field to the south in the lower troposphere, and the north-south gradient of the equivalent potential temperature suggests the presence of the Baiu front. It is also suggested that the field is prone to intensify deformation motions associated with the Baiu front.
AS46-A012
Development of Model Output Statistics to Support Flight Operations Around the Airports in South Korea
Jeonghoe KIM+, Jung-Hoon KIM#
Seoul National University, Korea, South
Weather phenomena such as low-level wind shear, icing, low ceiling and visibility can be potential weather hazards for flight operations around the airports. To support safe flight operations against these aviation weather hazards, especially around the airports, weather forecast offices around the world produce terminal aerodrome forecasts (TAFs) in which meteorological information related to the weather hazards is included. One way to produce weather forecasts is to use model output statistics (MOS). In the MOS method, relationships between meteorological variables from observations and numerical weather prediction (NWP) model outputs are established from long-term data archives using statistical models. Currently, Korea Meteorological Administration (KMA) operates a MOS system that is based on multilinear regression applied to global NWP models. However, this MOS system suffers from limitations since (1) the weather forecasts produced by the MOS system is not directly focused on the airport locations with high resolution of regional model and (2) a relatively “simple” statistical model was used in the development. In this study, MOS systems were developed for weather forecasts around the airports in South Korea using Local Data Assimilation and Prediction System (LDAPS), which is a regional NWP model operated by KMA. First, a MOS system was developed using multilinear regression with forward feature selection as a baseline model. Then, the new MOS systems are developed further using both linear (e.g. LASSO regression) and nonlinear (e.g. random forest regression) statistical models. Performance skills of the developed MOS systems are compared by scoring metrics including mean absolute error (MAE) and bias against observations at the airports in South Korea. Acknowledgement: This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2022-00310.
AS46-A013
Evaluation of Aviation Convective Index for Deep Convective Area Using the Global Unified Model of the Korean Meteorological Administration
Yi June PARK+, Jung-Hoon KIM#
Seoul National University, Korea, South
This study developed a new index for predicting deep convective area, the Aviation Convective Index (ACI), using the operational global Unified Model of the Korea Meteorological Administration (KMA). ACI was developed by the fuzzy-logic algorithm in Korea, which was validated and optimized by using the 1-yr period of radar data. The yearly optimized ACI (ACIYrOpt) based on the optimized weight coefficients for 1-yr period shows a better skill than the original one with the uniform weights. But, in winter with the lowest number of the deep convective events, performance skill was deteriorated significantly, resulting in the decrease of seasonal averaged value of Area Under the ROC Curve (AUC) and True Skill Statistics (TSS) by 0.358 % and 6.143 %, respectively. To consider the seasonal variability in the background conditions conducive to deep convections, membership function (MF) and weight combination in the fuzzy-logic algorithms were optimized in each season. Finally, seasonally optimized ACI (ACISnOpt) showed a better skill with the significant improvements in AUC and TSS by 0.931 % and 25.62 %, respectively, compared with those from the . We also conducted several case studies for confirming the improvements. The representative cases were selected in each season with observed CIT events from the aircraft data. In all cases, the ACISnOpt predicted a better spatial distribution and intensity of the convection. Enhancements in the forecast fields from the ACIYrOpt to the ACISnOpt in the selected cases explained well the changes in overall performance skills of the probability of detection for both “yes” and “no” events during 1-yr period of the data. These results imply that the ACI forecast should be optimized seasonally to take into account the variabilities in the background conditions for deep convections in Korea. Acknowledgement: This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2022-00410.
AS46-A015
Statistical Analysis on the Estimations of Solid Hydrometeors Growth Zones and Their Weather Conditions Using Radar Spectrum Width
Sung-Ho SUH1#+, Woonseon JUNG2, Hong-il KIM1, Eun-Ho CHOI1, Jung-Hoon KIM3
1Korea Aerospace Research Institute, Korea, South, 2National Institute of Meteorological Sciences, Korea, South, 3Seoul National University, Korea, South
This is a follow-up study to analyze the correlation between hydrometeor type and the radar spectrum width (σv) according to atmospheric disturbances such as turbulence and wind shear. The statistical analysis was performed for eight precipitation cases under various conditions (precipitation type, season) focusing on Dendrite Growth Zone (DGZ) and Needle Growth Zone (NGZ), where Dendrite (DN) and Needle (NE) type snowflakes are dominant, respectively. The Growth Zone Determination Algorithm (GZDA) was proposed to determine them quantitatively. The σv zone was identified only in stratiform precipitation, and the intensity of the σv zone in DGZ has inverse-proportional to their altitude (i.e., winter). The strong σv-the differential radar reflectivity (ZDR) negative relationship in DGZ for all cases is consistent with the aerodynamic properties of DN. In addition, as the range of SW was larger than that of ZDR, it was confirmed that the dependence of σv according to atmospheric conditions is significant. On the other hand, NGZ had a weak σv-ZDR negative relationship with a narrow range of SW, which is consistent with the aerodynamic properties of NE. The lower cross-correlation coefficient (ρhv) in DGZ than that in NGZ implied that the irregularities (particle shape and aerodynamics features) of DN were more pronounced than those of NE. Furthermore, the possibility of sub-zero air temperature estimation based on weather radar from GZDA was confirmed.
AS46-A017
A Study of Sea Fog Event Over the Yellow Sea Using the High-resolution Modeling with Improved Initial Surface Conditions
Jae-Sik MIN#+, Jung-Hoon KIM
Seoul National University, Korea, South
The west coast of Korea is composed of many islands and tideland, and the coastline is changing due to reclamation projects that began in the 1960s. Incheon International Airport (ICN) on Yeongjong Island in the Yellow Sea is a representative artificial structure built through land reclamation. Due to land reclamation and the construction of artificial structures, the surface conditions change, and the ocean-atmosphere interaction changes, resulting in changes in meteorological phenomena. This study aims to analyze the influence of meteorological phenomena according to changes in surface conditions, focusing on ICN. In particular, on November 16, 2019, the case was analyzed using the WRF for low visibility, which is a representative weather hazard around airports. Through a control experiment (CTL) using geographical information (topography and land-use type) before the past reclamation and an improved experiment (EXP) using the latest geographical information, the effect on the NWP simulations was examined. For geographic information, a topography with a 5 m resolution (NGII, 2022) and a land-use type (ME, 2021) with a 5 m resolution were used as initial conditions for the WRF. On November 16, 2019, low visibility was a case in which a migratory high in autumn was located on the Korean Peninsula, and radiation fog generated inland at night affected ICN by a land breeze. The minimum visibility distance was 150 m. In EXP, the low visibility phenomenon was well simulated. However, using past geographical information in CTL, an advection of radiative fog appeared inland, whereas fog due to radiative cooling did not occur because ICN was composed of the ocean. This study confirms the change in radiation fog distribution due to land reclamation, and details will be mentioned in this presentation. Acknowledgment: This research is supported by the Korean Meteorological Administration Research and Development Program (KMI2022-00310).
BG01-A004
A Potential Solution in the Removal of Copper in Mine Wastewater
Kung Ming LEUNG1#+, Richard XU2, Grace LAI1, Simon GRIFFIN1
1The ISF Academy, Hong Kong SAR, 2Melbourne Grammar School, Australia
Mine tailings and wastewater are often toxic and acidic. Heavy metal ions in the tailings can easily dissolve into wastewater and run-off to contaminate both surface water and groundwater, resulting in serious toxicity to humans and ecosystems, representing a long-term environmental hazard. Waste containment and chemical remediation are expensive options, so that bioremediation may present a more viable alternative. Serratia is a bacterial genus with a wide geographical distribution, known to survive harsh conditions such as acidic environments and high concentrations of heavy metal ions. This project has investigated two copper-tolerant isolates of Serratia sp. to explore their potential application to heavy metal remediation.
Two isolates of Serratia sp., isolated from a disused tungsten mine (KML.E1) and from countryside soil (RX11.2), showed tolerance to high levels of Cu2+. Upon incubation in Luria broth containing up to 90 mM CuSO4 or copper(II) tartrate, red-brown precipitates were observed indicating reduction of copper(II) ions to the metal. Subsequently, the activites of the bacterial strains immobilised in the form of calcium alginate beads has been investigated, since this would allow the bacteria to be localised and protected from competing microbes; it also minimises the risk of biocontamination of the surroundings.
While this work helps to support the use of bioremediation for the removal of Cu2+ from wastewater, the reductive mechanism of Serratia sp. strains ML.E1 and RX11.2 might also be applied to the recovery of other metals with suitable electrode potentials such as Ag and Au.
BG01-A006
Mercury Methylation in Sediment Influenced by Permafrost Thawing in the East Siberian Sea and Beaufort Sea, Arctic Ocean
Hakwon JEONG1#+, Jihee KIM2, Sangwoo EOM1, Juhyeong CHAE1, Seunghee HAN1
1Gwangju Institute of Science and Technology, Korea, South, 2Korea Institute of Science and Technology, Korea, South
The extent of submarine permafrost on the Arctic shelves has been declining in recent decades due to climate change, however, the influence of submarine permafrost thawing on methylmercury (MeHg) production in sediment has been understudied. The total Hg (THg) and MeHg concentrations and sediment properties in the shelf and slope sites of the East Siberian Sea (ESS) were observed to identify the seasonal permafrost thawing effect on the methylation of Hg(II) in sediment overlying permafrost zone. Top (0–2 cm) sediment was collected from the 12 sites on the ESS Shelf and Slope on the icebreaker R/V Araon in August 2019. THg in sediment was higher in the slope than in shelf sites due to the hydrodynamic sorting of fine particles enriched with Mn/Fe oxides. In contrast, the highest MeHg/THg ratio in sediment was noted at 50–60 m isobaths of the shelf sites, identified as a continuous-discontinuous transition zone. The same sediment also showed greater fractions of photoreactive humic and organic sulfur than in the surrounding sites. This suggests that a copious supply of dissolved organic matter in the active layer of the between transition zone may promote the in situ methylation rate. To confirm this hypothesis in the Beaufort Sea, thirteen 50 cm sediment cores were collected in August to September 2022 on R/V Araon. Like ESS, THg in surface sediment tends to increase towards the slope. The highest MeHg/THg ratio in surface sediment was noted at 50-60 m isobaths, presumed to be a transition zone. This transition zone was confirmed by the observation of pingos, formed through processes of freezing and thawing of sediment porewater. We are currently analyzing methylation rate constant values in each sediment cores to identify if the MeHg production rate increases in the sediment overlying transition zone.
BG01-A007
Productivity-induced Redox Oscillation Control the Nitrogen Isotope Offsets Between Bulk Sediment and Foraminifera-bound Nitrogen in the South China Sea Over the Past 500ky
Li-Wei ZHENG1#+, Yao LAI2, Xiaodong DING3, Ehui TAN1, Xufeng ZHENG1, Zhixiong HUANG1, Zhenzhen ZHENG1, Shuh Ji KAO2
1Hainan University, China, 2Xiamen University, China, 3North Minzu University, China
In oligotrophic South China Sea (SCS), the isotopic compositions of planktonic foraminifera tests (δ15NFB) and bulk nitrogen (δ15NTN), which are both considered as recorders of nitrogen dynamic in the upper ocean of SCS, showing inconsistent temporal patterns (variable offsets (Δδ15NTN-FB) through time) with debatable causes. Since the δ15NFB was protected from degradation, the multi-sources contribution and diagenetic alteration of δ15NTN was thought to be responsible for the offsets, which need further verified. Here we determine the different speciation of nitrogen isotope of a sediment core MD972142 in Southeastern SCS and synthesizes the modern observations of sinking particles (PN%, δ15Nsinking) over the SCS basin from export to burial modern to explore the temporal variation of Δδ15NTN-FB. Results show that the Δδ15NTN-FB changed from -3 to 3‰ over the past 500ky, with negative values in glacial and positive in interglacial period, which was controlled by the productivity-induced bottom water redox oscillation, while both the contribution of terrigenous ON and clay-fixed inorganic nitrogen to δ15NTN was ignorable.
BG01-A008
Biogeochemical Paleoceanography of Ulleung Basin, East Sea for the Last 600 Kyr
Jeongwon KANG#, Sangmin HYUN, Jin Hyung CHO, Yunji KIM+
Korea Institute of Ocean Science & Technology, Korea, South
GPC-2B sediment core, collected in Ulleung Basin, was analyzed to reconstruct the variation of paleoceanographic conditions of southern East Sea. Two tephra layers, Aso-4 (88 kyr) and Aso-3 (133 kyr), were observed and alkenone concentrations and lightness (L*) indicated that GPC- 2B covered 600 kyr (MIS 16). Similar to other sediment cores collected in East Sea, foliation and bioturbation were observed in GPC-2B suggesting GPC-2B would have well recorded surface primary production and paleoceanographic conditions. This study aims to reconstruct the history of terrigenous organic matter input and qualitative paleoclimate changes based on biogeochemical properties. The range of TOC content and δ13C were 1 ~ 4% and -21 ~ -25‰, respectively. Based on stable isotope and alkenone-derived SST of GPC-2B suggested that the sediment core reflected the orbital-scale variation for the last 600 kyr. N-alkane also showed orbital-scale alterations; N-alkane content generally increased during glacial stages and decreased during interglacial stages. It suggested that East Asian paleoclimate changes were in association with glacial-interglacial cycle. In addition to biogeochemistry, inorganic geochemical characteristics would be investigated to obtain more reliable paleoclimate and paleoceanographic reconstructions such as relative sea surface temperature and strength of influx East China Coastal Water.
BG02-A001
Applications of Geochronology in Mesozoic Evolutionary Events
Su-Chin CHANG1#+, Daran ZHENG2, Yangyang XIA1, Jun WANG3, Rui PEI2, Yuling LI1
1The University of Hong Kong, Hong Kong SAR, 2Chinese Academy of Sciences, China, 3Yunnan University, China
Geochronology is a foundational approach to understanding Earth’s history. Significant developments in the past 30 years in both U–Pb and 40Ar/39Ar datings, two of the most widely used geochronological methods, allow for unprecedented levels of precision and re-interpretation of geological, climatic, and biological events. Since 2011, our research team based at the University of Hong Kong has applied U–Pb and 40Ar/39Ar radio-isotopic dating techniques to refine the dates and durations of several key Mesozoic evolutionary events. Our age data, for example, provide robust ages to calibrate the terrestrial and marine recoveries after the Permo-Triassic mass extinction event, the origin and diversification of flowering plants, the radiation and migration of the famous Jehol Biota, and the fossil-rich amber discovered from China and Myanmar. In this study, we summarize our contributions which have improved our understanding of the Mesozoic world. We also review the limitations of applying geochronology to evolutionary events and discuss the solutions to these issues.
BG06-A001
Will Nature Do its Trick to Limit Warming Below 1.5°C?
Zhangcai QIN#+
Sun Yat-sen University, China
Significant reduction of greenhouse gas (GHG) emissions is urgently required in order to limit global temperature rise with a reasonable possibility. Under current and even more ambitious climate policies, emissions mitigation from energy and industrial sectors alone do not seem to be able to achieve the Paris climate target of 1.5 °C. The natural climate solutions, by reducing emissions and/or increasing carbon sinks in natural ecosystems, could provide additional efforts to mitigate GHG emissions. However, the role of nature has always been underappreciated in mitigating climate change, will nature do its trick to significantly limit warming? This talk hopes to present recent updates on this topic and discuss the role of nature in climate change from a broader perspective.
BG06-A003
Sensitivity of Land Surface Processes to Surface and Boundary Forcing: A Regional Application of Community Land Model Version 5 for Pearl River Basin
Deng JINLING#+, Liuqian YU
The Hong Kong University of Science and Technology (Guangzhou), China
Knowledge of land surface processes is essential to understanding and predicting the response of terrestrial ecosystems to human activities and climate change. A valuable tool to obtain the required knowledge is land surface models (LSM) that simulate a wide range of Earth’s surface processes, such as exchange fluxes of energy and water and cycling of carbon and nutrients. However, land surface simulations can have significant uncertainties and errors stemming from the imperfect representation of processes, inaccurate forcing, and uncertain initial and boundary conditions, among others. Sensitivity analysis of land surface models is thus an indispensable step for interpreting and improving model results to advance our knowledge of land surface processes. In this study, we implement the Community Land Model version 5.0 (CLM5.0) to Pearl River Basin, an expansive watershed in Southern China with complex heterogeneous landscapes. We assess how the simulated land surface processes respond to three variants of the model grid with high (0.01° × 0.01°), medium (0.05° × 0.05°) and coarse (0.1° × 0.1°) horizontal resolution, and to a suit of atmospheric forcing datasets with various spatial-temporal resolutions. Model simulations for 2010-2015 are validated against remote sensing products and tower-based flux measurements to identify the model configuration that best reproduces observations. Through these analyses, we gain insight into the key factors affecting the performance of land model simulations and improve our understanding of surface energy fluxes, and hydrological and biogeochemical processes in the Pearl River Basin.
BG06-A004
Forest Carbon Sequestration Potential in China Under Different SSP-RCP Scenarios
Yidan HAO#+, Jieming CHOU
Beijing Normal University, China
Forests are major components of terrestrial ecosystems, the estimation of forest carbon sequestration and its economic value as a carbon sink is an important element of global carbon cycle research. In this study, based on the prediction of forestland changes under the future shared socioeconomic pathways SSP1-RCP2.6, SSP2-RCP4.5, and SSP5-RCP8.5, the growth equations of different tree species were fitted using forest inventory data, and the biomass conversion factor continuum function method was used to estimate forest vegetation carbon fixation at the national-scale. The carbon sink potential of the forest ecosystems in 2020-2100 was estimated under the three scenarios, and the carbon fixation potential of forest ecosystems in China and its spatial pattern were discussed.
BG06-A005
Quantifying the Climate and Carbon Cycle Response to Negative CO2 Emissions Over Multi-centennial Timescales
K. U. JAYAKRISHNAN#+, G. BALA
Indian Institute of Science, India
Anthropogenic emissions of carbon dioxide during the industrial period (1750-present) has led to an increase in global mean surface temperature by approximately 1°C. Previous studies show that the increase in frequency of natural disasters such as extreme rainfall, floods and heatwaves is attributed to human induced climate change. The Paris agreement targets to keep global mean warming below 2°C above the preindustrial state, while pursuing efforts to limit the increase to 1.5°C. To achieve the targets set by the Paris agreement, artificially removing large amounts of atmospheric carbon dioxide might be necessary in the 2nd half of this century. Therefore, understanding the response of climate system towards negative atmospheric CO2 emissions is important. In this study, using a coupled climate and carbon cycle model, we simulate the response of the climate system to net negative emissions in 9 idealized simulations. Each simulation has a positive emission phase followed by a negative emission phase such that the cumulative emission since the preindustrial period is zero in each simulation. Three sets of simulations are performed with cumulative emissions of 1000PgC, 2000PgC and 5000PgC in the positive phase. For each value of cumulative emission during the positive phase, three different simulations are performed by varying the total duration (300, 500 and 1000 years) over which the positive and negative emissions occur. The above idealized simulations are designed to address the following two questions: 1) For the same total emissions in the positive phase, does the timescale of emissions have any impact on the long-term response of the climate system? 2) If the timescale of emissions is the same, what is the sensitivity to the magnitude of total emissions in the positive phase? The results from our nine climate-carbon model simulations will be discussed at the meeting.
BG06-A006
Towards Improved Accuracy and Efficiency of Ecohydrologic Processes Using Artificial Intelligence
Elias MASSOUD1#+, Forrest HOFFMAN1,2, Nathan COLLIER1
1Oak Ridge National Laboratory, United States, 2University of Tennessee, Knoxville, United States
Ecohydrology research sits at the intersection of ecosystem ecology and water cycle science, and it incorporates land surface processes and atmospheric and watershed science in addressing ecophysiological responses and feedbacks to the hydrologic cycle. Understanding interactions among important ecohydrologic mechanisms is challenging, and constraining models of ecohydrology is limited by mechanistic knowledge gaps and by observations that are available at only a few of the scales of interest. Artificial intelligence (AI) and machine learning (ML) approaches are likely to provide new avenues for extracting mechanistic understanding from the diversity of data available at different scales. In this work, we aim to apply AI/ML methods to improve computational accuracy and efficiency in estimations of vegetation processes relevant to ecohydrology by utilizing datasets that are rich with observational as well as model simulated information. Beyond improved skill and reduced computational cost, this work explores potential mechanistic process understanding that can be achieved by combining AI/ML methods with available libraries of data.
BG06-A009
Evaluating Land Carbon Cycle Processes in Earth System Models: Have Models Improved Over Time?
Forrest HOFFMAN1,2#+, Mingquan MU3, Min XU1, Gretchen KEPPEL-ALEKS4, Dave LAWRENCE5, Charles KOVEN6, Weiwei FU7, Bill RILEY6, James RANDERSON7
1Oak Ridge National Laboratory, United States, 2University of Tennessee, Knoxville, United States, 3University of California Irvine, United States, 4University of Michigan, United States, 5National Center for Atmospheric Research, United States, 6Lawrence Berkeley National Laboratory, United States, 7University of California, Irvine, United States
Better representations of biogeochemistry–climate feedbacks and ecosystem processes in Earth system models (ESMs) are essential for reducing uncertainties associated with projections of climate change during the remainder of the 21st century and beyond. Model–data intercomparison and integration activities are required to inform improvement of land carbon cycle models and the design of new measurement campaigns aimed at reducing uncertainties associated with key land surface processes. The International Land Model Benchmarking (ILAMB) Package was designed to facilitate systematic and comprehensive model–data intercomparison and improve understanding of factors influencing model fidelity. We used ILAMB to benchmark and intercompare terrestrial carbon cycle models coupled within ESMs used to conduct historical simulations for the Fifth and Sixth Phases of the Coupled Model Intercomparison Project (CMIP5 and CMIP6). Results indicate that the suite of CMIP6 land models exhibits better performance than the suite of CMIP5 land models in comparison with observations for a variety of biogeochemical, hydrological, and energy-related variables. To test the hypothesis that the multi-model range of climate–carbon cycle feedback strengths from more realistic models would diverge less over time, we calculated and compared the ranges of concentration–carbon and climate–carbon sensitivity parameters and the trajectories of land carbon uptake from CMIP5 and CMIP6 models. Since the multi-model means of both the CMIP5 and CMIP6 land models performed better across most variables than any single model that contributed to the means, we also calculated the CMIP5 and CMIP6 multi-model mean feedback sensitivities and uptake trajectories. In an attempt to further reduce uncertainties in carbon cycle projections, we used the ILAMB benchmark performance scores to weight model contributions to the CMIP5 and CMIP6 multi-model means for land carbon uptake and related variables and compared them with observationally constrained estimates for the historical period.
BG06-A010
Autumn Cooling Paused Increased CO2 Release in Central Eurasia
Masayuki KONDO#+
Hiroshima University, Japan
Recent autumn warming in northern latitudes has facilitated an increase in terrestrial ecosystem respiration (TER) more than that in gross primary productivity (GPP), leading to a net loss of CO2 from the land to the atmosphere in autumn. Conversely, autumn cooling is expected to induce a greater decrease in TER than in GPP, thus leading to a net increase in autumn CO2 uptake. However, a recent study reported an increase in net CO2 release in northern autumn cooling from 2004 to 20183, indicating that both the autumn warming and cooling result in net CO2 release. Here, we show that the conclusion regarding net CO2 release under autumn cooling was flawed owing to the inappropriate choice of the autumn period, which resulted in overlooking regions such as central Eurasia, where the 2004–2018 autumn cooling most affected CO2 fluxes. Empirical upscaling of eddy flux observations (FLUXCOM) and atmospheric CO2 measurements from seven towers suggested that the increased net CO2 release paused during the 2004–2018 autumn cooling in central Eurasia. The results reported by the recent study are likely biased toward CO2 release as their assessment involves regions including North America where the 2004–2018 autumn cooling had little effect (rather, the autumn warming effect was more profound) on CO2 fluxes.
BG06-A011
Global C4 Distribution Estimate Constrained by Observations and Optimality Theory
Xiangzhong LUO#+
National University of Singapore, Singapore
Photosynthesis of C4 plants responds to climate change differently than the more common C3 plants, due to their unique anatomic and biochemical characteristics. The different response is expected to cause a change in global C4 distribution, however, current C4 distribution models are inadequate to predict that as they are based on a temperature-only hypothesis and lack observational constraints. Here, we used a global database of photosynthetic pathways, satellite observations and a photosynthetic optimality theory to produce a new observation-constrained estimate of C4 distribution. We found that global C4 coverage stabilized at 11.2% of the vegetated land surface during 1992 to 2016, as a net effect of C4 grass decrease due to elevated CO2 and C4 crop increase, mainly from maize expansion. Using an emergent constraint approach, we estimated that C4 contributed 12.5% of global photosynthetic carbon assimilation, a value much lower than previous estimates (~20%) but more in line with the mean of an ensemble of dynamic global vegetation models (14 ± 13%). By improving the understanding of recent global C4 dynamics, our study sheds insight on the critical and previously underappreciated role of C4 plants in modulating the global carbon cycle in recent history.
BG06-A013
Peatland Loss in Southeast Asia Contributing to U.S. Biofuel’s Greenhouse Gas Emissions
Yakun ZHU+, Zhangcai QIN#
Sun Yat-sen University, China
Land use change (LUC) induced by biofuel production could lead to greenhouse gas (GHG) emissions, which potentially increase biofuel’s carbon intensity. Among the sources of LUC-related emissions for soy biodiesel, the contribution from peatland loss to agricultural plantations in Southeast Asia remains uncertain. Here, we analyzed LUC in Malaysia and Indonesia and modeled its impacts on the GHG emissions of soy biodiesel produced in the United States. It shows that oil palm plantations have more than doubled over 2001-2016 and the area of palm-on-peatlands (PoP) has expanded 3.7 times. Over new palm plantations, the share of PoP is about 19% regardless of time and location and the emission factor (EF) for peatland-to-palm conversion is estimated to be 41.5 Mg CO2 ha-1 yr-1. With these updates on PoP and EF, the contribution of peatland loss (0.7-5.1 g CO2e MJ-1) to biodiesel emissions is only 40- 65% of previous estimates, which reduces discrepancies among model simulations used by different agencies. Based on emerging evidence on LUC and related carbon changes, our analysis reexamines regional peatland loss and its impacts on LUC emissions modeling and provides new insights into the estimation of LUC impacts on biofuels’ carbon intensity.
BG07-A001
Trophic Base and Basal Resources of Northeast Asian Stream Food Webs Pre- and Post-monsoon
Hee Yoon KANG#+
Chonnam National University, Korea, South
Identifying variability in the trophic base and the role of aquatic and terrestrial sources for food webs is a challenge in understanding the dynamics and stability of aquatic ecosystems. Although a large amount of terrestrial detritus transported into the stream continuum during the East Asian summer monsoon would be expected to change the food web base from the pre- to post-monsoon period, further geographically and regionally specific case studies are needed due to the systematic differences in trophic pathways of organic matter supporting aquatic food webs. Here, we examined the δ13C and δ15N values of consumers (invertebrates and fish) across the upstream channel and lacustrine habitats during the pre- and post-monsoon periods in the stream system of Korea compared with those of their potential sources of organic matter. The isotope signatures of potential organic matter sources differentiated allochthonous sources (leaf litter and riparian vegetation) from autochthonous sources (algal biofilm and phytoplankton). The resultant trophic niche indicated a spatiotemporal consistency of the trophic structure at the community level. In addition, the isotope mixing model estimates revealed the trophic attribute of instream production as the primary source of organic matter. These results highlight a consistent dominance of autochthonous trophic bases in aquatic food webs pre- to post-monsoon. Our findings may provide insights into food web dynamics and processes in association with the availability of nutrient sources across the potential links between terrestrial and aquatic ecosystems in the East Asian monsoon climate zone.
BG07-A002
Assessing Carbon Sequestration Capacity of Shellfish Aquaculture Using a Coupled Bioenergetic and Biogeochemical Model
Ye LIU1#+, Liuqian YU2
1The Hong Kong University of Science and Technology, China, 2The Hong Kong University of Science and Technology (Guangzhou), China
Shellfish aquaculture has been rapidly expanding worldwide to meet the accelerating global seafood demand. Recent years have also witnessed a growing interest in including the cultivated shellfish in carbon trading systems. However, significant uncertainty remains in assessing shellfish's carbon sequestration capacity primarily because of the complex interaction between the shellfish and carbon and nutrient cycling in the aquatic environment as well as the atmosphere-water and sediment-water interfaces. Shellfish growth associated with shell formation can directly affect carbon flow through respiration, shell calcium carbonate production, and carbon dioxide (CO2) release from biogenic calcification. Shellfish can also indirectly regulate the ecosystem’s carbon sink capacity by exerting top-down control over carbon-sequestering phytoplankton populations through filter feeding and by accelerating the carbon sedimentation rate via bio-deposition. Therefore, a rigorous assessment of shellfish aquaculture’s carbon sink potential requires thoroughly accounting for the direct and feedback effects of shellfish on the carbon cycle. To conduct such assessment, we propose to build a coupled bioenergetic and biogeochemical modeling framework that can explicitly track the CO2 fluxes from respiration and shell calcification, the carbon flow through the planktonic food webs, and the deposition, remineralization and burial of particulate organic carbon at the aquatic-benthic interface. We will present initial results from the coupled model configured for a eutrophic bay with sizeable oyster farms. The potential of applying the modelling framework to assess shellfish aquaculture’s carbon sequestration capacity over a larger ecosystem scale will also be discussed.
BG07-A004
The Activity and Composition of Methanogens in Constructed Wetland Soils by DNA Stable Isotope Probing
Wen Ting HUANG+, Yo-Jin SHIAU#
National Taiwan University, Taiwan
Constructed wetlands provide various ecosystem services and are important in regulating the global C and N cycles, but they are also important sources for methane (CH4) emissions. Because CH4 is estimated to have a global warming potential of 27-30 over 100 years, it is important to know how the emissions are regulated by soil physiochemical properties in wetland ecosystems. Thus, in this study, we tried to determine the compositions of active methanogens in three constructed wetlands with different ages in Taiwan using a DNA-based stable isotope (DNA-SIP) technology. By incubated the field collected soil samples with 13C-methanol and sequenced the mcrA genes in the heavy layers of the isopycnic density gradient centrifugation, we were able to determine the changes of active methanogens after wetlands were constructed. The results showed the potential CH4 fluxes were respectively 0.02-0.40, 0-0.10 and 0.04-0.17 μg CH4 g-1 soil hr-1 with incubated with methanol, glucose and CO2. In addition, mcrA genes were between 3.12-6.24×108 copies and 0.81-8.88×108 copies in the fresh and incubated wetlands soils, respectively. Furthermore, the dominant methanogens were Methanosarcinales, Methanomicrobiales and Methanomassiliicoccales in the constructed wetlands across different ages. This observation showed that compositions of methanogens were temporal varied in the constructed wetlands. Future study may need to further determine the environmental factors that may decrease the activities of methanotrophs under different wetlands’ ages to maximize the C sequestration potential that wetlands may provide.
BG07-A005
DNA Stable Isotope Probing Reveals Temporal and Spatial Variations of Active Methanotrophs in Subtropical Constructed Wetlands in Taiwan
Ting-Kai CHEN+, Yo-Jin SHIAU#
National Taiwan University, Taiwan
Constructed wetlands, as ecological engineering technologies, are similar in function to natural wetlands in sequestrating carbon and are recognized as nature-based solutions (NBS) in reducing the global greenhouse gas concentrations. However, the anaerobic soil conditions that wetlands provide also make them considerable sources for methane (CH4) emissions. Fortunately, approximately 50 to 90 percent of the CH4 produced from deep wetland soils can be oxidized into carbon dioxide (CO2) by methanotrophs in the aerobic soil layer and mitigate the overall methane emissions from wetlands. Previous studies on methanotrophs have mainly focused on rice paddy and natural wetlands, with limited data on constructed wetlands, particularly in tropical and subtropical areas. This study analyzed the changes of active methanotrophs in three constructed wetlands with different ages and seasons in Taiwan. With using DNA stable isotope probing (DNA-SIP) and next-generation sequencing (NGS) techniques, we revealed the temporal and spatial variations of active methanotrophic compositions in the constructed wetlands. The results of 16S rRNA and pmoA genes in the field soil showed that the highest relative abundance of type II Methylocystis in the wetlands with the lowest sulfate (SO42-) concentration (8.10 ± 1.44 ppm). While the type I methanotrophs were mostly found in the wetlands with high SO42- concentrations. Furthermore, the DNA-SIP experiments revealed active type I methanotrophs were dominated all the studied constructed wetlands. In young wetlands during winter, the increased abundance of type Ib methanotrophs may have a positive impact on methane oxidation. These results demonstrate the ecological niche differentiation of methanotrophs in constructed wetlands under different conditions and the active community structure changes in response to methane concentration. Future management in constructed wetlands will be needed to enhance their carbon sequestration value.
BG07-A012
Seasonal Dynamicity of Environmental Variables, Water Quality Index and Unusual Abundance of Bloom-forming Aulacoseira Spp. Diatom Populations in the Lower Stretch of the River Ganga
Chakresh KUMAR#+, Anwesha GHOSH, Punyasloke BHADURY
Indian Institute of Science Education and Research Kolkata, India
Untreated sewage and other pollutants are being released on a daily basis into major rivers globally including the Ganga in India. Increasing human pressure and resulting anthropogenic pollutants pose numerous challenges to health of Ganga, in particular at the lower stretch which culminates into Bay of Bengal which also receives significant freshwater influx during monsoon season. In this study, the effect of monsoonal precipitation on environmental variables and the Water Quality Index (WQI) was studied at nine sites represented by 59 stations along the lower stretch of Ganga during 2019. Both pH and DO were strongly influenced by monsoon and affected WQI. Seasonal variations in dissolved nutrients, such as nitrate and o-phosphate concentrations were influenced by monsoonal precipitation. Higher concentrations of dissolved nutrients at point-source stations in the study area reflected the effect of direct discharge of untreated urban and industrial sewage on the river. During monsoon, the effects of precipitation and accompanying environmental factors were clearly visible on a key biological variable (concentration of Chl-a), with measured values in PS stations being lower than the SW stations. The WQI values determined for lower stretch of the Ganga revealed very poor water quality in majority of the stations and monsoonal precipitation did not show any influence on the observed trends. Besides, there was evidence of an algal bloom-like scenario, dominated by the centric diatom Aulacoseira spp. in one of the studied sites of the lower stretch of Ganga. This event highlighted the deteriorating water quality with implications for key ecosystem processes such as carbon cycling and the River Ganga's overall health.
BG07-A014
Removal of Arsenic from Groundwater by Natural Polymer-based Hydrogel in the Bengal Delta Plains- Linking Arsenic Biogeochemical Cycling with Carbon Cycling
Meghna BISWAS1#+, Punyasloke BHADURY2
1Vellore Institute of Technology, India, 2Indian Institute of Science Education and Research Kolkata, India
In the Bengal Delta Plains (BDP) encompassing parts of India along with Bangladesh, arsenic in groundwater, agricultural lands and in staple food such as rice, pose serious health challenges to millions of people on a daily basis. The prevailing biogeochemistry of arsenic cycling is influenced by nature and forms of organic carbon present in the BDP. Surface modified iron doped cellulose, a type of polymeric scaffold of biological origin, has been prepared in the laboratory and the efficacy of this polymeric scaffold for removal of forms of As has been evaluated using groundwater and agricultural soils collected from BDP. Based on ICP-MS analysis, the synthesized hydrogel showed ability to remove up to 11 ppb As from groundwater of BDP which exhibited initial concentration of almost 13 ppb As. Besides, the germination efficiency of a cultivar of rice grown in BDP was evaluated by spiking 10-100 mg/kg of As (arsenate salt) and 0.025 g polymeric scaffold. Under all the As spiked conditions, there was germination of the rice cultivar and the physiological mechanisms of this polymeric scaffold in stopping entry of As is being evaluated. As part of ongoing experiment, two cultivars of paddy grown under laboratory conditions but spiked with 100 ppb As and polymeric scaffold (1-2.5 g per 6 kg of soil) seems to be growing and did not exhibit observable physiological abnormalities. The ongoing study with spiked As along with different forms and concentrations of organic carbon in groundwater as well as agricultural soil are being evaluated to assess the efficacy ranges of the synthesized polymeric scaffold of biological origin. The study can form the basis for developing cost-effective and sustainable polymeric scaffold which can render As free groundwater and staple food.
BG07-A016
Harmonizing Satellite and Species Modeling to Explore Mangrove Suitable Area in Timor-Leste
Hyeon-Kwon AHN1#+, Chul-Hee LIM1, Wonhee CHO1, Byungwoo CHANG1, Sue Kyoung LEE2, Ohjung KWON2
1Kookmin University, Korea, South, 2SK Forest, Korea, South
Recently, various measures have been implemented to achieve carbon neutrality, among them, nature-based solutions such as planting tree species are emerging. Mangroves, representative high carbon absorption species, play an important role in minimizing negative impact while mitigating climate change, sea level rising, salt water intrusion, and tidal surges. This study aims to predict the habitat suitable area of mangroves in East Timor (Timor-Leste) based on machine learning ensemble approach. Mangrove presence data were extracted from the Sentinel-2 satellite data using deep learning based classification. The climate information used downscaled data for long-term averages globally. Habitat suitability was evaluated by ensemble the results of machine learning-based species distribution models. Currently, the area of mangrove habitat is about 0.19% of East Timor, and the area with significant mangrove habitat suitability is about 1.7% of East Timor, accounting for more area than the existing area. In addition, only areas with high habitat suitability for mangroves were extracted from shrubland, grassland, and agricultural land to extract areas suitable for additional mangroves. Areas with high habitat suitability for mangroves in shrubland, grassland, and agricultural land were evaluated to be capable of afforestation by 2,732.9ha in Pante Macassar and 1,452.1ha in Uato-Lari. Our results predict that carbon absorption and storage through additional mangrove afforestation can be expected.
BG07-A019
Microcosm Study to Simulate Effects of Ocean Acidification and Fertilizer Runoff on the Methylmercury Uptake by Marine Copepods
JuHyeong CHAE#+, Seunghee HAN
Gwangju Institute of Science and Technology, Korea, South
Ocean is the largest environmental medium absorbs CO2 released into the atmosphere. The CO2 dissolution causes ocean acidification, resulting in significant impacts on ecosystems. Before the Industrial Revolution, the CO2 concentration in the atmosphere was 280 ppm; this has increased to 420 ppm as of 2022. If the current trend continues, the concentration is likely to become 1,000 ppm by 2100, which corresponds to seawater pH of 7.6. A large proportion of agricultural land is bordered by Yellow Sea, and, freshwater with high nutrients is discharged into the sea, particularly during the monsoon. To determine the combined effect of seawater acidification and fertilizer runoff on the MeHg accumulation in copepods, we constructed microcosm with varying pCO2. The seawater was collected from the Yellow Sea and filtered through 150 um membrane to remove large particles and to contain the natural communities of bacteria, protozoa, and phytoplankton. Copepods were purchased and added to the microcosm along with 5 pM MeHg, to observe: 1) how the microbial food web structures, and the MeHg accumulation in copepods respond to the lower pH of seawater than current pH induced by CO2 dissolution; and 2) the effect of an increase in inorganic nutrients on the food-web structure, and the MeHg accumulation in copepods under the lower pH than current pH. We expect to detect less MeHg accumulation in the copepods due to the dominance of the conventional over the microbial food web under the high-CO2 and high-nutrition conditions. there is a possibility a higher accumulation of MeHg occurs in the copepods under the high-CO2 and high-nutrient condition, caused by copious release of dissolved organic matter from primary producers followed by additional Hg(II) methylation in the seawater. The microcosm simulation for understanding, is currently being carried out to verify whether the hypothesis stated above is valid.
BG07-A021
Spatiotemporal Variations of Organic Carbon and Sterols as Indicators of Primary Production and Ocean Sewage Dumping in the Sediments in the Southwestern Part of the East Sea (Japan Sea)
Minkyoung KIM1+, Jeomshik HWANG2#, Daniel B. MONTLUÇON3, Negar HAGHIPOUR3, Dongyoung KIM4, Chang-Keun KANG4, Young-Il KIM5, Timothy I. EGLINTON3
1Kyungpook National University, Korea, South, 2Seoul National University, Korea, South, 3Swiss Federal Institute of Technology Zürich, Switzerland, 4Gwangju Institute of Science and Technology, Korea, South, 5Korea Institute of Ocean Science & Technology, Korea, South
We examined sedimentary records in the UB (Ulleung Basin), located in the southwestern part of the East Sea and nearby shelf sites to investigate spatiotemporal variations in the depositional environment with a special focus on the various sterols. Sedimentary Organic carbon (SOC) accumulation rate and abundances of planktonic sterols (brassicasterol, cholesterol, and dinosterol) were obtained from 25-cm depth sediment samples. Spatiotemporal variation of coprostanol, a tracer of ocean waste dumping, was also examined to understand the dispersal and preservation of organic matter in this region. This study aims to provide new insights on SOC accumulation in the context of the biological carbon pump and behavior of the sewage in the water and sediments.
BG09-A001
Hand Sanitizers, Disinfectant Washes and Bacterial Cross-resistance to Antibiotics in Environmental Water Sources
S. Q. ZHANG+, Kung Ming LEUNG, Grace LAI, Simon GRIFFIN#
The ISF Academy, Hong Kong SAR
While the WHO has identified increasing antimicrobial resistance (AMR) as a global concern, this is a ‘slow emergency’ and a problem easily neglected in favour of more acute events [1]. In the meantime, of course, levels of AMR may even be unwittingly exacerbated: during the recent COVID epidemic, for example, the liberal use of sanitizers and disinfectants intended to neutralise the SARS-CoV-2 virus is likely to have encouraged bacterial cross-resistance to antibiotics [2], with resistant strains especially prevalent in sewage, grey water, and wastewater recycling facilities.
In order to track the possible effects of biocides on the levels and spread of AMR, this work comprises two stages. First, the isolation of antibiotic-resistant bacteria from beneath fingernails of a large cohort of subjects has been correlated with individual use of antibacterial agents and, at the same time, DNA extraction and sequencing of these bacterial isolates has allowed the identification of common AMR genes. Second, after the design of relevant primers, PCR testing is used to screen water samples recovered from a variety of sources and locations to understand their distribution and frequency of these AMR genes in the environment. In isolates recovered so far, the dominant resistance to ampicillin and augmentin points to an extended spectrum beta-lactamase, often accompanied by co-resistance to tetracycline. In some isolates, the relevant AMR genes co-occur with qac-family genes for quaternary ammonium salt resistance and plasmid- and transposase-mediated gene transfer allows their rapid dissemination. References
[1] D. Dominey-Howes, Geosci. Lett., 5: 7 (2018) [2] K. R. Harrison, A. D. Kappell, P. J. McNamara, Environ. Pollut., 257: 113472 (2020).
BG09-A002
An Investigation Into the Effects of Glyphosate on the Soil Microbiome
Rosalyn TANG+, Anya N. K. CHAN, Kung Ming LEUNG, Grace LAI, Simon GRIFFIN#
The ISF Academy, Hong Kong SAR
N-(phosphonomethyl)glycerine (glyphosate) is a popular broad-spectrum herbicide that is especially relevant in the Asia-Pacific region, its largest market. Despite concerns over possible human toxicity and its environmental impact, the global market for glyphosate in 2020 was estimated at US$7.6 billion and projected to grow to US$9.3 billion by 2027. Residue levels exceeding 0.5 mg.kg–1 have been reported in soils, large streams and groundwater in both Europe and the USA, and soil conditions and crop mix suggest that USA, Brazil and China are likely to see the highest exposure rates to glyphosate and its persistent breakdown product aminomethyl-phosphonic acid (AMPA) [1].
While human health and the emergence of resistant weeds are often identified as potential problems with glyphosate, as a potent inhibitor of the shikimate pathway for the biosynthesis of aromatic amino acids, the undoubted effects of the compound on the soil microbiome are poorly understood. Given that soil bacteria and fungi perform are key to the cycling of carbon and other nutrients and for sustaining plant growth, this lack of knowledge would seem to represent a major oversight.
This project investigates the effects of glyphosate on the soil microbiome in two ways. First, using soil samples recovered from a 1.5 x 1.5 m test square before and after treatment (on days 0, 3, 7, 14, 28 and monthly thereafter), 16S and ITS1 microbiome profiling of glyphosate-treated soil examines the immediate effects of glyphosate and estimates a recovery time under local conditions. Second, given some controversy about possible antimicrobial co-resistance, glyphosate-resistant bacteria have been identified in a number of soil extracts in order to gain an insight into characteristics that treatment is likely to favour. References: [1] F. Maggi, D. la Cecilia, F. H. M. Tang, A. McBratney, Sci. Total Environ., 717: 137167 (2020).
BG09-A003
Exploring Coffee Suitable Land Based on Socio-environmental Geo-criteria in Timor-Leste
Wonhee CHO1#, Byungwoo CHANG1+, Chul-Hee LIM1, Sue Kyoung LEE2, Ohjung KWON2, Hyeon-Kwon AHN1
1Kookmin University, Korea, South, 2SK Forest, Korea, South
The coffee industry is the largest non-oil export in Timor-Leste. Coffee was introduced by the Portuguese in the 1800s, and it became a major source of income for local communities. The Eremera, Ainaro, Aileu, and Liquica are known as the major municipality for the coffee industry in Timor-Leste. However, the coffee industry is vulnerable to global price fluctuations, lack of capital, and deficient infrastructure. Therefore, this study assesses the land suitability for coffee production, especially Coffea arabica L., in order to estimate the potential area for coffee plantations to support their sustainable industry. For this purpose, a suitability modeler in ArcGIS pro (version 3.0) was used for potential area estimation. Our model integrated 18 spatial inputs categorized as climatological (6), Edaphological (5), Physiographic (3), and Socio-economic (4). Our results confirm that Tatamailau mountainous area in Ermera and Ainaro, and Alieu are suitable for coffee plantations. Also, the results represent the mountainous area in Manatuto and Bobonaro, and the eastern part of Baucau is suitable for coffee plantations. This study can support local communities and governments in Timor-Leste to implement new strategies for coffee plantations and management to increase coffee production and their income. In addition, it can support the development of the local industry models, and afforestation (or reforestation) of the land by the coffee and shade tree can contribute to carbon absorption ability in Timor-Leste.
BG09-A008
Development of the Peptide-detecting Method for On-site Analysis
Miyamoto AI#+, Hajime MITA
Fukuoka Institute of Technology, Japan
One of the mysterious subjects is the origin of life. In 1969, approximately 100 amino acids were found in a meteorite that fell to Murchison, Australia, and glycylglycine was the only peptide found in the meteorite. It is essential to investigate whether peptides are synthesized in space to clarify life’s birthplace. In the Tanpopo, amino acids were exposed to the space environment on the International Space Station (ISS), and dipeptides were synthesized in space under vacuum ultraviolet light. The new space station, Gateway, is starting to construct in lunar orbit. Cosmic radiation at Gateway is stronger than those at ISS by shielding of the Van Allen belts. Therefore, the exposure experiments of peptide syntheses at Gateway are essential for studying peptide synthesis in deep space. It is necessary to analyze samples on-site since there is little opportunity to bring them back to Earth at the Gateway. Therefore, we will develop a simple method to analyze amino acid decrease, and dipeptide formation in space orbit on a cubic sat scale. Amino acid monomers and dipeptides were analyzed by FT-IR spectroscopy and biuret color reactions. FT-IR is acceptable, but a high-resolution one is required. In the biuret reaction, alanine (Ala) did not color, but alanylalanine (Ala-Ala) slightly colored blue. In general, the biuret reaction is a detection method for polypeptides that are longer than tripeptides, and the reaction causes a reddish-purple to bluish-purple color. Since amino acids and dipeptides have been used, this reaction should not normally occur. However, in this experiment, the dipeptides did not turn reddish purple to bluish purple but changed to blue that they could be distinguished from amino acids. In addition, a blue shift was observed depending on the ratio of Ala-Ala to Ala. The details of the biuret reaction are then studied.
BG09-A009
Nucleic Acid Adsorption on Proteinoid Microspheres
Sayaka TAKAHASHI#+, Hajime MITA
Fukuoka Institute of Technology, Japan
As one of the hypotheses for the origin of life, Oparin proposed chemical evolution. Fox and Harada et al. heated monoammonium malate to produce a polyamino acid called proteinoid. They also found that micron-sized spherical particles called microspheres were formed by dissolving proteinoids in hot water. This corresponds to the third stage of the chemical evolution theory, that specific structures such as coacervates are formed by the molecular assembly. The combination of proteins and nucleic acids is thought necessary for the proteinoid microspheres to express a function that leads to the emergence of life as the fourth step in chemical evolution. This study, therefore, investigated the adsorption and uptake of nucleic acids onto the proteinoid microspheres. Sheared salmon sperm DNA was added to a dispersion of proteinoid microspheres. The microspheres were then observed using an electron probe microanalyzer (EPMA). The distribution pattern of phosphorus was consistent with that of the spherical carbon and nitrogen, which were identified as proteinoid microspheres in the SEM images. This confirms that nucleic acids were either uptake into the microspheres or adsorption on the microsphere surface. A reconstitution experiment was also performed. After microspheres with nucleic acids were heated to dissolve and then cooled to reconstitute the microspheres. The EPMA observation confirmed the adsorption or uptake of nucleic acids onto the microspheres. It found that under both different timings of microsphere formation and nucleic acid addition, nucleic acids were adsorbed or taken up by the microspheres. In the future, we will confirm whether nucleic acids are taken up inside the proteinoid microspheres or only adsorbed on the surface. In addition, the functional expression of adsorbed nucleic acids, such as transcription and translation, will be clarified.
BG09-A010
Synthesisynthesis of Peptides by UV Irradiation and Synthesis of Authentic Peptides
Yoshiki BANZONO1#+, Koyo MIZUNO1, Kaori NAKASHIMA1, Kazumichi NAKAGAWA2, Hajime MITA1
1Fukuoka Institute of Technology, Japan, 2Kobe University, Japan
There are many organisms on Earth today. However, the origin of life on Earth remains unknown. About 100 amino acids and many organic compounds were found in the meteorites. Amino acids, the minimum unit to sustain living organisms, exist in the universe. Still, no peptides have been detected in meteorites, except for glycylglycine. have been reported for the existence of peptides. Studying whether peptides can be synthesized from amino acids in the space environment is essential. It has been reported that alanylalanine is synthesized by vacuum ultraviolet (VUV) irradiation, which is the most common and chemically reactive in the space environment. We, therefore, decided to study the synthesis of peptides from amino acids other than alanine and the formation of co-peptides from mixtures of amino acids. In the first step, thin films prepared by vapor deposition of two amino acids were irradiated with VUV rays. After irradiation, the products were extracted with water, and the extracts were analyzed by liquid chromatography combined with mass spectrometry. It is necessary to examine the authentic samples of peptides for chromatographic analysis. Some peptides were synthesized using DMATMM as a condensation reagent. In addition to the dimers, trimers were synthesized in the peptide synthesis experiments. Using the L-form for the N-terminal amino acids and racemic amino acids for the C-terminal, two peptides were obtained as diastereomers in the dimer and four in the trimer, and their retention times could be determined by chromatography. Using these authentics, it has been shown that the VUV irradiation of a composite thin film of alanine and serine produced co-peptides Ser-Ala. Further analysis of other combinations of amino acids is in progress. The exposure experiment is now underway to expose thin films of mixed amino acids in the natural space environment at the exposed facility on the ISS.
BG10-A007
The Climate Sensitivity of Vegetation in Tropical Asia
Tin SATRIAWAN#+, Jiaqi TIAN, Xiangzhong LUO
National University of Singapore, Singapore
Changes in global climate have been known to alter the productivity of tropical forest vegetation. To better understand the response of tropical forests to climate change, it is important to study the driving factors of vegetation dynamics. Temperature, precipitation, and solar radiation are potential drivers of vegetation dynamics in the tropics, however, their relative contributions vary between regions due to differences in soil type and community composition across tropical forests. The spatial heterogeneity is particularly high in tropical Asia, therefore, it is important to investigate the influence of climate on vegetation dynamics in the region. In this study, we aim to analyze the climate sensitivity of tropical Asia’s vegetation by answering: (1) what are the main climatic drivers influencing tropical Asia’s vegetation? (2) how does the impact of these drivers vary spatially? This study uses multiple satellite products (e.g., GIMMS NDVI and GLASS LAI) as proxies of vegetation seasonality. We use various statistical methods (i.e., multiple linear regression, machine learning) to infer the changes in vegetation seasonality in response to interannual climatic fluctuations (e.g., gridded temperature, precipitation, and solar radiation from CRU JRA, soil moisture from ESA CCI, and vapor pressure deficit). We expect to see larger anomalies of vegetation when climatic fluctuations are the most pronounced, e.g., during El Nino and La Nina years. We also hypothesize that different regions (e.g., continental vs maritime) would have different resistance to interannual climatic variabilities. Ultimately, our findings will help improve our understanding of the vegetation-climate interaction mechanisms and how different regions may respond to climatic changes in the future.
BG10-A013
Observation Site Coordinated to Eddy Covariance and Remote Sensing Techniques to Verify the Ecological and Productive Functions on Rice Paddy in Naju, South Korea
Bo-Kyeong KIM1#+, Jong-Min YEOM2, Jong-Sung HA2, Hyunki KIM3,1, Hyun-Dong MOON1, Euni JO1, Jaeil CHO1
1Chonnam National University, Korea, South, 2Korea Aerospace Research Institute, Korea, South, 3National Institute of Crop Science, Korea, South
Rice is the major staple food, particularly in Asia region. The flooded condition in rice paddy field will affect not only the agricultural productivity but also the surface energy, water, and carbon exchanges compared to other non-flooding crops. In this study, the Naju observation site on the rice paddy field of Jeollanamdo Agricultural Research and Extension Services, Naju, Jeollanam-do Province, Republic of Korea (N 35.026950°, E 126.82195°) was established in 2020. The simultaneous observation system of H2O/CO2/CH4 gases flux and hyperspectral reflectance and chlorophyll fluorescence on vegetated surface could be valuable for extension from the observed phenomenon in ground-scale monitoring to space-based estimation in upper-scale region. Fluxes, such as net ecosystem exchange, methane emission, and evapotranspiration, was observed with an open-path gas analyzer (LI-7500A & LI-7700; LICOR Inc., USA) and three-dimensional sonic anemometer (CSAT3; Campbell Scientific Inc., USA). The GPP could be derived from eddy covariance method and estimated by observing solar-induced chlorophyll fluorescence (SiF) using hyperspectral instrument (FLOX; JB Hyperspectral Devices, Germany), which is also produce the vegetation indices within visible and near infra-red wavelengths. In addition, the drone monitoring installed with 10 multispectral bands and thermal cameras is performed regularly for the ground-based observation area. The various scaled and instrumental data achieved from the Naju observation site will be helpful for comprehensive understanding of rice paddy ecosystem and validation for satellite-based model.
BG10-A015
Understanding the Fine-scale Space Use and Habitat Selection of Invasive Species: Applying Core Habitat Estimation to Improve Management Strategy
Byungwoo CHANG1+, Wonhee CHO1, Chanwoo KO1, Hyemin KIM1, Yongsu PARK2, Dongwook W. KO 1#
1Kookmin University, Korea, South, 2National Institute of Ecology, Korea, South
In order to eradicate invasive species, spatio-temporal analysis information on the behavioral characteristics of wildlife is important. In previous invasive species management studies, GPS collars were attached to track their movement and the traditional home range estimation technique was used to estimate their home range area. However, for the intensive management of invasive species, new analysis methods are required to consider the behavioral and ecological characteristics of target species in terms of activity patterns at core habitats. Nutria (Myocastor coypus) is a representative invasive species that destroys native ecosystems worldwide. It was introduced to South Korea in 1985 for their economic value (fur farming and food resources), but quickly settled after illegal release. Nutria, a semi-aquatic mammal, mainly lives along the banks of lakes and rivers, building burrows for shelter. Therefore, by analyzing their activity patterns in their critical habitats, it may be possible to obtain information at the particular location of nutria burrows. In this study, we applied the method of analyzing intensity of use within the range of movement to analyze the activity patterns of nutria inhabiting the Upo wetland in Changnyeong-gun, South Korea. We used GPS tracking data of nutria (n=3) to identify the core habitat areas and calculate the revisitation rate of these areas along the movement path. In addition, we analyzed the concentration of specific space use by period and individual, created density map, and identified the particular locations at the core habitats. The results of this study are expected to contribute to the effective control and management of nutria by providing fundamental data for understanding the behavioral characteristics related to their use of burrows.
HS01-A012
Uncertainty Analysis and High-resolution Prediction of Soil Moisture and Streamflow Using WRF-Hydro, PEST, and Deep Learning for Digital Twins
Bomi KIM+, Garim LEE, Sohyeon KIM, Yaewon LEE, Seong Jin NOH#
Kumoh National Institute of Technology, Korea, South
Reliable hydrologic modeling is a key to mitigate climate-related disasters in uncertain environments. However, it is widely known that hydrological models are subject to various uncertainties stemming from the input data, parameters, and model structure. As high-resolution is preferred and required in the era of digital twins and metaverse, challenges for calibrating hydrologic models with limited information are rather increasing. In this study, we will discuss challenges and solutions for sensitivity and uncertainty analysis to calibrate distributed hydrologic models with high-resolution land use and soil information using WRF-Hydro and PEST, model-independent parameter estimation. Then, we will discuss how deep learning approaches such as convolutional neural networks can be combined with physical modeling for high-resolution predictions with computational efficiency. The numerical experiments are conducted in the Kumho River basin in South Korea. The discussion will focus on the feasibility and limitations of the current physical and machine learning approaches for high-resolution digital twins.
HS01-A013
Multivariate Chaotic Analysis of Daily Runoff Series in Savitri River Basin, India
Namitha Elza SAJI1#+, V. JOTHIPRAKASH1, Bellie SIVAKUMAR1,2
1Indian Institute of Technology Bombay, India, 2Tsinghua University, China
The identification of the complexity of runoff is of great use in the water resources assessment and management in a region. It has more importance in today’s world, especially with the occurrence of more frequent and greater intensity of flood events due to climate change. The nonlinear dynamic approach can identify the nature of hydrologic variables with good accuracy. Although the single-variable phase space reconstruction approach has been found to yield useful results for characterization and prediction, more reliable outcomes can be achieved using multiple variables, if data are available. The present study aims to propose a multi-variable phase space reconstruction approach for chaos identification and prediction of daily runoff time series. Eight daily hydro-meteorologic variables namely runoff, rainfall, minimum temperature, maximum temperature, pan evaporation, relative humidity, sunshine duration, and wind speed collected for Savitri basin, India will be considered for phase space reconstruction. The influence of these variables on chaos identification will be investigated by applying False Nearest Neighbour (FNN) algorithm. The FNN is a dimension-based method that identifies the dimension. Here, hydro-meteorological variables observed during 2000–2011 at Birwadi station in the Savitri basin are used to develop the phase space. Initially, the complexity of hydrometeorological variables under consideration is identified individually. The daily hydro-meteorological variables at Birwadi are identified as low-dimensional chaotic systems with dimensions varying from 4 to 7. The phase space for the runoff series using the multivariate concept is reconstructed by using different combinations of runoff with rainfall, minimum temperature, maximum temperature, pan evaporation, relative humidity, sunshine duration, and wind speed.
HS01-A021
Integrated Modeling of Distributed Hydrological Model and 1D River Model on Nakdong River Basin
Hyeonseung KU1+, Hyunuk AN1#, Youngteck HUR2, Ahn JUNG MIN3
1Chungnam National University, Korea, South, 2K-water Institute, Korea, South, 3National Institute of Environmental Research , Korea, South
In the water system of South Korea, since several multi-function weirs have been built as a part of the four major river development projects, the water circulation has changed significantly. It has led to changes in quantity and water ecosystems and has had a significant impact on changes in water quality in rivers. Therefore, it is necessary to analyze and predict the quality and ecosystems of the river due to the influence of multi-functional weirs. In hydrological model, the routing analysis is usually performed by downstream traces such as kinematic waves by assuming a rectangular cross-section; therefore, reliable results cannot be obtained in large watersheds such as four major rivers where hydraulic structures are installed. To overcome this limitation, a distributed hydrology-hydraulic model, K-DRUM, and one-dimensional hydraulic river model, K-River, are integrated and applied on a Nakdong river basin in this study. The K-DRUM can perform detailed hydrologic analysis such as flow velocity, flow rate, and water level at any point in the basin by applying various physical characteristics. K-River can perform hydraulic analysis considering various hydraulic structures such as bridges, weirs. A series of water circulation processes were simulated by integrating K-DRUM and K-River to reflect weir operation. The model built through this study was compared and verified with the inflow amount for dam inflow points in the Nakdong River basin and the water level at several water level points in the mainstream of the Nakdong River for flood season in Repulic of Korea. As a result of the simulation, it was confirmed that the water level, the inflow, and the arrival time were successfully simulated at a meaningful level. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A2C200553012).
HS01-A023
Ensemble Streamflow Prediction Using Ensemble Meteorological Forecast and Dynamic Water Resources Assessment Tool (DWAT)
Jeonghyeon CHOI#+, Cheol Hee JANG, Deokhwan KIM, Hyeonjun KIM
Korea Institute of Civil Engineering and Building Technology, Korea, South
In Korea, weather and climate forecasts have mainly focused on meteorological and climatological aspects. However, it is necessary to prepare ways to utilize weather and climate forecasts that consider the spatial and temporal scale, accuracy, and evaluation scheme for short- and medium-term water resource assessment and analysis. This study predicted the streamflow for the Gyeongan Stream basin to prepare a method for future water resources assessment and analysis. To this end, we first applied the Dynamic Water resources Assessment Tool (DWAT) for the Gyeongan Stream basin, and calibrate it using daily observed rainfall, weather, and streamflow information from 2015 to 2021. A correlation analysis between global climate patterns and domestic meteorological characteristics was performed for the ensemble meteorological forecasts. After that, the climate indices that showed high correlations for each month were selected as predictors to construct the multiple regression model and the artificial neural network model for monthly rainfall and temperature forecasting for 2022. One thousand daily ensemble time series datasets were produced for meteorological stations that affect the targeted study area by downscaling the predicted monthly rainfall and temperature. The generated rainfall and temperature forecast information was used as input data for DWAT. The predicted daily streamflow differs from the one observed, which stems from errors in the predicted ensemble rainfall and temperature information. The result reaffirms the limitation that the error of the hydrologic model results is significantly affected by the error of forcing data sets. Therefore, it is necessary to consider analyzing monthly statistics by converting short- and mid-term water resources assessment and analysis into monthly streamflow. Acknowledgments: This work was supported by the Korea Environment Industry & Technology Institute (KEITI) through the Water Management Program for Drought Project, funded by the Korea Ministry of Environment (MOE), (2022003610002).
HS01-A024
Water Scarcity Risk Assessment in Four Major Basin Areas Using Dynamic Water Resources Assessment Tool
Deokhwan KIM1#+, Jeonghyeon CHOI1, Cheol Hee JANG1, Hyeonjun KIM1, Hyoungsub SHIN2
1Korea Institute of Civil Engineering and Building Technology, Korea, South, 2ERI Co., Korea, South
The complex water use system, such as the intake and drainage of river and groundwater, discharge of sewage and wastewater, and water reuse, significantly affects the availability of water resources in a catchment area during a drought. However, existing assessments for water resource availability during drought do not consider such a complex water usage arrangement, so it is difficult to predict water resource availability with high reliability. Therefore, it is necessary to develop a reliable technique to assess water scarcity risk and resource availability by investigating the interrelation between the detailed water use scheme and hydrological and environmental factors in watersheds during drought. This study used the Dynamic Water resources Assessment Tool (DWAT) to measure the water shortage risk and water resource availability during drought, reflecting the comprehensive water use system and hydrological and environmental factors within the basin area by simulating the four major medium-sized basins (Han River, Nakdong River, Geum River, and Yeongsan-Seomjin River). The results are expected to provide reliable evidence, such as primary data and software for preparing drought response measures. Acknowledgments: This work was supported by the Korea Environment Industry & Technology Institute (KEITI) through the Water Management Program for Drought Project, funded by the Korea Ministry of Environment (MOE), (2022003610002).
HS01-A025
Development and Global Extension of Dynamic Water Resources Assessment Tool (DWAT) Considering Interaction of Surface Water and Groundwater
Cheol Hee JANG#+, Hyeonjun KIM, Deokhwan KIM, Jeonghyeon CHOI
Korea Institute of Civil Engineering and Building Technology, Korea, South
DWAT is a water resources assessment tool that can be used free of charge worldwide and can be applied to small and medium-sized river basins for water resource planning and management that considers surface water as well as groundwater and water usage for various purposes. In particular, DWAT is loaded with a module capable of simulating the runoff process of rice paddies, coupled with a snow-melting module that could reflect the hydrological characteristics of high latitudes and alpine regions, and a parameter optimization function. As of December 2022, WMO is pushing ahead with the "global Hydrological Status and Outlook System (HYDROSOS)" project, one of the major initiatives in the water resources sector. This project utilizes the global climate forecasts to perform the status assessment and outlook of natural streamflow at major points and consists of the following three modules: - A status module that collects and presents hydrological observation data, - A climate forecast module that collects global climate forecasts and converts them into the scale for the required basin, and - A hydrological forecasting module that converts climate forecasts into streamflow. The 18th WMO Congress held in June 2019 decided that DWAT would support the pilot project of HYDROSOS, a major initiative in the field of water resources. As a result, it is expected that Korea's water resource assessment technique will be continuously extended to WMO member countries with the utilization of DWAT. Acknowledgments: This research was supported by Korea Environment Industry & Technology Institute (KEITI) through Water Management Program for Drought, funded by Korea Ministry of Environment (MOE)(2022003610002).
HS01-A040
Simulation of Precipitation Induced Flood Flow in Arid Region
Jennifer DUAN#+
University of Arizona, United States
In arid region, high-intensity and short duration monsoon rainfall can induce severe flash flood in the arid region. The HMS model developed by the US Army Corps Hydrologic Engineering Center has been widely applied in predicting precipitation induced flood flow. However, the traditional CN number approach was challenged by its original definition, and difficulty in taking account of various vegetation species and densities. The CN values were available from the tables in National Engineering Handbook Section 4: Hydrology (NEH-4) are based on two factors: one is the hydrologic soil group, and the other is land use and land cover including the type of landuse, and the type and density of vegetation cover. These CN values were obtained primarily from the small rain-fed agricultural watersheds. The CN method works well for the agricultural watersheds, but it’s less successful for the arid and semi-arid regions where vegetation is typically sparsely distributed with desert shrubs and perennial grass at low elevation, but forest at the higher elevation. The unique vegetation types and spatial distributions limit the applicability of the original CN table (Table 2-2d in TR-55) in the arid and semi-arid region. This paper reports an application of HEC-HMS model to simulate flash flood and sediment transport in an arid watershed in the southern Arizona. The model was used to simulate several largest precipitation events observed from 1970 to 2015. This paper discusses various methods for simulating the rainfall loss, surface and channel flow routing, and soil erosion. Results showed HEC-HMS model can achieve a high accuracy of flow and sediment yield prediction. The threshold value for watershed delineation is critical for HEC-HMS model to converge to accurate results.
HS02-A008
Development of a Surrogate Model to Improve the Efficiency of Groundwater Level Fluctuation Pattern-based Hydrologic Properties Evaluation
Jiho JEONG+, Jina JEONG#
Kyungpook National University, Korea, South
In this study, a method of aquifer hydrologic property estimation incorporating the deep learning method was developed to improve the estimation efficiency of a process-based model based on groundwater level fluctuation (GLF) patterns. As a reference study, a data-driven method suggested by Jeong et al. (2020) was considered; the uncertainty of the GLF patterns resulting from different yearly patterns of precipitation, which were considered as noise in the previous study, was effectively discarded using the newly proposed method of applying the conditional variational autoencoder (CVAE). The CVAE was used to acquire the specific GLF patterns under certain identical precipitation patterns for all the monitoring stations. The data-driven hydrologic property estimation model was developed to predict two hydrologic parameters ( and ) of the process-based model using the generated GLF patterns from the CVAE network as the input variables. The actual GLF and precipitation data that were acquired from nationwide groundwater monitoring stations in South Korea were applied to validate the developed method. It was found that the estimated and target hydrologic properties were highly correlated (correlation coefficients [CC]: 0.9833 and 0.9589 for and, respectively), which significantly improved the results when compared to the previous study (CC: 0.7207 and 0.8663 for and, respectively). Consequently, the developed model can contribute to a more accurate hydrologic property estimation of aquifers. Additionally, it can facilitate efficient groundwater development planning since the manual fitting of the process-based model by an expert is not required.
HS02-A009
Investigation of Influencing Factors of Acoustic Attenuation in the Atmosphere
Linhao FAN#+, Ji CHEN
The University of Hong Kong, Hong Kong SAR
With more research on new artificial rainfall technology in recent years, the concept of guiding the re-distribution of cloud water resources through acoustic waves has begun to gain more attention. Therefore, it is essential to study how acoustic waves attenuate and finally affect the layers of precipitation clouds. However, research on actual atmospheric acoustic attenuation in the outdoor field is not particularly extensive because of the high operating expenses, high requirements of equipment and energy consumption, and complicated environmental environment. Here, we design various case studies based on the existing typical theory of acoustic wave propagation to investigate the main characteristic parameters of the atmospheric acoustic attenuation. To promote the transmission efficiency of acoustic intensity more economically, we choose three characteristic frequencies to evaluate the optimized design of a multi-acoustic source combination layout. This study is of guiding significance for the efficiency improvement of future implementations of the emerging technology of acoustic-induced precipitation.
HS03-A001
Impacts of Meridional Wind and Water Vapor Flux on Regional Long-term and Short-term Precipitation Over Yarlung Zangbo River Basin
Xinzheng TANG#+, Ji CHEN, Dawei WANG
The University of Hong Kong, Hong Kong SAR
The Tibetan Plateau (TP), the third pole of the Earth, is the highest land in the world. Yarlung Zangbo river (YR) basin, located in the southern TP, is the world's highest great river, providing water resources for more than billions of people through several large Asian rivers. Under the control of the interaction between the westerlies and the Indian Summer Monsoon (ISM), the YR basin has undergone significant surface warming during the past five decades. ISM has exported huge atmospheric water vapor to TP, which experienced a weakening trend during the same period. However, to what extent the ISM influences the local precipitation in the YR basin remains uncertain. In this context, it is significant to investigate the regional climate change over the YR basin and the relationship between precipitation here and ISM. In this study, we conduct both long-term climate and short-term weather simulations using the Weather Research Forecasting model to quantify the impacts of the meridional wind on regional precipitation. Besides, we investigate the net water vapor input into three YR basin reaches through four boundaries to reveal the source of the precipitation. The results indicate the critical role of the meridional wind in the precipitation amount and location over the YR basin, especially in the lower reaches. The study would provide a unique insight for climate research and contribute to understanding the precipitation evolution over the TP.
HS03-A005
The Performance of CMIP6 Surface Water and Energy Balance Predictions and its Influence in Pan Third Pole
Zhu LIU#+, Bohan HUANG, Su LIU, Tao SU, Qingyun DUAN
Hohai University, China
The Pan Third Pole (PTP) contains Tibet Plateau and its surrounding regions such as Hindu Kush, Karakoram and Pamirs and it is one of the highest and most fragile as well as rapidly developing regions of the Earth. The water balance and energy balance not only regulate the fundamental water supply and demand as well as thermal conditions on earth but also control various atmosphere and land surface processes. In this study, predictions of water balance components including precipitation, evapotranspiration, runoff and surface energy balance components including net radiation, latent heat and sensible heat from 20 CMIP6 models are evaluated with ERA5 reanalysis data during 1981-2014 over PTP region and its three subregions. Specifically, the annual and seasonal relative bias of different components as well as water and energy imbalance are evaluated. Besides, considering the significantly large difference of CMIP6 multi-year mean air temperature predictions over Tibet Plateau, we investigate its influence on snow depth, frozen soil and runoff predictions. Results show that the spatial patterns of relative bias of water and energy components are quite different among models and significant bias exist for seasonal model predictions. Runoff has relative larger bias compared with precipitation and evapotranspiration for PTP region. Additionally, CMCC-HR4, CMCC-SR5 and CMCC-ESM2 have significant water imbalance because of runoff overestimation and water and energy imbalance are not negligible for seasonal predictions in PTP. The snow depth predictions are not always consistent with temperature bias. CNRM-ESM2-1 overestimates snow depth to 25m with its temperature only underestimated about 3.5 degree Celsius, which might be related to the maximum snow depth restrictions of model structure.
HS03-A008
Spatial and Temporal Analysis of Precipitation Extremities of Eastern Nepal in the Last Two Decades (1997–2016)
Sunil SUBBA1#+, Yaoming MA2, Weiqiang MA2
1University of Chinese Academy of Sciences, China, 2Chinese Academy of Sciences, China
In recent days there have been discussions regarding the impact of climate change and its vagaries of the weather, particularly concerning extreme events. Nepal, being a mountainous country, is more susceptible to precipitation extreme events and related hazards which hinders the socio-economic development of the nation. In this regard, this study aimed to address this phenomenon for one of the most naturally and socio-economically important regions of Nepal, namely, Eastern Nepal. The data were collected for the period of 1997 to 2016. The inter-decadal comparison for two periods (1997–2006 and 2007–2016) was maintained for the calculation of extreme precipitation indices as per recommended by Expert Team on Climate Change Detection and Indices (ETCCDI). Linear trends were calculated by using Mann-Kendall and Sen’s Slope estimator. The average annual precipitation was found to be decreasing at an alarming rate of -20 mm/year in the last two decades’ tenure. In case of extreme precipitation events, Consecutive Dry Days (CDD), one of the frequency indices, showed a solo increase in its trend (mostly significant). Meanwhile, all the intensity indices of extreme precipitation showed decreasing trends (mostly insignificant). Thus, it can be concluded that Eastern Nepal has witnessed some significant drier days in the last two decades, as the events of heavy, very heavy, extremely heavy precipitation events, and annual wet day precipitation (PRCPTOT) were found to be decreasing. The same phenomena were also seen in the Tropical Rainfall Measuring Mission (TRMM) 3B42 V7 satellite precipitation product for whole Nepal.
HS03-A009
Variation of Surface Air Temperature Induced by Enhanced Land–atmosphere Coupling During 1981−2020 in Xinjiang, Northwest China
Yang YANG1+, Zhaohui LIN2, Lifeng LUO3, Linhao ZHONG1, Dabang JIANG2#
1National Institute of Natural Hazards, Ministry of Emergency Management of China, China, 2Chinese Academy of Sciences, China, 3Michigan State University, United States
Land–atmosphere coupling (LAC) is a critical process in the climate system and has great effects on surface air temperature over the humid–dry transition zones. Using ERA5/ERA5-land reanalysis data, we show that summer temperature anomalies over Northwest China (NWC), known as one of the most important LAC hotpots in China, are significantly correlated with the LAC strength during 1981−2020. The stronger the coupling strength between air temperature and land surface, the more pronounced decrease in air temperature and extreme hot days over NWC. Among different pathways of LAC processes, soil moisture–latent heat flux–air temperature pathway contributes the most to the overall temperature changes in summer (> 30−40%). By analyzing the possible local and non-local physical links in this relationship, we show that wave-trains from Arctic Oscillation–East Atlantic/West Russia-like circulation patterns stimulate a meridional fluctuation of westerly airflow over mid-high latitudes of Eurasia, manifested by the intensification of Ural ridge and Central–Asia trough. Large moisture, therefore, converges into NWC, leading to excessive precipitation and deficient incident solar radiation reaching the land surface. In such cases, wetter and cooler soil states accelerate the cooling of the environment through a series of feedbacks between lands, land–atmosphere exchanging fluxes, and air temperature locally, significantly enhancing the LAC strength. Our study provides insight into the physical processes causing variations in summer temperature over a typical LAC hotspot and suggests that the role of land surface–atmosphere interactions need to be considered when studying temperature extremes under climate change.
HS03-A014
Implementation of the Calculating Soil Freezing and Thawing Fronts Parameterization in the Earth System Model CAS-ESM
Ruichao LI#+, Zhenghui XIE
Chinese Academy of Sciences, China
Permafrost and seasonally frozen ground are an important part of the cryosphere. it is widely distributed and the cycle of freezing and thawing of frozen ground has important influence on energy and water exchanges between the land surface and the atmosphere. In this study, the calculating soil freezing and thawing fronts parameterization was implemented into the earth system model of Chinese Academy of Sciences (CAS-ESM) and its land component the Common Land Model (CoLM) to investigate dynamic change of soil freezing and thawing fronts and the effects of soil freezing and thawing fronts on soil temperature and soil moisture. Our results showed that the developed models could reproduce the soil freezing and thawing process and the dynamic change of soil freezing and thawing fronts. We also evaluated the effects of soil freezing and thawing fronts on soil temperature and soil moisture. These results would be constructive to a better understanding of the freeze and thaw cycle process.
HS03-A016
The GEWEX Regional Hydroclimate Activities in Asia
Petrus (Peter) VAN OEVELEN#+
George Mason University, United States
In the early 1990s a newly formed GEWEX Program (Then called the Global Energy and Water cycle Experiment now: Global Energy and Water EXchanges project) launched a regional study to measure and model regional variations in the water and energy cycle. A continental scale experiment was needed to develop the ability to measure and model the components of the water and energy cycles over a macroscale land surfaces from smaller scale observations. These projects are now called Regional Hydroclimate Projects and are much broader than just the geophysical science and cover the entire earth system. In this presentation an overview of the evolution of these RHPs is shown along with a vision on the current and future relevance and importance of such projects along with the necessary additional activities such as cross cutting activities to link regional science to global efforts.
HS03-A029
The Impacts of Third Pole Snow Assimilation on Seasonal Meteorology Predictions
Lu LI1#+, Wei LI2, Jie CHEN2, Yvan ORSOLINI3, Retish SENAN4, Patricia DE ROSNAY4
1NORCE Norwegian Research Center, Norway, 2Wuhan University, China, 3Norwegian Institute for Air Research, Norway, 4European Centre for Medium-Range Weather Forecasts, United Kingdom
The Third Pole (TP) contains the largest amount of snow outside the Antarctic and Arctic regions, and is the source of many major rivers in Asia. An accurate seasonal hydrometeorological forecast is of great importance for this region. The fifth-generation seasonal forecast system of the European Centre for Medium-Range Weather Forecasts (SEAS5) provides global long-range meteorological forecasts including over the TP. However, SEAS5 uses land initial conditions produced by assimilating Interactive Multi-sensor Snow and Ice Mapping System (IMS) snow data only below 1500 m altitude, which may affect the forecast skill of SEAS5 over mountainous regions like the TP. In this study, we used twin ensemble reforecasts, which are initialized with and without snow assimilation above 1500 m altitude over the TP for spring and summer 2018, to investigate the impacts of snow assimilation on the forecasts of meteorological variables (e.g., snow, temperature, precipitation, and streamflow). We found that significant changes occur in the springtime. The reforecasts, which is without snow assimilation, overestimate snow cover and snow depth while underestimating daily temperature. Precipitation reforecasts perform better in the west TP than in the east TP compared with satellite-based data. Besides, the snow assimilated reforecasts of snow cover, snow depth and temperature are improved in the spring over TP. The snow assimilation experiment significantly increases temperature and precipitation for the east TP comparing with that of experiment without snow assimilation. The higher temperature after snow assimilation, in particular the cold bias reduction after initialization, can be attributed to the effects of a more realistic, decreased snowpack, providing favourable conditions for generating more precipitation. Overall, snow assimilation can improve seasonal forecasts through the interaction between land and atmosphere.
HS04-A003
Flow Characteristics of the Hornad River and the Anthropogenic Impact of the Ruzin Dam
Maria HLINKOVA#+, Martina ZELENAKOVA
Technical University of Kosice, Slovakia (Slovak Republic)
The aim of the study is to analyse the seasonal and term variability of the flow of the Hornad River. The annual RBI and Cv values show an even distribution of values over the analysed period 1973–2020 at the hydrological stations Spisska Nova Ves and Margecany. Higher annual amplitudes of RBI values were recorded at the Kysak post below the Ruzin II water reservoir, while lower amplitudes of RBI values at the posts located above the reservoir. The analysis of monthly mean RBI values showed that in the period from 1973–2020 the RBI values ranged from 0 to 0.49 at the hydrological stations Spisska Nova Ves and Margecany, while at the Kysak station, the RBI indicator ranged from 0 to 0.57, which indicated large changes in short-term flows. The maximum value of the RBI index occurred in June 1973 (0.57) at the Kysak station and in July 2008 (0.49) at the Margecany station (0.49) and the Spisska Nova Ves station (0.48), which was the result of very high precipitation (over 170 mm in a month). The correlation coefficient r between the RBI index and the monthly sum of rainfall shows that the highest correlation was in October, November, and December (r> 0.8) at the hydrological stations Spisska Nova Ves and Margecany, while at the Kysak hydro-logical station the highest value of r was recorded in October (r = 0.73). The lowest r values were recorded in February and March at all stations, and they ranged from 0.28 to 0.39 and were related to thaws, which could cause fluctuations in flows. The possibilities of water retention in the Ruzin reservoir are limited, which is visible in the case of very high precipitation.
HS04-A004
Using Integrated Flow Modeling to Understand Complex River-aquifer-sea Interactions in the Guangdong-Hong Kong-Macao Greater Bay Area
Xiaoli WANG+, Ji CHEN#
The University of Hong Kong, Hong Kong SAR
Hydrological processes in mega deltas are generally complex due to river-aquifer-sea interactions, especially under the joint influences of intensifying climate change and human activities. Systematic and quantitative understanding of the river-aquifer-sea interactions and their response to natural and anthropogenic disturbances is a prerequisite for the effective management of water resources and ecosystem health. In this study, we developed a high-resolution integrated hydrological model for the Guangdong-Hong Kong-Macao Greater Bay Area, one of the four largest city-clusters in the world with dense population and intensive socioeconomic development. The study was intended to quantify the watershed hydrological cycle and land-ocean interactions to support sustainable water management in the region. After being calibrated and cross-checked based on observations at gauging stations and independent remote-sensing products, the flow model was used to explore the influences of inland and ocean processes on river-aquifer-sea interactions at different time scales. The pivotal role of ocean tides in shaping the coastal groundwater system was closely examined and analyzed. Moreover, the total flux of the fresh submarine groundwater discharge of the terrestrial source was computed by the flow model, together with its spatial and temporal variations.
HS04-A007
Calibrate Tropical Forest Coexistence in Ecosystem Demography Models Using Multi-objective Optimization
Yanyan CHENG#+, Christine SHOEMAKER
National University of Singapore, Singapore
Tropical forest diversity governs forest structures and compositions and consequently responses and feedbacks of tropical forests to environmental changes. Better representation of forest diversity in ecosystem demography (ED) models within Earth system models is thus necessary to accurately capture and project how tropical forests affect Earth system dynamics subject to climate changes. However, achieving forest coexistence in ED models is still an ongoing research challenge. This study applies an advanced Multi-Objective Population-based Parallel Local Surrogate-assisted search (MOPLS) optimization algorithm to simultaneously calibrate ecosystem fluxes and coexistence for two physiologically-distinct tropical forest species in a size- and age-structured ED model with realistic representation of wood harvest. MOPLS exhibits satisfactory model performance in capturing hydrological and biogeochemical dynamics (both calibrated and non-calibrated variables) that observed in Barro Colorado Island, Panama, as well as robustly achieves coexistence for the two representative tree species. Given the same ensemble size, MOPLS results in much more simulations with stable coexistence than a random sampling strategy, demonstrating its effectiveness in calibrating coexistence for tropical trees. The optimal solution is applied to investigate the recovery trajectories of forest biomass after various intensities of clear-cut deforestation. We find that a 20% selective logging can take approximately 40 years for aboveground biomass to return to the initial level, due to the slow recovery rate of late successional trees. This study lays the foundation to calibrate coexistence in ED models. MOPLS can be an effective tool to help better represent tropical forest diversity in ESMs and guide forest management practices.
HS04-A009
Habitat Suitability Analysis Considering Low-flow and High-flow Periods – A Case Study in Shuangxi River of Taiwan
Kwan Tun LEE#+, Huan-Yuan CHEN, Cho-Min YANG, Jing-Zong YANG, Nai-Kuang CHEN, Ta-Chun CHIEH, Pin-Chun HUANG, Yu-Han HSU, Yu-Hsun LIAO, Yi-Ting LIN, Ching-Wen HSU, Chiao-Ju LEE, Han-Chung LIN, Kuo-Feng TSENG
National Taiwan Ocean University, Taiwan
This research analyzes the physical characteristics of the habitat in the Shuangxi River Basin of Taiwan. Due to the lack of flow records in the study watershed, geomorphologically-based models suitable for ungauged watershed analysis were developed for hydrological analysis. In-site water level and flow velocity measurements were used to calibrate the parameters of the hydrological models. Using the aforementioned hydrological analysis results and substituting them into a two-dimensional hydraulic model, we can simulate the spatial distribution of water depth and flow velocity in the study channel reach. Acrossocheilus paradoxus and Candidia barbata were selected as the target fishes for habitat evaluation. Two specified flow values, the low and the high flows, were chosen to assess the habitat suitability. The low flow (Q95%) indicates 95 percent time flow equaled or exceeded the flow value, and the high flow indicates a flood corresponding to the 5-yr return period flow (Q5) condition. Considering the low-flow period, a minimum required water depth of 15 cm was set for the target fishes to assess the habitat suitability. The result shows that the upstream inflow of Q95% can provide continuous water paths for the movement and survival of the target fishes. A fish-preferred-swimming path can then be delineated in the study channel reach during the low-flow period. In considering high flow velocity during the flood period, the prolonged-swimming speeds of the target fishes were used to assess the habitat suitability. The result shows that the low-velocity areas, where suitable for the target fish, were only 11.16% in the channel reach and mainly distributed in the riparian areas near the river bank. Therefore, the shoal areas can provide safe habitats to avoid fish being washed downstream during the flood.
HS04-A014
Changes of River Channel and Habitat Conditions by Vegetation Density
Mikyoung CHOI1#+, Hyunuk AN1, Chang Lae JANG2
1Chungnam National University, Korea, South, 2Korea National University of Transportation, Korea, South
Reduction of sediment flow and control of flow rate due to dam operation accelerates vegetation growth and succession, and then these vegetation affect changes in riverbed and biological habitats. In this study, we simulate how the vegetation affects river channel change using a numerical model (Nays2D), and try to identify fish habitat changes using the physical habtiat suitability Model (PHABSIM). Nays2D model was conducted according to 8 scenario by 2 types of flow (dam outflow, 2-year frequency flow rate) and 4 types of vegetation density (no vegetation, current vegetation density, density decrease, density increase) for 2 km the Geum River in Korea. The result of riverbed change (elevation, water depth and velocity) simulated by Nays2D were used as input data for PHABSIM model. The target fish species is Zacco platypus, and the Weighted Usable Area (WUA) for each scenario was calculated and analyzed. As a result, WUA value was the highest when the riverbed change not reflecting the vegetation, and the WUA value was the lowest riverbed change with increased vegetation density both of 2 flow conditions. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A2C200553012) and Korea Environment Industry & Technology Institute(KEITI) through the Water Management Project for Drought, funded by Korea Ministry of Environment(MOE) (2022003610004)
HS04-A016
Exploring the Effects of Environmental Factors on Macroinvertebrates in Mountainous Rivers: Lai Chi Wo River in Hong Kong, China
Zhaofeng HAN1#+, Ji CHEN1, Yi LU2,1, Qian XU1
1The University of Hong Kong, Hong Kong SAR, 2Hong Kong Metropolitan University, Hong Kong SAR
Rivers have always been the foundation of human survival and development, and an important source of fresh water and food. However, with the rapid economic development, the pressure on the river system have increased dramatically, threatening and deteriorating the environmental and ecological conditions. Society needs to clarify the various interactions among water movement, pollutant transport, and biological organisms in aquatic environment to protect and restore riverine ecologies. According to the research focus, this study explores the interrelationships between macroinvertebrates and environmental factors with structural equation modeling. This study indicated that PLS-SEM would provide more precise understanding of the direct and indirect effects of environmental factors on macroinvertebrates than linear fitting and principal component analysis methods.
HS04-A018
Comprehensive Analysis of Flow Characteristics in Stepped Fishway with Experimental and Numerical Approaches
Chanjin JEONG1+, Hyung-Ju YOO1, Hyungsuk KIM2, Seungoh LEE1#
1Hongik University, Korea, South, 2Kunsan National University, Korea, South
General purpose of fishway in streams is to minimize the negative impact of the river ecosystem due to streamwise discontinuation induced by transversal structures such as barriers, weirs and dams. When constructing a fishway, the ecological characteristics of the fish community such as the ascending capacity of migratory fish should be considered. Therefore, it is necessary to know the hydraulic characteristics near a fishway whether it works properly or not for fish passing. The maximum flow velocity within the fishway should be less than possible swimming speed of a fish at each step, and the flow characteristics within the fishway could be appropriate for the easy and safe ascending. In this study, the flow characteristics near a stepped fishway were measured using the LDV(Laser Doppler Velocimeter). In the hydraulic experiment, the velocity fields at the downstream for each step were measured and turbulent productions were calculated. Experimental results using LDV were also compared with those calculated with FLOW-3D, a three-dimensional numerical model. A total of four turbulence models, (k-epsilon), renormalized group (RNG), (k-omega), and large eddy simulation (LES), inside the FLOW-3D were used to select the most suitable turbulence model for a stepped fishway. In addition, the results of this study are expected to contribute as fundamental data for the fishway design to archive its purpose considering flow characteristics.
HS04-A019
Annual Precipitation Explains Variability in Dryland Vegetation Greenness Globally But Not Locally
Anna UKKOLA1#+, Martin DE KAUWE2, Michael RODERICK3, Arden BURRELL4, Peter LEHMANN5, Andy PITMAN1
1UNSW Sydney, Australia, 2University of Bristol, United Kingdom, 3The Australian National University, Australia, 4Woodwell Climate Research Center, United States, 5ETH Zurich, Switzerland
Dryland vegetation productivity is strongly modulated by water availability. As precipitation patterns and variability are altered by climate change, there is a pressing need to better understand vegetation responses to precipitation variability in these ecologically fragile regions. We present a global analysis of dryland sensitivity to annual precipitation variations using long-term records of Normalised Difference Vegetation Index (NDVI). We show that while precipitation largely explains spatial gradients in NDVI across dryland regions, precipitation only accounts for <26% of temporal NDVI variability over most dryland regions. This suggests that drylands are highly resistant to annual precipitation variability despite water availability playing a major role in determining vegetation greenness across dryland regions. Earth system models (ESMs) from the latest Coupled Model Intercomparison Project overestimate the observed vegetation sensitivity to precipitation variability up to three-fold, particularly during dry years. With projections of increasing meteorological drought, ESMs are likely to overestimate the impacts of future drought on dryland vegetation with observations suggesting that dryland vegetation is more resistant to increasing precipitation variations than ESMs project.
HS04-A023
Identification of a Function to Fit the Flow Duration Curve and Parameterization of a Semi-arid Region in North China
Dengfeng LIU1#, Lan MA1+, Qiang HUANG1, Fengnian GUO1, Xudong ZHENG1, 静 赵2, Jinkai LUAN3, Jingjing FAN4, Guanghui MING5
1Xi'an University of Technology, China, 2西安理工大学, China, 3Chinese Academy of Sciences, China, 4Hebei University of Engineering, China, 5Yellow River Engineering Consulting Co., Ltd., China
The discharge process has undergone major changes in many river basins throughout the world as a result of the simultaneous influences of global climate change and human activity. Flow duration curves (FDCs) are crucial indicators of river basin's hydrological processes. However, it is challenging to compare FDCs in a quantitative way. This study will identify the best function with which to fit the flow duration curve in a semi-arid region of North China, so as to quantify the FDC, and parameterize the function of the FDC of the region in order to describe the FDCs of ungauged basins. In this work, six small- and medium-sized catchments in North China are selected as the study area, and three functions, i.e., Log Normal, Generalized Pareto and H2018 function, were chosen to fit the FDC at nineteen hydrological stations. The relationship between the parameters of the FDC and the basin characteristics, such as the climatic factor and geographical features, were analyzed. A regression formula of the parameters of the FDC function was established, and its spatial and temporal distributions were examined. Based on the evaluation of four indicators, the Nash-Sutcliffe efficiency, the root mean square relative error, the Logarithmic Nash efficiency coefficient and the coefficient of determination, the results demonstrate that the H2018 function can match FDCs the best. Through the annual runoff, annual precipitation, precipitation in summer, potential evapotranspiration, catchment area, mean elevation, length of the main channel and maximum flow frequency, the parameters of a, b, and k in the H2018 function can be formulated. The regression formula constructed in this study can obtain a regional flow duration curve with satisfactory performance, which provides a reference for the validation of remote sensing based runoff data in ungauged regions.
HS04-A024
Soil Hydraulic Parameters Inversion Based on HYDRUS-2D Model
Xinmei HAO#+
China Agricultural University, China
Although many studies have been conducted to investigate soil water movement parameters by the inversion of the HYDRUS model, studies on the spatial and temporal variability of soil hydraulic parameters on an agricultural land, especially under intensive irrigation, are still lacking. In this study, soil hydrological parameters at different depths at different growth stages were estimated using HYDRUS-2D model inversion based on soil water content data measured in a vineyard. The performance of the estimated parameters in predicting soil water content for an independent validation period were evaluated, and the temporal variability of those parameters were analyzed. The results showed that the parameters from the inversion performed better than the predicted parameters of Rosetta model for most cases. The inversion simulations were best in the split layer case during fruit expansion and color change without irrigation. Soil hydraulic parameters from the inversion were only applicable to predicting soil water content under similar conditions as used in the inversion, and the simulation accuracy became significantly lower when the conditions varied greatly with the conditions for the inversion. The three parameters Ks, α, and n derived from the inversion showed spatial and temporal variability with different magnitudes, with Ks and n showing smaller spatial and temporal variability, and α having the largest spatial and temporal variability. The results of the study are of great scientific significance for accurately predicting the variability of soil water content in agricultural fields, so as to develop reasonable irrigation schemes and improve water use efficiency in the areas.
HS07-A006
Global-scale Interpretable Reconstruction of Compound Drought and Heatwaves Utilizing Anomalies of Atmospheric Dynamics
Zhenchen LIU#+, Wen ZHOU
Fudan University, China
Droughts and associated near-surface temperature anomalies can be attributed to amplified vertical subsidence and anomalous anticyclonic circulations from dynamic perspectives. However, two open and interesting issues remain unknown: 1) whether hydrometeorological situations under droughts can be reproduced directly utilizing variability of atmospheric dynamics, and 2) what specific roles atmospheric dynamics play in drought reconstruction. To explore them, this study employs three kinds of dynamical features (i.e., vertical velocity, relative vorticity, and horizontal divergence) for hydrometeorological reconstruction (e.g., soil moisture, and evaporation) under drought situations through an ensemble learning method. Regarding the 2010 European summer mega hot drought and 2015/2016 tropical South America hot drought, reconstruction of spatial patterns and intensities on the interannual scale performs relatively well, seemingly regardless of seasonality and drought-inducing mechanisms. More importantly, from interpretable perspectives, global-scale analysis on dynamical contributions help discover unexpected dynamically drought-inducing roles and associated latitudinal modulation. That is, low-level cyclonic/anticyclonic anomalies contribute to drought development in the northern middle and high latitudes, while upper-level vertical subsidence contributes a lot to tropical near-surface temperature anomalies concurrent with droughts. These achievements could provide potential guidance for conceptual models of drought monitoring and prediction in different geographic regions. The DOI-based linkage is https://doi.org/10.1175/JHM-D-22-0006.1.
HS07-A008
Development of the China Meteorological Administration Land Surface Data Assimilation System (CLDAS-Prcp) Multi-source Precipitation Fusion Dataset and Its Evaluation of Soil Moisture and Snow Simulation Effects
Shuai SUN1+, Chunxiang SHI2#, Shuai HAN2, Junxia GU2, Bin XU2
1National Meteorological Information Center, China, 2China Meteorological Administration, China
Precipitation plays a role in climate change, agricultural development, water use and management. Howerver, there are no long-term, high spatiotemporal resolution, high-quality precipitation datasets in China. To address these issues, in the China Meteorological Administration (CMA) Land Data Assimilation System (CLDAS), we blended the Climate Prediction Center (CPC) morphing technique (CMORPH) and Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA2) precipitation datasets with more than 60,000 CMA precipitation in-situ data using multigrid variational analysis and temporal downscaling to produce a multi-source precipitation fusion dataset for China (CLDAS-Prcp). This dataset covers all of China at a resolution of 6.25 km at hourly intervals from 1998 to 2022. We evaluated the CLDAS-Prcp dataset using CMA and Ministry of Water Resources (MWR) precipitation in-situ data separately. Our results show that the CLDAS-Prcp dataset represents reasonably the spatial distribution of precipitation in China. Using the CMA stations to evaluate CLDAS-Prcp indicates that the CLDAS-Prcp performs better than the MERRA2 precipitation, CMORPH precipitation, GLDAS-V2.1 precipitation, and CLDAS-V2.0 winter precipitation, as compared to the meteorological observational precipitation. Using the MWR stations to evaluate CLDAS-Prcp indicates that the CLDAS-Prcp dataset performs better than the IMERGE precipitation dataset and is similar to the CLDAS-V2.0 summer precipitation dataset. To further validate the simulation effect of CLDAS in soil moisture and snow depth, we used CLDAS-Prcp as well as CLDAS temperature, pressure, humidity, wind, and solar radiation to drive the Noah-MP land surface model for the simulation of soil moisture and snow depth in China. The results showed that the simulated soil moisture and snow depth driven by CLDAS-Prcp are better than the GLDAS-2.1 soil moisture and snow depth. Overall, the CLDAS-Prcp can meet the needs of the land surface models and hydrological research in China.
HS07-A009
Increasing Global Precipitation Whiplash Due to Anthropogenic Greenhouse Gas Emissions
Xinxin WU+, Xuezhi TAN#
Sun Yat-sen University, China
Precipitation whiplash including abrupt shifts between wet and dry extremes can cause large adverse impacts to human and natural systems. Observed and projected changes in occurrences of sub-seasonal precipitation whiplash remain not quantified, and response of precipitation whiplash to anthropogenic forcings remains unknown. We detect historical and projected future changes in whiplash and investigate the role of individual anthropogenic influences on these changes. Results show that the occurrence frequency of global (land) precipitation whiplash is expected to be 2.6 (3.5) times higher than that in the current period by the end of the 21st Century, with increasingly rapid and intense transitions between the two extremes. The most dramatic increases of whiplash show in the polar and monsoon regions. Changes in precipitation whiplash are concurrent with changes in precipitation totals with a much greater rate of change. Anthropogenic greenhouse gas (GHG) and aerosol (AER) emissions have increased and decreased precipitation whiplash, respectively. Anthropogenic GHG emissions are projected to increase ~40% occurrences of precipitation whiplash (mean of dry-to-wet and wet-to-dry extremes), given GHG are projected to sharply outpace of AER after the 2020s. The precipitation whiplash between dry and wet extremes is driven by shifts in circulation patterns conducive to precipitation extremes. Changes in precipitation regimes and circulation patterns will potentially challenge the current actions to water resources management and disaster prevention.
HS07-A014
Increased Risk of Compound Flood-heat Extremes in a Warming Climate
Jun ZHOU1+, Chuanhao WU1#, Pat YEH2, Jiali JU3, Lulu ZHONG1, Saisai WANG1, Junlong ZHANG4
1Jinan University, China, 2Monash University, Malaysia, 3China University of Geosciences, China, 4Shandong Normal University, China
Compound flood-heat extreme (CFHE) is a successive extreme event that threatens human health, economy, and building environment security that has attracted extensive research attention recently. However, the risk of global CFHE in a warming climate is unclear given the large uncertainties in climate change projections. Here, we present a global-scale evaluation of the projected changes and uncertainty in CFHE characteristics within the ISIMIP 2b framework based on the multi-model ensemble of 20 members (5 global water models × 4 global climate models) under two representative concentration pathway (RCP) scenarios (RCP2.6 and RCP6.0). The results show that CFHE frequency is projected to increase nearly globally especially in tropical (e.g., north South America, central Africa, and southeast Asia), and some temperate (e.g., eastern and southern Asia) regions. Furthermore, the higher projected CFHE frequency is generally accompanied by larger model uncertainty. Relative to the 1970-1999 baseline period, the CFHE land exposure is expected to increase by 10% (20%) by the end of this century under RCP2.6 (RCP6.0). The interval between flood and heatwave in CFHE tends to decrease (by up to 3 days) in most global regions under both RCPs, implying more intermittent CFHE occurrence under future warming. Attribution analyses suggest that the change of flood frequency contributes more to the change of CFHE frequency than that of heatwave in most global regions.
HS07-A016
Projecting Spatial and Temporal Changes of Rainfall Events Using CMIP6 Scenarios in Ca River Basin, Vietnam
Ju-Young SHIN1, Pham Van CHIEN2, Vo Cong HOANG2, YeonJi CHUNG3+, Myoung-Jin UM3#
1Kookmin University, Korea, South, 2Thuyloi University, Viet Nam, 3Kyonggi University, Korea, South
Climate change is causing significant change in the intensity, frequency and amount of rainfall in Vietnam. To attenuate the adverse effects of the rainfall changes on people’s life, the future projection of the rainfall changes induced by climate change in Vietnam is essential. Some studies have investigated the changes of rainfall events using CMIP5 climate change scenarios in Vietnam. Recently, CMIP6 climate change scenarios released and some studies have shown that the climate change scenarios from CMIP6 would be more reliable than those from CMIP5. Thus, spatial and temporal changes of rainfall events in Vietnam should be projected using climate change scenarios from CMIP6 and these projections should be analyzed. Hence, this study aimed to investigate spatial and temporal changes of rainfall events in Ca river basin in Vietnam using the climate change scenarios from CMIP6. Climate change scenarios from 26 CMIP6 models were used for monthly precipitation projections. Precipitation observations in eight ground weather stations near Ca river basin were employed to correct biases in monthly precipitation projections. There are large spatial variations in annual and seasonal precipitation within the eight stations. Overall, the total annual precipitation is increased. The autumn precipitation increases while the winter and spring precipitation decreases. Hence, there are possibility to increase magnitude of floods and severity of drought in Ca river basin in Vietnam.
HS07-A018
Projection of Future Drought Characteristics Using the Multiple Drought Indices Under SSP Scenarios in South Korea
Songhyun KIM+, Won-Ho NAM#
Hankyong National University, Korea, South
Recently, climate change has caused abnormal weather worldwide. Europe experienced a record heat wave and drought in 500 years, a severe drought in 1,200 years in the southwestern United States, and China experienced a heat wave in 60 years. Drought can have a serious social and economic impact on the entire agricultural system because of its wide range, and it is expected that the intensity and frequency of natural disasters such as drought will increase due to climate change. The trend of drought in South Korea has been increasing rapidly since 2000, and in 2015 and 2017, there was an unusual extreme drought, showing a different trend from before 2000. Therefore, in order to prepare for the occurrence of drought due to future climate change, it is required to establish a long-term drought outlook and adaptation strategy. In the Intergovernmental Panel on Climate Change (IPCC) 6th evaluation report, a Shared Socioeconomic Pathways (SSPs) scenario considering future socioeconomic changes and climate change mitigation efforts was developed through Coupled Model Intercomparison Project 6 (CMIP6). The SSP includes various factors of change, such as demographics, economic development, ecosystem, institutional, technological development, and policy development. Various drought indices were calculated based on the SSP scenarios calculated through 18 global climate models provided by CMIP6. The SSP5-8.5 scenario was used for the climate change scenario, and the Standardized Precipitation Index (SPI), Effective Drought Index (EDI), and Standardized Precipitation Evapotranspiration Index (SPEI) were applied to analyze the prediction and variability of each future drought index in South Korea.
HS07-A019
Dynamic Prediction and Early Warning Model of Urban Flood Ponding Process Based on Data-driven
Huiliang WANG, Yihong ZHOU#+, Zening WU
Zhengzhou University, China
Frequent urban floods disasters have become a major threat to cities, causing huge loss of life and property. To reduce the potential losses, it is important to improve the prediction ability of urban flood disasters. Previous studies have confirmed that the data-driven urban flood model can mine the nonlinear relationship between the driving factors and the target variables. However, few studies systematically describe how to use urban flood disaster data to realize dynamic prediction and early warning of ponding process. Therefore, this research seeks to propose a set of methods for dynamic prediction and early warning of urban flood from the perspective of data-driven to improve the accuracy and timeliness of urban flood prediction. Firstly, by using the spatial autocorrelation analysis and logical regression method to screen the sensitive index combination of urban flood prediction, the optimal index combination scheme suitable for the urban flood prediction was proposed. Secondly, three classical machine learning models were used to construct the prediction model of urban flood ponding process. On this basis, the improved Bayesian model average (BMA) method was used to dynamically couple the prediction results of the three models, and the integrated urban flood prediction model with dynamic weight was constructed. Finally, the modified rainfall forecast data was used to drive the integrated model to dynamically forecast the ponding process, realizing the rolling forecast and early warning of the urban flood. The results show that the Nash-Sutcliffe efficiency coefficient (NSE) of the integrated model was 0.986, the prediction accuracy of the integrated model was 11.4% - 50.4% higher than that of single model, which indicates that the proposed integrated prediction model based on data-driven has significant advantages in correcting the prediction bias, and can provide guidance for accurate and rapid urban flood ponding process prediction.
HS07-A020
Evaluation of the Stability of River Embankments Considering Climate Change
Sungho LEE1#+, Ingi YOO1, Jung Soo KIM2
1C&I Tech., Korea, South, 2University of Bucheon, Korea, South
Due to heavy localized rains and typhoons, which are caused by abnormal weather patterns, there is continued human loss of life and property damage in disaster-prone areas. In Korea, most rainfall occurs in summer, and runoff is concentrated in rivers in a short period of time, causing rapid fluctuations in river water levels. These sudden changes in water level can damage river levees and make them less stable, increasing the risk of flooding and causing loss of life in cities located near the levees. Therefore, it is important to regularly evaluate and maintain the stability of riverbanks to minimize the impact of natural disasters. In this study, the Levee Flood Vulnerability Index(LFVI) developed by referring to the Flood Vulnerability Index(FVI) was applied to evaluate the stability of river embankments when rainfall was applied considering climate change. The LFVI is a new technique developed by borrowing the format of the FVI and composing factors suitable for river embankments. It is a method of calculating the vulnerability index by calculating weights using an entropy technique based on the values of 7 factors. The study applied a climate change scenario to analyze the LFVI of river embankments along the Namhan River under rainfall scenarios in 2016, 2040 and 2070. The results of the analysis revealed a range of grades from 1 to 6, with the LFVI decreasing as climate change progressed, indicating potential concerns about stability. Acknowledgement: This work was supported by Institute of Information and communications Technology Planning and Evaluation (IITP) grant funded by the Korea government(MSIT) (No. 2022-0-00035, Development of Safety Management System for Deteriorated Reservoirs and River Embankment using Converged-Distributed Architecture with Composite IOT Sensors and AI Techniques).
HS07-A022
Assessing Human Contribution of a Drought via CMIP6 Models: A Case Study of the 2021 Iran Drought
Jonghun KAM#+
Pohang University of Science and Technology, Korea, South
In 2021, 4.9 million people over Iran, particularly rural areas, were at medium and high risk of drought impacts. The 2012 annual precipitation over Iran was lowest since 1979 while the level of public awareness of the ongoing drought was low, possibly due to the antecedent wet condition in 2020. The Arabian Subtropical High (ASH) expanded and was strong over 2020/21. The understanding of this event remains limited from the following perspectives: 1) How unusual the Iran drought in 2021 was? and 2) Was it attributable anthropogenic forcings? In this study, an extreme event is the unprecedented Iran drought in the calendar year 2021, defined by the 12-month standardized precipitation index (SPI12) calculated from the regional averages over Iran, excluding desert areas. Firstly, we evaluate the performance of the 13 CMIP6 models for the precipitation seasonality. Secondly, we use the CMIP6 models that capture well the precipitation seasonality and then construct the SPI12 distributions of the CMIP6 models for individual experiment forcing ensemble runs (historical, greenhouse gas-only, aerosol-only, and natural-only) and their SPI12 distributions over 2002–2021. Lastly, we compute the attributable probability ratio of the 2021-like drought to anthropogenic forcings in terms of drought intensity, persistence, and severity. Results show that the 2020/21-like severe and long-lasting Iran droughts have become more probable by at least 50% due mainly to anthropogenic greenhouse gas increases. In closing, the need for climate change adaptation for long-lasting Iran drought is discussed.
HS07-A025
Changes in Sediment Discharge Due to Climate Change Considering Sediment Production Factors
Riho KIDO1#+, Takuya INOUE1, Misako HATONO1, Kazuki YAMANOI2
1Hiroshima University, Japan, 2Kyoto University, Japan
Global climate change will have a significant impact on sediment discharge due to heavy rainfalls associated with climate change. Increase in sediment discharge will affect downstream riverbed form and channel conveyance capacity, causing damage such as levee breaks, overflows, and bridge failures. Climate change predictions require a large ensemble calculation to account for uncertainties. As a result, the calculation results of sediment discharge using the climate change predictions are also bigdata. However, there is no established method for evaluating the results of these large sediment discharge predictions. In this study, we investigate changes in sediment discharge based on changes in the factors of sediment production due to climate change using a physics-based model that can account for slope failure, channel erosion, and mixed grain-size sediment. Our study site is the upper reaches of the Pekerebetsu River in Hokkaido, Japan. Heavy rainfall in this basin was recorded during the heavy rainfall in Hokkaido in August 2016. We evaluate extreme events that are statistically infrequent using a large ensemble data for climate change in Japan called d4PDF and analyze the changes in return period using the abundant calculation results of sediment discharge. Our results show that the rate of increase in sediment discharge is larger than that in rainfall. Increase in heavy rainfall increases the supply of fine sediment from slope failures. When fine sediments are supplied into armored beds, the friction angle between bed materials decreases and the critical Shields number for incipient sediment motion decreases. Thus, the sediment on the riverbed will move more easily. Our results will contribute to the understanding of future landform changes and the planning of disaster prevention against climate change.
HS08-A001
Estimation of Water Demand Considering Natural, Social, and Environmental Variability
Tae-Woong KIM#+, Min Ji KIM, Jiyoung KIM, Ji-Young YOO
Hanyang University, Korea, South
Water shortage is a big challenge in the future because the global average temperature continues to increase, the drought occurrence due to climate change increases, and the availability of clean water decreases due to water pollution. To reduce future water shortage risk, it is necessary to estimate water demand in consideration of nature, social, and environmental factors. Thus, this study performed basic survey and analyses of change trends for the past water usage, and evaluated the variability and uncertainty of the water demand. We performed correlation analyses among water usage (domestic/industrial/agricultural), average temperature, precipitation, population, and water supply area (including residential, commercial, and industrial areas) in 19 districts within the Geum River basin from 1965 to 2019. Considering the correlations, enumeration models were proposed of which natural factors (precipitation, average temperature) consider non-linear relationship and social and environmental factors (water use, population, water supply area) represent a linear relationship. Based on the coefficient of determination, the enumeration models indicated that the water for industrial use accounted for 70.9%, and the water for agriculture accounted for 48.4%. Acknowledgement: This work was supported by Korea Environment Industry & Technology Institute (KEITI) through Water Management Program for Drought, funded by Korea Ministry of Environment (MOE) (No.2022003610001).
HS08-A005
Flash Droughts Identification Based on an Improved Framework and Their Contrasting Impacts on Vegetation Over the Loess Plateau, China
Shengzhi HUANG#, Xudong ZHENG+, Qiang HUANG, Lin YE, Beibei HOU, Xiaojuan ZHAO, Yifei LI
Xi'an University of Technology, China
Flash drought occurs in a short timescale and has more adverse impacts on society and ecosystems than regular drought. Considering flash drought as a special type of regular drought and identifying it by the rate of the first intensification period might ignore posterior intensification periods. To this end, we introduced the combinatorial decomposable flash drought identification framework (CDFDI) to identify flash drought from the perspective of regarding it as the subphase of drought and explore the characteristics and vegetation response of flash drought in the Loess Plateau (LP), China, where is prone to drought and its ecological environment is very fragile. The effectiveness of the framework is evaluated through the comparison analysis with a preexisting identification method proposed by Liu et al. (2020, https://doi.org/10.1175/jhm-d-19-0088.1). Results indicate that: (a) the CDFDI framework can better capture flash drought events than the Liu's method in terms of time series and spatial patterns, its rationality was further demonstrated by the obvious latitudinal pattern of correlation between flash drought and normalized difference vegetation index (NDVI); (b) the correlation shows an southeast (positive) and northwest (negative) contrasting pattern in the LP; (c) such contrasting pattern was also found in the response time of GPP, which suggests a more rapid impact on vegetation of flash drought in the arid northwestern LP; and (d) flash drought shows an exacerbating trend across the LP under the background of climate warming and mainly concentrated in the southern part. In general, this study provides new insights on flash drought connotations in a changing environment.
HS08-A007
The Decadal Changes in Drought Indicators in Indonesia from 1981 - 2020
Amalia Nafisah Rahmani IRAWAN#+, Daisuke KOMORI
Tohoku University, Japan
According to the Intergovernmental Panel on Climate Change (IPCC), the global temperature is projected to rise by around 1.5°C by 2030. This increase in temperature will result in an uneven distribution of rainfall patterns and amounts, leading to increased risk of drought disasters in certain regions. Droughts have a significant impact on water availability, both surface and groundwater, which in turn affects human activities that heavily rely on water such as domestic, industrial, and agricultural purposes. To assess droughts, numerous drought indexes have been developed, including the Standardized Precipitation Index (SPI) introduced by McKee et al. in 1993. One of the benefits of using SPI, it only requires long-term precipitation data as input and uses probability distribution and normalization to evaluate wet and dry conditions. This research used SPI-3, which is often used by many researchers to represent agricultural drought conditions, to assess various drought indicators including frequency, duration, severity, and intensity in Indonesia from 1981 – 2020. This research also focused on the change of agricultural drought indicators under changing climate that could also affect the agricultural activities. The precipitation dataset was obtained from the Multi-Source Weighted-Ensemble Precipitation (MSWEP) which provides monthly precipitation with 0.1° resolution from 1979 – present date. Based on the assessment, the drought frequency, duration, severity, and intensity tend to increase in the recent decade especially in South Sumatra and Java Island which is known as the main producer of crops. However, the worst drought event occurred in 1991 – 2000 where the precipitation was recorded as the lowest compared to the other decades. This study will be beneficial to assess the hotspot region to consider the appropriate drought mitigation and preparedness.
HS08-A008
Study on Multi-scale Drought Propagation and Its Impact on Grain Yield in the Yellow River Basin
Wenjing MAO+, Jun NIU#
China Agricultural University, China
The transition of drought signal from one type of drought to another is referred to as drought propagation. Exploring the propagation among meteorological, agricultural and hydrological drought and its potential influence factors is crucial for early warning of drought. As a case study in the Yellow River Basin (YRB), the Standardized Precipitation Index (SPI), Standardized Soil Moisture Index(SSMI) and Standardized Runoff Index (SRI) were used to represent meteorological, agricultural and hydrological drought, respectively. The Pearson correlation coefficient was used to explore the propagation time of meteorological to agricultural and hydrological drought. The run theory is applied to identify drought events and match both types of drought events. The copula-based conditional probability distribution and Bayesian network probabilistic model were used to constructs drought propagation index. Then, an integrated risk assessment framework based on drought propagation characteristics and socio-economic impact was established to assess drought propagation risk. And the drought-induced yield loss rate was analyzed.
HS08-A012
A Multimodel Assessment of Climate Change Impacts on Hydrological Drought Over Hanjiang River Basin, China
CHAO DAI#+, Zhu HAORAN
Sun Yat-sen University, China
Drought has become one of the natural disasters affecting the water ecosystems in many basins around the world, and the situation may become more severe under the impact of climate change. For better adaptation planning, this study proposes a drought assessment framework integrating downscaling method, hydrological model, drought index and statistic frequency analysis, and applies it to explore the changes in drought characteristics from the past to the future in the Hanjiang River basin of South China. First, a hydrological model of this basin was constructed and the hydrological parameters were calibrated. Then, the standardized runoff index (SRI) was used to define the hydrological drought based on the runoff data simulated by the hydrological simulation. Then, the spatial and temporal distributions of drought duration and severity are calculated. To address the effect of climate change, similar calculation process was applied to the future climate data, which was downscaled using delta change method from 10 general circulation models (GCMs) of Coupled Model Intercomparison Project Phase 6 (CMIP6). The results of the study provide useful information for water resource authorities interested in developing effective long-term drought management adaptation strategies.
HS08-A014
Assessment of Groundwater Recharge and Ternary Mixing in a Small Watershed Using Natural Tracers in Daejeon, Korea
Hanna CHOI1+, Chung-Mo LEE2, Shim BYOUNG OHAN1#
1Korea Institute of Geoscience and Mineral Resources, Korea, South, 2Pusan National University, Korea, South
The estimation of groundwater recharge and hydrochemical changes is necessary to long-term management of water resource and the understanding of hydrologic water balance. We investigated the hydrochemical mixing among rainwater, groundwater, and surface water under the given hydrological condition in a watershed boundary of Yuseong region, Daejeon in South Korea. To identify the mixing ratio among different water bodies of the catchment, hydrochemical analysis with tracers of chloride and stable isotope were performed. Ion composition indicates this watershed is mainly influenced by precipitation recharge in the mountain areas. The groundwater recharge rate in this site was calculated as about 20% of total precipitation by the GIS application with the water budget method. According to the calculated mixing ratios from tracer analysis, the groundwater hydrochemistry in this site is affected by water-rock interaction but it is also reflected the impact on small amount of untreated domestic effluent. Comprehensive interpretations of the recharge rate and surface water-groundwater mixing will be useful for estimating hydrological water balance in small mountainous catchments.
HS08-A016
Comprehensive Evaluation of Hydrological Models for Climate Change Impact Assessment
Shanshan WEN#+
Anhui Normal University, China
Climate change has substantial impacts on regional hydrology in the major river basins. To figure out such latent hydrological impacts of changing climate, more reliable hydrological simulations are imperative. In this study, we evaluated the impacts of climate change on the hydrological regime in the Upper Yangtze River Basin based on four downscaled and bias-corrected Global Climate Model outputs from Coupled Model Intercomparison Project Phase 5 under four Representative Concentration Pathways (RCP2.6, RCP4.5, RCP6.0, and RCP8.5) driving three hydrological models. Two model evaluation approaches were applied: simple and comprehensive. The comprehensive approach was used to evaluate models in the historical period, optimizing objective function at four gauges, and hydrological models were weighted for impact assessment based on their performance. In such a way, projected streamflow time series are obtained under different emission scenarios. Results show that the annual average discharge is projected to increase by 4.1–10.5% under the RCP scenarios at the end of twenty-first century relative to the reference period (1970–1999). Moreover, the high flow is projected to increase and the low flow to decrease indicating a higher probability of flood and drought occurrence in the basin. The severity of floods and droughts may increase. In comparison with the simple one-site model evaluation approach, the comprehensive method reveals that the anticipated extreme flow events would be less severe, and annual mean discharge slightly lower. The projected results imply that the application of the comprehensive model evaluation approach could narrow the simulated spreads of projections significantly, and might provide more credible results.
HS08-A017
Influence of Agricultural Irrigation on the Regional Groundwater System
Yi Hsuan HUANG#+, Ko Li LIU, Kai Wen LIN, Ray Shyan WU
National Central University, Taiwan
Agricultural water accounts for more than 70% of Taiwan's total water consumption, so there are often doubts about excessive water consumption. In recent years, studies have mentioned that about 40% of irrigation water will return to groundwater, and groundwater resources have gradually become an important water supply. The Tainan area has a relatively mature irrigation system. The irrigation system in the Kaohsiung area is rather incomplete. During the dry season, agricultural water is often unable to provide enough water due to insufficient water, resulting in an imbalance between the supply and demand of water resources, leading some areas to supplement water demand and over-extract groundwater. In this study, the system dynamics model - VENSIM is used to establish the correlation model between the reservoir river system and groundwater. The hydrological data of several years are used to analyze the adequate rainfall and irrigation water demand, and to explore the impact of agricultural water use on the groundwater level, to understand the agricultural water consumption. The amount available for dispatch and the best reasonable use amount.
HS08-A018
The Hydrological Impact of Climate Variability and Forest Disturbance in Stellako Watershed of Canada
Zipei LIU+, Mingfang ZHANG#, Shiyu DENG
University of Electronic Science and Technology of China, China
Climate variability and forest disturbance are commonly recognized as critical driving factors significantly affect the regional hydrology in large-scale forested watersheds. Yet, due to the watershed landscape heterogeneities (e.g., topography, soil characteristics, climate conditions, and vegetation types), hydrological responses to climate and forest changes and associated mechanisms have not been fully understood. In addition, distinguishing the hydrological effects of forest change, climate variability and other factors in a large watershed efficiently and accurately, remains a challenge. In this study, we combined the modified double mass curve (MDMC), Autoregressive Integrated Moving Average (ARIMA) intervention, and multivariate ARIMA to assess the annual streamflow affected by climate variability and forest disturbance in the forested Stellako watershed, a typical forest-disturbed area in Canada. The study period was from 1951 to 2018. The key findings are: (1) the hydrological environment was significant influence by cumulative external disturbances after 1980, referring to the 1951-1979 period the annual runoff decreased by 38.65 mm, (2) from 1980 to 2018, the streamflow decreased by 14.69 and 24.75 mm due to climate and forest changes, respectively, (3) the annual runoff variation was mainly attributed to forest disturbances contributing 42.42% of the total variations. The developed methodology can be applied to quantify the disturbance effects at a watershed or regional scale and develop watershed and forest management strategies under future climate and forest changes.
HS10-A007
Comparative Analysis of One Parameter Hydrological Model on Watershed in Republic of Korea
Heemin KO1+, Hyunuk AN1#, Seungjun LEE2, Jiyoung JUNG3
1Chungnam National University, Korea, South, 2Korea Institute of Geoscience and Mineral Resources, Korea, South, 3K-water, Korea, South
Agricultural reservoirs supply water for various purposes such as irrigation, maintenance, and living. Since agricultural reservoirs respond sensitively to seasonal and climate changes, it is essential to estimate supply and inflow for efficient operation, and water management should be done based on these data. However, in the case of agricultural reservoirs, the measurement of supply and inflow is relatively insufficient compared to multi-purpose dams, and inflow-supply analysis in agricultural reservoirs through water balance analysis is necessary for efficient water management. Therefore, rainfall-runoff analysis models such as ONE model and Tank model have been developed and used for reservoir water balance analysis, but the applicability analysis for ungauged watersheds is insufficient. The ONE model is designed for daily runoff calculation, and the model has one parameter, which is advantageous for calibration and ungauged watershed analysis. In this study, the water balance was analyzed through the ONE model and the Tank model for 15 watersheds upstream of dams, and R2 and NSE were used to quantitatively compare the performance of the two models. The simulation results show that the ONE model is suitable for predicting the inflow of agricultural reservoirs with the ungauged watershed. This work was supported by Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry(IPET) through Agricultural Foundation and Disaster Response Technology Development Program (or Project), funded by Ministry of Agriculture, Food and Rural Affairs(MAFRA)(321071-3).
HS10-A008
Impact of Acoustic Waves on Rainfall Distribution in Acoustics-induced Artificial Rainfall Technology
Mengyao WANG1#+, Ji CHEN1, Jiaye LI2, Jinzhao WANG3
1The University of Hong Kong, Hong Kong SAR, 2Dongguan University of Technology, China, 3Qinghai University, China
As a potentially effective method for increasing water resources, the acoustics-induced artificial technology has attracted wide attention for the characteristics of eco-friendly and low-cost. In this study, a non-randomized acoustic rainfall field test was carried out in the Tibetan Plateau from May 18, 2020, to June 19, 2020. The rainfall data were collected by ground-based tipping bucket rain gauges. Various classification criteria were applied to these rain gauges to analyze the acoustic impact on rainfall distribution. The results showed that the natural rainfall distribution in the experimental base is highly related to the cloud condition and terrain. The overall rainfall was more concentrated in the east. While with the influence of acoustic waves, the rainfall center has shifted to the west region during the rainfall events with the acoustic operation. This phenomenon may be caused by the combined effect of acoustic field and near-surface convection. Compared with the natural rainfall process, the long-duration rainfall process under acoustic fields has an apparent two-stage pattern. The rainfall intensity is much heavier in the central region (near the acoustic operation point) than on either side during the first stage, lasting less than one hour. This phenomenon may be attributed to the trigger effect of acoustic waves, which has accelerated the forming process of large droplets. While rainfall in the second stage usually lasts for hours with random distribution. The impact of acoustic waves on the growth of relatively small particles may not be reflected in the rainfall distribution due to the complex cloud dynamics.
HS10-A011
Analysis of the Effect of Design Rainfall Overrun Duration on Drainage System
Seok Hwan HWANG#+, Jungsoo YOON, Narae KANG
Korea Institute of Civil Engineering and Building Technology, Korea, South
On August 8, 2022, torrential rain of more than 100 to 300 mm per day fell in the Seoul, Incheon, and Gyeonggi metropolitan areas and Gangwon of KOREA, causing flooding of roads, houses, and vehicles in various places. Overall, the southern area of Seoul recorded more than 90 mm of precipitation per hour. At around 9:00 pm on the 8th, the maximum one-hour precipitation of 141.5mm was recorded at the Korea Meteorological Administration branch. The maximum daily rainfall also recorded 435.0mm/day (2022. 8. 9, 12:17) at the operating point, exceeding the all-time high of 354.7mm (1920. 8. 2.). It exceeded 350 mm in most of the Gangnam area of Seoul. And Gangnam, Seocho, and Korea Meteorological Administration (Sindaebang) points where precipitation was concentrated exceeded the 200-year frequency for up to 6 hours of rainfall duration. However, it is insufficient to judge the magnitude of the heavy rain that caused flood damage this time only by the frequency of rainfall. Compared to large-scale inundation and heavy rain events that have occurred since 2000, the instantaneous rainfall intensity was not record-breaking. However, it is characterized by the fact that the rain of strong rainfall intensity exceeding the design capacity continued continuously for 3 hours. Therefore, in this study, considering the duration exceeding the frequency as well as the frequency of precipitation, we analyzed the degree of effect on the performance of the drainage system according to the duration compared to the past cases. Acknowledgment: This research was supported by a grant(2022-MOIS61-002) of ‘Development Risk Prediction Technology of Storm and Flood for Climate Change based on Artificial Intelligence’ funded by Ministry of Interior and Safety(MOIS, Korea).
HS11-A001
Development of Observational Data Collecting System for Urban Flood Analysis
GyeongHyeon KIM+, BonHyun KOO, TaeYoung HAM, KyuCheoul SHIM#
JBT Corporation, Korea, South
This study presents various observational data collecting module to use collected data as input data in urban flood analysis model. Various institutions provide various formats of data such as XML, JSON, CSV, SHP, etc. We established different collection processes according to the format. Urban flood data collecting module is a web platform which automatically collecting 33 kinds of data for analyze rivers from K-water, Korea Meteorological Administration, Han River Flood Control Office, etc. using representational state transfer application programming interface and Linux crontab. Urban flood data collecting module provides quasi-real-time data collection and collection status information. Development of urban flood data collecting module is first part of 5 years research urban flood meta-solution. Based on the urban flood data collecting module, we are planning to import urban flood analysis model on the meta-solution platform and use collected data for input data. This work was supported by Korea Environment Industry & Technology Institute (KEITI) through R&D Program for Innovative Flood Protection Technologies against Climate Crisis Program (or Project), funded by Korea Ministry of Environment (MOE) (2022003470001).
HS11-A007
Characteristic of Regional Groundwater Flow System: Case Modeling Study in Longzici Karst Spring Area, North China
Xiaojuan QIAO1,2#+, Yu CHENG1, Dawei WANG1
1University of Chinese Academy of Sciences, China, 2Chinese Academy of Sciences, China
Karst spring water dynamic characteristics and its response to atmospheric precipitation are of great significance for water resources utilization under the background of climate change. This paper selects Longzici spring area, North China, as the study area. Based on a long series of spring water flow and precipitation data, the dynamic characteristics of spring flow was analyzed and the numerical simulation of the groundwater flow model was established. The results shows that the groundwater kept the sustained decline over the past decades which is in a negative equilibrium state, with a storage variable of -2.26 million m³/year. The sensitivity of spring flow to precipitation under different precipitation scenarios shows that the water level changes in the recharge and drainage areas are similar about (3-5cm) and slightly larger than that in the runoff area(1.5cm) when minimum rainfall (287.24 mm) happens. When the precipitation is at its maximum (867.66 mm), the water level change in the runoff area can reach 95 cm which is much larger than those in the recharge and discharge areas. The results indicates that Longzici karst spring has a relatively good regulation water resource capacity and the runoff area is more sensitive which plays an important role in response to climate change.
HS11-A013
Isolation and Characterisation of Bacterial Species for the Bioremediation of Synthetic Dyes in Wastewater
Priscilla S. K. LEUNG+, Kung Ming LEUNG, Grace LAI, Simon GRIFFIN#
The ISF Academy, Hong Kong SAR
Discharged effluent from textile dyeing is a major pollution concern for urban surface water as well as groundwater. While persistence and chemical stability may be desirable qualities for dyeing, the same properties make for a detrimental and unsustainable environmental impact. As the world’s predominant supplier of textiles, pollution from dyeing and finishing is especially acute in Asia, with annual discharges of textile wastewater in China alone exceeding 1.84 billion tonnes [1, 2].
This project has sought to isolate and characterise versatile dye-degrading bacteria that might offer an energy-efficient method of remediation of textile wastewater. Samples from a stormwater drain were used to inoculate a high salt content medium (CAV) and the resulting colonies transferred to separate agar plates containing azure B, methylene blue and malachite green. After isolation, DNA extraction by Qiagen DNeasy PowerSoil Pro Kit and sequencing via Illumina and Nanopore platform, the complete genomes of three isolates with vigorous dye-decolorizing activity were established by hybrid assembly (Unicycler v0.4.8). They were identified and annotated via PATRIC-BRC as Aeromonas hydrophila subs. hydrophila strain PSKL.DP, Aeromonas dhakensis strain PSKL.DM and Pseudomonas putida strain PSKL.D1, with genome sizes 4.78, 4.82 and 5.88 Mbp respectively. Whilst all three isolates possess genes explaining their dye-decolorization activity (up to 2.5 mg/L Azure B and 1.25 mg/L methylene blue in 24hr), the presence of potential virulence and antibiotic resistance genes in PSKL.DP would preclude its use for wide scale remediation. PSKL.DM and PSKL.D1, on the other hand, appear more promising. References:
[1] R. Al-Tohamy, S. S. Ali, F. Li, et al.. Ecotoxicol. Environ. Saf., 231: 113160 (2022). [2] H. Chen, X. Yu, X. Wang, Y. He, J. Clean. Prod., 326: 129353 (2021).
HS11-A022
Patch Size Effect on a Flow Field Due to Submerged Aquatic Vegetation
Keita MATSUMURA1+, Keisuke NAKAYAMA1#, Tetsuya SHINTANI2, Hiroki MATSUMOTO3
1Kobe University, Japan, 2Tokyo Metropolitan University, Japan, 3Port and Airport Research Institute, Japan
Natural disasters have become more frequent and severe worldwide, so it is urgent to adapt and mitigate climate change. In contrast, the carbon absorbed and sequestered by ecosystems, called "Blue carbon", has attracted attention as a means of mitigating climate change. Nellemann (2009) revealed that blue carbon ecosystems, such as coastal seagrass beds, absorb atmospheric carbon dioxide. Therefore, effective carbon dioxide reduction through accurate assessment and management of the blue carbon ecosystem is desired. However, submerged aquatic vegetation (SAV) often exists in patches, creating complex flow regimes through mutual interference with the current. As a result, the carbon absorption rate is significantly affected, making accurate estimates of sequestration by blue carbon ecosystems difficult. Therefore, it is necessary to understand mass transport under such a complex flow field. Thus, this study aims to clarify the patch size and deflection effect on the hydrodynamics around SAVs using numerical simulations. The SAV numerical model was successfully used to analyze the flow around an SAV patch, with results in good agreement with laboratory experiments. Numerical results showed that when the SAV bended significantly, the higher velocities occurred above the SAV meadow, with the lower velocities at the bottom of the SAV. Additionally, when the SAV did not bend significantly, the water flow was found to go significantly around the SAV patch than in the low-elastic modulus case. As a result, it was found that the proportion of the channel width occupied by the patch was the most critical factor in controlling the flow conditions and mass transport. Additionally, deflection was also an essential factor.
HS11-A037
Rainfall-runoff-inundation Simulation Using a 1m Resolution Elevation Data Focusing on Sannomiya, Japan
Nanako INOKAWA#+, Kenichiro KOBAYASHI
Kobe University, Japan
Due to climate change, the risk of flooding is increasing also in areas where previously the risk was low. It is very important to estimate the flooding risk accurately by using high accuracy inundation model against large-scale flooding and to take measures for such as large-scale flooding. There are several inundation models developed such as Rainfall-Runoff-Inundation (RRI) model and many researchers have been considered its accuracy. Input data especially elevation data is one of the most important factors for accurate inundation analysis. In Japan, 5m high-resolution elevation data by geospatial information Authority of Japan has been widely used for inundation analysis. In this study, we examined the accuracy of inundation analysis by using the inundation model based on two-dimensional shallow water equation in Kobe, Japan using 1m resolution elevation data that is firstly published by Hyogo prefecture in Japan. As a result, inundation analysis using 1m resolution elevation data is highly accurate compared using 5m resolution elevation and accurately reflects topography also in steep areas.
HS12-A005
Evaluation the Carbon Dioxide Control Effect of Hydropower Generation Using Irrigation Reservoirs Targeting Pre-discharged Water
Atsuya IKEMOTO1#+, So KAZAMA1, Takeo YOSHIDA2
1Tohoku University, Japan, 2National Agriculture and Food Research Organization, Japan
The ultimate objective of this study is to evaluate the effectiveness of hydropower generation by irrigation reservoirs. To achieve the ultimate objective, as a first step, this paper examines factors that influences electric-generating capacity by prior releasing at irrigation reservoirs. This study also attempted to discuss effect of control on the discharge of carbon dioxide. As a result, it was estimated that a 3-day pre-discharge to reduce the reservoir storage volume to zero would reduce carbon dioxide emissions by 156 t-CO2. In addition, electric-generating capacity which is generated prior releasing discharge at irrigation reservoirs set in this study throughout Japan is estimated about 0.2%. Each electric-generating capacity is thought of as depends not storage of irrigation reservoirs but also reservoirs height. So this study focuses on storage capacity and reservoirs height, and attempts to examine the relationship between irrigation reservoir’s storage or height and electric-generating capacity by prior releasing by prefectures. The higher the storage capacity per reservoir, the higher the power output. The higher the height per reservoir, the higher the power output.
HS12-A006
Relationship Between Population Change and Regional Characteristics Caused by Flood Damage
Ayaka OKAMOTO#+, So KAZAMA, Hayata YANAGIHARA, Yusuke HIRAGA
Tohoku University, Japan
Relationship between population change and population density was investigated in term of the occurrences of flooding. The target areas for the study were municipalities in which the proportion of damaged buildings to the total number of buildings was 10% or greater between the years 2011 and 2020. The flood damage was defined as the damage caused by the breakage of embankments, overflow of embankments and non-embankment areas, pluvial flooding, and water storage water in depressions. The population change resulting from flood disasters was calculated utilizing actual population data obtained from the Basic Resident Register. The rate of population change due to flood disasters was estimated by subtracting the estimated population in the non-flooding from the actual population. The estimated population in the non-flooding was determined based on the actual population data obtained in the six years after the flood event. The findings revealed a correlation between the rate of population loss due to flooding and low population density, as well as a correlation between the rate of population growth and high population density. Additionally, the impact of different types of building damage on population loss was evaluated in small cities (population less than 100,000), medium cities (population between 100,000 and 500,000), and large cities (population over 500,000). The results showed that in small cities, even in cases where a significant number of houses were inundated or partially and totally destroyed, there was no tendency for population changes. However, in medium-sized cities, people tended to migrate to areas with building damage in cases of both inundation and partial/total destruction. In contrast, in large cities, the damage to buildings had a limited effect on population migration.
HS12-A009
Consideration of the Best Way of Desalination of Salinity Accumulation Soil in Mekong Delta
Aoi TAKAHASHI#+
Sendai Nika Junior & Senior High School, Japan
Salt damage is currently occurring in Mekong Delta, which causes failure of the cultivation of crop and thus resulting in a heavy economic damage. In general, it takes about three months for rain to wash away the salt in the soil. My objective was to find the best way of desalting which can shorten the time to reduce the salt. Small-scale industrial farmers cannot afford neither purchasing an expensive drainage equipment nor using a large amount of water, which is the standard way of desalting. Therefore, developing less expensive way to reduce the salt is required. Based on previous studies, the three different methods were considered the practical alternatives; mixing compost which contains Haemophiles in the salted soil, disseminating calcareous materials, using phytoremediation of salt tolerant plants. First, the salt-damaged soil was made by sprinkling 3 wt. % of brine. Next, the soil was put into 10 flowerpots and divide each two of them into the following five groups; (1) mix halophilic bacteria contained compost, (2) disseminate calcareous materials, (3) implant sorghum, (4) implant chard, and (5) do nothing special. The water, which amount was determined with reference to precipitation of Cà Mau province, were given to these pots, and the salinity was measured once a week. The average salinity of soil in Group 1 and Group 2 was significantly reduced than that of Group 5. Sorghum in Group 3 and chard in Group 4 were withered. The approximate period until the salinity of the soil reaches 0% was about 60 days in Group 1 and 58 days in Group 2, while 76 days in Group 5. These results suggest that contained compost and disseminate calcareous materials were effective to desalt the salinity accumulation soil and that those desalting ways would be helpful as less expensive option in Mekong delta.
HS12-A010
Algorithm Development for Precipitation Estimation by Image Segmentation Model Using Meteorological Satellite Images
Kansei FUJIMOTO#+, Taichi TEBAKARI
Chuo University, Japan
With climate change becoming more severe in recent years due to global warming and other factors, accurate precipitation data from meteorological satellites is expected to play an important role in disaster prevention and agriculture in regions where ground rain gauges and radar rain gauges are not fully deployed. Recently, many deep learning models have been developed, among which image segmentation models are useful for precipitation estimation from meteorological satellite images. This study aims to develop an algorithm that can estimate precipitation more accurately from weather satellite IR bands using multiple image segmentation models. Many image segmentation models for deep learning CNNs have been developed from around 2015 to the present. Among them, we select a model that excels in precisely discriminating rainfall areas and estimating precipitation intensity using IR band brightness temperature information, latitude and longitude, and elevation data. We also extract features from the IR band as training data, aiming for a model with high generalization performance. The satellite data used was the Himawari elevation data. In addition to the brightness temperature information, latitude, longitude, and elevation data were provided for the training data. The National Synthetic Radar GPV was used as the teacher data. The spatial resolution of the Sunflower standard data is 2 km. The satellite observations used for the training data and the radar images used for the teacher data have different observation targets: cloud particles and raindrops, respectively. Therefore, the observed brightness temperatures and precipitation intensities do not always agree with the peak positions. The training and teacher data are varied from 2 km to 10 km at 2 km intervals to see which estimation results are more reasonable. The results showed an improvement in the accuracy of precipitation estimation compared to nonparametric regression.
HS12-A011
Applicability of Excess Probable Rainfall Using Radar Rainfall for Watershed Management
Shihori OHASHI#+, Taichi TEBAKARI
Chuo University, Japan
Although Japan's meteorological radar systems are currently well equipped in both space and time, the data are rarely used for analysis of past phenomena other than disaster investigation. Considering the cost of operating ground rain gauges in the future, it is necessary to consider the possibility of replacing radar rainfall observation with ground. In this study, we examined the applicability of radar rainfall to watershed management by comparing excess probable rainfall between radar and ground rainfall data. The radar rainfall is used from Synthetic Radar GPV (2006-2022), and the ground rainfall is from Water Information System (MLIT) and AMeDAS (JMA) (1976-2022). The target area was the upstream from each reference point of the Tone, Watarase, Kinu, Kokai, Ara, Tama, Tsurumi, Sagami, Naka and Kuji Rivers flowing through the metropolitan area of Japan. We calculated the annual maximum basin average rainfall per planned rainfall duration (2 or 3 days) and the probability rainfall using Gumbel and GEV distributions of both radar and ground rainfall for the period 2006-2022 (Pattern A) and of radar rainfall for the period 2006-2022 and ground rainfall for 1976-2022 (Pattern B). We compared the rainfall probabilities calculated from radar and ground rainfall. As a result, the comparison of rainfall probabilities calculated from radar and ground rainfall using the GEV distribution showed that in Pattern A, the difference between radar and ground rainfall was generally within a range of ±20% for all basins except the Tama River. On the other hand, in Pattern B, the larger probability rainfall, the more the ground rainfall tended to be underestimated to radar. By adjusting the sample sizes of radar and ground rainfall, the calculated probability rainfall was found to have a generally similar trend. Consequently, radar rainfall may be applicable to using for watershed management.
HS12-A013
Projections of Future Flood Damage Cost and Evaluation of Adaptation Measures in River Basins of Toyama Prefecture, Japan
Shuichi KURE#+, Daichi KIKUCHI, Ryuto FUJISHITA
Toyama Prefectural University, Japan
In recent years, water disasters have become more frequent due to global warming, and basin flood control has been promoted to mitigate the damage, and several adaptation measures have been considered for flood damage reduction. However, the comparison of adaptation measures in different river basins and the feasibility of adaptation measures with mitigation effects to achieve a decarbonized society is not discussed. Therefore, this study proposes the most appropriate adaptation measures for five rivers in Toyama Prefecture, Japan by projecting the amount of future flood damage cost and conducting a quantitative evaluation of several adaptation measures. Therefore, flood damages are estimated from rainfall-runoff and flood inundation simulations under changing climates. For adaptation measures, vegetation management in rivers, rice paddy field dams, a concrete dam reservoir, green infrastructure, and forest conservation management were evaluated in this study. From the results of the analysis, the potential for paddy field dams, vegetation management, and green infrastructure shows a greater effect than a grey infrastructure at the Oyabe River.
HS12-A018
Regional Scale Water Footprint Based Agricultural Water Security Assessment
T. R. SREESHNA#+, Athira P
Indian Institute of Technology Palakkad, India
Climate change causes a significant impact on water availability and crop yield, which in turn are governing factors for ensuring water security in an agrarian region. The current study analyses the impact of climate change on water security in the command area of a multipurpose reservoir in Kerala, India. An integrated modelling framework considering SWAT hydrological model and DSSAT CERES rice model has been utilized for quantifying the water footprint and analyzing the water security on a regional scale for kharif and rabi season. The study considers the major role of reservoirs and the relevance of management practices in the region for water security assessment. The green water and blue water use in the study area has been estimated using the SWAT hydrological model, while the crop yield has been estimated for the short-span rice cultivar, Jyothi, using the DSSAT CERES rice model. The climate change signals are accounted in the study by considering three CMIP6 GCMs under two scenarios of shared socioeconomic pathways, SSP245 and SSP585. The regional agricultural water security under the changing climate is accounted by the green and blue water footprints as an indicator. An increasing trend of water footprint was observed towards the future, thus paving a path to a water insecure future. The study indicates the importance of developing adaptation policies on a regional scale.
HS12-A019
Evaluation of the Impact of Changes in Domestic Wastewater Treatment Methods on the Nitrogen Load Discharged from the Kurobe River to Toyama Bay
Matsuura TAKUYA1#+, Taichi TEBAKARI2
1University of Yamanashi, Japan, 2Chuo University, Japan
In Japan, the nitrogen load in closed sea areas such as Tokyo Bay, Ise Bay, and the Seto Inland Sea has been decreasing year by year, and the decrease in fish catches and the discoloration of cultivated algae such as seaweed and wakame (seaweed) are emerging as social and economic problems. In Toyama Bay, the target area of this study, it has been reported that the nitrogen load is decreasing year by year due to the improvement of wastewater treatment capacity as a result of changes in the domestic wastewater treatment system. The purpose of this study is to clarify the effect of changes in domestic wastewater treatment on the nitrogen load discharged from the Kurobe River to Toyama Bay. The precipitation, temperature, and solar radiation used in this study are the Japanese bias-corrected climate scenario data set based on the CMIP6 CDFDM method. In this study, the analysis was conducted for the period 1987-2014, when observation and scenario data are available. The spatial and temporal resolutions are 1 km and 1 day, respectively. The tank model was used as the effluent model, and the intensity method was used to calculate the total nitrogen (TN) emission load. In this study, TN sources were divided into areal and point sources. As a result, the pollution load from public sewage systems has increased, while the use of stand-alone septic tanks has decreased. As a result of a 76% increase in the sewage treatment population coverage from 1987 to 2014, the nitrogen load discharged from the Kurobe River watershed into Toyama Bay decreased by 8 % (76 kg/day) over a 30-year period.
HS13-A002
Effect of Land Use Land Cover Changes on the Water Balance Components of the Glacier-fed Mountainous Watershed: Assessment Using Fully Distributed Hydrological Model
Kavya M#, Sanjeev Kumar JHA+, Ankit SINGH
Indian Institute of Science Education and Research Bhopal, India
Land use and land cover patterns have a significant impact on the hydrology of a watershed. The mountainous watersheds have varying land classes with changes in elevation. The increasing anthropogenic activities also lead to changes in the aerial extent of different land classes. The highly variable topography, intricate river networks, and occasionally the presence of snow and glaciers limit the semi-distributed hydrological models to capture the physical processes in the Himalayan region fully. This study aims to quantify the hydrological response of a glacier-fed mountainous region with changes in land use and land cover. The fully distributed hydrological model WATFLOOD is used for stimulating the hydrological processes at the Alakananda River basin in the Western Himalayan region. Considering the data scarcity in the Himalayan region, the model is calibrated using reanalysis data from ERA-5. The land use land cover maps from 2005 to 2015 are used to set up the model. The entire basin is divided into seven sub-basins based on the discharge sites and land use types. The rainfall and temperature data from ERA-5 are used as input to WATFLOOD to calculate the runoff at the outlet of each sub-basins. The water balance components are evaluated across eleven land-use classes at multiple locations in the study area. The results show that the WATFLOOD model can accurately simulate the water balance in the Himalayan region. The developed hydrological model can be a potential tool for the management of mountainous watersheds.
HS14-A002
Delineation of Saltwater Intrusion to Exploit Freshwater in the Coastal Vietnamese Mekong Delta: Empirical Evidences in Co Chien Estuary
Duc Dung TRAN1,2#+, Thuc PHAM THI BICH3, Edward PARK2, Nam NGUYEN TRUNG4, Vu TRUONG NGUYEN3, Man DUONG BA3
1National Institute of Education and Earth Observatory of Singapore, Singapore, 2Nanyang Technological University, Singapore, 3Vietnam Academy of Science and Technology, Viet Nam, 4Ministry of Agriculture and Rural Development, Viet Nam
In the Vietnamese Mekong Delta, saltwater intrusion reduces freshwater resources for agricultural and domestic use in coastal areas, causing difficulties in multi-scale socio-economic development. Our study analyses salinity monitoring data from 1996-2020 and applied a 1-dimensional coupled with 3-dimensional model to determine saline-intrusion boundaries along the Co Chien river of Ben Tre province under the severe salinity year of 2016 and forecast to 2030. The findings show that the freshwater exploitability at 0.3g/l salinity is complicated along the Co Chien river, particularly for 3 to 6 months in the dry season at 28km to 5.29km from the river mouth. For the freshwater at 4g/l salinity, the exploitation time is sufficient at 25-28km; however, the difficulty from 1 to 3 months is found at the location 17km to the river mouth. Generally, the salinity pattern is stratified at the beginning and the end of the dry season but evenly mixed in the middle. Cross-sectional analysis shows freshwater layering when the tide recedes to a depth of 3m. Freshwater resources decrease with the frequencies of 50%, 75%, 85%, and 95% along the river, causing high salinity intrusion and deep water intrusion, while the salinity 0.3g/l does not occur in the case of super-depleted water of 85% and 95% probability) and 4g/l salinity penetrates 90% of Ben Tre province. The future forecast shows that salinity will intrude 10-15km further than that in the current condition. We propose active water storage reservoirs along the main rivers, consistent operation of water infrastructure systems and effective water distribution and exploitation, crop pattern change, and people awareness raising to exploit freshwater resources to adapt to saline intrusion driven by climate change. Our findings provide a lesson learned for similar worldwide deltas where freshwater is scarce due to salinity intrusion.
HS14-A003
The Integration Technology of Wind Warning and Application During Typhoons Affecting Taiwan
Chieh-Ju WANG#+, Dan Rong CHEN, Hsin-Hung LIN, Yi-Chiang YU
National Science and Technology Center for Disaster Reduction, Taiwan
Taiwan is threatened by typhoons in summer and autumn, and there is a high risk of wind disasters. However, the wind speed simulated by the model is overestimated for the average wind and underestimated for the peak gust. Therefore, it is necessary to correct the error of the model before using the modeled wind data for wind warning. In order to improve the accuracy of wind forecasting, this study applies lots research results from academic community, such as feature analysis for observation and forecasting, and also further establishes statistical models and dynamic statistical correction methods, etc. At last, it integrates all technologies and develops a wind warning system for typhoon disaster response. In order to understand the climate characteristics of wind observations, feature classification and statistical analysis were carried out for the historical wind direction and wind speed of each station in Taiwan. Also, a gust factor database was built for 503 stations in Taiwan by using the characteristic statistical method of gust factor. This database is used as the calculation index of forecast wind speed conversion and forecast gust. In addition, the past ensemble forecast wind data database is also analyzed to understand the error distribution and systematic error causes of numerical weather prediction models in wind speed forecasting, and try to carry out regression correction and effect evaluation of different methods. Finally, technologies such as gust factor, ensemble forecast, regression correction method and typhoon path correction method are integrated, and are applied to the wind warning during typhoons affecting Taiwan.
HS14-A004
Risk Assessment and Real-time Warning System Development of Hillslope Disaster in Mountainous Indigenous Villages
Jui-Yi HO#+, YuTing WANG, Che-Hsin LIU, Wei-Bo CHEN, Chih-Hsin CHANG
National Science and Technology Center for Disaster Reduction, Taiwan
This study proposes the risk assessment method for hill tribes by field disaster environmental survey. The field investigation of 558 indigenous tribes in Taiwan was based on four items that include indigenous village potential (IVP), indigenous village symptom (IVS), Indigenous village magnitude (IVM), and Indigenous village traffic (IVT). The Nature Break method is used to classify the risk of the hillslope disaster. There are 27 high-potential hillslope disaster areas were selected as the demonstrated areas to develop the real-time warning system. To increase the disaster lead time, this study combined Shallow landslide prediction based on the Infinite slope Model and TOPMODEL (SIMTOP) with the Precipitation Ensemble forecasts to construct a comprehensive real-time shallow landslide warning system for study areas. The results of this study reveal excellent predictive performance in terms of the time of occurrence landslides in all study areas. The proposed model has the potential for application in landslide early warning systems to reduce loss of life and property.
HS14-A005
Analysis on Large-scale Landslide Occurrence - A Case Study for Hu-Hu-Lun Area
Yu-Ching LIN+, Jui-Yi HO#, Chiao-Yin LU, Che-Hsin LIU, Shih-Chiang LEE, Chih-Hsin CHANG
National Science and Technology Center for Disaster Reduction, Taiwan
Taiwan is prone to hillslope disaster in mountain areas because of its special topographical, geological, and hydrological conditions. Up to 9,848 large-scale landslides potential areas had been delineated based on the landslide micro-topography. Consequently, Soil and Water Conservation Bureau in Taiwan make a large-scale landslide prevention and response operation plan. The 269 large-scale landslide potential areas in Taiwan with high risk and protected objects had been selected to predict the large-scale landslide occurrence. Although the large-scale landslide is the rare event, one of large-scale landslide potential areas, namely Hu-Hu-Lun area (number: D003), occurred deep-seated landslide caused by the heavy rainfall during Typhoon NESAT in October 2022.In this study, the airborne Lidar with unmanned aircraft system was used to generate the digital elevation model (DEM) to provide the surface information such as the scope of the landslide, the historical cliff, and the old forest road. The results indicated the maximum elevation change of the landslide and the accumulation area are decreasing 26.1 m and increasing 22 m respectively. In addition, 180 frames (from 2019 to 2021) of down-orbit synthetic aperture radar images (SAR) were analyzed by permanent scatterer radar interferometry (PSInSAR). The long-term submersible phenomenon in the landslide crown and the landslide area has obvious deformation in the second half of 2021 from the monitoring results. The analysis results are good agreement with in situ monitoring. It is promising to apply the proposed method for subsequent disaster response research and application.
HS14-A006
Exploring the Use of Single Image Super-resolution Techniques for Enhancing GCM Rainfall Data in Taiwan
Chou-Chun CHIANG1+, Li-Huan HSU1#, Jung-Lien CHU1, Kuan-Ling LIN1, Li-Rung HWANG1, Hsin-Hung LIN1, Chieh-Ju WANG1, Yi-Chiang YU1, Chin-Shyurng FAHN2
1National Science and Technology Center for Disaster Reduction, Taiwan, 2National Taiwan University of Science and Technology, Taiwan
This study develops a downscaling technique for global circulation model (GCM) rainfall data using the Multi-Scale Residual Network (MSRN) algorithm, which is a deep learning algorithm for image super-resolution problems. The GCM rainfall data with a resolution of 0.25 degrees is increased 20 times to 0.0125-degree high-resolution grid rainfall data covering Taiwan. The technique consists of two MSRN modules that increase the resolution by 4 times and 5 times, respectively, in a hierarchical concatenation. The results of the verification of the test data show that the MSRN module can modify the rainfall distribution towards higher values and outperforms the linear interpolation method for daily rainfall thresholds less than 500 mm. Four sets of global model daily rainfall forecast downscaling products were tested from August 28th to November 30th, 2022, including the ECMWF deterministic forecast, the ECMWF ensemble forecast with 51 ensemble members, the MPAS deterministic forecast, and the JMA deterministic forecast. The verification results show that MSRN improves the rainfall forecast results for the four different model datasets, with significant improvement in the threat score and true positive rate for rainfall thresholds from 40 to 200 mm. However, the results also indicate that MSRN tends to overestimate higher rainfall thresholds and leads to higher false positive rates.
HS14-A008
Inundation Analysis of Farmlands Area Using 2D Inundation Model K-flood
Inhyoek SONG+, Hyunuk AN#, Hee Sung LIM
Chungnam National University, Korea, South
The frequency of heavy rains is increasing due to climate change. In Republic of Korea, the average annual rainfall has increased over the past 30 years, while the number of rainy days decreased, which means increasing rainfall intensity. In particular, despite of its importance for food production, farmland areas suffer great damage every year due to relatively insufficient preparedness and mitigation measures compared to urban areas or residential areas. In Korea, because the maintenance for main river is relatively well established, and farmland inundation is often caused by insufficient drainage capacity. However, flood analysis on farmland is still insufficient. In this study, flood analysis was conducted using K-Flood to analyze the causes of flooding in farmland areas and to reduce flood damage. K-Flood is a two-dimensional flood inundation analysis model developed by this research team that can simulate flooding in two dimensions in the target area to be analyzed. Farmland near the Shindae drainage plant in Mihocheon, Cheongju-si, Chungcheongbuk-do was selected as the target site, and the flood that occurred on July 14-16, 2017 was selected as the target event. Rainfall data and DEM data from Cheongju and Ochang were used for flood analysis. The flooded area simulated by K-Flood and the reported flooded area were compared, and the cause and progress of the flood were analyzed. This work was supported by Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) through Agricultural Foundation and Disaster Response Technology Development Program (or Project), funded by Ministry of Agriculture, Food and Rural Affairs (MAFRA) (321071-3)
HS14-A011
Improvement and Uncertainty Analysis of Streamflow Prediction Using Lumped-hydrologic Modeling and Ensemble-based Data Assimilation
Garim LEE+, Bomi KIM, Songhee LEE, Seong Jin NOH#
Kumoh National Institute of Technology, Korea, South
Accurate prediction of streamflow is essential for water resource management and disaster mitigation. However, under changing climate and environment, the conventional optimization schemes have become more uncertain and vulnerable since stationary features or parameters of a catchment might change over time. Hydrological data assimilation (DA) is a method that can improve predictive accuracy by considering the uncertainty of hydrological models, updating the states or parameters of a hydrologic model to produce more reliable estimates of the initial conditions and parameters. In this study, the two ensemble-based sequential DA techniques, ensemble Kalman filter and particle filter were analyzed for the streamflow predictions by a lumped hydrologic model using airGRdatassim. In addition, we assessed the effect of DA-related hyper-parameters on the simulation performance. Multiple numerical experiments were implemented for the Yongdam Dam catchment in South Korea. As expected, the accuracy of the daily streamflow simulation was improved by ensemble-based sequential DA while limited performance was found for high-flow simulation. We discuss the impacts of and hyper-parameters such as input forcings uncertainty and updating schemes on the performance and ensemble distributions. Also, feasibility of further improving DA such as increasing temporal resolution and adding new post-processing schemes will be discussed.
HS14-A012
Effects of Sample Volume on Microplastics Occurrence in Groundwater: A Case Study in Haean, Korea
Jihye CHA+, Jin-Yong LEE#
Kangwon National University, Korea, South
Microplastics, defined as particles less than 5 mm in size, have become a global environmental concern due to their widespread presence in the environment and potential harmful impacts on humans. Accurate quantification of microplastics is crucial to understand the extent of the problem and to evaluate the effectiveness of managing strategies. Sample volume is one of the key factors that can affect the detection and quantification of microplastics, and therefore should be carefully considered. This study examined the effects of sample volume on microplastics, including how it can affect their abundance, size, shape, and polymer type. To this end, we collected 30 microplastics samples using five different groundwater sample volumes of 100, 200, 300, 400, and 500 L from three groundwater wells located in the Haean agricultural basin of Korea, in the wet and dry seasons of 2022. The results showed that the sample volume may impact the conclusions about the distribution and abundance of microplastics, but larger sample volumes required more resources and time. Overall, the sample volume is a crucial consideration in the microplastics investigation and must be carefully evaluated in order to accurately understand the occurrence and impact of microplastics in groundwater. This research was supported by Korea Environment Industry & Technology Institute (KEITI) through Measurement and Risk assessment Program for Management of Microplastics Program, funded by Korea Ministry of Environment (MOE) (2020003110010). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT, Ministry of Science and ICT) (No. NRF-2021R1F1A1064027).
HS14-A015
Using Three-dimensional Numerical Simulation Technology for Delineation of the Impact Area Caused by Large-scale Landslide
YuTing WANG, Jui-Yi HO#, Chih-Hsin CHANG, Yu-Ching LIN+
National Science and Technology Center for Disaster Reduction, Taiwan
The Three-Dimensional Distinct Element Code (3DEC) belonging to the Distinct Element Method (DEM) was adopted to generate the three-dimensional model for deep-seated landslide simulation in this study. This study simulates the deep-seated landslide by 3D numerical simulation to explore the sliding process and its impact area. The analyze results determine the unstable block and impact potential area caused by large-scale landslides. Two study areas of Xin-Zhuang settlement in Shan-Lin District, Kaohsiung City (District-D021) and the landslide area at 3.1k on National Highway No. 3 in Taiwan, were adopted to evaluate the performance of 3DEC model. The results indicated that good landslide simulation in both study areas for subsequent disaster prevention.
HS14-A017
Use UAS to Track Coastal Changes in Northern Area in Taiwan
Ting-Yu LIANG+, Hung-Ju SHIH, Shih-Chiang LEE, Yu-Ching LIN#, Jui-Yi HO, Chih-Hsin CHANG
National Science and Technology Center for Disaster Reduction, Taiwan
The erosion and deposition of coastal areas are greatly affected by wave, storm surge, and sea level rise especially during typhoon periods. The range or altitude changes in coastal area will affect the safety of coastal settlements in both short and long term time period. That highlights the importance of long-term records of coastal terrain change. Started from 2020, we use unmanned aircraft systems (UAS) to take multi-period images at 3 locations (Lao Mei, Yong Xing, and Zhong Jiao) of northern coast area in Taiwan. And transfer these images into digital surface model (DSM), which can show high resolution surface elevation. Through this multi-period DSM data, we can analysis the elevation changes between different seasons and notify the inter-annual variability of chosen locations. We can also analysis the efficacy of coastal facilities, as a reference for future facility construction.
HS14-A018
Prediction of Sewer Pipe Water Level Using Machine Learning Algorithm
Hyojin LEE1+, Hyunuk AN1#, Hee Sung LIM1, Seungsoo LEE2
1Chungnam National University, Korea, South, 2Korea Environment Institute, Korea, South
In highly impervious urban areas, the frequency of inundation and its damage is increasing due to the lack of drainage capacity and sewage outflow. Urban flooding causes enormous property damage and loss of life. Flooding countermeasures include expansion of drainage capacity and flood forecasting. In general, flood forecasting is practiced using river water level prediction. In the past, studies on river level prediction have been conducted using various methods. However, since urban inundation is caused by insufficient rainwater drainage capacity and sewage outflow, urban inundation is related to sewer pipe water level rather than river level. Currently, measuring sewer pipe water levels is being carried out as part of flood forecasting and damage prevention in Seoul, South Korea. However, the research on predicting sewer pipe water levels is insufficient and necessary. Therefore, this study predicted the sewer pipe water levels using the LSTM algorithm widely used in water level prediction research. We collected data on sewer pipe water levels from 25 points in Seoul. Since LSTM requires big data to perform deep learning, this study analyzed the Gangdong area where the least missing data among 25 points. We construct 5-, 10-, and 30-minute interval data through data in 1-minute intervals. We selected a week with significant sewer level fluctuations for accuracy analysis. In addition, the water level was predicted by adding rainfall data affecting sewer pipe water level. And the model performance was validated using an R square. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A2C200553012).
HS14-A019
Development of Rapid Flood Image Recognition Using Deep Learning Algorithm
Yuan-Fu ZENG#+, Gwo-Fong LIN, Cheng-Lin YANG
National Taiwan University, Taiwan
In recent years, the increased frequency of short-term, high-intensity rainfall events, caused by the intensification of climate change, has placed significant stress on urban and drainage facilities. Accurately predicting, detecting, measuring, and locating water volume and bodies can serve as the foundation for decision-making, enabling appropriate actions to minimize risk and loss. Therefore, developing an automatic and efficient flood image recognition system has become essential. Recent advances in deep learning have overcome the shortcomings of traditional technologies, particularly in the field of computer vision. Image segmentation technology has also gained significant attention in areas such as medical imaging, object tracking, image reconstruction, and intelligent transportation. In this study, we propose a deep learning-based flooded image recognition system, utilizing two widely-used image recognition models: DeepLabv3+ and Mask R-CNN. The accuracy of both models in detecting water bodies is compared, and the actual flooded area in the imagery is calculated. To prove the model's practicality, we applied it to intersection monitoring imagery in Taiwan, successfully identifying the flooded area and location with high accuracy and reliability. The proposed model can provide relevant emergency response units with an effective reference for flood management. This study highlights the significance of developing advanced flood image recognition systems, which can significantly contribute to reducing flood risk and loss.
HS14-A022
Semantic Standardization and Automatic Alert Application of Taiwan's Tangible Cultural Heritage Under the Flood Situation
Yu-Hua CHEN#+
National Science and Technology Center Disaster Reduction, Taiwan
With the rapid development of science and technology, the software and hardware of computer science are constantly innovating, the development of three-dimensional space is becoming more and more mature, and the concept of four-dimensional time series is also gradually emerging. Domestic and foreign are committed to formulating standards and regulations. Tangible cultural heritages are an important witness to the history of the country. It is located on the west side of the Pacific Ocean. And Taiwan, which is located in the volcanic and seismic belt around the Pacific Ocean, is one of the hot spots of natural disasters in the world. However, once the tangible cultural heritages are damaged, it will cause irreversible damage. This study refers to OGC (Open Geospatial Consortium, OGC) and OSM (Open Street Map, OSM) to formulate the three-dimensional semantic framework of tangible cultural heritages in the context of flooding disasters. It tries to filter through historical disaster data and flooding potential, cooperate with the Water Conservancy Department to announce the warning value of township flooding, and then use the system automation method to proactively Publish flood warning E-mail, string API, and system platform presentation, and provide diversified warning information, so that the competent authority can obtain the priority list of tangible cultural heritages before and during the disaster, so as to shorten the response decision-making time and achieve optimization management to reduce the risk of disasters to tangible cultural heritages.
HS14-A024
A Study on the Establishment of Flood Criteria for Vehicle Using a Survey
Cheonkyu CHOI#+, Hui-Seong NOH
Korea Institute of Civil Engineering and Building Technology, Korea, South
Recently, localized heavy rains have occurred due to the influence of climate change. When a flood occurs, it causes a lot of damage to property and human life located in the flood damaged area. In addition, traffic control and vehicle damage may occur on roads located in flooded areas. In this study, establishment of flood risk levels about vehicle according to the depth of flooding. First, selection of vehicle type for establishment of flood risk levels. And, In order to evaluate the risk according to the depth of flooding, the vehicle height calculates from the ground for each vehicle type. And, Conduct a survey of vehicle experts. This study has experience in repairing vehicles that suffered actual flood damage, and we conducted a survey of vehicle-related experts. The vehicle is divided into chassis, body, power train, interior, and electronic unit, and the degree of damage is evaluated according to the flood depth. In the future, it is considered that the flood criteria for vehicle can be used by determining the expected area of vehicle damage due to flooding.
ACKNOWLEDGEMENT
Research for this paper was carried out under the KICT Research Program (project no. 20230174-001, Development of Prediction and Monitoring Technology for Road Inundation based on Artificial Intelligence) funded by the Ministry of Science and ICT.
HS15-A005
Deep Learning-based Multi-source Soil Moisture Merging and Downscaling in Central Taiwan
Yu-Ru CHIOU+, Chia-Jeng CHEN#
National Chung Hsing University, Taiwan
Soil moisture (SM) is a critical component of the hydroclimate system, yet obtaining an accurate estimate of SM at high spatiotemporal resolution is still challenging. Three primary sources of SM information, namely satellite sensors, land surface models, and in-situ measurements, exhibit their own strengths and weaknesses in accuracy and spatiotemporal coverage. This study aims at conducting multi-source SM merging and downscaling based on Quadruple Collocation (QC) analysis and the Trajectory Gate Recurrent Unit (TrajGRU) model, respectively. QC method is used to merge SM data from Soil Moisture Active Passive (SMAP), Soil Moisture and Ocean Salinity (SMOS), Climate Change Initiative (CCI), and High Resolution Land Data Assimilation System (HRLDAS). TrajGRU is used to downscale the merged SM data from ~0.36° to 0.01° (~1 km) resolution based on the relationship between the SM data and auxiliary environmental variables (e.g., land surface temperature, land cover, elevation, and slope). Our analysis will be carried out in central Taiwan, and the merged and downscaled SM product is expected to not only resolve the issue of data scarcity but also support hydrological applications in this region.
HS15-A006
Global Snow and Ice Cover Dataset and Climatology Derived from 35 Years of Multi-satellite Observations
Peter ROMANOV#+
City University of New York, United States
Since 2006 NOAA has been using Global Multisensor Automated Snow and Ice Mapping System (GMASI) for operational monitoring of the Earth’s cryosphere. The GMASI system implements an automated algorithm which processes observations in the visible and infrared bands from the AVHRR sensor onboard NOAA and METOP satellites and observations in the microwave from SSMI and SSMIS sensors onboard DMSP satellites. The primary output of the system is a daily spatially-continuous (gap-free) maps of snow and ice cover at the spatial resolution of 4 km. The GMASI algorithm has been applied to process historical satellite data back to 1987 and to generate a high-resolution 30+ year-long daily dataset of global snow and ice cover. Daily data have been further used to produce monthly and yearly statistics of the snow and ice cover occurrence and to estimate long-term trends in the snow and ice extent. In the presentation we provide details on the data processing algorithm focusing on efforts to ensure consistency of retrievals across the 30+ year-long time period. Estimates of the snow and ice extent and corresponding long-term trends derived from the GMASI-reprocessed data are compared with the available coarse resolution snow cover climatology based on NOAA interactive snow and ice charts. The output of the GMASI system is shown to closely match the accuracy of snow maps produced within NOAA Interactive Multisensor Snow and Ice Mapping System (IMS) and to over-perform the existing coarse, 190 km, resolution, NOAA Snow Climate Data Record (CDR). The analysis of the Northern Hemisphere snow area extent changes over time estimated from the GMASI dataset supports earlier findings of a generally decreasing snow cover extent in late spring, and in summer and of its small increase in winter months.
HS15-A022
Estimation of Actual Evapotranspiration by Using Soil Moisture Data
Harshita Rani AHIRWAR#+, Anupam Kumar NEMA, Prashant K. SRIVASTAVA
Banaras Hindu University, India
The great importance of water is well-known worldwide. Also, its various forms are present on Earth. Alternation of any natural activity distress the life on the planet proving the importance of the water cycle. Hence, it becomes vital to understand every form of water, therefore, the moisture loss from the agricultural field and vegetation. The research work attempts to illuminate the process of actual evapotranspiration via soil characteristics (soil moisture, field capacity, and wilting point). The experiment was done for a single field considering the two extreme conditions of crop coefficient (fully vegetative and bear soil) to reach the results of actual evapotranspiration from potential evapotranspiration. From various combinations created, it was found that soil moisture data at a depth of 20cm gives a better result compared to the others like 5 cm and 50 cm depths and satellite data. Further, from standard and experimental values of field capacity and wilting point, the RMSE value of both was almost alike but standard values perform better. The research delivers that actual evapotranspiration can be calculated with minimum data generated in the field and has a lot more scope for the future to develop better algorithms.
HS15-A023
Examining the Extreme and Long-term 2022 Drought Event in the Southern Region of South Korea Using Remote Sensing-based Drought Index
Gwangsu PARK+, Won-Ho NAM#
Hankyong National University, Korea, South
Drought is a disaster that causes great social, economic, and environmental damage worldwide, and its occurrence frequency and magnitude are increasing due to recent abnormal climate. In the case of domestic drought monitoring, research is being conducted using satellite images that can provide periodic as a drought monitoring in ungauged areas. The drought index is used to quantitatively analyze and respond to drought damage, and representative drought indices include the probability distribution based Standard Precipitation Index (SPI) using ground precipitation data, the Standard Precipitation Evaporation Index (SPEI) including variability in precipitation and temperature, and Evaporation Stress Index (ESI) that predicts drought using satellite image data. The average temperature in spring 2022 (March to May) was the highest since 1973 weather observation, and May precipitation was the lowest ever, and as of June 6, cumulative rainfall was a national average of 193.6 mm, which was only 55% of the average year, resulting in an extreme drought. From July to August, the southern regions except the metropolitan area showed less precipitation compared to the average year, so the drought was not resolved even by the rainy season. Even, the drought duration has been reported to be the longest ever since 1974. In this study, the time series changes by individual indicators were analyzed for the spring drought in 2022 and the occurrence period of drought in the southern region using the drought index. In the case of SPI and SPEI, the temperature and precipitation in the weather station point data were utilized, and the ESI utilized satellite image data provided by the Terra MODIS (Moderate Resolution Imaging Spectroradiometer). Accordingly, there are compared drought indices and analyze spatio-temporal variability with respect to the overall cycle (preparation, occurrence, diffusion, deepening, and resolution) of extreme drought events due to continuous lack of precipitation in 2022.
HS16-A003
Inundation Risk and Its Impact Assessment on Groundnuts Under Climate Change in Yunlin County, Taiwan
Yi-Hua HSIAO1#+, Chun-Che CHEN1, Xing-Yu LIU1, Chih-Tsung HSU2, Dong-Sin SHIH3
1National Science and Technology Center for Disaster Reduction, Taiwan, 2National Center for High-Performance Computing, Taiwan, 3National Yang Ming Chiao Tung University, Taiwan
According to the 110-year agricultural land area statistics, the total area of Yunlin County is about 307.64 mi2, accounting for 61.73% of the total area of the county. It is mainly rich in rice, groundnuts. According to the statistics of typhoon and water damage losses in the past 20 years, the largest losses in one year are $440 million (typhoon) and $350 million (water damage), and the frequency of water damage is increasing. The types of disasters that groundnuts will be damaged are mainly typhoons and heavy rains. In addition to strong winds that cause dryness and affect the development of flower buds, inundation is more likely to cause losses. Therefore, this study uses typhoon event data under climate change scenarios to simulate future inundation disasters, and conduct risk assessment for groundnuts. The climate change data used is RCP8.5 dynamic downscaling HiRAM-WRF typhoon events, with a total of 149 in the base period (1979 to 2008), 450 in the middle of the 21st century (2040 to 2065) and 214 in the end of the 21st century (2075 to 2099). The SOBEK model was used to simulate the above typhoon events, and calculate the proportion of the worst inundation distribution above 0.3m within the groundnut planting range in Yunlin County in each period. The analysis results show that the average inundation occurrence probability is about 17.3% in the base period, about 15.0% in the middle of the 21st century, and about 22.5% in the end of the 21st century in the area where groundnuts are distributed. Overall, the increase in the scope and frequency of inundation is more likely to cause losses. The follow-up disaster reduction and adaptation assessment can be carried out early by the results of this study.
HS16-A006
Measuring Flow Field of Scouring Hole Using Laser Doppler Velocimetry
Wei-Feng TAI#+, Dong-Sin SHIH
National Yang Ming Chiao Tung University, Taiwan
Taiwan is located at the junction of the Eurasian plate and the Philippine Sea plate, pushing out a series of north-south mountains. The rivers primarily run east-west and have steep slopes in the flow channel. The bridges connect the towns and are essential for Taiwan's economy and population communication. In addition, many reservoirs or hydrological structures in Taiwan, such as sand check dams, fishways, and groundsill works...etc., are built upstream of the river, resulting in insufficient sand sources for bridge piers. Therefore, the scouring around the bridge pier of Taiwan is getting severe under extreme floods. In recent years, the global climate has intensified. The intensity of rainfall, the shortening of rainfall delay, and other factors have made sediment around the foundation of bridge piers more prone to local erosion. The traditional measurement of flow velocity and turbulence is mostly an invasive device that interferes with the flow field and may cause some measurement errors. This study tried using the open channel flume experiment to measure the flowing current of equivalent scour by the non-invasive Laser Doppler Velocimetry. The study also explores the relationship between the flow field and the scouring pit, then tries to identify the significance of turbulent flow intensity and maximum scouring. From measurements, the deepest erosion area is at the front of the horseshoe-shaped fossa flow area from the observed position. Furthermore, the area with the most significant turbulence intensity was about 1.2 times the diameter of the pier behind the pier.
HS16-A007
Analysis of Compound Flood Risk Using Trivariate Copulas
Jiun-Huei JANG#, Jun-Hao LIN+
National Cheng Kung University, Taiwan
For flooding triggered by multiple factors, flood risks are greatly influenced by the correlations of the triggering factors. In this study, trivariate copulas were used to describe the joint probability of rainfall (R), storm surge (T), and river discharge (Q) based on 28 historical events for a coastal area in Daan River, Taiwan. The model parameters were estimated using the maximum likelihood method, and the best-fit marginal and copula functions were selected using the Akaike Information Criterion and Bayesian Information Criterion. The results showed that R, T, and Q fitted Log-Normal, Gumbel, Gamma distributions, and the joint probability fitted Joe copulas the best. To estimate the compound flood risk simultaneously influenced by the R, T, and Q, Monte Carlo simulations were employed to generate numerous sets of (R, T, Q) based on the determined copula and served as boundary conditions for flood simulation. The simulated flood depths were used to establish a statistical model for calculating the return period for any set of (R, T, Q). The proposed method can be applied to different regions to enhance flood risk assessment and disaster management under the impact of compound flooding.
HS16-A011
Urban Restoration Priority Assessment Against Urban Flood Damage with Resilience
HyungJun PARK+, Chanjin JEONG, Hyun Jung LEE, Seungoh LEE#
Hongik University, Korea, South
Flood forecasting technology has been developing because the frequency and scale of damage of floods become increased due to globalized climate variability. At the same time, researches related to the evaluation of resilience, the ability to resist and restore after specific flood damage, are emerging as an important field. However, separate factors and methods were studied and presented for each case, and most of them focused on measuring only the resilience of facilities. Therefore, this study developed the blanket evaluation methodology for resilience degree that is able to consider additionally social and economic factors as well as facility one. Also, to reflect the temporal variation, it is subdivided into a dynamic factor that is affected by the time and a static factor that is less affected by the time. Facilities factor includes both buildings and infrastructures, and damage costs were quantified through the depth-damage functions in the literature. The resident characteristics and distribution, which were quantified through the ratio of the population affected by flooding and the flooded area ratio are considered in social factor. Lastly, economic factor related to recovery and resilience speed includes the regional income and resident income level, which were used as weighting factors for facilities and social factors. The time-damage graph for each zone was created using QGIS, one of popular GIS softwares, and resilience was calculated through it. Finally, after applying to the pilot urban area, the priority of urban restoration was visualized. By comparing and analyzing with the flood risk map, the areas that need to prepare for floods was listed. If further studies for additional factors such as industrial and policy factors will be conducted in the next time, it would be expected to be used as more precise reference materials to improve urban flood resilience.
HS17-A001
Flood Susceptibility Mapping Using Frequency Ratio and Weights of Evidence Models: A Study on Brahmaputra River Basin
Pritiranjan DAS#+, Netrananda SAHU
University of Delhi, India
Flood is one of the most devastating natural disasters worldwide and having great influence in the Indian sub-continent. Therefore, thorough flood control is required to mitigate the effects of flooding on human lives and livelihoods. The main aim of this study to examine the application of the frequency ratio (FR) and weights-of-evidence (WoE) models for flood susceptibility mapping in the Brahmaputra River basin. At first, a flood point data was prepared using Google Earth Engine (GEE) using global dataset and locations were identified in the study area. The flood point database was split as training data and testing dataset, 70% as training and 30% as testing dataset. Training database were used for model calibration and testing database used for the validation purposes. In the next step, flood influencing factors such as rainfall, elevation, slope, lithology, geology, land-use, distance from rivers, soil texture, slope angle, slope aspect, plan curvature, topographic wetness index (TWI). Each conditioning factor was used for flooding mapping using bivariate statistical analysis for flood susceptibility study. Following that, the receiver operating characteristic (ROC) curves for the obtained flood susceptibility maps were constructed, and the area under the curves (AUCs) were computed. The final results showed that the FR and WoE models produced nearly identical and fair outcomes. As a result, these flood susceptibility maps can help academics and planners in developing flood mitigation plans.
HS17-A003
River Sediment Prediction Based on Coupling WRF with GSSHA Models
Wen Yi LU+, Chia-Jeng CHEN#
National Chung Hsing University, Taiwan
Rainfall and runoff are responsible to the inception and transport of sediment over a catchment, respectively. New rainfall datasets available from satellite products (e.g., the Integrated Multi-satellitE Retrievals for Global precipitation measurement, IMERG) and numerical weather prediction models (e.g., Weather Research and Forecasting model, WRF) can provide more real-time information for river sediment analysis. In this study, rainfall data from IMERG and WRF are used to drive the Gridded Surface Subsurface Hydrologic Analysis model (GSSHA) to investigate the inception mechanisms of sediment motion and simulate the amount of sediment discharge in the Shimen Reservoir watershed in Taiwan. GSSHA is first calibrated with gauge-based rainfall and sediment discharge derived from rating curves to ensure a reasonable simulation of river runoff and sediment discharge at catchment outlets. Afterwards, by replacing gauge-based rainfall with IMERG or WRF rainfall, we are able to assess the predictability and physical mechanisms of sediment initiation and transportation. Preliminary results indicate that, as expected, the accuracy and spatiotemporal patterns of precipitation estimates are the determinant of the predictability of sediment discharge. The coupled modeling framework can indeed disclose the dynamics of sediment motion, pinning down the hotspots of soil erosion for further attention.
HS17-A004
Assessment of River Morphological Changes Based on Coupling WRF-Hydro with SRH-2D Models
Yi Yun LU+, Chia-Jeng CHEN#
National Chung Hsing University, Taiwan
Characteristics associated with surface runoff and sediment transport in a catchment can change drastically in response to extreme rainfall events, accelerating the evolution of river morphology. Modeling techniques can provide a means to assess transient changes in river morphology. This study aims at coupling the Weather Research and Forecasting model-Hydrological modeling system (WRF-Hydro) with a two-dimensional river hydraulic mobile-bed model referred to as the Sedimentation and River Hydraulics-2D (SRH-2D) to simulate rainfall-runoff and river bed changes in the Yousheng Creek in northern Taiwan. WRF-Hydro is able to simulate multi-scale land-atmosphere interactions and streamflow, while SRH-2D uses the hybrid mesh of quadrilateral and triangular cells to simulate various flow-related mechanisms, including river hydraulics, sediment transport, and river bed changes. WRF-Hydro is first calibrated to ensure a reasonable simulation of runoff at the downstream station to the Yousheng Creek, and then the simulated upstream runoff is used to drive SRH-2D to simulate multiple large flow events in a semi-consecutive fashion. It is found that simulated changes in the river bed over different cross sections mimic the survey data, suggesting the capability of such coupled modeling framework in predicting morphological changes. Under this framework, locations of channel erosion and deposition, found to be dependent upon the simulated flow velocity, can also be identified in great detail.
HS17-A010
Seasonal Variability of River Discharge and Profile Analysis Using Acoustic Doppler Current Profiler (ADCP): Monitoring the Agno River in San Carlos City, Pangasinan, Philippines
Kim Bryan CABRERA1#+, Decibel FAUSTINO-ESLAVA1, Juan Miguel GUOTANA2, Loucel CUI1, Jenielyn PADRONES1, Richard WILLIAMS3, Emma BILES4, Laura QUICK3, Patrick BYRNE4, Ylam Shalev MATBA1, Kennethjer ALEJO1, Francis GONZALVO1, Maria Regina REGALADO1
1University of the Philippines Los Baños, Philippines, 2University of the Philippines Diliman, Philippines, 3University of Glasgow, United Kingdom, 4Liverpool John Moores University, United Kingdom
Rivers provide insights into a watershed’s health and potential future trajectories. One of the crucial watersheds in the Philippines is the Agno Catchment. The Agno River is the most significant river within this catchment and provides food, sanitation, irrigation and livelihoods for local communities. Monitoring river discharge, paired with the analysis of water quality samples, can create contaminant flux estimations - which are valuable for estimating total pollution loads within rivers, particularly for highly modified (by agriculture, mining, and other land uses) regions. Estimating river discharge in wide and deep rivers, like the Agno River, requires a more advanced approach than handheld flow gauging used for smaller rivers. This study utilized a remote-controlled Acoustic Doppler Current Profiler (ADCP). Discharge data were collected from one representative site at the downstream section of the Agno River, using an ADCP. Monitorings were done during the wet and the dry seasons - representing the two pronounced seasons in the area. Data were collected for one month during each season with an average of six (6) transects per day. Data were then post-processed to achieve a ≤0.03 covariance for the discharge (Q). Average monthly wet and dry season discharges were 119.33 m3/s and 41.907 m3/s respectively. A transverse profile of the riverbed was also ascertained by recording depth values throughout each transect. Maximum and average river depth were also recorded for wet (8.01m, 3.36m) and dry (6.56m, 3.17m) seasons. Results from the study showed that the use of ADCP improved the monitoring of river discharge, making seasonal morphological changes more identifiable. Discharge data can be used as a baseline for planning activities of local government units for disaster risk reduction management. River discharge measurement results can then be correlated with water quality parameters for estimating contaminant fluxes.
HS19-A003
Performance Evaluation and Improvement of CMFD-based Precipitation Products Over Shanghai City, China
Nuo LEI#+, Zhengzheng ZHOU, Shuguang LIU, Guihui ZHONG, Sha LOU, Qi ZHUANG
Tongji University, China
Precipitation products with high resolution for urban areas remain an important and challenging issue. The main purposes of this study are to evaluate the accuracy of the China Meteorological Forcing Dataset (CMFD) in the Shanghai megacity and to improve the accuracy of the CMFD precipitation. With the rain gauge observations for the 2013-2018 period, we evaluate the error and detection ability of CMFD at the sub-daily, daily, monthly, and yearly scales, and examine the spatial variation of CMFD performance over the region. The Geographic Differential Analysis (GDA) method is used to calibrate the CMFD precipitation dataset. The results show that the performance of CMFD precipitation varies from sub-daily to annual time scales with better accuracy at the monthly scale in the study region. The CMFD can capture the spatial variability over the region with less error in the north and outliers in the center. The GDA-based calibration framework can significantly improve the capability of CMFD products, especially at the sub-daily and daily scales. The calibrated CMFD can provide reliable precipitation estimates and capture more extreme precipitation events. The improved CMFD products can provide a key basis for applications related to hydrological and meteorological hazard monitoring and assessment in the Shanghai area. The overall framework is scalable and could be readily generalized to other regions, and the calibrated product can be used in the research of urban natural disaster risks and other studies.
HS19-A008
Bivariate Rainfall Frequency Analysis in an Urban Watershed: Combining Copula Theory with Stochastic Storm Transposition
Qi ZHUANG#, Shuguang LIU, Zhengzheng ZHOU, Yuting JIN+
Tongji University, China
Extreme rainfall is a critical “agent” driving flash floods in urban areas. In rainfall frequency analysis (RFA), however, storms are usually assumed to be uniform in space and fixed in time. Spatially and temporally uniform design storms and area reduction factors are oftentimes used in conjunction with RFA results in engineering practice for infrastructure design and planning. The consequences of such assumptions are poorly understood. This study examines how spatiotemporal rainfall heterogeneity impacts RFA, using a newly-introduced bivariate framework consisting of copula theory and stochastic storm transposition (SST). A large number of regionally extreme storms with specific features—rainfall depth, duration, intensity, and level of intra-storm spatial organization—were collected. Rainfall intensity-duration-frequency (IDF) estimates exhibiting these bivariate features were then generated by synthesizing long records of rainfall via SST. The results show that dependencies exist among spatiotemporal storm characteristics. Bivariate frequency results exhibit smaller uncertainties but more complex physical meanings that the results from conventional methods. In particular, the highly spatially organized storms play a leading role in frequency estimates.
HS20-A009
Energy Distribution Within the Canopy Column
Kwanghun CHOI, Kyungrock PAIK#+
Korea University, Korea, South
Incoming Solar radiation on the terrestrial surface is distributed into various fluxes. The widely used surface energy balance equation treats the surface as 2-d entity. However, the Earth’s terrestrial surface is mostly covered by vegetation, rather than bare land. Energy distribution within the canopy column is complex: in addition to three (ground, sensible, latent) heat fluxes, redistribution within the canopy, photosynthesis, and heat captured within the vegetation body and canopy air needs to be considered. In this sense, 2-d assumption is limited and terrestrial surface should be seen as 3-d entity. Here we suggest the 3-d canopy column structure consisting of the hypothetical canopy column for the space of vegetation on the ground surface. Energy distribution within the 3-d canopy column using data from Fluxnet sites of different biome and climate will be carefully examined and presented with discussions.
HS21-A002
Safe Alternative Wet and Dry Irrigation to Increase Water Use Efficiency in Dry-season Rice Cultivation, Case Study: Cambodia
Chan Arun PHOEURN#+
Institute of Technology of Cambodia, Cambodia
Improving water use efficiency is considered globally as a key adaptive strategy for responding to climate change and for sustainable development to countries such as Cambodia where rice growing is the main source of income. The objective of the study is to evaluate the effectiveness of alternative wet and dry (AWD) compared to conventional flooding method in terms of water use efficiency and growth responses, and (2) to assess the tolerance level of rice toward different AWD severities. During AWD cycle, the field was re-irrigated whenever the water level in the field drops below -15 and -20 centimeters for AWD15 and AWD20, respectively. The field experiment was conducted at Cambodia Agricultural Research and Development Institute (CARDI) in 2021 and in Kampong Province in 2022. The Annova Test reveals that the yield, water productivity and the majority of phenological indicators such canopy cover, percentage of filled kernels, harvest index, and biomass of rice grown in AWD15 were not significantly different from those in CF condition. In terms of AWD application, CARDI could save the highest amount of water in AWD15 treatment equal to 34%, which is 12% and 11% higher than KTM 1 and KTM 2. Grain yield and WUE were not significantly different. Average yield was 3.59 t ha−1 in AWD15, 3.29 t ha−1 in AWD20, and 3.61 t ha−1 in CF, respectively. Average WUE was 0.52 kg m-3 in AWD15, 0.44 kg m-3 in AWD 20, and 0.40 kg -3 in CF, respectively. From this study, we can conclude that AWD could potentially be an adaptive measure for climate change to help farmers who grow rice in the dry season to save more input water.
HS21-A003
Study on the Multi-scale Regional Climate-vegetation-evaporation-runoff Relationship Based on Wavelet-Budyko Coupling Model
Wenting WEI+, Jun NIU#
China Agricultural University, China
This research provides a new method that combines wavelet analysis and the Budyko framework to study the multi-scale regional climate-vegetation-evaporation-runoff relationship. Based on this method, the driving mechanisms of regional climate change on hydrological processes are comprehensively analyzed, the factors that can be included in Budyko parameter estimation at different scales are determined, the contribution of climate change and human activities to regional hydrological water resources is quantitatively recognized, and the multi-scale relationship between regional climate-vegetation-evaporation-runoff is clarified, providing reference for the protection of the ecological environment, rational development and utilization of agriculture, and configuration and management of water resources in the Shiyang River Basin.
HS21-A007
Spatial-temporal Dynamics of Cropland Ecosystem Water-use Efficiency and Its Response to Climate Change and Human Activities in the Shiyang River Basin, Northwestern China
Fei TIAN#+
China Agricultural University, China
To deal with serious water resources crisis, the Shiyang River Basin (SRB) of Hexi Corridor in Northwestern China has been experiencing rehabilitation for water-saving since 2006. Water-use efficiency in cropland (WUEc) is a critical indicator to understand the response of carbon-water interactions. Because we currently lack a clear picture of how WUEc responds to climate and human activities factors in the SRB, here we applied Moderate Resolution Imaging Spectroradiometer (MODIS) satellite images to obtain a regional estimation of gross primary productivity in cropland (GPPc) and actual evapotranspiration in cropland (ETc), and analyzed the variations in WUEc and climate and human activities factors, then we evaluated the annual WUEc responses to climate and human activity factors and discussed major driving factors underlying the interannual variability (IAV) of WUEc from 2000 to 2014 in the SRB. Finally, we clarified the implications of the water saving project (WSP) on the water cycle. Results indicated that increased WUEc covered 97.25 % of the cropland area, with a trend of 0.017 g C kg−1 H2O yr-1. ETc decreased at 0.41 mm yr-1. ETc decreasing pixel mainly occurred in the irrigation districts of WSP completed by 2010. The IAV of WUEc was mainly determined by ETc (68 %) rather than GPPc (6%). The relative contribution of human activities factors in the WSP to ETc was 77.5 %, while that of climate factors was 22.5 %. Which further proved water availability increase was mainly artificially controlled, an effect of the WSP rather than that of climate factors.
HS21-A010
Optimal Cropping Patterns Can Be Conducive to Sustainable Irrigation: Evidence from the Drylands of Northwest China
Yunfei FAN+, Sufen WANG#
China Agricultural University, China
The pressures of frequent extreme weather, water shortages and increasing food demand pose a continued challenge of maintaining the sustainable development of irrigated agricultural systems. Although rational arable land management is fundamental to alleviating these pressures, the relationship between cropping patterns and irrigation sustainability is understudied. Using the Hexi Corridor as an example, a maximum entropy machine learning model was used to determine the optimal cropping pattern based on crop suitability and to explore the impact mechanism of the optimal cropping pattern on the irrigation sustainability index (SI) from the perspective of reliability, resilience, and vulnerability. An optimal cropping pattern was conducive to sustainable irrigation and reduced irrigation water use by 21.03% from 1960s–2010s with no continued agricultural expansion. Thus, the challenges of food security and sustainability for similar regions, and globally, can be met but will require major changes in cropping planning and management.
HS21-A011
Reallocating Crop Spatial Pattern Improves Agricultural Productivity and Irrigation Benefits Without Reducing Yields
Sufen WANG#+
China Agricultural University, China
The allocation of crop spatial pattern has an appreciable impact on achieving sustainable agricultural development. Crop spatial pattern should be adjusted in accordance with the agricultural environment factors and climate change so that we make full use of agricultural resources to produce more food. However, crop suitability has not been adequately considered in crop patterns, ignoring the fact that the fundamental solution to agricultural water scarcity is to promote crop water productivity (CWP). This study aims to reallocate crop spatial patterns while synergistically improving irrigation benefits and water productivity. To achieve this, we developed a minimum cumulative resistance (MCR) model based on ecological movement processes to simulate crop suitability distribution and thus determine crop spatial patterns. The results show that the adjusted crop pattern could increase the regional water productivity by 1.35 times and the net benefits of unit water by 0.94%, and maintained crop yields. Under future climate scenarios, this approach can still ensure irrigation benefits and food security. Therefore, the MCR model provides effective crop patterns and solutions for sustainable agricultural development when facing a complex agricultural environment.
HS21-A012
Surface Soil Moisture Assimilation Improves Subsurface Soil Moisture Estimation
Dehai LIAO+, Jun NIU#
China Agricultural University, China
Surface soil moisture is widely available from remotely sensed imagery, however, estimation of subsurface moisture has long been a common challenge for the scientific community. Here, we assimilate surface soil moisture into a physical hydrological model and use a dual state-parameter filtering method to jointly update the model parameters to better represent the physical processes of the model, ultimately achieving a better estimate of subsurface soil moisture.
HS21-A014
Analytical Modelling of Water Retention Across the Ecological Indexes and Hydrological Process Mechanism
Guangchuang ZHANG+, Yiping WU#
Xi'an Jiaotong University, China
Land water cycle and water resources health are important prerequisites to ensure regional sustainable development and ecosystem security. As an important part of ecosystem services, water retention function plays a vital role in the stability and sustainability of regional ecosystems. The weakening of its function will directly lead to the decrease of biodiversity, the aggravation of land desertification, and even the deterioration of local regional weather, etc., which will lead to the imbalance of the watershed ecosystem that was originally in dynamic balance, and then affect the landscape structure and ecological functions of the watershed ecosystem. In recent decades, scholars at home and abroad have done a lot of research on the service function of watershed ecosystem, especially the water retention function, with various research methods and perspectives. At present, the methods for calculating the water retention function mostly focus on discussing the variation law and its influencing factors of single or few hydrological factors (such as surface runoff, soil water, runoff yield), or only pay attention to the change and influence of vegetation growth, and some studies have been carried out on site scale through field sampling for local analysis and discussion. Most of the work often ignores the integrity of watershed ecosystem, and lacks the theoretical research on the water retention function of hydrological process and multi-factors of ecological system elements. The purpose of the present study is to provide a quantitative diagnosis method and system of water retention function integrating hydrological and ecological elements, so as to solve the problem in the existing methods, which only discusses watershed water retention quantity, but is difficult to reflect the function of vegetation conservation.
HS22-A002
Soil-moisture Derived Spatial Drought Prediction Using Long Short-term Memory (LSTM) Model in India
Vaibhav KUMAR#+, Hone-Jay CHU, Sumriti Ranjan PATRA
National Cheng Kung University, Taiwan
Drought is one of the costliest hydro-meteorological hazards, which poses a fundamental challenge to predict spatially and temporally. The severity and frequency of drought events have increased under the warming climate. It has sophisticated physical mechanics characterized by precipitation deficiency, having a ripple effect on agricultural and hydrological systems, which causes severe socio-economic damage, particularly in emerging countries like India. However, developing accurate and more reliable drought prediction models is challenging but essential for mitigation strategies and enhancing early warning systems. Even though the deep learning approach can enhance our comprehensive understanding of drought features, specifically spatial variations, intensity, and frequency, they have not been thoroughly explored. Therefore, this study proposes a deep learning method, specifically the Long Short-Term Memory (LSTM), to predict standardized soil-moisture index (SSI) at short-term time scales (SSI-06) over India region. This region has experienced severe droughts during this spanning period. The LSTM model utilizes soil-moisture and other hydro-meteorological variables (herein precipitation, potential evapotranspiration, and surface air temperature) as predictors acquired from the Global Land Evaporation Amsterdam Model (GLEAM), India Meteorological Department (IMD), and Climate Research Unit (CRU) datasets continuous from 1981 to 2020. The observed and predicted results were compared during monsoon season ((June to September) in the 2009 and 2015 severe drought years. Moreover, LSTM improves soil-moisture drought features and focuses on spatial variations, intensity, and frequency. Albeit having these drought characteristics, the model needs to tightly constrain to enhance forecasting accuracy and more reliable simulations over India. Further, the present study will strengthen soil-moisture drought conditions through a data-driven prediction model. It will be helpful for drought mitigation purposes.
HS22-A004
Multi-objective Extraction-injection Optimization Modeling for Saltwater Intrusion Control Using Machine Learning Models
Jina YIN#+, Ning WANG, Zhu LIU
Hohai University, China
Data-driven machine learning surrogates are used to substitute complex groundwater numerical simulation models within optimization algorithms to reduce computational burden for large-scale aquifer management. The traditional surrogate-assisted simulation-optimization modeling has been limited due to uncertainty persisting in surrogate model predictions. More advanced methods are imperative to reduce impact of uncertainties from surrogate models on solution optimality. In this regard, we propose an ensemble surrogate-based simulation-optimization methodology for optimal saltwater intrusion (SWI) control through accounting for uncertainty induced by surrogate models. The optimization model includes two conflicting objectives: minimizing total groundwater pumping and injection rate from an extraction-injection horizontal well system while reducing chloride concentration at monitoring locations below a certain level as much as possible. Three types of machine learning surrogates including artificial neural network, random forest and support vector machine were established to replace a high-fidelity physically based saltwater intrusion model. Optimal Latin hypercube design combined with parallel computing on high performance computing (HPC) was performed to generate input-output data of pumping and injection schedules and resulting salinity levels. An innovative Bayesian model averaging approach was presented to derive posterior model weights by considering big training and testing data. The newly constructed individual and ensemble machine learning surrogates were then coupled with a multi-objective optimization model to obtain Pareto-optimal extraction-injection strategies, where the optimization was solved using NSGA-II. Results showed that individual and ensemble surrogate models were accurate enough for salinity prediction. Through comparing the Pareto-optimal solutions, the ensemble surrogate-based modeling was confirmed to provide more reliable and conservative strategies for alleviating saltwater intrusion threat while considerably reducing computational cost.
HS22-A007
A Method of Solving Data Imbalance Problem to Improve the Performance of Data-driven Model for Estimating High-concentration Occurrence Probability for the Naturally Occurring Radioactive Materials in Groundwater
Hyeongmok LEE+, Jina JEONG#
Kyungpook National University, Korea, South
Groundwater can be easily contaminated by naturally occurring radioactive materials (NORMs) as it interacts with surrounding geological elements while moving through the primary and secondary pores of the underground medium for a long time. Therefore, it is necessary to efficiently evaluate groundwater contamination vulnerability to NORMs. In this study, a classification model to assess a high-concentration occurrence probability for NORMs in groundwater was developed based on the in-situ groundwater quality monitoring data and geological information, and its practical applicability was evaluated. For model implementation, random forest (RF), an ensemble machine learning model, was applied to develop the proposed model; the actual in-situ monitoring data (pH, temperature, Eh, EC, DOE, HCO3-) and the concentration of NORMs (238U and 222Rn) acquired from 201 locations were applied in this study. In particular, this study used data sampling techniques to solve the data imbalance problem and improve the performance of the developed model. The sampling techniques applied in this study are as follows: (1) under-sampling, (2) SMOTE (synthetic minority over-sampling technique), (3) complex sampling that comprehensively utilizes techniques of (1) and (2). The classification results showed that the accuracy of the model applying the sampling techniques was higher than the model without using the sampling techniques. In particular, techniques (3) and (2) showed superior performance for estimating the high-concentration occurrence probability of uranium (238U) and radon (222Rn), respectively. Data imbalance problem frequently occurs in developing data-driven geological estimation model. In this aspect, this study might be practical in suggesting a method to improve the performance of the estimation model. In addition, the developed model can contribute to the safety of the groundwater user by informing the risk of the NORMs in groundwater in real-time.
HS22-A011
A Hybrid Approach for Forecasting Flood Runoff by Combining a Rainfall-runoff Simulation Model and Deep Learning Networks
Kyung Soo JUN#, Kyung Soo JUN+
Sungkyunkwan University, Korea, South
Accurate prediction of flood runoff during storm events is essential for mitigating flood damages. Deep learning model is a powerful tool to address various practical problems, and it is extensively used for forecasting in diverse areas. However, as the forecast lead time increases, it shows poor performance because the output variable has less correlation with the input variables. In this study, hybrid models which integrate the outputs of physically based rainfall-runoff simulation model into data-driven deep learning models are proposed to predict hourly flood runoff from Yongdam Dam Basin in South Korea. Two types of hybrid models were established. One is the deep learning model that includes the runoff forecasted by a physically based simulation model as input variable. The other adopts error correction modeling that attempts to analyze the potential nonlinear relationships between the previous rainfall and runoff data and errors of runoff forecasted by the simulation model. Artificial neural networks (ANN) and HEC-HMS models were used for machine learning model and physically based simulation model, respectively. To assess the hybrid forecasting approach, performances of the physically based model, ANN based pure machine learning model, and the hybrid models were compared. Sixteen flood events were used for model calibration (or training) and validation. Various statistical indices were employed to assess prediction performance. The hybrid models showed better performance in prediction accuracy compared with the physically based rainfall-runoff simulation model or pure machine learning model especially as the forecasting lead time increases. This suggests that the hybrid models can take advantage of complementary strengths of both the simulation model and the deep learning model. Hence, the physically based simulation model coupled with deep learning model can be used for accurate forecasting of flood runoff. This study was supported by the Korea Environmental Industry and Technology Institute (KEITI) (Grant number: 2022003460001).
HS22-A012
Combining CNN and Transformer for Enhanced Daily Streamflow Forecasting: A Study on Lanyang Stream Basin
Wei Jin WANG#+, Weicheng LO
National Cheng Kung University, Taiwan
Flood disasters often result in significant losses of life and property and are considered one of the most devastating natural hazards. In recent years, the frequency and intensity of extreme rainfall events have increased significantly. As a result, reliable and accurate streamflow forecasting is of vital importance. Rainfall-runoff modeling is a complex and nonlinear time series process. In data-driven methods, numerous studies have demonstrated their promising performance in streamflow prediction by using deep learning approaches such as Long Short-Term Memory (LSTM), Convolutional Neural Network (CNN) and Transformer. This study proposes a deep learning framework that combines CNN and Transformer for rainfall-runoff modeling. The framework extracts precipitation and meteorological features of meteorological stations through self-attention mechanisms and aggregates these features and the streamflow data through cross-attention mechanisms. In this study, the proposed model is applied to the Lanyang Stream basin to validate its applicability to the task of streamflow forecasting by predicting the 5-day-ahead runoff. The results show that the proposed model significantly outperforms LSTM, CNN and traditional Transformer models in terms of the Root Mean Squared Error (RMSE) and the Nash–Sutcliffe Efficiency (NSE) for 1-day-ahead runoff predictions. Additionally, the results also indicate that the model has better performance for multiple-step-ahead runoff predictions.
HS22-A016
Development and Application of a High-resolution Urban Flood Model Based on Cellular Automata
Hyeonjin CHOI#+, Songhee LEE, Hyuna WOO, Seong Jin NOH
Kumoh National Institute of Technology, Korea, South
In this work, we propose and evaluate a high-resolution urban flood model based on cellular automata. Cellular Automata (CA), a rule-based machine learning model, has advantages over conventional physics-based flood models, especially in terms of computational efficiency in high-resolution predictions. Instead of solving the entire St. Venant equation, CA can relax computational limits without losing computational accuracy. However, user-defined rules in CA-based models can be a source of uncertainty leading to unstable predictions such as numerical oscillations. By reviewing several existing CA algorithms, we will discuss what conditions are needed for stable urban flood modeling, especially with high-resolution data. We will also show the performance of urban flood modeling with additional features such as adaptive time steps and GPU parallel computation. Finally, we will discuss how CA-based approaches can be efficiently integrated with physical and deep learning-based models to improve flood and hydrological predictions in urban areas.
HS22-A020
A Novel Approach for Image-based Rainfall Estimation with GAN and VAE: Focusing on Rainstreak Detection, Removal, and Generation
Jongyun BYUN, Hyeon-Joon KIM, Jinwook LEE, Jongjin BAIK, Ki-Hong PARK, Changhyun JUN#+
Chung-Ang University, Korea, South
In this study, a novel approach is proposed to estimate rainfall amounts from actual rainfall image datasets obtained by surveillance cameras. Here, basic characteristics of rainstreaks in a CCTV video are mainly investigated to find how to deal with rainstreaks’ information in terms of rainfall estimation with high accuracy. We selected two observation sites (i.e., Seoul and Jincheon) in Republic of Korea and used datasets obtained by rain gauges, disdrometers, and CCTVs from 1st March to 31th December 2022. At first, background subtractor algorithms (e.g. K-nearest neighbors (KNN), Gaussian Mixture-based Background/Foreground Segmentation Algorithm (MOG2)) were exploited to extract the rainsteak from CCTV raw data. Secondly, generative adversarial networks (GAN) and variational autoencoders (VAE) were applied to generate rainstreak datasets based on the extracted actual rainstreak data at the prior stage. The generated rainstreaks’ information were analyzed and compared under different experimental conditions such as initial values in the considered CCTV device (e.g., shutter speed, depth of field), rainfall parameter (e.g., drop size distribution, fall speed), and image background subtraction methods (e.g., KNN, MOG2). As results, it indicates that the GAN model has the advantage of being able to generate more realistic images and the VAE model has the advantage of learning in structural and effective latent space which enables the encoding of meaningful transformation in image data. It is also expected that the proposed approach with a generative model can be a fresh alternative in the field of rainfall estimation from characteristics of rainstreaks in image datasets. [Acknowledgement] This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2022-01910 and this work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. NRF-2022R1A4A3032838) and this work was funded by the Korea Meteorological Administration Research and Development Program under Grant RS-2023-00243008.
HS25-A002
Environmental Issues in the Mekong Delta: Drivers, Consequences, and Management Outlooks
Edward PARK1#+, Duc Dung TRAN2,1, Huu Loc HO3
1Nanyang Technological University, Singapore, 2National Institute of Education and Earth Observatory of Singapore, Singapore, 3Asian Institute of Technology, Thailand
The flow of the Mekong is contributing to the delta’s richness and diversity of ecosystem services. Besides providing obvious ecosystem services such as water provision and natural soil fertilisation, the Mekong Delta (MD) also provides less obvious, but nonetheless, important services including protection against storm surges and carbon sequestration. However, the MD, like many mega deltas worldwide, has been constantly threatened by human activity on multiple geographical scales: (i) local: sand mining and groundwater extraction; (ii) trans-boundary: dam construction; and (iii) regional to global: climate change-induced salinity intrusion and sea-level rise. These environmental stressors have rendered critical threats toward various important ecosystem services of the MD, greatly affecting agricultural productivity and the livelihood of millions of inhabitants. In this article, we provide an overview of the current environmental issues plaguing the MD. Among the many issues (Arias et al., 2019), we focus on four of the most critical environmental challenges in the MD (sand mining, land subsidence, dam construction, and sea-level rise), and provide a review of their causes and environmental consequences. Management implications for the delta include transboundary water diplomacy, halting the sinking delta, and promoting sustainable agricultural practices.
HS25-A003
Uncertainty in Projected Agricultural Water Demand in the Ganges Delta of Bangladesh
Sonia Binte MURSHED1#+, Homin KIM2, Jagath KALUARACHCHI3
1Bangladesh University of Engineering and Technology, Bangladesh, 2Freeport-McMoRan, United States, 3Utah State University, United States
Understanding the climate change effects on agricultural water demand is crucial for the Ganges Delta of Bangladesh, which is an agriculture-dominated region. Evidence shows a decrease in agricultural land and loss of soil fertility in the region due to water scarcity, floods, droughts, and salinity intrusion. These concerns are the basis for this study to understand the potential impacts on future agricultural water demand under climate change. We used projected climate data (2020-2100) of three regional climate models along with their eight driving global climate models with moderate and high carbon emission scenarios (RCP 4.5 and 8.5). The analysis is used to assess the changes in climatic parameters, water loss, crop water requirement, irrigation water need, and freshwater availability. Random forest algorithm is used to predict future land cover data, and a complementary relationship model is used to estimate actual evapotranspiration. Crop water requirement is estimated and compared with freshwater availability to assess agricultural sustainability. We found high uncertainty among different climate model scenarios. A mean increase of 2 to 3°C temperature during the dry season is expected while rainfall shows a fluctuation pattern over time Although we found the possibility of decreased wet season rainfall up to 500 mm, there is also the possibility for opposite scenarios. In essence, the results suggest a wide uncertainty of rainfall and associated impacts. Therefore, irrigation water need is expected to increase by 18% to 60% from the historical (2001-2015) mean. Such an increase can seriously affect other water uses such as domestic, industries and in-stream. Quantifying uncertainty is therefore essential to develop adaptation plans to combat climate change effects. The findings of this study are helpful to develop economically feasible agricultural water management plans.
HS25-A009
Identification of Agricultural Drought-flood Abrupt Alternation Events in the Middle and Lower Reaches of the Yangtze River
Si CHEN#+, Peng HAN
Hubei University, China
The drought-flood abrupt alternation (DFAA), as an extreme event that coexist with drought and flood, is a serious natural disaster that poses a great threat to water resources and food security. At present, there are no unified definitions for DFAA, and its evolution characteristics are under study. In order to investigate the agricultural DFAA events and figure out the monitoring method, this study proposed the standardized soil moisture index (SSMI) based on the root zone soil moisture data from the Global Land Data Assimilation System from 1951 to 2020, and was used as the index to detect the onset/determination and turning point of the DFAA events in the middle and lower reaches of the Yangtze River. The detection accuracy was verified with historical recorded disaster data and the spatial and temporal evolution characteristics of agricultural DFAA events were analyzed. Results indicated that the SSMI exhibited an accuracy of 50%-62% in full detection of agricultural DFAA events in the study area. The observed events have gradually expanded and shifted southward since the 1950s. The frequency of DFAA events showed an increasing trend, with drought-to-flood events occurred mostly in the north-central part while flood-to-drought events occurred mostly in the south-central part. It was found that most of the moderate and severe DFAA events were concentrated in Anhui, Hubei and Zhejiang Province. The historical DFAA events mainly occurred during May to August, while drought-to-flood events occurred more frequently in June and July, and flood-to-drought events occurred more frequently in May and August. This study focused on the monitoring of DFAA events based on agricultural conditions and is expected to provide scientifical decision support for local water resources management.
HS25-A014
Study on Economic Game Logic of Groundwater Overexploitation
Chunfeng HAO#+
China Institute of Water Resources and Hydropower Research, China
To deal with significant decline of groundwater table along with eco-environment degradation in most regions of North China in past decades, China government has carried out a series of countermeasures on comprehensive treatment of groundwater overexploitation. The paper studies on the economic game logic of groundwater overexploitation by quantitatively analysis the actual benefits and losses with overall consideration of eco-environment and socio-economic systems to illustrate the institutional defect accounting for continuous ecological damage and the necessity of eco-environment value assessment in the check-up system of local government. Taking Fenhe river basin as an example, the second large sub-basin of the Yellow river in North China, the direct economic benefit of groundwater overexploitation is 12.0 billion yuan, the direct socio-economic loss is 846 million yuan, the indirect socio-economic loss is 116 million to 491 million yuan, and the ecological service value loss is 15.3 billion to 38.3 billion yuan. The net socio-economic benefit of groundwater overexploitation is as high as over 10 billion yuan, that’s why people prefer more groundwater exploitation in the past. However, by considering the eco-environmental impacts, the overall benefit becomes negative for local eco-environment and socio-economic systems. The loss of groundwater overexploitation is 27.6~164.6 yuan per cubic meter, over twice of the apparent socio-economic benefit. The efforts for effective treatment of groundwater overexploitation should be made from both administrative and market sides for a long-term mechanism by comprehensive assessment of local water resources management.
HS27-A007
Anthropogenic Activity Forcing Has Significantly Influenced Snowfall Changes in Eurasia
Wenqing LIN#, Han WANG+, Weiqi WANG, Dawei ZHANG, Fan WANG, Wuxia BI
China Institute of Water Resources and Hydropower Research, China
This study investigates the influence of external forcings on the various grades of snowfall (including light snowfall (<2.5 mm/day) and instense snowfall (>5mm/day)) over the Eurasian continent. Based on the phase 6 of the Coupled Model Intercomparison Project (CMIP6) multi-forcing dataset and regularized optimal fingerprint method, the detection and attribution of snowfall changes in Eurasia were carried out. Results show that All-forcing (ALL), anthropogenic activity forcing (ANT) and greenhouse gas forcing (GHG) well reproduced the spatial-temporal characteristics of snowfall. The influence of ANT on the changes in annual snowfall, light snowfall and its days over the Eurasian continent could be detected at the 90% confidence level. Moreover, the decreases of snowfall days and light snowfall also could be detected in GHG at the 90% confidence level. Thus, anthropogenic activities may considerably account for the decreases of snowfall days and light snowfall, wherein the GHG plays a dominant role. However, GHG underestimated the changes in snowfall days and light snowfall. Compared with observation, ALL, ANT and GHG significantly overestimated intense snowfall and its days, and couldn’t detected changes in them, which may be related to the low capability of models in simulating high levels of snowfall; thus, further improvement is needed.
HS27-A012
Complex Large-Scale Global Optimization based on Sea Anemone Optimization Algorithm
Xiaolong WANG1#, Guocheng AN1+, Dan WANG1, Qiang MA2, Philippe GOURBESVILLE 2
1Artificial Intelligence Research Institute of Shanghai Huaxun Network System Co., LTD., China, 2China Institute of Water Resources and Hydropower Research, China
Intelligent bionic optimization algorithms can effectively solve complex multimodal optimization problems compared with traditional optimization algorithms. In the paper, based on the anemone algorithm, the principle and effect of its application in complex optimization-seeking problems are investigated; it simulates anemone competition processes: covering, reproduction, convergence, exploration and elite processes. Its process and theory are discussed in detail, and the convergence process of the algorithm is explored. Based on the complex optimization problem test, the effectiveness of the anemone algorithm in solving complex optimization problems is verified. Thus its can be effectively applied in the optimization of parameters of hydrological model, etc., and it also has a wide range of application prospects in the remaining fields.
HS27-A016
Development of Flash Flood (Road Inundation) Real-time Monitoring and Response Technology Using AI
Hui-Seong NOH#+, Cheonkyu CHOI
Korea Institute of Civil Engineering and Building Technology, Korea, South
Flood damage is increasing as the frequency and intensity of torrential rains and typhoons increase due to global warming. In particular, in terms of road flooding, it is necessary to shift away from the post-processing system centered on 'recovery-compensation' to a proactive disaster response system through 'prevention-response-management'. This study aims to solve local issues related to flood damage targeting Jinju-si, Korea, with 'real-time road flood prediction, monitoring and operation technology', which can be the foundation technology for road flood-related disaster policies. It consists of empirical studies that combine various technologies such as flood analysis using rainfall prediction data, AI-based real-time monitoring using CCTV images, flood information based on spatial big data, and e-SOP.
ACKNOWLEDGEMENT
Research for this paper was carried out under the KICT Research Program (project no. 20230174-001, Development of Prediction and Monitoring Technology for Road Inundation based on Artificial Intelligence) funded by the Ministry of Science and ICT.
HS27-A022
Study on the Outburst Flood of Mazbach Ice Lake Based on Remote Sensing
Wei QU1#, Shuai LI2, Yuan YAO3, Tingting ZHANG2, Juan LU1, Changjun LIU1, WenlOng SONG4, Wenjing LU5+
1China Intstitue of Water Resources and Hydropower Research, China, 2Shenyang Agricultural University, China, 3North China University of Water Resources and Electric Power, China, 4China Institute of Water Resources and Hydropower Research, China, 5IAHR, China
In order to reveal the characteristics of the outburst flood of Mazbach Lake, the bottom topography of Mazbach lake was extracted based on the cartographic satellite data, and the water area changes before and after the ice lake outburst were extracted using the GF satellites and Sentinel-2 satellites. At the same time, combined with the water area - ice lake storage curve drawn based on the lake topographic data, the burst flood volume of the Mazbach Lake was calculated. Based on the flood volume, the HEC-RAS model is used to simulate the evolution process of the ice lake outburst flood, and the characteristics of the Mazbach lake outburst flood are analyzed.
HS27-A025
Assessment of Wave Runup on Seawalls in Southwestern Taiwan
Yun-Ta WU#+, Hsiao-Chu HUNG
National Cheng Kung University, Taiwan
Understanding wave runup process has been an important issue in designing coastal structures since it is highly related to coastal flooding. Taiwan is vulnerable to the pathways of typhoons from the Western North Pacific. To withstand the impacts from typhoon-induced long waves, more than half of Taiwan’s coastline has been protected by artificial structures, such as seawalls, indicating the urgent need for efficient and accurate estimates of wave runup on structures. In Taiwan empirical runup formulas developed by the US or European countries are frequently used to estimate the runup height levels. Since these runup formulas are not specifically designed for the coasts in Taiwan, additional correlation parameters should be applied. Having said that, these correction values are in general manually tuned for different locations. In this study, the main aim is to develop an integrated framework for estimating runup heights in the southwestern coasts of Taiwan. A new empirical runup formula has been developed which unifies the runup prediction capability for solitary waves, regular waves and irregular waves on uniform slopes. This new runup formula is then used to compare with those of field observed runup data during typhoon events on three seawalls in Southwestern Taiwan. Existing empirical runup formulas which have been frequently used are also used to compare with the present estimates and in-situ runup measurements. The comparisons indicate that the present runup model shows a higher value of index of agreement than the other empirical formulas. Since the present framework is essentially based on empirical formulas, it can serve as a quick estimation of wave runup and can be then utilized and optimized for nationwide applications in Taiwan.
HS28-A001
Research on Combining Mixed Reality Technology and Fracture Propagation Process by the Hybrid Domain Finite Element Model in Fractured Rocks
Chuen-Fa NI, I-Hsien LEE#+
National Central University, Taiwan
Fracture is the dominant pathway for groundwater flow and solute transport in fractured rock, and it plays an important role in the field of geology and engineering. Hydraulic fracturing is one of the methods for increasing the fractures and has been well-developed in these decades, however, it still has a serious of challenges to realize the fracture propagation mechanism by numerical method. Fracture tip displacement is one the mechanism for fracture propagation which influences the strength and hydraulic conductivity of geological medium and it is a critical issue for engineering. Mixed Reality helmets and the metaverse concept will be utilized to achieve synchronous/asynchronous operation and display by sharing virtual reality. The aim of this research is to review important issues such as fracture propagation, derivation of hydraulic-mechanical coupled numerical model, development of grid generation for fracture propagation unstructured, hybrid domain groundwater flow and transport simulation in fractured rocks, and combine with multi-person mixed reality technology and other important topics.
HS28-A002
Feasibility Study of Floodplain Dredging Using SRH-2D
Tzu Chieh SU#+, Weicheng LO
National Cheng Kung University, Taiwan
River sedimentation may impact hydraulic structures; in turn, threaten life and lead to loss of property. Therefore, river dredging and rectification are crucial for safety issue. However, traditional dredging methods are time-consuming and labor-intensive, as well as do not always work for all conditions. In addition, to protect the coastline from erosion, it needs to maintain sediments in estuaries. In this regard, the Sixth River Management Office has proposed a plan to disturb sediments in the floodplain; accordingly, they can be carried downstream during the event of high flow or reservoir recharge. This study thus aims to evaluate the feasibility of this proposed method by using the two-dimensional hydraulic sediment transport model, SRH-2D (Sedimentation and River Hydraulics – Two-Dimensional), developed by the Taiwan Water Resources Agency and the U.S. Bureau of Reclamation. Our numerical study reveals that Sections 78 to 88 of the Zengwen River are the suitable dredging locations to disturb the sediments. The influence of disturbance depth on dredging effectiveness to move the amount of sediments is quantified, providing a useful reference for future dredging projects. Typhoon Megi in 2016 is selected as the illustrative example for the high flow event. Our results show that the left bank of Sections 80 to 84 are acted on by greater shear stress, making them to serve as the appropriate dredging location. Additionally, we identify the optimal disturbance ranges and depths to maximize the dredging effectiveness, evidently implying that the proposed dredging method is feasible.
HS28-A012
Effective Pumping Scenario for Irrigation Reservoir : Case Study in Deasa
Jong Hyun PARK+, Hyunuk AN#
Chungnam National University, Korea, South
The water used for irrigation which comes from agricultural reservoirs should be ideally sourced from the reservoirs’ adjacent watershed areas. However, in situations that prevent regular collection methods, such as droughts or watershed areas become limited, water used for irrigation must be collected from alternative sources. In South Korea, 273 agricultural reservoirs are operated in conjunction with pump enabled facilities. Using regional characteristics, the aforementioned reservoirs perform water balance analyses which determine optimal levels of water supply. However, data collection is a challenge in Korean pump enabled facilities as storage rate data is usually only information available. Other important data, such as the amount of water supply and its effectiveness, is rarely collected or measured. To achieve efficient use and secure of water in agricultural reservoirs, it is crucial to analyze the effectiveness of pumping scenario and to prepare countermeasures for future events. In this study, meteorological data of 29 years (1991-2019) and water supply data from Daesa Reservoir which has been utilizing pumped-storage since 2016, were used to evaluate the water supply capacity. Comparing the water balance before and after utilizing water pumped storage, the water balance before pump storage was only 128 ha which is smaller than the irrigated area of 163ha. Scenario-based analysis was conducted by considering water supply amount, water supply period, year-end reservoir storage, and normal/drought year periods showed that the pumped-storage of water could increase the stored water volume by up to 10 and 62Mm3, depending on the scenarios.
HS28-A016
Assessment of the Embedded Risk Associated with the Daily Precipitation Dataset Over India
Neha GUPTA#+
Indian Institute of Technology, Ropar, India
In a country like India, changing climate has contributed to increased extreme precipitation events causing extensive damage to humans and nature. Changes in extreme precipitation have been investigated by examining the tail heaviness of daily precipitation datasets using different scalar and graphical methods. However, little is known about the actual tail risk associated with these extremes, especially among different climate types. This study shows the utility of a simple empirical risk function that provides a single concise value after analyzing the risk dispersion in tails, which host the extremes. Concentration Maps are developed to assess the risk attached to any dataset with respect to its right tail. Risk embedded into the tails is evaluated for the historical time period (1951–2019) over India, using a daily gridded precipitation dataset from IMD with a resolution of 0.250. A climate type is assigned to each grid based on a Köppen-Geiger (KG) climate classification system for which the embedded risk associated with daily precipitation datasets has been examined. Grids associated with the Tropical (BWh) followed by Polar (ET) had the most frequent and largest magnitudes of extreme precipitation as the tail risk are higher in these climate types. Proper risk estimation and assessment of extreme climatic events in a region-based framework are necessary for formulating effective response measures to cope, resist, and recover from the severe impact of extreme events in changing climate.
HS28-A017
Evaluation of Two High-resolution Soil Moisture Reanalysis Products Over Major Land Areas of China
Hongmei XU1#+, Qiuling WANG2
1China Meteorological Administration, China, 2National Climate Center, China Meteorological Administration, China
Soil moisture (SM) is one of the most important parameters of the boundary layer. In this study, the China Meteorological Administration Land data assimilation system (CLDAS) SM product, the Global Land data assimilation system (GLDAS) SM product are compared with observations from national automatic soil moisture stations. The results indicate that, (1) for 0~10cm and 10~40cm soil moisture, CLDAS outperforms GLDAS in all regions, with higher correlation coefficient and smaller root mean square error (for 0~10cm soil moisture, the COR of CLDAS in China Ⅰ to China Ⅴ is 0.94, 0.93, 0.91, 0.96 and 0.86, while the COR of GLDAS in the five regions is 0.64, 0.81, 0.75, 0.80 and 0.41; for 10~40cm soil moisture, the COR of CLDAS in China Ⅰ to China Ⅴ is 0.97, 0.88, 0.91, 0.97 and 0.82, while the COR of GLDAS in the five regions is 0.39, 0.75, 0.85, 0.35 and 0.61); (2) for 40~100cm soil moisture, CLDAS outperforms GLDAS in other regions except the southwest; (3) from the perspective of seasonal change trend, the two datasets are close to the observation of 0~10cm and 10~40cm in late summer and early autumn, but seriously overestimated in winter, meanwhile, for 40~100cm soil moisture, CLDAS can more accurately grasp the seasonal change trend, and GLDAS is seriously dry. Based on the evaluation results, it is helpful for researchers to select appropriate datasets for disaster monitoring and early warning, water and energy interaction research, and agro-meteorological modeling.
HS28-A018
Effect of Channel Adjustment on Sediment Transport
Yan-Pei HUANG#+, Weicheng LO
National Cheng Kung University, Taiwan
Sediment siltation in rivers often causes the instability of flow channels and aggravates their narrowing and deepening. Channel dredging is conventionally carried out in engineering practices to solve this problem. In Taiwan, dredging projects are often combined with soil and sand auctions, which usually fail due to the poor quality of riverbed sediments since they are customarily not useful for infrastructure construction. However, the problem of sediment siltation is urgent. Channel adjustment is another method for dredging, by altering the targeted channel section to guide the flow path to retreat back to the center of the channel. This is able to avoid the flow path towards the riverbank to damage its foot. In this study, the Sedimentation and River Hydraulics – two-dimensional model (SRH2D) is applied to conduct a moving bed analysis for the meandering river section from the downstream of the Danei Bridge to the upstream of the Zengwen Bridge, where is a S curve channel; the right bank is convex and then becomes concave. Our numerical model is established according to the digital elevation model (DEM) of the study area before and after river adjustment. Field river section-depth measurements implemented from 2011 to 2016 are applied for model calibration, while model verification is performed based on the remaining five-year measurements from 2017 to 2021. Variations in river roughness due to channel adjustment is indeed taken into account in our numerical calculation. Our results show that after channel adjustment, only a small amount of siltation occurs in the front section of the left bank because the flow path becomes stable and no longer towards the riverbank. Furthermore, erosion takes place mainly in the main channel alone. However, as simulated time increases, erosion tends to be towards the left bank and the erosion area accordingly becomes wider.
HS28-A024
Lagrangian-based Catchment-scale Rainstorm Frequency Analysis
Haochen YAN1+, Mingfu GUAN2#
1University of Hong Kong, Hong Kong SAR, 2The University of Hong Kong, Hong Kong SAR
Rainstorm frequency analysis is a fundamental procedure to learn about the characteristics of regional climate extremes for subsequent flood modeling, structure design, and risk analysis. Conventionally, rainstorm frequency analysis mainly relies on point observations of gauge stations under an Eulerian framework, i.e., the rainstorm intensities of a certain return period and a certain duration are calculated separately and statically in space. However, a significant portion of extreme rainfalls in southeast Asia is contributed by convective systems. Due to the spatial and temporal variability in each rainstorm event, a homogeneous rainfall pattern over the entire catchment can lead to spurious results of flood simulation. Besides, widely used interpolation techniques assuming the same exceeding probability among the relevant stations during an individual event also cause considerable errors, particularly for larger catchments. Despite an areal adjustment factor or the concept of regional frequency analysis can be incorporated, the spatial variability is only depicted in a statistical sense, and the temporal lagging effects induced by the storm evolution across the catchment are still omitted. Motivated by the issues mentioned above, our recent study aims to explore a new method for frequency analysis from the Lagrangian perspective, taking Hong Kong and its periphery as an example. The spatiotemporal statistics of individual rainstorms that appeared within the study domain are first extracted by a state-of-the-art tracking algorithm incorporating the Karman Filter method, based on a high spatiotemporal-resolution gridded dataset with a long time span (>20 years). The core intensities, mean transit speed and directions, dimensions, and life cycle, are considered to fit probability models under a Bayesian-copula-based framework. The disparities of spatiotemporal features obtained by the proposed Lagrangian-based approach against the Eulerian-based approach are elucidated; the associated consequences in flood modeling are discussed. Our study provides new insights and alternatives for regional rainstorm frequency characterization.
HS28-A027
Estimation of the Spatial Distribution of the Internal Density of River Embankment by Exploration Technology Using Cosmic Ray Muon
Keigo NAMIKAWA1#+, Naoki KOYAMA1, Taro KUSAGAYA2, Keiichi SUZUKI3, Tadashi YAMADA1
1Chuo University, Japan, 2NEC Corporation, Japan, 3Kawasaki Geological Engineering Co., Ltd., Japan
River embankments have been constructed and reconstructed to resist extensive damage due to failure. However, the soil materials and compaction methods used have varied over time, which can cause localized voids and land subsidence that can lead to failure. Therefore, it is very important to know the presence and location of low-density and weak areas inside embankments. There are few ways to detect them. For example, Geophysical exploration has been used to estimate inside of ground, but conventional methods do not provide information on ground based on its physical properties and require specialist skills and knowledge to estimate extent of weak points and to interpret the results. In this study, the aim is to study the effectiveness of exploration technology using cosmic ray muon for understanding the internal structure of embankments, which can directly determine the ground density and are suitable for the scale of embankment exploration (spatial resolution 0.1-1.0 m, exploration depth 1.0-10 m). To verify the validity of exploration using muon, the number of muons through the embankment is observed. To visualize the internal density distribution internal of the embankment, a tomography analysis was carried out in a way that the analytical values were independent of the initial values. The results of the analysis show that the analyzed density values internal the embankment generally agree with the actual embankment ground density data. Furthermore, the high-density areas representing the concrete are clearly visible. To improve the accuracy and resolution of the tomography analysis, a few cases of simultaneous observation by many muon detectors were executed. The results show that as the number of measurement points is increased, the analysis grid becomes smaller, and the high-density and low-density regions can be identified in more detail.
HS29-A001
A Study on the Optimal Design of Low-impact Development Technology Using K-LIDM
Joowon CHOI#+, Soonchul KWON, Youngsu JANG
Pusan National University, Korea, South
The collapse of urban water circulation systems is increasing due to the increase of impermeable layers due to urbanization. In particular, damages such as flooding in cities are occurring due to the increase in extreme rainfall and changes in rainfall patterns due to the global climate crisis. To solve these problems, the water management paradigm is changing from water supply, backwater and sewage maintenance to water circulation and water-sensitive cities for sustainable urban development and greening. In particular, the need for application to Low Impact Development (LID) for the restoration of the natural water cycle was emphasized. In this study, a study was conducted on the optimal design of low-impact development technology according to the flood management goal for the Korea GI&LID Center in Pusan National University Yangsan Campus. Results were derived through runoff hydrograph analysis using the K-LIDM model using scenarios such as the area of low-impact development technology for the center's disaster prevention performance.
HS29-A004
Impacts of the Environmental Changes on the Groundwater Contamination Potential
Sheng-Wei WANG#+, Yen-Yu CHEN, Chih-Yu LIN
Tamkang University, Taiwan
Groundwater is an important water resource in Taiwan. The hydrological events, industrial development, water resource depletion, and land use have caused variations in groundwater quality. The hydrological factor of rainfall and anthropogenic factor of land use are adopted in this study to evaluate the influence of environmental changes on groundwater quality characteristics. Since the unneglectable social-economic development of Taoyuan city may cause stress on groundwater quality, 20 years of monitoring data was collected, including the temperature, rainfall, land use, and groundwater quality. According to the results of the hypothesis test, a significant difference in rainfall, temperature, groundwater organic carbon, pH, and iron was found between dry and wet years. Per wet years, the positive correlations between rainfall, temperature, redox potential were determined by factor analysis. Frequently surface recharge caused oxygen infiltration and subsequence oxidative reactions in wet years. While the positive correlation among the rainfall, temperature, sulfate, and magnesium in dry years shows that mineral dissolution dominates groundwater characteristics. Moreover, the groundwater quality index (GWQI)was adopted for understanding the groundwater quality variation within 20 years. The results showed that the groundwater contamination potential in the first decade is higher than that in the last decade. Based on the distribution of GWQI by geostatistical analysis, the high potential area is different in two decades. The aggregation between contamination potential distribution and land use by applying the local indicators of spatial association (LISA). 20.7% decrease in high potential area and 4.5% increase in low potential presented the groundwater quality is gradually better. The process of urbanization limited industrial development and possible groundwater contamination. Groundwater recharge will be more significant in the future via extreme hydrological events, and the adjustment of land use of industry and agriculture in the high potential area will be an applicable adaptation to climate change.
HS29-A027
Optimal Reservoir Operations for Water Supply Under Forecast Uncertainty in Korea
Yeonju KIM#+, Young-Oh KIM, Joohyung LEE
Seoul National University, Korea, South
The Ensemble Streamflow Prediction (ESP) technique, which is the most widely employed statistical hydrological forecasting method under uncertainty, is designed for the water resource management since the 1940s, and it is actively applied to reservoir optimization around the world. Unfortunately, despite the hardship of obtaining forecast distributions, dam operation plans are being planned harnessing only single values of forecast such as the average or median, rather than the entire distribution, for operational convenience. This study aims to purpose a method of managing the water resources by utilizing the probability prediction distribution by itself, rather than the mean or median, and to show its effect on it. To this end, 21 multi-purpose dams in Korea were calculated according to the ratio of annual average inflow to total storage capacity (r). Then Dam Jangheung (JH, r = 0.8) and Dam Chuangju (CJ, r = 1.8) were selected as the subjects of the study among them. In addition, operating rules in response to the forecast distribution were derived by Stochastic Dynamic Programming (SDP), which can explicitly use the streamflow distribution. Since water supply is the most prioritized over other purposes for multi-purpose dams in Korea. The objective function was set to minimize the difference between the water supply and demand. The operating rules derived from this were simulated and the effect was evaluated through the reliability, resiliency, and vulnerability criteria. As a result, even the distribution of forecasts with the same average tended to release more conservatively as the variance increased. Through this study, it was shown that it is more reasonable to manage water resources utilizing distributions themselves rather than only the representative values. Furthermore, to obtain the distribution of this forecast, the utilization of ESP, which can perform statistical hydrological predictions, was also shown.
IG01-A001
Development of a Hydrogeological Apparent Model for Choushuichi Alluvial Fan by Integrating Geophysical Exploration Measurements and Machine Learning Analysis
Ping-Yu CHANG#+, Jordi Mahardika PUNTU
National Central University, Taiwan
This study aims to develop a hydrogeological apparent model for Choushuichi alluvial fan by integrating geophysical exploration measurements and analyzing them with machine learning methods. The apparent model is an advanced technology that can substitute traditional conceptual models and provide a more accurate representation of subsurface hydrogeological conditions in the area. The study involves collecting geophysical exploration measurements, including borehole resistivity logs, electrical resistivity, and transient electromagnetic survey data, from the target area. These measurements will be analyzed using machine learning algorithms and borehole core records to extract relevant information about subsurface hydrogeological conditions. The information will be integrated to create an apparent model that can be used to predict subsurface sediment distributions. The results of this study will demonstrate the potential of the hydrogeological apparent model as a powerful tool for understanding subsurface hydrogeological conditions. By using machine learning methods, the apparent model can provide a more accurate and detailed representation of subsurface conditions than traditional conceptual models.
IG01-A002
Hydraulic Properties Evolution Caused by Pore Clogging from ISCO Injection
Bing-Shiun KE#+, Jui-Pin TSAI
National Taiwan University, Taiwan
ISCO (in situ chemical oxidation) is one of the most frequently used soil and groundwater remediation approaches. However, three popular ISCO amendments, Potassium permanganate, Fenton’s reagent, and Sodium persulfate, usually cause pore-clogging due to the formation of precipitation, leading to a decrease in hydraulic conductivity (K). In other words, pore-clogging due to ISCO amendment injection changes the spatial distribution of K, causing a change in the flow paths of amendment and plume. To quantify the spatial change in K, an advanced hydraulic test, hydraulic tomography (HT), can be a useful tool to delineate the spatiotemporal evolution of the K field. In this study, we conduct a sandbox experiment with Fenton’s reagent injection. HT is employed to quantify the spatial change in K, and the soil cores were sampled at the place where K was significantly reduced. Inductively coupled plasma-optical emission spectrometry is also used to measure the increase in Fe(III) in the soil samples. The results show that the concertation of Fe(III) was raised in the areas with decreased K values after injection. The results reveal that HT is the appropriate method for delineating spatiotemporal K fields during the ISCO remediation. This study can benefit the study related to hydraulic – geochemical studies, especially valuable for those related to groundwater remediation.
IG01-A003
Using Signal Analysis and Light Gradient Boosting Machine to Analyze Groundwater Levels of Choushui River Alluvial Fan in Taiwan
Tzung-Hsin TSAI+, Shien-Tsung CHEN#
National Cheng Kung University, Taiwan
This study applied signal analysis on the groundwater level in Choushui River Alluvial Fan in Taiwan. The wavelet analysis and independent component analysis were used to extract principle component information of groundwater level. Moreover, the correlation between the groundwater level and other hydrological variables (rainfall, pumping data, and river flow) were also analyzed by using the signal analysis. Analysis results exhibit that these signal analysis techniques can reveal the interaction of groundwater level with other variables, and can contribute to the understanding of groundwater level variation in the study area. In addition, this study applied the light gradient boosting machine (LGBM) to develop a prediction model for short-term prediction and long-term projection of groundwater level. The LGBM is capable of processing large data sets and category characteristics to build a groundwater level prediction model for the study area. The signal analysis results were used to improve the input selection of the groundwater level prediction model. The prediction performance for one-month lead time is satisfactory in terms of correlation coefficient and efficiency coefficient. Climate change scenarios of SSP2-4.5 and SSP5-8.5 were used to perform long-term projections for the future short-term (2021 to 2040) and mid-term (2041 to 2060) groundwater levels.
IG01-A006
Hydrogeological Investigation using the Transient Electromagnetic Method
Lingerew Nebere KASSIE1+, Ping-Yu CHANG1#, Jun-Ru ZENG1, Hsin-Hua HUANG2, Chowson CHEN1, Yonatan Garkebo DOYORO1, Ding-Jiun LIN 1, Jordi Mahardika PUNTU 1, Haiyina Hasbia AMANIA 1
1National Central University, Taiwan, 2Academia Sinica, Taiwan
We used Transient Electromagnetic (TEM) to map the hydrogeological structures in the Choushui River Alluvial Fan in Yunlin county of central Taiwan. 63 TEM measurements were collected using the FASTSNAP system with 50x50m in-loop configurations in the middle and distal fan. The 1D model, based on prior information, was constructed from the inverted soundings. Results showed a thin, resistive shallow layer and a 40m low-resistive (6-42 ohm-m) zone beneath it. High-resistive zones (50-170 ohm-m) were found from 50-120m depth, and low-resistive zones were revealed below 120m in some areas. Results were consistent with resistivity and lithology logs from nearby wells. We interpolated resistivity at 10m, 50m, 100m, and 160m depth from the 1D model results to produce a slice map of the area, which indicated variations, trends, and depths of the sediment deposits. The TEM method successfully identified the hydrogeological structures, showing that the upper 40m of sediment acts as a confining layer for the aquifer structure from 50m to 120m depth.
IG01-A007
Characterizing the Hydraulic Heterogeneity of a Contaminated Site in Taiwan Using Hydraulic Tomography and Fiber Bragger Grating Multilevel Monitoring System
Jui-Pin TSAI1#+, Tian-Chyi YEH2, Yen-Te HO3
1National Taiwan University, Taiwan, 2The University of Arizona, United States, 3CITPO Technology, Taiwan
Hydraulic tomography (HT) is a new hydraulic test method for characterizing heterogeneous aquifer properties. We need to perform sequential pumping/injection tests for the HT test, and a group of wells is employed to measure the groundwater pressure variations for every test. The pressure variations are then transformed into aquifer properties using the geostatistics approach. In the traditional HT test, the conventional wells for collecting pressure data often open screens at a single target depth. In other words, a single well can only measure the pressure in one depth range. In contrast, a multilevel well has several open-screen at the target depths. Thus, the number of pressure observations from the multilevel well can be several times more than that of a traditional well. Accordingly, this study employed a new multilevel well system, developed by fiber Bragg grating technology, to conduct HT at a contaminated site in Taiwan. We then compare the estimate with those from depth-average pressure data, which represents the traditional well. The results show that the parameter estimate from FBG multilevel well is better than that of a conventional well. Results also reveal that HT with a multilevel well system benefits HT and has the potential to be the next-generation hydraulic test.
IG01-A009
Evaluation of Hydraulic Control on the Remediation of Groundwater Chlorinated Contamination
Chih-Yu LIN#+, Sheng-Wei WANG
Tamkang University, Taiwan
Groundwater chlorinated organic contamination is a global concerning issue. Biostimulation by injecting organic carbon substrate is an environmental-friendly in-situ remedy. Due to the slow transport of groundwater flow, the concept of groundwater circulation well has been widely applied for increasing the effectiveness of bioremediation. In this study, a groundwater vinyl chloride (VC) contaminated site is collected to simulate the transport and chemical reactions by MODFLOW program with RT3D package. The average hydraulic conductivity and hydraulic gradian are 4.93 m/day and 0.0003, respectively. Three pumping wells with a flow rate of 60 m3/day were set up in the downstream area of this model. Monitoring groundwater levels were used for model calibration. The difference between simulated and observed heads was reduced to 0.45m by Parameter Estimation (PEST). According to the results of model verification, the simulated drawdown and flow velocity coincide with the field measurement. The groundwater velocity increases from 6.11×10-5 m/day to 1.45×10-2 m/day by continuous pumping. Moreover, a significant difference in VC decreased by injecting persulfate between the natural groundwater flow and the hydraulic control scenarios. Advanced persulfate injection with hydraulic control effectively accelerates the degradation of VC plume. The established model can be used as a convenient and fast assessment tool for the design of pumping wells network in the future.
IG01-A011
Making the Invisible Visible: Evaluation of Inter-catchment Groundwater Flow Using Deterministic and Stochastic Method
Hsin-Yu CHEN#+, Hsin-Fu YEH
National Cheng Kung University, Taiwan
The hydrological model, often known as the closed model, typically assumes that there is no groundwater exchange at the boundaries between catchments. Yet, this assumption is rarely satisfied. To assess inter-catchment groundwater flow (IGF), five adjacent catchments in Taiwan's Choshui River Basin were chosen as the study area. The Generalized Likelihood Uncertainty Estimation (GLUE) method and the Shuffled Complex Evolution - University of Arizona (SCE-UA) optimization algorithm were combined in the open lumped rainfall-runoff abcd model to assess groundwater exchange from the stochastic and deterministic perspectives, respectively. To understand whether each catchment was in a gaining, leaking, or isolating state, the open rainfall-runoff model's groundwater exchange parameter (xg) and the effective catchment index (ECI) were utilized simultaneously. For instance, groundwater was received by the Nei-Mao-Pu catchment. The deterministic method estimated the change of IGF over time, and the results showed that the performance of open rainfall-runoff model was superior to the closed model. The stochastic method estimated the possible intervals of IGF at each time step. However, since IGF cannot be measure directly, this study collected additional water balance fluxes and compared the consistency between simulated evapotranspiration and observed evapotranspiration to indirectly verify the justifiability of estimated IGF. In addition, the proportion of IGF to the rainfall was larger in the dry season than in the wet season. This study suggested that groundwater exchange plays a significant role in the hydrological cycle. This study is expected to advance our scientific knowledge of groundwater and contribute to the sustainable groundwater development.
IG01-A013
Hydraulic Heterogeneity Estimation Using Convolutional Neural Network and Hydraulic Tomography
Yukai CHEN#+, Jui-Pin TSAI
National Taiwan University, Taiwan
Hydraulic tomography (HT) is a well-developed approach for estimating three-dimensional hydrogeological parameter fields. The widely used inverse method for HT is the successive linear estimator (SLE). SLE is a well-proved geostatistical method employed in various scale problems. However, SLE’s computational efficiency decreases as the number of parameters and observations increases. To overcome this issue, we propose an HT-based convolutional neural network (HT-NN) to replace SLE for converting head/drawdown data to hydraulic heterogeneity. We developed a two-dimensional groundwater flow model via VSAFT2 to generate large data pairs (head data and K/Ss). These data pairs are then used to train the HT-NN. The results reveal that HT-NN successfully converts the head dataset to K and Ss fields. The values of MAE, RMSE, and R2 of the predicted K field in the validation process are 2.502, 3.269, and 0.623, respectively. Besides, the values of MAE, RMSE, and R2 of the predicted Ss field in the validation process are 0.001, 0.002, and 0.795, respectively. These results reveal that the developed HT-NN can be an efficient tool to accurately delineate the hydraulic heterogeneity and benefit groundwater-related studies.
IG01-A014
Analysis of the Impact Extents of Salinity by Seawater Intrusion in the Geumgang Estuary Using Opengeosys
Hyun Jung LEE1+, Hyung-Ju YOO1, Seung-Jin MAENG2, Seungoh LEE1#
1Hongik University, Korea, South, 2Chungbuk National University, Korea, South
Discharge and water surface elevation in Geumgang estuary are controlled by roller gates to secure living, industrial, and agricultural water in the basin. However, because of mostly operated as the closed estuaries, requests are conflicting in the view of the demand for opening to form a brackish water area and concerns about crop damage due to saltwater intrusion when opened. Currently, 5.0 x 10^6 m^3, which takes 62.2% of the annual groundwater use upstream of the estuary is used for agricultural purposes, mainly for paddy rice. Thus, it is crucial to consider the spatial and temporal extent of seawater intrusion impact. To consider the optimal seawater distribution between making brackish water zone and the minimum seawater intrusion distance upstream, three scenarios were set according to the period and the water level difference with three different numerical models: MODFLOW, FEFLOW and OpenGeoSys. Boundaries of this study area were constructed with a digital elevation model (DEM) with a spatial resolution of 90 m, and water level and salinity data from four groundwater observed stations. Model was verified by obtaining Root Mean Squared Errors of 0.1~ 0.16 m and 0.89 ~ 0.92 of coefficient of determination (R2) between observed groundwater level and predicted values acquired from 2018 to 2022. Then, the model was applied to the Geumgang area to identify the extents of seawater wedge. If meteorological data like temperature, rainfall and tidal level from the Representative Concentration Pathways (RCP) are added to further study, it could be used to predict and prevent the impact of the seawater intrusion from climate change.
IG01-A017
Experimental Study on Non-Darcian Flow and Hydraulic Conductivity Variation Through a Single Fracture
Snigdha PANDEY#+, Pramod KUMAR SHARMA
Indian Institute of Technology Roorkee, India
The groundwater flow rate, in general, varies spatially through the volume of fractured rocks. This is attributed to their fundamental characteristic of spatial variation in hydraulic conductivity. Therefore, the standard methods used for the characterization of porous media hold limited significance in the case of fractured rock aquifer (FRA) systems. The proposed study is aimed to study the influence of geometric and hydraulic parameters on the flow and hydraulic conductivity of a single artificial fracture. A series of laboratory experiments were conducted to simulate groundwater flow through a single rough-walled fracture with 3 mm and 12 mm fracture apertures under unconfined flow conditions. Flow characteristics through fracture were found to be essentially non- Darcian for different flow velocities. Evaluation of Local cubic law further suggested the dominance of inertial terms for the flow. With the increase in aperture size, the gradient of Reynold’s number with average flow velocity was found to increase. The flow-characterizing parameters of the Darcy, Izbash, and Forchheimer models were calculated using nonlinear regression, and their suitability was tested for the prevailing flow conditions. Hydraulic conductivity was found to vary with space for different apertures and hydraulic gradients, mainly due to the surface roughness and induced 2-D torturous flow in the fracture.
IG01-A020
An Integrated Platform for Real-time Groundwater Modeling and Data Visualization
Chuen-Fa NI#+, I-Hsien LEE, Gumilar Utamas NUGRAHA, Thai Vinh Truong NGUYEN, Ping-Yu CHANG
National Central University, Taiwan
The integrated technologies and multidisciplinary knowledge of groundwater have enhanced the understanding of dynamics in groundwater systems. Taking advantage of wide developments in computer sciences and web services, the web platform provides an excellent open environment for groundwater investigations. The study aims to develop an online web-based platform for groundwater data visualization, temporal and spatial data analysis, mesh generation, and flow modeling. The study integrates multiple program languages to bridge the data flow and online visualization. The interactive real-time web environment enables users to screen temporal and spatial measurements on the web map, conduct online data analyses, and develop numerical groundwater models. With a well-designed database and numerous modules for data analyses and modeling, the platform allows users to share data and develop collaborative activities. The built-in analysis tools can also improve the efficiency of groundwater management and decision-making processes.
IG02-A005
What Did We Learn from COVID?
John Barnett GAANO#+, Camille RULE, Jimuel Jr CELESTE, Vena Pearl BONGOLAN
University of the Philippines Diliman, Philippines
We revisit the previous modelling we did, which revealed: a) prioritizing the low-income group in a low-income country might be the better strategy and b) the high cost of vaccine hesitancy. Various improvements were done to the previous model, all calibrated by Philippine data. As Covid nears its fourth year, it now makes sense to add a population’s vital statistics to the model, to make it more responsive to changes in demographics, following through on our previous theory of age-stratification. Hypothetical scenarios such as reinfections and waning immunity were likewise factored in, although these are far from certain due to succeeding outbreaks being caused by different variants. More difficult to catch would be a population’s underlying “genetic vulnerabilities”, i.e., if they are prone to one or more of the known Covid co-morbidities. There is little local data on this, and we might have to rely on international data if they can be reasonably be used as a similar datapoint.
IG02-A006
Vulnerable Communities: Examining the Cost of Forgoing Vaccination in the BARMM Region
Jose Marie Antonio MIÑOZA1#+, Vena Pearl BONGOLAN1, Roselle Leah RIVERA1, Romulo DE CASTRO2
1University of the Philippines Diliman, Philippines, 2University of San Agustin, Philippines
This study examines past research on the BARMM region in the Philippines, an area that was expected to have high vaccine hesitancy. Previous studies found that factors such as low income, low pre-Covid vaccination rates, and poor delivery of services did not greatly affect vaccine allocation methods. The current study examines the impact of school reopening scenarios and finds that regions with low or slow vaccination rates, such as BARMM, were among the last to reduce risks from the ongoing pandemic. This suggests that there may be a cost associated with vaccine hesitancy. The study then utilizes a cost utility function, based on Bayesian Regret, to evaluate the expected reduction in infection and death rates under a scenario of no vaccine hesitancy (optimal strategy).
IG02-A007
Detection of Thermokarst and Vegetation Succession from Multitemporal Satellite Images
Hitoshi SAITO1,2#+, Yoshihiro IIJIMA3, Takashi KIRIMURA4
1Nagoya University, Japan, 2The University of Tokyo, Japan, 3Mie University, Japan, 4Kogakkan University, Japan
Eastern Siberia is characterized by widespread permafrost thawing and subsequent thermokarst development in open natural and anthropogenic landscapes. The thermokarst development affects the hydrological processes, ecosystems, and human society accompanied by vegetation succession and degradation. In the last few years, a satellite constellation system attracted a tremendous amount of interest in acquiring frequent cloud-free images. This study detected the early-stage thermokarst and vegetation succession using multitemporal satellite images of PlanetScope. We focus on the changes in the normalized difference vegetation index (NDVI) of grasslands around the Churapcha area in eastern Siberia. The results showed that the NDVI of grasslands with early-stage thermokarst landforms was higher than that of grasslands without thermokarst development. The differences in NDVI were large during the summer growing season from June to August. Analysis of the time series NDVI over the past 20 years showed an increasing tendency in NDVI in early-stage thermokarst grasslands with a history of anthropogenic land use. These results indicate that increases in soil moisture and soil temperature may affect rapid vegetation growth and succession at the early-stage thermokarst landforms. Further study is necessary to verify the results using field observation over a wide area of eastern Siberia.
IG02-A014
Performance of the Drought Indices in the Different Agricultural Systems
Seonyoung PARK#+
Seoul National University of Science and Technology, Korea, South
Drought has a significant impact on a region's economy, and its severity is determined by the level of infrastructure in the affected region. For adequate assessment and mitigation, it is important to consider not only the conventional environmental properties of drought, but also the infrastructure of the target region. Drought indicators are provided to interpret the various meteorological, agricultural, and hydrological characteristics of droughts. However, because each of these drought indices has its own characteristics, it is difficult to contemplate an adequate assessment of drought impact. In this study, we investigated the applicability of satellite-based drought indices over South and North Koreas, which have different agricultural infrastructure systems. Over the Korean Peninsula, we compared satellite-based drought indices to in-situ drought indices, the standardized precipitation index (SPI), and rice yield. Drought indices were derived for the period from 2001 to 2018 using data from the Moderate Resolution Imaging Spectroradiometer (MODIS), Tropical Rainfall Measuring Mission (TRMM), and the Global Land Data Assimilation System (GLDAS). The performance of the indices in monitoring meteorological and agricultural droughts revealed opposed correlation patterns between the two countries. It is considered that drought impacts differed due to differences in agricultural systems, especially irrigation. The vegetation condition index (VCI) and the evaporative stress index (ESI) are ideally suited to assessing agricultural drought in well-irrigated regions such as South Korea. In contrast, most of the drought indices—with the exception of the temperature condition index (TCI)—are appropriate for regions with poor agricultural infrastructure, such as North Korea.
IG02-A015
Landslide Risk Analysis in Ciletuh Geopark Area, Ciemas Subdistrict, West Java, Indonesia
Qonita Nur SHOFIYAH#, Kemala WIJAYANTI+
Universitas Padjadjaran, Indonesia
Landslide is one of the disasters that often occur in the Ciletuh Geopark area, Sukabumi Regency, West Java Province, because of the rock conditions and topography. This study aims to determine the magnitude of the potential for landslides in Ciemas District, which often occur, to determine the impact of landslides on the environment and people's lives, and to determine ways to reduce the effects of landslides. The methods used in this research are secondary research methods, literature studies, and scoring methods. The data analysis used is in the form of quantitative data analysis with a descriptive approach. Landslide-prone areas in Ciemas District are divided into four categories based on slope parameters, rainfall, bedrock type, soil type, geological structure, and land cover. The four categories are low vulnerability covering 24% of the study area; moderate vulnerability covering 33% of the study area; high vulnerability surrounding 33% of the study area; and very high exposure covering 10% of the study area. Districts with a high level of vulnerability to landslides are Cibenda, Ciemas, Girimukti, Mekarjaya, Mekarsakti, and Tamanjaya Districts. The impact of landslides on the environment and people's lives in Ciemas District is damage to people's houses with severe to light levels of damage, disruption of toll road access, and temporary closure of tourist areas. In addition, mitigation efforts can be carried out in structural and non-structural mitigation. Disaster mitigation that can be done is planting taproot vegetation in areas with grassland land cover and the built-up regions, building gabions in areas with steep slopes, making landslide zoning maps, conducting counselling, and outreach about landslides and their mitigation.
IG02-A019
Stochastic Simulation of Tropical Cyclones for Risk Assessment at One Go: A Multivariate Functional PCA Approach
Chi YANG1#+, Jing XU2
1Beijing Normal University, China, 2Chinese Academy of Meteorological Sciences, China
Tropical cyclones (TCs) are one of the biggest threats to life and property around the world. However, the infrequent nature of catastrophic TCs invalidates the standard actuarial loss estimation approaches. TC risk assessment requires estimation of catastrophic TCs having a very low occurrence probability, or equivalently a very long return period spanning up to thousands of years. Since reliable TC data are available only for recently decades, stochastic modeling and simulation turned out to be an effective approach to achieve more stable TC risk estimates for regions where little or no historical TC records exist. Here we present a novel model for the full-track simulation of TCs for risk assessment, via multivariate functional principal component analysis approach. Elemental variables of TC along the track necessary for risk assessment, such as center coordinates, maximum wind speed, minimum central pressure and ordinal dates, can be simulated simultaneously at one go, using solely the best-track data with no data supplemented from any other sources. The simulation model is optimally determined by means of the ladle estimator. A TC occurrence model using the Conway–Maxwell–Poisson distribution is proposed as well, by which different dispersion features of annual occurrence can be represented in a unified manner. With the occurrence model, TCs can be simulated on an annual basis. The modeling and simulation process are programmed and fully automated such that little manual intervention is required, which greatly improves the modeling efficiency and reduces the turnaround time, especially when newly available TC data are incorporated periodically into the model. Comprehensive evaluation shows that this approach is capable of generating high-performance synthetic TCs in terms of distributional and extreme value features, which can be used in conjunction with wind field and engineering vulnerability models to estimate economic and insurance losses for governments and insurance/reinsurance industry.
IG02-A020
Landslide Preparedness and Response of Selected Communities in the Philippines
Maria Regina REGALADO#+, Decibel FAUSTINO-ESLAVA, Beth Zaida UGAT, Jenielyn PADRONES, Loucel CUI, Juan Miguel GUOTANA, Rosemarie Laila AREGLADO, Bianca Maria Laureanna PEDREZUELA, Jefferson RAPISURA, Gabriel Angelo MAMARIL
University of the Philippines Los Baños, Philippines
Aside from studying the geophysical characteristics of landslides, understanding the perception of the local communities residing in landslide prone areas is a great help in planning for disaster risk management. While planning for engineering-based solutions, risk reduction can also be effective by mainstreaming risk information in communities. However, it is important to determine first the perception of the local communities. To determine risk perception, landslide preparedness and response towards landslide occurrences, household surveys were conducted in the provinces of Benguet, Albay, Sorsogon, and Northern Samar, Philippines. This study also looked into the available sources of landslide information of respondents from the study areas. Results of the survey showed that respondents who think they are prone to landslides are willing to relocate. However, the results also showed that several respondents, despite residing near landslide areas, believed that they are not at risk to landslides. Results also indicated that the top trusted source of information of the respondents are TV, radio, community leaders, and local government officials. While choosing information campaign materials, respondents from Benguet, Northern Samar, and Sorsogon preferred radio and posters, while respondents from Albay preferred radio and videos made available over the internet. The results of the survey have shown varying responses from each of the provinces. Thus, this should be accounted for in determining adequate landslides information and efficient pathways of information dissemination to the different communities.
IG02-A022
Cost-effectiveness of Wind Mitigation Strategies
Ayat AL ASSI#+, Rubayet Bin MOSTAFIZ, Carol J. FRIEDLAND
Louisiana State University, United States
Severe winds cause billions of dollars in annual losses and significant damage to buildings, resulting in economic losses for homeowners. Mitigation strategies beyond minimum building code requirements are essential to improve home quality and resilience. The FORTIFIED home program has effectively minimized wind risk. This study evaluates the cost effectiveness of FORTIFIED's Roof, Silver, and Gold designation levels for new single-family homes using life-cycle benefit-cost analysis (LCBCA) over 30- and 70-year periods. The study includes wind hazard insurance and flood risk reduction. The LCBCA is conducted with and without including the wind hazard insurance considering the flood risk reduction (i.e., average annual loss) as the absolute benefits. Results provide actionable information to stakeholders and simplify the mitigation decision-making process to reduce wind risk.
IG02-A023
Application of FLOW-3D to Simulate Slump-flow Behavior in the Slump Test of Sediment Slurries
Ming-Wei LIAO#+, Chyan-Deng JAN, Tung-Yang LAI, Yu-Chao HSU
National Cheng Kung University, Taiwan
The slump test is used to measure the slump behavior of the test body, and the result is used to evaluate the test-body flow behaviors. In the slump test, the slump and slump-flow speeds are very fast and difficult to record, resulting in only the final slump and spread being recorded. In addition, it is not easy to maintain the same slump-cone lifting speed in the test. In order to improve the problems, this study uses FLOW-3D to simulate the slump test. It is assumed that the test body is a sediment slurry, being a kind of Bingham fluid, of two rheological parameters, such as yield stress and viscosity in this study. Five different test slurries were used in the slump-test simulation, and the results were compared with those by manual slump tests. The measured parameters of the simulation include slump velocity, slump-flow velocity, final slump, final spread, and final time of slump-flow. The simulated results are close to the manual slump-test measurements, with errors of less than 10%. It shows the FLOW-3D software has good applicability in slump tests. These simulations and manual measurements indicated that the slump parameters of the tested slurries are closely related to their rheological parameters. In addition, simulations show that the slump-cone uplift velocity affects the slump behavior, but the impact has an upper limit. After the uplift velocity exceeds a certain value, the slump behavior does not change significantly. It is concluded that the FLOW-3D can be used to simulate the slump test, and the slump parameters so obtained can be used to estimate the rheological parameters of the test slurries. As the slump-cone lifting speed is set to be higher than a certain threshold value in the simulation, the lifting-speed effect on simulation results can be ignored.
IG02-A024
Interpretation of Riverbed Sediment Grain Size Distribution Using UAV Aerial Images Combined With Basegrain Software
Hsiang-Wei CHEN#+, Tung-Yang LAI, Chyan-Deng JAN
National Cheng Kung University, Taiwan
Knowing sediment grain size distribution in the riverbed helps to estimate the sediment transport and morphology of the river. The traditional grain size investigation method is limited by manpower, and cannot carry out large-scale investigation. This study uses the BASEGRAIN software to interpret the riverbed surface grain size from aerial images, and explores accuracy of the interpretations. Indoor experiment was carried out by laying sediment of known particle size distribution on a platform, taking a vertical-view photo, and then using BASEGRAIN software to interpret the particle size distribution. Field photo taking were conducted in Heshe River and its upper reaches in Nantou County, Taiwan. Ten riverbed photos were taken by unmanned aerial vehicles, and high-resolution orthophotos were constructed, and then the BASEGRAIN software was used to interpret the particle size distribution, and the effects of the selected software parameters on interpretations were also discussed. Comparing the interpretation results by BASEGRAIN with those by the traditional line pebble sampling method, the indoor experiment results show that the differences in the index particle sizes D16, D30, D50, D60 and D84 by the two methods are about 29%, 17%, 3%, 5% and 17%, the closer to the median particle size, the smaller the relative error obtained by the two methods. Interpretation results of the field aerial photos show that the difference in D30, D50 and D84 by the above two methods are about 25%, 21% and 30%, respectively. The results of field-photo interpretation may vary greatly due to factors such as terrain undulations, and material stacking and burial. Application of BASEGRAIN can quickly and massively interpret the particle size of the riverbed surface, but there are still some problems in the accuracy of the interpretations, and how to improve the accuracy needs further research.
IG02-A025
Assessment of Rheological Parameters of Debris Flow Sediment Slurry by Using the Slump Test
Fang-Yu CHANG#+, Chyan-Deng JAN, Tung-Yang LAI, Yu-Chao HSU
National Cheng Kung University, Taiwan
The movement behavior of debris flow is related to its rheological properties, and the rheological properties of debris flow are related to its sediment concentration and particle size composition. To master the rheological characteristics of debris flow, it is necessary to obtain sediment materials from the channel bed debris flow to measure its rheological characteristics and related parameters. In this study, debris-flow sediment samples were taken from the riverbed of Jiaopu Creek that is a debris-flow river in Tainan, and brought them back to the laboratory to analyze the particle size distributions of these samples. The samples so obtained were mixed with clean water to form sediment slurries with different volume concentrations for rheological measurements and slump test to obtain rheological parameters and slump parameters, respectively. We analyze the relationship between the obtained rheological parameters and slump parameters so as to understand their relations, and the relations can be used to estimate debris-flow rheological parameters from its slump parameters. The slump test was carried out with debris-flow sediment slurries of different concentrations, and the slump parameters were measured to estimate its rheological properties, so as to evaluate the feasibility of indirectly estimating the rheological parameters from the on-site debris-flow slump test.
IG02-A032
| Invited
The Potential Landslide-induced Tsunamis of Iya Volcano in Sawu Sea
Sakka SAKKA1#, Muh. Alimuddin HAMZAH1, Amiruddin AMIRUDDIN1, Saaduddin 1+, Darmawan HERLAN2, Devy Kamil SYAHBANA3, Ainun Mawaddah ABDAL1, Miswar TUMPU1, Yatimantoro TATOK4, Norman Patrick Lucky Bire Riwu KAHO5
1Hasanuddin University, Indonesia, 2Gadjah Mada University, Indonesia, 3Center for Volcanology and Geological Hazard Mitigation, Indonesia, 4Indonesian Agency for Meteorology Climatology and Geophysics, Indonesia, 5Nusa Cendana University, Indonesia
A comprehensive study should be conducted to evaluate the exposure and risk related to the potential landslide-induced tsunamis in Sawu Sea which could be triggered by the activities of Iya volcano. This is an active volcano located in the coastal area in the southernmost of Ende, East Nusa Tenggara Province in Indonesia. The current Iya’s edifice shows a potential sector collapse as a consequence of the flank instability. Furthermore, this condition could trigger landslide-induced tsunamis in Sawu Sea. This study will reanalyse the existing rupture surface which is considered as the source of the potential landslide-induced tsunamis for the input parameter of tsunami modelling. A finite element method will be applied to model the tsunami generation to numerically solve Navier-Stokes equation for the approach of incompressible flows in a multi-material simulation. The expected outputs are the physical parameters of tsunami such as: run-out distance, run-up, and arrival time to neighbouring islands, Kupang dan Sumba. Further, this study will be equipped with risk vulnerability analysis as the part of risk mitigation for the authorised institutions and the local government.
IG03-A002
Bayesian Seismic Tomography Based on Particle-based Variational Inference in Velocity-space for Physics-informed Neural Network
Ryoichiro AGATA#+, Kazuya SHIRAISHI, Gou FUJIE
Japan Agency for Marine-Earth Science and Technology, Japan
In this study, we consider Bayesian seismic tomography using physics-informed neural networks (PINN). PINN is a recently proposed framework in deep learning that offers enhanced capabilities of physics-based simulations and inverse analyses. PINN-based deterministic seismic tomography incorporates two moderate-sized neural networks (NNs): one to predict seismic velocity and the other to predict travel time. Widely adopted naive approaches of Bayesian neural network fail to handle the high-dimensional space spanned by the weight parameters of these NNs. To address this problem, we propose a novel approach called velocity-space Stein variational gradient descent for PINN-based seismic tomography (vSVGD-PINN-ST). This approach targets only the network predicting seismic velocity in the Bayesian estimation, while the network predicting travel time is used only for deterministic travel time calculations, with the help of the adjoint method. Furthermore, it performs Bayesian estimation for the velocity network by introducing a function-space Stein variational gradient descent (SVGD), which conducts a type of particle-based variational inference in the space of function predicted by the NN (i.e., seismic velocity), but not in the weight space of the NN. These improvements drastically decrease the complexity of the problem and allows for more accurate and physically consistent Bayesian estimation for PINN-based seismic tomography, confirmed by synthetic tests of one- and two-dimensional tomographic problems. Our new approach allows PINN to be applied to Bayesian seismic tomography practically for the first time. In addition, it can be a powerful tool for general PINN-based Bayesian estimation problems associated with similar sizes and formulations of NNs.
IG03-A003
Shrinkage-induced Crack Pattern Formation Based on Variational Energy Physics-informed Neural Network
Shin-ichi ITO#+
The University of Tokyo, Japan
Cracks on the surface of thinly spread dense colloidal suspensions (desiccation cracks) show complicated patterns, and such patterns are observed in various scientific and industrial scenes. Although the numerical simulations of the crack pattern formation are necessary to understand the underlying physics, obtaining accurate crack formations has still been a computationally challenging task due to the scale gap between the crack width and the whole domain of the pattern. In order to tackle this problem, this study proposes a phase-field modeling of the time evolution of the desiccation cracks based on a variational energy physics-informed neural network (VE-PINN) approach. The proposed VE-PINN model enables the computation of crack dynamics in high resolution since it learns and outputs the crack pattern as a spatiotemporally continuous function. The numerical experiments reveal the proposed model shows the rich pattern formations corresponding to the patterns observed in the real experiments.
IG03-A007
U-Net: A Deep-learning Method for Improving Summer Precipitation Forecasts in China
Qimin DENG#+, Peirong LU
China University of Geosciences, China
A deep-learning method named U-Net was applied to improve the skill in forecasting summer (June–August) precipitation for at a one-month lead during the period 1981–2020 in China. The variables of geopotential height, soil moisture, sea level pressure, sea surface temperature, ocean salinity, and snow were considered as the model input to revise the seasonal prediction of the Climate Forecast System, version 2 (CFSv2). Results showed that on average U-Net reduced the root-mean-square error of the original CFSv2 prediction by 49.7% and 42.7% for the validation and testing set, respectively. The most improved areas were Northwest, Southwest, and Southeast China. The anomaly same sign percentages and temporal and spatial correlation coefficients did not present significant improvement but maintained the comparable performances of CFSv2. Sensitivity experiments showed that soil moisture is the most crucial factor in predicting summer rainfall in China, followed by geopotential height. Due to its advantages in handling small training dataset sizes, U-Net is a promising deep-learning method for seasonal rainfall prediction.
IG03-A008
Assessment of the Effectiveness of a Convolutional Autoencoder for Digital Image-based Automated Core Logging
Jaesung PARK+, Suwan SO, Jina JEONG#
Kyungpook National University, Korea, South
Widely applicable convolutional neural network (CNN)-based lithology classification models are limited to interpret soundness of a trained model and require high computational cost. This study proposes a convolutional autoencoder (CAE)-based classification model to improve the efficiency of rock-core-logging analysis based on digital rock-core images (CAE model I) and suggest a more understandable classification model by extracting the lithological feature information from the network structure of the model. Moreover, input digital-image data transformation using the Canny edge-detection algorithm was implemented (CAE model II). The applicability of the developed models is validated by comparing them with a CNN model and the model proposed by the previous study (RGBE model). While implementing the proposed model, digital images of 85-m-long cores were used, which were acquired from the Satyr 5 well in the Northern Carnarvon Basin, Western Australia. It was found that CAE models I and II showed classification accuracy comparable to the CNN model (CAE model I: 96.4%, CAE model II: 94.9%, CNN model: 97.5%, and RGBE model: 94.4%). The extracted features of the trained CAE models are effective in interpreting the trained network structure. In addition, in terms of computational efficiency and training time, the CAE-based models are significantly better than the CNN model (CAE model I: 7 min 21 s, CAE model II: 7 min 34 s, CNN model: 12 min 6 s, and RGBE model: 24 min 35 s). Overall, the results demonstrate the feasibility of the proposed CAE-based models for automated rock-core logging.
IG03-A016
Method of Assessing the Origin of South Korea Using Deep Learning-based Feature Extraction Technology
Subi LEE+, Jina JEONG#
Kyungpook National University, Korea, South
Isotope data of environmental samples, such as soil, groundwater, or rock, contain information about specific regional environmental characteristics, making it possible to guess the samples' origin. For this reason, isotopic data is widely applied to various research areas, including origin tracking, source tracing of environmental pollution or climate change research, etc. In particular, the ratio of 87Sr, which is naturally abundant in strontium isotope data, varies depending on the type of rocks and geological eras. Therefore, the geographical and geological origin can be inferred by comparing the strontium isotope ratio in the samples with baseline databases of strontium isotope ratios of each region. As a preliminary study to develop a model that can infer the origin of the environmental samples from the isotope data, this study quantitatively characterized geological properties of each geographical and geological origin, including information on rock type, tectonic provinces, major geochemical elements of rocks, and strontium isotopes. Autoencoder (AE), a deep learning technique, was applied to identify the complexity of the relationship between the origin and the various geological information. Before applying the AE, principal component analysis (PCA) was applied to discriminate the primary input data of the AE, influencing the characterization of the geochemical properties of origin. The actual database (soil samples) acquired from South Korea nationwide was applied to validate the proposed method in this study. Based on the low-dimensional features extracted from the AE, a total of eight origins were clustered, which was utilized to produce a map of the isotope content and estimate the origin of unknown environmental samples.
IG03-A017
Reconstruction of Electron Radiation Belts Using Machine Learning and Data Assimilation
Dmitri KONDRASHOV1#+, Alexander DROZDOV1, Yuri SHPRITS2
1University of California, Los Angeles, United States, 2GFZ German Research Centre for Geosciences, Germany
The radiation belts consist of electrons and protons trapped by the Earth’s magnetic and are a major source of damaging space weather effects on near-Earth spacecraft. The inner electron belt is located typically between 1.2 and 2.0 Earth radii, while the outer belt extends from about 3 to ∼8 Earth radii. Relativistic electron fluxes in the outer belt are highly variable; this variability is due to the competing effects of source and loss processes, both of which are forced by solar-wind-driven magnetospheric dynamics and by resonant interactions of plasma waves and particles. Understanding the mechanisms of build-up and decay of radiation belt electron fluxes is one of the fundamental problems of modern space physics. While significant progress has been achieved in understanding the electron radiation belt dynamics using physics-based models, it is still incomplete, due to the very limited number of satellites operating at different orbits in space and providing measurements of radiation belt electron fluxes. Presented approach for a global reconstruction of radiation belt electron fluxes represents the gray box combination (via data assimilation) of physics-based and machine learning (ML) models and considers errors (uncertainties) in both. First, low-Earth-orbiting (LEO) Polar Orbiting Environmental Satellites (POES) measurements are mapped by machine learning (ML) to medium-Earth-orbiting (MEO) Van Allen Probes dataset. The ML-based LEO-to-MEO mapping can be interpreted as creating high-quality Van Allen Probes-like (“virtual”) satellite measurements. To map POES measurements, two ML methods are considered: multivariate linear regression (MLR) and neural network (NN). The ML-mapped flux is then included by data assimilation with the Versatile Electron Radiation Belts (VERB) physics-based model and compared with Van Allen Probes observations as “ground truth”.
IG03-A019
Simple Physically-Based Emulator of the MATSIRO Land Surface Model
Roman OLSON#+, Kei YOSHIMURA, Tomoko NITTA
The University of Tokyo, Japan
Land surface and hydrological models are key tools to analyze and predict hydrological variables such as runoff. However, their major shortcoming is their relatively slow speed. This often precludes these models from being used for a host of tasks such as uncertainty quantification, sensitivity analysis, and so on. For these purposes, one requires a simple model approximating the original model’s behavior – a so-called “emulator”. Emulators of hydrologic models are a topic of active research. However, so far, to our best knowledge realistic global model emulators have only been constructed on a monthly scale, which considerably reduces their usefulness for many applications. Here we develop a simple and fast emulator of MATSIRO land surface model on a daily scale. The emulator takes as input five atmospheric variables (surface air temperature, precipitation, surface atmospheric pressure, snowfall, and surface specific humidity). The output of the emulator includes snow water equivalent, upper layer soil moisture, wetland water storage and runoff. Notably, in contrast to deep learning methods, emulator parameters and state are physically interpretable, which offers insights into soil moisture and runoff dynamics. We achieve improvements in speed via code written in modern Fortran with parallel programming using coarrays. The emulator operates at spatial scales ranging from a single grid point to regional to global. Emulator parameters are month and location-dependent. We optimize the parameters by minimizing simulation error at each grid point. We benchmark emulator performance and compare it with the original MATSIRO model, evaluate the emulator using a range of metrics, perform cross-validation, and discuss the emulator’s applicability under conditions of global climate change. We discuss data structures that help to speed up the emulator. Finally, we outline plans for coupling the emulator with other climate and social system component models (e.g., CaMa-Flood river hydrodynamics model), and enumerate future application areas.
IG03-A025
Quantitative Petrographical Criteria for the Exploration of Chromitites as Methanation Catalysts. A Data Analysis Example from Greek Peridotites
Haezan JANGARUN1, Elena IFANDI1#+, Stavros KALAITZIDIS2, Basilios TSIKOURAS1
1Universiti Brunei Darussalam, Brunei Darussalam, 2University of Patras, Greece
Carbon capture and catalytic conversion to methane have been proposed as a carbon-neutral energy production method. Recent studies show that platinum group minerals within chromitites catalyse Sabatier reactions and produce abiotic methane. Hence chromitites could be used as natural methanation catalysts for the production of syngas. In this respect, it is important to characterise the mineralogical aspects of rocks with different levels of methane to identify the optimum exploration targets for catalyst-bearing chromitites. Spinel is the host and/or the support of the natural catalyst(s) in chromitites. Statistical analyses of point counting data show that higher abundances of methane are found in chromitites with moderate (250-500 um) to large (500-1500 um) spinel crystal sizes whereas the methane-poor rocks include spinel with small crystal sizes (<250 um). Veining is important for the circulation of hydrothermal fluids. The rich-in-methane chromitites have the highest abundance of veins (approximately 10% higher than the rocks with moderate methane levels). In the rich-in- methane rocks, about 20% of the veins are classified as small (<100 um) and about 15% as moderate size (100-500 um). The methane-poor chromitites have limited veins (less than 10%). Overall, massive chromitites with adequate veining and moderate to large spinel size seem to host the highest abundance of methane. These petrographical characteristics probably enhance the effectiveness of the fluid-rock interaction in catalysis. Petrographical analyses are quick, low-cost and have low environmental impact for the characterisation of chromitites with catalytic potential for industrial scale.
IG03-A028
Spatiotemporal Dynamics and Forecasting of Ecological Security Pattern under the Consideration of Species Habitat: A Case Study of the Poyang Lake Ecoregion
Daohong GONG1#+, Min HUANG2, Hui LIN3, Changjiang XIAO4
1jiangxi normal university, China, 2Jiangxi Normal University, China, 3Jiangxi Normal University, China, China, 4Tongji University, China, China
With human activities' continuous expansion and development, many species' habitats face serious destruction and threats, and ecological security issues are becoming increasingly prominent. Therefore, constructing an ecological security pattern considering species' habitats is crucial for protecting biodiversity and maintaining ecological balance. As a paradise for wildlife, Poyang Lake is the habitat and breeding ground for many birds, fish, and other aquatic organisms. In this study, we selected the ecological circle around the Poyang Lake Ecoregion (PYLE) as an example. We produced Land Use and Land Cover (LULC) maps of the PYLE in 2000 and 2020 using the random forest classification method. Additionally, the Cellular Automata (CA)-Markov model was used to forecast the LULC in 2040. By combining morphological spatial pattern analysis (MSPA) analysis, landscape pattern index, landscape connectivity index, and Linkage Mapper with long-term LULC data, we constructed a long-term ecological security pattern in the PYLE. The dynamics of ecological security patterns over long-time series were compared and analyzed. Based on PYLE's predicted ecological security pattern in 2040, we propose an optimized ecological security pattern scheme of "one area, two zones, and multiple points". This study provides valuable insights for the sustainable development of the PYLE and the protection of species' habitats.
IG06-A001
Problems to Get Reliable Ionosphere Parameters Te and Ne with Small Satellite
Koichiro OYAMA1,2#+
1International Center for Space and Planetary Science, Japan, 2Asia Space Environment Research Consortium, Japan
Contamination of the electrode in Langmuir probe to measure electron temperature, Te and electron density, Ne, produces inaccurate data. This problem has not been paid attention to large satellite mission so far. At the stage when we are entering small/cube satellite mission, this problem is further worse, because the contamination of the satellite frame which act as the reference electrode also exists. We repeat here the serious problem of Langmuir probe measurement, in order to get reliable and accurate data. We need to make the maximum effort to save money, time and energy.
IG06-A009
Application Potentialities of Nanosatellite in Earthquake-prediction in Complex Solar Geomagnetic Environments by Adopting Ionospheric Equatorial Anomaly as the Precursive Feature
Minakshi DEVI#+
Gauhati University, India
Earthquakes are serious hazards in global scenarios, thus a need arises for a reliable prediction of such events, even though there are largescale efforts in this direction. The paper deals here with this aim by taking two basic issues (i) What are the Earthquakes (EQ) sources? and (ii) How effective is the role of Equatorial Ionospheric Anomaly (EIA) in identifying EQ precursors at wide and complex solar-geomagnetic ambiances? The data for the study consists of global EQ events with magnitude M>4.5 and TEC data from Global profiles covering high and low solar years of cycles 23/24 over the west Pacific and South Asia zones. An extensive analysis of the growth of the EQ and TEC with solar geomagnetic activity shows that EIA strength calculated from global TEC profiles reflects complex modulation before an impending EQ dictated by the solar geomagnetic environment., when its strength reaches a high, not at its maximum but 70 % to 60% below the RZ peak, and the same is true for geomagnetic status. Thus, intense solar background inhibits the growth of EIA, an important feature for EQ prediction and modeling. Further, the paper focuses on the adaptation of the growth of anomalous EIA at the night sector of the epicenter longitude as the precursors of an impending EQ by analyzing a few massive EQ events of M>7.0. Explanations for such growth of anomaly and its inhibition are provided through the EQ-induced E field and the Forbush effect. However, for reliable prediction and modeling, the simultaneous monitoring of magnitude. & direction of the E field, upper ionosphere density, and temperature at different heights under a qualified solar geomagnetic background are essential. Here nanosatellites with multisensor probes are the most effective solution, especially over the longitude zone covering the ring of fire location where our interest lies.
IG06-A012
Orbit Analysis of Very Low Earth Orbit (VLEO) Satellites
Sui CHEN1#+, Erick LANSARD2
1Politecnico di Milano, Italy, 2Nanyang Technological University, Singapore
The Very Low Earth Orbit (VLEO) (at altitudes below 450 km) offers an alternative solution to ease the congestion in LEO. Being closer to the Earth, satellites operating in VLEO also benefit from higher image resolution and lower communication link-budgets. However, they also experience a significantly larger atmospheric drag that will quickly lead to orbital decay, due to much denser atmosphere present in VLEO. Another challenge associated with operating in VLEO is the large modelling error of atmospheric density. This project focuses on predicting the orbit of a future VLEO satellite and subsequently proposing thrusting strategies for orbit maintenance. It is hoped that the results will provide insightful guidance for mission designers with an enhanced understanding of VLEO as an operational region for satellites. A 100kg satellite operating in VLEO with a dual-thruster electric propulsion system is considered. The impact of solar activity on atmospheric drag is investigated by modelling the F10.7 solar index based on observation data of the past 4 solar cycles. The upcoming solar activity cycle, depending on the sources, is expected to be similar or much stronger than the previous one, with a peak of 220 sfu occurring in December 2024. Using MATLAB, the satellite’s orbit subject to atmospheric drag is propagated. Without any orbit-raising manoeuvre, the satellite is predicted to re-enter the atmosphere after 1190 days. After predicting the satellite’s orbit under passive fall, a trade-off study is conducted to analyse different thrusting strategies by varying altitude, thrusting frequency, thrusting duration, delta-V and thrust magnitude. Finally, comparison between electric propulsion and the traditional chemical propulsion is drawn by computing their delta-V ratio. This project demonstrates the potential and feasibility of operating satellites in VLEO using electric propulsion. The results serve as a steppingstone towards enabling more VLEO satellite missions to be advanced in the future.
IG06-A013
Gemini Mission: An Education and Industry-academy Cooperation CubeSat Mission
Alfred CHEN#+, Jia-Ting LIN, Chia wen CHUANG
National Cheng Kung University, Taiwan
The Gemini mission led by the National Cheng Kung University was kicked off in 2022 to fabricate two 3U CubeSats for scientific experiments of GNSS receiver and UHV/VHF transponder, technology verification, and the proof of the space system engineering of a Taiwan space startup company. These two CubeSats are scheduled to place into a sun-synchronized orbit by an innovative hybrid rocket in 2024 Q2 or Q3. In this mission, two postdoctoral researchers, more than twenty undergraduate students, and an engineering team from the Taiwan space industry work together to build these CubeSats step by step. In addition to space system engineering, several Taiwan domestic industries also joined the development of the CubeSats and contributed their products for validation. This presentation introduces the development and strategy of this industry-academy cooperation mission, and its impact and outcome will also be discussed.
IG06-A018
Development of the Magnetometer EQM Model for the CAS-500
Seunguk LEE1#+, Kwangsun RYU2, Dooyoung CHOI1, Chang-Ho WOO2, Jinkyu KIM2, Wonho CHA2, Dongkook KIM2, Bon-ju KOO2, Seong-og PARK2, Cheongrim CHOI1, Dae-Young LEE1
1Chungbuk National University, Korea, South, 2Korea Advanced Institute of Science and Technology, Korea, South
The Ionospheric Anomaly Monitoring by Magnetometer And Plasma-probe (IAMMAP) is a space science payload package on the Compact Advanced Satellite 500-3 (CAS-500) planned for launch by the Korean Space Launch Vehicle (KSLV-III) in 2025. IAMMAP aims to understand the correlation between equatorial electro-jet (EEJ) and equatorial ionization anomaly (EIA), which plays a very important role in the plasma dynamics of the equatorial ionosphere. To measure the EIA, the instrument is equipped with a plasma probe, Impedance probe (IP) and Langmuir probe (LP), and to measure the magnetic field perturbation caused by the EEJ current, a fluxgate-type magnetometer, Adaptive In-phase MAGnetometer (AIMAG). The main feature of AIMAG is an in-phase circuit that keeps the phase of the output signal constant even when the temperature changes to solve the temperature dependence problem of fluxgate-type magnetometers. The EEJ is a variable flow of strong currents about 100 kilometers above the equator. Since the CAS-500 target orbit is a solar synchronous orbit of about 500 kilometers, the magnetic field perturbations generated at 100 kilometers above the Earth's surface are measured at 500 kilometers above the equator. The perturbed magnetic field of the measured EEJ is expected to be about tens of nT. AIMAG is operated with a sensitivity of several hundred pT to measure the EEJ. To exclude magnetic field contamination from the satellite, three AIMAGs will be installed on CAS-500: two on each end of the solar panels and one on the main body.
IG08-A001
The Approach of the Kinematics Modeling for Slip Surface Estimation, Characteristics, and Types of Landslide Using the Geodetic Method
Vera SADARVIANA#+, Hasanuddin Z. ABIDIN, Djoko SANTOSO, Joenil KAHAR
Bandung Institute of Technology, Indonesia
On the landslide anatomy, the slip surface separates the stable and unstable material on the slope. In the limit equilibrium method, the slip surface is used as a reference for calculating the safety factor. Landslide observation using GPS satellite technology is useful for monitoring the material slope displacement and eventually, disaster mitigation. This study's results are expected to contribute to the characteristics, types, and slip surface estimation in the Ciloto landslide zone using the kinematic model approach. Estimation of the slip surface is carried out in the first, dividing the slope into several parts based on the similarity of the horizontal displacement directions of the monitoring points. The similarity of the horizontal displacement directions indicates that the monitoring points are on the same slip surface. Second, the function of the maximum-minimum geodetic method for the velocity trend lines and polynomial approximation for the vertical profile. The intersection of the velocity trend lines shows the position of the slip surface when the material slides. The ideal planar slip surface is determined by infinite slope analysis and the circular slip surface is determined by circular arc analysis. The intersection of the two observed point velocity trend lines provides an estimate of the location of the slip surface. A geodetic approach can provide an estimate of the scarp's position as well. It was on a vertical profile to ensure conformity with the results of geological studies at the same study site. The Ciloto landslide zone has a very slow speed (5 x 10-5 - 5 x 10-7 mm/sec). The nature of horizontal displacement has a variety of directions. This characteristic indicates that the landslide zone has many slip planes. From this study. The landslide type is multiple compounds (rotational and translational) debris avalanches.
IG08-A002
Development and Testing of Small Array Corner Reflectors and Synthetic Aperture Radar for Slope Monitoring
Chih-Chung CHUNG#+, Chun-Cheng LIN
National Central University, Taiwan
This study aims to enhance the protection of lives and properties in hillside areas by proposing the implementation of a more advanced monitoring system using Synthetic Aperture Radar (SAR) and a small corner reflector (CR). The CR design is focused on being compact, lightweight, portable, and effortless to install, to provide more dependable SAR reflection points for landslide detection. Theoretically, altering the length of the sides of the CR can modify the maximum radar cross-section scattering (RCS) and reflection angle. To further simplify installation and reduce weight, a smaller and more manageable installation is proposed. Despite the smaller size of the reflector, the RCS may not be sufficient, hence the CR array setup is expected to enhance the reflection strength. The feasibility of this concept was verified through simulations using a multiphysics finite element modeling software and field testing with ground-based SAR, which showed that adding a small CR array increases the signal strength for a specific angle. Further field tests will be conducted to advance the practical implementation of this research.
IG08-A003
Landslide Mapping Using Google Earth Engine: A Case Study in Taiwan
Tee-Ann TEO#+, Tsung-Han WEN
National Yang Ming Chiao Tung University, Taiwan
Google Earth Engine (GEE) platform offers an easy-to-use interface for accessing open data, as well as the ability to develop custom applications using online cloud computing resources. Earth observation satellite images can be utilized for landslide mapping by comparing their spectral features between two different time periods. The stacking of multi-temporal satellite image creates a time-series satellite image which contain valuable information about the ground surface conditions. Due to the availability of time-series satellite images processing capabilities in GEE, this study aims to perform landslide mapping using deep learning techniques and time-series satellite images from GEE. In this study, we employ a Long Short-Term Memory (LSTM) neural network to classify regions as either landslide or non-landslide, using 30m time-series Landsat-8 images. The focus of this landslide detection is on regions, rather than individual pixels. A multiscale image segmentation approach is applied to identify regions with similar spectral characteristics. Each region is then analyzed for its time-series spectral information, which is used for landslide detection. The LSTM model is trained by manually digitized landslide labels and segmented regions. The accuracy of the model is evaluated by precision and recall, using an individual check area. The training area is located in the mountainous central region of Taiwan and covers an area of 2600km2. The individual check area is located in the southern part of Taiwan and approximately 1800km2. The time-series image was created using Landsat-8 images from the years 2015 to 2018. The proposed LSTM model uses time-series spectral information to identify landslide regions. The preliminary experimental results show that, the precision and recall for landslide areas were 51% and 72%, respectively. In conclusion, GEE provides a convenient platform for constructing time-series satellite images, and the proposed landslide detection achieved a 70% accuracy using 30m satellite images.
IG08-A010
In Situ Monitoring and Analysis of Slope Stability in the Baoshan Village of Kaohsiung
Huai-Houh HSU#+, Yen-Chi HUANG, Chen-Hsun HSIEH
National Kaohsiung University of Science and Technology, Taiwan
Baoshan village is located in Taoyuan District, Kaohsiung City. The geology here is mainly the Lushan formation, composed of weathering and broken slate. According to the geological survey data, it has been observed that there are many disaster potentials in this area. This paper analyzes the possibility of sliding here using in situ surveys and monitoring. In terms of field investigation, it was observed that there were noticeable cracks in many structures and retaining walls in Baoshan Elementary School. In the Baoshan village, multiple floor bulges, broken walls, and floors were found. According to the in situ survey results, this study set up three inclinometer casings with depths of 22m, 40m, and 50m, respectively, and seven tiltmeters at this campus. The monitoring frequency is about once a month, and the monitoring data, groundwater table, and rainfall are collected and analyzed. The long-term monitoring was carried out from 2018 to 2022, and it was observed that the slope mainly slowly moved toward the northwest direction. The relative movement of layers deformed the inclinometer casing on the north side of the campus. This displacement was observed at a depth of 46m below the ground surface. While Comparing the data of rainfall and groundwater table, it is speculated that the typhoon brought concentrated heavy rainfall to cause the groundwater table to rise and trigger the slope of a slide.
IG08-A011
Deriving Rainfall-landslide Thresholds for Tectonically and Geomorphologically Heterogeneous Regions: The Philippine Example
Beth Zaida UGAT#+, Decibel FAUSTINO-ESLAVA, Jefferson RAPISURA, Bianca Maria Laureanna PEDREZUELA, Maria Regina REGALADO, Gabriel Angelo MAMARIL, Jenielyn PADRONES, Rosemarie Laila AREGLADO, Loucel CUI, Juan Miguel GUOTANA, Cristino Jr. TIBURAN, Jayson ARIZAPA
University of the Philippines Los Baños, Philippines
Landslide disasters in the Philippines are often caused by the geographical location of the country exposing the land to extreme weather events frequently damaging properties and causing losses of lives. In an area vulnerable to such, intensive research and study that requires extensive data are beneficial. The national government has identified the need to mitigate landslide disasters through initiatives such as Project LIGTAS or “Landslide Investigations on Geohazards for Timely Advisories in the Philippines”. Project LIGTAS focuses on the generation of a non-structural preventive approach to mitigate landslides using rainfall-landslide thresholds. Furthermore, landslide events and rainfall data mining and population are being done by Project LIGTAS. This study aims to present the generated thresholds for the provinces of Benguet and those in the Southern Tagalog region. This paper discusses the encountered challenges in data acquisition and the solutions employed by the team. Lastly, potentials to operationalize a localized landslide early warning system within the study areas are also presented. Various methods and platforms were utilized for data acquisition such as from partner national government agencies. With the current data, huge differences have been derived for different geological areas. Approximately 27 mm of rainfall already triggers slope failures in the CALABARZON region, while selected areas in the Bicol region trigger landslides at around 90 mm of rainfall. Lower thresholds were generated for the Benguet province where slope failures start at lows of 12mm of rainfall. Continuous data collection and correlation can further improve threshold values and be used in the formulation of localized early warning systems protocol for the study areas. The results of this work are used in the landslide warning system posted on the LIGTAS website (www.ligtas.uplb.edu.ph). Additionally, the simplicity of the method provides a higher chance of adaptation by other regions in the country.
IG08-A012
Rainfall-Pore Pressure Response of a Dip Slope: Insights from a Tank Model Based on 3-D Geological Model
Alvian R. YANUARDIAN#+, Jia-Jyun DONG
National Central University, Taiwan
For any engineering project, a 3-D geological model is crucial for estimating geological conditions, especially those related to the hydrogeological condition of a dip slope. This study proposes the tank model as a fast way to know the abnormal pore pressure changes caused by rainfall and geological conditions. In order to identify the orientation and distribution of the lithology in the research area, we used the average of 3 types of orientations; 1) a planar-like feature on the east slope of the research area, 2) the orientation of key-bed from 3 boreholes that show distinct sedimentary structure called wavy laminations, 3) orientation of shale layers from 2 boreholes and an outcrop. Afterward, 14 boreholes were adjusted based on the average bedding plane orientation in order to identify the rock units and boundaries. Subsequently, applying linear regression to construct a 3-D geological model and also clarifying it using a cross-section. The result shows that the 3 types of orientation show similarities in orientation indicating the lithologies are spatially distributed well in the research area. We also defined 6 rock units and colluvium-infilling material, with 6 boundaries. On the other hand, calibrating the tank model's parameters based on a hydraulic test is used to get the best fit simulated groundwater level’s result. Therefore, re-calibrating is proposed to make sure the tank model’s parameters based on the hydraulic test fit well for the rainfall cases. The slow responses of pore pressure induced by rainfall which is represented by the good fitness of the tank model’s simulation, indicate that geological conditions, including joint sets, are responsible for it. Moreover, the parameters of the tank model’s simulation can be used to predict future pore pressure responses induced by rainfall which can trigger landslides.
IG09-A002
Cascading Impacts of Tsunamis and Coastal Vulnerability in the Indian Ocean
Anawat SUPPASRI1#+, Ryuto MIZUSHIMA1, Constance Ting CHUA1, Elisa LAHCENE1, Miwako KITAMURA1, Pescaroli GIANLUCA2, David ALEXANDER2, Fumihiko IMAMURA1
1Tohoku University, Japan, 2University College London, United Kingdom
The 2004 Indian Ocean tsunami left its fingerprints on coastal communities across the Indian Ocean basin, demonstrating the far-reaching potential of a single tsunami event. A tsunami does not only impact the population but can also have cascading impacts on the critical infrastructure which the population depends upon. For instance, tsunami damage to port facilities as well as power generation plants does not only affect the local population, but it can also impact on regional and global supply chain. The objective of this study is to provide a preliminary vulnerability assessment of coastal communities against tsunami hazards and their cascading impacts in the Indian Ocean. Vulnerability of coastal communities will be considered from the perspectives of population size, age and gender. For this purpose, we collect some data that can be used to identify tsunami vulnerability such as high-resolution world population data (including age, gender and migration status) and locations of ports and power generation plants. Though tsunami hazard assessments have been performed at macro scales for the region, there has been limited focus on tsunami hazards under the influence of a changing climate. Therefore, we also consider the effects of rising sea levels in the event of tsunamis.
IG09-A006
Extreme Nearshore Surface Currents in Singapore
Jun Yu PUAH1#+, David LALLEMANT1, Ivan HAIGH2, Dongju PENG1, Kyle MORGAN1, Adam SWITZER1
1Nanyang Technological University, Singapore, 2University of Southampton, United Kingdom
Despite the importance of extreme currents in key applications such as ship navigation, sediment transport and coral growth, research remains scarce due to the lack of long-term observational records. In this study, we model the profile of extreme shallow-water currents off Pulau Hantu and Kusu Island, both located along the Singapore Strait, and investigate their potential drivers. We decomposed about 12 months of observed currents into their tidal and residual components by applying harmonic analysis. The tail distribution of the residual component was estimated using extreme value analysis by fitting a non-homogeneous Poisson process to the data, accounting for temporal and directional dependences. Random simulations of tidal currents were then combined with residual currents via the Joint Probability Method to generate new observed current realizations. Finally, we extracted wind speeds from ERA5 Reanalysis to investigate how well monsoonal winds correlate with residual currents across monsoon periods. Tidal variance ranges from 29-69% across all sites, which is lower than expected given the dominance of tidal currents in the Singapore Strait. Extreme currents orient primarily along the coastline contours. Mean speed in Pulau Hantu is greater than Kusu Island and may be attributed to the hydrodynamic pressure gradient set up by the monsoons. Lastly, the stronger correlation observed in some sites during the inter-monsoon periods suggests that localized wind systems such as the Sumatra squalls are critical in driving extreme currents. The variability of the study results highlights the challenges in modelling currents in the Singapore Strait given its complex bathymetry, equatorial weather patterns and complex tidal regime. Future work could include the integration of shipborne Automated Information Systems to derive extreme surface currents in Singapore and the Sunda Shelf region.
IG09-A009
A Stochastic Model of Potential Tsunami Impacts Originating from the Southern Part of the Manila Trench
Elaine Hz TAN1#+, Linlin LI2, Qiang QIU3, Constance Ting CHUA4, Masashi WATANABE1, Adam SWITZER1
1Nanyang Technological University, Singapore, 2Sun Yat-sen University, China, 3Chinese Academy of Sciences, China, 4Tohoku University, Japan
Tsunami can impact both near and far field locations, as illustrated by the 2004 Indian Ocean, 2018 Palu and the 2011 Tohoku-Oki events. In Southeast Asia, the tsunami hazard is often tied to the subduction zone systems in Indonesia. The Manila Trench in the South China Sea is also likely able to generate damaging tsunamis however available studies have predominantly concentrated on the northern sectors of the fault and examined the potential tsunami impact on Luzon, Philippines, Vietnam, Hong Kong, Macau and China. Little is known about the tsunami risk posed by the southern segments of the fault. Our study seeks to fill this gap by conducting tsunami hazard assessment for this region. We model heterogeneous slip distributions from the southern segment of Manila Trench (13-16°N) for earthquake events, with magnitudes ranging from Mw 7.4 to 8.4, and their wave propagations. Using the obtained peak nearshore tsunami amplitude, we developed hazard curves for fifty-two (52) study sites. The study sites were selected based on population density and economic importance. Our preliminary analysis indicates that areas in close proximity like the Philippines are at most at risk with localised tsunami heights of up to 5.4m followed by areas in southern Vietnam where localise tsunami height can be up to 4.3m. In contrast, Singapore, Malaysia, Indonesia, Thailand and Cambodia are likely to be less affected and modelled tsunami heights do not exceed 1 m. As our preliminary study does not consider wave run-up or tsunami currents, this hazard is likely to be an underestimate at this current point.
IG09-A011
Numerical Simulation of Storm Wave Propagation Over Structural Complexity of Coral Reefs at Komaka Island, Japan
Masashi WATANABE1#+, Hironobu KAN2, Ken TOGUCHI3, Yosuke NAKASHIMA4, Volker ROEBER5, Taro ARIKAWA6
1Nanyang Technological University, Singapore, 2Kyushu University, Japan, 3University of the Ryukyus, Japan, 4Ariake College, Japan, 5University of Pau and Pays de l'Adour , France, 6Chuo University, Japan
Propagation of storm waves across coral reef is affected by geomorphology over reef slope. Complex structures of several meters over reef slopes, such as spur and groove formations, are also believed to affect current or wave propagation. A spur is topography whose elevation is partially high over the reef slope to the reef edge and a groove is a depression between the spurs. In particular, the direction and energy of wave are controlled by the structural complexity. However, measurements of water depth data in shallow water regions, such as reef slopes over coral reefs, have recently become possible using multibeam echosounders installed in small vessels. Therefore, to date, measured water depth data, including several-meter-sized complex structures, have not been used for numerical simulations. The objective of our research is to investigate the effect of several-meter-sized complex structures on coastal wave run-up and propagation based on numerical simulation using real topographic data. To reveal the role of the structural complexity of coral reefs, we conducted numerical simulation of storm wave at coral reefs of Komaka Island. We first conducted a multibeam survey to reveal the topography of the reef on Komaka Island. The high-resolution bathymetry of 1 m grid size was observed by multibeam echo sounding (MBES) survey was used for the simulation. We then conducted a three-dimensional simulation using the measured topography with a supercomputer, and this simulation results can explain observed significant wave height during strong waves from typhoons at Komaka Island. After that, we conducted two-dimensional simulation of storm waves and estimated wave friction factor which can explain simulation result of the three-dimensional simulation. After the setting of wave friction factor, we investigated effect of the structural complexity against storm wave propagation from our simulation results.
IG09-A015
The Development of Deep Learning-based Tsunami Forecasting for Early Warning System in Java Island, Indonesia
Muhammad Rizki PURNAMA#+, Anawat SUPPASRI, Kwanchai PAKOKSUNG, Fumihiko IMAMURA
Tohoku University, Japan
Past events of the catastrophic tsunami in Indonesia, such as Flores tsunami 1992, Banyuwangi tsunami 1994, The Great Indian Ocean tsunami 2004, Pangandaran tsunami 2006, Palu tsunami 2018, and Krakatau tsunami 2018, have caused significant damage and losses in the coastal area. Most of the events are triggered by a submarine earthquake. One of which is from the Java subduction zone. Three major earthquakes with tsunamis have been caused by deformation along this subduction zone. Thus, this zone covers most of the populated as well as notable area span from Java to Nusa Tenggara, such as Pelabuhan Ratu, Pangandaran, Yogyakarta, Bali Island, Mandalika, and Nusa Tenggara. Therefore, Indonesia needs a decent Tsunami Early Warning System. There are only six existing cable-based tsunameters (CBT), which use bottom pressure gauges to inspect tsunami wave propagation in Indonesia's deep-sea area to issue an early warning. In this paper, we assessed the optimal deployment of tsunami buoys along The Southern part of Java Island to Nusa Tenggara and make an optimization scheme using a Deep Learning-based model. First, we create a set of synthetic tsunami scenarios using a stochastic-slip earthquake model with Mw 8.0-9.2 for the Java Megathrust fault to generate multiple tsunami-earthquake scenarios. Next, we apply the empirical orthogonal functions (EOF) based on the tsunami scenarios to determine the initial location for the deployment of each tsunameter. Finally, we apply an optimization scheme to forecast maximum tsunami height and arrival time in the coastal area using Convolutional Neural Network (CNN). Tsunami wave height at each initialized tsunameters are defined as an input in our model. Then, we do the sensitivity analysis to find the optimal placement by reducing the number of the tsunameters while evaluating its MSE. Thus, this scheme will lead to the improvement of the tsunami early warning system in Indonesia.
IG09-A021
Engineering Properties Measurement from Free-fall Penetrometer in Sandy Soils: A Preliminary Study in Theoretical Approach
Chun-Hung LIN#+, Wei-Jong TIEN, Po-Yin LIN
National Sun Yat-sen University, Taiwan
Free-fall penetrometer is an efficient tool to investigate the offshore shallow sub-seabed, especially in the transition zone and shallow water. It can provide the engineering properties of the sub-seabed. However, currently, most of the applications are based on empirical formulas. The aim of the study is to establish a theoretical-based algorithm to measure the engineering properties of the free-fall penetrometer. A 1-D theoretical-based algorithm for homogeneous and isotropic soils was established to study the behavior of change of velocity of free-fall penetrometer after penetrating into sandy sub-seabed. A linear inversion skill was applied to invert the engineering properties of the sandy soils. The results show that the algorithm can better describe the penetrating behavior with reasonable engineering properties. A further experimental study should be conducted to verify the measured engineering properties.
IG10-A001
Technique Development for Intersection Between Fracture System and Objects by Means of Hybrid Domain Model
Chuen-Fa NI1, Yun-Chen YU2,1, I-Hsien LEE1#+
1National Central University, Taiwan, 2Atomic Energy Council, Taiwan
Detecting precise start location of containment is crucial for numerical modeling of groundwater flow and transport, especially for some of the containments are stored inside the containers. Due to the low water-conducted feature of rock matrix, the fractured rocks are one of the potential host rocks for containment disposal. However, the fracture system of fractured rocks plays an important role on groundwater flow and transport, and the hydraulic characteristic of rock matrix is critical as well. In this study, we present a hybrid domain (HD) model, which can consider fracture system and rock matrix simultaneously, to simulate groundwater flow and transport in fractured rock. A series of objects are also embedded in a complex conceptual fractured rock for developing the technique of intersection between fracture system and objects. The interactions between fracture system and objects is detected, and the additional nodes are generated on the intersections for the following flow and transport purpose. The system of equation for flow field of the complex conceptual fractured domain is solved by means of the mesh generation algorithm, which employs two-dimensional (2D) triangle for fracture system and surfaces of objects and three-dimensional (3D) tetrahedron for rock matrix and interior of objects. Results show that the detection technique is successfully developed, so does the mesh generation algorithm for the complex conceptual fractured domain. Results also show the detail flow field and the accurate flow velocity on the intersection between fracture system and objects are simulated. These results are critical information for containment transport modeling in the fractured rocks.
IG11-A001
A Data Management Plan Starting with Climate Change Data Services
Tzu-Ming LIU#, Shih-Yao LIN+, You-Syuan CHEN, Yung-Ming CHEN
National Science and Technology Center for Disaster Reduction, Taiwan
Taiwan Climate Change Projection Information and Adaptation Knowledge Platform (TCCIP), with the support of the National Council of Science and Technology, has been providing climate change-related scientific data, information, knowledge and tools that Taiwan needs to promote climate change research and adaptation programs since 2012. In order to ensure the data quality of climate change big data and expand the scientific application services of research data, we have tried to draw up the TCCIP Data Management Plan (DMP) with reference to international experience and with the FAIR principle as the vision since 2019. The original intention of DMP is to effectively plan and implement data management, which includes the life cycle of data, from "planning", "production", "checking", "storage", to "publishing", respectively. Behind the climate change data services provided by TCCIP, the DMP is the core of climate change integration services, which includes external data service policies and internal data management regulations. This study will use the experience of TCCIP to illustrate the content of the DMP behind the climate change integration service platform, how to implement it into external data services, and provide reference for climate services.
IG11-A002
Open Data Produced by “Minna De Honkoku”
Yasuyuki KANO1#+, Yuta HASHIMOTO2
1The University of Tokyo, Japan, 2National Museum of Japanese History, Japan
“Minna de Honkoku” (https://honkoku.org/) is crowdsourced and online collaborative project to transcribe historical materials written in old Japanese. "Minna de Honkoku" was launched as an online citizen science project to transcribe earthquake-related historical materials from Earthquake Research Institute Library, the University of Tokyo. On July 2019, the system of Minna de Honkoku was upgraded to support IIIF, International Image Interoperability Framework. Broader range of manuscripts on digital archives adopting IIIF can be registered for transcription. The subjects of the project was extended to cover wide variety of historical materials as well as earthquake-related materials. AI-assisted transcription was also implemented. More than 3,500 documents are registered on the system. Total number of characters transcribed is about 28 million. The transcribed text data is shared using Creative Commons licenses (CC BY-SA). The data is used for, for example, editing bibliographic information at libraries, museums and so on. The text is also used for publishing e-books that translates classical literature. An experiment of OCR text conversion of digitized materials of the National Diet Library, Japan (NDL) Lab utilized the transcribed text of Minna de Honkoku. The OCR Training dataset is also published by NDL Lab.
IG11-A003
NASA’s Science Discovery Engine: Enabling Interdisciplinary Open Science
Kaylin BUGBEE1#+, Ashish ACHARYA 2, Emily FOSHEE2, Kumar RAMASUBRAMANIAN2, Carson DAVIS2, Xiang LI2, Rahul RAMACHANDRAN1, Shawn FOLEY3
1NASA Marshall Space Flight Center, United States, 2University of Alabama in Huntsville, United States, 3All Points, United States
NASA is committed to fostering an inclusive open science community, defining open science as collaborative, technology-enabled sharing of data, information, and knowledge to accelerate scientific research and understanding. NASA champions the Open-Source Science Initiative (OSSI) to support this. OSSI's cyberinfrastructure includes the Science Discovery Engine (SDE), which enables the discovery of data, software, and documentation across NASA’s five science disciplines. The SDE increases potential data reuse and fosters interdisciplinary science by making data and information more discoverable to a larger audience. The beta SDE version was released in December 2022 and includes over 84,000 datasets, 700,000 documents, and 9,000 science terms. The SDE development was collaborative and guided by subject matter experts. In this presentation, NASA shares lessons learned while developing the SDE and seeks community feedback on the SDE's information and features.
IG12-A002
Attempt to Estimate Long-term Vertical Land Surface Movement Using Archaeological Information in Actively Subsiding Sedimentary Basin, Niigata, Japan
Yuka ITO1#+, Seiichi SHIMADA2, Tomochika TOKUNAGA1
1The University of Tokyo, Japan, 2Nippo Co., Ltd., Japan
The Niigata Plain, central Japan, is an actively subsiding sedimentary basin with its tectonic subsidence rate to be ca. 3-4mm/yr at its coastal area. In addition, anthropogenic activities such as groundwater abstraction may accelerate compaction, which results in the formation of accommodation space for sedimentation.
Archaeological surveys have been investigated in this plain, and the elevation of paleo-ground surfaces have been determined from buried sediments and in the paleo lake bottom sediments. Depths of archaeological sites excavated in the Niigata Plain are much deeper than those in other plains in Japan. Therefore, previous studies have indicated the possibility that local ground deformation (e.g., earthquakes) may have caused the burial of archaeological sites or the expansion of lagoons.
In this study, we attempt to understand the long-term land surface movement of this plain by extracting buried heights from many archaeological survey reports and by mapping the extracted data spatially. Paleo-surface during ca. 1000 years ago to the present tends to be deeper towards the western side of the plain while shallower towards the eastern side. This characteristic spatial pattern indicates that the western part of the plain may have subsided faster relative to the eastern part. Because the stratigraphic analysis suggested that the sites were not affected by flood events that dramatically buried the remains nor by sea-level changes of recent 1000 years period, the spatial pattern of land surface movement extracted from the archeological reports is likely reflecting the long-term subsidence of the plain.
IG12-A003
On the Observation of Signal Behavior from Magnetotelluric Survey in the Urban Area of Taiwan
Haiyina Hasbia AMANIA1+, Ping-Yu CHANG1#, Ding-Jiun LIN1, Jordi Mahardika PUNTU1, Yin-Long CHEN1, Lingerew Nebere KASSIE1, Jun-Ru ZENG1, Yonatan Garkebo DOYORO2,1
1National Central University, Taiwan, 2Academia Sinica, Taiwan
Geophysical survey has made understanding of the Earth’s subsurface possible and thus aids the planning and the execution of natural hazard mitigation as well as energy resource exploration. Many geophysical methods are developed to suit various exploration targets. Magnetotelluric (MT) is one of the common methods that can be used to retrieve subsurface information both from shallow and deep target. It is a passive geophysical method that measure the naturally occurring electromagnetic (EM) field at the earth surface. The MT survey can record EM waves in the frequency range between 10-4-104 Hz. Such a wide band frequency makes it possible for MT to yield tens to a few hundreds of kilometers subsurface information. Yet, it is due to this reason that the MT method suffers from electromagnetic noise contamination that lies between its broadband frequency range. While the noise source can come from natural phenomenon such as a complex geological condition, artificial sources are also significantly affecting the recorded signal. A few examples are power transmission lines, urban constructions, communication devices and electric railway. The contamination often results in distorted MT data and the decrease in reliability of the subsurface information. Thus, obtaining a good quality MT data has been a challenge for many years. In this study, we begin by observing the MT timeseries recorded in urban area where noise source is abundant. We analyze the timeseries and attempts to work out how signal from difference sources are affecting the data and what are their approximate frequency range. This can be helpful to identify the character of each signal and better help preserve the target signal to avoid underestimation or overestimation. This work serves as a groundwork for our future studies in attempt to obtain an improved result from MT survey, especially in the urban area of Taiwan.
IG12-A008
Changing Patterns and Determinants of Green Buildings in Guangzhou, China
Lijie LIN#+
Guangdong University of Technology, China
With the development of the economy and society, energy crises and environmental problems have been a worldwide concerned issue. Considering that energy consumption in construction and related sectors is much higher than that in others, the concept of green building is accordingly processed. In accordance with China’s carbon goals of energy saving and emission reduction, it is necessary to study the spatiotemporal patterns of green buildings in China and to reveal the driving forces of such patterns. The previous study of spatial and temporal variations of green buildings in China mainly focused on a national or regional scale, while the disparity of green buildings within a particular city has not received much scholarly attention. Based on the data of green buildings label projects from 2008 to 2021, by taking Guangzhou as a study case, this study aims to explore the spatiotemporal patterns and the major driving forces of uneven green buildings development in Guangzhou. It is found that: (1) Green buildings developed a lot in Guangzhou from 2008 to 2021. The growth rate of the number of projects and construction areas reached a peak in 2013 and then moderated to a stable lower trend. (2) Most of the green building projects gathered in the central west and south of the city, while small parts of them gathered in the northeast. Additionally, there is a significant disparity in ratings of green buildings in the spatial dimension. (3) Economic factors and resource factors are the main factors affecting the development of green buildings.
IG12-A010
Changes in Productivity and Deep Water Oxygenation at Central South Pacific Across the Mid-Pleistocene Transition - A Benthic Foraminiferal Proxy
Nirakara MAHANTA#+, Raj Kumar SINGH, Sunil Kumar DAS
Indian Institute of Technology Bhubaneswar, India
The emergence of 100 kyr glacial cycles after the mid-Pleistocene transition (MPT) has always been linked with a long-term decrease in atmospheric pCO2 levels. The Southern Ocean plays a major role in decreasing glacial pCO2 through enhanced productivity and stratification of the water masses. To assess these variabilities, we analysed the benthic foraminifera of the sediment cores recovered from IODP Site U1540 (55o08.5’S, 114o50.5’W, 3580 m depth) for the period up to 1.5 Ma. The distribution pattern of benthic foraminifera are ideal proxy to assess the variations in productivity, organic carbon flux, and changes in the dissolved oxygen contents of the bottom water. The site is located in the Central South Pacific (CSP) and responds to global atmospheric fluctuation. The high productivity group, which includes Melonis pompilliodes, Melonis barleeanum and Uvigerina peregrina showed an increasing trend from pre-MPT to post-MPT period, but the amplitude of fluctuations increased during the post-MPT. This suggests a switch to 100 kyr, high amplitude change in productivity at CSP during various glacial-interglacial period. This is also evident from the increase in infaunal vs epifaunal ratio and increase in benthic foraminiferal species diversity. The bottom water corrosiveness was nearly absent during the pre-MPT and early transition period, which increased towards last phase of MPT marked by the abundance of Nuttallides umbonifera. This study observed high-amplitude fluctuation in all the proxies after the MPT in response to long-term glacial-interglacial changes at CSP.
IG12-A011
Participatory Resource and Landscape Services Mapping of an Upland Mining Community: Case Study of Ampucao Village in Itogon, Benguet, Philippines
Rico Neil QUIERREZ1,2#+, Ma. Catriona DEVANADERA3, Edgar Jr REYES3, Casper Boongaling AGATON3, Leonida BUGAYONG2, Jessie SAMANIEGO4, Cris Reven GIBAGA4, Alexandria TANCIONGCO5,6, Carlo ARCILLA5
1University of the Philippines, Philippines, 2University of the Philippines Open University, Philippines, 3University of the Philippines Los Baños, Philippines, 4Philippine Nuclear Research Institute, Philippines, 5University of the Philippines Diliman, Philippines, 6University of the Philippines Diliman, Philippines
Long-term sustainable management of mining areas entails better understanding of human-environment interaction including environmental impacts, land use and landscape services among local communities. The study area, Ampucao Village in Itogon, Benguet, has long been a mining community hosting a sixty-year-old large-scale mining company and numerous artisanal small scale gold mining. In this research, participatory mapping and focus group discussion were conducted to characterize the human-environment interactions of an upland mining community in Philippine context through a community drawn resource map outlining their natural, economic and social resources. Sketch maps were then digitized using QGIS 3.22.8 for spatial occurrences and analyses. Results show that landscape services enjoyed by Ampucao community from their environment mainly include food, geological resources, ornamental resources, fuel, raw materials, spiritual values, aesthetics and social relations. Generated maps show geographic patterns of each landscape service. Identification and mapping of community’s local spatial knowledge are critical inputs to sustainable management of mineral rich areas and could serve as essential guide for policy makers regarding mixed-used natural resources management.
IG12-A012
Urban Change Detection in Metro Manila, Philippines Using Sentinel-1 SAR Coherence
Ma. Criselda BALDAGO#+, James Cesar REFRAN, Paul Daniel ANG, Gay Jane PEREZ
Philippine Space Agency, Philippines
Monitoring urban change is of significance to policy makers, city planners, and social and environmental scientists in addressing problems that may arise from the growth or decline of an urban settlement. Metro Manila, Philippines is one of the most rapidly growing urban regions in East Asia and the Pacific with a current population of 18,649,422 increasing at a rate of 2.05 percent annually. Among the challenges in studying the urbanization of Metro Manila, is identifying centers of rapid population increase. This rapid and dispersed growth in urban areas is difficult to monitor on the ground. Consequently, problems such as pollution, transportation, lack of resources and inequality would result from failure to monitor these growth centers. Satellite remote sensing is an advantageous tool for urban change detection, having global coverage and consistent revisits of the same area which is ideal for monitoring. Particularly, the Synthetic Aperture Radar (SAR) instrument offers reliable, wide-scale data regardless of the time of day and weather condition. Buildings and other man-made structures have a high radar reflectance when observed in multi-temporal SAR images. Coherence is the similarity of radar reflectance between two SAR images of the same area taken at different times. In this study, Sentinel-1 SAR images of Metro Manila, Philippines were processed to obtain the difference in coherence between consecutive monthly images dated 2018 to 2022. Geospatial Information System (GIS) operations were performed to determine how urban areas evolved in the last four years. Validation of generated coherence maps through optical imagery confirmed detectable changes in industrial and commercial districts as well as large residential areas in Metro Manila. Effectively monitoring the centers of population growth in urban areas would aid in building more sustainable and livable cities.
IG12-A015
Integrated Geophysical Studies to Decipher Subsurface Configuration and Evolution of a Non-volcanic Geothermal System Along Mahanadi Rift Basin, India
Aurobindo Kumar BASANTARAY1+, Animesh MANDAL2#
1Earth Sciences, Indian Institute of Technology Kanpur, India, 2Indian Institute of Technology Kanpur, India
Non-volcanic hot springs within intracontinental rifted but relatively stable continental part are often less studied owing to its inherent low-enthalpy nature and sedimentary provenance. Present integrated geophysical study using gravity and magnetic methods, combined with the results of previous near-surface investigations, aims to map sub-surface structure, and to understand the evolution of hot springs in the Atri and Tarabalo region of the Mahanadi rift basin, Odisha, India. Gravity-magnetic study reveals deeper structure and its effect on geothermal activity. The 3D gravity model deciphers the presence of high density (>2750 kg/m3) igneous formations beneath the metamorphic and sediment formations as well as the depth extent of Mahanadi fault. Deeper Moho (depth ~34 km) than the estimated average curie depth (as 29 km) for the area supports the presence of felsic intrusion as observed in 3D model. Based on geophysical inferences and previous geological findings the study hypothesises that Mahanadi rift basin may have originated from a pull-apart basin formation during the Permian period, leading to multiphase tectonic and sedimentation processes until the separation of Australia, Antarctica, and India during early Cretaceous. The Mahanadi graben has undergone transformation due to breakup after ignition of plume activity, resulting in the Khondalite group of rocks and igneous rock formations around the edges of the graben. Both rock formations act as heat sources in the hot spring region. Faulted metamorphosed formation overlain by sedimentary formations is identified as the strata for heat transfer to meteoric water via convection processes, and the strata may be considered as the hot water reservoir. Smaller faults and fissures that link Mahanadi fault act as conduits for hot fluid outside of the geothermal system's heat source and reservoir, and may have evolved during the basin's rifting phase.
IG12-A016
The Origin of Pyrite in the Soils of Brunei Darussalam
Pavlos TSIKOURAS1, Stavros KALAITZIDIS1, Elena IFANDI2, Azrina BOEY2, Basilios TSIKOURAS2#+
1University of Patras, Greece, 2Universiti Brunei Darussalam, Brunei Darussalam
Pyrite deposition in sedimentary basins is an intriguing topic due to the great variety of the forming processes, often overlapping. Additionally, its formation plays an important role in the global Fe and S cycles, largely affecting the redox chemistry of the atmosphere. Pyrite is abundant in all the detrital Miocene sedimentary formations of Brunei Darussalam. X-ray diffraction data and microscopic studies show the abundance of octahedral and/or cubic pyrite, frequently associated with clay and/or coal layers, suggesting an authigenic, rather than detrital, origin and slow rates of crystallisation. Infrequently pyrite is associated with gypsum and native sulphur. It is likely that the pyrite formation in Brunei is triggered by sulphate-reducing bacteria (SRB), which mediate in the formation of pyrite from the transformation of mackinawite and/or greigite, formed in euxinic environments. Microbial H2S is capable to convert FeS to FeS2 (pyrite). The occurrence of sulphur S0 promotes the conversion of mackinawite into pyrite and may derive either from the oxidation of bisulphide (HS-), a common metabolic product of SRB, or from the organic matter in the sediments, which consumes oxygen and releases sulphur. It has been suggested that pyrite-forming reactions are coupled with methane formation with the synergistic aid of methanogen microorganisms. In outcropping formations and/or nearby surfaces of recent sediments, the pyrite is extensively oxidized to Fe-oxides forming red ferricrust. The occurrence of gypsum may be explained by the oxidation of pyrite and the production of H2SO4, which reacts with Ca2+ of the abundant micro- and nannofossils hosted in the Miocene formations. This natural acid drainage process is thought to be responsible for the highly acidic soils in Brunei Darussalam and requires close monitoring for potential adverse effects on agricultural activities and groundwater contamination.
IG12-A018
Assessment of the Geochemical Contamination Levels in the Agricultural Soils of Brunei - Muara District, Brunei Darussalam
Khairunnisa Nazirah KARIM, Elena IFANDI#+, Azrina BOEY, Adlina MISLI, Haezan JANGARUN, Syahrul Nizam ADENAN, Basilios TSIKOURAS
Universiti Brunei Darussalam, Brunei Darussalam
Recently, the Government of Brunei Darussalam has recognised the need to increase agricultural productivity in line with the country's Wawasan 2035. To this end, soil conditioners and fertilisers have been used to improve the properties of naturally acidic soils. However, these practices may have unintended effects on the soil quality and public health. Geochemical analyses were conducted on 370 topsoil and 370 subsoil samples collected from a grid with a density of one sample per km2 in Brunei-Muara District to assess potential contamination. Results showed enrichments of potassium, manganese, sodium, nickel, zinc and phosphorus in agricultural topsoil, with lesser intensity in the subsoil. In order to ascertain whether the enrichment of these elements had reached concerning levels, statistics and heatmaps were used to identify threshold values and evaluate the degree of contamination. The heatmaps highlighted geochemical anomalies in the southwestern region of the District, where mostly paddy plots are found. We suggest that the geological setting has a significant role in this, as the Jerudong anticline acts as a natural barrier, trapping the aforementioned elements in the soil of its west limb. Additionally, organic matter and clay minerals contribute to the retention of these elements in the agricultural soils. Copper contents show a positive correlation with zinc, which is typically found in soils where poultry manure is applied, a practice that has been actively implemented in the country until recently. Although there were intense geochemical anomalies of these elements, the enrichment factor and geoaccumulation index suggest that the contamination is currently at a manageable level. However, if proper agricultural practices are not adopted and implemented, contamination may reach concerning levels in the near future. Therefore, it is essential that the relevant stakeholders take proactive steps to ensure that the agricultural soils remain uncontaminated and of high quality.
IG13-A003
Decomposition of Carbon Emission Driving Factors and Judgment of Peak Status in Countries Along the Belt and Road
Yuanmeng LI#+
Beijing Normal University, China
Most of the countries along the “Belt and Road” are still developing countries, and most of their carbon emissions have not yet reached their peak. However, there is currently a lack of comprehensive analysis and research to judge the current carbon peak state of the countries along the “Belt and Road” and quantify the contribution of key driving factors to the carbon emissions of the countries along the “Belt and Road”. This study fills this gap by developing a new method for judging the peak carbon status of a country based on the time series of carbon emissions. We divide the status of all countries along the Belt and Road into four categories: Has reached the peak, Peak plateau period1 (the downward trend is not significant), Peak plateau period2 (obvious recession), Not reached the peak. The results show that the main positive driving factor of the three countries that have reached the peak is GDP PPP per population, while other driving factors make negative contributions to carbon emissions. However, in some years, these countries briefly experienced a negative contribution of GDP PPP per population to carbon emissions. The driving factors of the country's carbon emissions in the Peak plateau period play a role and are not stable. The contributions of GDP PPP per population, energy intensity and carbon intensity fluctuate periodically, sometimes positive and sometimes negative. In countries that have not reached the peak of carbon emissions, population growth and economic growth are very significant positive contributors to carbon emissions, and the effect of driving factors that negatively contribute to carbon emissions is not so obvious.
IG13-A013
The Effects of Human-made and Natural Disturbances on the Eco-environment from a Global View
Yuei-An LIOU#+, Kim Anh NGUYEN
National Central University, Taiwan
It has been well recognized that human activities have negative impacts on the nature. Here, we introduce a framework to assess the eco-environmental vulnerability due to human-made and nature disturbances on a global scale with emphasis on the former factor. Since COVID-19 pandemic has caused a significant impact to the whole world in the past few years, it has been chosen to be a key influential factor in the current study. To prevent the spread of COVID-19 virus, it has been a typical measure to impact lockdown over a region, city, or even a whole country during the first couple years after pandemic outbreak except China where zero COVID-19 policy was implemented till January 2023. Under lockdown circumstance, the human activities are either significantly reduced, or even essentially ceased. In this study, global eco-environmental vulnerability maps with quantified levels before COVID-19 and during pandemic will be presented. Their comparison reveals the improved environmental conditions over the whole world as expected. The improvement, due to lockdown policy, can be considered as the benefit brought to the environment with the sacrifice of human beings’ welfare or even life. It becomes an interesting question should the human activities be ceased to protect the natural environment for the sustainable development of the world?
IG13-A015
Resilience in Response to Climate Change and Social Sustainability Assessment: Case Study of Aquaculture Industry in Pingtung, Taiwan
Li-Sheng WANG, Ching-Hsien HO#, CHIH-HENG CAI+
National Kaohsiung University of Science and Technology, Taiwan
In the event of future climate change and extreme climate hazards, the global fishery industry will have to face the compound impact caused by long- and shortterm climate hazards. With the intensification of climate change and extreme weather, however, forecasting changes in the natural environment is laden with high uncertainty and variations. Taiwan’s geographic location is favourable for aquaculture, which has evolved into an important primary industry and source of animal protein for the residents of Taiwan. Aquaculture plays a critical role in Taiwan’s aquatic product supply chain. Since 2011, the annual output of aquaculture has been maintained at approximately 310,000 tons, with a monetary value of approximately 40 billion NTD. In recent years, both long-term climate change and extreme climate hazards (for example, extremely high or low temperatures) have led to shocks to the aquaculture industry, such as environmental degradation and sudden deaths or losses of certain species, causing operational losses for fishers. The instability of and fluctuations in aquaculture, in turn, directly affect supply of and demand for aquatic products in the market. As such, this study attempts to perform a case study of aquaculture in Pingtung, Taiwan that incorporates social concern assessments of risk perception and the judgement of risk acceptance through risk management processes. Furthermore, the study incorporates stakeholder participatory processes to reduce the gap in awareness of adaptation and increase the opportunity of reaching a consensus and to develop an integrated risk management model that makes decision making better meet the actual needs of society. It is expected that these measures will enhance all parties’ willingness to adapt and help achieve the goal of public-private collaboration in facing the challenge of climate change.
IG15-A002
MIOS Radar Interferometry
Haiyong XIE1#+, Guozhu LI2, Yi LI2, Lianhuan HU2
1Institute of Geology and Geophysics, Chinese Academy of Sciences, China, 2Chinese Academy of Sciences, China
The Meteor and ionospheric Irregularity Observation System (MIOS), which consists of radar subsystem at Ledong (18.4°N, 109°E), and multi-station optical subsystem at Ledong and Sanya (18.3°N, 109.6°E), has been fully operated since December 2021. The radar subsystem includes a coherent radar with an operational frequency of 47.5 MHz and a peak power of 72 kW. It employs an active phased array consisting of 135 three-element Yagi antennas. The phased array is divided into 15 identical subarrays arranged in an area shaped like a sword. One capability of this radar is to unambiguously locate backscatter echoes using the multi-base-line spatial-domain interferometry. In order to calculate ambiguities and avoid the effects of mutual impedance, crossed subarrays 2, 4, 10, 11, and 15 with spacings of 4λ, 4.5λ and 8.5λ are used. Radar system phase offset calibration is critical to the interferometry analysis. Considering that the multi-station optical subsystem of MIOS can obtain the accurate spatial location of an ablating meteoroid. We used a common meteor and calibrated the radar system phase offsets. A good agreement between the positions of non-specular echoes derived from the radar interferometer and those of optical meteors was found, validating that the radar system phase offsets have been properly calibrated. And then, the backscatter echoes could be located accurately after the calculations of phase differences and ambiguities. Based on this work, the development of coherent radar imaging technique will be carried out in the future.
IG15-A008
Multireceiver and Multifrequency Techniques Used with VHF Atmospheric Radar for Volume Imaging
Zhen-Xiong YOU1#+, Yen-Hsyang CHU2, Ching-Lun SU2, Chien-Ya WANG3, Hiroyuki HASHIGUCHI4
1China Medical University, Taiwan, 2National Central University, Taiwan, 3Chinese Culture University, Taiwan, 4Kyoto University, Japan
Very-high-frequency (VHF) atmospheric radar is a pulsed, phase-arrayed, and powerful instrument for remote sensing of the atmosphere. In addition to clear-air turbulence and plasma echoes, precipitations and meteors are also observed frequently by such kind of radar. To improving the spatial resolution of echoes for obtaining additional information of the targets in the radar volume, observational techniques with multiple receivers and multiple frequencies are one of the approaches. Adaptive retrieval algorithms are commonly applied to these multi-channel received radar echoes, and as a result, multiple layers, multiple echo centers, and so on, in the radar volume could be resolved to some degree. In this report, high-resolution observations of the atmosphere using multireceiver and multifrequency techniques are present, including clear-air turbulence, precipitations, small-scale and wavy layer structures, field-aligned plasma irregularities, meteors, aspect sensitivity in neutral and ionospheric irregularities, and so on.
IG16-A006
Real-time Anomaly Detection in Population Data from Mobile Spatial Statistics for Disaster Mitigation
Erick MAS#+, Shunichi KOSHIMURA
Tohoku University, Japan
Observation of population dynamics is possible due to GPS technology and localization of users connected to telecommunication towers. Many studies have used GPS mobile data for various applications in multiple fields. However, those studies use samples from a particular cellphone provider or small sets of a larger population. Limited data may incorporate biases or incorrect recommendations that may be critical, at least for disaster mitigation. Another approach is Mobile Spatial Statistics (MSS) which estimates the number of people in rectangular cells (mesh) at regular intervals. MSS uses GPS-enabled devices, adoption rates, and spatial statistics to correct for biases. Thus, population counts in MSS data correspond not only to mobile phone users but also those from different providers or even with off-portable terminals. Here, we used MSS data to develop a real-time system for anomaly detection to grasp the effects of disasters on population dynamics. We discuss the challenges in this kind of application, focusing on the methodologies, event duration, the spatiality of the problem, and online implementation requirements. Finally, this study provides a step toward a Coastal Digital Twin for Disaster Mitigation. Population dynamics are followed in real-time and analyzed to flag anomalies due to possible disasters or emergencies.
IG16-A009
Investigating the Link Between the River Profile and Streambed Texture of Mixed-grain Size
Dongwoon KANG+, Kyungrock PAIK#
Korea University, Korea, South
There has been a long debate on the relationship between the concavity of river profile and the streambed texture. A school of thought claimed that the concavity increases as bed sediment size grows. Another argued exactly the opposite: the concavity diminishes as particle size increases. We aim to test which of these hypotheses is appropriate, using a whole landscape evolution model with selective transport of mixed-size sediments. We aim to run the model over geologic time scale to reproduce whole landscape evolution, under ideal tectonic and climate scenarios. The selective transport of particles causes downstream fining to emerge, and as the distribution of grain sizes changes, so does the local slope. Simulation results and in-depth scientific discussions will be presented.
IG17-A005
GEWEX and International Research Collaboration in Asia
Petrus (Peter) VAN OEVELEN#+
George Mason University, United States
The Global Energy and Water EXchanges (GEWEX) project of the World Climate Research Programme (WCRP) has for more than 30 years supported and promoted successfully international research collaboration on climate, energy and water. During these more than 3 decades a clear change in how research has evolved from more disciplinary to inter- and transdisciplinary has manifested itself. With that change the challenges regarding collaboration have grown but likewise the opportunities. In this presentation a short overview is given on past, present and future developments within GEWEX on promotion of international research collaboration and how that is relevant and applicable to the Asia and Oceania region and what are the main take away messages that can also be of use and relevance to other actors.
IG17-A009
Earth Sciences for a Sustainable Future: The AOGS Initiative in Advancing SDGs
Ping-Yu CHANG#+
National Central University, Taiwan
The Asian Oceania Geosciences Society is one of the organizations in Asia that recognizes and works towards reaching the Sustainable Development Goals (SDGs) through science cooperation. AOGS founded the Interdisciplinary Geoscience Section, which aims to collaborate with scientists studying geoscience in different disciplines, especially in sustainable approaches and studies. We are concerned with issues that can help the regional society achieve more sustainable, safe, and resilient infrastructure through the application of earth science technology and observations. One of our recent missions is to promote SDGs through geoscience research efforts. Since 2020, SDGs video contests have been held every year for students and members to promote awareness of the SDGs to the geoscience society and the general public. Participants can upload their videos to YouTube and have them evaluated by invited judges. Through new media broadcasting abilities, we hope not only to promote SDGs awareness to the public but also to recognize and promote research groups in geosciences over the Asian-Oceania region for their contribution to the SDGs.
IG17-A010
Project PIPE DREAM for Regional and International Cooperation
Yi-Shiang TZENG1#+, Wing-Huen IP1, Gilbert PI2
1National Central University, Taiwan, 2Charles University, Czech Republic
As the pace for manned missions to the Moon and Mars has been picked up, the study of space weather effects has also gained more and more attention in the context of interplanetary travels and lunar and Martian settlements. These considerations lead to the discussion of necessary deployments of small spacecraft and/or CubeSats at the Sun-Earth L4 and/or L5 Lagrangian points for solar and heliospheric observations. The basic idea is that the L5 point provides the best vantage point for viewing the eastern limb of the sun, thus allowing a high-precision forecast of space weather effects due to the impact of geoeffective CME impacting the Earth's magnetosphere. On the other hand, the L4 point is the best place to monitor extreme SEP events occurring on the west limb at ~ W60, with GeV ions capable of causing ground-level events (GLEs) on Earth, which are also dangerous to the Moon and Mars explorers. It is therefore clear that in the coming decades, we will see spacecraft stationing at different strategic positions around the Earth's orbit (or beyond) to provide inputs to space weather forecasts on an interplanetary scale. This is also the meaning of PIPE DREAM for "Patrolling Interplanetary Explorers and Deep-space Research Mission." In this presentation, we will discuss how Project PIPE DREAM representing a large-scale international cooperation might be realized by combining the solar space observatory missions to be launched and under planning by different space organizations.
OS01-A002
Interactions Between Ocean and Successive Typhoons in the Kuroshio Region in 2018 in Atmosphere–ocean Coupled Model Simulations
Yuma KAWAKAMI1#+, Hideyuki NAKANO1, Shogo URAKAWA1, Takahiro TOYODA2, Kei SAKAMOTO2, Hiromasa YOSHIMURA1, Eiki SHINDO1, Goro YAMANAKA2
1Meteorological Research Institute, Japan, 2Japan Meteorological Agency, Japan
Typhoons decrease sea surface temperature (SST) along their wakes through upwelling of subsurface water, vertical mixing in the upper ocean, and heat release from the sea surface, and these cold wakes can influence subsequent typhoons. In this study, we investigated interactions between the upper ocean and typhoons in the North Pacific subtropical gyre with focuses on Kuroshio's response and feedback using atmosphere–ocean coupled model simulations. In late August and early September 2018, typhoons SOULIK, CIMARON, and JEBI passed through the northwestern subtropical gyre. During the passages of SOULIK and CIMARON, SST decreased along their paths due to vertical mixing except in the Kuroshio region. We quantitatively revealed that the Kuroshio stayed warm because the deep mixed layer along its path and small vertical temperature gradient around the mixed layer base, which are unfavorable conditions for cooling by vertical mixing, limited the cooling effects. After SOULIK and CIMARON had passed, SST recovered through horizontal Kuroshio heat transport and radiative heating. The possibility that the SST field after SOULIK and CIMARON passages influences JEBI was also discussed. Although impacts on JEBI intensity were not identified, it is implied that the turbulent heat flux (THF; sum of the sensible and latent heat fluxes) around JEBI was modulated by the SST field: heat release from the ocean was reduced in the region with decreased SST and enhanced over the sustained high SST of the Kuroshio. Furthermore, the large THF over the Kuroshio may have caused an increase of JEBI-associated precipitation around Japan.
OS01-A012
Typhoon Hinnamnor Interacting with Underlying Marine Heatwaves
Saranya J.S., Sung-Hyun NAM#+
Seoul National University, Korea, South
Typhoons draw their energy from underlying warm oceans. In a warming climate, oceans are often experiencing extreme sea surface temperature conditions known as marine heatwaves. The interactions between typhoons and marine heatwaves constitute a significant concern in a changing climate and require immediate attention. Typhoon Hinnamnor was a severe typhoon that interacted with underlying marine heatwave conditions near the Korean strait before hitting the southern part of the Korean Peninsula on September 6, 2022; it is an excellent case to study the interaction between typhoons and marine heat waves. After reaching maximum intensity in the open ocean, typhoon Hinnamnor started moving northward from September 2 towards the Korean strait and initially declined its strength. However, the typhoon reintensified from September 3 to September 5, increasing the maximum wind speed from 75 kt to 90 kt in the presence of underlying marine heatwave (MHW) conditions. This study resolves the crucial ocean-atmosphere interactions during the typhoon's intensification and decay in the presence of marine heat waves. We analyzed in-situ time-series observational data observed at multiple locations in the seas around the Korean Peninsula along with the ECMWF Reanalysis v5 (ERA5) reanalysis data before, during, and after the typhoon passage. Results show that increased latent heat flux from the ocean to the atmosphere associated with the MHWs in the Korea Strait sustained the typhoon's high intensity. In contrast, the MHWs decayed abruptly due to strong typhoon wind-induced vertical mixing (mixed layer thickened from 10 m to 30 m) and sea surface cooling up to 2.72 °C. Our results provide a case study on the interactions between two major extreme events in the climate system, providing crucial insights into the interplay between MHWs and typhoons and their combined impacts on the coastal environments and marine ecosystems.
OS01-A014
The Upper Ocean Response Due to Three Sequential Tropical Cyclones in the Bay of Bengal
Abhishek KUMAR#+, Arun CHAKRABORTY, Biplab SADHUKHAN
Indian Institute of Technology Kharagpur, India
The physical and biological response of the three sequential tropical cyclones(TCs) was investigated in the Bay of Bengal region using in-situ observations, multi-satellite data, and biogeochemistry model outputs from November-December 2013. We looked at the responses of TC Helen, Lehar, and Madi. The Lehar cyclone formed in the Andaman Islands soon after storm Helen made landfall, whereas the Madi cyclone formed eight days after the Lehar cyclone dissipated. Helen and Lehar's journey lowered the sea surface temperature (SST) by 1°C. Despite this, the SST in the region stayed over 26.5°C, allowing cyclone Madi to develop. The initial chlorophyll-a (CHL-a) boost was linked to CHL-a redistribution associated with TC-induced vertical mixing and Ekman pumping at the base of the mixed layer post-TC Helen and Lehar. Following TC Madi, Ekman pumping, entrainment, and eddy pumping pushed nutrient-rich cold waters into the euphotic layer, resulting in a more spectacular CHL-a bloom and net primary production. Upwelling was the principal strategy for replenishing nutrients towards the right side of the cyclone track channel. The near-surface dissolved oxygen content has increased significantly as a result of TC-induced vertical mixing and enhanced CHL-a photosynthesis. The consecutive cyclones' turbulence mixing and upwelling were principally responsible for preserving the lower temperature region and phytoplankton blooms. The study's goal is to deduce the reactions to these three consecutive TCs and their related physical works for phytoplankton growth and sea surface cooling.
OS01-A018
Downcoast Redistribution of Changjiang Diluted Water Due to Typhoon Chan-Hom (2015)
Yunpeng LIN1+, Yunhai LI2, Shuai CONG3, Meng LIU1, Liang WANG4, Binxin ZHENG4, Jingping XU1#
1Southern University of Science and Technology, China, 2Ministry of Natural Resources, China, 3Ocean University of China, China, 4State Oceanic Administration, China
Typhoons are known to substantially influence the coastal circulation and the associated biogeochemical processes. The transport of Changjiang Diluted Water (CDW), an important source to the coastal current in the East China Sea (ECS), varies markedly under the influence of typhoons. This study quantitively details the downcoast transport of CDW driven by Typhoon Chan-Hom in the summer of 2015. Salinity measurements 3 days after the typhoon’s passage showed the presence of a large volume of low salinity water, up to 70 km wide and 20 m thick along the Zhejiang-Fujian coastal area with an estimated freshwater volume of 3.7×1010 m3. A three-endmember mixing model shows that the CDW’s contribution to the study area’s surface waters (<10 m) immediately after the typhoon was as high as 40% (average 32%), much greater than the contribution under normal summer conditions of 8% (average 3%). The vast spreading of CDW along the Zhejiang-Fujian coast created a strong stratification in the upper water column that limited the diffusion of CDW in the study area. The calculated and observed results suggest that these abnormal low salinity water could stay in the study area for 13-21 days. Additional nutrients in the CDW elevated the Chlorophyll-a concentration in the upper water column (mean 3.74 mg m-3) and produced large amount of particulate organic carbon (POC).
OS01-A020
Decrease of Annually Accumulated Tropical Cyclone-induced Sea Surface Cooling and Diapycnal Mixing in Recent Decades
Xueyang ZHANG+, Fanghua XU#, Yanluan LIN, Jishi ZHANG
Tsinghua University, China
Tropical cyclones (TCs) are an important source of turbulent mixing for the upper ocean at low latitudes, causing sea surface cooling and subsurface warming. A new estimate of annually accumulated sea surface cooling and upper ocean diapycnal diffusivity induced by TCs is obtained by using quantified cold wake sizes, which were largely ignored by previous studies. Both the annually accumulated tropical cyclone-induced sea surface cooling and upper ocean diffusivity on a global scale show a significant decreasing trend over the period of 1982–2016, at a rate of −0.09 ± 0.03 °C/decade and −0.03 ± 0.01 cm2/s/decade respectively. The strengthening of ocean stratification with global warming contributes to the decrease of sea surface cooling and mixing, while the changes of tropical cyclone characteristics (such as translation speed, intensity, number, lifetime and size) contribute differently in various ocean basins.
OS01-A025
Sea Surface Salinity Response to Typhoons in the Northwest Pacific Using Satellite Salinity Data Over the Past Decade
Kyung-Ae PARK1#+, Jae-Jin PARK1, Wenqing TANG2
1Seoul National University, Korea, South, 2Jet Propulsion Laboratory/California Institute of Technology, United States
To investigate the potential use of satellite salinity data in studying the oceanic response to typhoons in the Northwest Pacific, the accuracy of such data was assessed by comparing it with Argo float and buoy observations over the past decade (2011-2020). The findings revealed that satellite salinity data from SMAP (Soil Moisture Active Passive) and Aquarius exhibited relatively high accuracy, particularly during the summer season and in low-latitude subtropical seas. However, despite these encouraging results, the usefulness of satellite salinity data during the typhoon season is constrained by certain limitations. To delve deeper into the topic, a comprehensive analysis was conducted on a selection of typical typhoons over the past decade, employing objective classification based on parabolic trajectories. The oceanic response to these typhoons was examined. Both Aquarius and SMAP satellites demonstrated a salinization pattern on the right side of the typhoon path, while desalination occurred on the left side. Notably, areas of reduced salinization corresponded to regions experiencing intense precipitation to the left of the typhoon's center. Additionally, there was an inverse relationship between precipitation and satellite salinity, with a salinity desalination-to-precipitation rate ratio estimated at approximately -0.0401 psu mm-1 h-1. Analyzing the vertical distribution of Argo data before and after typhoon events revealed distinctive cooling in the surface layer of seawater following a typhoon's passage. The depth of the mixed layer increased, and freshening phenomena were observed on the left side. Furthermore, transforming the coordinate system along the typhoon's path and examining the atmospheric environment exposed a localized freshening phenomenon appearing slightly ahead and to the left of the typhoon's center.
OS01-A026
Satellite Significant Wave Height Variations during Typhoon Period in the Northwest Pacific
Hye-Jin WOO, Kyung-Ae PARK#, Hee-Young KIM+, Ji-Hyun LEE, Sunwoo KIM, Park HYEWON
Seoul National University, Korea, South
The Northwest Pacific has a variety of ocean and atmospheric phenomena which show obvious spatial and temporal variability of significant wave height (SWH). In addition, the Northwest Pacific is one of the oceans with the most frequent high-intensity tropic cyclones. The typhoons are accompanied by heavy rains and huge waves as well as strong winds, which have a great impact on the coastal environment. As the intensity of typhoons is becoming stronger due to climate change, extreme wave height induced by typhoons and hazardous events can also increase in the Northwest Pacific. However, in spite of the urgent need to understand the characteristics of the extreme height in the region where typhoons occur frequently, studies on the estimation of extreme SWH in the Northwest Pacific are insufficient. In this study, the 100-year return period of SWHs was estimated by applying the Peak over Threshold method (PoT) as one of representative extreme value analysis to satellite altimeter data from 1992 to 2016. To analyze the suitability of the PoT method in the Northwest Pacific, where typhoons frequently occur, the estimated PoT-derived SWHs were compared with the maximum SWHs within the upper 0.1% of satellite observations. It was suggested that PoT method could be applied to reliably estimate the extreme SWH using the accumulated satellite observation SWH data in the Northwest Pacific.
OS02-A006
An Improved Parameterization of Wind-driven Turbulent Vertical Mixing Based on an Eddy-resolving Climate Model
Man YUAN1+, Zhuo SONG1#, Zhao JING1, Zhuoran LI1, Ping CHANG2, Bingrong SUN1, Hong WANG1, Xin LIU3, Shenghui ZHOU4, Lixin WU1
1Ocean University of China, China, 2Texas A&M University, United States, 3Qilu University of Technology (Shandong Academy of Sciences), China, 4Pilot National Laboratory for Marine Science and Technology (Qingdao), China
Turbulent vertical mixing in the stratified ocean interior has a huge impact on global ocean circulations and the climate system. Although parameterizations of vertical mixing furnished by internal tides have been built into state-of-the-art coupled global climate models (CGCMs), efforts in parameterizing wind-driven vertical mixing in CGCMs are still limited. In this study, we apply a modified finescale parameterization (MFP) to an eddy-resolving Community Earth System Model (CESM) to represent the wind's contribution to vertical mixing in the stratified ocean interior. The spatial pattern of the MFP-parameterized wind-driven vertical mixing in the thermocline agrees with the observation derived from the finestructure measurements of Argo floats, reproducing the enhanced values in the Kuroshio, Gulf Stream extensions, and the Southern Ocean where the winds inject great amount of energy into the internal wave field. The MFP also captures the observed seasonal variation of wind-driven vertical mixing in the thermocline of these regions that exhibits enhancement and weakening in winter and summer, respectively. Application of the MFP to a non-eddy-resolving CESM fails to reproduce the observed wind-driven vertical mixing. Specifically, the magnitude of parameterized wind-driven vertical mixing in the thermocline of Kuroshio, Gulf Stream extensions, and the Southern Ocean is systemically smaller than those in the observation and eddy-resolving CESM; so is the case for the amplitude of seasonal cycle. The results highlight the benefit of eddy-resolving CESM compared to its standard-resolution counterpart in parameterizing the wind-driven vertical mixing and provide insight into developing parameterizations for wind-driven vertical mixing in eddy-resolving CGCMs.
OS02-A010
Extreme Ocean Mixing in Coastal Seas
Arnaud VALCARCEL1+, Joanne O'CALLAGHAN2, Ata SUANDA3, Glenn CARTER4, Cynthia BLUTEAU5,6, Fiona ELLIOTT7, Craig STEVENS8,9#
1Oceanly, New Zealand, 2OceanlyScience, New Zealand, 3University of North Carolina Wilmington, United States, 4University of Hawaii, United States, 5Innovation Maritime, Canada, 6University of Quebec, Canada, 7University of Bergen, Norway, 8National Institute of Water and Atmospheric Research, New Zealand, 9University of Auckland, New Zealand
Turbulence-driven mixing is an essential mechanism that regulates energy transformations in the ocean and its role in the global climate. Mixing matters crucially in coastal seas, key regions of the Earth system for biological productivity and atmospheric carbon uptake. There, winds and tides can stimulate energetic turbulence in boundary layers that can interact in the interior, regulating stratification, air-sea exchanges and nutrient fluxes. The magnitude of diapycnal diffusivity, the central quantity to estimate vertical fluxes of heat and mass in the ocean, is scaled by a mixing efficiency factor often assumed to be constant. The efficiency of extreme turbulent mixing driven by high winds and fast tidal flows were investigated in an energetic ocean passage, Te Moana o Raukawa (Cook Strait, Aotearoa - New Zealand), using an extended glider dataset of in situ turbulent rates and background flow conditions, and atmospheric wind records. > 15 m/s winds and > 1.5 m/s depth-integrated tides intensified turbulence (buoyancy Reynolds numbers, Reb, up to 10^8) and extended boundary influence (a function of the Ozmidov scale, of isotropic turbulent motions) to the full water depth. For most samples, mixing efficiency coefficient (Γ) values were reduced by up to 3 orders of magnitude from the widely-used canonical Γ = 0.2 (Rf = 0.16) value. Lower energy turbulent patches free from boundary influence (i.e. Ozmidov-limited) operated with significant scatter within a standard deviation of Γ = 0.2. Moderately energetic surface or bottom boundary-influenced samples affirmed the Γ ∝ Reb^(−1/2) relationship of shear-driven turbulence. Extremely energetic turbulence influenced by both boundaries revealed a new regime for mixing efficiency variability, decreasing drastically along Γ ∝ Reb^(−9/10). The results presented here have the potential to inform how mixing efficiency parameterizations should be treated in global ocean models.
OS02-A013
Large Eddy Simulations of Ocean Vertical Mixing in the Transition Region Between Coastal and Open Oceans
Zheng WEI1+, Qing LI2#, Bicheng CHEN3
1The Hong Kong University of Science and Technology (Guangzhou), China, 2The Hong Kong University of Science and Technology, China, 3Xiamen University, China
Ocean vertical mixing is driven by complex forcings such as winds, buoyancy, and tides, and modulates the vertical exchange of energy and substance in the ocean. Physical processes that drive ocean vertical mixing are too small to be resolved in ocean general circulation models and are often parameterized. Such parameterization can be divided into two categories: bulk models and differential models. However, both categories have limitations in representing the vertical mixing in the transition region between the coastal ocean, where mixing extends throughout the whole water column, and the open ocean, where the surface and bottom boundary layers are well separated. In the transition region, the surface and bottom boundary layers can develop, interact with each other, and even merge into one layer. Nevertheless, the physical mechanisms behind this process have not been clarified. We have been using large eddy simulations to investigate the evolution of boundary layer turbulence in such transition region. Preliminary results of the turbulent kinetic energy budget analysis indicate that internal waves are generated in the stratification layer between the surface and bottom boundary layer and may play a role in the energy transfer process between the two layers. Results of large eddy simulations of boundary layer turbulence in such transition region under more complex conditions, such as changing wind forcing, surface buoyancy flux, and tides, and including the effect of topography, will be discussed. The goal is to explore the parameter space to provide basic knowledge for further improvement of ocean vertical mixing parameterizations in such transition region.
OS02-A023
The Internal Surfzone in Regional Ocean Models
Ata SUANDA#+
University of North Carolina Wilmington, United States
Realistic regional-scale ocean modeling uses the hydrostatic approximation and turbulence closure such that it does not resolve all scales of turbulence nor the dispersive aspects of coastal internal waves. Despite these limitations, output from these numerical models are what is available through regional ocean observing networks, used to forecast water properties and provide stakeholders with valuable predictions of oceanic conditions. Particularly in regions with strong internal waves, we must better understand both resolved and unresolved mixing in coastal models and improve representations of internal wave driven mixing. A recent observation-based parameterization suggests that wave-averaged, depth-integrated coastal internal wave dissipation is equivalent to internal wave energy flux divergence (Becherer et al., 2022). In this framework, a self-similar “internal surf zone” develops shoreward of an internal wave energy-saturated water depth that is a function of mean stratification and internal tide energy flux, both properties available from tidal-resolving numerical models. In this presentation, a series of shelf-focused numerical simulations of shoreward-propagating internal tides will be conducted and analyzed to quantify the kinematic similarity between the observational parameterization the internal surfzone and what is produced by the hydrostatic, RANS-type of regional models. Where available, observations of internal wave dissipation will also be discussed.
OS02-A025
Tides and Tidal Mixing at the Shelf Break in the Timor Sea North of Australia
Robin ROBERTSON#+
Xiamen University Malaysia, Malaysia
In order to characterize the tidal fields and mixing over the shelf and at the shelf break in the Timor Sea, three 51 hour time series of CTD/LADCP/VMP profiles were conducted. The shelf break and one of the shelf time series occurred during spring tide and the other shelf break time series occurred during neap tide. The time series alternated using the CTD/LADCP or VMP at two hour intervals, so a profile was collected at hourly intervals. Semidiurnal tides dominated all three time series with the hydrography changing with the tides due to tidal advection. There was also energy at 4 cpd. Intrusions of different water types occurred at various depths, indicating the generation of different water types nearby. Anomalies in temperature and salinity propagated deeper in the water column with time, indicating upward propagation of energy. Both tidal advection, intrusions, and the anomalies were stronger during spring tide. Surprisingly, mixing was just as strong during neap tides as spring tide.
OS02-A028
Estimating Diapycnal Mixing Parameters of the Eddy Regions in the Western Arctic Ocean by Using Multi-channel Seismic Reflection Method
Shun YANG1#+, Haibin SONG1, Bernard COAKLEY2, Kun ZHANG1
1Tongji University, China, 2University of Alaska, Fairbanks, United States
Turbulence mixing is considered to be an important process for maintaining oceanic overturning circulation. In recent years, the sea ice cover in the Arctic Ocean has decreased sharply, resulting in the enhancements of turbulent mixing and eddy activities. However, due to the scarcity of observations, our understanding of turbulent mixing in the ocean is still insufficient. In this work, 11 eddies are identified in the ice-free Chukchi borderland of the western Arctic Ocean using concurrent multi-channel seismic reflection data and the current velocity derived from an ADCP (Acoustic Doppler current profiler). These eddies have a horizontal scale of ~10 km, which is consistent with the local Rossby radius, so they are all mesoscale eddies. Most of these eddies are anticyclonic eddies in the halocline, consistent with existing studies. Turbulent dissipation rate can be estimated by tracing seismic events and fitting the slope spectrum of seismic events and Bachelor spectrum. Then, according to the Osborn’s method, the diapycnal diffusivity Kρ is obtained. The results show that the turbulent mixing around eddies is generally strong. Kρ at the upper boundary of eddies is high, and can reach 1×10-4 m2s-1, which may be caused by strong vertical shear. However, there is no obvious mixing enhancement at the lower boundary of eddies with strong shear, which may be caused by the underestimating buoyancy frequency at the lower boundary. Kρ at the edge of eddies is strong, which may be the result of the thermohaline intrusion or eddy stirring. Uncertainty calculations indicate that estimating turbulent mixing using seismic events is a reliable method. Given the scarcity of turbulence observation in the ocean at present, there is great potential for the application of a large number of historical seismic data in the global oceans.
OS02-A029
The Characteristics and Enhanced Diapycnal Mixing of a Cyclonic Eddy Offshore Southeast North Island, New Zealand from Multichannel Seismic Data
Kun ZHANG#+, Haibin SONG, Linghan MENG, Shun YANG
Tongji University, China
Mixing induced by mesoscale eddies impacts the climate and ecosystems profoundly. Multichannel seismic (MCS) data can provide high-resolution acoustic images of thermohaline fine structures in the water column, known as seismic oceanography. In this study, we analyzed a cyclonic eddy captured by the MCS data acquired on November 8th and 9th, 2017, offshore southeast of North Island, New Zealand. A concave-down structure with strong dipping and weak reflections on seismic section is identified as a typical eddy structure in the study region. The eddy has a width of over 120 km and a thickness of about 1500 m. The strong dipping reflections representing submesoscale features (e.g. fronts and filaments) at the periphery of the eddy. We used sea surface height and geostrophic current velocity derived from satellites to detect eddies in the study region. The location of the concave-down structure matched the cyclonic eddy, with a lifetime of over 30 days. To diagnose eddy activities in the region, we used physics reanalysis data from Copernicus Marine Service and Hybrid Coordinate Ocean Model. Both showed a negative Okubo-Weiss parameter at the location of the cyclonic eddy. The sea surface chlorophyll concentration derived from Aqua-MODIS satellite showed high-value spiral bands at the location of the eddy, indicating enhanced primary production in the eddy region. We computed horizontal wavenumber spectra from vertical displacements of tracked seismic reflections to estimate the diapycnal mixing rate. The mean diapycnal diffusivity in the eddy region had an average level of O (10-3.9) m2s-1, much higher than that of the open ocean. The mean diapycnal diffusivity showed a patchy distribution in the front and filament region. These findings may contribute to a better understanding of the process of energy cascade and eddy pumping in enhancing primary production in the ocean.
OS02-A030
Calculation and Analysis of the Horizontal Dispersion Coefficient in Yueqing Bay
Jia LI1#+, Yanming YAO2, Tao ZHANG1
1Ministry of Natural Resources, China, 2Zhejiang University, China
In coastal waters, the dispersion process was not longitudinal one-dimensional like in rivers, but expended horizontal two-dimensional. Based on the research result of the longitudinal dispersion process in rivers, a method to calculate the horizontal dispersion coefficient was inferred theoretically. Then a three dimensional model is used to simulate the tidal circulation in Yueqing Bay, combined with the output of which, the temporal and spatial distribution of horizontal dispersion coefficient in the bay was obtained. The analysis result indicated that the topographic influence to the horizontal dispersion appeared the character of duality: one is the positive correlation, the other is that there is some relationship between the marked changed in topography and the horizontal dispersion. At the same time, the velocity is an important factor for the horizontal dispersion, too. There is also the positive correlation between them and the tidal range and vertical distribution of the tidal current are important factors simultaneously. Furthermore, it is found that the horizontal dispersion coefficient can be estimated using an expression constructed by vertical mean velocity, tidal range and water depth.
OS03-A001
Effects of Climate Variability in Marine Ecosystems as a Bottom-up Control Regulator in the Pacific Ocean
Kuo-Wei LAN1#+, Yan-Lun WU1, Ting-Yu LIANG1, Lu-Chi CHEN2
1National Taiwan Ocean University, Taiwan, 2Fisheries Research Institute, Taiwan
How top predators behave and are distributed depend on the conditions in their marine ecosystem through bottom‐up forcing; this is because where and when these predators can feed and spawn are limited and change often. This study investigated how the catch rates of immature and mature cohorts of bigeye tuna (BET) varied across space and time; this was achieved by analyzing data on the Taiwanese longline fishery in the western and central Pacific Ocean. We also conducted a case study on the time series patterns of BET cohorts to explore the processes that underlie the bottom-up control of the pelagic ecosystem that are influenced by decadal climate events. Wavelet analysis results revealed crucial synchronous shifts in the connection between the pelagic ecosystem at low trophic levels in relation to the immature BET cohort. Many variables exhibited decreasing trends after 2004–2005, and we followed the Pacific Decadal Oscillation as a bottom-up control regulator. The results indicated that low recruitment into the mature cohort occurs 3 years after a decrease in the immature cohort’s food stocks, as indicated by a 3-year lag in our results. This finding demonstrated that, by exploring the connection between low-trophic-level species and top predators at various life stages, we can better understand how climate change affects the distribution and abundance of predator fish.
OS03-A010
Ningaloo Niño/Niña in CMIP6 Models: Characteristics, Mechanisms, and Climate Impacts
Jiaqing XUE1#+, Hongpei YANG2, Jing-jia LUO1, Chaoxia YUAN1, Boni WANG3, Toshio YAMAGATA4
1Nanjing University of Information Science & Technology, China, 2Sun Yat-sen University, China, 3Jiangsu Meteorological Service Center, China, 4Japan Agency for Marine-Earth Science and Technology, Japan
As a dominant climate mode of the southeast Indian Ocean, Ningaloo Niño/Niña has paramount impacts on regional climate and marine ecosystems. Using outputs from the latest phase of Coupled Model Intercomparison Project (CMIP6), we have systematically evaluated the simulation of Ningaloo Niño/Niña in the state-of-the-art coupled models. Eighteen out of 28 CMIP6 models well reproduce the spatial pattern and seasonality of Ningaloo Niño/Niña, whereas the simulated amplitudes show large spread across the models. Main processes of the oceanic and atmospheric El Niño-Southern Oscillation teleconnections and the coastal Bjerknes feedback are successfully captured by most of the CMIP6 models, but their uncertainties in the simulation are responsible for the inter-model difference in amplitude. The CMIP6 models are also skillful in reproducing the regional climate impacts of Ningaloo Niño/Niña. Compared to Coupled Model Intercomparison Project Phase 5, a larger fraction of models in CMIP6 well reproduce the Ningaloo Niño/Niña, which provides a good hope for projecting its future changes.
OS03-A027
The Modulations of the Pacific North Equatorial Current Bifurcation by Interannual-to-decadal Climate Variability
Li-Chiao WANG#+
National Central University, Taiwan
Long-term reanalysis data were used to assess interannual-to-decadal modulations of the North Equatorial Current (NEC) bifurcation in the Pacific. Wind stress curl anomaly (WSCA) in the region of 10N–15N and 160E–170E (C-BOX) generates oceanic Rossby waves and affects the NEC bifurcation along the Philippine coast. Our analysis results show that oceanic Rossby waves are preferentially generated in either the negative Pacific Decadal Oscillation (PDO) phase when the El Niño–Southern Oscillation (ENSO) signal dominates, or in the positive PDO phase when the ENSO signal is overshadowed. In the phase when the positive PDO counteracts with the ENSO signal, neither ENSO nor PDO has a significant influence on oceanic Rossby wave generations through the WSCA. Moreover, our further analysis revealed that the WSCA has also been remotely modulated by the Southern Annular Mode (SAM). It is demonstrated that the SAM shifted to its positive phase at this transition and began strongly impacting the WSCA in the C-BOX and the NEC bifurcation. During the positive SAM phase after the early 1990s, strong climate variability occurred in the tropical to the subtropical area of the North Pacific, with a clear footprint connected to the Antarctic region. During the positive SAM phase, a dipole sea surface temperature pattern was generated in the South Pacific; this induced an atmospheric Rossby wave train in upper-level wind shear that propagated northward to the North Pacific. Such effects further enhanced downward motion and divergence at the surface, intensifying the easterlies in the equatorial area and the anticyclonic WSCA in the C-BOX. The anticyclonic WSCA in the C-BOX substantially excited downwelling oceanic Rossby waves at the surface, inducing an equatorward trend of NEC bifurcation after the early 1990s.
OS03-A028
Early Warning of the Indian Ocean Dipole Using Climate Network Analysis
Zhenghui LU#+
National Institute of Natural Hazards, Ministry of Emergency Management, China
The Indian Ocean Dipole (IOD), an air-sea coupled phenomenon over the tropical Indian Ocean, has substantial impacts on climate, ecosystem and human society. Due to the winter predictability barrier, however, a reliable prediction of the IOD has been only limited with three or four months in advance. Our work approaches this problem from a new data driven perspective, the climate network analysis. Using this network-based method, an efficient early warning signal for the IOD event was revealed in boreal winter. As a result, our finding can correctly forewarn the IOD events from December of the previous year with one calendar year in advance with a hit rate of higher than 70%, which strongly outperforms that of the current dynamical models.
OS03-A032
Impacts of Diverse El Niño Events on North Tropical Atlantic Warming in Their Decaying Springs
Weihao GUO#+
South China Sea Institute of Oceanology, China
Previous studies have demonstrated that North Tropical Atlantic (NTA) warming can be modulated by El Niño events through atmospheric teleconnections. Considering the diversity of El Niño events, this study focuses on different responses of the NTA sea surface temperature (SST) to eastern Pacific (EP), central Pacific type I and type II (CP‐I and CP‐II) El Niño events in their decaying springs. In EP and CP‐II El Niño events, the pattern of NTA warming is well established, while the NTA SST fails to warm in CP‐I El Niño events. In EP and CP‐II El Niño events, anomalous cyclones can be excited in the subtropical Atlantic. Consequently, anomalous southwesterly winds in the NTA weaken the background northeasterly winds and suppress oceanic latent heat loss, leading to NTA warming. However, in CP‐I El Niño events, anomalous anticyclones are excited in the subtropical Atlantic and anomalous northeasterly winds in the NTA strengthen the background northeasterly winds, which facilitate oceanic latent heat loss and lead to NTA cooling. The inconsistent remote atmospheric responses of the NTA are attributed to the different patterns of warm and/or cold SST anomalies in the tropical Pacific in the decaying springs of different types of El Niño events. The physical mechanism linking the SSTs in the tropical Pacific and the NTA has been verified in a slab ocean model.
OS03-A034
Upper Arctic Ocean Properties and Relationships with Sea Ice in CMIP6 Historical Simulations
Wei CHENG#+
University of Washington, United States
While current-generation CMIP and OMIP models have biases in their upper Arctic Ocean hydrography, it is less clear how these biases impact the models' ability to simulate the observed Arctic sea ice. In this study we seek to quantify relationships between sea ice and ocean states in CMIP6 historical simulations and identify common model behaviors. Multi-model mean (MMM) simulations exhibit accelerated changes in the ice and ocean system since the late 20th century. Underlying the MMM is strong inter-model variation in the simulated ice and ocean mean states, trends, and variability. However, despite the inter-model differences, simulations show consistent relationships between upper ocean property and sea ice changes, in particular, there is a common ratio between sea ice reduction and upper ocean warming or stratification increase across the models. Our results highlight the urgent needs for reliable Arctic Ocean observations or data products in order to better contextualize modeling results.
OS04-A003
Surge Residuals at the Singapore Coast
Zhi Yang KOH#+, Benjamin GRANDEY, Lock Yue CHEW
Nanyang Technological University, Singapore
We analyse the non-tidal residual at Singapore’s coast using tide gauge records at Tanjong Pagar from 1999 to 2018 and at Johor Bahru from 1993 to 2013. Using harmonic analysis software UTide to estimate the tidal time series, we find that coastal water level has deviated from tidal predictions by more than ±600 mm in the past. The greatest deviations are caused by phase differences between the tidal time series and the tide gauge time series. Extreme exceedances are found to occur more frequently 4 to 6 hours before high tide at Tanjong Pagar and 4 to 7 hours before high tide at Johor Bahru, with frequency peaking at 5 hours before high tide at both locations. This shows that tides are arriving earlier than the predictions from harmonic analysis, but whether this is caused by tide-surge interactions warrants further study.
OS04-A006
Estimation of Tidal Energy Flux Change Related to the Tidal Flat Reclamation in the East China Seas
Byoung Jun LIM#+, You-Soon CHANG
Kongju National University, Korea, South
This study simulated tidal energy flux change in response to tidal flat reclamation of Jiangsu Shoalwater coast and Gyeonggi Bay in the East China Seas using MOHID (MOdelo HIDrodinâmico) ocean circulation model. Based on previous studies and historical coastal information maps, we carried out several numerical experiments with reliable coastal topography change around these two areas.
Results show the different tidal energy redistribution processes. The energy flux from Gyeonggi Bay disperses in the open sea, but most of it remains inside the Yellow Sea. This residual energy steadily increases the tidal amplitude in the Yellow Sea with the tidal flat disappearance. Most of the tidal energy flux from the Jiangsu Shoalwater coast was found to pass out of the East China Sea through the South Sea of Korea, which caused a sea level decrease in the East China Sea. This result indicates that coastal topography change in a specific area can cause sea level change in the surrounding area as a far-field effect through the tidal energy redistribution process and its modification.
OS04-A007
Sea Level Variability Along the Western Coast of India Simulated in a High-resolution Ocean General Circulation Model
Yoko YAMAGAMI#+, Tatsuo SUZUKI, Hiroaki TATEBE
Japan Agency for Marine-Earth Science and Technology, Japan
Sea level variability along the coast of India is influenced by the coastal Kelvin wave. Wind forcing around the southern tip of India and east of Sri Lanka dominates seasonal variability (Suresh et al., 2016), while intraseasonal variability is mainly driven by equatorial forcing (Suresh et al., 2013). As sea level rise in the northern Indian Ocean is projected to be faster than the global average (IPCC AR6), the densely populated coastal areas will face serious risks from coastal storm surges and extreme tidal events in the future. However, most climate projections are based on climate models with a horizontal resolution in the ocean of about 1°. Therefore, it should be closely examined whether standard climate models can adequately represent coastal sea level variability due to coastal Kelvin waves. In this study, we examine the sea level variations in the northern Indian Ocean based on a comparison of non-eddying and eddy-resolving Ocean General Circulation Model (OGCM) experiments. We find that the eddy-resolving OGCM can better simulate the intraseasonal and seasonal sea level variability in the Indian Ocean. In particular, the eddy-resolving OGCM can reproduce intraseasonal extreme sea level events along the western coast of India that are underestimated by the non-eddying OGCM. The intraseasonal sea level variation is explained by a coastal Kelvin wave from the equatorial ocean in the eddy-resolving OGCM, which is consistent with previous studies based on a linear stratified model. However, the non-eddying OGCM does not simulate the propagation of coastal Kelvin waves in the Bay of Bengal due to its coarse resolution. This study implies that current climate models tend to underestimate the extreme sea level events and thus the future risks of sea level rise in the coastal region of India.
OS04-A008
The Evaluation of Sea Level Budget in the Northwestern Pacific Marginal Seas
Hyeonsoo CHA1#+, Jae-Hong MOON1, Taekyun KIM1, Yuhe Tony SONG2
1Jeju National University, Korea, South, 2California Institute of Technology, United States
Despite of recent advances in observation for underlying processes in the global mean sea-level rise (SLR), the process-based assessment on regional scales is challenging due to the physical processes having spatial and temporal variability. Understanding and quantifying these processes are important to projecting sea-level change and improving the basis for future vulnerability. In this study, we estimate the underlying process of the regional sea level rise on the northwestern Pacific marginal seas and assess whether the regional SLR budget can be closed with a combination of observation and ocean reanalysis datasets. The process-based budget assessment shows that the ocean mass change between deep ocean and shallow marginal seas, which are playing a role in driving regional SLR trend and its variability along the continental shelves. In this presentation, we will further discuss the sterodynamic estimation can be decomposed into two major processes (local steric sea level change and ocean mass redistribution) based on an observational approach.
OS04-A009
Sea-level Trends at Nine Southeast Asian Coastal Cities from 1993 to 2018
Trina NG1,2#+, Dhrubajyoti SAMANTA2, Julius OELSMANN3, Nidheesh GANGADHARAN1, Tanghua LI2, Aurel MOISE1, Benjamin HORTON2,4
1Centre for Climate Research Singapore, Singapore, 2Nanyang Technological University, Singapore, 3The Technical University of Munich, Germany, 4Rutgers University, United States
Global mean sea level has been rising since the 19th century, but this rate of change is not uniform across the globe. Ocean dynamics, Gravity, Rotation and Deformation (GRD) effects of land ice and water mass distribution on the Earth’s surface, and vertical land motion are processes that influence relative sea-level rise on a local scale over varied temporal periods. For this reason, many low-lying Southeast Asian coastal cities are susceptible to relative sea-level rise. Here, we compiled all available tide gauge data within a 10km-radius of the coastal cities in Southeast Asia. The average number of years these tide gauges possess is 34 years, and majority (80%) have less than 50 years of data. Linear sea level trends from tide gauge and satellite data from 1993 to 2018 were shown and discussed for nine selected cities: Malacca, Penang, Singapore, Bangkok, Phuket, Prachuap Khiri Khan, Chumphon, Manila and Cebu City. The mean relative sea-level rise from tide gauge data across these cities was 4.16 ± 2.37 mm/yr (1993 – 2018). The contribution of GRD effects and ocean dynamics from internal variability to the sea level trends had an influence on regional sea level trends and spatial patterns over the last two decades. Vertical land motion due to anthropogenic activity and tectonics was conjectured to be the main driving process in cities such as Phuket and Manila. This study highlighted the non-uniformity of relative sea-level rise on a local scale and the importance of continuous long-term monitoring of sea level and vertical land motion in this region for more robust sea level projections.
OS04-A015
Spatiotemporal Analysis of Extreme Sea Levels Along the Korean Peninsula
Jung-A YANG#+
Korea University, Korea, South
Various countries around the world have been experiencing coastal disasters caused by coastal flooding, and Korean Peninsula is no exception. Most coastal flooding occurs during extreme sea level conditions which is comprised astronomical tides, nontidal residuals, wind wave, and mean sea level. To respond to coastal flooding disasters, it is important to understand the characteristics of extreme sea levels. Therefore, this study analyzed the spatiotemporal patterns of extreme sea levels along the Korean Peninsula and evaluated the effects of the astronomical tides and nontidal residuals represented by storm surges on extreme sea levels among the components constituting extreme sea levels. At this time, when analyzing the impact of the storm surge, it was evaluated whether the storm surge was caused by tropical cyclones or extra-tropical cyclones, and what storm condition were more dangerous in the Korean Peninsula. This study collected observed tidal data from 1979 to 2021 at 48 tide stations which are installed along the coast of the KP and performed a hormonic analysis to distinguish them into astronomical and storm surge components. In this case, storm surges occurring in summer and winter were considered to be caused by tropical cyclones and continental cyclones, respectively. In addition, to more accurately analyze the regional characteristics, the Korea’s coast was divided in the three zones: the East Sea, the West Sea, and the South Sea. As a result of the study, it was found that the extreme sea levels along the Korean Peninsula showed regional differences, and in the case of the south coast, storm surges generated by tropical cyclones were the main drive of extreme sea levels.
OS05-A002
Numerical Sensitivity Experiment on Seasonal Variation of Circulation in Jinhae and Masan Bays
Jiha KIM1#+, Byoung-Ju CHOI2, Ho Kyung HA3
1National Institute of Meteorological Sciences, Korea, South, 2Chonnam National University, Korea, South, 3Inha University, Korea, South
Jinhae and Masan Bays in Korea are semi-closed embayments that are affected by freshwater discharge from the Nakdong River. Although many oceanographic studies have been carried out in bays, research on seasonal and interannual variations of circulation is scarce. In this study, seasonal variation of hydrography and currents are examined using a three-dimensional ocean circulation model. Sensitivity experiments were conducted to investigate the effect of tides, winds and river discharges on regional ocean circulation.
The ocean circulation in Jinhae and Masan Bays was found to be characterized by two distinct patterns. In the western Jinhae Bay, the effects of tides and winds were dominant. Surface and bottom currents flowed toward the south and north, respectively, during the winter months. The tide mixing in winter lowered the density difference between the western Jinhae Bay and Gadeok channel in the southeast. The density difference between the surface and bottom layers was reduced due to wind mixing. The strong wind forcing in the surface layer caused the slope of the sea surface. During the summer, the density difference between the north and south increased, leading to the surface and bottom currents flowing toward the east and west, respectively, by geostrophic balance. Tidal mixing in summer lowered the density difference between the surface and bottom layers while, wind mixing, increased the thickness of the surface mixed layer.
The currents in the central Jinhae Bay and Masan Bay were significantly influenced by the wind in winter, and tides in summer. The river discharge was found to have a relatively large effect on ocean circulation in Masan Bay throughout the year. The currents in the surface and bottom layers of Masan Bay flowed to the open sea and the head of the estuary, respectively.
OS05-A005
Transient Response of Langmuir Turbulence to the Changing Forcings in a Diurnal Cycle
Wentao PAN#+, Qing LI
The Hong Kong University of Science and Technology, China
Langmuir turbulence results from the interaction between ocean surface waves and background turbulence. It is an important physical process in the ocean surface boundary layer that affects the air-sea exchange of heat, momentum and gases. However, its evolution under transient forcing and interaction with changing stratification in a diurnal cycle are not well understood yet. This largely contributes to the existing biases when parameterizing its effects on turbulent mixing in ocean general circulation models and climate models. In this study, Langmuir turbulence with various diurnally varying wind, wave, and surface buoyancy fluxes is investigated using Large Eddy Simulation (LES). By directly resolving the turbulent structures of Langmuir turbulence with high spatial and temporal resolutions, we focus on the transient response of Langmuir turbulence to the changing ocean surface forcing and background conditions during a diurnal cycle. Here we present preliminary results of such LES experiments and discuss the implications for improving existing parameterizations of Langmuir turbulence.
OS05-A007
Latitudinal Shifts of the Intertropical Convergence Zone in the Eastern Equatorial Atlantic During the Last 513 Kyr
Leyla BASHIROVA1,2#+, Liubov KULESHOVA1
1Shirshov Institute of Oceanology of Russian Academy of Sciences, Russian Federation, 2Immanuel Kant Baltic Federal University, Russian Federation
Equatorial Atlantic is characterized by a complex of surface and subsurface currents – some of them flow westward, while others (countercurrents) direct eastward. Most of the year this region is influenced by the Intertropical Convergence Zone (ITCZ), a narrow belt of converging trade winds and strengthening of ascending air fluxes, resulting in an abundant precipitation. The latter leads to a decrease in surface water salinity and increased vertical stratification. Modern seasonal ITCZ migration is well known: over the central Atlantic ITCZ shifts between 6°N in boreal winter and 15°N in boreal summer (relative to the African coast), associated with regional rearrangements of atmospheric and surface ocean circulations due to changes in the meridional gradient of surface temperatures. Here, we present evidence of pronounced glacial-interglacial and millennial-scale variations in ITCZ position and related deep-water upwelling and surface biological productivity. We analyzed stable isotope, geochemical, and micropaleontological records from core ANS-33047 (08°16.38'N, 31°42.87'W, 4027 mbsl, 5.16 mbsf) retrieved from the southern part of the Cape Verde Basin east of the Mid-Atlantic Ridge. The modern annual ITCZ position over the core site allowed estimating the latitudinal displacements of the paleo-ITCZ during the last 513 kyr, based on RN/Gg proxy for mixed layer depth (Portilho-Ramos et al., 2017). This proxy was calculated using the ratio of three key species of planktic foraminifera. A southward displacement of the ITCZ has been suggested during mid-MIS 9, at the beginning of MIS 7, late MIS 5, and within MIS 3–2. Enhanced bioproductivity associated with northward ITCZ migration has been determined during MIS 13/12, early MIS 11,9,7, and MIS 1. Stronger deep-water upwelling and shoaling of the mixed layer over the study site preceded these intervals. The research was funded by the RSF (grant No.22-17-00170).
OS05-A008
High-resolution Sedimentary Record from the Gardar Drift: Surface and Deep-water Variability in the Subpolar North Atlantic During the Last 340 Yr
Liubov KULESHOVA1#+, Leyla BASHIROVA1,2, Evgenia DOROKHOVA3,2, Ekaterina NOVICHKOVA3
1Shirshov Institute of Oceanology of Russian Academy of Sciences, Russian Federation, 2Immanuel Kant Baltic Federal University, Russian Federation, 3Russian Academy of Sciences, Russian Federation
Changes in paleoceanographic conditions on the Gardar Drift are inferred over the last 340 yr from the high-resolution study of planktic (PF) and benthic foraminiferal (BF) assemblages, AMS14C dates, variations in stable isotopes (δ18O, δ13C), sortable silt mean grain size (SS), ice-rafted debris, and total organic carbon (TOC) content in multicore AMK-5687 (59°29.916'N, 24°40.001'W, 2530 mbsl). This time interval corresponds to the latter half of the Little Ice Age (LIA) and the Modern Period (MP). A mean sedimentation rate is ∼0.1 cm/yr. Average sea-surface temperatures (0-50 m) ranging from 8-9.2 °C (winter) to 10-11.5 °C (summer), with minima at ∼1725 AD followed the Maunder solar minimum. The subsequent warming apparently caused the melting of the sea ice in the northern latitudes and, as a consequence, the appearance of a cold freshwater "cap" in the upper ocean layer south of Iceland. A sharp increase in the abundance of the planktic subpolar species Turborotalita quinqueloba and a simultaneous decrease in the subsurface species Globorotalia inflata collectively indicate the Sub-Arctic Front (SAF) position east of the Reykjanes Ridge and the thermocline shoaling at the end of the LIA. North- and westward shift of the SAF as well as warm and salty surface water conditions were proposed for LIA–MP transition by reduced δ18O, an increase in G. inflata, and low abundance of T. quinqueloba. Simultaneously, an enhanced bottom-current intensity occurred according to high values of SS, and an increased carbonate corrosiveness existed leading the PF fragmentation and a significant decrease in δ13C values. A combination of BF diversity indices and TOC content allowed to reconstruct a relatively high surface bioproductivity and an organic carbon flux to the sediments during 1750-1790 and 1940-2010 AD. The study was supported by the RSF (grant No.22-17-00170).
OS05-A009
Estimating the Transport Timescale of Terrestrial Dissolved Substances in the Pearl River Estuary by Using Passive Tracers
Bo HONG#+
South China University of Technology, China
The Pearl River Delta is experiencing environment degradation resulting from the tremendous input of terrestrial dissolved substances (TeDS). The fate and transport timescales of TeDS in the Pearl River Estuary (PRE) was investigated to predict the pollutant transport coming from upstream. By using passive tracers in a calibrated 3D numerical model, the TeDS transport time was computed by using the concept of water age, which is a measure of the time that has elapsed since the tracer was transported from the upstream boundary to the downstream concerned area. The tracer impacted area was defined by the area with tracer concentrations > 0.2 (arbitrary unit). The domains that were impacted by the tracer coming from each outlet group were identified separately. In the wet season, the impacted area was larger than in other seasons. The most prominent variations appeared in the Jiaomen-Hengmen-Hongqili (JHH) and Modaomen (MD) outlets. The hydrodynamic conditions controlled the offshore spreading of the TeDS. Assuming the TeDS were conservative, it took approximately 10-20 days for the TeDS to be transported from the head water to the entrance of the outlet. For the TeDS coming from the head water of the Humen outlet, it took approximately 40 (80) days for the TeDS to be transported out of the mouth of the Lingding Bay during the wet (dry) season. For the MD, Jiti and Yamen–Hutiao outlets, it usually took approximately 10 days for the TeDS to be transported from the head water to the inner shelf. The correlation coefficient between the river flow and tracer concentrations was 0.78, and between the river flow and transport timescale it was −0.70 at a station in the lower Lingding Bay. Other forcing fields (i.e., wind and tide) have stronger impacts at the estuary mouth.
OS05-A013
Inversely Inferring the Diapycnal Diffusivity and Overturning Circulation with Ideal Ventilation Age
Boer ZHANG1#+, Marianna LINZ1, Andrew F. THOMPSON2
1Harvard University, United States, 2California Institute of Technology, United States
The ideal age (or ventilation age) is a commonly used bulk metric of the ocean circulation timescale, and is equivalent to a tracer that is transported by both advective and diffusive ocean motions. In this work, we propose a integrated version of the Munk balance for the ideal age tracer, or a water mass transformation analysis on it, where the sum of the advective and diffusive fluxes across an isopycnal surface equals the volume below it, corrected by an extra air-sea exchange flux if the surface outcrops. The theory is tested in a set of idealized single-basin simulations which mimic the Atlantic basin. With this integrated constraint on total diapycnal age flux, the effective diapycnal diffusivity at an isopycnal level can be inferred from the spatial distribution of the ventilation age near that level and prior knowledge of velocity field. Furthermore, a ratio between the effective diffusivity and the total diapycnal overturning circulation can be inferred by the age distribution, with proper separation of the upwelling and the downwelling region. Our theory provides conceptual clarification on the interpretation of the ideal age distribution, and we find that overturning strength is reflected by the difference of mean age between the upweling and downwelling zones, with the confounding effects of diapycnal diffusion and spatial correlation between age and diapycnal velocity, instead of the absolute value of ideal age itself. Our framework can be applied to realistic clock-like tracers (e.g. radiocarbon, Aragon, oxygen) to constrain the diapycnal diffusivity and overturning strength, which could be a particularly meaningful tool for paleoceanography.
OS05-A014
Multiscale Analysis of Typhoon-induced Oceanic Responses
Gang LI1#+, Yijun HE1, Yang YANG1, Guoqiang LIU2, Xiaojie LU1, William PERRIE2,3
1Nanjing University of Information Science & Technology, China, 2Bedford Institute of Oceanography, Canada, 3Fisheries and Oceans Canada, Canada
A localized multiscale energetics framework is used to study the multiscale interactions between near-inertial and mesoscale processes during the passage of Typhoon Kalmaegi in the South China Sea. The original HYCOM variable fields are decomposed into a low-frequency background flow window, a mid-frequency flow window and a high-frequency process window. Our results show that the background window represents mesoscale processes and Kuroshio currents well and the mid-frequency window captures near-inertial processes influenced by typhoon-induced wind stresses. The kinetic energy transfers from the near-inertial window to the background window, mainly on the right-hand side of the typhoon track. Advection redistributes energy, transporting kinetic energy downward from the ocean surface. Pressure work, which is stronger than advection processes, contributes to the accumulation of kinetic energy in the mid-frequency flow window and enhances ocean mixing. Negative vorticity has a significant impact on the distribution and downward propagation of the near-inertial energy, leading to heterogeneity in the mixing of the upper ocean. Negative vorticity and pressure work partially result in “leftward abnormal enhancement”, the magnitude of which is smaller than the increase in the near-inertial energy. We offer new insights into understanding the multiscale interactions between typhoons and the upper ocean.
OS06-A002
Deep Learning Application for Emulating Atmospheric Forcings in Storm Surge Modeling
Iyan MULIA1#+, Naonori UEDA2, Takemasa MIYOSHI3,4, Takumu IWAMOTO5, Mohammad HEIDARZADEH6
1RIKEN Cluster for Pioneering Research, Japan, 2RIKEN Center for Advanced Intelligence Project, Japan, 3RIKEN Center for Computational Science, Japan, 4University of Maryland, United States, 5Port and Airport Research Institute, Japan, 6University of Bath, United Kingdom
Due to their computational efficiency, parametric models are often used to simulate atmospheric forcings in typhoon-induced storm surge modeling. However, such models need better predictive skills in areas far from the typhoon center, during the extratropical transition, and landfall due to topographic effects. Numerical Weather Prediction (NWP) models are generally more accurate than parametric models, especially when incorporating a proper data assimilation scheme. Nonetheless, their accuracy should be compensated by the high computational cost. In this study, we aim to develop a method that can produce comparable accuracy to the NWP models yet with a minimum computational resource similar to that required for the parametric models. To that end, we propose using deep learning to emulate the atmospheric forcings for our storm surge model efficiently. In this study, a deep learning approach is implemented based on generative adversarial networks (GAN). The input is constructed from the widely adopted parametric model (Holland, 1980) using typhoon best track dataset, and the ground truth or target is based on the DSJRA-55 dataset having a spatial resolution of 5 km at a one-hour time interval. We utilize typhoon data passing through our study area around Japan from 1981-2012, considering 34 events for a training set and four for a test set. Furthermore, we design our GAN model to predict the wind and pressure fields of up to a 12-hour lead time using the current and previous four-hour states. The resulting forcing fields by GAN are then used for the storm surge model using a regional ocean model known as ROMS. The proposed method can achieve comparable storm surge model accuracy to the NWP-based forcings. Moreover, the transformation of parametric model outputs by GAN takes only approximately one second for a typhoon event using a standard computer.
OS06-A011
Analysis of Compound Floods from Storm Surge and Extreme Precipitation in China
Jianlong FENG#+
Tianjin University of Science and Technology, China
The variations and underlying drivers of the compound floods caused by storm surges and heavy precipitation are critical for flooding mitigation and risk reduction in China’s coastal cities. The variability of compound floods from storm surge and extreme precipitation from 1958 to 2014 was analyzed using daily maximum sea level data and daily cumulative precipitation at 16 tide gauges along the coast of China. More than 70% of the storm surges that caused damage from 1989 to 2014 at 14 out of 16 tide gauges were compound floods. We found a strong and seasonally varying dependence between the storm surges and extreme precipitation along the Chinese coast. These were generally positive trends in the annual number of compound events at tide gauges south of 35°N. Compound floods variability was related to large-scale climate modes. The Arctic Oscillation in March was significantly negatively correlated with the compound events at tide gauges north of 35°N, while the opposite was true at tide gauges south of 35°N. The compound events were significantly correlated with the Pacific Decadal Oscillation (PDO) in June at 10 out of 16 tide gauges, and negatively correlated with the Niño1+2 index in February at 7 out of 16 tide gauges. By modifying the East Asian summer monsoon and typhoons, the large climate modes are supposed to impact the occurrence of compound floods. Owing to the large population and low capacity of drainage systems in many cities along the coast of China, our study on the variations and underlying drivers of the compound floods serves as an important reference for flood risk management.
OS06-A020
Effects of Grain Size on the Movement of Submarine Landslides and the Generated Tsunamis
Xiafei GUAN1+, Huabin SHI2#
1University of Macau, China, 2University of Macau, Macau
Submarine landslide is one of the common marine geological hazards with massive sediment transport, large velocity and huge kinetic energy, which threatens seabed pipelines, cables and infrastructure along the propagation path. In addition, generated tsunamis may crush coastal cities with casualties and property losses. The movement of submarine landslides is affected by many physical properties, such as the composition and initial compaction of the slide and the topography. It is reported that the grain size of solid particles has a significant effect through the drag between the solid and the fluid phases. Besides, submerged slides composed of coarse and fine sediment behave differently in the shear dilation/contraction process. Accordingly, the deformation and movement of submarine landslides as well as the tsunami generation are notably affected by the grain size, especially in the initial stage. In this paper, a two-phase SPH model is utilized to study the effects of grain size on the initial acceleration of submarine landslides, a key factor of landslide-induced tsunami generation. The collapsing process of submerged granular landslides on a slope, the generated tsunami, the inter-phase drag force in the slide, and the inter-grain pressure in the cases of different grain sizes are compared. It is shown that the initial acceleration of submarine landslides with fine grains is smaller than that of the coarse-grain ones and consequently leads to a lower tsunami wave. The smaller grain size induces a larger inter-phase drag which hinders the initial movement of granular slides. However, the accelerating duration of submarine landslides with fine sediment is longer, which causes a greater translational velocity and momentum in the balance and deceleration stages.
OS06-A026
A Review of Historical and Paleo-tsunamigenic Earthquakes Along the Littoral Fault Zone in the Northern South China Sea
Linlin LI1#+, Qiang QIU2, Zhigang LI1
1Sun Yat-sen University, China, 2Chinese Academy of Sciences, China
The Littoral Fault Zone (LFZ) was developed along the southeast coast of China in the northern continental shelf in the South China Sea. The 1000 km-long LFZ has high seismic activity, posing a great threat of seismic and tsunami hazard to the southern coast of China. Historically, the fault had generated many moderate to large earthquakes including 18 events with Mw >6 and 4 events with Mw >7 since 1600. Newly obtained geological records indicate strong earthquakes may have occurred in the segment previously assumed less seismogenic. However, little is known about the tsunami hazards associated with earthquakes from the LFZ. Here, we review the historical and paleo-earthquakes which either have documented tsunami phenomenon or have tsunamigenic potential. Based on the available geophysical data and historical documents, we briefly explain the seismogenic behaviors of the LFZ. And taking one of devastating earthquakes: the 1918 Nanao earthquake as an example, we demonstrate the key features of tsunami hydrodynamics and discuss how the earthquake focal mechanisms affect their tsunamigenic capacity. Our results suggest that the tsunami generated by earthquakes along the littoral fault possesses two unique features which may cause substantial damage in future: 1) the long tsunami duration (longer than 48 hours) due to shelf resonance and edge wave trapped in the very broad continental shelf of northern South China Sea; 2) strong tsunami currents induced by rapid change of sea level will pose significant threat to coastal infrastructures, e.g. ports, wharfs and aquaculture farms in southern China. Our sensitivity tests on earthquake parameters suggest that the tsunamigenic capacity is strongly affected by the source mechanism and fault geometries. Detailed marine geophysical surveys are required to better understand the geometrical characteristics and seismogenic behavior of the littoral fault.
OS06-A029
Marine Inundation History During the Last 3000 Years at a Coastal Lake on the Pacific Coast of Central Japan
Yumi SHIMADA1#+, Yuki SAWAI1, Dan MATSUMOTO1, Koichiro TANIGAWA1, Kazumi ITO1, Toru TAMURA1, Yuichi NAMEGAYA1, Masanobu SHISHIKURA1, Shigehiro FUJINO2
1National Institute of Advanced Industrial Science and Technology, Japan, 2University of Tsukuba, Japan
We found geological evidence of marine inundations during the last 3000 years at a coastal lake on the Pacific coast of central Japan. The lacustrine sediments consisted mainly of organic silt, and inundation events were identified from eighteen event deposits (E1–E18, from top to bottom) interbedded with the organic silt. Visual observation by the naked eye identified thirteen sand layers (E1–E3, E5, E8, and E11–E18), one gravel layer (E6), and one volcanic ash layer (E10) as event deposits. The other three event deposits (E4, E7, and E9) were detected only on computed tomography images as layers with higher density than the underlying and overlying organic silt layers. The spatial distribution of the event deposits in seaward areas, diatom assemblages, and frequency of inundation events suggested that thirteen (E1–E8, E11–E15) of the eighteen event deposits were formed by tsunamis or extraordinary storms. To constrain the depositional ages of the event deposits, a Bayesian age-depth model was constructed based on the radiocarbon ages of macrofossils and concentrated pollen grains and the cesium-137 profile. The age model allowed us to correlate five or possibly six event deposits with historical tsunamis along the Nankai Trough: E2, either of E3 or E4, E5, E7, and E8 corresponded to the 1707 CE Hoei, the 1605 CE Keicho, the 1498 CE Meio, the 1096 CE Eicho, and the 684 CE Hakuho tsunamis, respectively. E1 perhaps corresponded to the 1944 CE Showa-Tonankai tsunami.
OS06-A041
Detection and Warning of Sudden High Swells on the East Coast of the Korean Peninsula
Youjung OH1+, Il-Ju MOON1#, Sang Myeong OH2, Pilhun CHANG2
1Jeju National University, Korea, South, 2Korea Meteorological Administration, Korea, South
In recent several years, sudden high swell waves have often occurred on the east coast of the Korean Peninsula, especially in the winter season, which caused many casualties and property damage. These sudden swells have the characteristics of suddenly generating high waves even though the wind does not blow strongly, sweeping away unwary people on breakwaters or causing property damage such as ports and fish farms located on the coast. This study develops a detection and warning system for sudden high swells that frequently occur on the Korean Peninsula's east coast in winter. First, we developed a method to separate the wind and swell components based on the one-dimensional wave spectrum, wind speed, wind direction, and wave direction observed from coastal buoys. Using the calculated swell-wind wave height difference, significant wave height, and wind speed, we developed a sudden swell warning system in three stages (Warning, Watch, and Attention). Analysis reveals that this system successfully detected three recent swell-related accidents on the east coast. Further experiments by applying the system to the prediction results of the wave model showed that the method successfully issued a warning 24 hours before a sudden swell reached the east coast of the Korean peninsula. The developed system can provide quantitative and consistent forecast information, which will significantly contribute to preventing accidents caused by sudden high swells along the east coast of the Korean Peninsula. Acknowledgment: This research was supported by the Korea Meteorological Administration, National Institute of Meteorological Sciences, titled “Development of marine meteorology monitoring and next-generation ocean forecasting system (KMA2018-00420)”, and the National Research Foundation of Korea (NRF) grant funded by the Korea government (Ministry of Science and ICT) (No. RS-2022-00144325)
OS06-A047
Comparison of Coastal Inundation and Deposition Characteristics Accompanied with Tsunamis and Storm Waves Based on Numerical Simulations
Fating LI1+, Linlin LI1#, Kangyou HUANG1, Adam SWITZER2
1Sun Yat-sen University, China, 2Nanyang Technological University, Singapore
The South China Sea (SCS) region, frequently hit by typhoons and tropical cyclones from the northwest Pacific Ocean, is also at risk from multiple tsunami sources, including the Manila subduction zone (MSZ). Reconstructing the frequency and magnitude of past catastrophic wave events in the SCS is still a great challenge due to the difficulties of distinguishing tsunami deposits from storm deposits. Hainan Island in the northern part of SCS features numerous high sand barrier lagoons along the shoreline, which provide suitable environments to preserve overwash deposits, offering the potential for a better interpretation of long-term coastal hazard records. The Xincun Lagoon and Li’an Lagoon in the southeast of Hainan Island, both connected to the open sea through narrow inlets, contain reported sandy deposits. Here, we use numerical simulations to contrast the physical processes of inundation and sediment transportation in the lagoons produced by representative tsunami scenarios and extreme historical storm events at Hainan Island, China. Our preliminary results show that great earthquakes (~Mw9.0) from MSZ could produce large tsunami waves (~7 m) capable of inundating the lagoons and carrying plenty of sediment deposits. This study aims to identify the key source factors affecting the characteristics of tsunami deposits and storm deposits in this specific site. Such site-specific studies are essential for a deeper understanding of the overwash deposition process in the barrier-lagoon system, thus benefiting the subsequent tsunami and storm surge hazards preparation and mitigation in the SCS and worldwide.
OS06-A051
Coastal Tsunami Prediction in Tohoku Region, Japan, Using S-net Observations Based on Artificial Neural Network
Yuchen WANG1#+, Kentaro IMAI1, Keisuke ARIYOSHI1, Takuya MIYASHITA2, Narumi TAKAHASHI1
1Japan Agency for Marine-Earth Science and Technology, Japan, 2Kyoto University, Japan
After the 2011 Tohoku earthquake, Seafloor observation network for earthquakes and tsunamis along the Japan Trench (S-net) was installed offshore Japan. It provides observations for tsunami early warning. Coastal tsunami prediction using offshore tsunami observations contains two main types: tsunami inversion (e.g., tsunami Forecasting based on Inversion for initial sea-Surface Height; Tsushima et al., 2009) and tsunami data assimilation (Maeda et al., 2015). The first type must consider the initial source information, whereas the second type is affected by coseismic deformation. Recently, artificial neural network was introduced to real-time tsunami prediction (Mulia et al., 2020; 2022). We adopted a denoising autoencoder (DAE) model for coastal tsunami prediction. It is a neural network with the encoder-decoder structure trained to denoise or correct corrupted data (Goodfellow et al., 2016). We used 1,000 stochastic earthquake models (M7.0–8.8) in Tohoku region, Japan, and calculated synthetic tsunami waveforms at 50 S-net stations and two coastal stations. The DAE model was trained using 800 synthetic scenarios. Then, we tested the model against 200 unseen synthetic scenarios and two real tsunami events: the 2016 Fukushima earthquake and the 2022 Tonga volcanic eruption. S-net stations had real tsunami records of these two events. DAE model makes accurate prediction of coastal tsunami waveforms for synthetic events. The maximum amplitude was accurately predicted for the 2016 Fukushima tsunami with a forecast accuracy of over 90%. The entire waveforms were also fairly predicted. However, coastal waveforms were not satisfactorily predicted for the 2022 Tonga volcanic tsunami, likely due to its different generating mechanism (i.e., meteorological tsunami). Our research is the first study to apply artificial neutral network to coastal tsunami prediction using real offshore observations. In the future, we will use more tsunami scenarios for model training to make it robust for different types of tsunamis.
OS06-A052
Experiments on the Characteristics of Impact Forces of Bore Waves with Rectangular Drifting Objects
Kensei KUDO#+, Toshinori OGASAWARA
Iwate University, Japan
Tsunamis cause damage directly from wave force and secondary injury from drifting debris. Impact forces exerted by the floating objects on structures are necessary to be correctly evaluated. In this study, we conduct an experiment using a rectangular model to investigate the impact force exerted by drifting objects on a structure and clarify the effect of the impact angle on the impact force. Experimental conditions were set up by satisfying Froude's similarity rule, load cells were placed on the model structure, and impact forces were measured. The experimentally measured impact forces were compared with those obtained by the FEMA equation to verify the validity of the FEMA equation.
The results show that the FEMA equation for impact force is more excessive than the experimental values. As a factor in the overestimation, we focused on the impact angle when drifting objects collide with structures. The collision angles were calculated from the impacting images of drifting objects, and the cases were classified into plane and point impacts. The impact forces for the point are more significant than those for the plane, even when the generated bore waves are under the same conditions. Although the maximum velocities are similar in the drifting process, there is a difference in the decrease in velocities just before the impact. The forces were determined based on the accelerations obtained from the velocity slopes. The force was defined as the damping force. The impact force plus the damping force was considered the total force exerted by the bore wave on the drifting object. The damping force of the plane impact was greater than that of the point impact, indicating that the damping force may strongly influence the difference in impact force.
OS06-A053
Causes of Pressure Instability Problem in Explicit-MPS and Its Improvement Method
Yo OTOBE#+, Toshinori OGASAWARA
Iwate University, Japan
MPS (Moving Particles Simulation) is a typical particle method used for fluid and structural analysis. MPS methods include the semi-implicit algorithm, which solves for pressure implicitly, and the explicit algorithm, which solves for pressure explicitly. Previous studies have proposed methods to suppress pressure oscillations, mainly semi-implicit algorithms. A method to suppress pressure oscillations must also be developed for the explicit algorithm. This paper aims to investigate hydrostatic pressure as an important study for suppressing pressure oscillations and propose a method for suppressing them. One cause of pressure oscillations is that particles inside the fluid are misjudged as free surface particles, causing the pressure value to be calculated as zero even though it exists. Therefore, we examined the distribution characteristics of other particles within the radius of influence on the central particles. The results show that the center of gravity of other particles within the radius of influence of the fluid particle misjudged as a free surface particle is concentrated within 0.005 m of the central particle. Fluid particles were determined conditionally on the distance, and the pressure of misjudged fluid particles was corrected. Furthermore, it was found that there were many particles, even those determined to be fluid particles, that the pressure was more significant than the hydrostatic pressure. The pressure values for these fluid particles were taken as the average of the pressure values for the other particles within the radius of influence as the alternate values. The proposed method significantly reduced the number of misjudged particles and fluid particles with anomalous pressure values. It was possible to obtain pressure distributions that follow the hydrostatic pressure distribution.
OS06-A061
Influence of Urban Buildings on Tsunami Inundation Behavior Using Numerical Simulation
Keisuke HAGA+, Taro ARIKAWA#
Chuo University, Japan
The probability of a Mw.8-9 class Nankai Trough earthquake occurring in Japan within the next few decades is said to be over 80%, and the damage is expected to be enormous. Especially in urban areas, where people and buildings are more concentrated than in plain areas, the tsunami flow and its reach will differ significantly depending on buildings and houses, and the damage is likely to be extensive. Therefore, it is crucial to reproduce the topography of urban areas using numerical simulations to understand the hazards. Although there have been studies on inundation area and depth considering buildings, most of them have focused mainly on inundation depth and arrival time, and there have been few studies on detailed flow velocity and inundation area. In recent years, the improved performance of computers has made it possible to calculate tsunami inundation using high-resolution topography at 10 m or less. Therefore, in this study, numerical tsunami simulations for a Nankai Trough earthquake in an urban area were performed on a 2-meter high-resolution topography, taking buildings into account, and the changes in water level, flow velocity, inundation area, etc., were examined in detail. In addition, the random-phase tsunami model developed by Goda et al. was used to study many tsunami scenarios to cover the uncertainty of the earthquake magnitude. These results will suggest optimal evacuation routes and disaster prevention education for possible future tsunamis in the target area.
OS06-A062
A New O/U-tube to Generate Oscillatory Flows
Cheng-Hsien LEE#+, Jia-You CHEN
National Sun Yat-sen University, Taiwan
This study introduces a new coastal research facility, referred to as an O/U-tube due to its combinations of an O-tube and a U-tube. This new facility has a circulating, enclosed water tunnel and two vertical columns with open tops. The two vertical columns can avoid pressure surges. A valve is installed in the O/U-tube. The O/U-tube becomes a U-tube when the valve closed. Two impeller pumps are used to drive fluid. For steady flows, the force applied by the impellers on fluid is countered by the resistance force. Therefore, there exists a relationship between the rotation speed and flow velocity, which can be used to generate steady flows. For oscillatory flows, the gravity force and the inertia force also have effect on flows. Such relationship cannot be used to generate oscillatory flows. To generate target oscillatory flows, an open-loop control scheme is developed based on a numerical hydrodynamic model and a genetic algorithm. The scheme allows the O/U-tube to generate target oscillatory flows with given velocity skewness and asymmetry.
OS06-A064
A Numerical Simulation Study on the Influence of Flexible Vegetation on Coastal Profile Evolution Under Regular Waves
Yiran WANG#+, Sudong XU
Southeast University, China
Wetland vegetation can effectively resist waves and storm surge disasters, and has the characteristics of lower cost and sustainability, which leads to significant advantages compared with traditional coastal structures. Therefore, flexible vegetation is of important research value on coastal profile evolution. At present, most of the research on the influence mechanism of coastal vegetation has generalized the aquatic vegetation into a rigid cylinder, and little research has directly simulated the erosion and sedimentation effects of flexible vegetation on beach. This paper uses physical model experiments to explore the difference of erosion and sedimentation characteristics between the flexible vegetation beach(FVB) and non-vegetated beach. Then the numerical simulation model: XBeach was well verified by physical model data to simulate and study the erosion and sedimentation characteristics and differences between FVB and rigid vegetation beach(RVB). Physical model tests obtain profiles of non-vegetated beach and FVB under different water depths, wave heights, and periods. Results show that the erosion and sedimentation of FVB are generally smaller than that of non-vegetated beach and present a more near-shore distribution. Numerical simulation results show that the erosion and sedimentation extent of FVB is generally 3% to 14% greater than those of RVB, while the corresponding erosion and sedimentation sites of FVB are generally more offshore than those of RVB. With the increase of wave height, the positions of the first erosion/sedimentation points continue to move offshore. Meanwhile, the range and extent of significant coastal morphological deformation have increased respectively. Periodic tests follow the same results.
OS06-A065
The Research on the Interaction of Coastal Multi-branched Flexible Vegetation with Random Waves in Submerged Environment
Hui XU+, Sudong XU#
Southeast University, China
Storm surges and extreme wave disasters caused by tropical cyclones have caused great economic damage in coastal areas. Therefore, it is of great significance to find reasonable and feasible measures for shore protection to improve the capacity of marine disaster prevention and mitigation and increase the level of coastal ecological environment restoration and management. Compared to traditional coastal protection, nature-based coastal ecological protection has become a hot topic for research on viable solutions to marine hazards due to its ecologically sustainable nature. Coastal wetland flexible vegetation, as a new type of coastal disaster prevention and reduction method, is an significant section in coastal ecological restoration. Flexible vegetation such as reeds and mangroves grow in most of our coastal cities, all of which have a distinctive branching structure. The bending and oscillation of the branches interact with the random waves can reduce the wave energy and thus protect the embankment. However, due to the shading effect of the branching structure and complex dynamic characteristics, a simplified study is carried out here in order to quantify the movement of the flexible vegetation. Most previous work has simplified flexible vegetation to a uniaxial column, ignoring the shading effect of the branching structure of flexible vegetation on the main stem, thereby it is generalised to a uniaxial, multi-branched flexible vegetation model. Based on theoretical analysis and the selection of existing vegetation models, the research intends to carry out physical model experiments to analyze the action mechanism of flexible vegetation on random wave attenuation, and reveal the interaction between the flexible vegetation and random waves under submerged circumstance in a laboratory wave flume. The successful conduct of this experiment can reduce losses and promote the study of coastal ecological revetment for the sake of resisting marine hazards caused by tropical cyclones.
OS07-A001
Existence Periods of Salinity Front as a Feature of Fresh Water Plug During Northwest Monsoon in the Main Pathway of Indonesian Through Flow
Amirotul BAHIYAH1+, Iskhaq ISKANDAR1#, Muhammad Rizki NANDIKA2, Anindya WIRASATRIYA3, Wijaya MARDIANSYAH1
1Sriwijaya University, Indonesia, 2National Research and Innovation Agency, Indonesia, 3Faculty of Fisheries and Marine Science, Indonesia
Freshwater plug is a vigorous phenomenon that widely altered water mass characteristics of Indonesian throughflow (ITF), from Java Sea to Banda Sea. This phenomenon coupled with atmospheric circulation triggered Indo-Pacific climate change. This study investigates salinity front as a feature of freshwater plugs in the main pathway of ITF. However, rainfall on Borneo Island has a significant impact on anomalies’ energetics. Research analyses utilized the remote sensing approach, including atmosphere, ocean, and land analyses. This study's findings are the existence of salinity front and its energetics-long periods that are influenced by ENSO and IOD events. Moreover, a similar study has never been presented previously in Indonesian waters. The study area showed massive salinity front anomalies with the value reaching more than 1 PSU. Its elongated shape closes the main line of ITF and Java Sea pathway. Shorter existence periods (January to May) were discovered in 2015 and 2016 as the result of extreme El Niño 2015-2016 and low positive IOD 2015 events, whereas the anomalies along Jan-May 2019 and 2020 were influenced by moderate El Niño 2018-2019 and extreme positive IOD 2019 events. This condition was followed by a lower total of front less than 1 PSU/100. Longer periods occurred from January to June 2017 and 2018 attributed to moderate negative IOD 2016 and low La Niña 2018. However, more energetic anomalies were illustrated in 2017 than in 2018 due to heavier rainfall anomalies on Borneo Island with a difference of total front value around 0.6 PSU/100. Input sources of river discharge that are revealed from Borneo Island, are eastern (southern) of Borneo. Its drainage actively supplied river runoff during Jan-Jun (Apr-May). It can be concluded that salinity front anomalies are significantly influenced by river discharge from Borneo Island with its energetics determined by Indo-Pacific climate anomalies.
OS07-A003
How Well Do CMIP6 Models Simulate Salinity Barrier Layers in the North Indian Ocean?
Shanshan PANG1,2+, Xidong WANG3#, Jérôme VIALARD1
1Sorbonne University, France, 2Sorbonne University, France, 3Hohai University, China
Previous studies have hypothesized that climatologically thick salinity-stratified Barrier Layers (BL) in the North Indian Ocean (NIO) could influence upper ocean heat budget, sea surface temperature (SST) and monsoon. Here, we investigate the performance of state-of-the-art climate models from the Coupled Model Intercomparison Project phase 6 (CMIP6) in simulating the barrier layer thickness (BLT) in the NIO. CMIP6 models generally reproduce the main features of BLT seasonal cycle and spatial distribution, but with shallow November-February (NDJF) BLT biases in regions with thick observed BLT (eastern equatorial Indian Ocean [EEIO], Bay of Bengal [BoB] and southeastern Arabian Sea [SEAS]). CMIP6 models display an easterly equatorial zonal surface wind bias linked to dry rainfall and cold SST biases in the southern BoB, through the Bjerknes feedback. The easterly equatorial bias is also responsible for shallow isothermal layer depth (ILD) and BLT bias in the EEIO. The underestimated rainfall over the BoB leads to higher sea surface salinity (SSS) and too deep mixed layer depth (MLD), resulting in the BoB BLT bias. The intensity of the easterly equatorial bias also contributes to the inter-model spread in BoB BLT bias, through the propagation of EEIO ILD signals into the coastal waveguide. Finally, the SEAS BLT bias is due to a too-deep MLD, which is predominantly controlled by the high SSS related to attenuated monsoonal currents around India and a reduced inflow of BoB low-salinity water. BLs effect on the mixed layer entrainment cooling does not seem to operate in CMIP6 simulations. Rather, deep salinity-related MLD biases in the BoB result in a diminished cooling rate in response to winter negative surface heat fluxes, and hence alleviate cold BoB SST biases. This suggests that salinity effects alleviate the biases that develop through positive Bjerknes feedback between BoB SST, rainfall, and equatorial wind stresses in CMIP6.
OS07-A007
The Spatial Heterogeneity of Paleoenvironmental Conditions in Baltic Sea During the Late Holocene
Tatiana PUGACHEVA1,2#+, Ekaterina PONOMARENKO2
1Immanuel Kant Baltic Federal University, Russian Federation, 2Russian Academy of Sciences, Russian Federation
The Baltic Sea ecosystem is highly influenced by sporadic salt inflows from the North Sea, which are the main mechanism for water ventilation below the permanent halocline, especially in the central Baltic. Furthermore, the high anthropogenic load and climate variability strongly affect the Baltic Sea environment. The work presents the reconstruction of the paleoenvironmental conditions based on the complex analysis (micropaleontological, grain-size, XRF, and loss-on-ignition) of five short sediment cores retrieved from the Arcona, Bornholm, and Gdansk Basins. The reconstruction of past conditions is crucial for understanding the ecosystem’s natural variability and separating the latter from the reaction to ongoing climatic changes. The results reveal the difference in paleoenvironmental conditions of the studied basins as the response to the heterogeneous impact of the North Sea inflows and climatic fluctuations during the Late Holocene. According to the foraminiferal data, during the whole sediment accumulation period, the salinity of the bottom layer was higher in the Arcona and Bornholm Basins due to the vicinity of the inflow source (Danish Straits).The grain size composition of the cores indicates that the Arcona Basin and the Gdansk-Gotland Sill (Gdansk Basin) were characterized by the most hydrodynamic conditions in the near-bottom layer, which could be partly connected to the shallowness of these areas. Moreover, the Arcona Basin is the most proximal to the inflow source. Among the three basins, the Gdansk Basin was characterized by a higher content of organic matter in the sediments, which could be explained by the river runoff impact due to the proximity to the land, as well as by the repeating hypoxic conditions favoring the organic matter preservation in the sediments. The study was founded by Russian Science Foundation (grant №22-17-00170)
OS07-A009
The Presence of Barrier Layer in the Arctic
Hailong LIU1#+, Hualing WANG2
1Yunnan University, China, 2Shanghai Jiao Tong University, China
Barrier layer (BL) is an important representative variable reflecting salinity stratification. It is defined as the difference between mixed layer depth and isothermal layer depth (Lukas and Lindstrom 1991). Its existence not only weakens the warming effect of entrainment on the upper layer due to a roughly consistent lower temperature within BL than subsurface temperature above warm Atlantic water layer, but also limits the kinetic energy in the upper layer by salinity-induced stratification. Much attention has been paid to the role of halocline in the Arctic in the previous research. By using MOSAiC hydrographic observations and introducing multiple metrics, we focus on the evolution of barrier layer and associated mechanism in this present study. Our results show that BL demonstrates strong seasonal variation and potential role in modulating the interface interaction.
OS08-A005
Three-dimensional Oceanic Eddy Identification in the South China Sea Based on Machine Learning
Guangjun XU1,2#+, Wenhong XIE3, Xiayan LIN4, Yu LIU4, Changming DONG3,2
1Guangdong Ocean University, China, 2Southern Marine Science and Engineering Guangdong Laboratory, China, 3Nanjing University of Information Science & Technology, China, 4Zhejiang Ocean University, China
Oceanic mesoscale eddies play an important role in transports of heat, freshwater, mass in the ocean, therefore understanding three-dimensional structure of oceanic eddies is of significance to climate study and oceanic applications. However, detection of three-dimensional (3D) structures is a big challenge though many algorithms of sea surface 2D eddy detection are developed. In this study, a novel approach by using 3D U-Net residual architecture (3D-U-Res-Net) is proposed to identify 3D structure of oceanic eddies in the South China Sea. The sensitivity tests to input variables are conducted to optimalize the input setting. Trained by 3D eddy data provided by a kinetic eddy detection method, the AI-based method can identify different kinds of eddy vertical structures and moreover can dig out more eddy information in deeper layers. This study has significant implications for the further application of the AI-based algorithm in oceanic study.
OS08-A006
Wave Prediction Based on Improved Empirical Wavelet Transform Decomposition and Long Short-term Memory Network
Jin WANG1,2#+
1Southern Ocean Science and Engineering Guangdong Laboratory (Zhuhai), China, 2Nanjing University of Information Science & Technology, China
Ocean wave is one of the common ocean phenomena. Its formation and propagation are affected by many factors. Ocean waves are nonlinear and non-stationary. In order to improve the accuracy of wave forecast, we propose a wave prediction method base on improved empirical wavelet transform (EWT) decomposition and long short-term memory (LSTM) network. Firstly, as a time series, the significant wave height is used for Fourier transform to obtain the frequency spectrum. Then, according to the wave variation characteristics (yearly, monthly and daily), the segmentation interval of the wave spectrum is determined and divided. According to the divided spectrum, the wavelet filter is used to decompose the signal, so as to obtain the waves of different frequency bands. And then, LSTM method is used to predict the waves of different frequency bands obtained above. Finally, the prediction results of different frequency bands are superimposed to obtain the predicted significant wave height. In this paper, buoy in the North Pacific from National Data Buoy Center(https://www.ndbc.noaa.gov/) is taken as an example for modeling and prediction analysis. The results show that the method has high prediction accuracy. With the increase of forecast windows, the advantage of prediction accuracy is more obvious, which shows the important application values.
OS08-A007
Ocean Data Fusion for High Resolution Surface Current Maps
Evangelos MOSCHOS1,2#+, Hannah BULL2, Alisa KUGUSHEVA3,2, Alexandre STEGNER4
1École Polytechnique, Amphitrite, France, 2AMPHITRITE, France, 3ENS Paris-Saclay, France, 4Laboratoire de Météorologie Dynamique/ National Centre for Scientific Research, France
Ocean circulation is a complex process, making real-time reconstruction of surface currents a particularly challenging inverse problem. Currently, real-time maps of surface currents are produced using inhomogeneous measurements of Sea Surface Height (SSH) and strong spatiotemporal interpolation. However, these maps suffer from significant uncertainties, particularly in regions that are not sampled by altimetric satellites, and local current intensities tend to be underestimated as altimeter observations sample only the geostrophic component of the total velocity. To address these limitations, we propose a novel method that fuses SSH with Sea Surface Temperature (SST) observations to improve the accuracy of ocean circulation maps. In this study, we develop an end-to-end pipeline employing multi-modal input and an encoder-decoder neural network. An Observing System Simulation Experiment generates synthetic SSH and SST data by simulating altimetric along-track measurements as well as infrared sensor cloud coverage. Our data-generating process allows efficient sampling of the learning domain, while a simple data augmentation method is adopted to simulate cloud coverage. The model is thus robust to noisy and missing data due to clouds. Our results on synthetic satellite data demonstrate that this approach leads to improved reconstruction accuracy for both current intensity and direction, compared to the standard reconstruction methods. To validate our results on real data, we use in-situ measurements obtained from drifters. This allows us to compare the real-time nowcast of operational numerical models and our real-time reconstruction method, with improved characterization of ocean circulation at the mesoscale. The results of our experiments demonstrate the effectiveness of a data-driven approach for a real-time reconstruction of high-resolution ocean current maps.
OS08-A013
A Multi-mode Neural Network for the Long-term Ocean Wave Reanalysis
Jiawen LIAO1+, Yineng LI2#, Shiqiu PENG2, Shaotian LI2, Junmin LI2
1学生, China, 2Chinese Academy of Sciences, China
Long-term significant wave height reanalysis is crucial in the application of coastal engineering. The lack of observations and large biases of wind in the coastal region results in significant biases in the numerical model of ocean wave. In this work, we established single-mode and multi-mode correction models based on the Long-short term memory neural network (SCM_LSTM and MCM_LSTM) to revise the results of the numerical model using the in situ observations in 2020. Although the traditional single-mode correction model can efficiently revise low sea state characteristics, it is unsatisfactory in high sea state due to the imbalance of low sea state data and high sea state data. To solve this problem, the MCM_LSTM was built and separately studied the low and high sea state conditions. The correction results for 2021 show that the SCM_LSTM can significantly improve the RMSE and MAE of modeled results with a reduction of 50% and 62.1%, respectively. Compared to the SCM_LSTM, the MCM_LSTM’s RMSE decreases by 5.9%, and its correlation increases by 2.5%. The multi-mode correction model shows great superiority, especially in the case of the high sea state.
OS09-A001
North Pacific Gyre Oscillation and Reorganization During the Holocene with Deglaciation
Xufeng ZHENG1#+, Lixin WU2, Victoria PECK3, Xun GONG4, Hong YAN5, Xu ZHANG6, Martin FRANK7, Frank LAMY8, Li-Wei ZHENG1, Anchun LI5, Zhong CHEN5, Shiming WAN5, Wen YAN5, Yan DU5, Xiao MA9, Lisa BRETSCHNEIDER7, Xiaodong DING10, Lijuan LU5, Shuzhuang WU11, Shuh Ji KAO12
1Hainan University, China, 2Ocean University of China, China, 3British Antarctic Survey, United Kingdom, 4China University of Geosciences, China, 5Chinese Academy of Sciences, China, 6Helmholtz Centre for Polar and Marine Research, Germany, 7GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany, 8Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Germany, 9State Oceanic Administration, China, 10North Minzu University, China, 11University of Lausanne, China, 12Xiamen University, China
The North Pacific Subtropical Gyre (NPSG) vents enormous amounts of heat poleward, modulating the circum-Pacific and global climate1,2. However, orbital and millennial scales oscillations of the NPSG and its interactions with climate systems during current and past warming periods remain undetermined1,3-5, complicating accurate predictions of future ocean circulation and climatic changes. Here, using proxies of current strength and past sea surface temperature gradients, we find that the NPSG was markedly enhanced between 8 and 4 ka. Meanwhile, warming in the northwest and cooling in the northeast is manifested by intensified east-west mid-latitude North Pacific SST gradient, which is in phase with elevated temperature of > 2°C in intermediate waters. The intensified NPSG, potentially caused by strengthened Pacific trade winds, is associated with a climatology sea surface temperature pattern resembling the negative phase of Pacific decadal oscillation, which promotes basin-wide heat uptake in the North Pacific. In addition, the periodicity of NPSG variability shifted remarkably from ~1500 years to ~870 years at ~ 6 ka when the Laurentide ice sheet (LIS) melted away, implying that the presence of the LIS might have suppressed tropical forcing, and thus constitutes a critical tipping point of reorganization of the gyre dynamic over the North Pacific.
OS09-A004
Multi-platform Observation of the Atmosphere and Ocean in the Origin Region of the Kuroshio, East of the Philippines
Akira NAGANO#+, Iwao UEKI, Masaki KATSUMATA, Masahide WAKITA
Japan Agency for Marine-Earth Science and Technology, Japan
Sea surface temperature (SST) variation in the western tropical and subtropical North Pacific is related to atmosphere and ocean variations on various timescales from days to decades such as typhoons, El Niño-Southern Oscillation, and Pacific decadal oscillation. In addition to variations of sea surface forcing, the entrainment of deep water from the subsurface layers is responsible for the SST variation and also the sea surface salinity. Deploying a mooring buoy at 13˚N, 137˚E, named the Philippine Sea mooring observation (PHSMO) site, we initiated the observation in December 2016. As of now, we obtained temperature, salinity, dissolved oxygen concentration, and current velocity data down to a depth of 300 m for longer than 5 years at PHSMO site, and observed their interannual variations at the site. Further, we have conducted field campaigns around the site by the JAMSTEC R/V Mirai. Sea surface and near-surface water became cold and saline just before the occurrent of the 2018/2019 El Niño. Associated with this, the apparent oxygen utilization increased, so that deep old water might be upwelled in the east due to the precedent La Niña and advected to the site. Our observation contributes to monitor the upper-ocean conditions in the western North Pacific tropical and subtropical region and leads to the improvements of predictions of the regional and global climate changes and marine ecosystems, the main goals of the 2nd Cooperative Study of the Kuroshio and the Adjacent Regions (CSK-2) programme registered to the UN Decade of Ocean Science for Sustainable Development.
OS09-A006
A Stability Condition of a Topographically Constrained Geostrophic Current and Its Application to the Large Meander Path of the Kuroshio
Yuki TANAKA#+
Fukui Prefectural University, Japan
A general condition for the stability of a two-layer quasi-geostrophic flow constrained by bottom and coastal topography is derived and applied to the Kuroshio paths south of Japan. First, using a conserved quantity called pseudoenergy that is proportional to the square of the disturbance amplitude, we theoretically derive a sufficient condition for stability for the simplest steady background field in which the potential vorticity and the stream function are proportional to each other. The condition enables us to judge the stability of various background fields by explicitly taking into account the limitation imposed on the scale of the disturbance by the domain size. We then perform an idealized numerical simulation with a realistic situation in mind where the Kuroshio flows over Koshu Seamount and is confined within the Shikoku Basin (a basin bounded by Kyushu Island to the west and the Izu-Ogasawara Ridge to the east). It is shown that a flow similar to the straight path of the Kuroshio becomes unstable while passing over the seamount, developing into a flow similar to the large meander path of the Kuroshio. The application of the above-obtained stability condition shows that the stability of the two flow states can be successfully distinguished, suggesting that the Shikoku Basin stabilizes the large meander path of the Kuroshio while Koshu Seamount fixes the position of the crest and trough of the meander. This result may provide a reasonable explanation for the recently revealed path variability of the Kuroshio south of Japan.
OS09-A007
Change and Variability of Kuroshio Under Global Warming
Jo-Hsu HUANG+, Yu-Heng TSENG#, Yi-Chun KUO
National Taiwan University, Taiwan
Kuroshio plays a critical role on the ocean ecosystem, weather, and even climate in the Western North Pacific through its significant heat transport and air-sea interaction. The future change and dominant mechanism behind it under global warming remain unclear. Some previous studies suggested a negative midlatitude wind stress curl (WSC) tendency, potentially driven by El Niño or Arctic Oscillation, may accelerate the Kuroshio recirculation. The other studies found that the warmer subtropical mode water (STMW) might transport to the east of the Kuroshio along the isopycnals and enhance the upper-layer velocity around Ryukyu island under a warmer climate. Our analysis of the ensemble of 28 CMIP6 low-resolution models in the SSP5-8.5 future scenario shows that the kinetic energy (KE) tendency is positive to the north of 30N and negative to the south. To the south of 30N, the KE of Kuroshio increases in the upper 300m and decreases below 300m (i.e., baroclinic change). Compared with the result above, the ensemble of 5 eddy-permitting models shows that the Kuroshio recirculation north of 30N enhances more dramatically and the Kuroshio extension moves poleward, while the KE in the upper layer decreases in the south of 30N. This suggests the consistent baroclinic increase south of 30N is not evident in the eddy-permitting models. We also find that the meridional transport change negatively correlates well with the WSC change overall. Particularly, the meridional transport change north of 30N is more sensitive to the WSC in eddy-permitting models. Further future scenario ocean model sensitivity experiments suggest that the warmer SST dominates the upper 300m Kuroshio change to the south of 35N, but the WSC affects at depth (below 300m). The warmer isopycnal temperature transport clarifies the STMW pathway, increasing the Kuroshio’s baroclinicity.
OS09-A012
Impact of Kuroshio Meander on Pressure Changes in 2012 to 2013 Along Nankai Trough
Keisuke ARIYOSHI1#+, Akira NAGANO1, Takuya HASEGAWA1, Takeshi IINUMA1, Masaru NAKANO1, Demian SAFFER2, Hiroyuki MATSUMOTO1, Shuichiro YADA1, Eiichiro ARAKI1, Narumi TAKAHASHI1, Takane HORI1, Shuichi KODAIRA1
1Japan Agency for Marine-Earth Science and Technology, Japan, 2University of Texas, Austin, United States
Since DONET station covers above the source region of the 1944 Tonankai earthquake and its shallower extension, it has been also expected to monitor stress accumulation/release process around there from pressure gauges. Recently, it has been well known that slow slip event (SSE), which is one of slow earthquake family (Ide et al., 2007), repeatedly occurs in major subduction zones in shallower extension of the source regions of megathrust earthquakes as well as deeper one (Obara and Kato, 2019). For the shallower extension, SSE has been detected repeatedly from pore pressure extracted from the combination of pressure sensors in a borehole and on the seafloor close to DONET (Araki et al., 2017). For smaller magnitude of SSE about Mw5, its crustal deformation could not be detected from inland observation networks because of amount of displacement for long distance (Ariyoshi et al., 2021). On the other hand, seafloor pressure gauge contains atmospheric and oceanic fluctuations in addition to leveling change due to crustal deformation (e.g., Araki et al., 2017; Ariyoshi et al., 2021). In recent studies, there are several ways to extract the crustal deformation component from pressure gauges on the seafloor and in the boreholes. In this presentation, we reinvestigate the possible SSEs in 2012 and seafloor pressure change in 2013 from the view of crustal deformation on the basis of pore pressure in the borehole and oceanic fluctuation expected from an ocean modeling, JCOPE (Japan Coastal Ocean Predictability Experiment) (Miyazawa et al., 2004).
OS09-A015
Effects of Interannual Variations in the Kuroshio and Oyashio Fronts on Atmospheric Circulation and Storm Track
Xiang LI+, Guidi ZHOU#, Xuhua CHENG
Hohai University, China
Recent findings showed that midlatitude oceanic fronts in the Kuroshio-Oyashio Extension (KOE) region may significantly influence the overlying atmosphere on the interannual timescale. However, the exact mechanism and the combined effects of both the Kuroshio Extension Front (KEF) and the Oyashio Extension Front (OEF) are still largely unknown. Here we use front-resolving ERA5 reanalysis data to investigate the characteristics and mechanisms of the atmospheric response to interannual fluctuations of the KEF and OEF latitudinal position in a consistent way. It is found that the when the fronts meridionally migrate, response of the marine atmospheric boundary layer is remarkable. The response is mostly equivalent barotropic, with upper atmosphere intensification and sign reversal of temperature anomalies. Significant response of the storm track is also found. Diagnosis showed that eddy-mean flow feedback mediated by the storm track is responsible for the large-scale circulation changes, by means of both eddy heat flux and eddy vorticity flux. The spatial pattern of the KEF influence is a zonal dipole and the OEF is a monopole. The northward excursion of the KEF and OEF generally forces atmospheric responses with reverse sign. However, as the KEF and OEF moves in opposite directions with a lag time of 2.5 years, their atmospheric impacts sustains each other.
OS09-A018
Global Warming Effect on Oceanic Mesoscale Eddy Energetics
Junghee YUN1+, Kyung-Ja HA2#, Sun-Seon LEE3
1Yonsei University, Korea, South, 2Pusan National University, Korea, South, 3IBS Center for Climate Physics, Korea, South
Mesoscale eddies are of ubiquity in the ocean and play an essential role in transporting heat, salt, volume, and bio-geochemical properties on a global scale, which could modulate the interplay between the ocean and atmosphere and potentially affect the regional and global climate. However, it remains unclear how climate change will affect ocean eddies due to the lack of observational long-term records and model simulations with high spatiotemporal resolution. Here, we examine changes in ocean eddy activity due to global warming by employing an ultra-high-resolution climate simulation project, fully coupled global climate simulations using Community Earth System Model version 1.2.2 (CESM1.2.2) with different levels of greenhouse gas condition: Present-day run (PD, fixed CO2 concentration of 367 ppm), Doubling CO2 run (2xCO2, 734 ppm), Quadrupling CO2 run (4xCO2, 1468 ppm). We use the eddy kinetic energy (EKE), defined as the time-varying component of ocean kinetic energy, to measure the variability of mesoscale eddies. Model simulations show the inhomogeneous changes of the EKE under global warming conditions. To find the underlying processes, we focus on identifying changes in ocean circulation and stratification and their impacts on eddy energetics.
OS09-A021
Observed Subsurface Lens-like Features East of the Mindanao Island
Linlin ZHANG#+, Weiqi SONG, Dunxin HU
Chinese Academy of Sciences, China
Two subsurface anticyclonic lenses (Lens12 and Lens17) were observed with in-situ measurements along the 8 N transect east of the Philippines during the December 2012 and December 2017 cruises. The isopycnals above the lens center dome upward and those below depress downward. The horizontal scales of Lens12 and Lens17 are approximately 176 km and 210 km, centered at approximately 800 m and 1000 m, respectively, and their vertical extents exceed 1500 m. Mean swirl velocity of Lens17 measured by Lowered Acoustic Doppler Current Profilers is approximately 15 cm/s below 400 m and generally exhibits vertically coherent characteristics. The isopycnal undulations induced by lenses result in substantial temperature anomalies in depth. Temperature anomalies associated with Lens12 reach −3 °C and 1 °C at the depth range of 200–400 and 800–1500 m, respectively. On isopycnals, prominent positive temperature and salinity anomalies associated with Lens12 reach 0.5 °C and 0.1 psu near 26.82, implying that Lens12 carries alien warm and saline water. Combining the water mass properties of Lens12 and the mooring measurements, it is suggested that Lens12 originates from the east and travels westward with a phase speed of approximately 5.2 cm/s. Differing from Lens12, Lens17 shows no evident anomalous water mass properties on isopycnals. Mooring measurements imply that Lens17 probably originates from the south or southeast along the western boundary. By analyzing the outputs from an eddy-resolving ocean general circulation model (OGCM), this study further investigated the statistics of subsurface eddies east of the Philippines, including their geographic characteristics, and eddy-induced transport.
OS10-A014
A Persistent Marine Heatwave in the Northeast Pacific During 2021 Spring and Summer
Haocheng YANG#+
Ocean University of China, China
Marine heatwaves (MHWs)——extreme, prolonged, and dispersed weather events manifested by anomalous warming of seawater, have been found in the near two decades. A persistent marine heatwave has been found in the northeast pacific (NEP) region during the 2021 spring and summer. We used the heat budget to quantitatively analyze the oceanic and atmospheric processes inducing this NEP MHW. During May 2021, a decreasing latent heat loss, which was induced by decreased background westerlies, was the main reason for the onset of this NEP MHW. We can see that the atmospheric process played a crucial role during the occurrence of this MHW. In June, though the temperature tendency was negative, enhancing vertical mixing and entrainment maintained this MHW, while the net surface heat flux gave a negative contribution to the development. This situation was kept until August when the oceanic and atmospheric processes offset each other, causing the slight decay of the NEP MHW event. The atmospheric processes in erecting MHW and oceanic processes in maintaining the developing MHW are significant in spring and summer, which gives us the insight to predict MHW events in the NEP region.
OS10-A019
Role of Local and External Forcing on the Variability of Mixed Layer Depth Over the Bay of Bengal
Biplab SADHUKHAN#+, Arun CHAKRABORTY, Abhishek KUMAR
Indian Institute of Technology Kharagpur, India
To evaluate the climatic scenario of the Indian subcontinent, the study of Mixed Layer Depth (MLD) variability over the Bay of Bengal (BoB) is imperative, as it governs the climatic variability over this region. The BoB is a distinct region, with a large freshwater influx from numerous rivers and monsoon reversal winds in various seasons. The present study examines the role of local and external forcing on the seasonal, interannual, and decadal variability of MLD over the BoB. The analysis spans 36 years between 1980 and 2015 using reanalysis products. The wavelet analysis confirms that the MLD includes prominent interannual and decadal signals throughout the period. The seasonal variation demonstrates that the MLD over the BoB deepens during the summer and winter monsoons and shallows during the pre- and post-monsoons. The interannual variability of MLD is related to the different phases of the Indian Ocean Dipole (IOD), which shows that the positive (negative) phase of IOD is related to the shallower (deeper) MLD over the BoB. The variations in the second downwelling Kelvin and associated Rossby waves over BoB for the opposing phases of the IOD years substantially contribute to this. For a decadal timescale, the MLD over BoB is found to have more significant variance in the western bay and be comparably deep for regime-1 (1980–1998) and shallow for regime-2 (1999–2014). It is found that the decadal variability of BoB MLD is significantly modulated by local forcing like wind, wind-related processes, and Evaporation minus Precipitation (E-P). Moreover, there is a strong correlation between the Interdecadal Pacific Oscillation (IPO), which modulates the MLD of the coastal region of the BoB via propagating coastal Kelvin waves on a decadal timescale.
OS10-A026
Coupling of Alkenones SST and N-alkanes Records in Sediment from the North Atlantic ODP Site 980 During the Past 500 Kyr
Sangmin HYUN1#+, Yeonjee SUH2, Jeongwon KHANG3
1Korea Institute of Ocean Science & Technology, Korea, South, 2Global Oceon Research Center, Korea, South, 3Korea Institute of Ocean Science and Technology, Korea, South
Two typical biomarkers, alkenones and n-alkanes, from the drilling sediment of the ODP Site 980, North Atlantic sector were analyzed to reconstruct linkage and variabilities between SST and paleoclimate variation since the last 500 kyr. The variations of SSTs by alkenones ranged from 7.59 to 22.63oC with distinctive 100ka orbital cycle. Both the warmest and the coldest SSTs were observed during MIS 7, and MIS 8, and corresponding well to the SSTs from the result of previously measured benthic foraminiferal oxygen isotope. This implies that the alkenone SST and their fluctuation well reflected paleoceanographic and paleoclimate variations. The distribution patterns of n-alkanes were characterized by high odd number predominance, particularly nC27, nC29 and nC31, and by the variation of even number n-alkanes distribution. The drastic fluctuations in the abundance of total n-alkane abundance show 100ka cycle and their individual n-alkanes occurred in specific time can be explained by changes in plants habitat of source areas. Therefore, n-alkanes distribution suggests vegetation community changes, and thus paleoclimate changes of source areas. The variations of Average Chain Length (ACL) and Carbon Preferences Index (CPI) were coincident with n-alkanes distribution, reflecting that the vegetation community has been changed in response to global paleoclimate variations with glacial-interglacial time-scale. Strong coincident between alkenones based SST (cycle) and terrestrial total n-alkanes abundance (cycle) imply that the influx of terrestrial organic compound may be associated with paleoclimatology and local paleoceanography in North Atlantic area for the last 500 ka.
OS10-A027
Simulation of Drifting Trajectory of Garbage Discharged Into the Ocean from Rivers in Taiwan
Chung-Ru HO#+, Guan-Yu LIN, Wei-Chih LIN, Yu-Hao TSENG
National Taiwan Ocean University, Taiwan
Marine garbage has become one of the main sources of harm to the ocean. It is well known that a portion of marine garbage is discharged from rivers. In order to understand the drift of Taiwan's garbage after it flows into the ocean from rivers, this study uses the flow field and wind field data from satellite remotely-sensed data, and applies the Oceandrift model in the open source software OpenDrift to simulate the trajectories of garbage discharged from Taiwan's three major rivers on the ocean. These rivers are the Danshui River, the Gaoping River, and the Lanyang River. They are located in northwest, southwest, and northeast Taiwan, respectively. The simulation results show that if the influence of wind drag is not considered, the discharged garbage is mainly affected by ocean currents, especially the Kuroshio flowing through east of Taiwan. If the wind drag effect is considered at the same time, the direction of the Kuroshio and the northeast monsoon is opposite in winter, most of the garbage stays in the waters near Taiwan or even goes down to the Luzon Strait. Garbage with a high wind drag coefficient, it can even be flown to the South China Sea. When the southwest monsoon prevails in summer, under the action of wind drag and the Kuroshio, marine garbage is brought to the ocean around Japan. As for spring and autumn when the monsoon is relatively insignificant, the wind has less impact on marine garbage than ocean currents, so most marine garbage moves mainly with ocean currents, but at a relatively slow speed.
OS10-A030
A CFD Study on Suspended Sediment Transport Analysis at Connection Pier-bridge Between Busan New-Port and Nakdong River Estuary
Sung-Chul JANG#+, Han-sam YOON, Lee SANGHYUB
Pukyong National University, Korea, South
Busan New-Port has undergone large-scale port development, and many projects are currently being implemented or planned, and changes in the marine environment are continuously occurring. In particular, the deposition of suspended sediment causes burial in the harbor, continuously creating an area where the planned water depth is not secured on the front of the quay. These problems hinder the efficiency of port operation by causing unsecured navigation safety of using vessels. In this study, a numerical model simulation is performed to identify the sedimentation characteristics of suspended sediment generated inside the Busan New-Port. For the numerical analysis model, a discrete particle model was applied to the reproduction of suspended sediments, and various simulation cases were set and performed focusing on diffusion according to topographical characteristics.
OS10-A035
Using Shipboard Sonar Data to Identify Subseafloor Intrusive Rock
Pengcheng CHEN+, Shaoping LU#, Chen CAI
Sun Yat-sen University, China
Shipboard sonar is a marine acoustic device that uses a known and repeatable source signature to observe seafloor topography and bathymetry. The advantage of the technology is that it possesses the ability to offer a vertical shallow subseafloor resolution on a decimeter scale. Nowadays, the technology presents potential in exploration to provide direct evidence for identifying subseafloor events relating to sedimentary events, seafloor spreading, mass-transport deposits, and submarine landslides. It is usually used to interpret sedimentary stratigraphy information, but we found that intrusive rock signals could be captured in the sonar data. However, the signals are weak and blurry in comparison with horizons, by which it makes manual picking very difficult. In this research, we propose a novel workflow to identify the intrusive rock signals from the sonar data automatically. This workflow can be divided into three steps. In the first stage, we detect vibration events from the data. After that, the events are clustered based on density-based spatial clustering of applications with noise (DBSCAN) to find areas of increased energy concentration. Finally, the clustered results are combined with the data, the point cloud in the identified area is recovered into one or more lines, and the ones belonging to intrusive signals are determined. The effectiveness of the proposed approach on identifying intrusive signals is verified using survey data from the National Oceanic and Atmospheric Administration (NOAA).
OS10-A037
The South-north Equatorial Asymmetrical Distribution of Chlorophyll in El Niño Events in the Observations and CMIP6 Models
Lixia PAN+, Haigang ZHAN, Xin WANG#
Chinese Academy of Sciences, China
The interannual variability of chlorophyll (Chl) in the tropical Pacific Ocean is influenced by El Niño. When El Niño occurs, insufficient nutrients (suppressed upwelling), reduced shortwave radiation reaching the surface (increased precipitation), and eastward zonal current (U) anomalies, which transport low Chl from western Pacific warm pool water to the east, can cause a reduction in tropical Pacific Chl. The El Niño-induced Chl anomaly is asymmetrically distributed across the equator between 10°S and 10°N, and is particularly significant in extreme El Niño events. This asymmetric phenomenon is mainly caused by asymmetrical anomalies of the eastward U and precipitation. During El Niño events, U and precipitation anomalies are much stronger north of the equator, which can cause a greater reduction in Chl, which is asymmetrical. Models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) are used to evaluate the simulation of the north-south asymmetry of Chl under extreme El Niño events. It finds that the simulation of U and precipitation anomalies is the key parameter to the simulation of this asymmetry. Among 15 CMIP6 models that provided Chl data, only 5 of them (MIROC-ES2 L, MPI-ESM1-2-HR, MPI-ESM1-2-LR, NorESM2-LM, and NorESM2-MM) can be used to investigate the asymmetrical distribution of Chl during extreme El Niño after comparison with observational Chl. Among the 5 selected models, only 2 (NorESM2-LM, NorESM2-MM) can show asymmetry during extreme El Niño events, and the other three models (MIROC-ES2 L, MPI-ESM1- (MIROC-ES2 L, MPI-ESM1-2-HR, MPI-ESM1-2-LR, NorESM2-LM, and NorESM2-MM) 2-HR, MPI-ESM1-2-LR) show symmetrical distributions. From the composite distribution of U and precipitation for these five models, it can be seen that the key reasons for whether a model can simulate the asymmetry lies in the simulation of U and precipitation.
OS10-A040
Geophysical Study on the Relationship Between Offshore and Onshore Faults in the South China Sea
Jun CHEN#+
Tongji University, China
The study on the fractures distribution of offshore and onshore faults and their relationship will help to reveal the history of the continental margin of the South China Sea, the Cenozoic geodynamic process of the western Pacific active continental margin. Through potential field separation and various derivative calculations of gravity and magnetic anomalies, combined with geological and geophysical data, the spatial distribution characteristics of faults in the South China Sea and its surrounding areas were obtained. Our results show that the northwest-trending fault extends from the South China continent to the northern slope of the South China Sea. And some of them even cross the South China Sea and enter Luzon Island. Most of the northeast-trending faults were cut and staggered by northwest-trending faults. The northwest-trending faults in Luzon Island extend into the South China Sea, but most of them become north—north—east or near east—west direction. The northwest-trending fault of the Indo-China block gradually deviates to the south in the process of extending to the southeast. The northeast-trending fault cuts the Yuedong fault and the Wanandong fault individually, but not much extension to the sea area. It shows that the Honghe fault, Yuedong fault and Wanandong fault formed the boundary between the Indo-Chinese block and the South China Sea. The fault systems on both sides are quite different. Most of the northwest-trending faults in Kalimantan region extended into the sea area and cut most of the northeast-trending faults in Nansha.
OS11-A001
Establishing a Risk Assessment Framework for Marine Assets and Assessing Typhoon Lekima Storm Surge for the Laizhou Bay Coastal Area of the Bohai Sea, China
Dongxue MO1#+, Jian LI2
1Institute of Oceanology, Chinese Academy of Sciences, China, 2State Oceanic Administration, China
Effective risk assessment can reduce the economic losses and physical damage caused by marine dynamic processes, such as storm surges. Most risk assessments of marine disasters are based on regional parameters and discrete hazard grades. Targeted, multi-level, and multi-angle risk assessments are urgently needed. This study focuses on specific types of affected infrastructure. We established a sensitivity matrix by considering the effects of different disaster causal factors on different types of affected infrastructure. Through this matrix, hazards, vulnerability, and emergency response and recovery capability were effectively combined in a risk assessment framework. We completed the risk calculation for multiple concurrent effects of disasters in areas with superimposed key infrastructure using complementary risk superposition. The hazard grade, vulnerability grade, and coefficient of emergency response and recovery capability were established based on the means of return period, characteristics of disaster distribution, types of affected infrastructure and disaster relief distance, and were continuous by solving functions, normal cumulative distributions, and analytic functions. On the basis of reasonable MIKE21 numerical simulation and abstract spatial distribution of vulnerable assets, we tested the rationality of the assessment system in the Lekima typhoon storm surge process. The results showed that the assessment system accurately reflected the risk of damage to the important infrastructure in terms of spatial distribution. Therefore, this risk assessment framework was suitable for the assessment of a marine dynamic disaster process in the lower Laizhou Bay coastal area of the Bohai Sea, China. Moreover, it provided a reference for disaster prevention and reduction, guided the way for decision making, and effectively reduced disaster losses.
OS11-A004
Spatiotemporal Variations and Controlling Mechanism of Low Oxygen in a Highly Urbanized Complex River System
Rui-Chen MA+, Jia-Tang HU#
Sun Yat-sen University, China
Numerous aquatic systems are prone to low-oxygen issues due to the anthropogenic impacts. Located in the Pearl River Basin and the upper reaches of the Pearl River Estuary, DongJiang River Network suffered from multiple pollution stressors and experienced prominent low-oxygen events despite effective control on local anthropogenic pollutant loads. A well-validated model was used to reconstruct its spatiotemporal distribution and dynamics processes of DO and to further explore the controlling factors and mechanism of low oxygen. As shown in simulations, DO exhibited significant spatial discrepancies and seasonal variations. The low oxygen was primarily happened in summer and early autumn, and a large-extent low oxygen frequently occurred in the lower region. As the DO budget revealed, photosynthetic production and the microbial oxidation of organic matter were the dominant factors controlling the source and sink terms of DO, respectively. Further scenario experiments indicated that oxygen depletion was dominated by the oxidation of organic carbon from external inputs and in-situ primary production, which contributed 67% and 36% on the low-oxygen volume, respectively. Moreover, phytoplankton played a significant role in DO source-sink processes (e.g., photosynthetic production, autotrophic respiration and heterogeneous respiration), serving as an oxygen source in the upper and middle regions, and as an oxygen sink in the lower region. Collectively, this study revealed the underlying causes of low-oxygen conditions under multi-stressors in a highly urbanized river system and provided a scientific basis for low-oxygen mitigation and management for similar areas.
OS11-A007
Construction of Tsunami Experience System to Improve Evacuation Awareness Using Photogrammetry with VR
Rena NAITO+, Taro ARIKAWA#
Chuo University, Japan
On March 11, 2011, the tsunami following the Tohoku earthquake caused substantial damage. The people who did not evacuate despite the earthquake suffered from normalcy bias. Thus, it is necessary to educate the public to avoid normalcy bias by conducting evacuation drills on a regular basis and other means to prepare for disasters. In recent years, virtual reality (VR) technology has been used to educate the public on how to behave optimally in specific disaster situations, focusing on evacuation and disaster preparedness.
Moreover, to experience a tsunami using VR, information on buildings and roads in the target city is necessary. In Japan, building and topographic data for 3D urban models have been established for urban areas––referred to as Project PLATEAU, which is led by the Ministry of Land, Infrastructure, Transport and Tourism––but not thus far for non-urban areas where tsunami damage is a concern. Therefore, in this paper, we propose creating a VR space that represents a cityscape by using photogrammetry, which creates a 3D model by photographing a subject from various angles. A 3D model was created for town A in Mie Prefecture, and the results and improvements are shown. Further, we propose guidelines regarding the photogrammetry method and how to create 3D models; it is expected that VR spaces can be easily created in any location in the future.
By combining the results of inundation calculations with 3D models, the construction of a VR tsunami experience system will potentially improve evacuation awareness in a more realistic space. This would let the public experience a simulated tsunami experience, leading to early evacuation in the event of a disaster.
OS11-A011
Sedimentary Response to Human Activities in Daya Bay, China
Shuwei ZHANG+, Yunpeng LIN, Jingping XU#
Southern University of Science and Technology, China
Daya Bay, a small embayment in Guangdong province, China, is better known for a nuclear power plant nearby. Sediment from ten surface and five core samples collected in Daya Bay in the summer of 2022 were analyzed for grain-size, loss-on-ignition (LOI), and 210Pb dating, parameters that help investigating the environmental changes due to human activities or otherwise. Surface sediments from stations near the outlet of the power plant cooling water discharge are the largest in mean size and poorest in sorting. Three (D2, D13 and D16) of the five sediment cores can be divided into upper (0-23 cmbsf), middle (23-42 cmbsf) and lower (42-100 cmbsf) sections based on grain-size. The lower section displays a gentle upward fining trend, suggesting a stable sedimentary environment. Sediments in the middle section become much finer, indicating a significant change of sedimentary environment. The upper section has the smallest Mz and much weaker variation, implying a stable environment with weak hydrodynamic force. For D16, the core located in the center of the study area, the Mz clearly decrease upward, from 25.8 μm in the middle and lower to 12.4 μm in the upper section. Meanwhile, the LOI increase from 4.55% to 7.78%, indicating a significant increase of organic matter in the upper part of the core. 210Pb dating of D6 core results in a deposition rate of 0.5 cm·yr-1 in the study area. Thus the one-meter core contains sediment deposit of roughly 200 years assuming constant deposition rate. Applying this time frame to the five sediment cores shows that the 23 cmbsf and 42 cmbsf (two boundaries separating the three sections) correspond to 1980s and 1940s respectively. These to timelines happen to coincide with the intensification of human activities spurred by China’s Reform and Opening Up policy and the construction of the Daya Bay Waterway.
OS13-A003
Applications of Ensemble Coupled Data Assimilation in El Niño–southern Oscillation Prediction
Yanqiu GAO1#+, Youmin TANG2
1Second Institute of Oceanography, Ministry of Natural Resources, China, 2Hohai University, China
El Niño-Southern Oscillation (ENSO) is the most prominent short-term climate oscillation on Earth, which significantly influences the climate and weather anomalies in most regions globally. However, its practical forecast is still highly uncertain. In recent years, much research effort in climate prediction has been devoted to reduce initial and model error issues. In this work, ensemble based data assimilation approaches was employed to the Zebiak-Cane model to form an ensemble coupled assimilation–prediction system. Based on the ensemble system, by assimilating sea surface temperature (SST) and wind stress anomalies, we investigated the impacts of initial condition estimation, parameter estimation, and model tendency error (the comprehensive effect of different sources of errors) estimation on ENSO prediction in sequence. Results showed that, with the initial conditions estimation (i.e. state estimation only), the correlations of predicted Niño3.4 SST anomalies were improved remarkably and the root mean square errors were reduced compared with the values based on the original model. Further results indicated that model parameter estimation achieved better ENSO prediction skills than state estimation only. Model tendency error estimation effectively reduced model error effects in ENSO prediction. Aiming at the filter divergence problem raised by limited ensemble size, we proposed a new covariance inflation scheme to prevent the collapse of ensemble spread. The proposed scheme obtained the best parameter estimation and thereby ENSO prediction skill among the current inflation schemes. Overall, this work provides a promising approach to further improve prediction skill and a useful platform for real-time prediction.
OS13-A005
Research Progress of Ocean Temperature Data Quality Control System
Bin ZHANG#+, Huanping REN
Institute of Oceanology Chinese Academy of Sciences, China
Data quality is the prerequisite condition determining the correctness of the research. However, there’re still a lot of data quality problems existing in the international sharing marine data nowadays. Especially, it is hard to identify the non-conventional “artificial” data error by the traditional methods of quality control. Based on the previous quality controlling about the WOD09 data which is widely used in the world, it is found that among the data of 301740 stations randomly sampled from different geographical areas, data of 4351 stations is failed in error identification in total, accounting for 1.44% error information. The existence of such error information will great possibility affect the research findings. Targeting for such quality problems of international sharing data, we develop the global temperature and salinity data management system to collect and standardize data from diverse sources according to the independently designed ODSF1 data format, which helps optimize the traditional methods for data quality control and repeated data removal. Besides, for the data processed by artificial means (falsification data) and the “simulation” data of the quasi-repeated measurement station, we develop a whole set of “error information identify, analyze, and diagnose technologies”, thereby providing multiple types of data quality control analysis through the way of “expert-machine” combination. The construction of this system has effectively diagnosed and marked a great of data quality problems existing in the international marine data that is now under circulating, and has formed a data set which is more competitive in quality compared with the WOD data; established a set of quality control system for different sea areas, different months, different levels, different temperature and salinity observation parameters within the region from China offshore to Western Pacific, thereby consolidating a sound foundation for scientific researchers using the international sharing data.
OS13-A006
A New Quality Control Scheme for Marine Buoy Temperature and Salinity Data
Huanping REN#+
Institute of Oceanology Chinese Academy of Sciences, China
Based on the errors diversity of marine buoy observational data, this study presents a new quality control (QC) system for marine buoy temperature and salinity data. This QC scheme includes 6 checks with PauTa criterion as its core. The innovation of this scheme is that we present a new quality control algorithm that combines the traditional Spike check and PauTa criterion check. Its robustness has been verified by the seawater temperature and salinity data of buoy in the Yellow Sea and East China Sea. Many spurious measurements or outliers in long time series can be effectively identified. We further suggest this new scheme can be used in the quality control of buoy observation data in the future. Furthermore, we stress that the quality-controlled data could be used for marine scientific research, marine meteorological prediction, marine disaster forecast and fishery development.
OS13-A018
Estimation of Ocean Subsurface Thermal Structure in the South China Sea: An Ensemble-based Machine Learning Approach
Jifeng QI#+, Chuanyu LIU, Bowen XIE, Jianwei CHI
Chinese Academy of Sciences, China
Ocean interior information is vital for a better understanding of Earth's climate and oceans. This study presents a novel ensemble machine learning (Ens-ML) model for reconstructing the ocean subsurface thermal structure (OSTS) in the South China Sea (SCS) utilizing a combination of satellite-derived sea surface data and Argo data. The inputs to the model include sea surface height (SSH), sea surface temperature (SST), sea surface salinity (SSS), sea surface wind (SSW), and geographical information (including longitude and latitude). The performance of three machine learning algorithms (extreme gradient boosting, RandomForest, and light gradient boosting machine) is compared, and the advantages of combining their outputs via an artificial neural network technique are demonstrated. The results suggest that incorporating geographical information into the model significantly improves the accuracy of the OSTS estimate. The Ens-ML model was found to outperform individual models in terms of accuracy and precision. The model's performance varies seasonally, with the best results achieved in winter, likely due to weaker stratification. This study highlights the potential of multi-model ensemble machine learning algorithms for retrieving ocean interior information and provides evidence of their ability to produce more accurate results than individual models. The results of this research contribute to the advancement of oceanography and have implications for future studies on ocean and climate.
OS13-A028
The Mesoscale Eddy Hindcast Experiment for the South China Sea Based on 4DVar Method
Jun ZHAO+, Shan GAO#, Fan WANG
Chinese Academy of Sciences, China
Ocean mesoscale eddy is essentially a large scale motion satisfying quasi geostrophic equilibrium. Theoretically, its motion will be mainly constrained by the quasi geostrophic equilibrium relationship in a short time, while the influence of external forcing field will not change its motion characteristics significantly. Therefore, a prediction scheme of mesoscale eddy was proposed based on the initial field of four-dimensional variational assimilation. To test the feasibility of the scheme, a regional ocean model system (ROMS) and its built-in the primal formulation of incremental strong constraint 4-dimensional variational (I4D-Var) module were used to establish a marine assimilation simulation system for the South China Sea (SCS). First, AVISO altimeter data were assimilated into the ocean numerical simulation by the I4D-Var method, and the ideal mesoscale eddy assimilation simulation results were obtained. The statistical results of assimilation, model simulation, and observation show that the path, radius, sea surface height anomaly and amplitude of the mesoscale eddies simulated by the assimilation system are in good agreement with those observed by AVISO. Meanwhile, the depth analysis shows that the temperature, salinity, and density of eddies could be effectively adjusted. Secondly, the simulation results of the assimilation system were used as the initial field to simulate and quantitatively analyze the mesoscale eddies in the SCS in a certain period. By comparing the SSHA (sea surface height anomaly) correlation coefficient, eddy center distance, and radius absolute error of the corresponding eddies in the post prediction simulation and observation data, the post prediction time of mesoscale eddies in this scheme reached at least 10 days. The results of the post prediction experiments verified the feasibility of the proposed scheme, which provides a theoretical basis and a feasible scheme for the prediction of mesoscale eddies.
OS13-A042
Products of HY-1C/D Ocean Color Satellites
Jianqiang LIU, Xiaomin YE#+, Qingjun SONG, Bin ZOU
National Satellite Ocean Application Service, China
The HY-1C and HY-1D satellites are the first operational ocean color constellation in China. HY-1C and HY-1D was launched in September 7, 2018 and Jun 11, 2020, respectively. Chinese Ocean Color and Temperature Scanner (COCTS), Coastal Zone Imager (CZI), Ultra-Violet Imager(UVI), Satellite-based Calibration Spectrometer (SCS) and Automatic Identification System (AIS) are the key payloads onboard HY-1C and HY-1D. The HY-1C/D constellation has been detecting the global ocean color twice and sea surface temperature (SST) four times every day, and high- resolution (50m) China’s coastal zone and offshore environments twice every three days.In this study, the HY-1C/D satellites and the specifications of the payloads, flow-process, product levels and distribution of data products are introduced. The HY-1C/D satellites complete processing chains for generating raw data, radiances, ocean color and sea surface temperature (SST) from the payloads by Geo-location, radiometric and atmospheric correction, geophysical parameters retrieval, data gridding and merging. There are different data products associated with the five levels of processing (Level 0 to Level 4). Data products of Level-1 (radiances), 2 (ocean color parameters and SST), 3 (gridded products) and 4 (merged gridded products) are available from the China Ocean Satellite Data Service Center to the general public for free. The HY-1C/D satellites product structure system is complete and data product processing and distribution are efficient. The typical products of Chlorophyll-a concentration and SST, the applications on floating green tides algae Ulva prolifera, sea ice and polar ice, offshore aquaculture, inland water and tropical cyclones are also presented in this study. The typical products and application shown in this study indicates that the sensors and the data products of HY-1C/D have high quality and great application potential in marine and coastal environmental monitoring.
OS13-A043
A Sea Surface Temperature Retrieval Method of China Ocean Color and Temperature Scanner (COCTS)
Bin ZOU, Xiaomin YE#+, Qimao WANG, Qingjun SONG
National Satellite Ocean Application Service, China
The Chinese Haiyang-1C (HY-1C) and Haiyang-1D (HY-1D) satellites were launched in September 2018 and June 2020, respectively. These satellites are both equipped with the COCTS, a moderate-resolution imaging scanner with a nadir spatial resolution of 1.1 km and a viewing swath width of more than 2900 km. The satellite measures signals in 8 visible and near-infrared (VNIR) bands and 2 thermal infrared (TIR) bands (10.3~11.3μm,11.5~12.5μm). By using the non-linear algorithm for SST (NLSST) of split window, we retrieve SST from the two thermal infrared spectrum channels of 11 and 12 µm of COCTS. The Multiple Channel Sea Surface Temperature (MCSST) is used to be as the first guess of NLSST equation. The coefficients of both NLSST and MCSST are regression to ocean buoys and ship measurements. The retrieval SSTs from Jan. 1, 2019 to Mar. 31, 2020 were evaluated by the in situ measurements from iQuam with root mean square errors (RMSEs) of 0.84 °C for daytime and 0.97 °C for nighttime and robust standard deviations (RSDs) of 0.73 °C for daytime and 0.72 °C for nighttime, respectively. RMSEs of 0.65 °C and 0.71 °C and RSDs of 0.51 °C and 0.47 °C were obtained for the daytime and nighttime SSTs of the COCTS/HY-1D recorded from April 26 to August 31, 2021, using a spatiotemporal matching window of 4 hours and 2.5 km. Daily gridded retrieval SSTs from COCTS on both HY-1C and HY-1D were compared with SSTs from the moderate-resolution imaging spectroradiometer (MODIS) on Terra satellite and the visible infrared imaging radiometer (VIIRS) on the Suomi National Polar-orbiting Partnership (S-NPP) satellite. Both daytime and nighttime SSTs from COCTS are consistent with those from MODIS and VIIRS.
OS13-A045
Exploring Deep Ocean Bottom Using OBS and Impacts of Mass Blocks
Tianzhu LUO+, Qingyu YOU#, Lei ZHANG, Jinhai ZHANG
Chinese Academy of Sciences, China
Hadal trench—the deepest region of ocean, lying within oceanic trenches, is a promising place to uncover geological and geophysical mysteries of the deep ocean. China’s deep-sea submersible mother ship, Tansuo-1, deployed an ocean bottom seismometer (OBS) at the Hadal trench. This OBS recorded three events triggered by mass blocks (~400 kg for each), which can be regarded as vertical force sources. Here, we first utilized the grid search method to find the best-matching azimuth angle corresponding to the minimum energy ratio between the tangential and radial components. Then, we performed time-frequency analysis to present the time-frequency response of porous ocean bottom. Finally, we obtained the seismic wave velocities derived from body waves and surface waves. This research provides the first active detection using OBS and impacts from mass blocks with horizontal distance of <300 meters at the deep ocean bottom, which is helpful for future works on the investigation of seabed structure in hadal trench zones.
OS13-A047
Parameter Optimization and Observing System Evaluation Based on Data Assimilation to Improve Water Quality Monitoring and Prediction
Zhouxiao LIU+, Liuqian YU#
The Hong Kong University of Science and Technology (Guangzhou), China
Coastal waters have been increasingly degraded worldwide due to human disturbance and climate change. Quantitative knowledge of the status, underlying drivers, and future trend of coastal degradation is of paramount importance to designing scientifically-sound management strategies. Ocean biogeochemical models are a vital tool to serve the purpose, but their performance and predictive capability are often limited by the inaccurate description of ecosystem processes, uncertain parameters, and inadequate observations for validation and calibration, among others. This work aims to conduct parameter optimization to improve an ocean biogeochemical model and evaluate the observing system design through data assimilation, with the goal of informing water quality management. We will take Deep Bay, a shallow eutrophic system under intensified human perturbation in southern China, as a case study. The Bay has five long-time series stations monitoring water quality monthly since the 1990s. It also exists a 3D coupled physical-biogeochemical model that has been developed for a larger spatial scale beyond the Bay and thus has not been vigorously calibrated for the Bay area. Considering the computation costs for directly optimizing parameters and performing a large number of sensitivity tests in the 3D model, we alternatively build a 1D surrogate model that consists of multiple horizontal well-mixed boxes and is tuned to represent major biophysical features of Deep Bay. In the twin experiment framework, we evaluate the performance of parameter optimization by assimilating data from the existed monitoring system versus alternative observational sampling schemes. Through these analyses, we gain insight into where, how frequently, and what variables we should observe to maximize the benefit of data assimilation to improve model prediction and inform water quality management. We also explore to what extent the optimized parameter set from the 1D model can improve the 3D counterpart for providing spatially-explicit estimation and prediction.
OS13-A048
Observed Taylor Cap Around a Seamount Intensified by a Surface Mesoscale Eddy in the Northwest Pacific
Yansong LIU#+
Chinese Academy of Sciences, China
Observations from 4 current and pressure-recording inverted echo sounders (CPIESs) deployed in the northwest Pacific from 2018 to 2019 reveal an anticyclonic cap around a seamount. Significant increases in velocity can be found from mid-November 2018 to January 2019 and verified the coexistence with the “cold dome” combined with numerical model data. The Taylor cap induced by the impinging flow toward the seamount plays a primary role in the anticyclonic current structure
compared with tide rectification. The relationship between the impinging flow and surface mesoscale eddy in the northwest Pacific was further analyzed by combining the satellite altimeter data. When the surface cyclonic eddy moved to the center of the seamount in November 2018, the absolute sea level anomaly (SLA) increased, the temperature at the summit decreased, and the deep velocity impinging toward the seamount decreased and then intensified the Taylor cap around the seamount.
OS13-A052
Deviations of Satellite-measured Sea Surface Salinity Caused by Environmental Factors and Their Regional Dependence
Yating OUYANG1+, Yuhong ZHANG1#, Jianwei CHI1, Qiwei SUN2, Yan DU1
1Chinese Academy of Sciences, China, 2Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), China
Satellite measurements have largely improved sea surface salinity (SSS) observations in the recent decade, including Soil Moisture Ocean Salinity (SMOS), Aquarius/Satélite de Aplicaciones Científicas (SAC) –D, and Soil Moisture Active-Passive (SMAP). This study evaluates the deviations between the satellite SSS products and the in-situ observations (ΔS) and analyses their relationships with the environmental factors, including sea surface temperature (SST), precipitation, and wind speed. The level 3 satellite SSS generally correlates well with Argoobserved SSS but differs in the middle and high latitudes and the tropical convergence zones. The smallest ΔS appears in the subtropical open oceans, where the sea surface features warm SST, rare precipitation, and low wind speed. The variations in mean |ΔS| for the three satellites show a robust dependence on SST, precipitation, and wind, with large ΔS (outside 5%–95% interval) in particular tending to occur in areas of cold SST, heavy rainfall, and high wind speeds. The most pronounced SSS deviations occur in the middle and high latitudes (beyond 40°) due to cold SST. In particular, heavy rainfall in the subpolar regions and strong westerly winds in the mid-latitudes also make the satellite SSS measurements less accurate. In the tropical convergence zones, large SSS deviations are mainly related to heavy rainfall, showing significant surface freshening. The fresh biases related to rainfall are more significant in Level 2 SSS than in Level 3, due to the short period of the convective rainfall. In addition, surface freshening is more obvious in low wind speed scenarios, showing that the fresh skin layer induced by rain is more common on the calm ocean surface.
OS13-A053
Ocean Surface Wind Speed Inversion from the First Order Echo of HF Surface Wave Radar
Xiaoyan LI+, Xiongbin WU#, Liang YU, Fuqi MO
Wuhan University, China
The traditional methods of retrieving sea surface wind speed by high frequency(HF) surface wave radar are mainly based on the second order echo. However, due to the low signal-to-noise ratio and complex nonlinear effect of the second order echo, the detection range and accuracy of wind speed retrieved from radar are limited. Recently, some wind speed inversion approaches have been proposed based on the first order echo. But most of them utilize only a single operating frequency or a single radar station, thus the range of wind speed estimation from radar is usually limited for using restricted information of frequency and viewing angle. To address this issue, a wind speed inversion method based on the first order echo for a dual-frequency dual-station HF surface wave radar system is proposed. For each radar frequency, the spreading factor parameter which represents the growth state of wind waves, can be extracted from the ratios of positive and negative Bragg peaks of the two radar stations by using a cosine model as the angular distribution function. It has been inferred from in suit data that there is an ambiguity between the spreading factor of a fixed frequency and the wind speed. The problem is solved by using spreading factors of two frequencies retrieved from radar. The proposed wind speed inversion method is applied to an HF surface wave radar system operating at 7.94MHz and 12.365MHz and installed along the coast of the Taiwan Strait. In addition, a comparison between radar-derived, buoy-measured and ERA5 wind speed at the location 100km away from both radar stations is given to validate the proposed method.
OS13-A054
Spatiotemporal Variation of the Departure in Simulation from HF Radar Doppler Spectra Measurements
Fuqi MO+, Xiongbin WU#, Liang YU, Xiaoyan LI
Wuhan University, China
Directional ocean wave spectrum extraction from HF radar Doppler spectra has been a challenge with the limitations of second-order theories in high sea states. Whereas, the inversion of wind speed and direction for HF radar has been widely used to get relatively accurate results. These wind field information could be utilized to simulate corresponding radar backscatter spectrum with empirical ocean wave spectrum model by the first and second order theory. But, the departure of these simulated spectrum from radar Doppler spectra measurements is universal phenomenon during our field experiment in the Taiwan Strait with a complex topography. Due to the influence of wind field and geomorphic factors, the practical ocean wave spectrum is unable to described by existing empirical model. Although, the analysis of spatiotemporal variations in those departure could provide more details about the features of practical ocean wave spectra and then the interconnection between them. The field experiment carried out in Fujian Province collected a few months of data with dual radar system. Also, buoy and ERA5 data is prepared for verification. The comparison shows this analysis of the departure contributes to measure ocean dynamic parameters.
OS14-A006
Holocene Sea-level Evolution in Western Australia
Nicole KHAN1#+, Kayla MURAI1, Michael O'LEARY2, Erica ASHE3, Tanghua LI4, Abang SURYA4, Rahul KUMAR4, Adam SWITZER4
1The University of Hong Kong, Hong Kong SAR, 2The University of Western Australia, Australia, 3Rutgers University, United States, 4Nanyang Technological University, Singapore
Records of Holocene relative sea-level (RSL) change from Western Australia, a far-field location distal to former polar ice sheets, offer important constraints on ice melt contributions to global mean sea-level (GMSL) change. Despite this, efforts to reconstruct RSL have been limited, and the nature of Holocene RSL evolution in Western Australia remains debated in part due to biased comparisons of data. Here we 1) review, re-evaluate, and aggregate RSL data from Western Australia following international standard protocol and 2) explore the potential of sedimentary archives from beach ridge systems from southwest Western Australia to produce accurate, high-resolution records of Holocene RSL change. We use these data to test several working hypotheses about ice sheet contributions to GMSL change during the Holocene and the influence of local (e.g., non-stationary tides) or higher-frequency (e.g., El Niño Southern Oscillation) drivers of sea-level variability. Improved constraints on the behaviour of RSL during the Holocene will also provide new data for enhancing our understanding of earth rheology, ice sheet dynamics, and natural variability of sea-level changes under warm, interglacial climate states.
OS14-A009
The Utility of Vertical Zonation of Intertidal Microfossils and Stable Carbon Isotope and C/N Geochemistry for Sea-level Reconstruction in the Pearl River Delta
Howard Kwok Yin YU#+, Nicole KHAN
The University of Hong Kong, Hong Kong SAR
Determining the rates and mechanisms of relative sea level (RSL) change in the past can help enhance local projections of future RSL change, which is especially important in populated regions such as the Pearl River Delta (PRD), China. However, the late Holocene RSL history in this region is incomplete, and most of the data from existing reconstructions consist of limiting points that lack detailed bio- and chemo-stratigraphic analysis, which introduces uncertainty into the RSL record. Microfossils (foraminifera and diatoms) are used as RSL indicators because their community assemblages change across the elevation and environmental gradient in the intertidal zone. Moreover, stable carbon isotopes (δ13C) and the ratio of total organic carbon to total nitrogen (C/N) are able to identify the sources of organic matter that deposit in coastal sediments. To reduce potential bias in RSL reconstructions, a full understanding on the factors that control local modern microfossils distribution and δ13C and C/N geochemistry are required. Here, we investigate the utility of microfossils to generate a high-resolution (decadal to centennial age and ± 0.1 m vertical) late Holocene RSL reconstruction from sediments in Deep Bay, PRD. We describe the contemporary distribution of foraminifera, diatoms, and δ13C and C/N geochemistry from three transects that cover subtidal, intertidal (mudflat and mangrove) to upland environments. We examine the effect of elevation, total organic carbon content, and porewater salinity on the vertical distribution of microfossil groups using principal component analysis (PCA) and partitioning around medoids analysis (PAM). We develop a weighted averaging partial least squares regression (WA-PLS) transfer function from foraminifera and diatom assemblages and apply it to a core collected from mangrove in Mai Po, Deep Bay. Our approach could generate new late Holocene RSL records and improve our understanding of the rates and mechanisms of RSL change in the region.
OS14-A012
Foundations for Analysis and Machine Learning of Coral Microatoll Surface Features
Rohan GAUTAM#+, Aron MELTZNER, Khai Ken LEOH, Nurul Syafiqah TAN
Nanyang Technological University, Singapore
Coral microatolls are coral colonies found in shallow reef environments. Their unique surface morphology of concentric rings is a result of relative sea-level (RSL) change and other environmental conditions that can affect the coral's growth over time. Invasive techniques involve physically extracting a slab of the coral microatoll to study the coral's annual growth bands to precisely determine RSL as the coral grew. However, such invasive techniques may not be viable at every site. Non-invasive techniques and methods of analysis are essential for large scale, cost-effective, and sustainable studies of coral microatolls. Examples of this technique include digital reconstructions of coral microatolls obtained via photogrammetry and LiDAR techniques. These digital models are further analyzed for tasks such as estimating growth variability across corals, detecting overgrowth and ring structures on the coral surface, and direct comparison of two coral surfaces. Conventional techniques for carrying out such analyses involve human intuition in key steps and are subject to significant human errors and biases. In our study, we work with digital reconstructions of corals to develop key foundations for analyzing and comparing different regions of the coral surface. We define a mathematical and computational notion of similarity between surface patches of varied sizes. We then develop the necessary data preprocessing pipelines and machine learning algorithms that use the initial formulation of the notion of similarity and apply it to analysis tasks. In doing so, we aim to support and formalize human intuition traditionally used for these tasks and significantly reduce human-induced errors, along with enabling more rigorous and larger-scale analysis of coral microatoll surfaces.
OS14-A013
Using Non-invasive Techniques to Estimate Growth Variabilities of Living Coral Microatolls on St. John’s Island, Singapore
Khai Ken LEOH#, Nurul Syafiqah TAN, Lucas KOH, Junki KOMORI, Rohan GAUTAM, Aron MELTZNER+
Nanyang Technological University, Singapore
Multi-decadal sea-level histories are crucial for quantifying processes that drive relative sea-level (RSL) change and for forecasting future RSL rise. However, tide gauge records maybe short, discontinuous or have poor spatial coverage. To overcome this, coral microatolls can be used to reconstruct RSL over decadal to centennial scales. Microatolls are coral colonies that grow in the intertidal zone, whose upward growth is limited by low-water levels. The exposed portions die, forming characteristic concentric rings that track RSL over the coral’s lifetime. The established method for reconstructing RSL from a microatoll involves extracting a radial slab, a cross section revealing the coral’s growth history. This may not always be viable, therefore inferences of the coral’s growth history are determined from its surface morphology. This is complicated by variable coral growth rates that form different surface morphologies on coeval microatolls. Overgrowth, out-of-sequence growth on the inner rings of a microatoll, is highly sensitive to growth rates. Both the growth rate and overgrowth must be considered for RSL reconstructions. In this study, we explore three-dimensional (3D) photogrammetry as a non-invasive technique to study the surface morphology of coral microatolls. Focusing on five living coral microatolls on St John’s Island, Singapore, we created digital elevation models (DEMs) using structure-from-motion (SfM) photogrammetry. We differentiated overgrowth regions and quantified the relative intra- and inter-coral growth variabilities based on distinctive features from multiple radial surface profiles. Next, we combined these results with literature values to estimate the true growth rates of each coral. In this session, we present two complementary techniques for RSL and coral microatoll research. Komori et al. introduces a simulator to model coral growth in response to RSL change. Gautam et al. uses an algorithm to quantify similarities in gradient changes across fixed coral transect lengths.
OS16-A008
Global Oceanic Diazotroph Database Version 2 and Elevated Estimate of Global Oceanic N2 Fixation
Yangchun XU+, Ya-Wei LUO#
Xiamen University, China
N2 fixation by marine diazotrophs is an important bioavailable N source to the global ocean. In 2012, the first version of the global oceanic diazotroph database (version 1) was published. Here, we present an updated version of the database (version 2), significantly increasing the number of in situ diazotrophic measurements from 13,565 to 55, 286. Data points for N2 fixation rates, diazotrophic cell abundance, and nifH gene copy abundance have increased by 184%, 86%, and 809%, respectively. Version 2 includes two new datasheets for the nifH gene copy abundance of non-cyanobacterial diazotrophs and cell-specific N2 fixation rates. Consequently, when estimating global oceanic N2 fixation rates using the geometric means of different ocean basins, version 1 and version 2 yield similar rates (43–57 versus 45–63 Tg N yr-1). In contrast, when using arithmetic means, version 2 suggests a significantly higher rate of 223±30 Tg N yr-1compared to version 1 (74±7 Tg N yr-1). Specifically, substantial rate increases are estimated for the South Pacific Ocean (88±23 versus 20±2 Tg N yr-1), and the North Atlantic Ocean (40±9 versus 10±2 Tg N yr-1). Moreover, version 2 estimates the N2 fixation rate in the Indian Ocean to be 35±14 Tg N yr-1, which could not be estimated using version 1 due to limited data availability. Furthermore, a comparison of N2 fixation rates obtained through different measurement methods at the same months, locations, and depths reveals that the conventional 15N2 bubble method yields lower rates in 69% cases compared to the new 15N2 dissolution method. This updated version of the database can facilitate future studies in marine ecology and biogeochemistry.
OS16-A009
N2 Fixation in Trichodesmium Does Not Require Spatial Segregation from Photosynthesis
Weicheng LUO1+, Keisuke INOMURA2, Han ZHANG3, Ya-Wei LUO1#
1Xiamen University, China, 2University of Rhode Island, United States, 3Shandong University, China
The dominant marine filamentous N2 fixer, Trichodesmium, conducts photosynthesis and N2 fixation during the daytime. Because N2 fixation is sensitive to O2, some previous studies suggested that spatial segregation of N2 fixation and photosynthesis is essential in Trichodesmium. However, this hypothesis conflicts with some observations where all the cells contain both photosystems and the N2-fixing enzyme nitrogenase. Here, we construct a systematic model simulating Trichodesmium metabolism, showing that the hypothetical spatial segregation is probably useless in increasing the Trichodesmium growth and N2 fixation, unless substances can efficiently transfer among cells with low loss to the environment. The model suggests that Trichodesmium accumulates fixed carbon in the morning and uses that in respiratory protection to reduce intracellular O2 during the mid-daytime, when photosynthesis is downregulated, allowing the occurrence of N2 fixation. Cell membrane barrier against O2 and alternative non-O2 evolving electron transfer also contribute to maintaining low intracellular O2. Our study provides a mechanism enabling N2 fixation despite the presence of photosynthesis across Trichodesmium.
OS16-A013
Impacts of River-discharged Freshwater on Surface Ocean Environments Revealed by Satellite Measurements
So-Young KANG1+, Jae-Hong MOON1#, Taekyun KIM1, Chanhyung JEON2
1Jeju National University, Korea, South, 2Pusan National University, Korea, South
A Large amount of freshwater discharged from the Changjiang River supplies high concentrations of nutrient and organic matter into the East China Sea (ECS). The river-discharged freshwater plays an important role in physical and biochemical responses of ocean environment, which are also closely related to regional carbon cycle. In this study, we used satellite-derived datasets for sea surface temperature (SST), chlorophyll a(Chl-a), and sea surface salinity (SSS) to investigate the impacts of freshwater on surface ocean environments in the northern ECS over 2015–2022. The corrected SSS shows a distinct interannual variation, with a strong seasonal cycle in winter maximum and in summer minimum. By comparing with SST and chl-a anomalies, we found that the river-induced low-salinity water is closely linked to SST warming and high levels of chl-a concentration relative to their long-term means. In addition, relatively low partial pressure of carbon dioxide (pCO2) estimated appears in the northern ECS in 2016, which corresponds to the regions where in the SST warming and high levels of chl-a concentration are significant. These results suggest that warm and nutrient-rich freshwater at the surface may contribute to a reduction of surface pCO2 by prompting biological uptake of CO2.
OS16-A014
The Role of Mixotrophs in Lower Trophic Levels of Marine Food Webs
Mengting QIAN+, Ya-Wei LUO#
Xiamen University, China
Mixotrophy, the combination of autotrophy and heterotrophy in the same organism, is widespread among protist plankton. Mixotrophs range in size from pico- to megaplankton and vary in type. For a long time, most aquatic scientists thought that mixotrophs were not universal or of little significance, but as more mixotrophs were discovered, realizing their importance for energy budgets and elemental cycling in planktonic ecosystems was largely ignored. Mixotrophy alters the basic trophic structure of marine planktonic ecosystems, and most unicellular organisms in lower trophic level of plankton food web can no longer be considered strictly producers or consumers. Mixotrophy has a profound impact on marine planktonic ecosystems and may enhance primary production, biomass transfer to higher trophic levels, and the functioning of the biological carbon pump. But now the representation of mixotroph community is highly simplified, and further explicit inclusion of mixotrophs into biogeochemical models is necessary to improve our understanding of marine food webs and the global carbon cycle. So we built a plankton food web model incorporating mixotrophic functional diversity. We distinguish the size and type of mixotrophs, simulating how mixotrophs regulate plankton dynamics, primary production and carbon biomass transfer under different marine environmental conditions. Our study suggests that mixotrophic functional diversity can significantly alter our understanding of ecosystem dynamics within the lower trophic levels of marine food webs.
OS16-A016
Negative Surface Chlorophyll Concentration Anomalies in the Southeastern Arabian Sea During 2015 and 2019 Summers
Huaming HUANG#+
Sun Yat-sen University, China
Two extremely low surface chlorophyll concentration events in the southeast Arabian Sea (SEAS, 6oN-15oN, 72oE-77oE) during summers of 2015 and 2019 have been found since 1998. Although warm sea surface temperature (SST) and low nutrients are the direct cause for the anomalously low surface chlorophyll concentration, the physical processes leading to the warm SST anomalies during 2015 and 2019 summer are different. Satellite observations, model outputs and reanalysis data are used to explore the related mechanisms. In 2019, the combined effects of northward local wind anomaly due to extreme positive IOD and westward-propagating downwelling Kelvin wave driven by the easterly anomaly in eastern Sri Lanka weaken the upwelling in the SEAS, leading to warm SST anomaly and suppressing the upward transport of the subsurface nutrients to the surface. A weaker positive IOD occurred in 2015, leading to stronger upwelling in the SEAS than during 2019. Yet, seawater in the SEAS experienced extreme warming (lowest SST exceeded 28.5oC) due to the development of super El Niño in 2015. The significant seawater warming can shoal mixed layer and prevent the nutrients in the subsurface from reaching surface, which is unfavorable for the chlorophyll growth. The thermal balance analysis suggests that the extreme warming in the SEAS was mainly related to more downward shortwave radiation.
OS16-A021
Residual Overturning Circulation in the East/Japan Sea
Yujin KIM+, Hajoon SONG#
Yonsei University, Korea, South
An overturning circulation connects the surface ocean to the interior and is a critical component of the global climate system. The overturning circulation also exists in the East/Japan Sea (EJS), a marginal sea surrounded by Korea, Japan, and Russia, evidenced by a relatively high concentration of dissolved oxygen in the deep sea. However, there are not enough studies on overturning circulation. In particular, the residual circulation, which includes the role of eddies in addition to the wind-driven Eulerian circulation, has not yet been calculated in the EJS, even with its significant role in distributing heat, salt, freshwater, and other tracers. As a result, the contribution of eddies to the overturning circulation has not been discussed in the EJS yet. Here, we use a regional ocean model configured in the Northwest Pacific to compute the residual circulation in the EJS. In the annual average circulation, the clockwise circulation at 36-41°N appeared both in the Eulerian and residual circulation. The latitudes at which subsidence occurs during summer and winter were different. Eddy-driven circulation, the difference between residual and Eulerian circulation, intensified or weakened the circulation at 700m depth.
OS16-A022
Impact of Phytoplankton-induced Change in Mixed Layer Depth on Carbon Export Production in the Subpolar North Atlantic: A Modeling Assessment
Zhuowei XU1+, Liuqian YU1#, Qing LI2
1The Hong Kong University of Science and Technology (Guangzhou), China, 2The Hong Kong University of Science and Technology, China
Phytoplankton light absorption changes ocean optical properties, causing a vertical redistribution of heat that warms the ocean surface and cools the subsurface. The altered temperature distribution can modulate the mixed layer depth (MLD). Changes in MLD have long been recognized as a critical factor in governing the onset, duration, magnitude and variability of phytoplankton blooms, thus affecting carbon export production. However, the impact of phytoplankton-induced change in MLD on carbon export has been overlooked in most ocean biogeochemical models that do not account for the biological feedback to physics (e.g., phytoplankton light absorption). This work aims to assess how much phytoplankton light absorption modulates the seasonal cycle of MLD and to what extent these changes escalate to affect the timing, evolution, and magnitude of phytoplankton bloom and consequently the carbon export production. To achieve the goal, we set up a one-dimensional physical-biogeochemical model that explicitly resolves the bio-optical attenuation and its feedback on heat flux and ocean physics. The model is optimized to best reproduce the climatological annual cycles of phytoplankton biomass in the Subpolar North Atlantic, a region characterized by massive spring blooms. By conducting a series of model experiments with and without activating the feedback from biology to physics, we assess the impact of phytoplankton light absorption on upper ocean dynamics and carbon export production. Implications of this assessment for including such biological-physical feedback mechanisms in climate models will also be discussed.
OS16-A026
Assessment of the Impact of Ultraviolet Radiation on Global Marine Primary Productivity Observations
Weili CHEN#+, Ya-Wei LUO
Xiamen University, China
Oceans contribute nearly half of the global net primary productivity (NPP). Therefore, accurate assessment of its level plays a key role in understanding the global carbon cycle, climate change and ecosystem functions. It is found that ultraviolet radiation (UVR) has negative and positive effects on marine NPP. Nevertheless, the majority of culture flasks currently used have low transmittance to UVR, thus shielding the UVR effects on marine NPP. In our study, based on existing research, we use a multivariate generalized additive model (GAM) to analyze the UVR effects on marine NPP. The predictors are UVA (320-400 nm) and UVB (280-320 nm) irradiance, cell size obtained by mesh filtration, and primary productivity with UV shielding, and the response factors are the effects of UVR in UVA and UVB bands on NPP. The models are further applied to obtain corrected values. The results show that there is little difference between the global marine NPP estimations from satellite remote sensing and NPP values after UVR correction. Spatially, there are significant differences in the UVR effects: (1) in the vertical distribution, UVR significantly inhibits surface NPP, but at deeper depths, UVR (mainly UVA) promotes it; (2) in the horizontal distribution, mainly affected by cell size, UVR inhibits nearshore NPP but promotes it in the open ocean at low latitudes and mid-latitudes; and (3) in the latitudinal distribution, also mainly controlled by cell size, UVR inhibits NPP in the Northern Hemisphere but promotes it in the Southern Hemisphere. Overall, UVR may not significantly change the estimation of the global marine primary productivity total level, but its impact on NPP in different sea areas and water depths is quite different. This provides a certain reference value for further research.
OS16-A028
Influence of Power Plant Cooling Water Discharge on the Biogeochemical Processes in Daya Bay, China
Hanying CAO+, Yunpeng LIN, Fukang QI, Jingping XU#
Southern University of Science and Technology, China
Water samples collected at 25 stations in the summer of 2022 were analyzed for the lateral and vertical distribution of temperature, salinity, Chlorophyll-a, nutrients (including nitrates, ammonium, nitrites, and phosphates), particulate organic carbon and nitrogen (POC and PN), and carbon isotopic composition (δ13CPOC) within the water column of Daya Bay, a coastal embayment in Guangdong province, China. The mean nutrient concentrations are 4.6 μmol L-1 for dissolved inorganic nitrogen (DIN, include NH4+, NO2−, and NO3−) and 0.2 μmol L-1 for reactive phosphate (DIP, mainly H2PO4−) respectively, and all increase toward the bottom. The nutrient ratio (DIN/DIP=23) was greater than the Redfield value (16:1), suggesting phosphorus limited in Daya Bay. The δ13CPOC and C/N ratio ranged from -23.84‰ to -18.95‰ and 3.95 to 6.91 respectively, suggesting a dominated marine source of POC. The cooling water discharge from the power plant increased the water temperature by 2-4°C and decreased the salinity by 2-4 PSU, compared to the surrounding water. Concentration of Chlorophyll-a, nitrate, and ammonium were found lower in the vicinity of the outlet of the cooling water discharge, probably resulting from degradation due to the high temperature inside the power plant. In contrast, the POC and PN concentrations at the outlet (0.9 and 0.17 mg L-1) were higher than those of the surrounding water (0.7 and 0.14 mg L-1). This is because (1) POC and PN concentrations are normally high near the surface (where the intake of cooling water is located), and (2) POC and PN are not as easily degradable as Chlorophyll-a or nutrients. Thus, even though the power plant’s cooling water discharge may have reduced the primary productivity, it may not have significantly changed the deposition and burial of organic matter in the area.
OS16-A029
Study of Cohesive and Non-cohesive Sediment on the Northern Bay of Bengal Shelf Using ROMS-CSTMS Climatological Simulation
Mohd IMARAN1,2+, Arun CHAKRABORTY1#, Subhasish TRIPATHY1
1Indian Institute of Technology Kharagpur, India, 2SWAN ENERGY LIMITED, India
The Northern Bay of Bengal is one of the world's largest bays, receiving vast influxes of fresh water and sediment from India's monsoonal rivers at its head. We set up the integrated community sediment transport modelling system (CSTMS) within Regional Ocean Modelling System (ROMS) for our study domain in order to analyze the cohesive (silt) and Non cohesive (sand) sediments. The model was stabilized after one year of simulation, and as it nears the end of its full run, it gets even more stable. We have tested the model under two alternative scenarios: (1) with river and (2) without river simulation, to understand the sediment dynamics close to the coast. The Ganges-Brahmaputra, Mahanadi, and Irrawaddy Rivers revealed a very high vertically averaged silt and very low sand at their mouths while presence of river in simulation. Additionally, where the averaged silt concentration is very high, the bottom stress brought on by wave-current interaction is also strong. Furthermore, bottom stress is the primary cause of sediment migration near the coastal zone. Due to sand's faster settling velocity than silt, it has a larger bed fraction than the silt. Moreover, the averaged silt and sand are also noticeably less at the mouths of the Ganges-Brahmaputra, Mahanadi, and Irrawaddy rivers when the rivers are not included in the simulation. The primary factors in the coastal water of the Bay of Bengal sediment transport modelling are water quality and flow calculations on time scales of days to seasons. Finally, the model output is compared to the satellite that was observed, and the findings show a good agreement.
PS01-A001
A Comparison of the Ionospheric Dynamo Current of Mars Above the Landing Sites of Insight and Zhurong: Modeling and Observations
Lin TIAN+, Hao LUO#
Chinese Academy of Sciences, China
Previous observational studies suggest that the surface time-varying magnetic field of Mars originates in large part from the dynamo currents in the Martian ionosphere [Johnson et al., 2020; Lillis et al., 2019; Mittelholz et al., 2020a; Mittelholz et al., 2020b]. However, it needs further study whether there are significant differences in the strength, the configuration, and the diurnal and seasonal variation of the dynamo current in different regions of the Martian upper atmosphere. This study compares the similarities and differences between the wind driven dynamo current over the InSight landing site (4.50° N, 135.62° E) and the Zhurong rover (25.07° N, 109.90° E). The results show that the dynamo current as well as its magnetic signal at around perihelion on surface at Zhurong is smaller than that at InSight due to weaker magnetic field in the ionosphere. This study also indicates that the seasonal effect, or the solar zenith angle (SZA), would affect the plasma density which should be included when dealing with off-equatorial locations. The direction and strength of the magnetic field and neutral wind, along with SZA, impact the intensity of the dynamo currents at Zhurong. The study provides a reference in an attempt to promote the understanding of the solar wind – Mars induced magnetosphere – ionosphere – Mars surface coupling process.
PS01-A002
The Injections of Plasma and Aurorae at Jupiter
Zhonghua YAO#+
The University of Hong Kong, Hong Kong SAR
Jupiter’s powerful auroral emissions include a substantial component from the region at lower latitudes than the main auroral oval, named outer auroral emission. Besides the persistent auroral footprint of Jupiter’s natural moon Io, auroral injections are often observed in the outer auroral region, manifesting the magnetospheric plasma injection from the middle/outer magnetosphere to the inner magnetosphere. Magnetospheric plasma injections sometimes have auroral counterparts, while sometimes have not. It is yet to be understood what controls the auroral counterparts of magnetospheric plasma injections. In this presentation, we show a long-lasting auroral injection events captured by the Hubble Space Telescope, together with simultaneous particle measurements from the Juno spacecraft. Multiple auroral substructures were identified in the injection region, which is likely associated with the observed filament plasma injections. A comparison between terrestrial and jovian processes could greatly help the understanding of auroral injection from a universe perspective.
PS01-A004
Study on Magnetic Field Signature of Intermediated-sized Impact Craters: Modeling and Observations
Kuixiang ZHANG#+
Chinese Academy of Sciences, China
Impact cratering is a dominant geologic process on Mars, with the crust demagnetized or remagnetized in the presence of a dynamo field. Thus the large impact craters are used to constrain the history of the Martian dynamo, however, the absence of crustal magnetic fields above the large basins suggesting the core dynamo cessation during their formation is controversial. Because impacts could excavate large portions of the strongly magnetic crust, making craters demagnetization completely even when the dynamo is alive. We select the intermediated-sized craters (150 km ~ 500 km in diameter) on Mars whose magnetic anomalies are associated with the topography. we find that the magnetic field magnitude of craters in the South Province is weak and has no magnetic edge effect, in other words, the crust is formed without an active Martian dynamo. We compare the observed magnetic field signature to the random magnetization model, the results show that the magnetic field variation (Bin/out) caused by impact and crater diameters are anti-correlation. Combining with the absolute model age of craters, we conclude that the Martian dynamo may start after the primordial crust formed, become weak or even cease at about 4.0 Ga, and likely become stronger or restart at about 3.7 Ga. High-resolution magnetic field characteristics analysis of more young and small impact craters will be required to constrain the evolution of the martian dynamo accurately.
PS01-A005
Long-term Monitor of Cometary Materials and the Potential Influences on the Earth During the Close Visit
Yong ZHAO1#+, Zhonghua YAO2
1Chinese Academy of Sciences, China, 2The University of Hong Kong, Hong Kong SAR
The stunning tails of comets are interesting astronomical phenomena to human beings and have been noticed for thousands of years. The bright tails also emit substantial materials into interplanetary space, including dusts and charged particles. The charged particles are picked up by solar wind magnetic fields, and thus could propagate together with solar wind to influence planetary space environments. In this presentation, we show the variation of cometary materials for successive days and potential influences on the Earth during close visit.
PS01-A006
Hourly Periodic Variations of Ultralow-frequency (ULF) Waves in Jupiter’s Magnetosheath
Weidong GU1#+, Zhonghua YAO2, Dongxiao PAN3, Yan XU4, Binzheng ZHANG2, Peter DELAMERE5, Suiyan FU6, Lun XIE6, Shengyi YE7, Yuening CHEN7, William DUNN8, Yong WEI4
1Institute of Geology and Geophysics, Chinese Academy of Sciences, China, 2The University of Hong Kong, Hong Kong SAR, 3China University of Geosciences, China, 4Chinese Academy of Sciences, China, 5University of Alaska Fairbanks, United States, 6Peking University, China, 7Southern University of Science and Technology, China, 8University College London, United Kingdom
Periodic variations are widely identified in Jovian system, varying from 10s of seconds to several days or even longer. These processes are strongly influenced by solar wind conditions, planetary rotation and Io’s volcanic activity. The ultralow-frequency (ULF) waves at 10s of minutes, which are the typical time scale of field-line resonance, are considered as a crucial process in driving Jovian energy circulation. The longer time-scale periodicities are likely associated with global mass circulation. While in this study, we focus on multi-hour variations of the ULF wave energy, which are difficult to identify within the magnetosphere due to the rapid planetary rotation modulation. Using the magnetic field observations from Juno and Galileo in Jupiter’s magnetosheath, we found multiple significant multi-hour periodicities, widely distributed from 2 to 10 hours, peaked at different values from case to case. The most common periodicities were between 3h and 5h, existing in both the dawn and dusk sides. These common periodicities are likely associated with the energy transport from inside to the magnetosheath.
PS01-A007
Excitation of Saturnian ECH Waves Within Remote Plasma Injections: Cassini Observations
Minyi LONG+, Xing CAO#, Xudong GU, Binbin NI
Wuhan University, China
Based on Cassini observations, we report representative electrostatic electron cyclotron harmonic (ECH) wave events observed in Saturn’s magnetosphere within remote plasma injections. Unlike local injections, remote injections are ‘older’ injection events that have evolved to form a dispersed signature in particle energy spectrum. We show that Saturnian ECH waves within remote injections present a strong fundamental band and much weaker high harmonic bands. By calculating the linear wave growth rates based on the measured electron distributions, we indicate that Saturnian ECH waves can be excited by the loss cone distribution of remotely injected, hot electrons of ~100 eV to several keV. We find that ECH waves tend to intensify with increased fluxes of injected hot electrons but weaken with increased evolution time of the flux tubes, which is consistent with the results of wave growth rates and improves the current understanding of the generation of ECH waves at Saturn.
PS01-A011
Automated Classification of Auroral Images with Deep Neural Networks
Zhiyuan SHANG#+
Chinese Academy of Sciences, China
Terrestrial auroras are highly structured that visualize the perturbations of energetic particles and electromagnetic fields in Earth’s space environments. However, the identification of auroral morphologies is often subjective, which results in confusion in the community. Automated tools are highly valuable in the classification of auroral structures. Both CNNs (convolutional neural networks) and transformer models based on the self-attention mechanism in deep learning are capable of extracting features from images. In this study, we applied multiple algorithms in the classification of auroral structures and performed a comparison on their performances. Trans-former and ConvNeXt models were firstly used in the analysis of auroras in this study. The results show that the ConvNeXt model can have the highest accuracy of 98.5% among all of the applied algorithms. This study provides a direct comparison of deep learning tools on the application of classifying auroral structures and shows promising capability, clearly demonstrating that auto-mated tools can help to minimize the bias in future auroral studies.
PS01-A016
Magnetic Field Structures in the Near-terminator Induced Magnetospheres of Venus and Mars
Sudong XIAO1#+, Tielong ZHANG2,3, Guoqiang WANG1, Ming-Yu WU1, Tong DANG3, Yuequn LOU1, Yuanqiang CHEN1
1Harbin Institute of Technology, China, 2Austrian Academy of Sciences, Austria, 3University of Science and Technology of China, China
Venus and Mars, our two neighboring planets, have no global intrinsic magnetic fields, and the induced magnetospheres are formed in their solar wind interactions through mass loading of magnetic flux tubes carried by the solar wind and draping around the highly conducting ionosphere. Although they have similar global magnetic environments in their induced magnetosphere controlled by the interplanetary magnetic field and the solar wind motional electric field, their differences in planetary size, solar wind conditions, crustal magnetic fields, etc. also have measurable impacts. We comparatively study the magnetic field structures in the Venusian and Martian induced magnetospheres near the terminator via observations. The nature of their current systems and the features of magnetic structures such as flux ropes are examined in the near-terminator space and the effects of solar activity, interplanetary magnetic field, and crustal fields are explored. The results reveal the solar wind interaction with unmagnetized planets near the terminator, and a simulation provides a three‐dimensional view.
PS01-A020
Magnetic Reconnection in Jupiter's Undulating Magentodisk Current
Ruilong GUO1#+, Z. H. YAO2
1Shandong University, China, 2Chinese Academy of Sciences, China
Magnetic reconnection is crucial in magnetospheric dynamics and aurora borealis processes on planets. Magnetic reconnection is often identified in the diurnal magnetopause and the magnetotail. At Jupiter, rapid rotation and internal mass sources lead to an additional magnetodisk current sheet that encircles the planet. It is generally accepted that the magnetodisk reconnection site begins in the pre-evening sector and ends in the dawn sector before encountering the magnetopause. Here we demonstrate that the magnetodisk reconnection is not restricted to the night side but discretely distributed at all local times inside the magnetosphere. The reconnection sites also rotate with the magnetosphere, and the corresponding disturbed current exhibits undulating features.
PS01-A021
Global Spatial Distribution of Dipolarization Fronts in the Saturn's Magnetosphere: Cassini Observations
Sibo XU+, Shiyong HUANG#
Wuhan University, China
Dipolarization front (DF), characterized by a sharp increase of the south-north component of the magnetic field, is suggested to play an important role in transferring plasmas, magnetic fluxes, and energy in the planetary magnetosphere. Using the measurements from the Cassini spacecraft between January 1, 2005 and June 15, 2011, we successfully selected 96 DF events, and obtained the global spatial distribution of DFs in the Saturn's magnetosphere. For the first time, we found that DFs are distributed not only in the nightside magnetotail but also in the dayside magnetosphere. The dayside DF events are mainly located from X = 10 RS to X = 30 RS (RS is the Saturn's radius) while the nightside events have a wide range, up to X∼−50 RS. Moreover, the DFs are observed to be asymmetric in the south-northern hemisphere: ∼70% of events in the northern hemisphere and ∼30% of events in the southern hemisphere, which is likely to be due to the asymmetric orbit coverage of the Cassini in south-northern hemisphere. The occurrence of dayside DFs provides a strong evidence that the magnetic reconnection could also occur in the dayside of Saturn's magnetosphere. Thus, our results concerning the location and distribution of DFs are helpful for the study of the site of magnetic reconnection and energy transport/dissipation in Saturn's magnetosphere.
PS01-A024
Prediction of Axial Asymmetry in Jovian Magnetopause Reconnection
Junjie CHEN1#+, Binzheng ZHANG1, Dong LIN2, Peter DELAMERE3, Zhonghua YAO1, Oliver BRAMBLES4, Kareem SORATHIA5, Viacheslav MERKIN5, John LYON6
1The University of Hong Kong, Hong Kong SAR, 2National Center for Atmospheric Research, United States, 3University of Alaska Fairbanks, United States, 4O.J. Brambles Consulting, United Kingdom, 5Johns Hopkins University Applied Physics Laboratory, United States, 6Dartmouth College, United States
We show the possible existence of a significant axial asymmetry in the reconnection separator at the Jovian magnetopause using first-principle, physics-based global simulations. Under eastward interplanetary magnetic field (IMF) conditions near Jupiter’s orbit, reconnection occurs at the southern-dusk and northern magnetopause with large shear angles between the magnetospheric and magnetosheath magnetic fields. When driven by the westward IMF, the reconnection position switches to the northern-dusk and southern magnetopause. Component reconnection at the southern-dusk/northern-dusk magnetopause is associated with the interaction of the IMF with the nearly-dipolar background fields. Nearly-antiparallel reconnection near the noon-midnight plane at the northern/southern magnetopause is related to the dawn-dusk asymmetric, helical, closed lobe magnetic fields, which is a consequence of significant planetary corotation effects and not expected at Earth. Such configuration is testable as Juno has proceeded its orbit to the high-altitude cusps and provides new insight into the interpretation of measurements from other rotationally-driven systems.
PS01-A028
The Responses of Jovian Broadband Kilometric Radio Emissions to Different Compressional Conditions
Yuening CHEN1#+, Shengyi YE1, Zhonghua YAO2
1Southern University of Science and Technology, China, 2The University of Hong Kong, Hong Kong SAR
In planetary magnetosphere, plasma waves act as the medium for particles to transfer energy. Jupiter is the largest planet in our solar system, and the giant magnetosphere is full of energetic particles, producing intense radio emissions. When shock waves in the solar wind interact with the Jovian magnetosphere, the characteristics of Jovian radio emissions show distinct variations accordingly. This study focuses on the morphological characteristics of Jovian broadband kilometric radio emissions under different solar wind compressional conditions, i.e., quiet and compressed. Using observations from Juno and the Hubble Space Telescope, both the frequency range and duration of Jovian broadband kilometric radio emissions are studied, and we compared their variations during compressed and quiet solar wind conditions. Our results show that the frequency range of Jovian broadband kilometric radio emissions was greater under solar wind compression conditions, together with significantly longer duration. The distinct features of radio emissions under different solar wind conditions imply that solar wind conditions have important influences on Jovian auroral processes, and thus the radio emissions can be used as a diagnostic tool of solar wind interaction with Jovian magnetosphere.
PS01-A029
A Rapid Localized Deceleration of Earth's Radiation Belt Relativistic Electrons Driven by Storm Proton Injection
Zhaoguo HE1#+, Zhenpeng SU2
1Sun Yat-sen University, China, 2University of Science and Technology of China, China
Earth's radiation belt relativistic electron dropouts frequently occur during the main phase of geomagnetic storms, which have been partially attributed to the ring current ion enhancements causing geomagnetic field reconfigurations. In contrast to early studies on the global radiation belt response to the ring current buildup on a timescale of several hours, we here describe a rapid, localized, significant decay of relativistic electrons driven by freshly injected energetic protons during the 27 May 2017 geomagnetic storm. Near the proton injection front, the magnetic field lines were stretched outward, with an inferred migration of their equatorial crossings by ∼0.5 RE during several minutes. Because of the betatron and Fermi decelerations, the relativistic electron fluxes decreased by 2–3 orders of magnitude with pitch-angle distributions evolving from pancake/flat-top type to cigar type. This rapid localized response pattern of relativistic electrons could be general over strong particle injections during both geomagnetic storms and substorms.
PS02-A002
Measuring the Depth of Planetary-scale Changes in Jupiter from Juno Microwave Radiometer Observations
Glenn ORTON1#+, Shawn BRUESHABER2, Michael H. WONG3, Thomas MOMARY1, Steven LEVIN4, Scott BOLTON5, Kevin BAINES6, Emma DAHL1, James SINCLAIR1
1Jet Propulsion Laboratory, California Institute of Technology, United States, 2Western Michigan University, United States, 3SETI Institute, United States, 4California Institute of Technology, United States, 5Southwest Research Institute, United States, 6University of Wisconsin-Madison, United States
We report on variability of the microwave brightness of Jupiter’s axisymmetric bands over 2016-2022 using Juno Microwave Radiometer (MWR) observations. We first examined the depth of changes in regions where visible changes have taken place. The variability in channels sensitive to depths of 9-50 bars of pressure are generally much smaller than those at pressures of 0.7-3 bars. An exception to this is in the northern component of Jupiter’s Equatorial Zone (2°N-6°N), whose variability at depth does not correspond to any visible feature in the upper atmosphere, although it might be a precursor to the short-lived 2018-2019 Equatorial Zone disturbance. At 0.7-3 bars, a decrease in the antenna temperature in the northern component of the North Equatorial Belt (12°N-15°N) is coincident with its visible brightening and drop of 5.1-µm radiance, both implying increased cloud and NH3 opacity in 2021. Even though the visibly dark North Equatorial Belt expanded northward into latitudes more typically associated with visibly bright regions that are cold at 5.1 µm (16°N-19°N), known as the North Tropical Zone (Fletcher, et al. 2017. Geophys. Res. Lett. 44, 7140), we do not detect any corresponding change of the MWR antenna temperature. Although there are substantial changes in the visible and 5.1-µm appearance of the northern component of the North Temperate Belt (24°N-26°N) as well as in the MWR antenna temperatures, the two do not appear to be correlated with one another. An important part of our next steps in this research will be to examine which of the MWR variabilities in the zonal-mean microwave brightness are the result of zonally discrete features in the atmosphere, particularly the North Equatorial Belt (6°N-15°N).
PS02-A014
A Juno-era View of Electric Currents in Jupiter's Magnetodisk
Zhiyang LIU1#+, Qiugang ZONG1, Michel BLANC2
1Peking University, China, 2Institute for Research in Astrophysics and Planetology, France
Recent observations from Juno provided a detailed view of Jupiter's magnetodisk, including its magnetic fields, waves, plasmas and energetic particles. Here, we contribute to Juno results by determining the electric currents threading the magnetodisk and their coupling to field-aligned currents (FAC) in the midnight-to-dawn local time sector. We first derive from Juno magnetic field data the spatial distributions of the height-integrated radial (Ir) and azimuthal (Ia) currents in the magnetodisk, and then calculate the FACs from the divergence of the two current components. The Ir-associated FAC, Jr, flows into and out of the magnetodisk at small and large radial distances, respectively, approximately consistent with the axisymmetric corotation enforcement model. On the other hand, Ia decreases with increasing local time everywhere in the local time sector covered, indicating an additional FAC (Ja) flowing out of the magnetodisk. From Ia and Ja, we conclude that the influence of the solar wind, which compresses the dayside magnetosphere and thus breaks the axisymmetry of currents and fields, reaches deep to a radial distance of at least 20 Jupiter radii. Our results provide observational constraints on Jupiter's magnetosphere-ionosphere-thermosphere coupling current systems, on their relation to the main auroral emission and on the radial mass transport rate in the magnetodisk, which we estimate to be close to ~1500 kg/s.
PS04-A002
Photoelectron Boundary: The Top of the Dayside Ionosphere at Mars
Shaosui XU1#+, David MITCHELL1, James MCFADDEN1, Christopher FOWLER2, Gwen HANLEY1, Tristan WEBER3, David A. BRAIN3, Yingjuan MA4, Gina DI BRACCIO5, Christian MAZELLE6, Shannon CURRY1
1University of California, Berkeley, United States, 2West Virginia University, United States, 3University of Colorado Boulder, United States, 4University of California, Los Angeles, United States, 5NASA Goddard Space Flight Center, United States, 6Institute for Research in Astrophysics and Planetology (IRAP), National Center for Scientific Research (CNRS) - University of Toulouse (UPS) - National Center for Space Studies (CNES), France
The interaction between Mars and the solar wind results in different plasma regimes separated by several boundaries, among which the separation between the sheath flow and the ionosphere is complicated. Previous studies have provided different and sometimes opposite findings regarding this region. In this study, we utilize observations from the Mars Atmospheric and Volatile EvolutioN (MAVEN) mission to revisit boundaries within this region and perhaps reconcile some differences. More specifically, we start with the photoelectron boundary (PEB), a topological boundary that separates magnetic field lines having access to the dayside ionosphere (open or closed) from those connected to the solar wind on both ends (draped). We find that large gradients in the planetary ion density occur across the PEB and that the dominant ion switches from heavy planetary ions to protons near the PEB, indicating the PEB falls within the ion composition boundary (ICB). Furthermore, our results show that the PEB is not a pressure balance boundary; rather the magnetic pressure dominates both sides of the PEB. Meanwhile, we find that the PEB is located where the shocked solar wind flow stops penetrating deeper into the ionosphere. These findings suggest the PEB marks the top of the Mars dayside ionosphere and also the interface that the sheath plasma flow deflects around the obstacle going downstream.
PS04-A004
Sporadic E-like Event Driven by Wind Shear in the Martian Ionosphere
Rong TIAN#+, Chunhua JIANG
Wuhan University, China
Sporadic E is the oldest known ionospheric disturbance on Earth, which can affect the propagation of radio signals. According to recent studies, Es-like events on Mars are driven by magnetic shear. The rift, which was not observed on Earth, was also observed on Mars. While both magnetic and wind shear can theoretically drive the formation of Es-like events, no observational evidence shows that wind shear can also drive the formation of Es-like events on Mars. In this study, we report a new observation of a sporadic E-like (Es-like) event with both layer and rift in the ionosphere of Mars by NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Wind shear was observed during the event, and our preliminary statistics suggest that wind shear may be a common phenomenon on Mars. This study provides new observations of Es-like events on Mars and constructs a picture of Es-like events through observations of neutral wind fields from NGIMS. The observational result supports the theory that wind shear could drive Es-like events on Mars.
PS04-A006
Partial Absorption of Surface Echoes Observed by MARSIS During the December 2014 Solar Event at Mars: Initial Results from a Data-model Comparison
Yuki HARADA1#+, Yuki NAKAMURA2, Beatriz SANCHEZ-CANO3, Mark LESTER3, Naoki TERADA2, Francois LEBLANC4
1Kyoto University, Japan, 2Tohoku University, Japan, 3University of Leicester, United Kingdom, 4National Centre for Scientific Research, France
Solar energetic particles (SEPs) drive a variety of phenomena in planetary atmospheres. At Mars, the SEP precipitation leads to the global emission of "diffuse aurora" from the nightside atmosphere. Since the recent discovery of the Martian diffuse aurora, their properties have been investigated from both observation and modeling perspectives. A Monte Carlo model developed by Nakamura et al. is one of the numerical models solving the interaction between SEPs and the Martian atmosphere. Based on the measured SEP energy spectra, this model is capable of reproducing the peak altitude and relative altitude profile of the observed auroral emission. The new model by Nakamura et al. also provides the altitude profile of electron density in the nightside ionosphere of Mars during SEP events, thereby suggesting another use case of data-model comparison focusing on "radar blackouts" at Mars. Radar blackouts refer to a significant attenuation of trans-ionospheric radar signals from Martian orbiters caused by enhanced ionization and electron-neutral collisions below ~100 km altitudes as often observed during SEP events. The degree of signal attenuation provides a proxy for the low-altitude electron densities that are otherwise difficult to measure. We investigate the evolution of the low-altitude electron densities during SEP events and discuss the relative roles of different ionizing agents by comparing Nakamura et al.'s model against the radar signal attenuation recorded in the MARSIS Active Ionospheric Mode data during the December 2014 SEP event. We report the initial results from the data-model comparison.
PS04-A007
Escape of Martian Ionospheric Proton Due to the Resonant and Non-resonant Interactions with Large-amplitude Magnetosonic Waves
Xiaotong YUN1+, Fu SONG1#, Binbin NI1, Jun CUI2,3
1Wuhan University, China, 2Sun Yat-sen University, China, 3Chinese Academy of Sciences, China
Ion escaping frequently occurring in the Martian space leads to a significant influence on Martian plasma and atmospheric environment. However, the dominative mechanism of ion escaping remains unclear. In this study, we quantitatively investigate the wave-induced proton escaping driven by large amplitude magnetosonic (MS) waves in the Martian ionosphere. The resonant condition analysis shows that via Landau resonance the protons with Ek0 = ~10–104 eV can interact with MS waves. By using our developed test particle code, we simulate the proton dynamics and find that on the time scale of ~6 s, the MS waves combined with the crustal magnetic fields scatter the protons’ pitch-angle as <(Δα)2> = 10-2–10-1 rad2 and diffuse the protons’ energy as <(ΔEk/Ek0)2> = ~ 10-2. The calculations also suggest that beyond the Landau resonance, the non-resonant effect can effectively scatter the protons with lower energy ~1–10 eV. Furthermore, to represent the proton escaping at the topside of the crustal magnetic field, we construct a global test particle simulation code involving the wave scattering effect. The results suggest that the net proton escaping probability caused by the MS wave-driven resonant and non-resonant process is 0.6269%, which is ~2 times higher than that without MS waves. Our results indicate that the large-amplitude MS waves are very important on Martian ionospheric proton escaping by wave-particle interactions, which is helpful for better understanding the evolution of the Martian plasma and atmospheric environment.
PS04-A011
A Study of the Energy Spectrum of Photoelectrons and Auger Electrons Emitted from the Sunlit Lunar Surface
Masahisa KATO1#+, Yuki HARADA1, Shaosui XU2, Andrew POPPE2, Jasper HALEKAS3, Yohei MIYAKE4, Hideyuki USUI4, Masaki NISHINO5, Toru MATSUMOTO1
1Kyoto University, Japan, 2University of California, Berkeley, United States, 3The University of Iowa, United States, 4Kobe University, Japan, 5Japan Aerospace Exploration Agency, Japan
Since the moon does not have a dense atmosphere and its global intrinsic magnetic field, the lunar surface directly interacts with its ambient plasma. The lunar surface potential changes as a result of the interaction. Auger electron emission is one of the interactions between photons and solid surfaces. Auger electrons are emitted from the surfaces with characteristic energy depending on the chemical composition and the process. In this study, we developed a numerical model which explains an energy spectrum of photoelectrons and Auger electrons emitted from the lunar surface. Through this model, we discuss the electrostatic potential distribution with a height from the lunar surface.
PS04-A012
An Unexpected Double-peak Structure in Diurnal Variation of Martian Upper Atmosphere
Huijun LE#+, Libo LIU, Yiding CHEN, Ruilong ZHANG, Hui ZHANG
Chinese Academy of Sciences, China
Previous studies have shown that the Martian ionosphere and thermospheric atmosphere are mainly controlled by photochemical processes, especially near the peak electron density height of the ionosphere. Therefore, it can be considered that the diurnal variation of ionospheric electron density and thermospheric neutral density on Mars is mainly controlled by solar irradiation flux, which increases rapidly after sunrise, peaks around noon, and drops sharply after sunset. Maven has accumulated more than eight years of data since October 2014, covering different Martian seasons, local times, solar activity and altitudes. Through statistical analysis, we found for the first time that the diurnal variation of the ionospheric electron and ion density and thermospheric gas density of Mars has a significant double-peak structure, with the first peak appearing around LT 08-09, the second peak appearing around LT15-17, and an low value at ~LT12. To further confirm the accuracy of the results, we conducted empirical modeling of electron density, ion density and neutral gas density based on the LWP and NGISM observation data, and the model results reproduced the double-peak structure found statistically. This further confirms the double-peak structure of the ionosphere. These studies show that the changes in Mars' upper atmosphere are far more complex than we had expected, with direct effects from the solar wind above, effects from the lower atmosphere below, and strong dust storms that can propagate up to the upper atmosphere.
PS05-A007
Statistical Properties of Plateau-like Turbulence Spectra in the Martian Magnetosheath: Maven Observations
Hui LI1#+, Wence JIANG2, Xiaodong LIU2, Daniel VERSCHAREN3, Chi WANG2
1National Space Science Center, Chinese Academy of Sciences, China, 2Chinese Academy of Sciences, China, 3University College London, United Kingdom
The Martian magnetosheath provides us with a natural laboratory to study plasma turbulence in the presence of pickup ions and locally generated instabilities. Unlike the typical magnetic-field spectra with a single spectral scaling at magnetohydrodynamics (MHD) scales in Earth's magnetosheath, the magnetic-field spectra in the Martian magnetosheath during 4 years of Mars Atmosphere and Volatile EvolutioN observations frequently present an additional spectral break-point with a shallow slope at MHD scales which we define as a plateau-like spectral feature. The average occurrence rate of plateau-like magnetic-field spectra is 56.6% of our measurement intervals. At moderate pick-up angles, the occurrence rate increases to a maximum of ∼70.0%. Furthermore, we present a positive correlation with the local ion density and anti-correlations with the local βi and the solar Extreme Ultra Violet irradiance. A similar occurrence rate in the quasi-perpendicular and the quasi-parallel magnetosheath (60.1% vs. 52.9%) indicates that the plateau-like spectra are more likely formed locally than in the upstream solar wind. Our results suggest that energy injection from pickup ion driven micro-instabilities, for example, in the form of proton cyclotron waves, has insufficient time to evolve into a fully developed cascade in such a confined space like the Martian magnetosheath.
PS05-A008
ULF Modulations on Plasma Environment and Coherent Waves of Mercury's Magnetosphere: Messenger's Observation
Jiutong ZHAO#+, Qiugang ZONG
Peking University, China
Ultra low frequency (ULF) waves are fundamental waves that can energize, transport, and scatter charged particles in planetary magnetospheres. With the measurements from MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER), we investigate the proton flux fluctuations and coherent waves associated with a series of ULF waves on the flanks of Mercury's magnetosphere. The ULF waves are mainly compressional with a frequency of ∼15 mHz and significantly modulate the intensity of proton flux. The coherent waves accompanied by the ULF waves correspond to a higher frequency (∼1 Hz). The wave power and compressibility of the coherent waves vary quasi-periodically with the ∼15 mHz ULF waves. We conclude that the compressional ULF waves modulate the coherent waves with higher frequency. This modulation might result from the associated periodic proton flux changes and helps us understand the nature of the ∼1 Hz waves better.
PS05-A010
MMS Observations of Upstream 3-seconds Waves in Earth’s Foreshock Region
Gangkai POH1,2#+, Guan LE1, Scott BOARDSEN3, Norberto ROMANELLI1, Daniel GERSHMAN1, Weijie SUN4, Li-Jen CHEN1
1NASA Goddard Space Flight Center, United States, 2Catholic University of America, United States, 3University of Maryland, Baltimore, United States, 4University of California, Berkeley, United States
Ultra-low frequency (ULF) waves have been observed and studied extensively in the Earth’s ion foreshock region, with their basic wave properties determined. ULF waves can be formed from the backstreaming ions in the ion foreshock region upstream of the bow shock when the solar wind interacts with the terrestrial bow shock. However, many questions regarding their plasma characteristics and generation mechanisms remain unanswered. One example of such ULF waves are the 3-seconds wave first observed in the ISEE magnetometer data [Le et al., 1992; Blanco-Cano et al., 1999] and more recently by MMS [e.g. Wang et al., 2021]. This class of ULF waves are always right-handed with periods near 3 seconds, near circularly polarized in the spacecraft frame, and typically occur in regions of high plasma β and are often associated with suprathermal ion populations. In this study, we presented magnetic field and plasma measurements of case study and statistical analysis of 3-seconds waves as observed by MMS upstream of the Earth’s ion foreshock region. We surveyed 3 months of MMS magnetic field and plasma data and identified ~25 potential 3-seconds wave intervals as observed by MMS. Using FFT and minimum variance analysis, we confirmed that these waves have frequency of ~0.3 Hz (or 3.3s), and are near circularly right-handed polarized in the s/c frame, consistent with earlier studies. We also analyzed the MMS FPI Burst mode data during observations of these 3-second waves to determine the ion distribution functions, which is then input into a dispersion solver to determine the instability that generated these 3-second waves.
PS05-A011
MESSENGER Observations of Distribution of Planetary Ions Near Mercury’s Space: Their Escape Rates and Dependence on True Anomaly Angle
Weijie SUN1#+, Ryan DEWEY2, James SLAVIN2, Jim RAINES2, Gangkai POH3,4
1University of California, Berkeley, United States, 2University of Michigan, United States, 3NASA Goddard Space Flight Center, United States, 4Catholic University of America, United States
This study presents MESSENGER observations of the distribution of O+-group ions and Na+-group ions in the regions near Mercury’s space. The regions include the solar wind, magnetosheath, and magnetosphere. We have investigated the distributions of O+-group ions and Na+-group ions in these regions separately and divided them into four true anomaly angles (TAAs) groups. We have shown their distributions under convection electric field coordinates. The densities of O+-group ions and Na+-group ions are the highest in the magnetosphere and the lowest in the solar wind, and their densities show clear dependencies on the TAAs. The escape rates of the O+-group ions and Na+-group ions are estimated in different regions and different TAA intervals.
PS05-A013
Validation of the AWSoM Solar Wind Magnetic Field Model with Upstream Mercury Solar Wind Conditions from MESSENGER Observations
Rayta PRADATA1,2#+, Gangkai POH2,3, Ana PERUZA4, Zhenguang HUANG5, Nishtha SACHDEVA5, Evangelia SAMARA6
1University of Delaware / Catholic University of America, United States, 2NASA Goddard Space Flight Center, United States, 3Catholic University of America, United States, 4George Mason University, United States, 5University of Michigan, United States, 6Royal Observatory of Belgium, Belgium
Previous studies from MESSENGER have shown that plasma dynamical processes within Mercury’s magnetosphere are strongly driven by its solar wind conditions. However, the upstream region of Mercury’s magnetosphere has no constant solar wind monitor to provide information about them when the spacecraft is inside the planet’s plasma environment, which emphasizes the importance of a solar wind model to accurately predict their conditions. This project aims to validate and assess the capability of the Alfvén Wave Solar Atmosphere Model (AWSoM) developed at the University of Michigan in predicting solar wind Interplanetary Magnetic Field (IMF) condition (polarity and magnitude) by comparing its simulated outputs with solar wind data from MESSENGER. We have identified solar wind intervals in the MESSENGER’s magnetic field measurements from three Carrington Rotations (i.e. CR 2132, 2138, and 2139) to be compared with AWSoM’s simulation results using ADAPT-GONG magnetograms as the input. Each of the 12 ADAPT realizations for each Carrington rotation period was compared with the solar wind data IMF measurements, and assessed on how well they agree with MESSENGER’s observations. The comparative analysis technique Dynamic Time Warping (DTW) is used to make this assessment in this study, due to the time-shifted alignment typically observed between the observed and simulated solar wind data. The technique is implemented on all 12 realizations of each simulation run to determine the “best-fit” comparison, accounting for the time shift, using the DTW “cost” or “score” parameter. The data-model comparison methods and results presented in this study will contribute to future studies related to solar activity and solar wind IMF, and applied towards other planetary environments (e.g. MAVEN for Mars) and future spacecraft missions to Mercury (e.g. Bepi-Colombo).
PS05-A016
Magnetic Shielding of Earth’s Atmosphere from the Solar Wind
Parker HINTON1#+, David A. BRAIN1, Neesha SCHNEPF1, Yingjuan MA2, Fran BAGENAL1
1University of Colorado Boulder, United States, 2University of California, Los Angeles, United States
For decades it has been accepted canon by many that Earth’s intrinsic magnetic field works to shield its atmosphere from escape caused by the solar wind (Watson and Junge 1962, Hutchins and Jakosky 1997, Lundin et al. 2007). This hypothesis has recently fallen under the criticism that even without an intrinsic magnetic field a magnetosphere will still be induced, which can protect the unmagnetized planet from solar wind ablation (Gunell et al. 2018, Ramstad et al. 2021). We use BATSRUS, a compressible multi-species magnetohydrodynamic code, to globally simulate the plasma interaction between the solar wind and Earth’s magnetosphere under two different scenarios i) the present-day dipole magnetic field and ii) demagnetized Earth (no intrinsic field). We present first results quantifying and comparing atmospheric escape between the two scenarios, helping answer the question as to whether or not Earth’s intrinsic magnetic field shields its atmosphere. We also explore what atmospheric escape from Earth may be like during geomagnetic reversal, which is when the Earth's magnetic field reverses polarity. Reversals occur in Earth's history on average every 450 ky. The last major event in the geologic record is the Brunhes–Matuyama reversal, which occurred 780 ky ago and lasted for 22 ky. Such an event can leave the Earth relatively unprotected by its generally strong intrinsic dipole magnetic field for an extended period of time.
PS05-A018
Global MHD Simulation of the Planetary Magnetosphere: Uranus and Neptune
Kyung Sun PARK#+
Chungbuk National University, Korea, South
Global magnetohydrodynamic (MHD) has successfully reproduced overall magnetospheric dynamics and ionospheric phenomena for the Earth. However, understanding how the energy and momentum transfer from the Sun to Uranus and Neptune is a complex problem with many different aspects. The surface magnetic field at the dipole equator of Uranus and Neptune have smaller than Earth. Also, one of the significant characteristics of Uranus and Neptune is that the rotation axis and the magnetic dipole axis are separated by a large angle. To understand where the magnetic reconnection occurs, how the reconnected field lines move to the tail, and how much energy is transported from the solar wind, I have performed a three-dimensional global MHD simulation to examine the effect of the tilt with a weak solar wind condition. The input parameter of the simulation used the average value of solar wind observed from Voyager 2 and NEW HORIZONS. The simulation box is (nx, ny, nz) = (600, 400, 400) with a uniform grid spacing of 0.5 Rp. The simulation results show the large-scale 3D magnetic field configuration and plasma flow in outer planetary magnetospheres and the main differences between the two planetary configurations will be discussed in this study.
PS06-A002
Desorption of Hydrogen Sulfide Induced by VUV Irradiation
Yen-Yu HSU1#+, Chun-Chi HUANG1, Yu-Jung CHEN1, Guillermo Manuel MUÑOZ CARO2
1National Central University, Taiwan, 2Centro de Astrobiología (INTA-CSIC), Spain
In cold dense clouds, most of the molecules should exist in the solid phase because of the low temperature near 10 K. However, astrophysicists can still observe a large number of gas phase molecules. Since thermal desorption is absent in this region, therefore photon-induced desorption or photodesorption is expected to contribute to the ejection of molecules from ice in cold regions of space. The secondary vacuum ultraviolet (VUV) field caused by the cosmic rays reacting with molecular hydrogen is a significant photon source in dark cloud interiors and radiation-protected circumstellar regions.
Hydrogen sulfide (H2S), one of the most abundant sulfide-bearing species in the interstellar medium (ISM), can be seen as a precursor of biochemical molecules. Oba et al. (2018) proposed the chemical desorption caused by hydrogen atoms should be more effective than the photodesorption in cold dense clouds. However, they estimated the value by the absorption cross-section of H2S instead of measuring its photodesorption directly. Under the VUV irradiation, Cazaux et al. (2021) showed H2Sx (x>1) and S-chain (Sx) molecules are the main photoproducts, but there is no photodesorption information in detail.
In this study, the effect of structure effect on VUV photondesorption of H2S ice was measured by depositing H2S ice at 13 K and 70 K, respectively. The results show that the photodesorption yield of H2S ice deposited at 13 K is higher than that deposited at 70 K, and this might be related to the binding energy and the effective surface area of ice. Furthermore, the H2S ices with different initial thicknesses were examined, and the energy transfer length for photodesorption is around 5−10 ML.
References:
1. Cazaux, S., et al. arXiv preprint arXiv:2110.04230 (2021).
2. Oba, Y., et al. Nature Astronomy 2.3 (2018): 228-232.
PS06-A007
VUV Photoinduced Energy Transfer in 13CO Ice Deposited on CO/CO2 Ice
Chun-Chi HUANG1#+, Yen-Yu HSU1, Guillermo Manuel MUÑOZ CARO2, Yu-Jung CHEN1
1National Central University, Taiwan, 2Centro de Astrobiología (INTA-CSIC), Spain
The VUV-induced photodesorption of CO ice has been studied in the last few decades. Chen et al. (2014) show that the process of CO photodesorption induced by VUV photons with broadband energy is more complex than the sum of individual processes induced by the monochromatic light source at the same energy range. It results from the difference in absorption cross-section between the parent molecules (CO) and photoproduct (CO2) in the Ly-α and molecular H2 emission ranges. In this study, 13CO ice (7 ML) is deposited on the top of CO or CO2 ice (18 ML) and irradiated by VUV photons with a high proportion of Ly-α emission (76.4%) produced by a microwave-discharged hydrogen flow lamp (MDHL). We find that for the 13CO ice deposited on the CO2 ice, the photodesorption yield of 13CO is higher than that deposited on CO ice. The result supports that more energy can transfer from products (CO2) to parent molecules (CO). Furthermore, the energy transfers from CO2 to CO decreases because CO2 dissociates into CO during the VUV irradiation.
PS06-A009
Formation of Insoluble Organic Material from the Ultraviolet Irradiation of Laboratory Ice Photolysis Residues
Michel NUEVO1#+, Brian FERRARI2,3, Scott A. SANDFORD1, Christopher J. BENNETT3, Yu-Jung CHEN4, Yu-Jong WU5
1NASA Ames Research Center, United States, 2Leiden Institute of Chemistry, Netherlands, 3University of Central Florida, United States, 4National Central University, Taiwan, 5National Synchrotron Radiation Research Center, Taiwan
We present preliminary results from the study of ice photolysis residues which were exposed to ultraviolet (UV)/extreme UV (EUV) photon radiation. The residues were produced from the simultaneous deposition and UV irradiation of ice mixtures of astrophysical interest (H2O, CH3OH, CO, NH3, without/with N2 and/or O2, and without/with small quantities of aromatic compounds) at 15–20 K using an H2 lamp, which emits 10.2-eV (121.6 nm) Lyman-α photons and a continuum at 7.5–8 eV (155–165 nm). After warm-up to room temperature and subsequent sublimation of volatile compounds, the refractory materials (residues) recovered at room temperature were analyzed with infrared (IR) microscopy and then further irradiated with UV/EUV photons at a synchrotron facility, on a beamline providing a broad-band photon beam in the 4–45-eV range with a ~1016 photons s-1 flux.2 The residues were UV/EUV irradiated with increasing photon doses ranging from ~1018 to ~1021 photons, i.e., covering 4 orders of magnitude and relevant to those experienced by ice-coated grains in the protosolar nebula.1. After UV/EUV irradiation, residues were analyzed with IR microscopy and the data compared to those before irradiation to identify changes in chemical composition as a function of the photon dose. UV/EUV-irradiated residues were also analyzed with other techniques such as nanoscale secondary-ion mass spectrometry (nanoSIMS) to the study the changes in isotopic composition, and scanning transmission electron microscopy to look at variations in structure and C bonding distribution. Results will be compared with data from extraterrestrial materials, in particular, meteoritic insoluble organic material (IOM) and interplanetary dust particles (IDPs). References: [1] Ciesla, F.J., Sandford, S.A., Science, 336, 452 (2012). [2] Nuevo, M., Chen, Y.-J., Hu, W.-J., et al., Astrobiology, 14, 119 (2014).
PS06-A012
Observations of Various Meteor Optical and Plasma Trails with MIOS and the Properties of Their Parent Meteoroids
Guozhu LI1#+, Yi LI1, Lianhuan HU1, Haiyong XIE2, Wenjie SUN1, Xiukuan ZHAO1, Baiqi NING1
1Chinese Academy of Sciences, China, 2Institute of Geology and Geophysics, Chinese Academy of Sciences, China
Meteoroids entering the Earth’s atmosphere significantly disturb the background ionosphere, producing ionized columns and plasma density irregularities, change the ionospheric composition, and even seed large-scale ionospheric irregularity structures. Under the support of the National Natural Science Foundation of China, the Meteor and ionospheric Irregularity Observation System (MIOS) facility, which consists of multi-station optical subsystem at Ledong (18.4°N, 109°E) and Sanya (18.3°N, 109.6°E), and radar subsystem including a 38.9 MHz all-sky interferometric radar and a 47.5 MHz coherent phased array radar at Ledong, was recently completed. The MIOS was specifically designed to have the following capabilities: (a) To simultaneously obtain radar and optical features of meteors within a large field of view; (b) To observe meteor echoes in specific directions with high sensitivity by steering a narrow radar beam; (c) To unambiguously locate meteor echoes using multi-baseline spatial-domain interferometry in order to identify field-aligned and non-field-aligned irregularities; (d) To observe the structural evolution of plasma density irregularities by steering a narrow radar beam on a pulse-to-pulse basis or by using fixed wide radar beam multi-baseline imaging techniques; (e) To obtain the physical and chemical properties of meteoroids producing/not producing meteor echoes. In this talk we will present some preliminary observations of various meteor optical and plasma trail phenomena and the properties of their parent meteoroids.
PS06-A013
Some Characteristics of the Geminids Meteor Shower Through TMDS Observations Between 2018 and 2022
Zhong Yi LIN1#+, Po-Chih CHUNG2, Jim LEE3, Hsin-Chang CHI4
1Institute of Astronomy, Taiwan, 2National Central University, Taiwan, 3Taipei Astronomical Museum, Taiwan, 4National Dong Hwa University, Taiwan
We have obtained the characteristics of the Geminid meteoroid stream by TMDS (Taiwan Meteor Detector System) through observations from 2018 to 2022. Meteors with radiant from Geminids are summarized as observed over an eligible period between early December and mid-to-late December amid the peak shower activity was found on Dec. 13. The associated solar longitude during this period is from 237° to 289° and the peak period is between 261° and 262°. In total, more than six thousand meteors have been identified as Geminids. The absolute magnitudes, the geocentric velocity, the radiant of the shower, and population index distributions are therefore statistically analyzed for comparisons with available investigations. No obviously outburst of the Geminids meteor shower has been detected. In addition, meteors with components from simultaneous multi-station detections in the TMDS are sorted out to determine associated orbits (~ 400 orbits), of which the similarities with their parent body, (3200) Phaethon, are attained successively by invoking the DSH criterion.
PS06-A015
Study of Meteor Spectra Recorded by the MIOS
Yi LI#+, Guozhu LI, Zhi WU
Chinese Academy of Sciences, China
Understanding the physical and chemical properties of meteoroids is helpful to reveal how the Solar System formed. A double-station optical video subsystem located in Ledong (18.4°N, 109°E) and Sanya (18.3N,109.6°E), China, which is a part of the Meteor and ionospheric Irregularity Observation System (MIOS), was developed recently. The MIOS is designed for investigating the properties of meteoroids entering the Earth’s atmosphere and how they affect the Earth’s space environment, for example the ionosphere. The observations of meteor spectra and common volume optical trails from the MIOS optical subsystem allow us to determine the emission from meteoroids and atmospheric species, and calculate the meteor velocity, trajectory and orbital parameters, and then we can distinguish the characteristics of populations of differently sized meteoroids and infer the relationship between meteoroids and their parent bodies. Numerous meteor spectra and their related trails were observed by the MIOS optical subsystem. Here we report preliminary results of the meteoroids observed in 2019 and 2020.
PS06-A018
Reflectance Spectral Variation of Hydrated and Dehydrated Carbonaceous Chondrites
Jinfei YU1,2+, Haibin ZHAO1#, Yunzhao WU3
1Chinese Academy of Sciences, China, 2University of Science and Technology of China, China, 3Purple Mountain Observatory, Chinese Academy of Sciences, China
Carbonaceous chondrites provide vital information on the early Solar System and their parent bodies’ history. We Investigated the 1-25 μm infrared spectral features of 17 carbonaceous chondrites with different petrologic properties and alteration degrees, and the spectral variation laws of the alteration and metamorphism were developed. With the increasing of aqueous alteration, the 3 μm band, diagnostic of OH-bearing minerals and water, and the 6 μm band, diagnostic of water molecules, both features increase in strength and band centers shift to the short-wavelength. With more alteration, a sharp absorption feature at 2.72μm shows in 3 μm band, which is similar to serpentine’s 3 μm absorption feature. Vibrational features of silicate minerals control the 10μm and 20μm regions. The 12.4 μm /11.4 μm reflectance ratio reduces and the reflectance peak in 9-14 μm region shifts to short-wavelength because of the conversion of anhydrous silicates to phyllosilicates. In the 15-25 μm region, with the thermal metamorphism processes, the single reflectance peak at 22.1 μm changes to two peaks at 19 μm and 25 μm, spectral curve becomes rough, which is likewise explained by the increase of anhydrous silicate with the increase of recrystallized olivine. These results can provide new constraints on C-complex asteroids’ volatile-rich compositions and their parent bodies’ thermal evolutionary history.
PS08-A006
Observing the Martian Atmosphere in the Ultraviolet: Science Updates from MAVEN IUVS
Daniel LO1#+, Sumedha GUPTA2, Roger YELLE3, Joseph EVANS4, Emmaris SOTO4, Matteo CRISMANI5, Sonal JAIN2, Justin DEIGHAN2, Nick SCHNEIDER2
1University of Michigan, United States, 2University of Colorado Boulder, United States, 3The University of Arizona, United States, 4Computational Physics, Inc., United States, 5California State University, United States
Since entering Martian orbit more than eight years ago (four Mars years), MAVEN’s Imaging Ultraviolet Spectrograph (IUVS) has been making observations of the Martian atmosphere in the far and mid ultraviolet (110--340 nm). Regular dayglow and occasional occultation observations have allowed us to map the composition and structure of the atmosphere, as well as to monitor how these vary diurnally, seasonally, interannually, and in response to solar events. The recent improvement in our characterization of the O I dayglow emission at 297 nm has extended our high-frequency monitoring of temperatures and wave activity from the original 130--170 km altitude down to 80 km. IUVS has also made the first direct detection and measurement of atomic carbon in the Martian atmosphere, and these measurements point to higher carbon abundances and escape rates than modeled. Since its discovery of a Mg+ layer in the atmosphere in 2015, IUVS has continued to map this meteoric ion layer in unprecedented detail. We found this layer to be persistent, but with significant variation with latitude, longitude, season and local time. We will be providing more details on these observations and recent scientific results.
PS08-A008
In-flight Calibration of the Magnetometer on the Mars Orbiter of Tianwen-1
Zhuxuan ZOU1+, Yuming WANG1#, Tielong ZHANG2,1, Guoqiang WANG3, Sudong XIAO3, Zonghao PAN1
1University of Science and Technology of China, China, 2Austrian Academy of Sciences, Austria, 3Harbin Institute of Technology, China
Mars Orbiter Magnetometer (MOMAG) is one of seven science payloads onboard Tianwen-1’s orbiter. Unlike most of the satellites, Tianwen-1’s orbiter is not magnetically cleaned, and the boom where placed the magnetometer’s sensors is not long enough. These pose many challenges to the magnetic field data processing. In this paper, we introduce the in-flight calibration process of the Tianwen-1/MOMAG. The magnetic interference from the spacecraft, including spacecraft generated dynamic field and slowly-changing offsets are cleaned in sequence. Then the calibrated magnetic field data are compared with the data from the Mars Atmosphere and Volatile EvolutioN (MAVEN). We find that some physical structures in the solar wind are consistent between the two data sets, and the distributions of the magnetic field strength in the solar wind are very similar. These results suggest that the in-flight calibration of the MOMAG is successful and the MOMAG provides reliable data for scientific research.
PS08-A012
Observation Plans for Mars and Its Moons by Using the MMX Infrared Spectrometer (MIRS)
Takahiro IWATA1#+, Hiromu NAKAGAWA2, Fuminori TSUCHIYA2, Shohei AOKI3, Moe MATSUOKA4, Hiroyuki KUROKAWA5, Tomoki NAKAMURA2, Maria Antonietta BARUCCI6, Jean-Michel REESS6, Pernelle BERNARDI6, Alain DORESSOUNDIRAM6, Sonia FORNASIER7, Michel LE DU8, Veronique PIOU8, Eric SAWYER8, Nathalie PONS8
1Japan Aerospace Exploration Agency, Japan, 2Tohoku University, Japan, 3The University of Tokyo, Japan, 4National Institute of Advanced Industrial Science and Technology, Japan, 5Tokyo Institute of Technology, Japan, 6Paris Observatory, France, 7Paris Diderot University, France, 8National Centre for Space Studies, France
MIRS (MMX InfraRed Spectrometer) is a push-broom imaging spectrometer in the wavelength range of 0.9 to 3.6 micrometers which is one of the instruments to be installed on the Martian Moons Exploration (MMX) spacecraft. It has a field-of-view (FOV) of 3.3 deg width with instantaneous-FOV (IFOV) of 0.35 mrad, which can be scanned by the inner along-track scan mirror in the range of ±20 deg. MIRS will observe absorptions of hydroxide or hydrated minerals on Phobos and Deimos. It will also monitor the Martian atmosphere with particular attention to spatial and temporal changes as clouds, dust and water vapor. We will report and discuss on the science targets, the observation plans, and the design results of instruments.
PS08-A023
Noachian Volcanism: Implication for Thermo-chemical Evolution of Early Mars
ALKA RANI1#, Yash SRIVASTAVA2+, Amit Basu SARBADHIKARI2
1NASA Marshall Space Flight Center, United States, 2Physical Research Laboratory, India
Geochemical information derived from the Martian orbiter missions provides insight into the various geologic processes. An earlier study based on orbiter geochemical data on Hesperian and Amazonian surfaces depicts that magmatism has chemically evolved. However, persistent weathering and resurfacing could have caused substantial geological changes that make a thorough examination of Noachian volcanism difficult. Therefore, understanding the thermo-chemical processes and evolution at the early stage of Mars is limited by the less constrained composition of the Noachian period. To understand the thermo-chemical evolution of the Martian interior at its early stage we investigate the Noachian-aged volcanic regions Arabia Terra, Solis (N1), and Argyre (N2). For the bulk chemical composition of the study areas, we use the latest geochemical provinces dataset of Mars, which is based on the latest elemental mass fraction maps of five-degree resolution by Nuclear Gamma-Ray Spectroscopy (GRS) data onboard Mars Odyssey 2001. Using pMELTS we derive formation pressure (P) and temperature (T) conditions and estimate the depth and mantle potential temperature. The average formation pressure of Arabia Terra shows a range from 1.3 to 1.7 GPa, whereas the average formation pressure of N1 and N2 ranges from 1.4 to 1.7 GPa with and without normalization of volatiles, overlapping with Arabia Terra. The calculated mantle potential temperature varies from 1310-1400 ᵒC for the studied Noachian regions. The degree of partial melt is ~8 % in Arabia Terra, ~12 % in N1, and ~11 % in N2. The melting depth is consistent in all three Noachian provinces, which is 130-150 km. Compared to the Hesperian and Amazonian magma formation conditions, the Noachian volcanic regions have relatively lower pressure and higher temperature of formation. This pioneering work of Noachian volcanics using an orbiter geochemical dataset suggests a cooling trend of the Martian mantle over time.
PS09-A007
Titan’s Surface Chemical Composition: What We Learned After 13 Years of Cassini Exploration
Anezina SOLOMONIDOU1#+, Alice LE GALL2, Athena COUSTENIS3,4, Paul HAYNE5
1Hellenic Space Center, Greece, 2Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS-UVSQ), France, 3Paris Observatory/ National Centre for Scientific Research, France, 4PSL Research University, France, 5University of Colorado Boulder, United States
The Cassini spacecraft spent 13 years in the Saturnian system and performed observations of Titan through 127 flybys, along with the in situ observations of the surface by Huygens. This led to the detailed investigation of Titan’s surface composition at both local and global scales. However, due to the complexity of Titan’s atmosphere and surface, the surface composition is only partially unveiled and is still considered to be one of Titan’s largest mysteries. Titan resembles Earth more than almost any other planetary body in the solar system, despite its frigid surface temperatures of -180 C (~93 K). Instead of silicate rocks, the crust is dominated by water ice. Sedimentary deposits in the form of hydrocarbon grains cover the top layer of the surface, while liquid hydrocarbons are found in the polar lakes. Titan’s active geology with its resurfacing processes creates topography where exposed materials from the underlying old crust along with new atmospheric sediments are present. After Cassini and Huygens with their several instruments investigated Titan for more than a decade one of the prevailing questions that still remains unanswered is whether and where water ice is exposed on the surface. Additionally, advanced knowledge with regards to the mixtures and the materials that create and cover the surface is yet to be gained from future missions and ground/space telescopes that would carry advanced technology. Here, we present an overview of what we have learned so far about the composition as well as its correlation and constraints with regards to Titan’s astrobiology.
PS11-A004
The Chirp Transform Spectrometer Flight Model on JUICE-SWI After NECP
Paul HARTOGH#+
Max Planck Institute for Solar System Research, Germany
The Chirp Transform Spectrometer (CTS) is the only heterodyne real-time spectrometer backend that was successfully flown on a deep space mission. A version with 180 MHz bandwidth and 4096 channels was operated in space without any problems between the Rosetta launch in 2004 and the end of the mission in 2016 as part of the MIRO (Microwave Instrument of the Rosetta Orbiter) instrument. A new version with 1 GHz bandwidth and 10000 spectral channels was developed for the JUICE-SWI instrument. It is based on the same basic principles, however is using a higher degree of digital technologies which results in higher flexibility (e.g. programmable input bandwidth, centre frequency, spectral resolution etc.), more than 6 times lower mass and about 4 times lower power consumption than the MIRO version. The FM and FS CTSs were completed mid 2020 and mid of 2022 respectively. This presentation focuses on the determined functional performance during the AIVT and NECP phases.
PS11-A007
Radiative Transfer (RT) and Inversion Codes for Characterizing Planetary Atmospheres: An Overview
Miriam RENGEL1#+, Jakob ADAMCZEWSKI1,2
1Max Planck Institute for Solar System Research, Germany, 2Georg-August-Universität Göttingen, Germany
The study of planetary atmospheres is crucial for understanding the origin, evolution, and processes that shape these celestial bodies. To interpret planetary spectra, it is necessary to have a detailed understanding of radiative transfer (RT) and its application through computational codes. With the advancements in observations, atmospheric modeling, and inference techniques, there has been a proliferation of RT and retrieval codes in planetary science. However, selecting the most suitable code for a given problem can be challenging. To address this, we provide a comprehensive mini-overview of the different RT and retrieval codes currently developed or available in the field of planetary atmospheres. This study serves as a valuable resource for the planetary science community by providing a clear and accessible list of codes, and it offers a useful reference for researchers and practitioners in selecting and applying RT and retrieval codes for planetary atmospheric studies.
PS11-A016
Microwave Spectrometry as a Tool to Target Io's Volcanic Plumes for Sample Collection
Neal TURNER1#+, William SMYTHE1, John PEARSON1, Paul HARTOGH2, Ryan OGLIORE3
1Jet Propulsion Laboratory, California Institute of Technology, United States, 2Max Planck Institute for Solar System Research, Germany, 3Washington University in St. Louis, United States
We model the microwave spectrum emitted from the plume of a major volcano on Jupiter's innermost Galilean moon, Io. The model covers hundreds of emission lines of the main gas component SO2, as well as lines of the lesser species SO, S, O, and NaCl. The thermal continuum emission from the pyroclastic silicate particles ejected with the gas is also included. We synthetically observe the resulting spectra using the parameters of the Submillimeter-Wave Instrument developed for the JUICE mission, and show that this instrument has sufficient sensitivity, speed, and angular and spectral resolution to map the plume's particle-rich central core during approach on a Jupiter-centered orbit suitable for collecting a sample from the plume.
PS13-A005
Numerical Simulation on the Evolution Process of Lunar Craters and Its Implication to the Dating of Lunar Craters
Junce ZHANG+, Caibo HU#
University of Chinese Academy of Sciences, China
The dating of lunar craters is an important scientific issue for exploring the evolution process of the moon. Dating work in the Earth sciences often relies on Isotopic dating of rock samples, but it is relatively difficult to obtain moon rock samples. Therefore, the current mainstream method of dating lunar craters mainly relies on the analysis of statistics of crater or boulder. For lunar craters, predecessors gave a classification basis based on the geometric characteristics of craters. In other words, there are some key geometric parameters corresponding to the type of craters on the lunar surface. Since there is no wind and water erosion on the lunar surface and the tectonic activity is weak, the landform evolution process of the craters on the lunar surface can be simulated by the linear diffusion equation. Taking simple craters on the lunar surface as an example, if we can find key geometric markers that are easy to measure directly and discover their quantitative relationship with time, we can find a new method for crater dating based on physical processes. In this study, the lunar surface diffusion equation is used to simulate the evolution of the lunar craters, and two dimensionless key geometric indicators of craters are selected for analysis. The quantitative relationship between the key geometric indicators and the age of craters is given. Finally, we propose a new method for preliminary quantitative dating of simple lunar craters based on physical processes and dimensionless parameters of lunar surface geometry.
PS13-A006
New Insights Into Subsurface Composition Variations of Mars South Polar Caps from Weak-reflection Zones in SHARAD Data
Peng FANG+, Jinhai ZHANG#
Chinese Academy of Sciences, China
The polar layered deposits (PLDs) of Mars preserve its Amazonian climate history which correlates to the orbital forcing. Characterization of stratigraphy and composition of the PLDs is critical for understanding the evolution of martian geology and climate. Radar sounding is a powerful tool for studying stratigraphy and composition the PLDs. Bright reflections represent the variations in the dielectric properties of subsurface materials, and these signals are widely used to inverse the structure and compositions of PLDs. However, geologic units or structures can also hide in weak reflection areas. Some of them have been proven to be CO2 ice, which is critical for understanding the paleoclimate of Mars. Some weak-reflection areas could also be artifacts caused by inferred interference or large topography variations. Few studies have focused on the differentiation of the artifacts and geological meaning signals. Here, using data from shallow Radar (SHARAD) onboard Mars Reconnaissance Orbiter, we propose a new method for distinguishing the weak-reflection signals in SHARAD radargram from data-processing artifacts. SHARAD original data processing consists of range compression and azimuth processing (i.e., synthetic aperture processing). The range compression produces the unfocused radargram that have enhanced resolution in the range direction and the azimuth processing generates focused radargram that has enhanced resolution both in along-track directions. Our method investigates the difference in waveform characteristics between unfocused and focused radargrams and then automatically detects the location of artifacts. We applied the method to SHARAD data across the south PLD and detected a series of shadow zones from abundant adjacent radargrams clustered in a small region near the south pole (86°~87°S). This quasi-linear array of connected shadow zones along a 50-kilometer-long meandering path is unique, and it may help to inform a paleogeology setting different from that of current Mars.
PS13-A014
Effect of Ice Depth and Abundance on the Evolution of Water Production Rate: Case Study of 67P/Churyumov-Gerasimenko
Xian SHI1#+, Xuanyu HU2, Yuri SKOROV3
1Shanghai Astronomical Observatory, China, 2Technische Universität Berlin, Germany, 3Max Planck Institute for Solar System Research, Germany
Water production rate is an important indicator of a comet’s physical nature. It sheds light on the composition and structure of the cometary nucleus, as well as the mechanism of its activity. As a comet approaches the Sun, its water production rate generally increases due to the intensification of insolation. However, the actual trend could vary between individual comets and between different orbits of the same comet. It is not entirely clear how this relation is dependent on various properties of the cometary nucleus. Measurements by ESA’s Rosetta spacecraft have provided a unique dataset for probing this problem. During its over two years’ rendezvous with the Jupiter Family Comet 67P/Churyumov-Gerasimenko, the water production was retrieved with high temporal resolution by multiple payloads on board. The resulting curve deviates from the commonly intuited inverse square law dependence on the heliocentric distance. In this study, we implement different thermo-physical models to simulate the evolution of water production rate of 67P. We demonstrate that the slope of the water production can be significantly influenced by the abundance and depth of the ice in the subsurface of the nucleus. Because both parameters can vary over time and across the nucleus, the global production of water vapour is unlikely a useful indicator for inferring the ice distribution of the comet. Moreover, the incorporation of diurnal water ice cycle in the model could notably alter the steepness of the water production curve, hence further complicates the scenario.
PS13-A015
A Complex Paleo-surface Revealed by the Yutu-2 Rover at the Lunar Farside
Jialong LAI1+, Yi XU2#, Ling ZHANG3
1Jiangxi University of Science and Technology, China, 2Macau University of Science and Technology, Macau, 3Sun Yat-sen University, China
The observable lunar surface is represented by a ubiquitous layer of fine-grained materials produced by billions of years of hypervelocity pounding of its crustal layer. These events are randomly distributed both in size and frequency, but the rate is thought to have declined significantly since the early formation stages of the Solar System. The data from the Radar (LPR) onboard Chang’e-4 (CE-4) rover (Yutu-2), which is exploring the Von Kármán Crater on the lunar farside, are helping to peel back the upper layer of finely comminuted materials, interpreted as a thick layer of ejecta from the neighboring Finsen crater, to reveal a complex paleo-surface morphology.
The LPR on the Yutu-2 rover of CE-4 mission has been surveying the lunar farside since the beginning of 2019. In this paper, we report the first 25 days of LPR data revealing a complex ancient lunar surface (paleo-surface), the elevation profile of which has been substantially modified after about 3.1 billion years of formation. During its 560 m journey, at a depth varying between 7 and 20 m, distinct variations in the returned signal characteristics reveal a possible 270 m ± 10 m buried crater with an estimated age of less than 100 m.y. A smooth surface depression might not be the remnant of a degraded crater but a related surface expression of the hidden structure. The geomorphology, the subsurface structure affected by the shock wave, the impact melt deposits, and the derived exposed time of the crater, are analyzed in the paper.
PS14-A008
Thermal Structure of the Upper Atmosphere in the Venusian Polar Region Simulated by a GCM with the Akatsuki Horizontal Wind Assimilation
Hiroki ANDO1#+, Yukiko FUJISAWA2, Norihiko SUGIMOTO2, Masahiro TAKAGI1, Yoshihisa MATSUDA3
1Kyoto Sangyo University, Japan, 2Keio University, Japan, 3Tokyo Gakugei University, Japan
The thermal structure of the upper atmosphere in the Venusian polar region is reproduced by the assimilation of horizontal winds in low- and mid-latitudes derived from the Akatsuki ultra-violet images. The obtained structure is well consistent with infrared and radio occultation measurements. In particular, the unique thermal structure in the Venusian polar vortex such as cold collar and warm polar region in our model is realistic: the level where the cold collar is located and the temperature difference between cold collar and warm polar region are consistent with the measurements. The reasons why the thermal structure of the upper atmosphere in the polar region is realistic are that the zonal wind distribution around the cloud top level and the structure of the residual mean meridional circulation induced by the thermal tides are improved. Our results also suggest that the thermal structure in the Venusian upper polar region is closely related to the atmospheric dynamics.
PS14-A012
Aerosol Properties in the Enormous Cloud Cover of Venus as Inferred from Improved IR2 Night-side Data
Takehiko SATOH1#+, Takao SATO2, Takeshi HORINOUCHI3, Takeshi IMAMURA4, George HASHIMOTO5
1Japan Aerospace Exploration Agency, Japan, 2Hokkaido Information University, Japan, 3Hokkaido University, Japan, 4The University of Tokyo, Japan, 5Okayama University, Japan
A very abrupt change of cloud opacity seen in the night-side disk of Venus, which we call Enormous Cloud Cover (ECC), was imaged by Akatsuki/IR2 and Venus Express/VIRTIS-M (Peralta et al., 2020). Similar phenomena were repeatedly recorded by the ground-based instruments since the beginning of the night-side observations (Allen and Crawford, 1984), suggesting this phenomenon is common in the Venus atmosphere and may include essential dynamical implication. We reported last year the analysis of six sets of Akatsuki/IR2 observations (cleaned with the RSS method of Satoh et al., 2021) as well as seven of VEx/VIRTIS observations (tabulated in Peralta et al., 2020). Darkening of normal region (just west of ECC, named Background Cloud or BC) to ECC in the two passbands (1.735 um and 2.26 um) was measured to characterize how aerosol size and number density changes from BC to ECC. To improve the photometric accuracy, needed especially for the extremely-low radiance region (ECC in 2.26-um), an alternative method to clean the IR2 1.735- and 2.26-um data has been developed. The new method uses an over-exposed (12.97 s) 2.02-um image, recorded between the 2.26- and 2.32-um images, to cancel the contamination from the dayside. Acquisition of the 2.02-um image was introduced when the observing program suite was updated in June 2016, therefore one of six IR2 data, 27 March 2016, is excluded from this new analysis. Once the IR2 images are cleaned, the radiance measurements in BC and ECC regions and characterization in the M3L coordinates (Satoh et al., 2021) are done just the same as before. We will discuss the improvement of the photometric accuracy, compare the obtained characteristics of the ECC for different observing times. Implication to the possible mechanism of this large-scale phenomenon will also be discussed.
PS16-A004
Tracing Seismic Phases Across the Moon
Ceri NUNN1#+, Benjamin FERNANDO2, Sharon KEDAR1, Mark PANNING1
1California Institute of Technology, United States, 2University of Oxford, United Kingdom
The Farside Seismic Suite is a planned seismic mission, which will land in Schrödinger Basin on the farside of the Moon. The mission, due to launch in 2025, is part of NASA’s Commercial Lunar Payload Services (CLPS) and will be the first seismic mission to the farside. From seismic experiments carried out during the Apollo missions, we know that the Moon is generates moonquakes and is frequently hit by meteoroids. In preparation for the FSS, we use AxiSEM3D, a full-waveform seismic propagation tool, to further explore how seismic waves propagate on the Moon. We compare our simulations to the impacts of the Apollo Saturn IV boosters and used Lunar Ascent Modules, which were deliberately crashed into the Moon. We simulate the artificial impacts because the locations, velocities, mass and trajectories of the impactors are known. Our analysis of the artificial impacts shows that seismic phases which have previously been labeled as shear arrivals are mislabeled (since there is no change to the polarization of the wave or the frequency of the arrivals). Instead, the observed increase in amplitude is likely to be somewhat random and may indicate energy arriving from an internal boundary. This absence of distinct shear arrivals is consistent with our simulations. In our simulations, which are modeled as pure explosions, no shear wave travels from the source. Secondly, our simulations show that direct arrivals are often too small to be observed, but later arrivals may be observed. This makes it difficult to label seismic phases observed in moonquakes, since later phases can be mislabeled as direct arrivals. By better understanding the propagation of seismic phases across the whole Moon, we will be in a better position to understand seismic data from future seismic missions, and explore the interior structure of the farside of the Moon.
PS16-A006
Dichotomy in Crustal Melting on Early Mars Inferred from Antipodal Effect
Lei ZHANG#+, Jinhai ZHANG, Ross MITCHELL
Chinese Academy of Sciences, China
The Martian crustal dichotomy (MCD) between the southern highlands and the northern lowlands is the planet’s most ancient crustal structure, but its origins and evolution remain enigmatic. Understanding of the MCD comes largely from present-day and shallow crustal constraints. Lacking ancient and deeper constraints, hypotheses for the origin of the MCD range from an early giant impact, partial melting from sustained mantle convection, or some combination. The antipodal effect is when a large impact has body and surface seismic waves that travel through and around the globe to meet at the planet’s antipode where the focused seismic energy induces crustal uplift and fracturing and subsequent volcanism. The antipodal effect has been investigated on the Moon, Mercury, and even Earth, but the antipodal pair of the Hellas Basin and the Alba Patera volcano of Mars has always been regarded as the exemplar among the terrestrial planets and moons. Here we investigate with seismological modeling the antipodal effect of Hellas-Alba. The volcano is latitudinally offset ~2°(~119 km) from the expected antipode, and we explore whether the MCD can explain this deflection. Variations across the MCD in topography, thickness, and composition have only minor effects. Simulations capable of sufficiently decelerating southern surface waves require the presence of 2%–5% more partial melt in the southern highlands. As the age of impact ca. 4 billion years ago post-dates the formation of the MCD, our partial melting results thus imply that, with or without an early giant impact, the MCD was modified by mantle convection to supply enough heat for crustal melts for several hundreds of millions of years after Mars formation.
PS16-A009
Focal Mechanism Inversion of the Largest Marsquake, S1222a
Huixing BI+, Daoyuan SUN, Mingwei DAI#
University of Science and Technology of China, China
S1222a, with a magnitude of Mw 4.7, is the largest marsquake detected by the InSight seismometer on Mars. Different from the previously recorded marsquakes and the meteorite impacts, this event is the first observed tectonic marsquake that has both clear body and surface waves. Furthermore, it originates away from the seismic active region, Cerberus Fossae graben. Thus, its seismogenic mechanism remains vague. Here, we use the Cut-And-Paste (CAP) method to invert the focal mechanism by fitting the direct P, S, and subsequent body waveforms filtered between 0.08 and 0.32 Hz. In the CAP method, different phases can be shifted separately to minimize the effects of the uncertainties of the velocity models. By including the later arrivals, such as depth phases and surface-reflected waves of PP, better constraints on the fault mechanism and the focal depth are achieved. Although S1222a has the waveform features of both high-frequency (HF) and low-frequency (LF) family events, our inversion prefers a deeper source depth, as suggested in the previous LF marsquake studies. Our inversion result shows that S1222a is a normal faulting event with a slight strike-slip component, suggesting an extensive seismotectonic regime around Apollinaris Mons or the dichotomy southeast to Elysium Planitia. We also apply this method to other LF events originated at Cerberus Fossae and obtain similar normal fault results as Brinkman et al. (2021). The extensional tectonic setting of S1222a, along with the normal faults at Cerberus Fossae may be indicative of possible volcanic activities within the deep crust or mantle of Mars.
PS17-A001
Research on the Activity of Comets 60P/Tsuchinshan 2 and 62P/Tsuchinshan 1
Jianchun SHI#+, Yuehua MA
Chinese Academy of Sciences, China
Comets 60P/Tsuchinshan 2 and 62P/Tsuchinshan 1 belong to JFCs. The activity of comets 60P/Tsuchinshan 2 and 62P/Tsuchinshan 1 is analysed by creating their Secular light curves (SLCs). We obtained the main activity parameters, the results show that both comets could be classified as middle-age comets in early apparitions, and their activity lasting for more than 300 d. The orbital changes (decrease of perihelion distance) of comets 60P/Tsuchinshan 2 and 62P/Tsuchinshan 1 in recent apparitions enhanced their activity. To study the physical properties and activity characteristic of 60P/Tsuchinshan during its 2018-2019 apparition, we observed 60P/Tsuchinshan with broadband B, V and R filters from November 2018 to March 2019 by using the 80 cm Yaoan High Precision Telescope at Yaoan Station of Purple Mountain Observatory, Chinese Academy of Sciences. Morphological analysis and photometric studies of 60P/Tsuchinshan were performed. The color indices, Af ρ values and dust production rates of 60P/Tsuchinshan were obtained. Compared to other Jupiter-family comets at similar heliocentric distances, we found that 60P/Tsuchinshan was a very active comet.
PS17-A005
A Note on the Yarkovsky Effect Detection with Ground-based Observations for Earth Quasi-satellites
Shoucun HU#+
Purple Mountain Observatory, Chinese Academy of Sciences, China
Earth quasi-satellites are objects in a specific type of co-orbital configuration (1:1 orbital resonance) with the Earth where the objects stay near the planet over many years. Due to the multiple-oppositions, they may be observed by ground-based facilities every year, making their observations more abundant then other general asteroids. We numerically find that their orbital drift under the influence of the Yarkovsky effect can be constrained due to the Earth quasi-satellite resonance, which may hinder the detection of the Yarkovsky effect from orbital fit using ground-based observations. We will quantitatively demonstrate this feature by performing a batch of orbit determination for several quasi-satellites and the corresponding detection SNRs are compared to those non-quasi-satellites that in the 1:1 orbital resonance with Earth.
PS17-A007
Regolith Properties of Large Main Belt Asteroid (704) Interamnia
Jiang HAOXUAN1#+, Jianghui JI1, Liang Liang YU2, Bin YANG3, Shoucun HU4, Yuhui ZHAO1
1Chinese Academy of Sciences, China, 2Macau University of Science and Technology, China, 3European Southern Observatory, Chile, 4Purple Mountain Observatory, Chinese Academy of Sciences, China
(704) Interamnia is one of the largest asteroids that locates in the outer main-belt region, which may contain a large amount of water ice underneath its surface. We observe this asteroid using 8.2 m Subaru telescope at mid-infrared wavebands, and utilize thermophysical model for realistic surface layers (RSTPM) to analyze mid-infrared data from Subaru along with those of IRAS, AKARI and WISE/NEOWISE. We optimize the method to convert the WISE magnitude to thermal infrared flux with temperature dependent color corrections, which can provide significant references for main-belt asteroids at a large heliocentric distance with low surface temperature. We derive best-fitting thermal parameters of Interamnia - a mean regolith grain size of 190-180+460 μm, with a roughness of 0.30-0.17+0.35 and RMS slope of 27−9+13 degrees, thereby producing thermal inertia ranging from 9 to 92 Jm−2s−1/2K−1 due to seasonal temperature variation. The geometric albedo and effective diameter are evaluated to be 0.0472 −0.0031+0.0033 and 339−11+12 km, respectively, being indicative of a bulk density of 1.86 ± 0.63 g/cm3. The low thermal inertia is consistent with typical B/C-type asteroids with D ≥ 100 km. The tiny regolith grain size suggests the presence of a fine regolith on the surface of Interamnia. Moreover, the seasonal and diurnal temperature distribution indicates that thermal features between southern and northern hemisphere appear to be very different. Finally, we present an estimation of volume fraction of water ice of 9% ∼ 66% from the published grain density and porosity of carbonaceous chondrites.
PS17-A010
Scenario-based Platform for Simulation and Inversion of Asteroid Light-curves
Kaiyu LEI1+, Xian SHI2, Fenzhi WU1, Xiao LIANG1, Yuehan AN1, Yanpeng WU1#, Wei ZHAO3, Peng LIU3, Yong YU2
1Beijing Institute of Spacecraft System Engineering, China, 2Shanghai Astronomical Observatory, China, 3Harbin Institute of Technology, China
An asteroid’s light-curve is the sequence of its apparent brightness over time. So far, most light-curve data is acquired with telescopic observations, while there is an increasing amount of data from spacecraft missions to asteroids. To fulfill the needs for the investigation of various types of light-curve data, we constructed a light-curve simulation and inversion platform based on realistic observing scenarios. By using modules and standard interfaces between them, the system covers the simulation, data reduction, and inversion of asteroid light-curves. We show with test cases, that this platform can be readily applied to further research on the asteroid light-curve inversion algorithm as well as the planning and operation of asteroid exploration missions. The platform is mainly composed of input data standardization, simulation, and inversion modules. Formatted files are used as interfaces between modules, making the system applicable to any target object and observation mode. The input data standardization module converts the shape and physical parameters of the target object, observation epochs, and observational geometries into standardized inputs for the other modules. In the simulation module, the standardized input data is rendered to obtain synthetic observations, which could be used for calculating the target’s apparent brightness and simulated light curves. The inversion module can use either the simulated light curves or observed light curve data for the inversion of physical parameters of the target, including its rotational properties and shape. To verify the feasibility and efficiency of the platform, we conducted a series of experiments with both ground-based and in-orbit asteroid light-curve observations. Results show that the simulated light-curves agree with observations. The inversion results obtained by using simulated light-curves are consistent with those obtained using actual observations. We expect to use this system for further studies of the light-curve inversion algorithm, and the planning and operation of future asteroid missions.
PS17-A030
Optical Landmark Searching and False-matches Elimination for Asteroid Pinpoint Landing
Yaqiong WANG#+, Huan XIE
Tongji University, China
Pinpoint landing on asteroids presents fundamental challenges for mission design and execution. Terrain relative navigation (TRN) is an efficient technology for precise landing for planetary exploration missions. Natural Feature Tracking (NFT) is a mapped landmarks-based optimal navigation method, which offer benefits in adaptive to feature appearance changes and present advantages when the spacecraft state is correctly estimate. As the spacecraft location and illumination conditions are not always precisely available to produce an optimally accurate map for feature matching and pose estimation, a robust landmark searching and false-matches elimination method is necessary. The proposed method is also based on the feature correlation between the 3D photometric data- based mapped landmark feature and the navigation image. Specially, we proposed a discriminative correlation filter (DCF) based landmark detection and matching method and a novel affine covariant feature false-matches elimination formulation. Firstly, based on specific image texture feature representations and circular matrix strategy, multi-channel DCF was employed to rapidly detect and match the landmarks features within current navigation camera image. Secondly, geometric topological relationships between the detected features were exploited to eliminate false matches. The false-matching features elimination was conducted by matching two sets of triplets under a global transformation model. A novel triples’ correspondence was proposed to describe the feature location correspondence, which improves the performance by exploiting local geometric structure of the feature. Furthermore, a novel latent variable model combining the feature frame and descriptor distinctness was employed, which significantly improves the convergence speed and matching performance in high-outlier-ratio cases. Images captured by the Touch and Go Camera System (TAGCAMS) of the Bennu asteroid were used to evaluate the performance of the proposed method. Qualitative and quantitative results illustrate the advancement of the proposed method in adapting to feature distortion and robustness to outliers.
PS17-A033
Thermal Properties of Small-sized Near-earth Asteroids from WISE/NEOWISE Observations
He HAOQING, Jianghui JI, Jiang HAOXUAN#+
Chinese Academy of Sciences, China
The number of near-Earth asteroids that have been discovered exceeds 31000 to date, among which the number of small-sized near-Earth objects with a diameter of less than 100 meters exceeds 18000. Besides, due to observational selection effects, the actual number of small-sized asteroids is higher than observed. These asteroids will pose a serious threat to the security of the Earth. However, because the lack of observational data, only a few asteroids' physical properties have been obtained. This work will improve the NEATM model by considering the influence of reflected light from the sun, and combine the observation data of WISE/NEOWISE to obtain the albedo, diameter and other thermophysical parameters of small-sized near-Earth asteroids around the earth, which can provide useful information to the near-Earth object defense missions.
PS17-A035
Orbit Determination and Gravity Field Recovery Around Asteroids Using Inter-satellite Range Data
Haohan LI1#+, Xiyun HOU1, Haowen CHENG2
1Nanjing University, China, 2National Astronomical Observatories, China
High precision orbit determination and gravity recovery have been an important part of asteroid exploration. High quality measurement data can improve the accuracy. Inter-satellite range link is a type of high quality relative measurement and has been widely used in orbit determination of Earth satellites, but not so widely used in missions around small bodies. In our study, we assume that high accuracy inter-satellite range data can be obtained around small bodies, between the chief spacecraft and some low-cost deputies, and study the orbit determination along with the recovery of important parameters such as the gravity coefficients of the asteroid and the coefficient of solar radiation pressure. By comparing the results of with or without the inter-satellite range data, we show that the accuracy can be improved.
PS17-A036
Stability of Asteroidal Ring Systems Under Close Encounters with Small Objects
Ren IKEYA#+, Naoyuki HIRATA, Keiji OHTSUKI
Kobe University, Japan
Recent stellar occultations revealed that not only giant planets but small objects can also possess ring systems. To date, rings are found around Centaurs (10199) Chariklo, a dwarf planet (136108) Haumea, and (50000) Quaoar. These discoveries imply that asteroidal ring systems may be common, particularly in the outer solar system. Ring systems are susceptible to various dynamical mechanisms that disrupt ring systems in a relatively short timescale. One of those disrupting mechanisms is close encounters with a perturbing object (perturber), since close encounters are a ubiquitous and fundamental evolutionary process in the solar system. We carried out a series of numerical calculations to investigate the stability of ring systems during close encounters with small objects. We found that even if the encounter takes place at the immediate vicinity of the ring, a perturber with mass ratio of ≥ 10-3 is required to cause a noticeable damage (the maximum change in eccentricity ~ 0.01). Unless the perturber is similar or greater in size than the ringed objects, a substantial disruption (the maximum change in eccentricity ≫ 0.01) would not occur. The change in eccentricity shows a good match with the analytical expression called “Exponential regime” given by Heggie & Rasio (1996) because the secular effect is not at work for encounters that bring devastating consequences on the ring system. The change in eccentricity is also in good accordance with the analytical expression derived from the impulse approximation (ZT04Imp) given by Zakamska & Tremaine (2004) although the conditions of the impulse approximation are not fully satisfied. We investigated the probability for severe close encounters by making use of the collision probability, and conclude that for both of Haumea and Chariklo such encounters are highly unlikely to take place even over the age of the solar system.
PS18-A002
Constraining the Warming Effect of High-altitude Water Ice Clouds on Early Mars in a 3D Moist General Circulation Model with a Simplified Cloud Microphysical Scheme
Feng DING1#+, Kaitlyn LOFTUS2, Robin WORDSWORTH2
1Peking University, China, 2Harvard University, United States
Geologic evidence suggests >102-yr-long lake-forming climates persisted on Mars 3-4 Ga. These early warm climates cannot be explained by the greenhouse effect of CO2 and water vapor alone. Recently, a warming mechanism for early Mars based on high-altitude water ice clouds was proposed, for situations where the surface water inventory is limited and far away from tropical regions. However, microphysical representations of clouds and precipitation remain one of the main uncertain factors for climate modeling of terrestrial planets, including present-day Earth. Here we use a three-dimensional moist general circulation model (3D moist GCM) with a simplified cloud microphysical scheme to constrain the potential warming effect of high-altitude water ice clouds in a physical parameter space. In our GCM, the cloud sink term is characterized by a constant timescale that can be interpreted as the conversion timescale from clouds to precipitation. Two distinct climate regimes emerge as the conversion timescale of cloud particles is varied in the GCM simulations, separated by the time scale of ~10 days when the global climate dramatically jumps from a cold state to a warm state. We show that this dramatic climate transition results from a strong positive feedback loop among surface evaporation, cloud mass, and the atmospheric greenhouse effect, and develop a toy model with such positive feedback to reproduce the GCM simulations. The behavior of dramatic climate transition is robust as we vary the surface ice distribution, surface CO2 pressure, and the obliquity of the planet in the GCM simulations. Our findings suggest that theoretical or experimental studies on cloud microphysics (e.g., cloud radii, conversion timescales) in ancient Mars' atmospheric conditions are crucial for quantifying the warming effect of high-level water ice clouds.
PS20-A007
NASA Moon Trek's Lunar Mission Planning Tools
Emily LAW1#+, Brian DAY2
1NASA Jet Propulsion Laboratory, United States, 2National Aeronautics and Space Administration, United States
NASA’s Moon Trek (https://trek.nasa.gov/moon/) is one of a growing number of interactive, browser-based, online portals for planetary data visualization and analysis produced by NASA’s Solar System Treks Project (SSTP). Moon Trek continues to be enhanced with new data and new capabilities enabling it to facilitate the planning and conducting of upcoming lunar missions by NASA, its commercial partners, and its international partners, as well as scientific research. Moon Trek’s innovation visualization and analysis tools are already being used by a growing number of missions and scientists around the world. The tools deployed including interactive 2D and 3D visualization, a DEM and Ortho Mosaic Image production pipeline as well as tools for distance measurement, elevation profile generation, solar altitude and azimuth calculation, 3D print file generation, virtual reality visualization generation, annotation, lighting analysis, electrostatic surface potential analysis, slope analysis, rock detection, crater detection, rockfall detection, profiling of raster data, line of sight calculation. This presentation will highlight Moon Trek’s tools for Lunar mission planning and demonstrate their use cases.
PS20-A015
A Low-cost Lander and Rover Investigation of the Reiner Gamma Lunar Magnetic Anomaly and Swirl: Lunar Vertex
David BLEWETT1#+, Jasper HALEKAS2, George HO3, Benjamin GREENHAGEN1, Brian ANDERSON1, Joshua CAHILL1, Edward CLOUTIS4, Brett DENEVI1, Shahab FATEMI5, Lon HOOD6, Jorg-Micha JAHN3, Rachel KLIMA1, Peter KOLLMANN1, Myriam LEMELIN7, Heather MEYER1, Leonardo REGOLI1, Sonia TIKOO8, Sarah VINES1, Dany WALLER1, Mark WIECZOREK9, Xiao-Duan ZOU10
1Johns Hopkins University Applied Physics Laboratory, United States, 2The University of Iowa, United States, 3Southwest Research Institute, United States, 4The University of Winnipeg, Canada, 5Umeå University, Sweden, 6The University of Arizona, United States, 7Université de Sherbrooke, Canada, 8Stanford University, United States, 9Institut de Physique du Globe de Paris, France, 10Planetary Science Institute, United States
Lunar Vertex is a mission at the intersection of planetary geoscience and space plasma physics. The first of NASA's Payloads and Research Investigations on the Surface of the Moon (PRISM) investigations, scheduled for delivery to the Reiner Gamma (RG) magnetic anomaly in 2024 aboard a commercial lunar lander, Lunar Vertex will unravel the nature of the RG anomaly, examine the enigmatic high-reflectance RG lunar swirl surface feature, and probe plasma interactions and the RG "mini-magnetosphere". Lunar Vertex includes three instruments on the lander: a suite of magnetometers (Vector Magnetometer – Lander, VML), a fixed-mounted set of cameras (Vertex Camera Array, VCA), and a low-energy ion and electron plasma analyzer (Magnetic Anomaly Plasma Spectrometer, MAPS). In addition, another suite of commercial fluxgate magnetometers (Vector Magnetometer – Rover, VMR) and a multispectral imager (Rover Multispectral Microscope; RMM) are carried on a small rover that will travel a distance of at least 500 m from the lander, providing additional multi-point measurements. The combination of magnetic field measurements taken during cruise and descent by VML and during surface operations by both VML and VMR will characterize the magnetic source and thus lend clues to its origin. The combined magnetic field and plasma measurements from VML and MAPS will provide direct observations of plasma populations reaching the lunar surface and the associated local magnetic field configuration. In addition, the regolith at locations along the rover's traverse within the RG swirl will be studied by RMM to reveal the surface texture, composition, and particle-size distribution, allowing hypotheses for swirl formation to be tested. VCA images will provide geologic context and yield data on the light-scattering properties of the surface. Correlations between magnetic-field data and soil properties determined by RMM and VCA will elucidate the role of solar-wind ion bombardment in the weathering of the surface.
PS20-A016
Lunar Mineralogical Prospecting Through Integrated Spectral Analysis
Rachel KLIMA#+, Angela DAPREMONT, Ellen LEASK
Johns Hopkins University Applied Physics Laboratory, United States
Danuri, Korea’s first mission to the Moon will provide valuable data for future lunar landed exploration. In support of that mission, we are working with existing data from Chandrayaan-1’s Moon Mineralogy Mapper (M3) and the Lunar Reconnaissance Orbiter Diviner Lunar Radiometer to provide mineral analyses to supplement Danuri’s measurements of elemental data through the Gamma Ray Spectrometer (KGRS) and imaging data collected by Lunar Terrain Imager. Our analysis focuses on characterizing the composition of minerals and potential resources at the sites targeted by Danuri. In advance of the return of science data from the mission, we have been working with existing Lunar Prospector Gamma Ray Spectrometer, M3, and Diviner data to develop our data processing pipeline, with the goal of being ready to combine derived mineralogical variability with the KGRS elemental data to create global low (1.5 km/pixel) and regional higher (250 m/pixel) resolution mineralogical, hydroxyl, and elemental maps. The data will be used for basic scientific analysis and to help assess the mineralogical composition and resource potential of candidate landing sites from orbit. Our specific scientific project is geared towards using these joint products to focus on investigation of orthopyroxene-dominated regions, exploring two specific questions: (1) What are the compositions of orthopyroxene-rich deposits exposed on the lunar surface and what is the range in their cooling rates? and (2) Is there a relationship between orthopyroxene modal abundance, composition, cooling rate, associated hydroxyl and specific types of terrain? Orthopyroxenes on the lunar surface could originate as cumulate layers of orthopyroxenite or norite in igneous intrusions, as crystallization of trapped melt entrained in the anorthosite floatation crust of the moon, or as orthopyroxenite in the lunar mantle.
PS20-A018
Advanced Lunar Imaging Spectrometer (ALIS) for Lunar Polar Exploration (LUPEX) Project
Kazuto SAIKI1#+, Yuusuke NAKAUCHI2, Noboru EBIZUKA3, Takayuki OKAMOTO3, Yoshiko OGAWA4, Masahiro KAYAMA5, Kohei KITAZATO4, Minoru SASAKI6, Hirohide DEMURA4, Hiroshi NAGAOKA3, Teruyuki HIRANO7, Takashi MIKOUCHI5, Yutaka YAMAGATA3, Yoshiaki ISHIHARA8, Ryusuke NISHITANI8, Hiroyasu MIZUNO8, Dai ASOH8
1Ritsumekan University, Japan, 2Ritsumeikan University, Japan, 3RIKEN, Japan, 4The University of Aizu, Japan, 5The University of Tokyo, Japan, 6Toyota Technological Institute, Japan, 7Astrobiology Center, Japan, 8Japan Aerospace Exploration Agency, Japan
Several studies that focus on searching for water ice resources in the lunar permanently shadowed regions (PSRs) reported positive results. However, the abundance, condensation mechanism, and lateral and vertical distribution of water at the PSRs remain unclear. To solve these problems, the Lunar Polar Exploration (LUPEX) project started by Indian Space Research Organization (ISRO) and Japan Aerospace Exploration Agency (JAXA) (Ohtake et al.,2021).We proposed a hyperspectral near-infrared camera named Advanced Lunar Imaging Spectrometer (ALIS) for LUPEX and it was selected as a candidate instrument for the rover in April 2020. ALIS can identify rock-forming minerals in the target area and confirm and quantify the existence of water ice. ALIS is composed of the following four blocks; ALIS-C (Camera): the main block, which contains the image sensor, spectroscopic optics, and electrical circuits, ALIS-M (Mirror): a movable mirror for shifting the field of view in elevation and azimuth directions, ALIS-L (Light): a light source that enables observation in PSRs, and ALIS-D (Diffuse reflector): a standard diffuse reflector to calibrate the spectral data of ALIS. There is an absorption band of water ice near 1500 nm, and we aim to use this absorption band to quantitatively detect trace ice with lower detection limit 0.5 wt% or better. We will also detect OH groups phases using the absorption band around 1400-1500nm and identify major rock-forming minerals using the absorption band around 1000nm. To improve the ice quantification accuracy of ALIS, we have developed a micro-ice production apparatus and are continuing the observation verification test by a BBM of ALIS. We estimate SNR value of the detector required to detect 0.5 wt% ice as to be ~220 for olivine and ~120 for plagioclase, respectively (Ogishima and Saiki, 2021). We have also started quantitative experiments using frosted highland regolith simulants.
PS20-A019
Testing and Characterisation of Front-end Electronics of Chaste Payload for Chandrayaan -3 Lander
Chandan KUMAR#+, Durga Prasad KARANAM, Sanjeev MISHRA, P. KALYAN REDDY, Janmejay KUMAR
Physical Research Laboratory, India
Chandra’s Surface Thermophysical Experiment (ChaSTE) aims to understand the thermophysical properties of the top 10 cm of the Lunar surface. The experiment has an electronics package, and a low thermal conductivity probe with Platinum RTD sensors mounted on it with a separation of 1cm. The Front-End electronics for the experiment has a constant low current excitation scheme with a low offset gain stage with a rail-to-rail amplifier. Each temperature sensor has an independent signal conditioning multiplexed onto a serial ADC for data handling and storage. The calibration and characterisation of the system (Sensor + Front End Electronics) were carried out using a custom-developed dry block calibration facility with an accuracy of better than 0.1K for the sensor and the integrated system. A Liquid Nitrogen bath was used to achieve an extremely lower temperature point. The calibration was done at three levels: sensor, probe and system. The electronics offset is first corrected at the sensor level by cross-referencing the sensor readings with a standard RTD Calibrator. After this, each RTD Sensor is calibrated over the entire range of temperatures. Since the sensors are mounted in the probe in this case, the effect of probe material, design and dimensions will also be accounted for. The same procedure is followed for instrument-level characterisation as well. We have also completed all the qualification tests per the project specification, and the package was cleared for flight. In addition, detail calibration and characterisation studies are also being carried out in an in-house developed Lunar simulation chamber. Using this setup, temperatures and thermophysical properties have been estimated for samples of various lunar analogous materials and compared with their known values for reference. Performance results, calibration and characterisation results will be discussed.
PS20-A021
Mineralogical and Morphological Investigation in and Around the Bowditch Crater of Lunar Farside: Insight to the Complex Volcanic Processes
Nabamita CHAUDHURI#+, Kusuma K.N., Aravind BHARATHVAJ
Pondicherry University, India
The mare units within the Bowditch crater (25.0° S, 103.1° E) and Lacus Solitudinis (27.8° S, 104.3° E) show an anomalous presence of basalts within the anorthosite-rich highlands of farside. We have analysed Moon Mineralogy Mapper (M3) to understand the nature of basalts available in this region. We have applied Integrated Band Depth (IBD) which targets the absorptions in visible near-infrared (VNIR) spectra diagnostic of lunar minerals. IBD colour composite was generated by assigning IBD1000, IBD2000 and IBD1250 to red, green and blue channels, respectively. The colour composite displays Bowditch and Lacus Solitudinis to be distinctly basaltic amidst the feldspathic highlands but in different hues and intensities, implying lithological variations. The Bowditch crater exhibits yellow colour, indicating the presence of pyroxene having absorptions at 1000 nm and 2000 nm. Comparatively, Lacus Solitudinis has a predominant presence of purple in the colour composite, generated due to the addition of red and blue, representing IBD1000 and IBD1250, indicating the presence of olivine along with pyroxene. The presence of various rilles and channels between the two units suggests that Lacus Solitudinis could be the source of basalts in Bowditch. A geomorphological study of the area using LROC-NAC data revealed the presence of many dark mantling deposits and fresh boulder patches along the rille shoulders, especially in the region near Bowditch. This indicates a relatively younger age of the region with a complex evolutionary history.
PS20-A029
Composition of Magma Composing Lunar Linear Gravity Anomalies: Implication to Magmatism During Ancient Lunar Expansion
Gaku NISHIYAMA1#+, Tomokatsu MOROTA1, Noriyuki NAMIKI2, Kazuki INOUE1, Seiji SUGITA1
1The University of Tokyo, Japan, 2National Astronomical Observatory of Japan, Japan
Several numerical simulations on the lunar interior evolution have proposed that the Moon has experienced an expansion stage in its history. After the lunar mantle overturn transported heat-producing elements, the radioactive heat warmed the lunar interior, causing a volumetric expansion. This phenomenon has been evidenced by linear gravity anomalies (LGAs) identified in high-resolution lunar gravity data acquired by NASA’s GRAIL mission. These long, narrow, and positive LGAs have been interpreted as ancient magmatic intrusions formed under extensional stress. Because the composition of magma reflects its origin and related processes, compositional analysis on LGAs may offer a new hint to decipher the ancient lunar thermomechanical state. In this study, we surveyed spectral and gravity datasets around 160-km-sized Rowland and Roche craters located on LGAs. Although LGAs have no prominent spectral feature right above them, LGAs weakened inside these craters suggest that ancient magma could have been excavated and distributed around them. Analyzing spectral absorptions with the Kaguya Multiband Imager (MI) and Chandrayaan-1Moon Mineralogy Mapper (M3) data, we first identified non-mare spots holding high-calcium pyroxene (HCP). Whether the discovered exposures originate from the LGA intrusion is next discussed in a comparison between data and impact simulation with iSALE hydrocode. Our spectral and gravity analysis indicates that Rowland crater did not excavate LGA material. No clear HCP exposures were found in its periphery, and the gravity drop inside Rowland did not lie within the range of our simulation. On the other hand, more than 30 HCP exposures were discovered around Roche. Together with gravity consistency between data and simulation, these exposures are likely to originate from the subsurface intrusion. Their low-Ti composition suggests that a mantle plume from overturned Ti-rich materials did not compositionally contribute to ancient LGAmagma but rather provided only heat to the LGA volcanism.
PS23-A005
Searching for Orbital Decay Candidates from Exoplanet Transit Databases
Li-Chin YEH#+, Ing-Guey JIANG
National Tsing Hua University, Taiwan
A huge number of mid-transit times from ExoClock and TESS projects are employed to investigate the possible non-linear transit timing variations of exoplanets by performing data-model fitting with both the fixed orbit and the orbital variation models. Several exoplanets in favor of orbital decay are found. Their tidally evolutionary orbits are also studied and presented.
PS23-A012
GTLS: A GPU Algorithm for Speeding up Periodic Transit Detection
Quanquan HU#+, Jian GE
Chinese Academy of Sciences, China
The Transit Least Squares (TLS) algorithm is a powerful tool for exoplanet transit searches in large datasets of photometric light curves. With its higher sensitivity and faster search speed than the traditional Box Least Squares (BLS) algorithm, TLS has become increasingly popular. However, it still takes a long time to run the TLS algorithm on the CPU to search for transit signals, which largely affects the search efficiency. An innovative GPU algorithm has been developed by us to speed up the TLS processing speed, allowing us to search more data for transit planet signals and improve search cadences for detecting weak transit signals or transit signals with shorter durations than those detected before. This GPU-based TLS algorithm is called GTLS, which has been tested and significantly improved the search speed using the TLS algorithm while still producing reliable results. This presentation reports this GTLS, its testing and early searching results from the TESS data.
PS23-A016
Forecasting Consecutive Transits of Circumbinary Planets in One Conjunction. Application to TOI-1338 b
Mutian WANG#+, Huigen LIU
Nanjing University, China
Current transiting circumbinary planets (CBPs) found by Kepler and TESS display significant transit time variations (TTVs) up to a few days. The dominant source of TTVs comes from the relative motion between the binary star and planet. In special cases, there will be multiple closely-spaced CBP transits over the same star present in one binary period, which we dub as ‘tight transits’. The frequency of tight transits significantly depends on the planet-to-stellar velocity ratio and the degree of co-planarity of the system. We derive analytical constraints to characterize the system architectures and binary and planetary phases when tight transits can occur. After refining the system parameters of TOI-1338 b using the newly-observed CBP transits during TESS Extended Mission, we found that the most recent tight transit of TOI-1338 b over the secondary star would be around February 23rd, and 27th 2024. Due to the large luminosity contrast between the primary and secondary star in the system, the apparent depth of the predicted tight transits will be around 200 ppm in the TESS band, but the visibility will be improved if redder photometry is employed. Finally, we develop an analytical approximation to explain the predicted timing and detectability’s dependence on the uncertainties of orbital parameters, which informs us how the detection of tight transits can yield a more precise three-dimensional architecture of TOI-1338 b system.
PS23-A025
Simultaneously Orbital Evolution and Gas Accretion of Giant Planets Embedded in the Protoplanetary Disk
Hui ZHANG1#+, David C. C. YEN2
1Shanghai Astronomical Observatory, China, 2Fu Jen Catholic University, China
Recent Transit and RV surveys have revealed that multiple-planet systems with more than one giant planet are common. And some giant planet pairs even show an orbit period ratio close to MMRs, which is an evidence of convergent orbital migration. How does the gas accretion process affect with the dynamical interaction between two gas-accreting planets? Will the convergent migration lead to a competition of gas? In this paper, we perform a series of hydrodynamic simulations that simultaneously model the orbital evolution and gas accretion of two giant planets embedded in the protoplanetary disk. Our results show that the convergent migration of two giant planets usually leads to a mass ratio (Mp_outer to Mp_inner) close to 1, which explains the similarity in mass of neighboring giant planets. And the final mass ratio significantly depends on the disk properties, e.g. density profile, viscosity, etc., and the orbital evolutions of the two interacting giants. This is also consistent to the large spread in the distribution (which is centered at 1) of the mass ratio of two adjacent giant planets.
PS23-A050
Prediction of the Free-floating Planet Event Rate for Microlensing Surveys
Qiyue QIAN1#+, Weicheng ZANG2, Hongjing YANG1, Shude MAO1
1Tsinghua University, China, 2Center for Astrophysics | Harvard & Smithsonian, United States
Free-floating planets (FFPs) are expected to be common in our Galaxy. The mass function and number density of the FFP population can provide constraints on planet formation theories. However, FFPs are difficult to detect because they are faint and unbound. Microlensing is currently the only method of detecting FFPs with wide mass and distance ranges. In this work, we will use simulations to predict the FFP event rate for future space microlensing surveys (e.g., ET, Roman). We will compare the expected detections and current observational results, discuss the potential reason for any gap between observations and our simulations, and outline optimizing strategies for future searches.
PS24-A001
North–south Plasma Asymmetry Across Mercury’s Near-tail Current Sheet
Jun ZHONG1#+, Lianghai XIE2, L. C. LEE3, James SLAVIN4, Jim RAINES4, Wing-Huen IP5, Yoshifumi SAITO6, Yong WEI2
1Institute of Geology and Geophysics, Chinese Academy of Sciences, China, 2Chinese Academy of Sciences, China, 3Academia Sinica, Taiwan, 4University of Michigan, United States, 5National Central University, Taiwan, 6Japan Aerospace Exploration Agency, Japan
Among the nearly 300 near-Mercury tail current sheet crossings performed by the MESSENGER spacecraft, we identified 34 traversals of an asymmetric current sheet, wherein the lobe densities on opposite sides differed by a factor of three or more. These asymmetric current sheet crossings primarily occur on the dawnside. Additionally, a global magnetohydrodynamic (MHD) simulation was found to be in excellent agreement with the observations. The results suggest that the north–south density asymmetry is caused by the solar wind entering via an upstream-connected window in one hemisphere. Moreover, the Parker spiral interplanetary magnetic field (IMF) controls the near-tail density asymmetries, whereas Mercury’s offset dipole magnetic field controls those in the mid- or distant-tail regions. We propose that hemispheric asymmetries in Mercury’s magnetospheric convection occur under strong IMF conditions.
PS24-A002
MESSENGER Observations of Standing Whistler Waves Upstream of Bow Shock of Mercury
Yang WANG1#+, Jun ZHONG2
1INSTITUTE OF GEOLOGY AND GEOPHYSICS, CHINESE ACADEMY OF SCIENCES (IGGCAS), China, 2Institute of Geology and Geophysics, Chinese Academy of Sciences, China
This paper reports on the standing whistler waves upstream of Mercury’s quasi-perpendicular bow shock. Using MESSENGER's magnetometer data, 36 wave events were identified during interplanetary coronal mass ejections (ICMEs). These elliptic or circular polarized waves were characterized by: (1) a constant phase with respect to the shock, (2) propagation along the normal direction to the shock surface, and (3) rapid damping over a few wave periods. We inferred the speed of Mercury’s bow shock as ~31 km/s and a shock width of 1.76 ion inertial length. These events were observed in 20% of the MESSENGER orbits during ICMEs. We conclude that standing whistler wave generations at Mercury are generic to ICME impacts and the low Alfvén Mach number (MA) collisionless shock, and are not affected by the absolute dimensions of its bow shock. Our results further support the theory that these waves are generated by the current in the shock.
PS24-A009
Learning from MESSENGER – Lessons for Tides Derivation with BepiColombo’s Laser Altimeter
Oliver STENZEL#+, Martin HILCHENBACH, Lukas MAES
Max Planck Institute for Solar System Research, Germany
The joint ESA-JAXA mission BepiColombo to Mercury [1] is set to arrive in orbit in late 2025. After commissioning the actual measurement campaigns of the BepiColombo Laser Altimeter BELA [2] will start during spring 2026. BELA will map the planet in high detail over the whole mission and will create a dataset the will allow us to estimate the Love number h2 from the cyclic deformation of the surface [3]. Measuring the Hermian surface between 2011 and 2015, NASA MESSENGER’s Laser Altimeter (MLA) [4] provides a multi year dataset from northern hemisphere, mostly that can be used to test data processing and tides derivation models. We will present our ongoing efforts to filter and select laser altimeter data with classical robust filtering and machine learning approaches [5], [6].
[1] J. Benkhoff et al., ‘BepiColombo—Comprehensive exploration of Mercury: Mission overview and science goals’, Planet. Space Sci., vol. 58, no. 1, pp. 2–20, Jan. 2010, doi: 10.1016/j.pss.2009.09.020.
[2] N. Thomas et al., ‘The BepiColombo Laser Altimeter’, Space Sci. Rev., vol. 217, no. 1, p. 25, Feb. 2021, doi: 10.1007/s11214-021-00794-y.
[3] R. N. Thor et al., ‘Prospects for measuring Mercury’s tidal Love number h2 with the BepiColombo Laser Altimeter’, Astron. Astrophys., vol. 633, p. A85, Jan. 2020, doi: 10.1051/0004-6361/201936517.
[4] J. F. Cavanaugh et al., ‘The Mercury Laser Altimeter Instrument for the MESSENGER Mission’, Space Sci. Rev., vol. 131, no. 1, pp. 451–479, Aug. 2007, doi: 10.1007/s11214-007-9273-4.
[5] O. J. Stenzel, I. Hall, and M. Hilchenbach, ‘Mercury Tide Parameter Estimation from Laser Altimeter Records’, presented at the 53rd LPSC, Mar. 2022. [6] O. J. Stenzel, M. Hilchenbach, and I. Hall, ‘Influence of Surface Properties from Laser Altimeter Data on Mercury Tide calculations’, 44th COSPAR Scientific Assembly, Athens, Jul. 2022, vol. 44, p. 470. https://ui.adsabs.harvard.edu/abs/2022cosp...44..470S.
PS24-A012
BepiColombo - Images from 3 Mercury Flybys
Johannes BENKHOFF1#, Joe ZENDER1, Go MURAKAMI2+
1European Space Agency, Netherlands, 2Japan Aerospace Exploration Agency, Japan
BepiColombo is a joint project between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA). The mission consists of two orbiters, the Mercury Planetary Orbiter (MPO) and the MercuryMagnetospheric Orbiter (MIO). Both spacecraft has been launched with an ARIANE V in October 2018 for an arrival at Mercury in late 2025. From dedicated orbits the two spacecraft will be studying the planet and its environment. On its route BepiColombo will perform flybys at Earth, Venus, and Mercury. Especially during these flybys but also during its cruise into the inner solar system some scientific and engineering operations have been scheduled. A short overview status of the mission and measurements taken by the three monitoring cameras during the first three Mercury flybys en route to Mercury will be given.
PS24-A013
Detection of Species in Mercury's Exosphere with the Visible Channels of PHEBUS During BepiColombo Flybys
Rozenn ROBIDEL1#+, Eric QUEMERAIS1, Jean-Yves CHAUFRAY2, Dimitra KOUTROUMPA1, Francois LEBLANC3, Aurélie REBERAC1
1Laboratoire Atmosphères, Milieux, Observations Spatiales, France, 2University Pierre et Marie Curie, France, 3National Centre for Scientific Research, France
BepiColombo, the ESA/JAXA joint mission has performed its first flyby of Mercury on October 1, 2021 and its second on June 23, 2022. PHEBUS (Probing of Hermean Exosphere By UltraViolet Spectroscopy) was able to observe during these flybys notably with its visible channels. The channel c404 is centered on 404 nm (K emission line), and the other one, c422, is centered on 422 nm (Ca emission line). During both flybys, the slit was removed and the acquisitions were made every 10s with an exposure time of 8s. The count rate as a function of time of both channels clearly indicates the observation geometry of the flybys, the transit in the shadow of Mercury in particular, and the maximum of the emission on the dawn side, after the closest approach. We present for the first time Mercury’s extended exosphere of Ca beyond ~12,000 km. We report a nightside/dayside asymmetry and show evidence for two different energetic populations of Ca. The distribution could be consistent with a two-step process: the first one ejects Ca-bearing molecules and the second one produces highly energetic Ca atoms. It is more difficult to state which species were detected by the other channel, c404. Its bandwidth is large enough to detect the emission lines of K, Mn, Al and even Ca+. However, K has not been observed by MESSENGER at this wavelength [1] while Mn has been observed only at the end of the MESSENGER mission, in the pre-dawn nightside region and between TAA of 0° and 70° [1], which does not correspond to the TAA of BepiColombo flybys. Finally, we make preliminary comparisons with the third Mercury’s Swing-By (June 2023). Reference: [1] Vervack et al., 2016
PS24-A014
3D Hall-MHD and MHD-EPIC Simulations of Mercury’s Dayside Reconnection-driven Dynamics
Changkun LI, Xianzhe JIA#+
University of Michigan, United States
Mercury possesses a miniature but dynamic magnetosphere driven primarily by the solar wind through magnetic reconnection. A prominent feature of the dayside magnetopause reconnection that has been frequently observed is flux transfer events (FTEs), which are thought to be an important player in driving the global dynamics at Mercury. In our initial work, we have used the BATSRUS Hall MHD model to conduct a series of global simulations to investigate the generation and characteristics of FTEs under different solar wind Alfvénic Mach numbers (MA) and IMF orientations. An automated algorithm was developed to consistently identify FTEs and extract their key properties from the simulations. In all simulations driven by steady upstream conditions, FTEs are formed quasi-periodically with recurrence time ranging from 2 to 9 seconds and the FTEs characteristics evolve in time as they interact with the surrounding plasma and magnetic field. The key properties of the simulated FTEs, including spatial size, traveling speed and core field strength, all exhibit notable dependence on the solar wind MA and IMF orientation, and the trends identified from the simulations are consistent with previous MESSENGER observations. Following the Hall-MHD simulations, we have employed the MHD with Embedded PIC (MHD-EPIC) model to perform the same sets of simulations to investigate the importance of kinetic effects in driving Mercury’s magnetopause reconnection. Our initial results suggest that the general properties of FTEs formed in MHD-EPIC follow very similar trends as in Hall-MHD simulations. In the MHD-EPIC runs, features like particle precipitation and localized diamagnetic depression are commonly found in the cusps as a result of dayside reconnection, which resemble the cusp filaments that have been observed by MESSENGER. We will present comparisons between the Hall-MHD and MHD-EPIC simulations and discuss the impact of kinetic physics on the formation and characteristics of FTEs.
ST01-A005
Suprathermal Electron Spectra at the Earth's Bow Shock
Xinnian GUO#+, Linghua WANG, Zixuan LIU, Liu YANG
Peking University, China
We present a comprehensive study of the in situ electron acceleration during 138 terrestrial bow shock crossings with good suprathermal electron observations by the Wind/3DP instrument from 1994 to 2004. For all 138 cases, we obtain the shock parameters from the nonlinear least-square shock fitting techniques and fit the observed omnidirectional electron flux JA (JD) at suprathermal energies at ~0.1-200 keV in the ambient solar wind (downstream) to a generalized triple-power-law energy function. According to the electron spectrum fitting results, we find that the downstream suprathermal electrons generally have three types of spectra: single-power-law spectrum, double-power-law spectrum, and triple-power-law spectrum. Furthermore, for significant shock electron acceleration (JD/JA > 1.5), JD/JA at ~0.4-10 keV tends to be correlated with the magnetic compression ratio rB.
ST01-A007
Research on Connection Arrangement Between Space Particle Radiation Detector and Its Front-end Readout Circuit
Xiangqian YU#+, Xin YANG, Linghua WANG, Weihong SHI, Yongfu WANG, Ao CHEN, Youlong WANG, Hongfei CHEN, Qiugang ZONG
Peking University, China
There are AC-coupled and DC-coupled configurations between the space particle radiation detector and its front-end readout circuit. This paper studies how these two configurations behave on the output amplitude, noise and signal-to-noise ratio. A theoretical model is derived to fully describe the transfer function from the input charge to the output voltage. The parameters of two typical Si detectors were took into the analysis. One is thick and small area while the other is thin and large area. The readout circuit consists of discrete components for convenience. Experiments were also done to verify the theoretical results. Generally, the gain of the preamplifier is larger for DC-coupled than AC -coupled. DC-coupled is suitable for the detector of smaller capacitance that is thick and small area. Furthermore, DC -coupled reduces the complexity of the circuit by fewer devices, so it benefits to multi-pixel detectors. While AC-coupled can reduce the input current of the readout circuit, thus reduces the pressure at the input. It is suitable to the detector of larger capacitance that is thin and large area. Furthermore, for PKU interplanetary ultralow-noise three-dimensional energetic particle instrument, we selected an appropriate coupled configurations to achieve the best performance. What’s more, the method proposed can also be applied to other space particle radiation detector system to select the appropriate coupled configurations to achieve their best performance.
ST01-A009
Range Expansion Technology for Space Particle Radiation Detector Readout Application Specific Integrated Circuits
Xiangqian YU#+, Youlong WANG, Linghua WANG, Weihong SHI, Yongfu WANG, Xin YANG, Ao CHEN, Qiugang ZONG
Peking University, China
Despite the widespread use of application specific integrated circuits (ASICs), their fixed measurable ranges are major limitations for some application. There are three method to solve this problem: paralleling the capacitor at the input of ASIC, decreasing the value of coupling capacitance between the detector and ASIC, employing a junction field-effect transistor source follower (JFET SF) as the first input stage of the ASIC. In this study, theoretical analysis, PSpice simulation analysis and experimental verification were carried out for the three method to find their best application situation. Furthermore, for ASIC (RENA-3) used in PKU interplanetary ultralow-noise three-dimensional energetic particle instrument, we selected an appropriate method to expand its energy detection range of proton channel. What’s more, the method proposed can also be applied to other space particle radiation detector system to expand its energy detection range for some situation.
ST01-A011
Multi-spacecraft Study of Solar Energetic Particles in Late October and Early November 2021
Ya-Hui YANG#+, Shao-Chun LU, Mao-Xiang WU, You-Min CHEN
National Central University, Taiwan
Two active regions (ARs) NOAA 12887 and 12891 are responsible for lots of solar flares in late October and early November 2021. In particular, the X1.0 flare erupted from AR 12887 on 2021 October 28 is relevant to the first ground-level enhancement (GLE) in solar cycle 25, and the M1.7 flare occurred at AR 12891 on 2021 November 2 is associated with the intense geomagnetic disturbances about two days later. Moreover, both flares are accompanied by EUV waves, CMEs, and solar radio bursts, indicating the possible role of CME-driven shocks or ICMEs on particle acceleration except flares. In this study, we attempt to characterize the solar energetic particles and their potential accelerators based on multi-spacecraft measurements in the interplanetary space (e.g., STEREO-A, WIND, PSP, or SolO) during October 28 - November 5, 2021. The shock analysis, including the estimations of shock parameters and propagation time, combined with the lightcurves and spectral evolutions of energetic particles are implemented to quantify the acceleration efficiency. The causes of flux enhancement in energetic particles other than shocks will be discussed as well.
ST01-A012
Solar Energetic Particles Produced During Two Fast Coronal Mass Ejections
Xiaolei LI#+, Jingnan GUO, Yuming WANG
University of Science and Technology of China, China
Two recent extremely fast coronal mass ejections (CMEs) are of particular interest. The first one originated from the southern hemisphere on 2021 October 28 and caused strong solar energetic particle (SEP) events over a wide longitude range from Earth, STEREO-A, to Mars. However, the other one, originating from the center of the Earthviewed solar disk 5 days later, left weak SEP signatures in the heliosphere. Based on the white-light images of the CMEs from the Solar and Heliospheric Observatory (SOHO) and the Ahead Solar Terrestrial Relations Observatory (STEREO-A), in combination with the observations of the corresponding solar flares, radio bursts, and in situ magnetic fields and particles, we try to analyze the series of solar eruptions during October 28–November 2 as well as their correspondences with the in situ features. It is found that the difference in SEP features between the two CMEs is mainly due to (1) the seed particles probably supplied by associated flares and (2) the magnetic connection influenced by the preceding solar wind speed.
ST01-A014
Solar Energetic Electron Events Observed by Solar Orbiter and Wind
Wenyan LI#+, Linghua WANG
Peking University, China
Solar energetic electron (SEE) events are the observed most common solar particle acceleration phenomenon in the interplanetary space. In order to improve the understanding of solar acceleration and interplanetary transport of solar energetic electrons, we will present a comprehensive study of SEE events observed both by SolO/EPD and Wind/3DP at different distances and longitudes. First, we will investigate the evolution of SEE events (e.g., the electron temporal profile, energy spectrum, pitch angle distributions, etc.) from SolO to Wind, to separate the solar acceleration information from the interplanetary transport effects. Secondly, we will locate the solar source of SEE events (e.g., flares, coronal jets, coronal mass ejections, etc.), using the remote-sensing measurements from SolO, SDO, and SOHO.
ST01-A016
Energetic Particle Instrument Developed by Peking University
Linghua WANG#+, Xiangqian YU, Weihong SHI, Yongfu WANG, Qiugang ZONG
Peking University, China
The PKU energetic particle instrument (EPI) is designed to make measurements of the three-dimensional distribution of suprathermal electrons and ions with good time, energy and angular resolutions in the interplanetary space, respectively, at energies from 20 keV to 1 MeV and from 20 keV to 11 MeV. The EPI consists of three sets of dual-double-ended foil/magnet semi-conductor telescopes, which cleanly separate electrons in the energy range of 20–400 keV and ions from 20 keV–6 MeV. The output of front detectors is taken in anti-coincidence with center detectors, to achieve the low background. The magnet telescopes also employ the well-established dE/dx vs. total energy approach to determine some ion species including 4He and 3He. The development of this instrument is funded by the national major scientific instrument development project from the National Natural Science Foundation of China (NSFC).
ST01-A017
The Formation of the Double-power-law Energy Spectra of Solar Energetic Particles
Feiyu YU1#+, Xiangliang KONG1, Fan GUO2, Yao CHEN1, Joseph GIACALONE3
1Shandong University, China, 2Los Alamos National Laboratory, United States, 3The University of Arizona, United States
Double-power-law energy spectra have been observed in many large solar energetic particle (SEP) events. Itis an important feature for understanding the acceleration and propagation of high-energy particles, but its formation mechanism remains unclear. We first perform numerical modeling of particle acceleration near the Sun at a CME-driven shock propagating through a streamer magnetic field by solving the Parker transport equation. We find that the energy spectra integrated over the whole simulation domain and in the streamer-nonstreamer transition region can be described by a double power law. We suggest that the double-power-law distribution may emerge as a result of the superposition of energetic particles from different source regions where the acceleration rates differ significantly. We also examine the double-power-law formation mechanism by analyzing the variation of particle energy spectra during propagation in the interplanetary space. Assuming that the SEP energy spectrum in the source region is a power-law with exponential rollover, we find that the superposition of energetic particles from different regions can produce a double power-law distribution during the interplanetary propagation. This further verifies that our proposed scenario of "mixing of SEPs from different source regions" can serve as a promising formation mechanism of the double-power-law feature in SEP energy spectra.
ST01-A019
Evolution of the Electron Acceleration Site in Solar Flares by Using Time-of-flight Analysis with Multiple Time-windows
Masaya YAKURA#+, Satoshi MASUDA
Nagoya University, Japan
It is well known that a large number of particles are accelerated during a solar flare. However, the particle acceleration process and where it happens has not been clearly revealed yet. The most outstanding study was done by Aschwanden et al. (1996) using the so-called Time-of-Flight (ToF) analysis technique. They concluded that the electron acceleration site is located slightly above the flare loop. Although the time evolution of the acceleration site during a flare is important for understanding the acceleration process, there are no studies on this topic. In this situation, we try to obtain new information on the evolution of the acceleration site using high-time resolution X-ray data derived from the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope. To investigate the time evolution of the acceleration site, ToF analysis was applied for each time-window including an outstanding spike that appeared in the hard X-ray light curve for flares occurring near the limb. We expect a time series of time-lags between different energy ranges can be derived. To confirm that this new analysis method effectively works for our purpose, we applied it to an M-class flare occurring on 25 June 2015. Then, we actually got a result suggesting that the ToF distance changed during the flare. This means that the acceleration site moved during the flare. Then, we extended this analysis method to several flares and derived some initial results. In this paper, we focus on the motion of the acceleration site during a flare and discuss about the physical interpretation of the results.
ST01-A024
Investigation of the Pitch Angle Distribution of the Accelerated Electrons Generating a Fast Propagation of a Microwave Source During a Solar Flare Observed with Nobeyama Radioheliograph
Keitaro MATSUMOTO1#+, Satoshi MASUDA1, Kazumasa IWAI1, Takafumi KANEKO2,3, Takashi MINOSHIMA4
1Nagoya University, Japan, 2Lockheed Martin Solar and Astrophysics Laboratory, United States, 3National Center for Atmospheric Research, United States, 4Japan Agency for Marine-Earth Science and Technology, Japan
The mechanism of particle acceleration during solar flares still remains controversial in solar physics. The pitch angle distribution of the accelerated electrons represents an important element in understanding this mechanism. Electrons that are accelerated to nearly relativistic speeds emit non-thermal microwaves. By using the Nobeyama Radioheliograph (NoRH), [Yokoyama+2002] estimated the pitch angle of accelerated electrons by analyzing the propagation velocity of non-thermal microwave sources. We found another flare event (an M-class flare on October 22, 2014) that showed similar observational features and evaluated the pitch angle of the accelerated electrons through multi-wavelength observations with NoRH, SDO, and Fermi, and computer simulations with the coronal magnetic field obtained from the NLFFF model. Finally, we concluded that electron injection took place toward one footpoint of the loop and also obtained results indicating a bouncing motion of the injected electrons along the magnetic loop (submitted to ApJL). This presentation will undertake a theoretical examination of the position and pitch angle distribution of injected electrons within the loop. By solving the Fokker-Plank equation, we will determine the phase space density with pitch angle and energy as independent variables in an 1D coordinate system along the magnetic loop, as determined by the NLFFF model. This will allow us to investigate the bouncing motion of electrons along the loop. The time-varying 17 GHz microwave emission along the loop will be determined through the solution of the Fokker-Plank equation. Our results indicate that electron injection occurred in the direction of the footpoint on one side. Our aim is to carry out an examination of the factors that influence the injection location and pitch angle distribution of accelerated electrons, using the simulations. We will then compare our results with available observations and discuss, in particular, the injection of accelerated electrons in this event.
ST01-A030
The Nonthermal Property of a Microflare
Zhentong LI#+, Yang SU
Chinese Academy of Sciences, China
In this poster, I will firstly show the energy release and plasma heating processes in the microflare first reported by Glesener et al. 2020, which shows the existence of a nonthermal component down to 6.5 keV in the X-ray spectrum. Using careful differential emission measure (DEM) analysis and the calculated multithermal X-ray component, we confirm the existence of the nonthermal component in the observed X-ray spectrum. Most importantly, we report the first imaging evidence for low-energy cutoff of energetic electrons in EM maps of >10 MK plasma, which first appeared as two coronal sources significantly above the chromospheric footpoints. This study reveals the important role of electron thermalization and low-energy cutoffs in the physical processes of microflares.
ST02-A006
Modeling of Thermospheric Atmospheric Density Based on MBiLE Model
Qian PAN1+, Chao XIONG1#, Zhou CHEN2, Peian WANG2, Chunyu XU1, Xu YANG3
1Wuhan University, China, 2Nanchang University, China, 3National University of Defense Technology, China
In this study, an ensemble learning algorithm based on a bidirectional long and short-term memory neural network (BiLSTM) and a multilayer perceptron (MLP) is used to build a model for prediction of the thermospheric mass density, MBiLE. We use the thermospheric density derived from the onboard accelerometer of Swarm C, which flies at about 450 km, for training and constructing the model. As expected, the MBiLE model predictions agree well with the Swarm C observations. We further checked the MBiLE model predictions at a wider altitude range, and compared the predictions with observations from the Swarm B (flying at about 500 km), CHAMP (flying at about 350 km), and GOCE satellite (flying at about 250 km). For example, for comparison with observations from GOCE, the prediction coefficient of determination of the model proved to be 0.96 with a root mean square error of 2.537×e-12. The comparison show that our MBiLE model has good robustness and generalization, and can achieve the prediction of thermospheric density covering a wide altitude range.
ST02-A021
Short-period Variation of Atmospheric Turbulence Activity in the MLT Region Over Langfang
Zewei WANG1+, Cunying XIAO1#, Xiong HU2, Junfeng YANG2, Xuan CHENG2, Qingchen XU2
1Beijing Normal University, China, 2Chinese Academy of Sciences, China
In this paper, we investigate the atmospheric turbulence activity in the MLT region and the relationship between atmospheric turbulence activity and atmospheric fluctuation activity. We use data from the Langfang MF radar (39.4◦N,116.7◦ E) from July 2019 to June 2020 and NRLMSIS 2.0 to calculate the parameters of atmospheric fluctuation activity and atmospheric turbulence energy dissipation rate. The atmospheric turbulent energy dissipation rate is modulated by different periods at different altitudes, with 12h and 24h period variations at all altitudes. At lower altitudes, there are more periodic variations; at higher altitudes, the 12h period is more pronounced than the 24h period, and the 8h period is more pronounced. A comparison of the atmospheric turbulent energy dissipation rate with atmospheric tidal wave activity shows that tidal waves have an effect on the atmospheric turbulent energy dissipation rate, and at higher altitudes, the effect of tidal waves on the turbulent energy dissipation rate is more evident. The pattern of variation in the atmospheric turbulent energy dissipation rate is similar to that of atmospheric gravity wave activity, with both turbulent energy dissipation rate and atmospheric gravity wave activity showing significant semi-annual variation.
ST02-A022
Ionospheric Disturbance Over Thailand and Nearby Regions in Southeast Asia During St. Patrick’s Day Geomagnetic Storm
Paparin JAMLONGKUL1#+, Suwicha WANNAWICHIAN1, Larry PAXTON2, Clayton CANTRALL2, Pornchai SUPNITHI3
1Chiang Mai University, Thailand, 2Johns Hopkins University Applied Physics Laboratory, United States, 3King Mongkut's Institute of Technology Ladkrabang, Thailand
This work focuses on the ionospheric disturbance in the Southeast Asia regions including Thailand, based on the thermospheric-ionospheric model and observations during the 17-18 March 2015 St. Patrick’s Day geomagnetic storm event. For thermospheric neutrals, the observational O/N2 column density ratio was measured by GUVI instrument on board TIMED spacecraft. The observed O/N2 compared to O/N2 computing from the WACCM-X SD model, based on high-latitude inputs including magnetospheric and geomagnetic states from two models, Heelis and Weimer. Global TEC (total electron content) data were obtained by the Madrigal GNSS database. Regional ionospheric data (TEC) were observed by several GNSS stations in the Asian sector including the KMIT Thailand station. The observed GNSS TEC is further compared to simulated TEC by the WACCM-X SD model. The preliminary comparisons show that the WACCM-X SD O/N2 from both Heelis and Weimer high-latitude drivers is consistently greater than GUVI O/N2 on global scales. Ionospheric results from TEC model-observation comparison show a slower response of the WACCM-X SD data. For regional ionospheric comparisons, WACCM-X SD TEC during the event has a significant variation in small response with KMIT TEC. The ionospheric response in low-latitude regions on localized scales is discussed. Moreover, the significant ionospheric response over Thailand could be interpreted in form of continuing irregularities among regions in Southeast Asia during the event in detail further.
ST02-A029
Midlatitude Ca+ Layers in the Mesosphere: Observations and Modeling
Jing JIAO#+
Chinese Academy of Sciences, China
Long-lived meteoric metal ions (1 day above 100 km altitude) converge to form dense ion layers, causing plasma irregularities in the ionosphere. Therefore, it is imperative to observe and understand the transport and formation of metallic ion layers. However, it is technically challenging to detect specific ion species, especially tracing ion transport over large vertical ranges and time durations. Numerous instruments detect electron density but cannot distinguish ion species. Rocket-borne mass spectrometers can distinguish ion species but provide only snapshots. Lidars provide a powerful tool to profile and trace metallic species over extended periods by exciting specific resonance fluorescence. The only metal ions detectable by ground-based lidars are Ca+, and previous lidar measurements reached ∼180 km. Our Ca+ lidar upgraded with narrowband lasers has achieved high detection sensitivity, enabling the Ca+ profiling up to 300 km. Such lidar measurements of dynamical Ca+ layers open a new window to study plasma irregularities.
ST02-A030
The COSPAR International Space Weather Action Teams (ISWAT) Initiative: Updates and Roadmap Progress
Mario BISI1#+, Masha M. KUZNETSOVA2, Anna BELEHAKI3, Sean BRUINSMA4, Shing FUNG2, Jingnan GUO5, Alexi GLOVER6, Manolis GEORGOULIS7, Insoo JUN8, Larisza KRISTA9, Ian MANN10, Arnaud MASSON11, Dibyendu NANDI12, Hermann OPGENOORTH13,14, Alexei PEVTSOV15, Christina PLAINAKI16, Martin REISS17, Camilla SCOLINI18, Manuela TEMMER19, Barbara THOMPSON2, Ilya USOSKIN20, Zhonghua YAO21, Yihua ZHENG2
1United Kingdom Research and Innovation - Science & Technology Facilities Council - RAL Space, United Kingdom, 2NASA Goddard Space Flight Center, United States, 3National Observatory of Athens, Greece, 4Centre National D'Etudes Spatiales, France, 5University of Science and Technology of China, China, 6European Space Agency, Germany, 7Academy of Athens, Greece, 8NASA Jet Propulsion Laboratory, United States, 9University of Colorado, Boulder, United States, 10University of Alberta, Canada, 11European Space Agency, Spain, 12Indian Institute of Science Education and Research-Kolkata, India, 13University of Umea, Sweden, 14University of Leicester, United Kingdom, 15National Solar Observatory, United States, 16Italian Space Agency, Italy, 17National Aeronautics and Space Administration, United States, 18University of New Hampshire, United States, 19University of Graz, Austria, 20University of Oulu, Finland, 21The University of Hong Kong, Hong Kong SAR
Modern society is becoming ever-more reliant on complex technologies and infrastructures that are highly susceptible to deleterious space-weather effects due to the temperamental nature of our dynamic Sun. Understanding and predicting space weather and its impact on society is acknowledged as a global challenge and was addressed by the initial COSPAR/ILWS Roadmap in 2015 (Schrijver et al., ASR, doi:10.1016/j.asr.2015.03.023, 2015). To better address many of the challenges identified in this initial roadmap, the COSPAR Panel on Space Weather (PSW) established the International Space Weather Action Teams (ISWAT) initiative. The ISWAT initiative is a bottom-up community-driven active network of teams, clustered by heliophysics domain, overarching activities, and key space-weather impact areas (see: https://iswat-cospar.org/ for further details). After several years of good progress across all areas of space-weather science and pathways to impacts (as well as with overarching activities in data utilisations, assessment, education and outreach, etc…), under the COSPAR PSW terms of reference to update the space-weather roadmap every ~five years, an updated roadmap was embarked upon led by both the ISWAT initiative and the PSW – but this time with a multi-paper approach across two Topical Issues in the COSPAR Advances in Space Research (ASR) journal. Here, we will provide an update on the COSPAR ISWAT initiative, how we work and how anyone in the wider community is welcome and can get involved, as well as an update on the updated roadmap progress to date.
ST02-A032
A Simulation Study on the Variation of Thermospheric O/N2 Ratio with Solar Activity
Xiaoli LUAN#+, Zhongli LI, Jiuhou LEI
University of Science and Technology of China, China
The ratio of number density of atomic oxygen (O) to that of molecular nitrogen (N2) in the thermosphere (O/N2) is an important parameter connecting the terrestrial thermosphere and daytime ionosphere. Previous studies demonstrated that the thermospheric O/N2 increases with increasing solar activity, and the changes in O/N2 with solar activity show a significant difference between winter and summer hemispheres. However, the root causes, which are responsible for the solar activity variation of O/N2, are not fully understood. In this study, we use the Thermosphere Ionosphere Electrodynamics General Circulation Model to investigate the contributions of various physical and chemical processes on the response of O/N2 to the solar radiation change. The controlled simulation results suggested that the chemical processes lead to the increase of thermospheric O/N2 over the globe with increasing solar activity. The increase of O/N2 with solar activity is dominated by the enrichment of O abundance and the loss of N2 abundance in the lower and upper thermosphere, respectively. Moreover, the simulation results suggested that a stronger hemispheric asymmetry in solstices is attributed to the stronger thermospheric circulation.
ST03-A003
Daytime Ionospheric Large-scale Plasma Density Depletion Structures Detected at Low Latitudes Under Relatively Quiet Geomagnetic Conditions
Wenjie SUN1#+, Guozhu LI1, Lianhuan HU1, Xiukuan ZHAO1, Haiyong XIE2, Yi LI1, Baiqi NING1
1Chinese Academy of Sciences, China, 2Institute of Geology and Geophysics, Chinese Academy of Sciences, China
The ionospheric electron density is expected to enhance after sunrise during geomagnetic quiet days. We present a case of anomalous large-scale ionospheric TEC depletion structure occurring in morning hours over low latitudes in China under relatively quiet geomagnetic conditions. The depletion structure, which occurred over a wide longitude range of more than 35°, developed toward higher latitudes at the speed of ~250 m/s. A statistical analysis using the data in 2018-2020 showed that such large-scale daytime TEC depletion mainly occurred in summer (mostly with Kp<3), with large intensity at ~16-30°N. The geomagnetic ΔH measurements at the stations near and away from the magnetic dip equator showed positive values, which rules out the possible contribution from a westward electric field. Observations from multiple ionosondes revealed a net downward plasma transport during the TEC depletion. An enhanced poleward neutral wind during the early morning hours, which may induce downward plasma transport, was surmised to play a leading role in driving the large-scale morning TEC depletion.
ST03-A007
Limb Sounders Tracking Perturbations from the Stratosphere to the Ionosphere Associated with Near-surface Sources
Xiangxiang YAN#+, Tao YU, Chunliang XIA
China University of Geosciences, China
Near-surface sources (earthquake/tsunami/volcano/typhoon) are known to induce atmospheric acoustic gravity waves (AGWs), which could propagate upwards through the lower atmosphere into the ionosphere. In this study, we employ three types of satellite data from two different limb sounders: the COSMIC radio occultation (RO) technique and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument to study the vertical coupling of near-surface sources-induced perturbations from the stratosphere to the ionosphere. For the 2011 Tohoku tsunami and 2015 Chile tsunami cases, all three types of datasets, including temperature profiles from 10 to 55 km and 16 to 107 km, and electron density profiles from 120 to 550 km, recognized perturbations of different scales at different heights after the tsunamis. The vertical scales identified by the wavelet analysis are from 1–2 km, 5–9 km, and 25–50 km in the stratosphere, mesosphere, and ionosphere, respectively. Another interesting point is that the temperature perturbations recorded by the SABER from 70–100 km altitude are found to arrive earlier than the tsunami wavefront. For the 2022 Tonga volcano case, the eruption induced strong GWs in the mesosphere are recorded by the SABER, these GWs have dominant vertical wavelengths of ~10-20 km. Not surprisingly, these disturbances also have profound effects on the ionosphere, one of which is the significant depletion of the ionosphere recorded by the RO data. This destructive depletion of the ionosphere had a marked effect on local short-wave communications. It is believed that these large near-surface sources disturbed the whole atmosphere space, and the scale of these signals gradually increases with the increase in altitude but decreases with time. The findings in this study suggest that the limb-sounding technique is a useful instrument in studying the vertical coupling of disturbances associated with near surface sources.
ST03-A014
Variation Trend of Shortwave Absorption in the Low-latitude Ionosphere
Xiaoli JIANG#+, Huimin LI, Lixin GUO
Xidian University, China
In this study, we propose a more comprehensive and valid ionospheric absorption model by incorporating an electron-collision model and the latest version of the geomagnetic model, based on the atmospheric model and the ionospheric model with reference to the Appleton-Hartree formulation. The absorption model is used to study the variation trend of the total absorption with frequency and elevation angle during two different times (day and night) in a low latitude ionosphere based on the ionospheric stratification theory, and some interesting phenomena are observed. Traveling ionospheric disturbances (TIDs) are commonly observed ionospheric disturbances, which influence the propagation process of radio waves. So based on the previous ionospheric model, the traveling ionospheric disturbances induced by the atmospheric gravity waves are modeled. Simultaneously, the variation trend of the absorption attenuation is analyzed under the existence of TID. Finally, in order to draw further conclusions, take the absorption with or without considering TID into comparison.
ST04-A008
Resonant Damping of Kink Modes in Solar Coronal Slabs
Hui YU1#+, Bo LI1, Shao-Xia CHEN1, Mingzhe GUO2
1Shandong University, China, 2Katholieke Universiteit Leuven, Belgium
We examine resonantly damped kink modes in straight coronal slabs, paying special attention to the effects of the formulation for the transverse density distribution (“profile”). We work in the framework of pressure-less, gravity-free, resistive magnetohydrodynamics, and we adopt the dissipative-eigenmode perspective. The density profile is restricted to be one dimensional, but nonetheless allowed to take a generic form characterized by a continuous transition layer connecting a uniform interior to a uniform exterior. A dispersion relation (DR) is derived in the thin-boundary limit, yielding analytical expressions for the eigenfrequencies that generalize known results in various aspects. We find that the analytical rather than the numerical solutions to the thin-boundary DR serve better the purpose for validating our self-consistent resistive solutions. More importantly, the eigenfrequencies are found to be sensitive to profile specifications, the ratio of the imaginary to the real part readily varying by a factor of two when one profile is used in place of another. Our eigenmode computations are also examined in the context of impulsively excited kink waves, suggesting the importance of resonant absorption for sufficiently oblique components when the spatial scale of the exciter is comparable to the slab half-width.
ST04-A010
A Neural Network Approach to Understanding the Flow Dynamics Photospheric Flux Emergence
Matthew LENNARD1#, Benoit TREMBLAY2, Andrés ASENSIO RAMOS3, Hideyuki HOTTA4, Haruhia IIJIMA4, Sung-Hong PARK4, Viktor FEDUN5+, Gary VERTH5, Suzana DE SOUZA E ALMEIDA SILVA5
1University of Sheffield, United Kingdom, 2National Solar Observatory, United States, 3Instituto de Astrofisica de Canarias, Spain, 4Nagoya University, Japan, 5The University of Sheffield, United Kingdom
Advances in modelling magnetic flux inside the Sun’s convective region (see e.g. Hotta & Iijima, 2020; Chen et al, 2021) have provided high resolution data, which allow the study of photospheric flows and their relationship with intense emerging magnetic flux. In the literature, photospheric velocity fields have been mostly inferred by employing optical feature tracking with e.g., local correlation tracking (LCT). This is useful for understanding flows mainly on supergranular scales, however results are influenced easily by noise, creating holes and large errors when performing tracking at smaller scales. Neural networks (NNs) such as DeepVel (DV) (see Asensio Ramos et al., 2017) have been developed for deriving transverse flows from time-consecutive images of the photosphere by learning from numerical simulations. DV works for photospheric observations at a wide range of spatial resolutions and cadences, only limited by the training data. The combination of speed and accuracy of recovering these data from a trained version of DV are an improvement on the often-used Fourier LCT (FLCT) algorithm. These highly detailed velocity fields can be used to analyse plasma flow organisation and subsurface flows using methodologies such as the Finite-Time Lyapunov Exponent (FTLE). In this work, we have tested and compared the ability of both FLCT and DV to recover velocities from the R2D2 simulation. We have found notable features within the FTLE field, which may be used to forecast flux emergence hours before there are any visible indicators, such as the appearance of pores or sunspots.
ST04-A011
Mode Conversion Near the Magnetic Null Point: Current Sheet Formation
Zhang CHAO#+, Mingzhe GUO, Zhenghua HUANG, Bo LI, Lidong XIA, Hui FU, Hengyuan WEI, Deng KAIWEN, Li HAIYI
Shandong University, China
Magnetoacoustic waves are thought to be ubiquitous in the solar atmosphere, in which fast waves are physically trapped by the null point, causing the collapse of the null points. Therefore, fast waves could be responsible to the sympathetic explosion that is energy release triggered by a remote activity. In this study, based on an initial state of the potential field with magnetic null point and Athena++ code, we perform a two-dimensional numerical experiment to study the dynamics when the slow wave propagating through the magnetic null point. We found that mode conversion occurs in the vicinity of the sound speed equal to the Alfvén speed and fast waves are generated and propagate towards magnetic nulls. Consequently, part of the energy of the fast waves is trapped by the magnetic null point, causing the collapse of the magnetic null point and formation of current sheet. As the current sheet becomes thinner, the plasmoid instability is triggered and the reconnection rate increases. The simulations help us better understand the relationship between MHD waves and magnetic spots, also provide an scenario sympathetic eruption.
ST04-A014
Vorticity and Energy Transport in Photospheric Vortex Tubes
Suzana DE SOUZA E ALMEIDA SILVA1#+, Istvan BALLAI1, Erico L. REMPEL2, Sergiy SHELYAG3, Luiz Augusto CAMARGO ARANHA SCHIAVO4, Viktor FEDUN1
1The University of Sheffield, United Kingdom, 2Instituto Tecnológico de Aeronáutica, Brazil, 3Deakin University, Australia, 4University of Manchester, United Kingdom
In this study, we use the instantaneous vorticity deviation method to detect three-dimensional vortex tubes in a solar plage simulation. Our analysis suggests that the vorticity in the vortex tubes is mainly created by the misalignment of magnetic pressure and density gradients, indicating the importance of the magnetic field for the vortex evolution. The vortices also present prevailing magnetic energy, transported up and downwards within each tube, creating a circulation of electromagnetic energy across the lower solar atmosphere. The vertical component of Poynting flux is mainly generated by horizontal motions leading to a nonuniform and time-dependent distribution of energy flux. Thereby, collectively, the vortices create a net upward propagating energy flux of 1.38x108 ergs/(s cm 2), enough to explain chromospheric temperatures. Moreover, our findings indicate that the dynamics imposed by vortex motion can help enhance energy transport and heating mechanisms such as viscosity and current dissipation.
ST05-A002
Identification and Velocity Characterisation of a Heliospheric Transient Using Interplanetary Scintillation with the Murchison Widefield Array
Angelica WASZEWSKI1#+, John MORGAN2, Rajan CHHETRI3, Mark CHEUNG3, Ramesh BHAT1, Melanie JOHNSTON-HOLLITT1
1Curtin University, Australia, 2CSIRO Space and Astronomy, Australia, 3CSIRO - Space and Astronomy, Australia
Interplanetary scintillation (IPS) is a phenomenon which causes sufficiently small radio sources to “twinkle” in the solar wind. IPS is a fantastic space weather tool as it is able to measure the solar wind density along any lines of sight an arbitrary distance from the Sun, giving it unlimited reign to probe the entire heliosphere. In the last few years, we have breathed new life into this old technique, adapting it for modern low-frequency instruments such as the Murchison Widefield Array (MWA). The key advance we have made is to exploit the enormous field of view of the MWA. This allows us to monitor all IPS sources across a field of view 30 degrees across, leading to an unprecedented density of measurements of around 250 sources per 900 sq deg. These capabilities have already been exploited to launch the IPS space weather era of the MWA, with the first detection and characterisation of a coronal mass ejection. Alongside this initial space weather work, a recently completed survey of IPS sources in the sky above the MWA has become the basis of this work. We have conducted a blind search of 49 days of MWA IPS observations from mid-2019, with overlapping daily observations approximately East and South-East of the Sun at an elongation of 30 degrees. This search has revealed several interesting transient features characterised by higher than usual scintillation levels (in spite of the observations being taken at solar minimum). One solar wind enhancement is captured in two observations several hours apart, allowing the plane-of-sky velocity to be inferred. After close inspection of solar event catalogues and white-light coronagraph images, it was determined that this heliospheric transient is not an effect caused by a coronal mass ejection, but has a most likely source of a co-rotating interaction region.
ST05-A003
UCSD Iterative 3-D Analyses: Forecast of the March 10, 2022, CME Using ISEE IPS Data
Bernard JACKSON1#+, Munetoshi TOKUMARU2, Kazumasa IWAI2, Ken'ichi FUJIKI2, Matthew BRACAMONTES1, Andrew BUFFINGTON1, Mario BISI3, Go MURAKAMI4, Daniel HEYNER5, Beatriz SANCHEZ-CANO6, Mathias ROJO7, Sae AIZAWA8, Nicolas ANDRE9, Alain BARTHE7, Emmanuel PENOU10, Andrey FEDOROV9, Jean-André SAUVAUD10, Shoichiro YOKOTA11, Yoshifumi SAITO4
1University of California San Diego, United States, 2Nagoya University, Japan, 3United Kingdom Research and Innovation - Science & Technology Facilities Council - RAL Space, United Kingdom, 4Japan Aerospace Exploration Agency, Japan, 5Institute for Geophysics and Extraterrestrial Physics, Germany, 6University of Leicester, United Kingdom, 7Institute for Research in Astrophysics and Planetology, France, 8Laboratoire de Physique des Plasmas, France, Metropolitan, 9University of Toulouse, France, 10Institute for Research in Astrophysics and Planetology (IRAP), National Center for Scientific Research (CNRS) - University of Toulouse (UPS) - National Center for Space Studies (CNES), France, 11Osaka University, Japan
Remotely-sensed interplanetary scintillation (IPS) from the Institute for Space-Earth Environmental Research (ISEE), Japan, allows a determination of solar wind parameters throughout the inner heliosphere. We show the 3-D time-dependent analysis technique developed for these data sets that is used to forecast plasma velocity, density, and component magnetic fields at Earth, as well at the other inner heliospheric planets and spacecraft. One excellent March 10, 2022, Coronal Mass Ejection (CME) example is shown here that was viewed not only in the ISEE IPS analyses, but also by the spacecraft near Earth that could measure the CME 1 AU arrival. Solar Orbiter that was nearly aligned along the Earth radial at 0.45 AU also measured the CME in plasma density, velocity, and magnetic field. BepiColombo at 0.44 AU, aligned with the STEREO A spacecraft, also measured this CME passage in the European Space Agency Mercury Planetary Orbiter MAG instrument. In addition, the Japan Aerospace Exploration Agency BepiColombo Mio Mercury Plasma Particle Experiment/Mercury Electron Analyzer recorded an enhancement of electrons and the Solar Particle Monitor on Mio measured a Forbush decrease from below the protective Sun-shroud covering that timed the passage of this event. This presentation summarizes the analysis from the ISEE, Japan real-time data for the CME forecast, and provides a synopsis of the results, and confirmation of the CME morphology, from the different data sets available after the CME arrival.
ST05-A004
Solar Wind 3-D Reconstructions Using STEREO and SMEI Thomson Scattering Data: Attempts to Define Mesoscale Structures Near Earth
Bernard JACKSON1#+, Matthew BRACAMONTES1, Andrew BUFFINGTON1, Jackie DAVIES2, David BARNES2, Munetoshi TOKUMARU3
1University of California San Diego, United States, 2United Kingdom Research and Innovation, United Kingdom, 3Nagoya University, Japan
We now use the University of California, San Diego (UCSD) iterative tomography analyses to provide high resolution Solar Mass Ejection Imager (SMEI) and STEREO Heliospheric Imager (HI) 3-D reconstructed plasma density volumes of the inner heliosphere. These analyses also include Earth-based interplanetary scintillation (IPS) instrumentation data from the Institute for Space-Earth Environmental Research (ISEE), Japan, to help provide more refined high-resolution plasma densities and velocities. Because we use both SMEI and STEREO HI data with a long temporal base removed, we can study the morphology of Stream Interaction Regions (SIRs) as well as that of Interplanetary Coronal Mass Ejections (ICMEs). Here we present the densities at one-hour cadences, and with comparable few-degree, latitude, longitude, and solar distance resolutions that are well within mesoscale sizes that take less than a half a day to pass over an observer. The analyses show that the structures that propagate past the spacecraft and near Earth are often very “corrugated” and “patchy” at these high resolutions. These 3-D reconstructions have the ability to explain some of the differences in multipoint in-situ observations from spacecraft near Earth and further afield (e.g., STEREO-A). Here we address the amount to which these structures continue to evolve as they move outward and interact with each other. Patchy structures present difficulties for most forecasting techniques, which assume smooth structures that propagate outward from the solar surface, unlike those revealed by the tomography. Our analyses prototype the forecasting capability needed for future similar spaceborne heliospheric imager instruments such as the NASA Small Explorer PUNCH, UCSD’s All Sky Heliospheric Imager (ASHI), or the Vigil heliospheric imager.
ST05-A006
ASHI: An All Sky Heliospheric Imager Designed to Maximize the Scientific Return from Solar Wind Structures Passing Earth
Matthew BRACAMONTES1#+, Bernard JACKSON1, Stephen KAHLER2, Mario BISI3, Andrew BUFFINGTON1, Stuart VOLKOW1, Ed STEPHAN4, Philippe LEBLANC4, Ron QUILLIN4
1University of California San Diego, United States, 2Air Force Research Laboratory, United States, 3United Kingdom Research and Innovation - Science & Technology Facilities Council - RAL Space, United Kingdom, 4Stephan Design-Build, United States
We have conceived, designed, and have evaluated components for an All-Sky Heliospheric Imager (ASHI), suitable for flight on future space missions. ASHI was tested last summer on a NASA-sponsored topside balloon flight; this presentation highlights the images taken by this instrument on its successful overnight flight. A successful space-borne flight will have an order of magnitude more throughput than SMEI or the STEREO HI instrumentation, and thus provide a far better science and forecast capability than possible before. ASHI is currently manifested on a DoD Space Test Program satellite. As a simple, light weight (~6kg), and relatively inexpensive instrument, the ASHI system has the principal objective of providing a minute-by-minute and day-by-day near real time acquisition of precision Thomson-scattering photometric maps of the inner heliosphere. The instrument's unique optical system is designed to view a hemisphere of sky starting a few degrees from the Sun. A key photometric specification for ASHI is 0.1% differential photometry in one-degree sky bins at 90 degrees elongation that enables the three dimensional (3-D) reconstruction of heliospheric density extending outward from near the Sun. The ASHI system, unlike coronagraphs or planned heliospheric imagers, is intended to maximize the scientific return of heliospheric structures that pass the spacecraft. This will allow density structure measured in-situ to be extended outward into the surrounding plasma close to Earth. This is especially important where recent high-resolution Solar Mass Ejection Imager (SMEI) and STEREO Heliospheric Imager (HI) analyses have shown CMEs have an evolving and “corrugated” structure when they pass nearby.
ST05-A010
Next Generation Interplanetary Scintillation Observation for Better Three-dimensional Reconstruction of the Heliosphere
Kazumasa IWAI#+, Munetoshi TOKUMARU, Ken'ichi FUJIKI
Nagoya University, Japan
Interplanetary scintillation (IPS) is a radio scattering phenomenon caused by the turbulences in the solar wind. The IPS observation using ground-based radio telescopes has been an important technique to investigate the three-dimensional (3D) structure of the solar wind in the heliosphere. The IPS observation has also been used for space weather research and operations. Institute for Space–Earth Environmental Research (ISEE), Nagoya University have observed IPS to derive the solar wind velocity and density irregularities for several decades using large radio telescopes at 327 MHz. The 3D structure of the heliosphere has been reconstructed by the tomography technique. The derived solar wind characteristics are also included in the three-dimensional (3D) global magnetohydrodynamic (MHD) simulation of the heliosphere to forecast the arrival of the solar wind and coronal mass ejections (CMEs). The recent space weather requires more accurate prediction of the solar wind that requires more IPS observations. Now, a new project to develop the next generation IPS observation system is in progress. We consider a new ground-based radio observation system at 327 MHz by constructing a 2D flat phased-array antenna system consisting of multiple dipole antennas, and installing digital beam forming devices. The multidirectional simultaneous IPS observation using this system enables the solar wind observation 10 times as much as the conventional radio instruments have been done. This project will greatly contribute to understanding the solar wind and improving the accuracy of space weather forecasts. We have developed a prototype of the digital phased array instrument. This instrument has 8 analog-digital converters (ADCs), field-programmable gate array (FPGA), and 10-Gbit Ethernet output. This system enables us to measure 8 beams simultaneously by processing 8 types of different beamforming in parallel. A small scall array system is under construction as a phase-I project.
ST05-A011
Three-dimensional Structure of the Ionospheric Disturbances Over Japan Following the Eruption of Hunga Tonga-Hunga Ha'apai on 15 January 2022
Susumu SAITO1#+, Taisei NOZAKI2, Mamoru YAMAMOTO2, Nicholas SSESSANGA3
1National Institute of Maritime, Port and Aviation Technology, Japan, 2Kyoto University, Japan, 34D-Space, Norway
After the intense eruption of the submarine volcano Hunga Tonga-Hunga Ha'apai on 15 January 2022, strong ionospheric disturbances were observed over the world. The ionospheric disturbances which attracted attention were the traveling ionospheric disturbances (TIDs) propagating radially from the volcano together with the atmospheric waves and its projection to the opposite hemisphere [1].
After the passage of TIDs and after the local sunset, there were many reports of irregularities with sharp depletion of the ionospheric density. However, it appears that there was no appropriate interpretation of such disturbances. We tried to understand the phenomena by using observations by a dense GNSS network over Japan which is the GNSS Earth Observation NETwork (GEONET) operated by the Geospatial Information Authority Japan.
The depletions of the ionospheric density accompanied small-scale irregularities and embedded in the region of enhanced total electron content (TEC). It was similar to the storm-induced plasma stream (SIPS) observed during a strong magnetic storm [2]. We investigated three-dimensional ionospheric density structures by using a GNSS tomography technique [3], and found that the structure was consistent with the theory of SIPS. The results indicated that the thermospheric neutral wind may have modified after the eruption.[1] Saito, Ionospheric disturbances observed over Japan following the eruption of Hunga Tonga-Hunga Ha’apai on 15 January 2022, Earth Planets and Space, 2022.
[2] Maruyama et al., Storm-induced plasma stream in the low-latitude to midlatitude ionosphere, J. Geophys. Res.: Space Physics, 2013.
[3] Ssessanga et al., Complementing regional ground GNSS-STEC computerized ionospheric tomography (CIT) with ionosonde data assimilation, GPS Solutions, 2021.
ST05-A012
LOFAR4SpaceWeather (LOFAR4SW) – Increasing European Space-weather Capability with Europe’s Largest Radio Telescope: Updates and Potential Future Prospects
Mario BISI1#+, Richard FALLOWS2, Rene VERMEULEN2, Stuart ROBERTSON3, Mark RUITER2, Nicole VILMER4, Hanna ROTHKAEHL5, Barbara MATYJASIAK5, Joris VERBIEST6, Peter GALLAGHER7, Tobia CAROZZI8, Michael OLBERG8, Michael LINDQVIST8, Eoin CARLEY9, Carla BALDOVIN2, Paulus KRUGER2, Maaijke MEVIUS2, Biagio FORTE10, Steve MILAN11, David JACKSON12, Bernard JACKSON13, Dusan ODSTRCIL14,15, Oyuki CHANG3, David BARNES3
1United Kingdom Research and Innovation - Science & Technology Facilities Council - RAL Space, United Kingdom, 2ASTRON - The Netherlands Institute for Radio Astronomy, Netherlands, 3United Kingdom Research and Innovation, United Kingdom, 4Observatoire de Paris, France, 5Space Research Centre of Polish Academy of Sciences, Poland, 6Bielefeld University, Germany, 7Dublin Institute for Advanced Studies, Ireland, 8Onsala Space Observatory, Sweden, 9N/A, Ireland, 10University of Bath, United Kingdom, 11University of Leicester, United Kingdom, 12Met Office, United Kingdom, 13University of California San Diego, United States, 14George Mason University, United States, 15NASA Goddard Space Flight Center, United States
Space-weather (SW) monitoring/forecasting/operations, and its unpinning research, are all important topics of the global effort to better understand and mitigate-against SW impacts. Knowledge/understanding of interactions in the Sun-Earth system, the physics behind observed SW phenomena, and the direct impact on modern technologies are all crucial areas of technological and scientific interest. A better understanding of the Heliosphere-Earth system is crucial, and this can be achieved by exploiting novel ground-based radio observations of such. The tracking of plasma structures across the inner-heliosphere is possible using instruments such as the LOw Frequency ARray (LOFAR) via observations of radio-wave scintillation – in the heliosphere, this is known as interplanetary scintillation (IPS). LOFAR is also capable of detecting ionospheric scintillation as well as undertaking other scientific investigations of the ionosphere and heliosphere. LOFAR observes over a wide radio bandwidth (~10-250 MHz) at high spatial/temporal resolutions and has capabilities that enable studies of several aspects of SW to be progressed beyond today’s state-of-the-art. However, in its present setup, it can only be used for SW campaigns. This severely limits its ability to contribute to SW monitoring/forecasting beyond its core strength of enabling world-leading scientific research. The LOFAR For Space Weather (LOFAR4SW) project (see: http://lofar4sw.eu/) was a Horizon 2020 (H2020) INFRADEV design study to undertake investigations into upgrading LOFAR for regular SW science/monitoring observations in parallel with normal radio-astronomy/scientific operations. It involved all aspects of political/scientific engagement with various stakeholders under the full recognition that SW is a worldwide threat with varied local/regional/global impacts. Here, we summarise key LOFAR observing capabilities in the context of LOFAR4SW, and, where possible, explore project ideas aiming to investigate how LOFAR can be utilised for advanced forecasts of SW conditions/impacts, via a new understanding of the Earth’s magnetosphere-ionosphere space-environment.
ST05-A015
Observations of Radio Wave Scintillation in the Auroral Ionosphere from Various Instruments
Biagio FORTE1#+, Richard FALLOWS2, Mario BISI3, Pawel FLISEK4, Kacper KOTULAK4, Andrzej KRANKOWSKI4, Maaijke MEVIUS2, Kasia BESER2, Antti KERO5, Ingemar HÄGGSTRÖM6
1University of Bath, United Kingdom, 2ASTRON - The Netherlands Institute for Radio Astronomy, Netherlands, 3United Kingdom Research and Innovation - Science & Technology Facilities Council - RAL Space, United Kingdom, 4University of Warmia and Mazury in Olsztyn, Poland, 5University of Oulu, Finland, 6EISCAT Scientific Association, Sweden
Inhomogeneities in the spatial distribution of electron density in the ionosphere can form as a consequence of plasma instability mechanisms. These inhomogeneities (or irregularities) are characterised by a gradient in the electron density that takes place over various spatial scales. In the presence of turbulent processes, larger scale irregularities cascade to smaller scale irregularities. On the basis of observations from artificial satellites, irregularities in the equatorial and high latitudes ionosphere can originate radio wave scintillation at frequencies between the VHF and C band, whereas irregularities forming in the middle latitude ionosphere can originate scintillation mainly at VHF (occasionally, L-band scintillation has been observed as a consequence of plasma structures expanding equatorward from high latitudes during disturbed magnetic conditions). Radio wave scintillation arising from irregularities in the ionosphere has been somehow regularly observed by means of the Low Frequency Array (LOFAR) radio telescope. These observations mainly relate to plasma structures forming in the middle latitude ionosphere. This contribution discusses measurements of radio wave scintillation carried out by using the KAIRA station (which is based on technology similar to standard LOFAR stations) whilst observing the Cassiopeia A object. These observations were carried out in a typical auroral ionosphere under varying magnetic conditions. The comparison between observations from KAIRA and from Global Navigation Satellite Systems (GNSS) enables to identify and characterise ionospheric irregularities forming in the auroral ionosphere. This comparison also allows to discuss any contribution originating outside of the Earth’s ionosphere (e.g., in the inner heliosphere).
ST07-A001
Investigation of Outflow O+ Dynamics in the Earth’s Magnetosphere by 3-D Global Hybrid Simulation
Xueyi WANG1#+, Chih-Ping WANG2, Yu LIN1
1Auburn University, United States, 2University of California, Los Angeles, United States
Outflow oxygen (O+) ions from the ionosphere are one of main particle source for the magnetosphere contributing to mass, momentum, and energy coupling between the ionosphere and magnetosphere. The O+ kinetic dynamics is thus crucial to understanding magnetosphere-ionosphere coupling physics. This presentation is to investigate the global properties of O+ ions and their dynamics both inside and outside the magnetosphere by using a self-consistent 3D global hybrid simulation model, ANGIE3D, developed at Auburn. Specifically, we will present a unique scenario that O+ ions could leak from dayside magnetosphere to the magnetosheath and get access into the upstream solar wind in the presence of a particular type of the IMF directional tangential discontinuity (TD). Some of the leaked O+ ions of ~10’s keV, when encounter the TD in the magnetosheath, can gyrate sunward into the solar wind. These O+ ions get continuously accelerated in the solar wind by convection electric field to > 100 keV without conserving the first adiabatic invariant, and some of them eventually move back to the inner magnetosphere and become part of the ring current. This scenario for generating ring current O+ ions is different from another more typical scenario that ions convect inward from the plasma sheet to the inner magnetosphere and get adiabatically energized.
ST07-A009
Correlations Between Giant Undulations and Plasmapause Configurations
Yijia ZHOU+, Fei HE#
Chinese Academy of Sciences, China
In this letter, we report the correlations between giant undulations (GUs) and plasmapause (PP) configurations based on GUs' images and corresponding PP crossings of satellites between 2005 and Typically, GUs occur when the plasmasphere is eroded to form a thin and sharp PP during the storm main phase and early recovery phase. The thicknesses of the PP are usually comparable with the azimuthal wavelengths of the GUs and are smaller than the radial amplitudes of the GUs. The amplitudes and wavelengths are quasi-proportional to the thicknesses of the PP and are inversely quasi-proportional to the ion density gradients around the PP. The radial centers of GUs are typically aligned with the PP surfaces and their radial geocentric locations show positive correlations for different geomagnetic storms. These results would provide both physical insights and model constrains on the magnetosphere-plasmasphere-ionosphere energy coupling and the generation mechanisms of the GUs and plasmapause surface waves.
ST07-A010
Observation of Lunar Tide Effects in Earth’s Magnetosphere
Quanqi SHI#+, Chao XIAO, et AL.
Shandong University, China
Tides are universal and affect spatially distributed systems, ranging from planetary to galactic scales. In the Earth–Moon system, effects caused by lunar tides were reported in the Earth’s crust, oceans, neutral gas-dominated atmosphere (including the ionosphere) and near-ground geomagnetic field. However, whether a lunar tide effect exists in the plasma-dominated regions such as the magnetosphere has not been explored yet. Here we show observational evidence of a lunar tide-induced signal in the plasmasphere (see DOI: 10.1038/s41567-022-01882-8, and other regions in the magnetosphere). We obtain these results by analyzing variations in the plasmasphere’s boundary location over the past four decades from multi-satellite observations. The signal possesses distinct diurnal (and monthly) periodicities, which are different from the semidiurnal (and semimonthly) variations dominant in the previously observed lunar tide effects in other regions. We identified a magnetospheric electric field variation of the same lunar period that can account for the observed plasmapause modulation. Where and how this electric field is generated also has been discussed.
ST07-A011
Downgoing, Upgoing, and Mirroring Expected Electron Spectra and Electron Precipitation Mechanisms by Geomagnetic and Ionospheric Conditions
John DOMBECK1#+, Frdrick ALONZI1, Maria BALVANERA MONTANO1, Clayton JOHNSON1, Joshua MAGNUS2
1University of Minnesota, United States, 2The University of Arizona, United States
Auroral electrons are one of the primary components of magnetosphere-ionosphere-thermosphere (MIT) coupling. Their precipitation, mirroring, interaction in the ionosphere and backscatter account for and affect many of the MIT coupling processes as well as ionospheric conditions. Understanding their composition, characteristics, and dependence on geomagnetic conditions is critical for understanding MIT coupling and ionospheric dynamics. We present the results of a new study which provides the statistically expected effective spectra and variance of downgoing, upgoing, and mirroring electron populations by geomagnetic and ionospheric conditions and location utilizing data from the entire FAST mission. Since the electron populations can be anisotropic and this is not accounted for in most ionospheric models, the effective spectra are calculated. That is the equivalent isotropic spectra over the entire loss cone that would result in the same downgoing or upgoing electron energy flux by energy as the actual distribution. We also present the results, again by geomagnetic and ionospheric conditions and location, of electron precipitation mechanism identification, e.g. wave scattered (or directly precipitating) isotropic precipitation, quasistatic potential structure (QSPS) and Alfvénic acceleration, even when multiple precipitation mechanisms are occurring simultaneously and the QSPS potentials are low compared to the isotropic precipitation temperature.
ST07-A013
The Effects of the Polar Rain on the Polar Wind Ion Outflow from the Nightside Ionosphere
Kun LI#+
Sun Yat-sen University, China
The polar wind, consisting of low-energy ions and electrons, is an outflow along the open magnetic field lines from the polar cap ionosphere to the magnetosphere. Previous studies found that both solar radiation and solar wind electromagnetic energy are the two main energy sources for the polar wind. The polar rain, being field-aligned precipitating electrons from the solar wind to the polar cap, may provide additional energies for the polar wind. This scenario is complicated as simulation studies show that polar rain changes the electric potential structures over the polar cap ionosphere. It is unclear how the polar rain affects the polar wind ion outflow. In this study, we show a positive correlation between the polar wind and the polar rain. Meanwhile, the polar wind is generally diminished in regions with strong Earth’s magnetic field, suggesting the B modulates the penetration depth of the polar rain through the magnetic mirror force and thus the energy dissipation of the polar rain. Therefore, the polar rain can be an additional energy source for the polar wind although the polar rain has generally smaller energies and intensities than the particle precipitations in the auroral regions.
ST07-A014
Lifetime of Energetic Electrons Due to Their Interactions with Chorus Waves
Dedong WANG#+, Yuri SHPRITS, Bernhard HAAS
GFZ German Research Centre for Geosciences, Germany
Energetic electrons in the Earth's magnetosphere can be dangerous to satellites. Chorus waves can cause the loss of energetic electrons in this area via pitch-angle scattering. To quantify the effect of chorus waves on energetic electrons, we calculate the bounce-averaged quasi-linear diffusion coefficients. In this study, using these diffusion coefficients, we calculated the lifetime of the electrons with an energy range from 1 keV to 2 MeV using two different methods. We parameterize the electron lifetime as a function of $L$-shell and electron kinetic energy in each MLT and geomagnetic activity (Kp). The parameterized electron lifetimes show a strong functional dependence on $L$-shell and electron energy. This new model of electron lifetime is more advanced than previous models. In particular, the current model fills the gap that previous models have on the dusk side of the Earth's magnetosphere. This improvement is critical for radiation belt and ring current modelling studies.
ST07-A016
Arase and Van Allen Probes Observations of Variations of Energetic Ion Pitch Angle Distribution and Rapid Flux Variation During Substorm Time Scales
Trunali SHAH1#+, Veenadhari BHASKARA1, Masahito NOSÉ2
1Indian Institute of Geomagnetism, India, 2Nagoya University, Japan
The study investigates variations in the ion flux and pitch angle distribution for the substorms in the inner magnetosphere for the years 2017-2019. The temporal evolution of O+, H+, and He+ ion flux distribution is studied using Arase and Van Allen Probes (VAP/RBSP) spacecraft. RBSP and Arase satellites have different inclinations which give us an opportunity to study the spatiotemporal effect of the substorm time flux variation. The flux variations are also accompanied by magnetic field dipolarization. Previous studies of magnetic field dipolarization in the outer magnetosphere revealed that it is capable of accelerating ions to a few hundred keV. This study focuses on substorm-associated magnetic field dipolarization in the inner magnetosphere as it would play an important role in developing the ring current through in situ acceleration of ions. The Helium Oxygen Proton Electron (HOPE) spectrometer, the Electric Magnetic Field Instrumentation Suit, and Integrated Science (EMFISIS) data on board the RBSP satellite are used. The Low-energy particle experiments (LEPi) and Medium-energy particle experiments (MEPi) data cover the energy range 0.01 keV/q to 180 keV/q which is significant for the substorm time particle dynamics is also used. The purpose of this study is to investigate the possible relationship between ion flux variation and corresponding particle dynamics. The detailed results with analysis of a significant number of events and related mechanisms will be discussed in the meeting.
ST07-A024
Dynamics of Turbulence Behind the Bow Shock and Its Dependence on the Solar Wind Conditions
Liudmila RAKHMANOVA1#+, Maria RIAZANTSEVA1, Alexander KHOKHLACHEV 1, Georgy ZASTENKER2, Yuri YERMOLAEV1
1Space Research Institute of the Russian Academy of Sciences, Russian Federation, 2Russian Academy of Sciences, Russian Federation
Magnetosheath serves as a link between the solar wind and the Earth’s magnetosphere. Experimental studies of last decades demonstrated significant role of the magnetosheath processes and turbulent variations in the global magnetosphere dynamics. Though properties of the magnetosheath turbulence are generally known, the global picture of its development behind the bow shock is still unclear. Present study considers evolution of the turbulence properties while solar wind plasma crosses the bow shock and propagate from the subsolar magnetosheath toward the flanks. Simultaneous observations in three points of the near-Earth’s space are considered – in the solar wind, in the dayside magnetosheath and at the flanks – for various solar wind conditions. The study uses Fourier analysis of fast measurements (with 4/s cadence or better) from a chain of spacecraft such as Wind, Cluster, Themis, Spektr-R and MMS. The work is focused on features of the turbulent cascade around ion scales, where MHD description of plasma flow may not provide satisfactory results and kinetic processes become important. The results show that for undisturbed slow solar wind the fluctuation spectra deviate from typical scaling just in the magnetosheath region close to the bow shock. On the other hand, during the disturbed solar wind (like ICMEs) such deviation occurs in the whole dayside magnetosheath. Spectra tend to restore their initial shape when plasma moves toward the flanks. However, interaction of the compressed solar wind (such as CIRs) with the magnetosheath results in arising of additional compressive fluctuations accompanied with flattening of the fluctuation spectra at the kinetic scales at the magnetosheath flanks. Thus, the conditions in the solar wind play crucial role in dynamics of the magnetosheath turbulence both at MHD and kinetic scales, that can be important for global magnetosphere dynamics. The work is supported by Russian Science Foundation grant № 22-12-00227.
ST07-A026
Complex Magnetospheric Dynamics Based on Forward and Inverse Karman Vortex Coupling
Dongsheng CAI#+
University of Tsukuba, Japan
Complex Magnetospheric Dynamics based on Forward and Inverse Karman Vortex Coupling Kelvin-Helmholtz (K-H) vortexes have been intensively studied using 3D global MHD simulations in the northward IMF. However, they discuss K-H instability theory based on the linear theory and none of them discuss about their nonlinear evolutions and their non-linear behaviors like Karman vortex street, vortex coherency or coherent turbulent structure etc. Those linear vortices evolve to be the so-called the Karman vortex pairs or vortex street between the inner and outer side of the magnetopauses in both dawn and dusk side of the magnetosphere, where the inner vortices are induced by some mechanism under investigation. These vortices are the so-called longitudinal vortices and generated along the earth magnetic field toward both north and south pole. When these vortices extend toward the north and south pole, both vortices from the dawn and dusk sides face each other near the north and south ionosphere and form the so-called inverse Karman vortexes. This is because when they face each other near the ionosphere the rotational direction is inverse to the ordinary Karman vortexes. Thus, the coupling mechanism through the vortex induction between two vortex systems at dawn and dusk side of the magnetosphere are generated. In addition, these inverse Karman vortex coupling are also related to the lobe reconnections.
ST08-A002
Latitudinal Differences of Substorm Expansion Auroras Between Polar VIS and UVI Observations
Suwicha WANNAWICHIAN1#+, Yukinaga MIYASHITA2,3
1Chiang Mai University, Thailand, 2Korea Astronomy and Space Science Institute, Korea, South, 3Korea National University of Science and Technology, Korea, South
Auroral images taken by the Visible Imaging System (VIS) and the Ultraviolet Imager (UVI) instruments onboard the Polar spacecraft were studied in this work to reveal the locations of initial brightening and maximum poleward expansion during several substorms. For aurora associated with low-energy, "soft," precipitating electrons, the responsive auroral emissions were shown in Polar/VIS (557.7, 130.4, 391.4, and 630.0 nm) images. On the other hand, the FUV auroras are presented in Polar /UVI (LBH long, LBH short, 130.4, and 135.6 nm) images, representing the results of higher energy precipitating auroral particles (mostly electrons). The poleward expansions of visible auroral emissions reach higher latitudes than the expansions of far ultraviolet auroral emissions. The latitude of initial brightening was also higher for the visible emissions than for the far ultraviolet emissions. These results suggest that high-energy precipitating electrons producing far ultraviolet aurora tend to be distributed or generated more in the near-Earth magnetotail, while low-energy particles (mostly soft electrons) producing visible aurora are distributed to the more tailward region.
ST08-A003
Unusual Shrinkage and Reshaping of Earth's Magnetosphere Under a Strong Northward Interplanetary Magnetic Field
Xiang-Yu WANG1+, Qing-He ZHANG2,1#, Chi WANG3, Yongliang ZHANG4, Binbin TANG3, Zanyang XING1, Kjellmar OKSAVIK5, Larry LYONS6, Michael LOCKWOOD7, Qiugang ZONG8, Guo-Jun LI9, Jing LIU1, Yu-Zhang MA1, Yong WANG1
1Shandong University, China, 2National Space Science Center, Chinese Academy of Sciences, China, 3Chinese Academy of Sciences, China, 4Johns Hopkins University Applied Physics Laboratory, United States, 5University of Bergen, Norway, 6University of California, Los Angeles, United States, 7University of Reading, United Kingdom, 8Peking University, China, 9Chongqing University of Posts and Telecommunications, China
The Earth’s magnetosphere is the region of space where plasma behavior is dominated by the geomagnetic field. It has a long tail typically extending hundreds of Earth radii (RE) with plentiful open magnetic fluxes threading the magnetopause associated with magnetic reconnection and momentum transfer from the solar wind. The open-flux is greatly reduced when the interplanetary magnetic field points northward, but the extent of the magnetotail remains unknown. Here we report direct observations of an almost complete disappearance of the open-flux polar cap characterized by merging poleward edges of a conjugate horse-collar aurora (HCA) in both hemispheres’ polar ionosphere. The conjugate HCA is generated by particle precipitation due to Kelvin-Helmholtz instability in the dawn and dusk cold dense plasma sheets (CDPS). These CDPS are consist of solar wind plasma captured by a continuous dual-lobe magnetic reconnections, which is further squeezed into the central magnetotail, resulting in a short “calabash-shaped” magnetotail.
ST08-A009
Investigating Proton Temperature Anisotropy of the Slow Solar Wind with Alfven-wave Turbulence and Micro-instabilities
Hwanhee LEE1#+, Jungjoon SEOUGH1, Bo LI2, Yeon-Han KIM1, Kyungsuk CHO1
1Korea Astronomy and Space Science Institute, Korea, South, 2Shandong University, China
We investigate a one-dimensional solar-wind model that incorporates a curved magnetic field and low-frequency Alfven-wave turbulence. The mechanism for plasma heating and acceleration in this model is represented by the wave dissipation of anisotropic turbulent cascade used in the fast solar wind near a polar coronal hole (Chandran et al. 2011). We extend this mechanism to apply to the slow solar wind by considering a curved magnetic field and also consider the effect of the micro-instabilities on proton temperature anisotropy. The characteristics of the steady-state solution described in this model appears to be associated with those of the Alfvenic slow solar wind stream that are recently reported in the inner heliospheric missions. It is suggested that the dissipation mechanism can be applied in common to both slow and fast solar winds and that the proton cyclotron instability may work effectively near 10-30 solar radii and Earth.
ST08-A012
Soft X-ray Imaging of the Earth's High-latitude Reconnection Region Under Northward Interplanetary Magnetic Fields
Ryota MOMOSE1#+, Yosuke MATSUMOTO1, Yoshizumi MIYOSHI2
1Chiba University, Japan, 2Nagoya University, Japan
The charge exchange between high charge-state ions in the solar wind and the Earth's exosphere (geocorona) emits soft X-rays. This emission process, termed SWCX (Solar Wind Charge eXchange), is useful for visualizing the dayside magnetosphere and its response to solar wind variations. The SMILE and GEO-X missions have been proposed to provide soft X-ray images of the magnetosheath and cusps and will contribute to a better understanding of the dynamic response of the Earth's magnetosphere. For this purpose, we have developed a global magnetohydrodynamic simulation model of the magnetosphere (Matsumoto and Miyoshi, 2022). The model can provide three-dimensional distributions of the soft X-ray intensity from the plasma parameters. Then line-of-sight integrations of the intensity distribution give a two-dimensional X-ray map as a virtual observation in the simulation domain. Therefore, simulation runs under different solar wind conditions allow us to understand how the global intensity map reflects the magnetospheric dynamics. We studied 2D X-ray maps under northward interplanetary magnetic field conditions seen from a high-latitude spacecraft orbit. We found that virtual observations successfully identified the shape of the high-latitude magnetopause. Furthermore, we found that under low plasma-β solar wind conditions, the X-ray intensity can reflect the bulk motion of outflows from the high-latitude reconnection region. This particular observation will give great opportunities to visually understand the spatial extent of the high-latitude magnetic reconnection.
ST08-A013
Why Should We Pay Attention to the Space Environment During Solar Minimum?
Kyung Sun PARK1#+, Jinhye PARK2, Young-Sil KWAK3
1Chungbuk National University, Korea, South, 2Kyung Hee University, Korea, South, 3Korea Astronomy and Space Science Institute, Korea, South
We carried out a high-resolution 3D MHD simulation of the interaction between the solar wind and the magnetosphere during a strong magnetic substorm on June 8, 2019, during the solar minimum. The input parameter to the simulation was from the OMNI solar wind and IMF data for 8 hour period on June 8. The solar wind density is over 20 cm-3 and it increases up to 49 cm-3 with a slow velocity. The dynamic pressure of the solar wind is in the range of 2-12 nPa. The IMF Bz has decreased to -18.5 nT at 1655 UT. In this period, there was no solar flare and CME, and zero sunspot number. However, the AL index reached the minimum value of -1500 nT when the Dst index was not changed significantly. The cross-polar cap potential value from SuperDARN had up to 83 kV while it maintained above 60 kV. Similar disturbances phenomena were frequently observed in 2019 even though the solar minimum. We selected several similar events to identify the causes and differences. From the simulation results, we show that the configuration of the magnetic field lines is dramatically changed by the IMF angle. The stretched closed field lines appear at dawn and dusk flank region. The strong tail reconnection occurs during the strong southward IMF at 1655 UT but the plasma sheet become thin after the tail reconnection and the strong tailward flow in there. The flow in the throat region (near noon) is poleward on the dayside and enhanced energy flux on the dayside is confined in the cusp region. The open-closed boundary extends at 66° on the night side. The cross-polar cap potential is governed by IMF Bz in this event. The simulated cross-polar cap potential is consistent with the inferred from the SuperDARN observation.
ST10-A003
Quantitative Analysis of Electron Acceleration in Coalescing Magnetic Flux Ropes at Earth’s Magnetopause
Wenqing MA1+, Meng ZHOU1,2#, Zhihong ZHONG1
1Nanchang University, China, 2University of California, Los Angeles, United States
The coalescence of magnetic flux ropes (MFRs) is widely acknowledged as a crucial mechanism for electron acceleration in astrophysics. However, in-situ observations of electron acceleration resulting from flux rope coalescence are limited due to the vast spatial scale in astrophysical environments. Our study, using magnetospheric multiscale (MMS) observations, reveals the presence of three coalescing MFRs in pairs at Earth’s magnetopause, which resulted in the generation of superthermal electrons. We find that the superthermal electron flux in the coalescing MFRs was several times higher compared to that in the magnetosheath. Two primary mechanisms, Fermi acceleration and parallel electric fields (E||), were responsible for the electron acceleration, with betatron acceleration being negligible. The majority of Fermi acceleration was observed in the squeezed magnetic flux rope at the center of the three MFRs, while E||-driven acceleration occurred primarily at the reconnection site between the coalescing MFRs. Our results indicate that coalescence enhances Fermi acceleration more than non-coalescing MFRs.
ST10-A010
Magnetospheric Multiscale Observations of Kelvin-Helmholtz Waves and Magnetic Reconnection Under Southward Interplanetary Magnetic Field
Tongkuai LI#+, Wenya LI, Binbin TANG, Chi WANG
Chinese Academy of Sciences, China
Kelvin-Helmholtz (K-H) waves and magnetic reconnection are two important physical phenomena frequently occurring at the Earth's magnetopause, which play a crucial role in transporting mass, momentum, and energy from the solar wind into the magnetosphere. Whether the K-H waves and magnetic reconnection can occur simultaneously under southward interplanetary magnetic field (IMF) is still unclear. Here, based on in-situ observations from the Magnetospheric Multiscale (MMS) mission, we analyzed one K-H wave event under southward IMF accompanied by on-going magnetic reconnection. The K-H waves are identified by the quasi-periodic fluctuations, the plasma with low density and high speed, and the variation of the boundary normal vectors on the leading and trailing edges. The on-going magnetic reconnection is identified by the Alfvenic ion jets and escaping of the magnetospheric electrons. The signals of on-going reconnection are found in most current sheet crossings on both the trailing and leading edges. These results indicate that the co-occurring process of the K-H waves and magnetic reconnection under southward IMF is different from that under northward IMF. The K-H waves can promote the excitation of magnetic reconnection by the current-sheet thinning along the magnetopause. On the other way, magnetic reconnection may likely suppress the evolution of the K-H waves.
ST10-A011
Energization of Cold Ions in Asymmetric Reconnection: Particle-in-cell Simulation
Liangjin SONG1+, Meng ZHOU1,2#, Yongyuan YI1, Xiaohua DENG3
1Nanchang University, China, 2University of California, Los Angeles, United States, 3Wuhan University, China
Cold ions from Earth's ionosphere and plasmasphere are frequently observed at the Earth's magnetopause, impacting reconnection in ways such as altering the reconnection rate and energy budget. Despite extensive research on reconnection, the fluid properties and kinetics of cold ions in magnetopause reconnection remain unclear. Our recent 2-D particle-in-cell simulation provides new insight into cold ion dynamics in asymmetric reconnection. Our simulation shows that cold ions, initially located only in the magnetosphere, absorb 10% to 25% of the total released magnetic energy, primarily converting it into thermal energy through stochastic heating, that is, the viscous heating associated with the non-gyrotropic pressure tensor. Cold ions are step-by-step accelerated by the Hall electric field during meandering motion across the magnetopause current sheet. The velocity distribution functions of cold ions in different regions are made up of two types of particles, differentiated by their ability to penetrate into the magnetosheath. The reconnection electric field has different effects on these two types of cold ions. As reconnection continues, the velocity distribution functions of the cold ions diffuse, leading to bulking heating. These findings significantly enhance our understanding of cold ion dynamics at the Earth's magnetopause.
ST10-A022
Formation of Negative J*E' in the Electron Diffusion Region During Magnetic Reconnection: PIC Simulations and MMS Observations
Qiyang XIONG1+, Shiyong HUANG1#, Meng ZHOU2,3, Zhigang YUAN1, Xiaohua DENG1, Kui JIANG1, Yunyun WEI1, Sibo XU1, Jian ZHANG1, Rentong LIN1, Lin YU1
1Wuhan University, China, 2Nanchang University, China, 3University of California, Los Angeles, United States
It is widely acknowledged that high positive energy conversion J*E’ from the fields to the plasma occurs in the electron diffusion region (EDR) during magnetic reconnection. There also exists negative J*E’ which means the particles return the energy to the field. How this kind of negative energy conversion appears in the reconnection is still lack of comprehensive explanation. In this study, we applied 2.5-D full kinetic particle-in-cell (PIC) simulations and high-resolution data from Magnetospheric Multiscale mission (MMS) to reveal the formation of the negative J*E’ near the EDR. Two main regions are found to have the negative energy conversion gathering: one is the outer EDR, and the other one is the inflow edge of the inner EDR. The PIC simulations suggest that in the outer EDR the negative J*E’ is contributed by the electron inertial term of the generalized Ohm’s law due to the deceleration of the electrons. This deceleration is caused by the opposite electric field which is induced by the magnetic field accumulation in the outer EDR. On the other hand, both PIC simulations and MMS observations verify that the negative J*E’ in the inflow edge is balanced by the electron pressure tensor term. The energy loss of the electrons plays the dominant effect in this term and the energy decline is caused by the electric field which induced by the decreasing magnetic field in the inflow region. These results provide significant insights to expand the understanding of the reconnection regimes.
ST10-A023
Simultaneous Observations of Dayside Magnetopause Crossings from MMS and THEMIS
Chongle ZHANG#+, Wenya LI, Binbin TANG
Chinese Academy of Sciences, China
Response of the magnetopause to the upstream solar wind is an important issue to understand the mass and energy transfer across this boundary, but the spatial-temporal effect is usually hard to distinguish. In this study, we have performed simultaneous observations of dayside magnetopause crossings from MMS and THEMIS to investigate the magnetopause activities spatially. We search for such magnetopause crossing events under the constraints that the time difference of the magnetopause crossing between MMS and THEMIS is less than 5 minutes. The results show that the MMS and THEMIS can observe either similar or dissimilar magnetopause activities (i.e. The reconnection jet) at different events at a separation of several Earth radii. These observations can be attributed to the limited spatial extent of magnetopause activities and/or different responses to the upstream solar wind.
ST10-A024
Observations of Dynamical Flux Ropes and Active Multiple X-line Reconnection at Earth’s Magnetopause
Zhihong ZHONG1#+, Guangya LEI1, Meng ZHOU1,2, Meng ZHANG1, Rongxin TANG1,3, Daniel GRAHAM4, Ye PANG1, Xiaohua DENG5, Yuri KHOTYAINTSEV4
1Nanchang University, China, 2University of California, Los Angeles, United States, 3Memorial University of Newfoundland, Canada, 4Swedish Institute of Space Physics, Sweden, 5Wuhan University, China
We present the Magnetospheric Multiscale (MMS) observations of three flux ropes (FRs) sequentially in a reconnection exhaust at Earth’s magnetopause. Three active X-lines, which are responsible for the formation of these FRs, were also detected by MMS, providing strong evidence that the FRs were generated by multiple X-line reconnection. We find that the core field inside the FRs considerably affects the Hall current in the adjacent X-lines. The intense core field of the FRs deflected the electron outflow jet, forming the electron-scale Hall magnetic field on the magnetosheath side. Additionally, an active secondary reconnection was observed at the center of one FR. This secondary reconnection split the FR into two smaller FRs and produced sharp density gradients and intense fluctuations of electric field and current within the FR. Our observations advance the understanding of the formation and evolution of FRs during multiple X-line reconnection at magnetopause.
ST11-A002
Forecasting the Final Dst Index with Temporal Convolutional Network
Junyan LIU1#+, Chenglong SHEN1, Mengjiao XU1, Yutian CHI2, Zhihui ZHONG1, Dongwei MAO1, Zhiyong ZHANG1, Can WANG3
1University of Science and Technology of China, China, 2Deep Space Exploration Laboratory, China, 3China Earthquake Administration, China
The Dst Index(disturbance storm time index) is one of the most important geomagnetic indices to describe the strength of geomagnetic activity. The accurate prediction of the Dst index helps avoid the hazards of severe space weather events. Therefore, Dst prediction has been a hot topic in space physics and space weather forecasting for a long time. Using observational data such as three components of the magnetic field, solar wind speed, proton density, etc., this paper incorporates the temporal Convolutional Network (TCN) to predict the Dst indices. Compared to the previous machine learning model, our model has very high forecast accuracy. The specific results are: the mean square root error (RMSE) between the prediction value and the real value is 2.876, the average absolute error (MAE) is 2.003 and the correlation coefficient r is 0.9846. Our single model can reach equivalent accuracy predicted by several machine learning models together. Besides, we also try to explain our model with the integrated gradient(IG) algorithm. The past Dst index, the z component of magnetic field $B_z$, and the plasma flow speed during the past two hours are the main control parameters for the Dst index prediction. These results confirm that the TCN algorithm can help us to improve the space weather forecast accuracy and understand the physical processes in space weather at the same time.
ST11-A003
Interplanetary Coronal Mass Ejection Southward Magnetic Field Estimation at Venus Based on In-situ Observations at 1AU
Dongwei MAO1+, Chenglong SHEN1#, Yutian CHI2, Mengjiao XU1, Zhihui ZHONG1, Junyan LIU1, Zhiyong ZHANG1, Can WANG3
1University of Science and Technology of China, China, 2Deep Space Exploration Laboratory, China, 3China Earthquake Administration, China
Development of human activities at other planets calls for space weather forecasting, especially southward magnetic field of Interplanetary Coronal Mass Ejections(ICMEs) which are related to intense magnetic storms. We select several ICMEs that can be detected by both Venus Express and WIND and estimate their magnetic fields at Venus based on in-situ observations at Earth. The magnetic structure of ICMEs is described with Lunquist model, and parameters of the model are gained from a least square fitting method. The propagation of ICMEs is assumed to be self-similar, so the ICME magnetic structure at Venus can be calculated from which at Earth. A drag-based model is used to estimate the arrival time of ICMEs at Venus based on the speed profile and time of arrival at Earth.
ST11-A005
Variations in Regional Precipitation Under Extreme Solar Activity
Yuqi WANG+, Yong WEI#
Chinese Academy of Sciences, China
Extreme solar activity can cause space weather hazards and have a significant impact on the Earth's weather and climate. Direct observations of sunspots date back about 400 years, when Maunder Minimum (1645-1715) was discovered and accompanied by prolonged periods of severe cold in the Earth's climate. This research contributes to analyse the regional precipitation variations under extreme solar activity. A unique approach was taken to reconstruct the continuous annual precipitation in Seoul from 1625 to the present based on the ancient book, including the world's earliest continuous instrumental rainfall records. Based the independent precipitation database, we found a significant correlation between solar activity and regional precipitation on multiple time scales. (i) An 11-year sunspot cycle exists in regional precipitation variation. (ii) During periods of the great Solar Minimum, summer rainfall and winter snowfall are significantly reduced on an interdecadal scale. (iii) Extreme precipitation is more likely to occur during sunspot maximum or minimum. The mechanisms by which solar activity affects sea-air coupling and hence precipitation in the Pacific region are complex. Investigating precipitation changes under extreme solar activity is of great significance to human production and to help deal with drought and flood disasters.
ST11-A006
The Interplanetary Origins of Geomagnetic Storm with Dst < -50 nT During Solar Cycle 24 (2009–2019)
Zhiyong ZHANG#+, Shican QIU
University of Science and Technology of China, China
In this study, we analyzed 149 geomagnetic storms of moderate and intensity (i.e., Dstmin < -50 nT) occurred during the solar cycle 24 from 2009 to 2019, and identified their interplanetary sources. Among them, there are 20 strong storms with -200 nT < Dstmin < -100 nT, and 2 super–strong storms with Dstmin < -200 nT. We have found that corotating interaction regions (CIRs) account for 37% (55/149) of geomagnetic storms, interplanetary coronal mass ejections (ICMEs) result in 30% (45/149) of geomagnetic storms and sheath regions (SH) are responsible for 15% (23/149) of geomagnetic storms. Meanwhile, 18/20 of the strong storms are caused by the structures associated with interplanetary coronal mass ejections (ICME, SH, and SH + ICME), while the CIR constitutes only to 2/20 of the strong storms. It is found that the two super–strong geomagnetic storms are caused by the SH + ICME. Our findings also suggest that geomagnetic storms in different periods of solar activity are caused by different interplanetary structures, which is consistent with previous research. In comparison to solar cycle 23, there is no substantial geomagnetic storm induced by CIR during the dwindling and subsiding phases of solar cycle 24. In the descending stage, the proportion of moderate events caused by ICME decreases, and ICMEs cause no super–strong event. In ascending stage, neither strong nor super strong events occur.
ST11-A009
Analysis of the Interaction Between Coronal Mass Ejections Based on a Simplified Collision Model
Zhihui ZHONG1+, Chenglong SHEN1#, Yutian CHI2, Can WANG1, Mengjiao XU1, Dongwei MAO1
1University of Science and Technology of China, China, 2Deep Space Exploration Laboratory, China
Coronal mass ejection (CME) is a large-scale solar explosion, which carries a large amount of plasma into interplanetary space and affects the interplanetary environment. The continuous bursts of multiple CMEs, specially the interaction between CMEs, will make the magnetic field and plasma environment in solar-terrestrial space more complex. According to previous studies, the interaction between CMEs will change the propagation direction and velocity of CMEs, and even super-elastic collision occurs. However, due to the complex structure of CMEs and the lack of observation equipment, the interaction process between CMEs cannot be well explained. In this work, a simplified collision model is proposed to analyze the interaction between CMEs. In order to verify the effectiveness of this model, we analyzed two events. The results show that our simplified collision model can effectively describe the interaction process of the two CMEs and predict the velocity and direction of post-interaction CMEs.
ST12-A009
Interference Suppression Method of Oblique Backscatter Ionogram Based on Adaptive Partitioning of Eigen-subspaces Filtering
Chongzhe LAO#+, Guobin YANG, Tongxin LIU, Chunhua JIANG
Wuhan University, China
The oblique backscatter sounding method can provide ionospheric state information with a radius of several thousand kilometers in all directions, which is a promising ground-based detection technology. However, some celestial interference and industrial interference will greatly reduce the signal-to-interference-noise ratio of the ionospheric oblique backscatter detection signal, making it difficult to extract ionospheric information from the ionogram. In this study, an interference suppression algorithm based on adaptive partitioning of eigen-subspaces for low power oblique backscatter detectors is proposed. The interference data of WIOBSS is decomposed and subjected to an adaptive subspace division based on the plural criterion, the echoes are projected into the signal subspace to filter out the interference, and the background noise is homogenized by a constant false alarm, with an energy contrast stretching algorithm to enhance the signal in the HF band to obtain a high contrast oblique back scatter ionogram with a uniform background, which greatly improves the information extraction capability of the oblique backscatter ionogram. Both simulation and experimental results are provided to illustrate the performance of the proposed method. This algorithm is more reliable than the image domain algorithm, has lower hardware requirements and is easier to implement than the air domain algorithm, which has good engineering application value.
ST13-A007
Features of Low-frequency Waves in the Plasma Sheet Associated with Dipolarization for Substorms and Pseudosubstorms
Kanpatom KASONSUWAN1#+, Yukinaga MIYASHITA2,3, Suwicha WANNAWICHIAN1
1Chiang Mai University, Thailand, 2Korea Astronomy and Space Science Institute, Korea, South, 3Korea National University of Science and Technology, Korea, South
Substorms and pseudosubstorms (pseudobreakups) involve explosive auroral activities which are caused by the magnetotail dynamics. Previous studies showed that substorms and pseudosubstorms have some different characteristics in both spatial and temporal development. This study mainly focuses on the features of low-frequency (0.002 - 0.006 Hz), Pi2, and Pi1 waves in the plasma sheet, such as wave power and Poynting flux, based on superposed epoch analysis of data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. We find that low-frequency and Pi2 waves are amplified before dipolarization onset, followed by Pi1 waves at the onset. This result suggests that an instability related to low-frequency waves, such as ballooning instability, is excited before dipolarization onset, and then other instabilities related to higher-frequency waves are excited at dipolarization onset. The power and parallel Poynting flux toward the ionosphere of low-frequency, Pi2, and Pi1 waves for substorms are more intense than those for pseudosubstorms. Moreover, the wave powers of the magnetic field during pseudosubstorms decrease earlier than those during substorms. These results suggest that both an instability related to low-frequency waves and instabilities related to higher-frequency waves grow sufficiently for full-fledged substorms or auroral poleward expansion. The wave power of the parallel component related to magnetosonic waves is more intense than those of the perpendicular components related to Alfven waves for both substorms and pseudosubstorms. The wave parallel Poynting flux toward the earth ionosphere after dipolarization onset during substorms is larger and lasts longer than that during pseudosubstorms.
ST13-A009
Global ULF Waves Excited by Positive Solar Wind Dynamic Pressure Impulses: Ground-based Statistical Study
Zikang XIE1+, Qiugang ZONG1#, Jie REN2, Chao YUE1, Zhiyang LIU1, Li LI1, Ze-Fan YIN1, Xingyu LI1
1Peking University, China, 2China University of Geosciences, China
The positive solar wind dynamic pressure pulse is one of the sources of ULF waves. Based on 1s-resolution magnetic field observations from global geomagnetic stations between the beginning 2012 and the end of 2019, we conducted statistics on temporal and spatial variations of gloal ULF power after the positive dynamic pressure pulse arrival. The magnetosphere responds quickly to the dynamic pressure pulse within 1 minute, and at low L values, it takes 4 to 6 minutes for the ULF waves to reach a power maximum, with a local decay time scale of about 10 minutes in magnitude. A dawn-dusk Pc3 power asymmetry is independent of solar wind conditions. indicating that Pc3 fluctuations may be excited by multiple sources and influenced by the effects of propagation. There is a north-south asymmetry in ULF fluctuations, and higher latitudes in the northern hemisphere tend to have stronger fluctuations. The magnetic field power in different bands exhibits seasonal effects, which can be further explained by the R-M effect. Based on the integrated power intensity of different bands of the global geomagnetic stations, and it would be helpful to compare the results with observations of satellites in GEO orbit such as the SWARM and Champ. Widespread asymmetries in different IMF conditions need to be further studied.
ST13-A011
The Structure Particle Distribution and Aurora Associated with Magnetospheric Compressional Pc5 Waves
Anmin TIAN#+
Shandong University, China
Pc5 compressional wave observed in the Earth magnetosphere is attracting extensive attention due to its high occurrence, rich wave-particle interaction processes and possible ionospheric effects. The complete geometric picture and particle pitch angle distributions (PADs) are keys to understand the generation and spatial effects of this kind of wave. However, there has been a lack of sufficient observation support. In our recent works, we built the three dimensional geometric structure of the wave and obtained the statistical characteristics of electron PADs and aurora phenomena related to the wave using data from MMS and THEMIS mission. It is found that the equatorial cross-section of the magnetic decreases (troughs) of compressional Pc5 waves has an 'eccentric wedge-like' shape with a radial scale larger than 4Re. The electron PADs in the magnetic troughs are classified into three types: cigar, butterfly, and pancake. The dependence of electron PAD types on electron energy depends on whether whistler waves are observed in the magnetic troughs or not. We further systematically expounded the modulation effect of Pc5 compressional wave on aurora based on THEMIS spacecraft and ground all sky imager observations.
ST13-A012
Spatial Propagation of Ground ULF Magnetic Field Oscillations Excited by Different Types of Foreshock Bubbles
Jiaqi LIU1+, Boyi WANG1#, Terry LIU2, Desheng HAN3, Yi WANG4, Vassilis ANGELOPOULOS2
1Harbin Institute of Technology, Shenzhen, China, 2University of California, Los Angeles, United States, 3Tongji University, China, 4Harbin Institute of Technology, China
Foreshock bubbles are transient structures caused by the interaction of suprathermal backstreaming ions upstream of the bow shock with rotational discontinuities (RDs) or tangential discontinuities (TDs). Due to their hot tenuous cores, foreshock bubbles can inflate the magnetopause and excite magnetospheric Pc5 (1.66~6.66 mHZ) ultra-low frequency (ULF) waves, which are proposed to be global by hybrid simulations. These waves are possibly transported to the ground through the coupled magnetospheric and ionospheric system. However, how do foreshock bubbles contribute to ground magnetic field disturbances and does this contribution depends on the characteristics of foreshock bubbles are still poorly understood. In this study, we investigate the differences between RD-driven and TD-driven foreshock bubbles in generating ground magnetic field oscillations (primarily in Pc5 band), based on the conjugated observations by the THEMIS satellites and high-latitudinal (60-75 MLAT) ground-based magnetometers in 2008, 2009 and in 2019. Multiple foreshock bubble events show that foreshock bubbles can indeed generate significant ground magnetic field Pc5 ULF oscillations. But we further found that whether these induced oscillations can propagate globally or propagate through only one side of the magnetosphere (duskward or dawnward) probably depend on the types of the associated interplanetary magnetic field (IMF) discontinuities (TD or RD), their normals and the relative position between the core of a foreshock bubble and its associated IMF discontinuity. More relationships between the characteristics of foreshock bubbles with the associated ground magnetic field oscillations will also be discussed.
ST13-A016
Statistical Characterization of Joule Heating Related to Ionospheric ULF Perturbations Using SuperDARN Data
Xueling SHI1,2#+, Shibaji CHAKRABORTY1, Joseph BAKER1, Michael HARTINGER3, Dong LIN2, Wenbin WANG2, J. RUOHONIEMI1, Kevin STERNE1
1Virginia Tech, United States, 2National Center for Atmospheric Research, United States, 3Space Science Institute, United States
Ultra-low frequency (ULF; 1 mHz - several Hz) waves are ubiquitous in the solar-terrestrial environment. They play important roles in transporting and coupling energy throughout the geospace system. Despite the fact that ULF pulsations have been studied for over a century, major questions remain regarding their significance for energy deposition through Joule heating in the ionosphere-thermosphere (I-T) system. The objective of this study is to quantify the energy deposition in the I-T system related to ionospheric ULF perturbations. We use measurements from SuperDARN HF coherent scatter radars operating in a special mode, in which three camping beams are sampled at ~ 18 s by interleaving soundings on the camping beams with successive beams of the normal azimuth scan. The Joule heating rate associated with ULF perturbations is estimated by using ionospheric electric fields from SuperDARN measurements and height-integrated Pedersen conductance from empirical models. We report statistical results on the ionospheric ULF wave occurrence and related electric field distributions. The dependencies of the ULF wave-related Joule heating rate on wave properties, solar wind conditions, and geomagnetic activity level are investigated. The results provide new insights into the role of ULF waves in energy transfer and dissipation in the geospace system.
ST13-A023
Statistical Study on the Azimuthal Mode Number of Pc5 ULF Wave in the Inner Magnetosphere
Wenlong LIU#+
Beihang University, China
The azimuthal mode number, m, of the ULF wave is important in the wave-particle interaction with radiation belt electrons because it determines the resonating energy of the particles. Based on multi-point magnetic field measurements of GOES satellites from January to September 2011, we statistically analyze the characteristics of the m value of Pc5 ULF waves. The wave propagation directions are classified into eastward or westward directions according to the sign of m. We find that in the dayside, the waves propagate predominantly westward (eastward) in the post-non (pre-noon), i.e., propagating anti-sunward. We also find that during quiet periods, the waves of |m|≤3 dominate in the inner magnetosphere. With increasing solar wind and geomagnetic activity, the intensity of ULF waves in the magnetosphere is also enhanced and the waves of |m|>3 have a stronger response to substorm activity at nightside.
ST14-A003
The Dynamics of Near-solar Charged Nanodust During the Rising Phase of the Solar Cycle 24
Yi-Shiang TZENG1#+, Li-Ping YANG2, Wing-Huen IP1
1National Central University, Taiwan, 2Chinese Academy of Sciences, China
For decades, the information on the near-solar dust cloud has been acquired through not only remote-sensing observations but the detections of high-speed nanodust impacts by spacecraft, such as Ulysses and Parker Solar Probe (PSP). These nanodust impact measurements are generally believed to result from the so-called hyperbolic beta-meteoroids, which break apart from larger bodies through collision or sublimation in the near-sun region. These tiny particles can be propelled radially forward by solar radiation. Moreover, when fragmented small enough, they can also be deflected by electromagnetic forces. As previous research pictures a scenario of understanding the near-solar dust environment by multi-point measurements by PSP and future Solar Orbiter (SolO), we believe that it is crucial and worthwhile to conduct more in-depth studies of the nanodust dynamics in the near-sun region. Therefore, in order to explore the charged nanodust sources, distributions, and their potential impacts on objects within the inner solar system, such as spacecraft and planets, here we conduct a comprehensive survey of the charged nanodust behavior during the rising phase of the Solar Cycle 24, based on a 3D SIP-AMR-CESE MHD solar-wind model. This work could also be beneficial in preparing for future, more detailed analyses of PSP and SolO observations.
ST14-A006
| Invited
Modeling CME-driven Shocks Through an Inhomogeneous Solar Wind: Challenges and Future Improvements
Meng JIN1#+, Nariaki NITTA2, Christina COHEN3
1Lockheed Martin Advanced Technology Laboratories, United States, 2Lockheed Martin Solar and Astrophysics Laboratory, United States, 3California Institute of Technology, United States
In the past decade, significant efforts have been made in developing physics-based solar wind and coronal mass ejection (CME) models, which have been or are being transferred to national centers (e.g., SWPC, CCMC) to enable space weather predictive capability. However, the input data coverage for space weather forecasting is extremely limited. One major limitation is the solar magnetic field measurements, which are used to specify the inner boundary conditions of the global magnetohydrodynamic (MHD) models. In this study, by using the Alfven wave solar model (AWSoM) to simulate a realistic solar eruptive event on 2013 April 11, we demonstrate that due to the inhomogeneous background solar wind and dynamical evolution of the CME, the CME-driven shock parameters change significantly both spatially and temporally as the CME propagates through the heliosphere. The input magnetic map has a great impact on the shock connectivity and shock properties in the global MHD simulation. Therefore this study illustrates the importance of taking into account the model uncertainty due to the imperfect magnetic field measurements when using the model to provide space weather predictions. In addition, we discuss strategies to improve model performance, especially by incorporating newly available state-of-the-art in-situ and remote-sensing observations.
ST14-A007
On the Activities in the Lower Corona Associated with the Formation of a Streamer Blob
Li HAIYI#+, Zhenghua HUANG, Lidong XIA, Hui FU, Deng KAIWEN, Hengyuan WEI, Zhang CHAO
Shandong University, China
Small-scale propagating blobs in helmet coronal streamers could be an important source of the slow solar wind. They are widely believed to be results of magnetic reconnection between open and close magnetic field. However no direct observations has been reported to either support or deny such mechanism. Using observations from SUVI/GOES and AIA/SDO, here we study precusors of a streamer blob as seen in the corona below 2.0 solar radii. We found that at altitudes below 2.0R the streamer blob was formed due to the gradual merging of three clumps of materials initiated from the lower corona. One of the clumps of materials may have been formed by the expansion and stretching of the loop structure at the base of the helmet coronal streamer. The other two clumps of materials may have been formed by the swing of the loop structure in the north-south direction in the base of the helmet streamer. In these observations, we do not observe reconnection between loops and open field lines. We raise a question whether magnetic reconnection actually occurred to drive the observed streamer blob. We also propose a possible mechanism to interpret the formation of this event. These observations might help us understand small-scale transients that frequently found in the solar wind near the sun.
ST14-A013
| Invited
Three-dimensional Anisotropy and Scaling Properties of Solar Wind Turbulence at Kinetic Scales in Inner Heliosphere: Parker Solar Probe Observations
Jian ZHANG1+, Shiyong HUANG1#, Jiansen HE2, Tieyan WANG3, Zhigang YUAN1, Xiaohua DENG1, Kui JIANG1, Yunyun WEI1, Sibo XU1, Qiyang XIONG1, Rentong LIN1, Lin YU1
1Wuhan University, China, 2Peking University, China, 3Yunnan University, China
We utilize the data from Parker Solar Probe (PSP) mission at its first perihelion to investigate the three-dimensional (3D) anisotropies and scalings of solar wind turbulence for the total, the perpendicular and the parallel magnetic-field fluctuations at kinetic scales in the inner heliosphere. By calculating the five-point second-order structure functions (SFs), we find that the three characteristic lengths of turbulence eddies for the total and the perpendicular magnetic-field fluctuations in the local reference frame (LPerp, lPerp, l||) defined with respect to local mean magnetic field Blocal feature as l||>LPerp>lPerp in both the transition range and the ion-to-electron scales, but l||>LPerp~lPerp for the parallel magnetic-field fluctuations. For the total magnetic-field fluctuations, the wavevector-anisotropy scalings are characterized by l||~lPerp0.78 and LPerp~lPerp1.02 in the transition range, and they feature as l||~lPerp0.44 and LPerp~lPerp0.73 in the ion-to-electron scales. These observational results need more complete kinetic-scale turbulence model to account for.
ST14-A017
Radial Evolution of the Wavelike Compressional Turbulence in the Inner Heliosphere
Jiansen HE1#+, Die DUAN1, Xingyu ZHU2, Daniel VERSCHAREN3, Trevor BOWEN4, Bale STUART4
1Peking University, China, 2The University of Alabama in Huntsville, United States, 3University College London, United Kingdom, 4University of California, Berkeley, United States
The quasi-radial alignment between Parker Solar Probe (PSP) and other spacecraft further away from the sun provides a great opportunity to observe the radial evolution of the wavelike compressional turbulence from the inner heliosphere near the solar corona to the near-earth environment. We choose the 4th and 11th encounters of PSP with their respective perihelion distances of ~30 Rs and 13 Rs away from the sun to address this issue. Similar time profiles of solar wind variables' changes are observed from both PSP and Wind (at 1 au) measurements. The accelerating-solar-wind model could be more suitable than the constant speed model for the observation, which means the solar wind is still accelerating from the perihelion distance (e.g., 30 Rs) to 1 au. Both PSP and Wind measure the co-existence of the Alfvenic and compressive fluctuations in the solar wind. It is interesting to note that the good correlation between radial velocity component (dVR), proton density (dn) and temperature (dT) fluctuations indicate the nature of the compressive fluctuations are outward-propagating slow-mode waves. However, dn and d|B| is well not correlated for PSP measurements, but in good correlation for Wind measurements, which indicates the propagating direction of the slow-mode waves is evolving along the distance from the quasi-parallel direction to the quasi-perpendicular direction. Comparing the radial evolution of the energies of both Alfvenic and compressive fluctuations with the WKB model, we find the observed energy decays slower than the theoretical prediction, which indicates the existence of extra energy injection and energy cascade during the solar wind expansion.
ST14-A018
Scaling Anisotropy with Stationary Background Field in the Near-sun Solar Wind Turbulence
Honghong WU1#+, Jiansen HE2, Shiyong HUANG1, Li-Ping YANG3, Xin WANG2, Zhigang YUAN1
1Wuhan University, China, 2Peking University, China, 3Chinese Academy of Sciences, China
The scaling of magnetic fluctuations provides crucial information for the understanding of solar wind turbulence. However, the observed magnetic fluctuations contain not only turbulence but also magnetic structures, leading to the violation of the time stationarity. This violation would conceal the true scaling and influence the determination of the sampling angle with respect to the local background magnetic field. Here, to investigate the scaling anisotropy, we utilize an easy but effective criterion $\phi<10^\circ$ to ensure the time stationarity of the magnetic field, where $\phi$ is the angle between the two averaged magnetic fields after cutting the interval into two halves. We study the scaling anisotropy using higher-order statistics of structure functions \textbf{under the condition of stationarity} for the near-Sun solar wind turbulence for the first time based on measurements obtained from Parker Solar Probe (PSP) at 0.17 au. We find that the scaling indices $\xi$ of magnetic field show a linear dependence on the order $p$ close to $\xi(p)=p/4$. The multifractal scaling of magnetic-trace structure functions becomes monoscaling close to $\xi(p)=p/3$ with the local magnetic field perpendicular to the sampling direction and close to $\xi(p)=p/4$ with the local magnetic field parallel to the sampling direction when measured with the stationary background magnetic field. The scaling of velocity-trace structure functions has similar but less significant changes. The near-Sun solar wind turbulence displays different scaling anisotropies with the near-Earth solar wind turbulence, suggesting the evolution of the nonlinear interaction process during the solar wind expansion.
ST14-A019
Observations of Preferential Heating and Acceleration of Solar Wind Alpha Particles in the Inner Heliosphere
Jingyu PENG1#+, Jiansen HE1, Xingyu ZHU2, Ziqi WU1, Die DUAN1
1Peking University, China, 2The University of Alabama in Huntsville, United States
Remote sensing of the nascent solar wind in the solar corona shows that heavy ions can be faster and hotter simultaneously than protons. While in situ detection of the near-Earth solar wind illustrates that hotter and faster states of heavy ions than protons do not happen simultaneously. So it is curious what happens to the heating and acceleration of heavy ions in the inner heliosphere. The answer would also be helpful for understanding the mechanisms for the preferential heating and acceleration of heavy ions and its competition with another important physical process, Coulomb collisions. Specifically, what is the spatial extent of the zone of preferential heating and acceleration for heavy ions? Although it is speculated to start from less than one solar radiu above the solar surface and continue to tens of solar radii, the hypothesis is not yet observationally examed. Parker Solar Probe is currently the closest spacecraft to the Sun and is highly anticipated to cross the outer boundary of the preferential heating and acceleration zone and provide additional clues to the related mechanisms. Using observations from Parker Solar Probe, we find that larger α-proton drift speeds in the solar wind correspond to larger α-proton temperature ratios close to the corona. This feature differs from in situ detections farther from the Sun (e.g., Helios, Wind at 0.3~1AU). Collisions and instabilities may be responsible for this radial evolution of the α-particle properties in the solar wind. In addition, we try to identify the outer boundary of the preferential heating and acceleration zone. We find that preferential heating is weaker than the effect of cooling due to collisions, with no significant preferential heating zone observed. We also find that the preferential acceleration is obvious within 0.16 au, which may correspond to the preferential acceleration zone.
ST14-A020
Kinetic Effects of Alpha Proton Participation on the Turbulence Decaying
Qiyang XIONG+, Shiyong HUANG#
Wuhan University, China
Turbulence is acknowledged to exist extensively in the space plasma environments, functioning on the mass transferring, particles heating, and energy dissipation. The alpha particles can have an extensive detection in the turbulent solar wind and planetary space with various accumulated density. Whether the alpha species have the same kinetic impact on the turbulence with different participation ratios has not been fully addressed. In the present study, we investigate the kinetic effects of the alpha protons on the turbulence evolution by full kinetic particle-in-cell (PIC) simulations. Six run cases in total are performed with different proton-to-alpha density ratio. It is revealed that the anisotropy and the heating efficiency of both the protons and alpha particles are changed as the proportion of the alpha particle increases. The ion-alpha differential flow plays the essential part in the anisotropic heating, and its effect varies as the alpha particle density changes. These features are also distinguishable between the time of peak magnetic field energy and the time of later decaying. Our results are significant in building the fundamental of studying the astrophysical turbulence with complicate plasma composition.
ST14-A022
The Three-dimensional Reconstruction of Transients in the Outer Corona by the CORAR Technique Based on Multi-view Observations from STEREO
Shaoyu LYU+, Yuming WANG#, Xiaolei LI, Quanhao ZHANG
University of Science and Technology of China, China
Based on the simultaneous white-light observations of STEREO twin spacecraft, we proposed the CORrelation-Aided Reconstruction (CORAR) technique to locate and reconstruct the three-dimensional (3D) structures of solar wind transients in the interplanetary space. For the study of transients in the outer corona, we apply the CORAR method on synthetic and real images of COR-2 onboard STEREO. By comparing the reconstruction quality and precision of synthetic transient blobs under various conditions, we find that transients are generally reconstructed well when the separation angle between two spacecraft (θSun) is between 120◦ and 150◦, and the optimal θSun for reconstruction is close to 135◦. Based on the conclusion, we study the 3D reconstruction and evolution of real small-scale transients observed by COR-2 during Jan 2010 - May 2010. The valid transients are automatically detected according to the velocity uncertainty and image comparison. We confirm that the transients can be located and reconstructed well by comparing reconstructed structures with the corresponding transients fitted by the self-similar expanding model. The reconstructed transients generally have the typical acceleration characteristic of slow solar wind, which fits the trans-coronal radio observation and the previous researches of blobs. Most transients are located near the top of streamer belts, and can be traced into the boundaries of coronal holes or open-field regions on the photosphere. It supports the opinion that the slow solar wind originates from the interchange magnetic reconnection between open and closed field.
ST14-A031
Jet-flow Fluctuations and Plasma Blobs as a Mediator Between Interchange Mangetic Reconnection in Solar Corona and Alfvénic Velocity Spikes in Interplanetary Space
Chuanpeng HOU1+, Alexis ROUILLARD2#, Jiansen HE1, Bahaeddine GANNOUNI2, Victor REVILLE2
1Peking University, China, 2Institute for Research in Astrophysics and Planetology/ Université Toulouse III—Paul Sabatier/ National Center for Scientific Research/ National Center for Space Studies, France
Solar Orbiter (SolO) detects many Alfvénic velocity spikes in the solar wind at solar distances of nearly 0.38 au. It remains inconclusive about these spikes' origin, properties, and impact on the background solar wind. Some of these Alfvénic spikes show decreasing radial magnetic field (Br) and nearly constant magnetic field strength (|B|), similar to the kink/switchbacks observed by Parker Solar Probe in the near-sun solar wind (<0.3au). Other spikes show reducing radial magnetic fields, decreasing magnetic field magnitude, and increasing density and temperature, presenting the characteristics of pressure-balanced structures. Using a two-step ballistic backmapping method, we trace the Alfvén velocity spikes observed by SolO back to the boundary of a coronal hole at low latitudes. We find that the number of bright points near the coronal hole boundary shows a periodic fluctuation, which period is comparable to the waiting time of velocity spike clusters. Among these coronal bright points, there occurs one typical interchange magnetic reconnection event, which is recorded by EUI aboard SolO and AIA aboard Solar Dynamics Observatory. With the imaging with high temporal and spatial resolution from multiple perspectives, we directly analyze the dynamic properties of plasma blobs and the fluctuating motion of jet flow materials. We compare these observational analysis results with a 2.5D MHD simulation of interchange magnetic reconnection. We speculate that plasma blobs and outward fluctuations may act as a kind of mediator between interchange magnetic reconnection and the formation process of velocity spikes/magnetic switchbacks.
ST14-A032
Generation of Flux Ropes in the Small-scale Interchange Magnetic Reconnection Process Observed by Solar Orbiter
Chuanpeng HOU1+, Alexis ROUILLARD2#, Jiansen HE1
1Peking University, China, 2Institute for Research in Astrophysics and Planetology/ Université Toulouse III—Paul Sabatier/ National Center for Scientific Research/ National Center for Space Studies, France
Parker Solar Probe has detected abundant magnetic inversions and velocity spikes in the young solar wind, the origins of which are still highly debated. Numerous studies based on observational data and numerical simulations favor the causal correlation between the interchange magnetic reconnection process and these velocity spikes. However, the specific process by which interchange magnetic reconnection leads to these structures is still inconclusive. Some simulation works consider flux ropes, which they think may propagate into interplanetary space after generating from reconnecting current sheet, to be responsible directly for the observed magnetic inversions and velocity spikes. However, some other simulation works of interchange reconnection show that the flux ropes will reconnect with the post-reconnected open field lines and excite multi-wave modes. In this work, we show imagery observations of an interchange magnetic reconnection event and the motion of relevant flux ropes. Based on the high-resolution images (HRI) of Solar Orbiter/EUI, we analyze the dynamic process of flux ropes, the interaction between flux ropes and surrounding field lines, and the amplitude of wave modes near the cusp region of the interchange magnetic reconnection. Our analysis will provide an observational constraint on the numerical simulation of interchange magnetic reconnection and the interpretation of corresponding simulational results.
ST15-A005
A Comparative Study on the Polar Cap Hot Patch and Cold Patch by Using Multi-instrument Observations
Yu-Zhang MA1+, Qing-He ZHANG2,1#, Larry LYONS3, Kjellmar OKSAVIK4, Zanyang XING1, Marc HAIRSTON5, Balan NANAN1, Yong WANG1
1Shandong University, China, 2National Space Science Center, Chinese Academy of Sciences, China, 3University of California, Los Angeles, United States, 4University of Bergen, Norway, 5The University of Texas at Dallas, United States
Polar cap hot patch is a newly identified enhanced density structure which is associated with particle precipitation, ion upflow and flow shears. Based on combined observations from DMSP satellites, EISCAT radar, and all-sky imagers at the Chinese Yellow River Station, the different characteristics between hot patch and classical polar cap patch (cold patch) are investigated. Poleward moving auroral forms (PMAFs) and throat aurora are observed equatorward of both types of patches, which are located in narrow anti-sunward flow regions that are surrounded by sunward flow. Compare to the cold patch, the hot patch is closer to the cusp region and is associated with strong auroral emissions. Both hot and cold patches show enhanced F region density, but the hot patch is associated with higher electron temperature and enhanced E region electron density, which may due to the particle precipitation. We suggest that the hot patch and cold patch may represent different states of the same density structure, and the difference between them may be due to the decay of particle precipitation when patches move from cusp region to polar cap.
ST15-A012
A Statistical Study of Space Hurricanes in the Northern Hemisphere
Sheng LU1+, Zanyang XING1#, Qing-He ZHANG2,1, Yongliang ZHANG3, Yu-Zhang MA1, Xiang-Yu WANG1, Kjellmar OKSAVIK4, Larry LYONS5, Balan NANAN1, Jing LIU1, Yong WANG1, Zhong-Xin DENG6, Kai XIA1, Di SONG1
1Shandong University, China, 2National Space Science Center, Chinese Academy of Sciences, China, 3Johns Hopkins University Applied Physics Laboratory, United States, 4University of Bergen, Norway, 5University of California, Los Angeles, United States, 6China Research Institute of Radiowave Propagation, China
The space hurricane is a newly discovered large-scale three-dimensional magnetic vortex structure that spans the polar ionosphere and magnetosphere. At the height of the ionosphere, it has strong circular horizontal plasma flow with a nearly zero-flow center, and a coincident cyclone-shaped aurora caused by strong electron precipitation associated with intense upward magnetic field-aligned currents. By analyzing the long‐term optical observation onboard the Defense Meteorological Satellite Program (DMSP) F16 satellite from 2005 to 2016, we found that the space hurricane in the Northern Hemisphere occurs in summer and has a maximum occurrence rate in the afternoon sector around solar maximum. In particular, the space hurricanes are more likely to occur in the dayside polar cap at magnetic latitude greater than 80°, and their MLT (magnetic local time) dependence shows a positive relationship with the IMF (interplanetary magnetic field) clock angle. We also found the space hurricane occurs mainly under dominant positive IMF By and Bz and negative Bx conditions. It is suggested that the stable high-latitude lobe reconnection, which occurs under the conditions of large Earth’s dipole tilt angle and high ionosphere conductivity in summer, should be the formation mechanism of space hurricanes. The result will give a better understanding of the solar wind-magnetosphere-ionosphere coupling process under northward IMF conditions.
ST16-A003
Forward Modeling of Magnetic Field Measurements at the Bases of Stellar Coronae Through Extreme-ultraviolet Spectroscopy
Xianyu LIU1#+, Hui TIAN1, Yajie CHEN2, Wenxian LI3, Meng JIN4, Xianyong BAI3, Zihao YANG1
1Peking University, China, 2Max Planck Institute for Solar System Research, Germany, 3Chinese Academy of Sciences, China, 4Lockheed Martin Advanced Technology Laboratories, United States
Measurements of the stellar coronal magnetic field are of great importance in understanding the stellar magnetic activity, yet the measurements have been extremely difficult. Recent studies proposed a new method of magnetic field measurements based on the magnetic-field-induced-transition (MIT) of the Fe x ion. Here we construct a series of stellar coronal magnetohydrodynamics (MHD) models and synthesize several Fe x emission lines at extreme-ultraviolet wavelengths, and then diagnose the magnetic field strength at the bases of the coronae using the MIT technique. Our results show that the technique can be applied to some stars with magnetic fields more than three times higher than that of the Sun at solar maximum. Furthermore, we investigate the uncertainty of the derived magnetic field strength caused by photon counting error and find that a signal-noise ratio of ∼50 for the Fe x 175 ̊A line is required to achieve effective measurements of the stellar coronal magnetic field.
ST16-A004
Where and How Does a Decay-index Profile Become Saddle-like?
Runbin LUO+, Rui LIU#
University of Science and Technology of China, China
The decay index of solar magnetic fields is known as an important parameter in regulating solar eruptions from the standpoint of the torus instability. In particular, a saddle-like profile of decay index, which hosts a local torus-stable regime at higher altitudes than where the decay index first exceeds the instability threshold, is found to be associated with some confined or two-step eruptions. To understand the occurrence of such a profile, we employed dipoles to emulate different kinds of photospheric flux distributions. Corroborated by observations of representative active regions, our major results are as follows: (1) in bipolar configurations the critical height increases away from the AR center along the polarity inversion line (PIL) and its average is roughly half of the centroid distance between opposite polarities; (2) in quadrupolar configurations saddle-like profiles appear above the PIL when the two dipoles oriented in the same direction are significantly more separated in this direction than in the perpendicular direction, and when the two dipoles are oriented differently or have unequal fluxes; and (3) saddle-like profiles in quadrupolar configurations are associated with magnetic skeletons such as a null point or a hyperbolic flux tube, and the role of such profiles in eruptions is anticipated to be double-edged if magnetic reconnection is involved.
ST16-A009
Magnetic Field Extrapolation in Active Region Well Constrained by Observations in Multiple Layers
Fu YU1,2+, Jie ZHAO1#, Xiaoshuai ZHU1, Yang GUO3, Yang SU1, Jinhua SHEN1, Hui LI1
1Chinese Academy of Sciences, China, 2University of Science and Technology of China, China, 3Nanjing University, China
Magnetic field extrapolation is an important tool to reconstruct the 3D magnetic field above the solar photosphere. However, the prevalently used force-free field model might not be applicable in the lower atmosphere with non-negligible plasma beta, where the crucial process of flux rope formation and evolution could happen. In this work, we perform extrapolation in an active region, based on an recently developed magnetohydrostatic (MHS) method which takes plasma forces into account.
By comparing the results with those from the force-free field extrapolation methods, we find that the overall properties, which are characterized by the magnetic free energy and helicity, are roughly the same. The major differences lie in the magnetic configuration and the twist number of magnetic flux rope (MFR). Unlike previous works either obtained sheared arcades or one coherent flux rope, the MHS method derives two sets of MFR, which are highly twisted and slightly coupled. Specifically, the result in the present work is consecutively constrained by the high-resolution observations from the chromosphere, through the transition region to the corona, such as the filament fibrils, pre-eruptive braiding characteristics and the eruptive hot channel.
Overall, our work shows that the newly developed MHS method is more promising to reproduce the magnetic fine structures that can well match the observations at multiple layers, and future data-driven simulation based on such extrapolation will benefit in understanding the critical and precise dynamics of flux rope before eruption.
ST16-A011
The Causes of Homologous Eruptions from NOAA AR 11302 Through the Data-constrained MHD Simulation
Wentai FU#+, Yang GUO, Mingde DING, Ye QIU, Ze ZHONG
Nanjing University, China
In this work, we obtain the coronal magnetic configuration for this region using a NLFFF extrapolation based on the photospheric magnetogram at 12:00 UT. Taking it as the initial condition, we perform a data-constrained MHD simulation to study the evolution of the magnetic topology for this region. We reproduce two homologous eruptions through MHD simulation, including a successful eruption and a confined eruption. By analyzing the magnetic null point and three-dimensional quasi-separatrix layers, we divide the magnetic structures into three magnetic ropes and two spine-fan structures. The observed flare ribbons and flare loops correspond to these magnetic structures, which further explains the reliability of our simulation. We also analyze the Lorentz force and decay index of the two eruptions. We find that torus instability plays a role in driving the successful eruption. After the successful eruption, due to the occurrence of magnetic reconnection, the direction of medium magnetic flux rope overlying magnetic field configuration has changed. Therefore, the direction of Lorentz force change to be downward, which makes the second eruption be confined.
ST16-A022
Solar Cycle Variation in the Properties of Photospheric Magnetic Elements
Song ANCHUAN1#+, Yuming WANG1, Quanhao ZHANG1, Rui LIU1, Jie JIANG2, Xiaolei LI1
1University of Science and Technology of China, China, 2Beihang University, China
Photosheric convective motions, energy transports, and eruption phenomena on the Sun, are inextricably related to solar magnetic field. The solar surface is widely covered with Magnetic Elements (MEs). We investigate physical properties of these MEs by analyzing magnetograms from 2010 to 2021 observed by Helioseismic and Magnetic Imager (HMI) on board Solar Dynamics Observatory (SDO). Utilizing “clumping” algorithm to identify MEs, we show that the distribution of MEs parameters follow the two segments power-law separated as small-scale and large-scale MEs. MEs with small-scale parameters (magnetic flux less than 5.5∗10^18 Mx or area less than 5.5 ppm or magnetic energy per unit depth less than 5.5*10^14 J/m) have almost no correlation with solar cycle but MEs with large-scale parameters have strong correlation with solar cycle. Meanwhile, the magnetic field strength (maximal value of MEs) versus area of MEs fit well with radical function. The fitting slope has strong correlation with solar cycle on all flux-scale MEs and almost no correlation with solar cycle on small flux-scale MEs. These implies large-scale and small-scale MEs are generated by different physical mechanisms.
ST16-A025
A Study of Pre-flare Solar Coronal Magnetic Fields: Magnetic Energy and Helicity
Aiying DUAN1#+, Chaowei JIANG2, Xueshang FENG3
1Sun Yat-sen University, China, 2Harbin Institute of Technology, China, 3Chinese Academy of Sciences, China
Solar flares fall into two types with eruptive ones associated with coronal mass ejection (CME) and confined ones without CME. To explore whether there are pre-flare conditions in terms of magnetic energy and helicity that can effectively determine the types of flares, here we analyzed a suite of related parameters of the reconstructed pre-flare coronal magnetic field of major solar flares, either eruptive or confined, from 2011 to 2017 near the solar disk center. The investigated parameters include the extensive-type quantities such as the total magnetic energy ET, the potential energy EP, the free energy EF, the relative helicity HR, and the non-potential helicity HJ, as well as the intensive-type indices EF/EP, |HJ/HR, |HR/phi'2| and |HJ/phi'2|, where phi' is half of the total unsigned magnetic flux. We have the following key findings: (1) None of the extensive parameters can effectively distinguish the eruptive and confined potential of the pre-flare coronal fields, though the confined events have averagely larger values; (2) All the intensive parameters have significantly larger average and median values for eruptive flares than the confined events, which indicates that the field for eruptive flares have overall higher degree of non-potentiality and complexity than that of the confined flares; (3) The energy ratio EF/EP and the normalized non-potential helicity |HJ/phi2|, which are strongly correlated with each other, have among the highest capability of distinguishing the fields that possibly produce a major eruptive or confined flare, as over 75\% of all the events are successfully discriminated between eruptive and confined flares by using critical values of EF/EP>=0.27 and |HJ/phi'2|>=0.009.
ST16-A026
Investigation Into the Stability of Magnetic Structure Producing Eruptive Flares in Solar Active Regions
Jihye KANG1#+, Satoshi INOUE2, Yong-Jae MOON1
1Kyung Hee University, Korea, South, 2New Jersey Institute of Technology, United States
We study a flare onset process in terms of stability of a three-dimensional (3D) magnetic field in several active regions, such as 12371, 11890, 12673, producing eruptive flares. In order to reveal the 3D magnetic structure, we first extrapolate the 3D coronal magnetic fields based on the photospheric vector magnetic fields under a nonlinear force-free field (NLFFF) approximation. The NLFFFs nicely reproduce the observed pre-eruptive magnetic configuration. Using the NLFFFs, we investigate the sheared arcade loops to explore the onset process of the eruptive flare using three representative magnetohydrodynamic(MHD) instabilities: the kink, torus, and double arc instabilities. Consequently, the NLFFFs are found to be quite stable against the kink and torus instabilities. We expect that the double arc instability is a key for understanding the onset process of the sheared arcade loops producing the eruptive flares. We also try to apply NLFFFs as the initial conditions to observation-based MHD models to reconstruct its process of the eruptive events.
ST16-A028
Twist and Writhe of the Eruptive Quiescent Filament on 2013 August 2
Yudi OU#+, Yingna SU
Chinese Academy of Sciences, China
Multi-wavelength observations of a filament eruption provide an opportunity to uncover the physical mechanism of the triggering and evolution process of the eruption. In this work, we investigate a quiescent filament that erupted on 2013 August 02, observed in H-alpha and EUV by SDO and GONG. At first, the eastern part of the filament starts to rotate in counterclockwise direction, then the western part of the filament shows clockwise rotation, finally the entire filament rises up and erupts. More interestingly, the filament shows two helical structures near its right footpoint during the eruption. We construct magnetic field models of this source region using the flux rope insertion method. The estimated twist number of the erupting flux rope based on the magnetic field model exceed the threshold value of kink instability, which suggests that kink instability might play a major role in the onset of the eruption. The critical height of torus instability increases from the eastern footpoint to the western footpoint of the filament, which may explain why the eruption begins at the eastern footpoint.
ST17-A008
Simultaneous Evolutions of Inner Magnetospheric Plasmaspheric Hiss and EMIC Waves Under the Influence of a Heliospheric Plasma Sheet
Nigang LIU#+
Sun Yat-sen University, China
Plasmaspheric hiss and electromagnetic ion cyclotron (EMIC) waves are two of the most important magnetospheric plasma waves inside the Earth's high-density plasmasphere. In this work, utilizing observations from the WIND and Van Allen Probes missions, we investigate the simultaneous evolutions of inner magnetospheric plasmaspheric hiss and EMIC waves under the influence of a heliospheric plasma sheet (HPS). The long duration impingement of high-density solar wind HPS onto the magnetosphere produced hot anisotropy electrons and protons, and then caused excitations of plasmaspheric hiss and EMIC waves in the duskside plasmasphere (L ∼ 6.75, MLT ∼ 16.85). In contrast, the solar wind decompression associated with the subsequent cessation of the HPS led to decreases in hot electron and proton fluxes, triggering prompt disappearances of the compression-related plasmaspheric hiss and EMIC waves. The presented results highlight the importance of solar wind conditions for the Earth's space weather and provide new insights into the solar wind-magnetosphere coupling.
ST17-A011
A Statistical Study of Superfast Precipitation of Energetic Electrons Observed by POES Satellites
Zheng XIANG#+, Deyu GUO, Binbin NI, Yangxizi LIU, Junhu DONG
Wuhan University, China
Energetic electron precipitation plays an important role in the magnetosphere-ionosphere-atmosphere coupling system, leading to chemical and electric effects in the upper atmosphere. Based on the quasi-linear theory, the population of trapped electrons is always larger than the precipitated ones. However, recent observations from ELFIN-A satellite found that precipitation electron fluxes can often exceed the trapped electron fluxes. This phenomenon is called superfast precipitation and is likely caused by nonlinear electron interactions with intense plasma waves. To comprehensively investigate the spatiotemporal features of the superfast precipitation phenomenon under different magnetic storm levels, we conduct a statistical study of superfast precipitation using long-term observations from POES satellites. The results show that superfast precipitation mostly occurs in the region L>7 with the largest occurrence rate of ~15% at nightside. These results can help to identify the wave mode driving the superfast precipitation.
ST18-A002
New Empirical Model of Radiation Belt Energetic Electrons
Qianyi MA#+, Linghua WANG, Qiugang ZONG, Zhiyang LIU, Yongfu WANG
Peking University, China
The energetic electrons magnetically trapped in the Earth’s radiation belt can pose severe hazards to spacecraft and astronauts. In order to improve the forecast of spatial and temporal distributions of energetic electrons in terrestrial radiation belt, we develop a new empirical model with seven parameters: the electron energy, magnetic local time (MLT), magnetic latitude, L-shell, time, solar wind velocity and AE index, using the 50-600 keV energetic electron measurements by the Image Electron Spectrometer (IES) on board a Chinese Navigation Beidou satellite in an inclined (55°) geosynchronous orbit from 2015 to 2020. First, we build up a quiet-time radiation belt model of energetic electrons, based on a statistical study of energetic electron spectra observed by BD/IES during geomagnetic quiet times (Ma et al., in preparation). Secondly, we extend this quiet-time model to an all-time model by introducing a magnification factor Q as a function of the electron energy, the AE index, and MLT, based on a statistical study of energetic electron spectra observed by BD/IES during geomagnetic active times. Compared with the popular NASA’s AE-8 model, the adjusted coefficient (that quantifies the model prediction accuracy) of our model is improved from 0.35 to 0.88. We will also compare the prediction accuracy of our model with some popular physics-based radiation belt environment models (e.g., RBE in the SWMF).
ST18-A004
Solar Wind with Magnetic Fields and Energetic Particles (SOFIE): A Physics-based Model to Predict the Solar Energetic Particles
Lulu ZHAO#+, Igor SOKOLOV
University of Michigan, United States
Radiation hazards caused by solar energetic particle (SEP) events are of great concern for space exploration. SEPs are suggested to be accelerated to high-energy either by magnetic reconnection-driven processes in solar flares or by shocks driven by coronal mass ejections. SEPs can be accelerated up to tens of GeV, and the flux of >10 MeV protons could exceed their background level by several orders of magnitude. Protons of >150 MeV are very difficult to shield, and the sparsity and large variation of the SEP events make them difficult to predict. We present a data-driven and self-consistent SEP forecast model, SOFIE, to simulate the acceleration and transport processes of energetic particles using the Space Weather Modeling Framework (SWMF). In this model, the background solar wind plasma in the solar corona and interplanetary space is modeled by the Alfven Wave Solar-atmosphere Model-Realtime driven by the near-real-time hourly updated GONG magnetogram. In the background solar wind, the coronal mass ejections are launched employing the Eruptive Event Generator using Gibson-Low configuration by inserting a flux rope estimated from the free magnetic energy in the active region. The acceleration and transport processes are then modeled self-consistently by the multiple magnetic field line tracker. We will demonstrate the capability of SOFIE to make now-cast and forecast of solar energetic particles.
ST18-A005
Research on the Effect of Data Assimilation for Three-dimensional MHD Simulation of Solar Wind
Fang SHEN1#+, Hanke ZHANG1, Yi YANG2
1Chinese Academy of Sciences, China, 2National Space Science Center, Chinese Academy of Sciences, China
As an important part of space weather forecasting, the prediction of solar wind parameters in the near-Earth space is particularly significant. The introduction of data assimilation (DA) method can improve the reliability of numerical prediction. In this study, we use a three-dimensional (3D) magnetohydrodynamics (MHD) numerical model with Kalman filter to infer the impact of the DA on solar wind modeling. We use the 3D MHD numerical model with near-Earth in situ observations from the OMNI database to reconstruct solar wind parameters between 21.5 solar radii and 1 AU. The period from 2018 to 2021 is simulated, when the solar activity in the decay of the 24th solar cycle to the rising of 25th solar cycle. The numerical model generates two separate results, one without DA and one with DA directly performed on the model-only results. Statistical analysis of observed, modeled and assimilated solar wind parameters at 1 AU reveals that assimilating simulations provide a more accurate forecast than the model-only results with a sharp reduction in the root mean square error and an increase of correlation coefficient.
ST18-A007
Automatic Recognition of Sunspot Based on Chinese Hα Solar Explorer
Huimin LI#+, Dalin YE, Lixin GUO
Xidian University, China
Sunspots are solar phenomena that occur in the solar sphere, and the overall situation of sunspots on the solar disk can reflect the level of solar activity. With the development and advancement of solar physics and observation technology, the automatic identification and feature extraction of sunspots has become a realistic requirement for studying solar activity. In this paper, the polynomial fitting method is used to remove the limb darkening effect from the CHASE images, and then threshold segmentation and mathematical morphology are combined for automatic identification of sunspots, and calculate the number and area of sunspots. In order to verify the accuracy of the method in this paper, the number and area of sunspots calculated from the CHASE were compared with the relevant parameters published by NOAA/SWPC. It was found that the calculation results had a good correlation with the SRS release. The results showed that for CHASE images, the method proposed in this paper could realize the automatic recognition of sunspots and obtain more accurate sunspot features, which is of great significance for the study of solar activity.
ST18-A009
Deep Learning Based Eruptive Flare Forecasting
Hemapriya RAJU#+, Saurabh DAS
Indian Institute of Technology Indore, India
Solar eruptions such as CMEs, flares disrupt geomagnetic and communication systems on Earth. While flares are abrupt, bright events that occur in the solar atmosphere and emit massive amounts of energy in the 10^28 to 10^32 erg range, CMEs are intense eruptions that hurl plasma into interplanetary space. CMEs can be found in conjunction with flares, filaments, or independent. Although both flares and CMEs are understood as triggered by a common physical process magnetic reconnection, yet, the degree of association is unknown. In this work, we study the time series of magnetogram data derived from SHARP (Space weather HMI Active Region Patches) to understand eruptive flare mechanism using Machine Learning models SVM,LDA and Deep learning model LSTM. Here, we use 18 SHARP parameters as input to our Machine Learning model from the year 2011-2021. The task here is to perform binary classification, hence two classes, predicting whether a flare will be accompanied by CMEs or not. We initially attempt to study the features at different time lags that will be more responsible for eruptive flare. For example, MEANSHR shows deviated mean between two classes at 48h time lag, while MEANGBZ shows it at 8-24h time lag before the event occurence. Therefore, we determine the appropriate time lag for each feature using our Deep Learning model LSTM, coupled with ML models SVM and LDA, to perform binary classification. We further attempt to study the model’s predictions and behaviour using Explainable ML methods such as variable-importance measure and shapley.
ST18-A014
The Equivalent Indices of Geomagnetically Induce Currents in Local Power Grid
Jin LIU#+
Yunnan University, China
The geomagnetic induced currents (GICs) generated in power grid by large-scale solar events may lead to electrical equipment damage and widespread power outages. So it is important to achieve effective GIC prediction and risk assessment for local grid. The Hilbert-Huang Transform (HHT) method is used to analyze the geomagnetic component and the GIC monitoring data. By extracting the GIC responses to storms, the equivalent disturbance indices is synthesized by instantaneous amplitude. In addition, the GIC potential risk of local power grid is evaluated comprehensively by considering the solar wind energy injection, dual-band geomagnetic disturbance and the GIC surge.
ST18-A015
Relationship of the Largest GIC During Geomagnetic Storms with Solar Wind-IMF Parameters
Balan NANAN1#+, Wen-Bin LI1, Ruth SKOUG2, Zanyang XING1, Manu VARGHESE1, Li-Kai LIANG1, Qing-He ZHANG3,1
1Shandong University, China, 2Los Alamos National Laboratory, United States, 3National Space Science Center, Chinese Academy of Sciences, China
The association of GIC (geomagnetically induced current) with various solar and geophysical conditions has been known. However, what determines the time of occurrence and amplitude of the largest GIC during geomagnetic storms, which during extreme storms can cause sudden damage of vulnerable utility systems, is not yet known. We address this important question by analyzing the GIC data measured in Finland for 21 years (1999-2019) during 106 geomagnetic activities (DstMin ≤-50 nT) at low, mid and high latitudes and the corresponding solar wind velocity V, dynamic pressure P and north-south component of interplanetary magnetic field (IMF Bz) measured using the ACE satellite, and the products VBz and PBz. The results show for the first time that the largest GIC (≥10 A) occurs at the time of the largest -(VBz) in all seasons and solar activity levels with its time determined by the time of the largest -Bz and magnitude determined by both V and -Bz, except in one case. The two power outages happened in the 21-year period (06 November 2001 and 30 October 2003) also occurred at the UT time of the largest GICmax. The correlation of largest GICmax is highest (0.92) with the largest -(VBz) at September equinox. The results highlight the importance of (1) measuring the solar wind velocity at the L1 point at high time resolution even under extreme space weather conditions, which with the existing instrument in the ACE satellite is not possible, (2) single station GIC measurements, and (3) the possibility of improving the forecasting of the rate of change of the local horizontal geomagnetic field (dH/dt) directly related to GIC.
ST18-A016
Double Superposed Epoch Analysis of Geomagnetic Storms and Corresponding Solar Wind and IMF in Solar Cycles 23 and 24
Manu VARGHESE1#+, Balan NANAN1, Qing-He ZHANG2,1, Zanyang XING1
1Shandong University, China, 2National Space Science Center, Chinese Academy of Sciences, China
The weakest solar cycle 24 (SC24, 2010-2019) in 100 years was 1/3rd less active compared to the previous solar cycle 23 (SC23, 1996-2009). We identify 135 and 61 ICME (interplanetary coronal mass ejection) driven clear geomagnetic storms (DstMin ≤-50 nT) in SC23 and SC24, respectively, giving a reduction of 55% storms in SC24, and present the double superposed epoch analysis (DSEA) of the storms/activities in SC23 and SC24 using the Dst, SymH, Kp and AE indices. The DSEA method for the corresponding solar wind velocity V, north-south component of the interplanetary magnetic field (IMF Bz) and the product VBz are also presented. Compared to SC23, the maximum storm/activity intensity in SC24 reduces by 52%, 12% and 45% at low, mid and high latitudes and the corresponding maxima in -VBz, V and -Bz reduce by 39%, 17% and 38%, respectively. The epoch average storm/activity intensity reduces by 27%, 11% and 4% at low, mid and high latitudes and average maxima in -VBz, V and -Bz reduce by 24%, 14% and 13%, respectively. The results seem to reveal that the average reduction in the main driver -VBz (~24%) might have caused nearly the same and equal average storm/activity intensity reductions in all latitudes (~25%), though the irregular nature of the AE index makes the reduction very small (4%) at high latitudes, and small (~11%) at mid latitudes mainly due to the small (0-9) quasi logarithmic scale of the Kp index.
ST18-A017
Spectral Analysis of Geomagnetically Induced Current and Local Magnetic Field During the 17 March 2013 Geomagnetic Storm
Zanyang XING1#+, Wen-Hao XU1, Balan NANAN1, Li-Kai LIANG1, Yan-Ling WANG1, Qing-He ZHANG2,1, Zi-Dan SUN1, Wen-Bin LI1
1Shandong University, China, 2National Space Science Center, Chinese Academy of Sciences, China
Geomagnetically induced current (GIC) is known to be closely related to the rate of change of local horizontal magnetic field (dBx/dt); and their spectra can give better insight into the relationship. We study the spectral characteristics of GIC measured in Finland and dBx/dt measured 30 km away during the 17 March 2013 intense geomagnetic storm (SymHMin = 132 nT). Two bursts of large GIC (up to 32A) and dBx/dt occurred at 16 UT and 18 UT during the storm main phase. For the first time, the cross wavelet transform (XWT) and wavelet coherence (WTC) techniques are used to investigate the correlation and phase relationship of GIC and dBx/dt in time-frequency domain. Their WTC correlation is strong (over 0.9) over the entire storm period, indicating dBx/dt is the main factor causing GIC. Their XWT spectra show two enclosed periods (8–42 min and 2–42 min) in the high energy region corresponding to the two bursts of activity in GIC and dBx/dt. Morever, we use continuous wavelet transform (CWT) and discrete wavelet transform (DWT) to analyze the spectral characteristics of GIC and dBx/dt. It is found that the CWT and DWT spectra of the two are very similar, especially in the low frequency characteristics, without continuous periodicity. Wavelet coefficients become large when GIC and dBx/dT are large; and the third-order coefficient, which corresponds to low-frequency part, best reflects the disturbance of GIC and dBx/dt.
ST18-A020
Global Model Output and Variable Reliability in Solar Wind Input
Ramon LOPEZ#+, Espen FREDRICK
The University of Texas at Arlington, United States
Global models of the geospace system use solar wind data as the outer boundary conditions of the simulations. The data are generally provided by the OMNI dataset, which takes observations in the solar wind (typically collected at the L1 Lagrange point), and ballistically propagates them to the bow shock. However, the actual solar wind conditions at Earth may at times be poorly correlated with the OMNI data. In this study we take two periods of OMNI data, one where the correlation between the OMNI data and data taken just outside the bow shock is good, and a period where the correlation is bad. The two time series for each period (the OMNI data and the near Earth solar wind data) are used to drive a global model and we compare the results to both observations to and to each other. This comparison will allow us to begin to quantify the range of potential error in the global model output as a function of solar wind input reliability, which is an important consideration for space weather prediction.
ST19-A003
Developing a New Technique to Identify Foreshocks
Huaizhong YU#+, Zeping LI
China Earthquake Networks Center, China
On average, more than 100 earthquakes of magnitude 6.0 and above occur in the world annually, of which about 15% have foreshocks. The existence of foreshocks may provide an opportunity for the prediction of the upcoming larger mainshocks. Unfortunately, the method to identify foreshocks has not been found yet. The detection of the potential of a larger event immediately after a moderate earthquake is still unresolved. In this work, we devised an approach to determine whether an earthquake is a foreshock to a larger mainshock by evaluating loading/unloading states. This is done by calculating the Coulomb fracture stress (CFS) change induced by earth tides along the tectonically preferred slip direction on the seismogenic fault surface of each of the candidates. The technique is based on the load/unload response ratio (LURR) method, but it can decide, not assume, the slip direction of CFS. Using the approach, we tested the Ms > 4.0 foreshocks of the Ms > 6.0 earthquakes on the Chinese mainland since 2000 and the earthquake swarms, where no subsequent larger mainshocks were expected, in the past 10 years. The former mostly occurred in the loading process, while the latter arose more frequently in a random process. The statistical results indicate that the occurrence of earthquakes during loading may imply the critical state of the seismogenic faults, and the derived stress is more likely to trigger a larger event than that of the earthquakes that occurred during unloading. This work has been supported by the Earthquake Joint Funds of NSFC (Grant No. U2039205) and the National Key Research and Development Project (Grant No. 2018YFE0109700).
ST19-A007
Estimations of the Number of Chinese Annual Seismic Hazard Region Based on R-score and Statistical Models
Zhengyi YUAN#+, Huaizhong YU
China Earthquake Networks Center, China
Some tentative studies are carried out on the number of Chinese annual seismic hazard region, aiming at giving the best estimation of which from the statistical point of view, and giving some reference to the practice of Chinese annual earthquake prediction. Firstly, formula for estimating the above number is derived by using R-score. Meanwhile, the traditional clustering algorithm is improved to identify the earthquake cluster areas that meet certain distance requirements. On this basis, the numbers of annual earthquakes above target magnitudes, earthquake cluster areas and isolated earthquakes in Mainland China during 1950 to 2019 are counted respectively. Finally, a variety of statistical models are fitted to determine the reasonable upper limit of the seismic hazard region number. Then results show that the estimation values obtained from the two statistical results are slightly different. The first value based on the annual incidence of earthquakes above MS5.5 in western (west of 108°E) and MS6.0 in eastern (east of 108°E) of Mainland China is 9, which is suitable for the prediction of earthquakes with slightly higher magnitudes, while the second one based on the cluster areas identification results of annual earthquakes above MS5.0 in Mainland China is 13, which is consistent with the number used by the China earthquake networks center at present, and has good application effect for determining annual earthquakes above MS5.0.This work has been supported by the National Key Research and Development Project of China (Grant No. 2018YFE0109700) and the Earthquake Joint Funds of NSFC (Grant No. U2039205).
ST19-A011
Spatiotemporal Evolutions of Large Earthquake Sequences in Tianshan Mountain Fault
Cheng CHANG#+, Chi-Chia TANG
China University of Geosciences, China
The foreshocks and aftershocks of large earthquakes provide valuable information for studying earthquake nucleation, fault rupture processes, and postseismic deformation. The Tianshan Mountain fault is a typical ongoing lithospheric deformation in an intracontinental setting. It formed during the accretion of the Altaids in the Paleozoic and was rejuvenated in the Cenozoic, and this might be a far-field response to the India-Asia collision. Tianshan Mountain fault is one of the most intense seismic areas in mainland China. In the past 20 years, there have been 13 earthquakes of Mw>5. To clarify evolutions of large earthquake sequences, we focused on the four large earthquakes with Mw>5.5 in the Tianshan region and used the matched filter technique to detect missing microearthquakes one month before and after the mainshocks. The newly detected events are at least three times more than that listed in the China Earthquake Networks Center catalog. The four large earthquakes have no foreshock sequence but have an Omori’s type decay with a logarithmic slope p~1. We found that aftershocks following Jinghe Mw6.3 earthquake migrated toward the west side while other aftershock sequences showed no evident migration. Geological structures around the mainshock hypocenters may affect the migration patterns of the aftershocks. Based on these phenomena, we attempt to describe the spatiotemporal evolution process and seismic properties of the mainshocks.
ST19-A013
Seasonal Variations of Parkinson Vectors
Zhiqiang MAO1+, Chieh-Hung CHEN1#, Aisa YISIMAYILI2
1China University of Geosciences, China, 2Earthquake Agency of Xinjiang Uygur Autonomous Region, China
Parkinson vector (or induction vector) is an effective indicator to investigate the underlying conductivity structures and pre-earthquake conductivity anomalies. Typically, the factors influencing Parkinson vectors (PVs) come from underground. Recently, the seasonal effects have been observed in the PVs. However, causal mechanisms of the seasonal effects on the PVs are not fully understood. In this study, we utilize ten years three-component geomagnetic data from 24 stations operated by the Geomagnetic Network of China to study the spatiotemporal characteristics of the PVs through vertical transfer function (VTFs). The analytical results show that the PVs exhibit seasonal variations that the magnitude of PVs reach maximum in summer and winter, which are pronounced in lower frequency bands. In addition, the PVs at all stations consistently exhibit a counterclockwise rotation in June (summer), and a clockwise rotation in December (winter). The Inter-hemispheric field-aligned current in the ionosphere is one of the potential reasons to explain the seasonal variations. This study finds that the PVs are also affected by ionospheric current systems. As a result, the seasonal effect on PVs should be examined when we study the pre-earthquake conductivity anomalies.
ST19-A014
Promising Anomalous Phenomena of Residing Waves Before Earthquakes
Chieh-Hung CHEN1#+, Yang-Yi SUN1, Xuemin ZHANG2, Kai LIN1
1China University of Geosciences, China, 2China Earthquake Administration, China
The instrumental array was established in Leshan, Sichuan, China for monitoring vibrations and perturbations in the lithosphere, atmosphere and ionosphere (MVP-LAI). Ground vibrations from the broadband seismometers, air pressure from the barometers, the magnetic field from the magnetometer, and total electron content from the ground-based Global Navigation Satellite System receivers retrieved from the MVP-LAI system share frequencies exceeding ~1 month before major earthquakes. Those geophysical parameters distributed from the Earth’s surface to the altitude of ~350 km suggest the existence of the LAI coupling before earthquakes. Meanwhile, the frequencies varies from low (~10-4 Hz) to high (~10-2 Hz or higher) with the approaching of the forthcoming earthquakes. The variable frequencies further suggest that seismo-waves reside in wide areas well covering the epicenters. The residing waves would be a promising candidate for predicting earthquakes.
ST20-A004
Results of the Wave Measurements by the WHU VLF Wave Detection System at the Chinese Great Wall Station in Antarctica
Xudong GU1#+, Binbin NI1, Wei XU1, Shiwei WANG1, Zejun HU2
1Wuhan University, China, 2Polar Research Institute of China, China
A Very Low Frequency (VLF) wave detection system has been designed at Wuhan University (WHU) and recently deployed by the Polar Research Institute of China at the Chinese Great Wall station (GWS, 62.22°S, 58.96°W) in Antarctica. With a dynamic range of ~110 dB and timing accuracy of ~100 ns, this detection system can provide observational data with a resolution to facilitate space physics and space weather studies. Located southwest and ~370 km from the Palmer station, the GWS site complements and provides new data for VLF wave studies using the Palmer station data. This paper presents the first results of the wave measurements by the WHU VLF wave detection system at GWS to verify the system's performance. With a three-month routine operation, the system can acquire the dynamic changes of the wave amplitudes and phases of various ground-based VLF transmitter signals emitted in North America and Europe. A preliminary analysis indicates that the properties of the VLF transmitter signals observed by the GWS wave detection system during the X-class solar flare events are consistent with previous studies. As the HWU-GWS path crosses the South Atlantic Anomaly (SAA) region, the observations also imply a good connection in space and time between the VLF wave disturbances and the lower ionosphere variation potentially caused by magnetospheric electron precipitation during the geomagnetic storm period. It is therefore well expected that the acquisition of VLF wave data at GWS, in combination with datasets from other instruments, can be beneficial for space weather studies related to the radiation belt dynamics, terrestrial lightning discharge, whistler wave propagation, and the lower ionosphere disturbance, etc., in the polar region.
ST20-A007
Statistical Analysis of Magnetosonic Waves in Plasmaspheric Plumes
Yun-Gi HAN+, Kyungchan KIM#
Chungbuk National University, Korea, South
Magnetosonic waves, also known as equatorial noise, are whistler-mode emissions distributed near the Earth’s magnetic equator between the proton cyclotron frequency and the lower hybrid resonance frequency. So far, much effort has been devoted to improving our understanding of their origin and characteristics inside and outside the plasmasphere, owing to their potential role in scattering energetic electrons and protons. In contrast, their characteristics in plasmaspheric plumes have not been reported yet. In this study, we, for the first time, statistically investigate magnetosonic waves in the plasmaspheric plumes based on the entire mission period (the year 2012-2019) of Van Allen Probes A and B. Statistical results show that magnetosonic waves are observed in plumes with an occurrence rate of ~10-20% depending on geomagnetic activity. Their amplitude and wave normal angle are distributed with an average of ~40 pT and 84o-88o, respectively. Increased geomagnetic activity enhances the amplitude and the ratio of plasma frequency to electron cyclotron frequency. In addition, approximately 80% of all selected magnetosonic wave events are observed simultaneously with the plasmaspheric hiss, which is known to be most effective in scattering electrons in the plume.
ST20-A010
Frequency Chirping of Chorus Subpackets in the Upstream and Downstream Regions
Huayue CHEN1#+, Xueyi WANG1, Lunjin CHEN2, Yoshiharu OMURA3
1Auburn University, United States, 2The University of Texas at Dallas, United States, 3Kyoto University, Japan
Chorus waves are electromagnetic emissions that are commonly detected in the Earth’s inner magnetosphere, which play a significant role in regulating electron dynamics, including the acceleration of electrons to ~MeV energies, and the precipitation of ~10 keV electrons into the ionosphere. These waves are believed to be excited in the upstream of the equator, with an amplitude enhancement in the downstream. The spectrum of chorus waves typically contains a series of discrete elements with an upward frequency chirping, known as rising-tone elements. In general, a chorus element is composed of several “subpackets” (or “subelements”), with a duration of about 5-10 ms. However, how the frequency chirps in the subpackets is still an open question. With a one-dimensional (1D) general curvilinear particle-in-cell (gcPIC) simulation in the dipole field at L=4, we investigate the frequency chirping of chorus subpackets. We find that the frequencies of subpackets have a comparable chirping rate with that of the entire chorus element in the upstream, but keep almost constant in the downstream. The mechanism of this kind of chirping has been further studied. Our study provides a fresh perspective on the theory of frequency chirping in chorus waves.
ST20-A017
Statistics of the Wave Normal Angle Distribution of Two-band Plasmaspheric Hiss
Junhu DONG+, Zheng XIANG#, Binbin NI
Wuhan University, China
The unique banded structure of plasmaspheric hiss has been recently reported by Ni et al (2023). Such banded hiss waves exhibit characteristically both an upper band above ~ 200 Hz and a lower band below ~150 Hz, with a gap in power in between. Using ~7-year datasets from Van Allen Probes, we establish a robust database of banded hiss events and investigate statistically the global wave normal angle (WNA) distribution for each band, along with which the statistical features of the wave amplitude for each band are also considered. Our results show that WNA of lower band hiss is smaller than that of upper band hiss, which suggests distinct generation mechanisms of two bands. Based on parameterization as functions L-shell, magnetic local time (MLT), magnetic latitude (MLAT) and geomagnetic (AE*) index, we also construct the empirical models of the wave amplitude and power-weighted wave normal angle of two-band plasmaspheric hiss, the results of which are further verified via data-model comparisons to show good performance.
ST20-A021
A Forecast Model of the Dst and AE Indices from Solar Wind Parameters Observed at the L-1 Point Based on Machine Learning Method
Hanyu HUANG1+, Zhengyang ZOU1#, Wentao ZHOU2
1Zhuhai MUST Science and Technology Research Institute, China, 2Macau University of Science and Technology, Macau
The Earth's magnetosphere is highly sensitive to the geomagnetic storms and substorms induced by kinds of interplanetary disturbances, such as CME and CIR events. Knowing the variations of the geomagnetic indices driven by solar winds could be an easy access to investigate magnetospheric physics. We present a machine learning approach to forecast Dst and AE indices based on the time series of more than 10 solar wind parameters observed on the L-1 point. The forecast result can well rebuild DST and AE evolutions during both geomagnetic and quiet times.
ST21-A001
Phase Space Density Hole/hill Formation by Whistler-mode Chorus in a Multi-component Plasma
Kyungguk MIN#+
Chungnam National University, Korea, South
Whistler-mode chorus waves in the inner magnetosphere are excited by a process involving phase trapping of energetic electrons in a dipole magnetic field. The critical element that gives rise to strong nonlinear wave growth is the formation of phase space density (PSD) hole which is asymmetric in gyro-phase space as a result of positive frequency chirping of chorus elements and the spatial gradient of the Earth’s magnetic field. Previous studies mainly assumed a two-component electron plasma where a cold dominant population provides a medium for wave propagation and a tenuous, anisotropic bi-Maxwellian or loss-cone distribution provides a necessary condition to form a PSD hole. On the other hand, earlier studies hinted that depending on the initial temperature anisotropy, either a PSD hole or hill can be formed. Then, a situation can arise where the presence of a relatively isotropic distribution can produce a PSD hill that counteracts the PSD hole produced by the anisotropic energetic bi-Maxwellian population, thereby reducing the nonlinear growth rate. In this paper, we expand the idea of the earlier studies and quantitatively show that phase-trapped particles by a rising tone element closely follow single wave characteristics. This indicates that the formation of PSD hole or hill is strongly related to the anisotropy of an initial distribution function. We suggest that the detailed structure in a realistic electron distribution far from an ideal single bi-Maxwellian can be important for chorus wave evolution.
ST21-A003
Revealing the Relationship Between Transpolar Arc Occurrence and Solar Wind Conditions Using the Novel Neural Network (Potential Learning): Initial Results
Motoharu NOWADA1#+, Ryozo KITAJIMA2, Ryotaro KAMIMURA3, Quanqi SHI1
1Shandong University, China, 2Tokyo Polytechnic University, Japan, 3Tokai University, Japan
Transpolar arcs (TPAs) are one of the interesting auroral phenomena that the bar-shaped emissions are growing from the poleward edge of the nightside main auroral oval to the dayside, occurred under northward and non-zero interplanetary magnetic field (IMF) conditions. Based on a novel machine learning algorithm: Potential Learning (PL), we reveal the relationship between high TPA occurrence rate and solar wind conditions, extracting the most significant solar wind parameter(s), closely related with the TPA appearance, from large databases of the OMNI solar wind and auroral image data from 1996 to 2005. PL is a neural network technique that can extract the most relevant parameter(s) to the output parameter among the input parameters. In this study, we set up the six solar wind parameters, such as the IMF-By and northward Bz components, solar wind velocity, number density, dynamic pressure, and solar wind energy coupling function, which is described with a formula proposed by Newell et al. (2007), as the PL input parameters. The output parameter of PL is the TPA presence/absence, represented with 1 or 0. Under these setup conditions, we examine the most significant solar wind parameter(s) when the output shows “1”. In this stage, we test the algorithm to evaluate the PL performance and confirm that the TPA appearance can be predicted with ~ 69.5% accuracy from input solar wind parameters. We will present the initial results on more detailed relationship between TPA occurrence and solar wind parameters, based on PL.
Reference:
Newell, P. T., Sotirelis, T., Liou, K., Meng, C.-I., and Rich, F. J. (2007), A nearly universal solar wind-magnetosphere coupling function inferred from 10 magnetospheric state variables, J. Geophys. Res., 112, A01206, doi:10.1029/2006JA012015.
ST21-A007
Layered Structure of Current Density Near Magnetic Equatorial Plane in the Inner Magnetosphere: Multi-spacecraft Observation
Xin TAN1, Malcolm DUNLOP1,2#+, Junying YANG1, Yanyan YANG3, Xiangcheng DONG4, Yingshuai DU1, Chris RUSSELL5
1Beihang University, China, 2Rutherford Appleton Laboratory, United Kingdom, 3China Earthquake Administration, China, 4Yunnan University, China, 5University of California, Los Angeles, United States
The Earth’s ring current forms a complex current system at the boundary of the inner magnetosphere. It is highly dynamic because of the interaction between the solar wind with the Earth's magnetosphere (the influence of space weather), while its morphology depends on the nature of the magnetospheric-ionospheric (M-I) coupling, generating field-aligned currents (FACs). Its behaviour can therefore have a huge impact on the terrestrial environment. According to Ampere's law, these currents can be directly measured by perturbations in the magnetic field using multi-spacecraft observation techniques. We have analyzed the magnetic field data from the four MMS spacecraft in their small-sale configuration to obtain the in-situ current density and have carried out statistical analysis from several years of data. The form of the current density distribution and its changing nature has been investigated. Our results show that the current density exhibits a three-dimensional layered structure in the ring current region. The significant westward current on the day side flows to higher magnetic latitudes and complete closure there rather than to the magnetic equator. There are some differences between geomagnetic quiet period and storm period on current density, but the basic spatial structure remains similar and compares well with previous space mission data. Comparison with Swarm data at low Earth altitudes, we found that the stratification is consistent with the distribution of the R2 field-aligned currents seen both adjacent to the ring current and at ionospheric altitudes (at Swarm). In addition, significant continuous eastward currents exist in some latitudes and some regions, indicating the complexity of the ring current. Some of them can be explained by the formation of banana currents.
ST21-A008
Solar Abundance Fractionation in an Active Region Related to the Existence of the Alfvén Wave in the Chromosphere
Kyoung-Sun LEE#+, Jongchul CHAE
Seoul National University, Korea, South
The elemental abundance in the solar corona is different from the photosphere. The fractionation between photospheric and coronal abundances is related to the “First Ionization Potential (FIP) effect.” In the corona, the low FIP (FIP < 10 eV) elements are enhanced by factors of 3–4 relative to the photospheric abundances. In contrast, the high FIP elemental abundance ratio to photospheric is approximately equal. Still, it is not revealed how the solar abundance is fractionated. Recently, the most probable model is “Abundance fractionation by the Pondermotive force”. The pondermotive force induced by the Alfvén wave preferentially affects the ionized elements (low FIP element), not the neutral in the chromospheric plasma, which is partially ionized. Then, the force drags up (or down) the low FIP elements depending on the Alfvén wave existence and their energy density in the chromosphere. For investigating the relations between the abundance fractionation and wave energy density in the chromosphere, we analyze the H alpha and Ca II data from GST/FISS for the Alfvén wave detection and Si X (low FIP element) and S X (high FIP element) spectra from Hinode/EIS for determining the relative abundance in an active region. We present the preliminary result of detecting Alfvén waves in the chromosphere compared to the spatial distribution of the abundance fractionation.
ST21-A017
Statistical Study of Mid- and Low-latitude Electric Field Response Corresponding to the CW Structure That Develops During Substorms
Moe HAYASHI1#+, Akimasa YOSHIKAWA1, Akiko FUJIMOTO2, Shin OHTANI3
1Kyushu University, Japan, 2Kyushu Institute of Technology, Japan, 3Johns Hopkins University Applied Physics Laboratory, United States
The purpose of this study is to comprehensively understand the evolution of global 3D current system from polar to equatorial ionosphere during substorms. There are two types of current systems in the polar ionosphere: the R1-current linked to the magnetospheric convection system, and the R2-current linked to the pressure gradient in the inner magnetosphere [Iijima and Potemra, 1976, 1978]. In addition to these currents, when substorms are occurred by strong plasma injections, current wedge (CW) is generated by the plasma vorticities at the edge of the plasma flow. They have the same current polarities as the R1-current system. Magnetic field generated by CW development are significant in the nightside mid- and low-latitude, and these variations was modeled by McPherron et al. [1973]. We capture the spatio-temporal development of CW during substorm by using MAGDAS and SuperMag magnetic field data. By comparing them with the electric field (E-field) from the FM-CW radar in Paratunka, Russia, we are analyzing the electromagnetic dynamic responses in the mid- and low-latitude. We performed a comparative analysis of ionospheric electric and geomagnetic fields for 50 of the 1790 isolated substorms from 09/21/2006 to 12/31/2010, in which the E-field changed significantly with onset. The results show that the amplitude of E-field is correlated with auroral electrojets (AEJ). Furthermore, the direction of E-field reflects E-field caused by the Hall polarization effect due to the ionospheric current induced by CW (simulated by Yoshikawa et al. [2013]), based on classification of the relative positions of the CW and observation points from mid-latitude geomagnetic data. However, similar analyses of the other 1,740 cases showed that these models alone could not explain the results. In this presentation, we report the results of our interpretation of E-field variations by comparing Kp and solar wind conditions in addition to substorm indices.
ST21-A019
SSUSI Aurora Forecast Model
Syau-Yun HSIEH#+, Yongliang ZHANG, Robert SCHAEFER, Larry PAXTON
Johns Hopkins University Applied Physics Laboratory, United States
The SSUSI Aurora Forecast Model has been developed and used to predict the global auroral quantities using the remote-sensing ultraviolet measurements from DMSP/SSUSI instruments. This model predicts the equatorward boundary of auroral oval and precipitating the electron energy flux and mean energy estimated based on the empirical GUVI global model for up to 1 day or 15 DMSP orbits in advance. We will present the current implementation, capability, validation and forecast results of this model and discuss the current/future development. Particle precipitation in the auroral oval serves as an important connection between the magnetosphere and ionosphere/atmosphere. Particle precipitation, an important source of energy for the high-latitude upper atmosphere, not only creates extra ionization in the high-latitude ionosphere which leads to absorption and disturbances in radio communication but also enhances the Joule heating by creating the Hall and Pedersen conductivity which alters the thermospheric convection and composition and further causes the global ionospheric disturbances. If we can accurately characterize the auroral region energy inputs and conductivity, we will have a better capability for nowcasting and forecasting the ionospheric conditions in the high latitude region for space weather.
ST21-A022
Radial Variations of the Heliospheric Current Sheet Tilt Angle During Solar Minimum Years: Magnetohydrodynamic Simulations
Chin-Chun WU1#+, Kan LIOU2
1U.S. Naval Research Laboratory, United States, 2Johns Hopkins University Applied Physics Laboratory, United States
Here we present results from a study of dynamic effects on the tilt angle (peak latitude) of the heliospheric current sheet (HCS) as a function of the heliospheric radial distance from ~0.08 to 15 AU using our time-dependent, three-dimensional, global magnetohydrodynamic (MHD) simulation model, G3DMHD. Specifically, we simulate solar wind during solar quiet years (1994-1995) to minimize effects from coronal mass ejections. We use the two years worth of photospheric magnetic field measurements from Mountain Wilson Observatory to drive the MHD model continuously and uninterruptedly. The locations of the HCS at different radial distances are derived from our simulation results and are compared with the tilt angle of the neutral line inferred from the potential field model at 2.5 Rs. Our results reveal a large peak in tilt angles in the northern hemisphere within 2 AU, suggesting steepening of the HCS. After 2 AU, the tilt angle reduces (e.g., flattening of the HCS) with the radial distance. In the southern hemisphere the trend mirrors those found in the northern hemisphere, forming near symmetric (about the equator) variations. We will present the results in detail and discuss possible causes of the HCS steepening and flattening.
ST21-A024
Extension of the Electron Density Enhancement from Middle to High Latitudes Observed by Swarm-A in Summer of the Southern Hemisphere
Jin WANG1#+, Yang-Yi SUN2, Tao YU2
1China University of Geosciences (Wuhan), China, 2China University of Geosciences, China
The major causal mechanism for the eastward movement of the electron density (Ne) enhancement associated with the southern Midlatitude Summer Nighttime Anomaly (MSNA) was attributed to the field-aligned thermospheric neutral wind at the middle geomagnetic latitude in the fixed local time coordinate. In the study, the Ne and horizontal cross-track ion drifts observed by the Swarm-A satellite at 462 km altitude show that the horizontal drifts can drive the Ne enhancement of the southern MSNA in the local summer of the Southern Hemisphere. Both the eastward and westward ion drifts transport the enhancement from the middle to the high geomagnetic latitudes, which results in the enhancement evolving at all the longitudes in the whole day.
ST21-A026
Two Distinct Brightness Distributions of Microwave Loop During an M-class Flare
Sujin KIM1#+, Jeongwoo LEE2, Satoshi MASUDA3
1Korea Astronomy and Space Science Institute, Korea, South, 2New Jersey Institute of Technology, United States, 3Nagoya University, Japan
We have studied the solar flare, SOL2013-10-28T02:01 (GOES class M9.1), with a sequence of microwave brightness maps obtained with the Nobeyama Radioheliograph (NoRH) at 17 GHz and 34 GHz. Hard X-ray maps from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) were also studied for the context. For the total six peaks of the bursts are counted in the microwave fluxes, the dominant microwave source appears to be dynamically changing its position within a simple loop oriented north-south near the limb. During the first three microwave flux peaks, the microwave source appears in the south while the X-ray source lies in the northern end of the loop. During the other three peaks, the opposite trend appears that the microwave source at the time of the peaks appears in the northern end while the X-ray source lies in the southern end of the loop. At the times between the peaks, the microwave intensity in the north substantially decreases while in the south, it changes little. Based on the results, we discuss the physical difference and the cause of two distinct brightness distribution of the microwave flare loop.
ST21-A030
An EUV Jet Driven by a Series of Transition Region Micro-jets
Hengyuan WEI1#+, Zhenghua HUANG1, Hui FU1, Ming XIONG2, Lidong XIA1, Zhang CHAO1, Deng KAIWEN1, Li HAIYI1
1Shandong University, China, 2National Space Science Center, China
Jets are one of the most common eruptive events in the solar atmosphere, and are believed to be important in the context of coronal heating and solar wind acceleration. We present an observational study on a sequence of jets with the data obtained from SDO and IRIS. This event includes an EUV jet, about 29 arcsec long with a dome-like base, a bundle of transition region (TR) flux ropes, and a series of transition region microjets. The bundle of flux ropes rises as a response to the TR microjets, with the rising motion eventually triggering the EUV jet. We propose a scenario involving a set of magnetic reconnections, in which the series of TR microjets are associated with the processes to remove the constraints to the TR flux ropes and thus allow them to rise and trigger the EUV jet. Our study demonstrates that small-scale dynamics in the lower solar atmosphere could be complex and are crucial in understanding the energy and mass connection between the corona and the lower solar atmosphere, even though many of them might not pump mass and energy to the corona directly.
ST21-A032
Automatic Recognition of Coronal Mass Ejection
Dalin YE#+, Huimin LI, Lixin GUO
Xidian University, China
Coronal Mass Ejection (CME) is a large-scale and the intense eruptive phenomenon, and also the main driving source of disastrous space weather, which is related to many phenomena such as flares, solar energetic particles, and geomagnetic storms. With the development and advancement of solar physics and observation technology, manual identification of CME can no longer efficiently process the rapidly increasing solar observation data, and automatic identification and feature extraction of CME has become a realistic requirement for studying solar activity. In this paper, the SOHO/LASCO C2 white-light images are preprocessed by running difference, threshold segmentation, and polar coordinate transformation, and then projected to obtain the intensity profile of the 1D projection along the angular and radial direction. Finally, the parameters of the central position angle, angular width, and speed of the CME are obtained by threshold segmentation and linear fitting. In order to verify the accuracy of the method in this paper, the central position angle, angular width, and speed calculated from 50 CME events in 2003 are compared with the corresponding parameters in the CDAW catalog, and it is found that the accuracy of CME feature extraction is 0.79. The results show that for SOHO/LASCO images, the method in this paper can realize the automatic identification of CMEs and obtain a more accurate description of the features, which is of great significance for the study of solar activity.
ST21-A033
Self-organized Criticality Characteristics and Statistical Studies of Flare Ribbons
Yue ZHANG+, Rui LIU#
University of Science and Technology of China, China
Each brightening distributed on the solar flare ribbons may be a small explosive reconnection event, and the single complex dynamic process can be regarded as a single avalanche. The UV (1600 and 1700) filter channel data of the Atmospheric Imaging Assembly (AIA) carried on the Solar Dynamics Observatory (SDO) are used to observe flare ribbons. We use morphological methods to deal with image data, thus flare ribbons can be extracted by setting a reasonable threshold and made as binary graphs convenient for the further statistical processing. It is expected that the duration, peak intensity, magnetic field, and dimming of the flare ribbon can be well described by power-law distribution functions. We explore the frequency distribution of each brightening’s physical parameters, and the distribution can be approximated with a power-law function. We find that the power-law index (i.e., the slope of the linear fitting part in the log-log graph, marked as index=average ± standard deviation) is insensitive to the threshold of flare ribbons identification (for Duration: αT=-1.5426±0.0050, for Peak intensity: αP=-1.4736±0.0561, for Line-of-sight magnetic field: αBz )=-1.4212±0.0132), which means these indices change little when the threshold changes. Since the idea of self-organized criticality (SOC) has been embodied in many natural phenomena, we attempt to explore the SOC characteristics within solar flare ribbons. And these results obtained can be explained as evidence of the existence of SOC in flare ribbons. In the future, we expect that there are also corresponding power-law relationships between different parameters, and deal with flares with other shapes or magnitudes to compare the characteristics of power-law presented by different flare ribbons.
ST22-A006
Correlation Study of the Variation in the Topside Ionosphere and F-region Along the Magnetic Field Line
Yen-Jung WU#+, Thomas IMMEL, Brian HARDING, Colin TRIPLETT, L. Claire GASQUE
University of California, Berkeley, United States
NASA's Ionospheric Connection Explorer (ICON) was launched in 2019 to investigate the interaction between the neutral atmosphere and the ionosphere. At altitudes in the F-region and below, ICON reports on various ionospheric quantities such as O+ profile, NmF2, and HmF2, as well as neutral wind, temperature, and disk O/N2. The Ion Drift Meter (IVM) on ICON, at an altitude of approximately 600 km, provides in-situ plasma measurements of the topside ionosphere. This study examines the relationship between daytime topside ion density and other ICON measurements on different time scales. The results show that disk O/N2 has the highest correlation with a value of 0.46 in the annual time scale. When the data is grouped by noontime equatorial crossings with a 14-day window size, the topside ion density has strong correlations with HmF2 and IVM's meridional drift, with mean correlations of 0.60 and 0.51, respectively. Furthermore, in the equatorial crossing groups, HmF2 has a significant positive correlation with NmF2 and field-aligned drift, while significant negative correlations are found with ion density and meridional drift. This exercise provides valuable information for developing a machine learning model that can estimate topside ion density and ion drift using measurements from lower altitudes.
ST22-A008
New Findings of Earth Ionosphere from Three Year Observations of FORMOSAT7-COSMIC2
Charles LIN1#+, P. K. RAJESH1, Jia-Ting LIN1, Chi-Yen LIN2, Shih-Ping CHEN1, Cheng -Yung HUANG3
1National Cheng Kung University, Taiwan, 2National Central University, Taiwan, 3National Space Organization, Taiwan
FORMOSAT7-COSMIC2 Mission consists of six satellites equipped with GNSS radio occultation payload, in-situ ion density and velocity meters, and RF beacon transmitters. The constellation launched in June 2019 is situated at the low inclination orbit of 24 degree and the radio occultation observations could cover up to 40 degree latitudes. As the operational mission takes ~5000 observations of occultations, plus 100% duty cycle of ion measurements, it provides an unprecedented opportunity to observe the three-dimensional ionosphere hourly. Taking advantage of this special design of the mission, we have discovered several exciting new phenomena during the three year period. In this presentation, we will show how the minor magnetic storm could create severe ionosphere effects; how the Antartica stratospheric sudden warming oscillated and modify the ionosphere plasma; how the mission help identify the super plasma bubble created by the gigantic volcano eruption. All these findings are very important to understand the ionosphere further.
ST23-A005
MHD Modeling of CMEs - Recconstructing Remote and In-situ Observations
Nishtha SACHDEVA#, Zhenguang HUANG+, Gabor TOTH, Ward MANCHESTER, Bart VAN DER HOLST, Aniket JIVANI, Hongfan CHEN
University of Michigan, United States
Successful modeling of solar transients like Coronal Mass Ejections (CMEs) is an important step towards accurately forecasting their space weather impact. It is therefore crucial to improve the models and tools to reconstruct CMEs by validating simulations with observations of the solar corona and the inner heliosphere at various heliospheric distances with multi-viewpoint observations. The Space Weather Modeling Framework (SWMF) includes MHD modeling of the solar wind and CMEs from the Sun to the Earth and beyond. The Alfven Wave Solar atmosphere Model (AWSoM) is a 3D extended-MHD solar corona model within SWMF that reproduces the solar wind background into which CMEs can propagate. The Eruptive Event Generator (EEG) module within SWMF is used to obtain flux-rope parameters to model realistic CMEs within AWSoM using different flux-rope configurations. In this work supported by the NSF SWQU and LRAC programs, we use an ensemble of solar wind backgrounds to obtain the best solar wind plasma environments into which CMEs can be launched. We vary the flux-rope parameters within a fixed range to do an ensemble of CME simulations to match the model reconstructed results with remote coronagraph observations near the Sun (LASCO C2/C3 and STEREO COR1/COR2) as well as with in-situ observations of solar wind plasma at 1 au. The ensemble modeling is a step forward towards improving the accuracy of the tools that provide flux-rope parameter estimates as well as the uncertainty quantification of CME modeling.
ST23-A007
The Dynamics of Turbulent Cascade Inside and Around ICME Propagating from the Sun
Maria RIAZANTSEVA1#+, Liudmila RAKHMANOVA1, Igor VOLODIN 2, Timofey TREVES 1, Alexander KHOKHLACHEV 1, Yuri YERMOLAEV1, Georgy ZASTENKER3
1Space Research Institute of the Russian Academy of Sciences, Russian Federation, 2HSE University, Russian Federation, 3Russian Academy of Sciences, Russian Federation
The study is devoted to the dynamics of the turbulent cascade inside and around ICMEs based on multipoint measurements of Wind, Spektr-R, Themis at the Earth orbit and Parker Solar Probe or Solar Orbiter closer to the Sun. Both case study and statistical analysis of turbulent properties in different positions in the heliosphere are performed. The ICMEs are selected with the help of the catalog of large-scale structures http://iki.rssi.ru/pub/omni/catalog/. Only data intervals with the best temporal resolution are used, which makes it possible to estimate the dynamics of the turbulent cascade on the ion-kinetic scales. As a rule, fast measurements are available only for interplanetary magnetic field. However, high-resolution plasma measurements on Spektr-R are also used for comparison with other spacecraft and for the statistical analysis. Comparison of magnetic field magnitude and ion flux fluctuations is possible as fluctuations of both quantities represent compressive fluctuations. Results reveal that typically fluctuation spectra have shape similar to the predictions of turbulence models in the undisturbed solar wind before ICME, become steeper at the kinetic scales in the Sheath region before of the ICME and tend to restore to the initial shape inside the ICME. It was shown also that the shape of the turbulent cascade can conserved both at the MHD and at the kinetic scales from the Sun to the Earth, while the fluctuation power decreases when moving away from the Sun. Plasma structures responsible for the steepening of the spectra at the kinetic scales and the enhancement of dissipation in the Sheath region are discussed. The work is supported by Russian Science Foundation grant № 22-12-00227.
ST23-A009
Helium Abundance Behavior in the ICMEs During Solar Activity Decrease in 23-24 Solar Cycles
Alexander KHOKHLACHEV 1#+, Yuri YERMOLAEV1, Irina LODKINA2, Maria RIAZANTSEVA1, Liudmila RAKHMANOVA1
1Space Research Institute of the Russian Academy of Sciences, Russian Federation, 2Russian Academy of Sciences, Russian Federation
The ICMEs are statistically characterized by the increase of average values of the relative abundance of doubly ionized helium ions. In this study we investigate the changing of the behavior of the helium abundance inside the ICMEs during the significant decrease in solar activity in 23-24 solar cycles. The change in solar activity observed in 23-24 solar cycles is widely discussed in recent years. One of the effects of activity decline is a decrease in the average values of the plasma and interplanetary magnetic field parameters, including the helium abundance (Yermolaev et al., JGR, 2021). Based on the hourly average data from the OMNI database, we consider changes in the helium abundance vs other solar wind parameters in two epoch of different solar activity. These epochs cover two periods - 21 and 22 solar cycles, when solar activity was high, and 23-24 cycles, when solar activity decreased significantly. In addition to the interplanetary magnetic field and solar wind plasma parameters, we analyzed the distance between the observation point and the ICME axis. The results of the statistical analysis show that the relative helium abundance increases in the ICME central region in comparison to the peripheral. This dependence is observed in both epochs of solar activities. An increase in the helium abundance near the center of the ICME confirms the hypothesis about the existence of a helium-enriched electric current near the ICME axis, suggested in the paper (Yermolaev et al., JGR, 2020). The dependences of the helium abundance on the magnetic field magnitude and the plasma beta parameter, which was shown at previous stage (Khokhlachev et al., Cosmic Research, 2022) and also confirm the above hypothesis, tend to conserve during the change of epochs. The work is supported by Russian Science Foundation grant № 22-12-00227.
ST24-A003
Clarification of Atmospheric Tidal Modes Appearing in Ionospheric Currents by Independent Component Analysis
Kumi TAKAYAMA#+, Akimasa YOSHIKAWA, Yasunobu MIYOSHI
Kyushu University, Japan
Daytime ionospheric currents are complexly superimposed the Sq-EEJ current system induced by solar radiation and currents excited by various modes of atmospheric waves. Therefore, no method has yet been established to separate each phenomenon from the observed data. In this study, we used Independent Component Analysis (ICA), which separates and extracts independent components from multivariate signals, to extract variations due to atmospheric waves from ground magnetic field data of the MAGnetic Data Acquisition System/Circum-pan Pacific Magnetometer Network (MAGDAS/CPMN) on magnetically quiet days for 1992-2004. As a first step, we reduce the dimension of the data with Principal Component Analysis (PCA) to remove noise. Since [Gurubaran, 2002] suggests that the first principal component is the Sq-EEJ current system and atmospheric tidal variations appear in the addition of the 2nd through 5th principal components. Therefore, we applied ICA to the 2nd through 5th principal components as four variables. Also, we visualize the horizontal current structure from each independent component as equivalent current. In addition, we reproduce each atmospheric tidal mode influenced on the ionospheric currents with an atmosphere-ionosphere coupled model (GAIA) and compare with the current structure of each independent component to discuss which mode has a strong influence on the ionospheric current.
ST24-A007
Ionospheric Disturbances During and After the Annular Solar Eclipse on 21 June 2020 Due to the Convergence Effects
Xiaoyin LI1+, Jin WANG2, Tao YU1#
1China University of Geosciences, China, 2China University of Geosciences (Wuhan), China
An annular solar eclipse passed through the East Asia at low latitudes on 21 June 2020, which provides us an opportunity to study the eclipse-induced ionospheric disturbances at low latitudes. In this study, we analyze the observations of the ionosondes at Wuhan (30.4°N, 114.4°E, 82.4% obscuration), Xiamen (24.2°N, 118.07°E, 97.8% obscuration), and Nanning (22.7°N, 109.25°E, 81.1% obscuration), as well as the total electron content (TEC) data from the Global Navigation Satellite System (GNSS) of the Global Ionosphere Maps (GIMs) to examine the ionospheric behaviors in the F-region on 21 June 2020 solar eclipse day. The observations show that a TEC enhancement occurred after the major depression near the center path of obscuration, along with the occurrence of the TEC depletions both in the northern and southern sides. The TEC enhancement lasts to midnight on the solar eclipse day. The independent in-situ electron density (Ne) observation from the Swarm-B satellite and the slant TEC profile from the radio occultation technique of COSMIC-2 also observed the long-lasting enhancement in the F2 region near midnight. The solar eclipse-induced convergence effects can result in the long-lasting ionospheric perturbations, which may further cause the spread-F in the nighttime.
ST24-A008
Assimilated Ionosphere - Thermosphere Coupled Model for Lower and Equatorial Latitudes
I-Te LEE1,2#+, Jyun-Ying HUANG3, Mark CHENG3
1Central Weather Administration, Taiwan, 2National Central University, Taiwan, 3Central Weather Bureau, Taiwan
The Space Weather Operational Office (SWOO) of the Central Weather Bureau (CWB) in Taiwan response for providing space weather information and forecasts daily and locally. Due to the geolocation of Taiwan, higher plasma density during the day time period overhead are recorded associated with the equatorial ionization anomaly, and to observe plasma bubbles/irregularities in the evening to midnight period. Those phenomena significantly influence high-frequency and satellite communication as well as navigation and positioning services. Thus, in order to provide a useful and reliable forecast of ionosphere locally, a data assimilated ionosphere and thermosphere coupled model is operated by SWOO since 2018. The coupled model is the NCAR TIE-GCM, and the assimilated data includes total electron content derived by global ground-based GNSS receivers and electron density profiles measured by the FORMOSAT-7/COSMIC-2 radio occultation (RO). The assimilation system is routinely updated hourly, and then forecasts the condition of the ionosphere and thermosphere for the next six hours. The evaluation of assimilated results with ionosonde observations shows the correlation coefficient of foF2 is about 0.85, particularly yielding a better performance at the latitudinal region between 40° and -40°. On the other hand, the results further show an additional improvement of peak density by assimilated F7/C2 RO electron density profiles. Furthermore, the assimilated results also indicate the daily density maximum occurred earlier than control run at lower latitudes and thus lead to more studies. These assimilated dataset are archived by SWOO from 2019 till now, it could be used to conduct more study for lower and equatorial ionosphere and thermosphere.
ST24-A009
Variability of Equatorial Plasma Bubble Occurrence Rate from OI 135.6nm GOLD Observations
Deepak KARAN1#+, Richard EASTES1, Carlos MARTINIS2, Robert DANIELL3, Quan GAN1, Wenbin WANG4, William MCCLINTOCK1
1University of Colorado Boulder, United States, 2Boston University, United States, 3Ionospheric Physics, United States, 4National Center for Atmospheric Research, United States
Equatorial Plasma Bubbles (EPBs) are the manifestations of post sunset plasma irregularities that are associated with the depleted plasma densities that occur over the equatorial- and low latitudes. The seeding, development, and persistence of the plasma irregularities depend on many factors, including the alignment of the dusk terminator with the magnetic field lines, thermospheric winds, waves, electric fields, etc. These factors change with day-to-day, seasons and solar flux conditions, producing variabilities in the EPB occurrence rate. Further, the varying nature of these factors at different longitude sectors creates longitudinal variability in the EPB occurrence rate. OI 135.6 nm emission images from the NASA GOLD (Global‐scale Observations of the Limb and Disk) imager detect EPBs ~1-1.5hrs after sunset over the South America, Atlantic, and West African longitude sectors. In this work, we use the GOLD data to investigate the day-to-day, seasonal and longitudinal variations of EPBs occurrence rates and their solar activity dependence over these three longitude sectors from 2019 to 2021 during the equinoxes and solstices. Over the South American and Atlantic longitude sectors, the EPB occurrence rate was around ~95% in December solstices. The occurrence rate over the West African longitude sector in the same month was ~10%. Results suggest that (i) the March equinox is more favorable than the September equinox for EPBs occurrence during low solar activity period, (ii) EPBs occurrence increases from September to December in all three years, (iii) EPB occurrence increases with increasing solar activity from 2019 to 2021 at all the longitude sectors, and (iv) a prominent quasi 6-day periodicity is observed in the EPBs daily occurrence rate over the South America longitude sector. The day-to-day, seasonal, and longitudinal variations of EPBs occurrence rates and their solar activity dependence will be discussed in this work.
ST25-A002
Role of Q2DW-Tide-GW Interactions at SH Mid-latitudes in Interhemispheric Coupling
Zishun QIAO1#+, Alan LIU1, Nicholas PEDATELLA2, Gunter STOBER3, Iain REID4,5
1Embry-Riddle Aeronautical University, United States, 2National Center for Atmospheric Research, United States, 3University of Bern, Switzerland, 4ATRAD Pty Ltd, Australia, 5The University of Adelaide, Australia
Most theoretical investigations into the mechanism of interhemispheric coupling (IHC) have previously focused on the modulation of mesospheric meridional circulation driven by forcing of GWs originating in the troposphere and recently on the role of quasi-two-day waves (Q2DW) and GWs in-situ generated in the middle atmosphere. This study utilizes paired meteor radar observations (CONDOR, 31.2ºS,70.0ºW and Buckland Park Meteor Radar, 34.6ºS,138.4ºW) and SD-WACCM-X simulations to provide observational confirmation on the role of Q2DW and GWs at summer hemisphere mid-latitudes to IHC mechanisms. Specifically, Q2DW-tide interactions as well as their child waves are investigated during the 2021 NH SSW. The connection between Q2DW-tide-GW interactions and IHC mechanism during the 2021 NH SSW will be presented.
ST25-A003
Latitude Dependence of Ionospheric F2 Layer Plasma Drift Characteristics
Blessy VARGHESE1#+, Tiju JOSEPH MATHEW2
1Christian College Chengannur, University of Kerala, India, 2Christian College, India
The comparison of Ionospheric F2 layer plasma drift characteristics at different latitudes is presented in this work. The zonal and vertical plasma drift velocities were obtained over an equatorial station, Boa Vista (2.8° N; 60.7° W) and a mid-latitude station, Eglin (30.5° N; 86.5° W) using a Digital Ionosonde. Quiet days (Kp < 5) during one year from November 2013 to October 2014 are selected for analysis of seasonal behaviour. Some interesting systematic and regular features with strong seasonal dependence are observed during sunrise and sunset. The latitude dependence of these features is analyzed. Resultant plasma drift vectors in the zonal-vertical plane for these stations are obtained, perhaps for the first time using simultaneous observations of the zonal and vertical plasma drift components.
ST25-A006
Simultaneous Observations of Thermospheric Na Layers at Two Nearby Midlatitude Lidar Stations
Fang WU+, GuoTao YANG#, Jing JIAO
Chinese Academy of Sciences, China
The metal layers in the Earth’s upper atmosphere have received growing attention in recent years because of the discovery of the Thermosphere-Ionosphere metal (TIMt) Layers by lidar. In the reports of lidar detection TIMt Layers, the highest metal atom layer is Thermosphere-Ionosphere Na (TINa) Layers observed at Yanqing station (40.42°N, 116.02°E), while the Ca+ Ions Transport From ∼80 to 300 km. In 2014, another Na lidar was developed at Pingquan station(41.0°N, 118.7°E), which is about 250 km away from Yanqing station. Simultaneous detection of metal atoms and metal ions by resonance fluorescence lidars and an all-solid-state lidar at that two nearby midlatitude stations. We divide thermospheric Na layers (defined here as 110-200km) observed in two stations into four types, including lower thermosphere sporadic Na layers, dawn thermosphere-ionosphere Na layers, midnight thermosphere-ionosphere Na layers and mid-latitude thermosphere-ionosphere Na layers (Mid-TINa), depending on their occurrence, temporal evolution, other characteristics, and referring to the previous reports. Moreover, there are rare reports of the small-scale horizontal distributions of TINa layers. According to the observation results of Na, Ni, Ca and Ca+ inos, it suggested that Mid-TINa is not neutralized from the Es layer, which may be triggered by other possible formation mechanisms.
ST25-A009
Three-dimensional Ionospheric Plasma Properties of Space Hurricane
Sheng LU1+, Zanyang XING1#, Qing-He ZHANG2,1, Yongliang ZHANG3, Kjellmar OKSAVIK4, Larry LYONS5, Yu-Zhang MA1, Xiang-Yu WANG1, Balan NANAN1, Yong WANG1, Zhong-Xin DENG6
1Shandong University, China, 2National Space Science Center, Chinese Academy of Sciences, China, 3Johns Hopkins University Applied Physics Laboratory, United States, 4University of Bergen, Norway, 5University of California, Los Angeles, United States, 6China Research Institute of Radiowave Propagation, China
We report a space hurricane event in the Northern Hemisphere observed by multiple instruments. Based on the convective velocity observations from ground-based radars and ionospheric satellites, we confirm that space hurricane rotates clockwise at the altitude of the ionosphere and can modulate the ionospheric convection pattern in polar cap. From plasma in-situ measurement of incoherent scattering radar, we firstly obtain the 3D plasma properties of space hurricane including: (1) strong flow shears, (2) ion temperature enhancements caused by Joule heating, (3) electron density precipitation, (4) multiple ion temperature enhancements corresponding to sunward velocity one by one, which is considered to be caused by spiral arms. These results complete the picture of space hurricane at the altitude of ionosphere and give a better understanding of the magnetosphere-ionosphere coupling process in polar cap.
ST25-A011
Chinese and Russian Atmospheric Electric Field Joint Observation Along a Meridian Chain
Lei LI#+
National Space Science Center, China
There are three main sources which influence the atmospheric ionization: solar activities, meteorological activities (vapor, wind, ice, precipitation, cloud and lightning) and geological activities. Since the variation of atmospheric electric field is characterized by local and global effects, atmospheric electric field observations at different latitudes are more comprehensive and meaningful. China and Russia have 42 observation stations at different latitudes (20°N~70°N). Based on the different latitudinal observed data from a same meridian chain stations in both Russia and China, the researchers can compare and study: (1) The processes that solar activities such as solar flare, SEP (solar energetic particle), CME (corona mass eject), CME with -magnetic cloud influence the atmospheric electric field. (2) Meteorological activities that influence the atmospheric electric field. (3) The physical processes how geological activities influence local atmospheric electric field.
SE01-A006
Mineralogical and Geochemical Occurrence of Mercury in Mine Tailings from Abandoned Mercury Mine in Palawan: Implications in Environmental Impact
Alexandria TANCIONGCO1,2#+, Jessie SAMANIEGO3, Gawen JENKIN4, Carlo ARCILLA1, Leon HICKS4, Vimalnath SELVARAJ4, Cris Reven GIBAGA3, Rico Neil QUIERREZ3
1University of the Philippines Diliman, Philippines, 2University of the Philippines Diliman, Philippines, 3Philippine Nuclear Research Institute, Philippines, 4University of Leicester, United Kingdom
One of the legacy mines in the Philippines, a mercury mine in Puerto Princesa City in Palawan Island, was operated by the Palawan Quicksilver Mines Inc. (PQMI) from 1953 to 1976. The tailings left behind was processed through calcination and was allegedly dumped in the jetty port in Honda Bay and surrounding villages. In this paper, the mineralogy and geochemistry of Hg is analyzed from sediments of three alleged mine waste dumping areas surrounding PQMI, namely, from the Honda Bay Wharf (HBW), from Sitio Matahimik (SMK; the village 300 meters away from former open pit site) and from the Puerto Princesa City Landfill (PPCL). Based on grain size analysis, the sediments with size less than 63µm show the highest mercury concentration reaching up to 885 ppm in SMK. Through automated scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS) analysis of composition, Hg is found to occur in mercury sulfides (HgS, cinnabar) surrounded by ferric oxide minerals and silica for all sampling sites. The cinnabar grains from both SMK and PPCL are relatively large (10µm size) and do not contain visible zoning, indicating that no processing had occurred while grains from HBW are smaller (<2µm) and broken in textural form. It is inferred that the “mine wastes” dumped in SMK and PPCL are the low-grade ore materials that did not pass the cut-off grade while those in HBW are the calcined ores. From these findings, it was confirmed that the finer grain size fractions that are more prone to inhalation through dust are concentrated with cinnabar minerals. Meanwhile, lower HgS amount in HBW occurring within goethite phases assures low biotoxicity of the metal provided it is not reacted with acidic water. This study contributes to the current knowledge in abandoned mine tailings in the Philippines and its implications in mine environmental safety.
SE02-A006
Late Quaternary Tectonic Activity of NW-trending Elashan Fault in the Ne Margin of the Tibetan Plateau and Implications for Plateau Deformation Mechanism
Zhikun REN1#+, Jinrui LIU2, Wei MIN2, Zhimin LI3, Dengyun WU2
1Institute of Geology, China Earthquake Administration, China, 2China Earthquake Administration, China, 3Earthquake Administration of Qinghai Province, China
Due to the effects of India-Eurasia convergence, the northeast margin of the Tibetan Plateau still has complex and intense deformation, which can be the best natural laboratory to study the expansion and growth process of the Tibetan Plateau. The main fault system around Qinghai Lake block are EW-trending Haiyuan and Kunlun faults, and NNW-trending Elashan and Riyueshan faults. The strain partitioning and seismic hazard in this faults system are pivotal to understanding the fault interaction, and also the key to deciphering the kinematic mechanism of the northeastern margin of the Tibetan Plateau. However, the slip rates of the Elashan and Riyueshan faults are still controversial, and their role in the growth and expansion of the plateau is still unclear. Therefore, we target the NNW-trending Elashan fault and use multiple levels of high-resolution topography data, including DEMs generated from WorldView and GF-7 stereo pairs of satellite images, unmanned aerial vehicle (UAV)-derived DEMs, to interpret its detailed and fine geometry. Furthermore, combining optically stimulated luminescence (OSL), radiocarbon, and cosmogenic isotope dating methods, we constrained the late Quaternary slip rates of the north and south segments of the Elashan fault to be ~1.5-2.5 mm/yr and ~3-4 mm/yr, separately. We suggest that the Elashan and the Riyueshan faults are the result of adjusting the difference between the high shear rate of the Kunlun fault and the low shear rate of the Haiyuan fault, and are a way of accommodating continuum deformation between the major EW-trending fault systems.
SE02-A010
Quantitative Landscape Analysis of Eastern Cape York Peninsula, Australia
Kangqiao CHEN1#+, Renjie ZHOU1, Tara JONELL2
1The University of Queensland, Australia, 2The University of Glasgow, United Kingdom
Cape York Peninsula (CYP) in tropical far north Queensland in Australia is the northernmost extension of the Great Dividing Range, a section of the East Australian passive margin created during opening of the Tasman Sea. This section of the Great Dividing Range is tectonically unique because of the ongoing collision to the north in Papua New Guinea. Influenced by a combination of tectonic and climatic processes, landscape dynamics in CYP are complex yet offer a natural laboratory in which to study their interaction. To explore landscape controls in CYP, it is essential to first fundamentally characterise the landscape. We derive a range of maps including the slope map, relief map, basin distribution and network maps from the SRTM 90-m DEMs. We also use SRTM 90-m DEMs with TopoToolbox 2.0 and RStudio to generate swath profiles, longitudinal profiles, hypsometric curves, slope-elevation plots, normalized steepness-lithology plots, elevation-lithology plots and slope-lithology plots. Our preliminary data suggests that igneous and high-grade metamorphic rock units, ranging from Proterozoic to Cretaceous in age, are correlated with steep and rough landscape. Results also show that lithology dictates highland and escarpment locations, along with catchment-wide geometric features. This study highlights how catchments are characterised under the tropical climate and northeastern Australian passive margin tectonism.
SE02-A020
The Impact of the 2018 Lombok Earthquake Sequence, Indonesia on the Unrest Rinjani-Samalas Volcanic Complex Inferred from the Time-dependent Seismic and Volcanic Source Models
Siyuan ZHAO#+, Simon MCCLUSKY, Meghan MILLER, Phil CUMMINS
Australian National University, Australia
In 2018, four deadly (Mw 6.2 to 6.9) earthquakes struck the north coast of Lombok Island, on 28 July, 5 August, and 19 August, distributed between the Flores back-arc thrust and the Rinjani-Samalas volcanic complex. We performed a comprehensive analysis of relocated aftershocks, static coulomb stress changes, and co-seismic and post-seismic deformation, to improve our understanding of this earthquake sequence. The fault geometries and slip distributions of the three mainshocks are modelled by inverting the co-seismic deformation imaged using an interferometric analysis of Sentinel-1 InSAR measurements, based on a multi-layered elastic half-space. The earthquake sequence aftershocks were analysed using an unsupervised learning method (ST-DBSCAN) to cluster these relocated aftershocks so that we can identify the source of each aftershock. We perform an InSAR time-serie analysis to investigate the time-dependent post-seismic deformation in the two years following the Lombok 2018 earthquake sequence, deriving a combined model that simulates the viscoelastic relaxation and afterslip simultaneously. The Coulomb stress change modelling based on the co-seismic and post-seismic rupture models indicates the stress change around the Barujari Crater region, which affects the open of the magma conduct, reflected as edifice-scale deflation and inflation. To quantify the influence of the earthquake sequence on the spatiotemporal deformation pattern of the volcano edifice, we extended our InSAR time-series range forward to the year 2014, just prior to the two eruptions that occurred on 25th October 2015 and 1st August 2016, and perform Principal Component Analysis to investigate the time-dependent inflation and deflation signals. We modelled the volume change and the location of the volcano pressure source for a better understanding of how changes in the magma body and magma movement may have been influenced by the 2018 Lombok earthquake sequence. A double-source compound model is used to invert the parameters of the magma chamber.
SE03-A013
Discovery of Volcaniclastic Deposits on the Eastern Wall of Aso Caldera (SW Japan): Implications for Characteristics and Frequency of Holocene Mass Movement in the Central Kyushu Region
Yasuo MIYABUCHI1#+, Hideo HOSHIZUMI2
1Kumamoto University, Japan, 2Geological Survey of Japan, Japan
Several volcaniclastic deposits discovered at the foot of the eastern wall of Aso caldera, central Kyushu, southwestern Japan, are divided into two types: lahar deposits (Lh1–Lh5 in descending order), which contain abundant subangular to subrounded lithic clasts (<3.5 m in diameter) set in a sandy to silty matrix, and debris avalanche deposits (DA1 and DA2), which include numerous plastically deformed fragments of tephra (ash and scoria) and soil layers in a homogenous silty to clay matrix. DA2, which underlies a paleosol dated at 5.4 cal ka BP (calibrated 14C age), is the largest volcaniclastic deposit observed in the section (more than 2.5 m thick and about 70 m wide). Because the debris avalanche deposits display no evidence that they were transported by water, they are likely to have originated from landslides triggered by intense earthquakes. Tephra chronology and 14C-dating on paleosols along the succession suggest that lahars occurred once over 900 years (6.3–5.4 cal ka BP), three times over 1400 years (5.4–4 cal ka BP), once over 400 years (4–3.6 cal ka BP) and twice (including the 2012 lahar) in the last 3600 years. This evidence indicates that the lahars occurred at an interval of 400–1800 years. In contrast, two debris avalanche deposits exist in the same succession spanning the last 6300 years. Including landslides and associated debris avalanches triggered by the 2016 Kumamoto earthquake (Mj 7.3), landslides generating debris avalanches in the Aso caldera occurred at least three times in the last 6300 years. This may suggest the frequency of large earthquakes triggering debris avalanches in the central Kyushu region, which has many active faults.
SE05-A004
Numerical Modeling on the Growth Dynamics of Fold-and-thrust Belts in the NE Margin of the Tibetan Plateau
Qizhi CHEN1,2+, Caibo HU1#, Felipe ORELLANA-ROVIROSA3, Yaolin SHI1
1University of Chinese Academy of Sciences, China, 2University of Chinese Academy of Sciences, China, 3Southern China University of Science and Technology, China
The NE margin of the Tibetan Plateau, as the leading edge of the northeastward growth and expansion of the Tibetan Plateau, formed a series of horizontally-arcuate structural belts since the late Cenozoic, and additionally, several historical, strong earthquakes have occurred here. We present a series of 3D-time-dependent finite-element models with elasto-plastic and frictional nonlinearities to understand the formation-evolution of arcuate folds here comprising real regional fault-zones including the Haiyuan, Xiang Shan–Tianjing Shan, Yantong Shan, and Niushou Shan faults since about ~10 Ma. Our reference simulation, having adequate parameter values from the available literature plus suitable boundary conditions for the region, produces four distinct major EPS concentration zones that are horizontally arcuate and developed outwardly-NE in spatio-temporal sequence, and symmetrically-perpendicular to the contraction direction. These major plasticity bands are spatially highly-correlated with the main regional geologic faults: Haiyuan fault, Xiang Shan–Tianjing Shan fault, Yantong Shan fault, and Niushou Shan fault on the NE margin of the Qinghai–Tibetan Plateau. Our reference-model-based sensitivity analysis suggest that the horizontal northeastward pushing-advancement-contraction of the region being bounded by a frictional vicinity (rigid Alxa and Ordos blocks hindering the advancement) have the dominant control on the formation and evolution of these arcuate fold-and-thrust belts perpendicular to the contraction axis, while the rotations imprinted by the Ordos and Alxa blocks and the shearing of the Qinghai–Tibetan Plateau, have only secondary effects. An additional, generic sensitivity analysis reveals that the folds’ horizontal curvature per unit horizontal shortening-displacement increases with the friction on the bounding vicinity, and this result could be considered for other Earth scenarios and planets.
SE05-A008
Intracontinental Multi-stage Deformation of the Langshan Tectonic Belt on the Western Margin of the North China Craton
Liyun ZHOU1#+, Yu WANG2
1China University of Geosciences (Beijing), China, 2China University of Geosciences, China
Precise dating of multiple-stage deformation in intracontinental settings and during cratonic destruction is difficult to achieve, and understanding the mechanisms involved is challenging. After various assemblies of microcontinents in the late Paleozoic, west and east China underwent different intracontinental tectonic evolutions with various tectonic frameworks on either side of the N–S-trending Helanshan–Liupan–Xueshan tectonic belt. The Langshan area in the northern part of this tectonic belt records a variety of tectonic mechanisms and evolutionary processes. During the Mesozoic–Cenozoic, at least four stages of deformation occurred along the belt, including (1) thrusting towards the south, which involved the crystalline basement and accompanied followed the emplacement of voluminous granitic rocks; (2) transpression, which produced NE–SW strike-slip faults and ductile shear zones as a result of NW-verging ductile compression; (3) NW-to-SE thrust faulting, which thrust the crystalline basement over Cretaceous strata; and (4) Cenozoic E–W extension, high-angle normal faulting, and rift basin formation. Zircon U–Pb LA–ICP–MS dating, as well as 40Ar/39Ar dating of synkinematic muscovite, sericite, and deformed biotite, yielded Mesozoic time constraints so that (1) N–S contraction occurred at 242–206 Ma, slightly later than the intrusion of granites at 242–234 Ma; (2) NE–SW-sinistral strike-slip motions and NW-verging compression took place at 183–160 Ma; (3) NW–SE contraction took place at 126–117 Ma; and (4) high-angle normal faulting occurred at 15–13 Ma (apatite fission track dating). The tectonic stresses involved were all far-field effects transmitted from continental margins. The N–S-trending tectonic belt marks the geographic boundary between west and east China, and it played the role of a weak zone in the crust that was reactivated repeatedly in response to a variety of distant tectonic events, and it therefore records a complex history of tectonic activity.
SE05-A009
Sedimentology and Provenance of Late Cretaceous Basins in the Sichuan-Hubei-Hunan Fold-thrust Belt, South China: A Record of Intracontinental Deformation
Qihui ZHANG1+, Liang QIU2#, Dan-Ping YAN 1, Minglong LI 3, Tao YANG 1, Shahnawaz ARISER4, Boyong YANG3, Xuesong ZHAO 3
1China University of Geosciences, China, 2China University of Geosciences (Beijing), China, 3Hubei Geological Bureau, China, 4Geological Survey of Pakistan, Pakistan
Plate tectonics theory assumes that the interior of the continent is rigid and difficult to deform. However, previous studies on the early Mesozoic strata in South China Block have verified the process of intracontinental deformation by using paleomagnetism, geochronology, and structural analysis. Sedimentology and provenance of basins also well record the intracontinental deformation. This paper presents detailed sedimentology, paleocurrent direction, sandstone component, and heavy minerals of the Jianshi, Enshi, Qianjiang, and Laifeng basins in the South China Block. Late Cretaceous red sandstone strata are principal across the study area and unconformably overlie the underlying strata. The sandstones contain abundant quartz with minor amounts of feldspar and lithic fragments. The spatial variation of the zircon-tourmaline-rutile (ZTR) index suggests that the Jianshi basin is nearer to the main source area than the Laifeng basin. The sediments of these basins show a high proportion of hematite, magnetite, ilmenite, pyrite, leucoxene, zircon (round), rutile, garnet, and epidote. The NW-trending paleocurrent and the parent rock type of mainly intermediate-basic magmatic rocks reflect that the Dabashan fold-thrust belt becomes the main source area. The increase of apatite content in Qianjiang basin and the SE-trending paleocurrent indicate that Xuefeng orogenic belt also provides potential sources. Provenance analysis results combined with previous geochronological data prove the uplift and denudation of Dabashan fold-thrust belt and Xuefeng orogenic belt in the Late Cretaceous. In addition, the normal faults control the deposition of the Jianshi, Enshi, and Laifeng basins, indicating that the Sichuan-Hubei-Hunan fold-thrust belt experienced extension in the Late Cretaceous.
SE05-A010
Molybdenum and Boron Isotopic Evidence for Carbon-recycling via Carbonate Dissolution in Subduction Zones
Yunying ZHANG1#+, Min SUN2, Chao YUAN3, Zhen SUN3, Qian LIU4
1South China Sea Institute of Oceanology, Chinese Academy of Sciences, China, 2The University of Hong Kong, Hong Kong SAR, 3Chinese Academy of Sciences, China, 4Northwest University, China
Subduction zones are critical sites for carbon recycling between the earth surface and interior, which modulate the global carbon budget and influence Earth’s climate. To balance the carbon flux in subduction zones, carbon release through dissolution of carbonate minerals has been highlighted based on recent studies of fluid inclusions in high-pressure metamorphic rocks. However, the lack of direct evidence from arc lavas hampers our understanding of carbonate dissolution. Besides, it remains unclear to what extent the subducted carbonates can be recycled back to the overriding plate. To explore the role of slab-derived fluids in the deep carbon cycle, herein we report Mo and B isotopic data for Silurian arc andesites (426 Ma) and adakitic andesites (422 Ma) from the Chinese Tianshan, which represent partial melts of fluid-modified mantle wedge and dehydrated oceanic crust, respectively. The arc andesites yielded δ98Mo values (0.33–1.08‰) significantly higher than that (about –0.20‰) of the depleted mantle, which could be ascribed to the incorporation of crustal material with heavy Mo isotopes in the mantle source. Since marine carbonate is featured by both heavy Mo and B isotopes and our arc andesites also give heavy δ11B (–1.63 to +4.00‰) values, we consider that marine carbonate was possibly involved as a component of the subducted slab. In contrast, the younger adakitic andesites have light δ98Mo (–0.48 to –0.27‰) and δ11B (–9.43 to –2.05‰) values, implying an isotopically Mo- and B-light source without carbonate signature. Given the preferential transport of heavy 98Mo and 11B to the fluid phase during slab dehydration, their remarkably light δ98Mo and δ11B values support a dehydrated oceanic crust as their magma source. The contrasting Mo–B isotopes for such two kinds of andesites highlight that most carbonates can be removed from the subducted slab to the overriding plate during oceanic subduction.
SE05-A011
Formation of Shear Bands in Foliated Granitic Rocks: A Field-based Analysis
Nandini CHOUDHURY1#+, Atin Kumar MITRA1, Nibir MANDAL2
1Indian Institute of Engineering Science and Technology, India, 2Jadavpur University, India
Micro- to macro-scale shear bands are quite common signatures of tectonic deformations in most of the granitic gneissic terrains, and they play a crucial role in syn-kinematic material transport processes during high-temperature metamorphic segregations. Understanding the mechanisms of their formation is thus important to theorize a range of petrological as well as structural phenomena. This study reports shear bands from strongly anisotropic foliated rocks in granite gneisses of the Chotonagpur Granite Gneissic Complex (CGGC), with an aim to show the mechanisms of their formation in association with fold structures produced by buckling instability. Realignment of mineral grains during the buckle-induced microfolds has resulted in the localization of discrete weak planes, which ultimately define a new set of mineral fabrics that completely obliterated the earlier fabrics. Using field correlations we recognize the initiation of shear bands during this structural transformation and their growth with progressive deformations. In CGGC the gneissic foliations are often asymmetrically buckled, where the short limbs of the consecutive folded layers show intense shear localization, forming a shear band structure. Moreover, some shear bands have been observed to be associated with kink band geometry. This article presents the characteristic features of these types of bands.
SE05-A012
Differential Uplift of Granite Mass in the Basu Region of the Eastern Bangong-Nujiang Suture Zone: Evidences from Zircon and Apatite Fission Track
Xunzhang ZHU1, Dongliang LIU2#+, Haibing LI3, Jiawei PAN1, Zhongbao ZHAO1, Yong ZHENG1, Chao LI1
1Chinese Academy of Geological Sciences, China, 2Institute of Geology, Chinese Academy of Geological Sciences, China, 3Chinese Academy of Geological Sciences, Institute of Geology, China
The Bangong-Nujiang New Tethys Ocean suture zone is an important tectonic boundary, separating the Qiangtang block and the Lhasa block in the Qinghai-Tibet Plateau. This suture zone is one of the important windows to deciphering the growth history of the Qinghai-Tibet Plateau. This suture zone can be divided into three parts: the western, middle and eastern sections. Few studies were involved in the eastern section, which contains abundant structural evolution information. In this study, a vertical profile of granite near Guoqing village of Basu County is taken to study the tectonic uplift process by the fission track dating, including zircon fission track (ZFT) and apatite fission track (AFT) with laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). The zircon U-Pb ages center at ~180 Ma, indicating that its crystallization age is the Early Jurassic. The ages of ZFT and AFT are ~180-130 Ma and AFT are ~86-61Ma, respectively. The QTQt simulation showed that the upper NJ-01 sample of the profile had a fast erosion rate during ~130-60 Ma, the middle NJ-03 sample and NJ-04 sample had a slower erosion rate during ~130-40 Ma, and the lower NJ-06 sample maintained the slowest during rate since ~130 Ma. This differential uplift is caused by the earlier slab break-off in southward subduction than in the northward subduction, which induced the negative slope of the Age-Elevation Relation of ZFT and positive slope of the Age-Elevation Relation of AFT. Based on this and previous research results, the granites with age of 180 Ma in the Basu area are resulted by the northward subduction of the Bangong-Nujiang suture zone, the erosion uplift induced zircon fission track cooling age since ~180 Ma, and the erosion uplift generated apatite fission track cooling age during ~86-61 Ma.
SE05-A013
Late Mesozoic Tectonic Transformation on the Eastern Margin of the Yangtze Block
Xin CHEN#+, Songnan LIU, Liyun ZHOU
China University of Geosciences, China
Yangtze platform formed in the Neoproterozoic, as the second platform of China has an important status. It is adjacent to the Mid-Korean quasi-platform in the north west, and adjacent to the South China fold system in the south east. The Ningzhen Mountains are located on the northern edge of the Lower Yangtze platform, spread from southwest-northeast to east-west, about 100 kilometers long. Complex folds and thrust faults are widely developed in this area, the field survey and data analysis show that there are mainly two sets of structural systems: one is east-west and the other is northeast. EW trending folds such as Longtan-Cangtou folds have an inverse ”S” shape axis, which means that on its sides the axis is twisted to the northeast. Low angle EW trending overthrust faults develop on Triassic limestone and Jurassic sandstone along the edges of folds. The NNE trending strike-faults (Liuhe-Jiangpu, Guabu-Tiexinqiao, Fangshan-Danyang, Maoshan fauls) cut through the existing EW trending structures forming a unique vertical tectonic pattern. There are also NW trending strike-faults cutting Ningzhen Mountains into some transvers block in some areas. Volcanic rocks are mainly in Yanshanian period and there is a set of conglomerate developed in the area. The U-Pb Age analysis shows that the granitic dikes cutting across the strike-fault are 104.2±1.3 Ma and 102.6 ±1.1 Ma. How do these structures relate to each other? What is the specific age of those deformations? Whether and how the subduction of the paleo-Pacific plate influenced the transformations of the structure orientations? Those questions remain to be clarified.
SE05-A015
Velocity Structure of the Sulu Orogenic Belt in the Yellow Sea, East China: Evidence from Wide-angle Ocean Bottom Seismograph Data
Weina ZHAO1#+, Chenguang LIU2, Zhiqiang WU3
1Northwestern Polytechnical University, China, 2Ministry of Natural Resources, China, 3Qingdao Institute of Marine Geology, China
The Sulu orogenic belt, formed by the collision between Sino-Korean and South China blocks, has important tectonic implications due to its unique tectonic setting. To understand the deep crustal structure of the extension of the Sulu orogenic belt in the Yellow Sea, we presented a active-source ocean bottom seismometer wide-angle reflection/refraction profile across the Yellow Sea. The obtained P-wave velocity structure exhibits significant horizontal and vertical variations. The middle and upper crustal regions of the north beneath the survey line exhibit a higher velocity and larger thickness than those of the south, whereas the opposite is the case with the lower crust. Due to undulating Moho interface and varying crustal velocities the Qingdao–Rongcheng fault is suggested as a fault in the Sulu orogenic belt without the significance of tectonic zoning. This study shows that the Sino-Korean Block, Sulu orogenic belt, and South China Block are bounded by the Jimo–Muping faults (an extension to the sea), Qianliyan fault, and deep fault of the South Yellow Sea. Furthermore, the Sulu orogenic belt may have been formed by the northward subduction of the South China Block beneath the Sino-Korean Block during the Indo-Sinian orogeny to the east of the Shandong peninsula.
SE05-A021
An Optimal Spatial-filtering Method Derived from Eigenvalue Perturbation for Extending the Courant-Friedrichs-Lewy Stability Limit
Zhongzheng MIAO+, Jinhai ZHANG#
Chinese Academy of Sciences, China
The numerical simulation of wave propagation is a vital importance tool for imaging the interior structure of the Earth and simulating long-term geodynamic evolutions. The explicit time-marching scheme is widely used in numerical simulation owing to its low memory demand and simplicity of numerical implementation. However, its maximum time step is constrained by the Courant-Friedrichs-Lewy stability limit. To overcome this limitation and improve the computational efficiency of the explicit time-marching scheme, the eigenvalue perturbation and spatial-filtering methods have been developed. The eigenvalue perturbation method has high numerical accuracy but requires unaffordable memory demand and computational cost even for middle-scale models. In contrast, the spatial filtering method can be naturally integrated into the pseudo-spectral method but has high large numerical errors under large time steps. However, the intrinsic connection between these two methods is still unclear. By considering the eigenvalue perturbation method for the homogeneous model, we reveal the intrinsic relation between these two methods. Based on this relation, we obtain the analytical spatial filter for the homogeneous model and the optimal spatial filter for the heterogeneous model. Compared with the traditional spatial filtering method, which directly removes all high wavenumber components, the proposed method eliminates those wavenumber components that lead to instability and retains those wavenumber components that help maintain numerical accuracy. With the same numerical accuracy, the maximum time step allowed by the proposed method is about twice that of the traditional spatial filtering method. Compared with the eigenvalue perturbation method, this method can be directly applied to large-scale models without extra memory consumption and computation cost. The proposed method can significantly accelerate the speed of numerical simulation of seismic waves and long-term geodynamic evolutions.
SE05-A025
Dynamics of Oceanic Slab Tearing During Transform-fault Oblique Subduction: Insights from 3D Numerical Modeling
Jie XIN1#+, Huai ZHANG1, Zhong-Hai LI1, Felipe ORELLANA-ROVIROSA2, Liang LIU3, Yigang XU3, Zhen ZHANG1, Yaolin SHI1
1University of Chinese Academy of Sciences, China, 2Southern China University of Science and Technology, China, 3Guangzhou Institute of Geochemistry, China
Oceanic slab tearing is identified during plate subduction, and the resulting slab window allows hot mantle materials to pass through, resulting in anomalous thermal and chemical conditions in convergent-margin environments. To understand the mechanism of vertical slab tearing, we introduce a 3D numerical model to investigate the characteristics of transform-faulted oceanic slab during oblique subduction, and we compare model results with natural observations from seismic imaging. We find that (i) transform-fault ages-offset and (ii) subduction horizontal obliqueness have the first-order control on the generation of vertical tearing, even without the lateral physical property (density and viscosity) differences. Regarding the two patterns of vertical tearing, we find that young overall lithosphere (average <30 Myr) at medium-low subduction obliqueness angles (<40°) tends to produce fault-perpendicular slab tearing. In contrast, combinations of high-medium obliqueness angles (>10°) and large age ratios of the older slabs (average >30 Myr) tend to produce fault-parallel tearing. Our modeling results also suggest that the continual along-trench variation in subduction dip angle may be related to oblique subduction's early stages of evolution. Observing the age contrast across faults and the horizontal obliqueness of plates' motion may allow predictions of the tearing pattern, evolution, and local mantle flow.
SE05-A026
Introducing Underworld3 - A High Performance Geodynamic Modelling Code Focused on Usability
Louis MORESI1#+, Julian GIORDANI2, Haibin YANG3, Andres RODRIGUEZ4
1Australian National University, Australia, 2The University of Sydney, Australia, 3Zhejiang University, China, 4The University of Melbourne, Australia
We introduce underworld3, a finite element, solid-Earth modelling code designed to be both straightforward to use and highly scalable to peak high-performance computing environments. underworld3 inherits the design patterns of earlier versions of underworld such as 1) A python user interface that is inherently safe for parallel computation. 2) A symbolic interface that allows users to construct and simplify combinations of functions, unknowns and gradients-of-unknowns on the fly that are then used to construct the finite element representation of the problem. 3) Fast, robust, parallel numerical solvers, 4) Flexible, Lagrangian "particle" swarms for modeling transport-dominated quantities that are fully interchangeable with other data-types and can be treated as symbolic quantities. 5) Mesh adaptivity that falls fully within the symbolic framework. The design philosophy of Underworld is to provide readable python code that stays close to the mathematics of the problem definition and is scalable (unedited) from Jupyter notebooks all the way to tens of thousands of cores. Typical problems of interest are subduction zone models coupled to over-riding plate deformation, groundwater flow studies on a whole-of-basin scale, and earthquake rupture models coupled with tectonics.
SE05-A028
Source Characterization of the November 2022 Mw 5.6 Cianjur Earthquake in West Java, Indonesia
Yukuan CHEN#+, Karen LYTHGOE, Rino SALMAN, Christina WIDIWIJAYANTI, Lujia FENG, Dannie HIDAYAT, Eleanor AINSCOE, Shi Tong CHIN, Benoit TAISNE, Sang-Ho YUN, Shengji WEI
Nanyang Technological University, Singapore
A damaging Mw 5.6 earthquake struck West Java, Indonesia, on 21 November 2022 and killed more than 300 people. Here, we characterize the source parameters of the mainshock and aftershocks to better understand the damage and the hosted fault of the earthquake. We conducted a finite fault inversion for the mainshock using static and high-rate GNSS data. To detect and locate the mainshock and aftershocks, we collected continuous waveform data from nearby seismic stations around the Gede volcano, mostly running by the lab volcano at Earth Observatory of Singapore. We applied a deep-learning neural network named Earthquake Transformer (Mousavi et al., 2020), to automatically detect and pick P and S-wave arrivals from the continuous waveform data. Then all the seismic phase arrival times were fed into the REAL (Zhang et al., 2019) program to associate them with earthquakes. After association, the NonLinLoc method (Lomax et al., 2000, 2014) was applied to locate the detected earthquakes. Finally, we further refined the relative location of these events using the double-difference relocation (hypoDD) method (Waldhauser & Ellsworth, 2000). The relocated high-resolution aftershock seismicity distributes in the depth range of 2-8 km, delineating a SE-NW oriented fault, which matches well with geodetic observations, yet surface rupture was not detected. Combined with the focal mechanism of the mainshock and the finite fault models on two conjugate fault planes, we concluded that the mainshock ruptured a shallow portion of a strike-slip fault with a strike ~345o, with rupture directivity towards the northwest, which agrees with observed ground damages.
SE05-A029
Blind Fault Branching Beneath Central Myanmar Basin Revealed by High-resolution Aftershock Location and Focal Mechanism of the 2019 Mw 5.5 Ye-u Earthquake Sequence
Win Shwe Sin OO1#+, Wardah FADIL1, Karen LYTHGOE1, Yukuan CHEN1, Dannie HIDAYAT1, Lin Thu AUNG1, Phyo Maung MAUNG1, Hongyu ZENG1, Ei Mhone Nathar MYO2, Shengji WEI1
1Nanyang Technological University, Singapore, 2National Taiwan University, Taiwan
Near-field seismic observations are usually not available for high-resolution source studies, and even when they are, high-frequency analysis are rarely conducted to extract more information. Here I study a unique dense nodal array data acquired by the development of the 2019 Mw 5.5 strike-slip earthquake in Central Myanmar Basin. The network, composed of 20 nodal stations with station spacing of approximately 5 km, was deployed 2 weeks after the mainshock for 40 days. A machine-learning based algorithm (Earthquake Transformer) was applied to detect 677 aftershocks from the dataset. Double difference relocation reveals that these events are distributed between 9 to 16 km in depth with a nearly northwest-southeast trending horizontal distribution, which is consistent with left-lateral fault plane solution of the mainshock. On the vertical component of most stations, a strong phase between the P and S-wave arrivals is present. This is an S-to-P converted phase produced by a sharp velocity boundary between the basin and the bedrock. The optimal 1D velocity model, constrained by 3-component waveform modelling, suggests a sedimentary layer thickness of approximately 3.5 km beneath the stations. To determine the focal mechanism of aftershocks, I conducted waveform inversion at 0.5-2Hz that results in high-quality waveform fits. For very small aftershocks (~Mw 1), the focal mechanism inversion is done at higher frequency 2-8 Hz and the unmodeled structural effect is corrected by applying Amplitude Amplification Factor (AAF). The focal mechanisms include strike-slip, reverse thrust, oblique thrust with strike-slip components and a few normal events. Highly diverse aftershock focal mechanisms suggest the fault system is likely immature. The thrust and normal events indicate that the mainshock rupture had branched into or activated nearby secondary faults, which allow the strike-slip fault to propagate and develop a more complex fault system.
SE05-A030
Earthquakes and Faulting at the Southernmost Mariana Subduction Zone
Han CHEN1,2+, Han CHEN3, Hongfeng YANG3#, Gaohua ZHU3, Min XU4, Jian LIN5,4, Qingyu YOU4
1Sun Yat-sen University, China, 2Southern Marine Science and Engineering Guangdong Laboratory, China, 3The Chinese University of Hong Kong, Hong Kong SAR, 4Chinese Academy of Sciences, China, 5Woods Hole Oceanographic Institution, United States
Near-field observational data are collected in the Southern Mariana subduction zone by three newly deployed ocean-bottom seismographs (OBS) networks. We process data by using both conventional seismic data processing techniques and recently developed Machine Learning (ML) earthquake detection techniques. This is the first time that the ML earthquake detection methods are applied to OBS observation data at the southern Mariana trench. Our result gives new insight into the fault and seismicity in the Southern Mariana subduction zone. We utilize machine learning-based earthquake detection methods (PhaseNet and EQTransformer) in the first two near-field data and locate the detected earthquakes by using both absolute and relative earthquake location methods. More than 1975 earthquakes are detected, of which 1972 earthquakes are relocated. The location result reveals a heterogeneous distribution of seismicity with a cluster of outer-rise events. The precise location of the cluster events reveals an outer-rise fault that reaches a depth of 50 km and strikes in the same direction as the inherited seafloor fabrics, indicating that there might be larger water input in the southern Mariana Trench than in the previous estimation. The location result of all three data sets also reveals significant along-strike variations in seismicity density and depth distribution pattern, based on which we inferred double seismogenic zones (DSZs) in the eastern region of the slab but a lack of such feature in the western region. We suggest that the dehydration embrittlement of the subducted plate controls the generation of IDEs in the study area. Keywords: Outer-rise fault, Mariana subduction zone, EQTransformer, Ocean Bottom Seismometer, Intermediate-depth earthquake.
SE05-A033
Late Paleozoic to Cenozoic Deformation of the Qilian Shan, NE Tibetan Plateau: Insights from the Huangcheng Basin
Jiabao JIA1,2+, Wenjun ZHENG1#, Renjie ZHOU2
1Sun Yat-sen University, China, 2The University of Queensland, Australia
The Qilian Shan in NE Tibetan Plateau has recorded the deformation history during the closure of the Paleo-Tethys Ocean and northeastern growth of Tibetan Plateau. We focus on the Huangcheng Basin where origins of Late Mesozoic sediments and styles of deformation of faults-folds systems remain controversial. Based on field mapping, fault locations and their correlations fault-folds systems are identified. We also documented two sets of slickensides on fault planes and typical sections of basin stratigraphy. Eleven detrital zircon samples from the Cretaceous to Neogene were collected for detrital zircon U-Pb dating and trace element analysis. Among the two sets of slickensides, one shows NE-SW movement while the other implies E-W compression. Zircon U-Pb ages show major peaks around 265 Ma and 455 Ma. There is also an age-dependent trend of zircon Eu/Eu* values. Our preliminary results suggest that the study region might have experienced three episodes of compression from the 400 Ma to the Neogene. The first episode may represent crustal thickening at ~350 Ma. The second episode is characterized by NNE-SSW trending compression, which could reflect the convergence between the Alashan block and Qilian Shan-Nan Shan block. The third episode reflect tectonic activities related to the regional strike-slip motion. We also infer that Neogene sediments were sourced from the Qilian Shan while Cretaceous sediments were sourced from the North China Craton and Alashan Block.
SE05-A036
Magnetostratigraphy of the Laolongwan Basin in the Northeastern Margin of the Tibetan Plateau and Its Tectonic Significance
Kang LIU1#+, Weitao WANG1, Renjie ZHOU2
1Sun Yat-sen University, China, 2The University of Queensland, Australia
Understanding the activity periods of the Haiyuan Fault, a major boundary fault on the northeastern margin of the Tibetan Plateau, is of great significance for understanding the expansion of the Tibetan Plateau. The Laolongwan Basin is a Cenozoic sedimentary basin developed within the Haiyuan Fault zone on the northeastern margin of the Tibetan Plateau. Its sedimentary evolution provides a detailed record of the tectonic deformation process along the Haiyuan Fault since the Cenozoic. Here we present evidence for inception and evolution of the Laolongwan basin, based on magnetostratigraphy combined with cosmogenic nuclide burial ages that date the basin fills to be from ca.14 to 0.8 Ma. Angular unconformity and growth strata indicate that the Haiyuan Fault underwent two tectonic activities ca.14 and 3.4 Ma. Evidence for 10 to 15 Ma widespread synchronous deformation throughout the Tibetan Plateau and its margins suggests that during this period, the Cenozoic deformation along the northeastern Tibetan Plateau reached their modern extent.
SE05-A038
Multi-stage Growth Process Since the Cenozoic in the Northern Margin of the Tibetan Plateau
Hulu JING#+, Weitao WANG
Sun Yat-sen University, China
The Cenozoic deformation of the surrounding area of the Tibetan Plateau is an important window to understand the pattern of plateau expansion. Tianshan is a typical Cenozoic resurgent orogenic belt affected by the remote effect of the India-Eurasian plate collision. The Cenozoic foreland deposits in the northern piedmont have recorded the evolution process of Tianshan in the Cenozoic. Constrained by the chronological framework of North Tianshan magnetostratigraphy, sedimentation rate changes and terrain simulations based on the foreland basin morphology revealed by seismic reflection profiles indicate that the North Tianshan piedmont has experienced three periods of growth since ~ 26 Ma, ~ 15 Ma and ~ 6 Ma. The deformation since about 30 Ma and 15 Ma widely existed in the northern and northeastern margins of the Tibetan Plateau, which indicates that the growth of the surrounding areas of the Tibetan Plateau is a quasi-synchronous process.
SE05-A039
Plio-Pleistocene Depositional and Tectonic History of Sulawesi Based on U-Pb Zircon Geochronology and Heavy Minerals of the Sedimentary Rocks in Palu, Indonesia
Abang SURYA1#+, Juliane HENNIG-BREITFELD2, Robert HALL2
1Nanyang Technological University, Singapore, 2Royal Holloway University of London, United Kingdom
The Celebes Molasse in Palu has generally been considered to be associated with the Pliocene collision. However, sedimentological, provenance, and zircon geochronological analyses suggest that the sedimentary unit was deposited in an alluvial fan to braided river setting as the syn-orogenic deposit that records gradual uplift rocks related to Neogene extension. The youngest zircon age from this study gives the maximum depositional age of c. 2.5 Ma. Heavy minerals indicate a mixed source from acid to basic igneous and metamorphic rocks, which are now widely exposed in the Neck and west Central Sulawesi. Detrital zircons show a single Proterozoic zircon, a prominent Mesozoic age population with a Triassic peak, and a significant Late Cenozoic peak similar to zircon populations analysed from metamorphic and granitoid rocks in the Neck and west Central Sulawesi. These characteristics differ from the so-called Celebes Molasse formations related to the Sula-Spur collision in eastern Sulawesi. Variations in depositional time, sediment composition and sedimentation history suggest that the ‘Celebes Molasse’ term causes confusion and is too general to provide detailed depositional history for the sedimentary basins across Sulawesi.
SE05-A041
Time Constraint on Danangou Mammalian Fauna in the Nihewan Basin, North China
Ping LIU#+
University of Chinese Academy of Sciences, China
Nihewan Basin is one of a series of well-developed East Asian Cenozoic basins, located in Hebei Province, North China. It has abundant gullies developed along both banks of the Sanggan River and Huliu River during and after the demise of Nihewan paleo-lake, creating a number of outcrops of the Nihewan Beds of fluvio-lacustrine origin, which are underlain by the Pliocene eolian Red Clay and overlain by the late Pleistocene loess. The fluvio-lacustrine sequence is rich sources of mammalian faunas and Paleolithic sites, thus providing unique insights into our understanding of land mammal biochronology and early human settlements in East Asia. Among the Nihewan Fauna (sensu lato), the Danangou (DNG) fauna is one of the important Pleistocene and Pliocene mammalian faunas in the Nihewan Basin. Except for a biostratigraphy, precise age control on the DNG fauna remains unavailable. Here we report a high-resolution magnetostratigraphic results that stringently constrain their ages. Rock magnetism and thermal demagnetization results show that magnetite and hematite dominate the remanence carriers in the DNG fluvio-lacustrine sequences. High-resolution magnetic polarity stratigraphy indicates that the DNG sequence recorded the Brunhes normal chron, the Matuyama reverse chron and the late Gauss normal chron, yielding the fossil-rich layers of DNG fauna with an age of ca. 1.95 Ma to 1.78 Ma during the Olduvai normal subchron. This result, together with previously published magnetochronology data obtained in the eastern basin, constructs a precise age constraints on the chronological framework of the Nihewan faunas and Paleolithic sites, especially during the Plio-Pleistocene transition.
SE05-A042
Field Observations and Zircon U-Pb Analyses of the Paleoproterozoic Rocks in the Gogeumdo Area, Sw Korean Peninsula
Kyoungtae KO#+
Korea Institute of Geoscience and Mineral Resources, Korea, South
The Yeongnam Massif is one of the Paleoproterozoic tectonic units, which is located in the southeastern part of the Korean Peninsula. The Gogeumdo area, which is the focus of this study, is located on the southwestern margin of the Yeongnam Massif. The study area mainly consists of the Paleoproterozoic rocks, which are covered by the Cretaceous volcanic rocks. Based on field observations, the Paleoproterozoic rocks are divided into metasedimentary rocks and metagranitoids. In addition, the Paleoproterozoic metagranitoids are subdivided into foliated granite, porphyritic granite, and biotite granite. LA-MC-ICP-MS zircon dating shows that the minimum depositional age of the Paleoproterozoic metasedimentary rocks is constrained to be at ca. 1870 Ma based on the metamorphic age of overgrown zircon rims. However, the Paleoproterozoic metagranitoids are emplaced during ca. 1875~1857 Ma. Our results of detailed field observations and geochronological data suggest the presence of Paleoproterozoic strata in the southwestern margin of Yeongnam Massif which is yet to be discussed.
SE06-A003
Petrogenesis and Implications of the Basalts in the Yap Trench, Western Pacific: Constraints from Geochemistry and Sr-Nd-Pb Isotopes
Limei TANG#+
Second Institute of Oceanography, Ministry of Natural Resources, China
The nascent arc magmatism is significant to elucidate the subduction mechanism and early evolution of the subduction zone. For a better understanding evolution process of the island arc, the basalt lavas collected from the north and south of the Yap trench were analyzed for their major, trace and Sr-Nd-Pb isotopes. The results reveal the difference of petrogenesis and implications between the north and south of the Yap Trench. The content of Nb and Ta suggests its mantle source is similar to Mariana Trough which consist of depleted mantle and Sr isotope is higher (0.704 646~0.704 794), indicating it was subjected to alteration of seawater. Combined with the other geochemical characteristics, we considered that the northern lava of the Yap Trench represents the crust of the Parece Vela Basin which was thrusting above the initial Yap Arc during the geological process of the collision between the Caroline Ridge and the Yap Trench. Compared with northern samples from the Yap Trench, the southern samples had lower content of MgO (4.18%~5.14%), TiO2(0.69%~0.80%) and CaO(8.64%~10.25%) and lower ratio of Ti/V(11.56~14.07). The REE pattern is relatively flat which is the typical trace element characteristics of subduction-related igneous rocks. The geochemical characteristics of the lava in the south of the Yap Trench indicate that it is the result of collision between the Caroline Ridge and the Yap Trench, which leads new nascent arc magmatism and increasement of the temperature of Yap Forearc. And the dehydration of the subducted plate in the shallow part of the arc, which induces a new island arc magmatism. Finally, the Yap Trench lava are exposed to the bottom of the trench due to subduction erosion.
SE06-A007
Molybdenum Isotopic Constraints on the Origin of EM1-type Basalts
Liang MA#+
Chinese Academy of Sciences, China
The origin of enriched mantle 1 (EM1) component in the mantle has long been debated. EM1 source of basalts has been variously attributed to recycled sub-continental lithosphere, recycled lower continental crust, or recycled oceanic crust plus pelagic sediments. Molybdenum stable isotope systematics has the potential to resolve this debate, because of the significant isotopic differences between mantle and crustal reservoirs. Here we present molybdenum isotope data for EM1-type continental intraplate basalts from Nuominhe (NMH), Northeast China. The NMH basalts display significant variations in both d98/95Mo and Mo/Ce, and strong correlations between d98/95Mo, Mo/Ce and Hf isotope and trace elements. EM1 end-member of the NMH basalts shows the lightest d98/95Mo and lowest Mo/Ce values. The involvement of continental crust and sub-continental lithospheric mantle cannot account for the light Mo isotopic compositions of the basalts. By contrast, the recycled oceanic crust with pelagic sediments, characterized by low d98/95Mo and Mo/Ce values, is the satisfactory candidate for the EM1 component in the NMH basalts. Our results also suggest a residual slab reservoir with light d98/95Mo values (<0.5‰) in the mantle beneath Northeast China, representing the complementary reservoir to heavy Mo isotope continental crust. Identification of this reservoir makes the Mo isotope system a powerful tracer of crust-mantle interactions.
SE06-A009
Osmium Isotope and Highly Siderophile Element of the Subduction Zone Mantle: Constraints from Data on the Yap Trench Peridotites
Ling CHEN#+, Limei TANG
Second Institute of Oceanography, Ministry of Natural Resources, China
Highly depleted peridotites from the Yap Trench in the western Pacific Ocean have been studied for highly siderophile elements (HSEs) and osmium isotope. The abundance of HSEs in Yap Trench peridotites is extremely low compared with that in oceanic peridotites from the mid-ocean ridge and other subduction-zone environments, indicating the extensive extraction of the sulfde melt. The peridotites have variable 187Os/188Os ratios (0.12043–0.14867), with the suprachondritic 187Os/188Os ratios indicating modification of the mantle wedge by slab-derived fluid and melt and the sub-chondritic 187Os/188Os ratios corresponding to a Re depletion age of 0.24–1.16 billion years. The osmium isotope results suggest that some of the Yap Trench peridotites represent old mantle residue of ancient melting events and old depleted mantle fragments may contribute substantially to the chemical heterogeneity of the oceanic mantle. Chondrite-normalized HSE patterns of the Yap Trench peridortites are heterogeneous and exhibit strong fractionation of platinum-group elements (PGEs) and slight enrichment of Re and Au. The Ru/Ir (1.64–16.12), Os/Ir (0.15–7.19), and Pt/Pd (0.53–13.17) ratios in most of the studied samples are higher than those in CI chondrite (Ru/Ir: 1.49; Os/Ir: 1.06; and Pt/Pd: 1.67). These suprachondritic PGE ratios result from the exhaustion of the base metal sulfde (BMS) and the formation of platinum-group minerals and alloys, such as Os–Ru-rich sulfdes and Pt–Fe alloys, that are selectively enriched with certain HSEs. We recommend that the high oxygen fugacity, hydrous melting, and high degree melting of the subduction-zone mantle may result in the exhaustion of the BMS in highly depleted peridotites, promoting the formation of platinum-group minerals and HSE-rich alloys, in which the HSEs are significantly fractionated.
SE06-A011
Magmatism and Crustal Structure of the Southern Kyushu-Palau Ridge from Seismic Refraction Profiles
Jie ZHANG1#+, Jiabiao LI2, Weiwei DING3, Aiguo RUAN1, Xiaodong WEI3, Pingchuan TAN4
1Second Institute of Oceanography, Ministry of Natural Resources, China, 2State Oceanic Administration, China, 3Ministry of Natural Resources, China, 4Second Institute of Oceanography,Ministry of Natural Resources, China
The Kyushu–Palau Ridge (KPR) is the result of the subduction of the Pacific Plate, separated from the proto-Izu–Bonin–Mariana arc by the back-arc spreading, showing variations in arc structures. The internal structure not only reveals the arc characteristics but also contains crisis information about how the arc formed from initial subduction to initial back-arc spreading. However, the less revealed velocity structure in the southern KPR might hinder an understanding of the mechanism of crustal variations. In this work, we model the crustal structure across the southern KPR, using data from two 2D wide-angle seismic profiles. The southern KPR crust is 6.0-11.0 km (Vp=1.9-7.0 km/s) without developing a distinct middle crust. The across-ridge diversities in arc structures suggest that the KPR is not a uniform magma body but comprises several independent seamounts with different periods of magmatism. By analyzing the evolution of the KPR, we conclude that multiple volcanic sources and episodic magmatism caused the diversities in arc structures. This research was granted by the Scientific Research Fund of the National Natural Science Foundation of China (91858214, 42025601, 42276075).
SE06-A016
Experimental Constraints on the Potential Significance of Rodingite in the Mantle
Yu WANG1#+, Yi-Xiang CHEN2
1Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, China, 2University of Science and Technology of China, China
Rodingites are calcium-rich silica-undersaturated rocks formed by metasomatic alteration (rodingitization) of mainly gabbros and basalts, and are often found associated with serpentinite. They are commonly composed of Ca-minerals including grossular, vesuvianite, epidote, prehnite and diopside, and have been documented in various tectonic settings, such as active seafloor spreading centers, rifted continental margins, greenstone belts, and orogenic belts. However, as an important component in both oceanic lithosphere and in ophiolites, the significance of rodingite in affecting mantle heterogeneity through subduction has been long overlooked, and the melting process of rodingite in the mantle remains poorly constrained. Here we report the first HTHP experimental results on partial melting of rodingite in the mantle to investigate the PT stability of both regular and dehydrated rodingite, compositions of the melts and residual facies, elemental behaviors, and the potential significance of rodingite in altering the oxidation state and compositional heterogeneity in the mantle.
SE06-A020
Seismic Evidence for Mantle Heterogeneity Caused by Trapped Water in the Southwestern South China Sea
Jinyu TIAN1+, Zhitu MA2, Jian LIN3#, Min XU4, Xun YU2, Ba Manh LE3, Xubo ZHANG4, Fan ZHANG5
1Shanghai Jiao Tong University, China, 2Tongji University, China, 3Southern University of Science and Technology, China, 4Chinese Academy of Sciences, China, 5South China Sea Institute of Oceanology, Chinese Academy of Sciences, China
Water is the most common volatile component inside the Earth. A substantial amount of water can be carried down to the interior of the Earth by subducting plates. However, how the subducted water evolves after the subducting slab breaks off remains poorly understood. Here we used the data from a passive seismic experiment using ocean bottom seismometers (OBSs) together with the land stations to determine the high-resolution, three-dimensional seismic structure of the Southwest Sub-basin (SWSB). At depths below 40 km, the mantle shear-velocity beneath the northern side of the SWSB is similar to that of the conventional oceanic pyrolite mantle, but roughly 3% shear-velocity reduction was found beneath the southern side of the SWSB. Results of thermal dynamic modeling reveal that the observed significant shear-velocity reduction could be explained by the presence of 150–300 ppm of water and 5–10% of lower continental crust. The inferred high-water content at the southern side of the SWSB is consistent with a model in which the Proto-SCS plate subducted southward prior to and during the formation of the SCS basin, releasing water into the upper mantle of the SWSB.
SE06-A023
Sedimentary Budget of the Okinawa Trough Since the Middle Miocene
Haiqin WANG1#+, Weiwei DING2
1Second Institute of Oceanography, Ministry of Natural Resources, China, 2Ministry of Natural Resources, China
The Okinawa Trough (OT), a back-arc basin formed by the subduction of the Philippine Sea Plate into the Eurasian Plate, is the receiving end of the sediment transport from the Asian continental margin to the sea. So it is the key place to study the source-sink process in the continental margin of East Asia. As the average water depth in this area exceeds 1000 m, it is difficult to carry out extensive drilling exploration in this area, so it greatly limits the systematic and long-term sedimentary process research. Based on 45 multi-channel seismic lines covering the OT, the sedimentary budget and spatial distribution characteristics of thicknesses in different geological periods are obtained, and the controlling factors and possible sources are discussed. The results show that the sedimentary budget of the OT have been increasing since the Middle Miocene. On the one hand, the sedimentary budget of the middle segment (MOT) and the northern segment (NOT) increased similar before the Middle Pleistocene, but NOT decreased after the middle Pleistocene. On the other hand, before the early Pleistocene, the total sediment budget in the southern segment (SOT) was low and increased rapidly since the early Pleistocene. Changes in sediment budget are mainly controlled by the the multi-stage expansion of the OT, and are also strongly related to river development in East Asia and global sea level changes. in addition, global climate change can accelerate or slow down the continental erosion. Temporal and spatial distribution of sediments in the OT indicates that the contribution of sediment sources to basin filling is different in different geological periods. In this study, the semi-quantitative constraints on the sedimentary processes of the OT have improved the understanding of the source-sink processes of the East Asian continental margin. Keywords: Okinawa trough; sediment budget; controlling factors; sediment provenance.
SE06-A024
Zircon U-Pb and Hf Isotopic Constraints on the Tectonic Event in West Java
Yu-Ming LAI1#+, Wai-Ki LEUNG2, Sun-Lin CHUNG3, Iwan SETIAWAN4, Hao-Yang LEE2, Lediyantje LINTJEWAS5, Yoshiyuki IIZUKA2
1National Taiwan Normal University, Taiwan, 2Academia Sinica, Taiwan, 3National Taiwan University, Taiwan, 4Indonesian Institute of Sciences, Indonesia, 5National Research and Innovation Agency, Indonesia
The western Sunda Arc is located in the southern margin of the Sundaland in Southeast Asia. The subduction system can be separated into two parts: the Sumatra arc is oblique subduction, whereas Java Arc is a normal one. Sunda Strait is the transition zone between these two arc systems, the different stress directions of tectonic setting eventually lead to the opening of Sunda Strait. However, when did the Sunda Strait open is still debated. Here we present zircon Hf isotopic data with known U-Pb ages in the western part of the West Java. According to these data, we deduce the time of slab tearing beneath the western West Java-Sunda Strait area and the Sunda Strait opening. A total 102 zircon Hf isotopic data from 14 andesites in Danau Volcanic Complex, Ciemas area, North and South Bayah Dome were analyzed. Miocene to Pliocene zircons (17.0 to 5.0 Ma, n = 76) with higher εHf values from +15.3 to +9.6 while Quaternary zircons (1.0 to 0.4 Ma, n = 26) with lower εHf values from +7.5 to +1.2. Zircons with higher εHf values are similar to the eastern Sumatra (15 to 13 Ma and 4 to 0 Ma, εHf values = +18 to +7) which can be referred to the ‘normal Sunda Arc magmatism’ signal. However, the lower εHf values from Quaternary zircons needs another enriched component to contribute. We refer to several previous tectonic modals beneath the western West Java-Sunda Strait area, and we suggest a slab tearing caused asthenospheric extra heat to melt the subducted sediments during 5.0 to 0.7 Ma according to our data. We further argue that the slab tearing was as a result of the opening of Sunda Strait. Therefore, the time of Sunda Strait opening might not younger than 1 Ma.
SE06-A026
Slab Breakoff Induced by Seamount Subduction at the Java Trench
Dan LIANG1#+, Weiwei DING2
1Shanghai Jiao Tong University, China, 2Ministry of Natural Resources, China
Slab windows or holes have been observed along circum-Pacific zone. Slab break-off mechanism is gradually to be a debated topic. According to the studies of several regions, high bathymetric collide with trench which may be the main factor in slab break-off information, such as Nazca plateaus subducted beneath North America continent, Zhenbei-Huangyan Seamount Chain subducted in the southern part of the Mariana Arc. Java subduction zone is located at the southernmost part of the southeast Asian subduction zone. Since the middle Eocene (about 45 Ma), the Indo-Australian plate has subducted northward to the southern Java Trench. The recent geophysics research suggested the existence of the slab tears between 250-450 km, including P-wave tomography, S-wave splitting results. Meanwhile, the intraplate volcanoes in Central Java are potassic (K)-rich and have been hypothesized to be caused by a supply of volcanic material in the deeper asthenosphere. We suggest that seamounts play a significant role in the subduction process of the Australian plate and the possible formation of the slab break-off in the Java. We designed a serials of numerical modeling experiments with variable parameters to discuss the slab break-off mechanism, which including plate convergence velocity, the age of slab, subduction angle, seamount size and lithospheric rheology. Generally, seamount with weak lithospheric rheology or fault-weakening lead the slab to breakoff more easily. The convergence rate is a key parameter affecting the break-off timing and depth. It’s difficult for seamount subduction to breakoff under fast velocity. Slab age shows complex rheological behavior in the process of plate subduction and detachment. The result of model is consistence with tomography of Java.
SE06-A027
The Oceanic Crustal Structure and the Magmatic Accretion History of the South China Sea
Chenghui ZENG1#+, Zhen SUN1, Yongjian YAO2
1Chinese Academy of Sciences, China, 2Guangzhou Marine Geological Survey, China
Plate separation is accommodated by magmatic accretion and tectonic extension, it is important to study the plate dynamics based on the ratio between them. The South China Sea (SCS) is symbolic of the slow-intermediate spreading marginal sea. However, there is lack of holistic quantitative calculation of the magmatic accretion from the perspective of spatio-temporal distribution, which limits the cognition of the seafloor spreading process of the SCS. We calculate the spatial distribution characteristics of M number, which marks the ratio of separation accommodated by magmatic accretion, in the SCS through seismic profiles. The main conclusions are:(1) The M number of the SCS fluctuates in the range of 0.5~0.95. For each sub-basin, the M of the main spreading area of the northwest sub-basin (NWSB) of the SCS can reach above 0.9. In the east sub-basin (ESB), the M can be above 0.9 and a few areas can be as low as 0.7~0.8 in the early spreading stage (> 23.6 Ma). In the late spreading period (< 23.6 Ma), the values of M number vary alternately between 0.5~0.8 and 0.8~0.95 along the single seismic profile or along the single magnetic anomaly lineation in the ESB and the southwest sub-basin (SWSB).(2) When the M number attain 0.93, planar faults are developed in the oceanic crust, the horizontal displacement is less than ~0.5 km. When the M value decrease to 0.66, low-angle detachment faults are developed, the horizontal displacement can reach ~3 km. The dip angle of fault plane is less than ~30°.(3) We speculated that the mantle serpentinization began to occur when the M number decrease between 0.7~0.8. Because the M number of SCS is generally greater than 0.5, serpentinized mantle exhumation is difficult to occur.
SE06-A028
Bifurcation of Mantle Plumes by Interaction with Stagnant Slabs in the Mantle Transition Zone: Evidence from Late Cenozoic Basalts Within Southeast Asia
Fan YANG1#+, Xiao-Long HUANG2, Yigang XU3
1Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), China, 2Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, China, 3Guangzhou Institute of Geochemistry, China
Mantle plumes and plate tectonics, the two basic geodynamic systems operating on Earth, frequently interact. One of the interaction scenarios is that mantle plumes encounter stagnant slabs in the mantle transition zone (MTZ) during their ascent from the lower mantle to Earth’s surface, which remains poorly understood. Here we present new data on a spatial thermal–lithological–chemical heterogeneity in the mantle over a vast area of southeast Asia that reflects variable influence of a late Cenozoic mantle plume. Mid-ocean ridge basalts (MORBs) in the southwest sub-basin of the South China Sea (SCS; IODP Site U1433) locate near the center of the seismically imaged mantle upwelling. They are derived from a peridotite-dominated and normal temperature mantle source with a depleted Nd–Hf and enriched 207Pb/206Pb isotopic composition. In contrast, MORBs from IODP Site U1431 within the eastern sub-basin of the SCS and other intraplate basalts from the Hainan–Leizhou area, the eastern Indochina block, and elsewhere in the SCS are dominantly sourced from higher temperature pyroxenite-enriched mantle material that records mantle plume activity. These observations are contrast with previous models involving a s ingle plume rising from the lower mantle beneath the SCS that then tilted toward Hainan Island. Instead, the observations from this region maybe indicative of plume–stagnant slab interaction. The shallow upper mantle beneath Site U1433 has not been influenced by a mantle plume as the presence of stagnant slabs within the MTZ prevented further upwelling of the plume. In contrast, a mantle plume passed through the weaker MTZ within the eastern sub-basin and circum-SCS areas, allowing plume-related magmatism to occur. The bifurcation of a deep-rooted mantle plume by stagnant slabs in the MTZ produced a cluster of small mantle upwellings that ascended to shallow depths, consistent with new multiscale global tomographic data for southeast Asia.
SE06-A030
Hydrous Mantle Induces Rapid Continental-oceanic Transition of the South China Sea Rifted Margin
Zhiyuan ZHOU1#+, Jian LIN2
1Southern University of Science and Technology, China, 2Woods Hole Oceanographic Institution, United States
Recent investigations of IODP Expeditions 367/368 have revealed that the transition from continental to oceanic lithosphere is surprisingly fast and mantle exhumation and serpentinization is not observed at the South China Sea (SCS) continental margin. It makes SCS margin significantly different with typical magma-poor margin such as the Atlantic Iberia–Newfoundland margin. Recent studies imply that SCS margin might be a magma-moderate margin with a hot mantle. However, the mechanism for rapid continental-oceanic transition of the SCS margin is still enigmatic though it is hypothesized to be related to subduction. Here we establish a model of continental rifting and breakup due to extension and mantle upwelling, in which we innovatively incorporate the water content in the asthenosphere mantle to quantitatively evaluate the effect of hydrous mantle on the rifting and breakup processes of the SCS margin. Modeling results reveal that a low-moderate mantle temperature (1,300 – 1,350 °C) is required to form both a failed rift center and a successful breakup point. Moreover, significant water (100-300 ppm) in the asthenosphere beneath the SCS margin is required to cause both rapid continental-oceanic transition and enough magma for observed large crust accretion at initial spreading center. It is further hypothesized that the preceding subduction before continental rifting might bring substantial water into the mantle beneath the SCS margin and accelerate mantle upwelling and continental breakup. Furthermore, our models reveal that melt migration could induce significant asymmetry in crustal underplating on the two conjugated margins, explaining the observed asymmetric high-velocity layer at SCS margin. Our models provide new insights to the origin and evolution of most of the marginal seas at the western Pacific Ocean, which are highly influenced by subduction processes.
SE06-A033
Suture Zone of Paleo-Pacific Ocean and Tectonic Inheritance in Rifting of the South China Sea Continental Margin: Revealed by Deep Seismic Profile
Zongdong PAN1+, Shaoping LU1#, Han CHEN1,2
1Sun Yat-sen University, China, 2Southern Marine Science and Engineering Guangdong Laboratory, China
The Northern South China Sea (SCS) margin, roughly includes the continent-ocean boundary (COB) and the South China Block margin, which has transformed from a Mesozoic active continental margin to a Cenozoic passive continental margin. The evolution of the South China block is considered to have been influenced significantly by the subduction of the paleo-Pacific plate since the Mesozoic as evidenced by widespread igneous rocks. However, the mechanism of the transition from active continental margin to passive continental margin and the opening of the SCS is inconclusive. the location of the ancient Pacific suture zone is also controversial. Paleo-suture zone corresponds to “weak” structures and is a key factor influencing the evolution of rifting and seafloor opening. According to tectonic inheritance, the closed remnants of the destroyed paleo-Pacific in the SCS region represent the suture zone. The precise location of the suture zone is crucial in understanding the rifting history of the SCS region. The deep seismic reflection profile can provide information on crust-mantle structure, which can be correlated to surface geological information and provide key evidence to reveal the evolutionary history of the tectonic assembly. We interpret the deep seismic reflection profile on the northeastern SCS and locate the suture zone of the paleo-Pacific Ocean by combining gravity, magnetic anomalies, and geochemical data. We propose that the SCS opening is initiated at the suture zone of the paleo-Pacific Ocean and tectonic inheritance plays a key role in rifting of the SCS continental margin.
SE06-A036
Crustal Structure and Its Tectonic Significance of the East Subbasin, South China Sea: Seismic Evidence from OBS Refraction/reflection Survey
Lu ZHANG#+, Chen CAI
Sun Yat-sen University, China
The South China Sea (SCS) is one of the largest marginal seas of the Pacific, which is located at the junction of the Eurasian plate, Philippine plate, and Indo-Australian plate. The spreading history and mechanism of the SCS have long been studied and debated. A recent 750-km long north-south trending OBS refraction/reflection seismic profile led by Sun Yat-sen University was carried out across the East Sub-basin, SCS, covering the entire oceanic basin and part of the continental crust to the south. The P-wave velocity model along the line was obtained by forward/inversion of the travel-time picks with Rayinvr program. Taking the fossil spreading ridge (i.e., the Huangyan-Zhenbei seamount chain) as the boundary, the velocity model reveals a thicker northern sub-basin with a mean thickness of ~7.7 km compared to the southern one with a mean thickness of ~5.9 km. The asymmetry feature of crustal thickness of the oceanic basin may be a joint result of the ridge jump event and the melt flow addition caused by the Hainan plume to the northern flank at zero-age crustal accretion. Our result also presents a low-velocity body within the upper crust slightly south of the fossil spreading ridge, suggesting asymmetric serpentinization to the southern flank along detachment faults formed during the last stage slow-spreading episode. We, therefore, recommend that the Hainan plume played an important role in the seafloor spreading process and in shaping the oceanic crustal thickness asymmetry.
SE08-A001
Mantle Source Characteristics of Cenozoic Volcanoes in Central Asia: Constraints from Olivine Compositions and Whole-rock B-Mo Isotopes
Yunying ZHANG1#+, Min SUN2, Chao YUAN3, Zhen SUN3, Qian LIU4
1South China Sea Institute of Oceanology, Chinese Academy of Sciences, China, 2The University of Hong Kong, Hong Kong SAR, 3Chinese Academy of Sciences, China, 4Northwest University, China
Cenozoic continental basalts are diffusely distributed in central Asia, and are dominated by alkaline basalts with subordinate tholeiites and show oceanic island basalt-like trace element features. The geodynamic settings and ultimate magma origin of these basalts remain mysterious, which are largely due to the short of knowledge on their source lithology. Phenocrystic olivine is always the first silicate phase to crystallize from primary basaltic melts and thus could faithfully record information about the magma source. Besides, boron and molybdenum isotope systematics, in the past two decades, have proven to be of great value in tracking recycled oceanic crust in the mantle source of within-plate basalts. Voluminous basalts with ages from 30 Ma to 5 ka and volume up to 2900 km3 erupted in the Hangai dome and Mongol–Chinese Altai region. Representative basalts from the Central Hangai and Chinese Altai were collected for geochemical investigation to constrain their mantle lithology and geodynamic mechanism responsible for the widespread intraplate basalts. The phenocrystic olivines are featured by lower Ca, Mn, Mn/Zn and Mn/Fe but higher Ni than their counterparts in the peridotitic melts, indicating a pyroxenite-rich mantle source. Besides, the light B and variable Mo isotopic compositions of the Chinese Altai basalts indicate that recycled, dehydrated oceanic crust was likely involved in the mantle source, since subduction dehydration preferentially transports heavy 11B and 98Mo to the fluid phase. It is proposed that the pyroxenite was formed by reaction of recycled oceanic crust with its ambient peridotite, based on their light B and Mo isotopic compositions, and negative correlations between B isotopes and B contents, and between oxygen fugacity and olivine Mn/Zn. The far-field effect of India–Eurasia convergence possibly tapped the upper asthenospheric mantle, subsequent melting of which gave rise to the dispersive Cenozoic volcanoes.
SE08-A010
Interaction of the Kerguelen and Amsterdam-St. Paul Dual Hotspots with the Eastern Indian Ocean
Yiming LUO#+, Jian LIN, Zhiyuan ZHOU
Southern University of Science and Technology, China
We investigated the influences of the Kerguelen and Amsterdam-St. Paul (ASP) hotspots on the crustal accretion of nearby spreading ridges in the Eastern Indian Ocean. Gravity analysis and 3-D geodynamic modeling revealed enhanced ridge magmatism caused by Kerguelen and ASP hotspots, resulting in anomalously thick crust. Ridge-hotspot distance and plume flux are key factors controlling the strength of interaction. Our results reveal that in the top 200 km lid, the plate-driven shear flow controls the distribution of plume anomalies, and the plumes links to the nearby ridge due to ridge capture. By comparing the dual hotspots and single hotspot models, we found that the existence of Kerguelen hotspot leads to a ~200 km offset of the temperature and crustal anomalies of ASP, implying potential hotspot-hotspot interaction, which may also apply to other dual/multiple hotspots-ridge systems around the world.
SE08-A014
Unusual Activities Revealed by the Recent Fluid Geochemical Results in the Tatun Volcanic Group, Northern Taiwan
Hsiao-Fen LEE1,2#+, Ai-Ti CHEN3, Yuji SANO4, Ya-Chuan LAI5,6, Min-Hung SHIH7, Cheng-Horng LIN8, Ching-Hua LO3, Guo-Teng HONG9
1National Center for Research on Earthquake Engineering, National Applied Research Laboratories, Taiwan, 2Taiwan Volcano Observatory at Tatun, Taiwan, 3National Taiwan University, Taiwan, 4Kochi University, Japan, 5Taiwan Volcano Observatory - Tatun, Taiwan, 6National Center for Research on Earthquake Engineering, Taiwan, 7National Applied Research Laboratories, Taiwan, 8Academia Sinica, Taiwan, 9Central Geological Survey, Taiwan
The Tatun Volcanic Group (TVG) is an active volcano located in northern Taiwan. Volcanic activity could have significant impacts due to proximity to metropolitan areas. The Tatun Volcanic Observatory has been established since 2011. Its main task is to monitor the seismic activities, patterns of volcanic fluid flows and surface deformations of the TVG. Combined with recent changes in geochemical indicators and seismic event monitoring results, volcanic activities were relatively quiet during 2017-2018. At the end of 2018, there was a deep hydrothermal upwelling, and the exhalation gases of hydrogen chloride in the whole region began to increase. At the same time in 2019, the number of seismic activities increased, and several large-scale and deep-focus seismic events occurred in the TVG area. Helium concentrations of the venting gases increased, while the concentration of hydrogen chloride continued to increase. Numbers of seismic activities peaked in 2020, and then it was observed that the cation concentrations of hot spring of Dayoukeng (DYK) area, the most active area in the TVG, increased sharply in the late 2020. It was possibly due to the upwelling of a large number of deep hydrothermal fluids. Gas and water anomalies continue to occur in 2021, but seismic activities have slowed down as the pressure has been released. According to the surveillance video, in December 2021, a new fumarole appeared above the main fumarole in the DYK area. Surface environmental features also suggest mud splashes from this period. At the same time, several important parameters of fumarolic gas, such as SO2/H2S, HCl/CO2, He/Ar ratios, also changed significantly. The concentration of cations also reached the highest peak. Based on these changes, it is speculated that a small hydrothermal eruption might have occurred in the end of 2021.
SE08-A015
Simulating the Effect of Sea Level Change on Internal Stresses in the Tectonic Plates Along Subduction Zones to Study Its Impact on the Likelihood of Volcanism
Nathan TEO#+, Benoit TAISNE
Nanyang Technological University, Singapore
Prior research suggests sea level rise has an impact on volcanic activity, where, in coastal volcanoes, empirical data suggest volcanism increases with sea level rise. This project aims to explore the effect of sea-level change on various components of the internal stresses within the tectonic plates through finite-element physics simulations in COMSOL. The study is centred around profiles of Sumatra and Java, Indonesia, and Honshu, Japan, which are one of the most active regions in the world. Those two locations are also displaying differences in bathymetry leading to asymmetrical stress changes within the crust. A parametric study of the bathymetric profiles from the two regions is performed, applying the change in pressure attributed to sea level rise or drawdown on the top surface. The change in horizontal stress and gradient of the change in pressure with depth is analysed to infer the impact of sea level change on magmatic rise and consequently volcanic activity. The results of the simulation agree with the empirical data, with sea level drawdown discouraging magmatic rise and sea level rise favouring magmatic rise. Furthermore, a comparison of the asymmetry in the bathymetry between Indonesia and Japan is used to demonstrate significant differences in the stress response to sea level change and implications in volcanism and its location.
SE09-A005
Crustal Attenuation of Lg Wave in Eastern Tibet Plateau
Jing HE1#+, Qingju WU2, Eric SANDVOL3
1National Institute of Natural Hazards, Ministry of Emergency Management of China, China, 2China Earthquake Administration, China, 3University of Missouri, United States
Crust rheology is vital for understanding whether there is a large-scale crustal flow and its role in the lateral expansion of the Tibetan plateau. Here we apply the Reversed Two-Station Method using the waveforms recorded by the dense seismic networks to obtain the crustal Lg attenuation model in eastern Tibet, which is sensitive to crustal rheology, especially the partial melting, temperature, and fracture. Prominent low Q values, i.e., high crustal attenuation, are found beneath the Songpan-Ganzi block, the northwestern Sichuan sub-block, the Xiaojiang fault zone, and the Tengchong volcano. The low Q value in the Songpan-Ganzi block is strictly blocked by large faults, indicating the presence of partially molten crust related to the crustal composition and tectonic deformation. We interpret the geometry of low Q in the Songpan-Ganzi block as the signature of the localized crustal flow controlled by major faults. Low Q anomalies beneath the Xiaojiang fault and its adjacent region indicate a melt-weakened crust, which may be caused by a combination of fractured upper crust formed by the strike-slip faults, heating due to the thickening of the felsic mid-lower crust, and the possible thermal upwelling from the upper mantle.
SE09-A007
Groundroll Suppression in Qiangtang Basin Based on Local Orthogonalization
Xiao PAN#+, Xiaotao WEN
Chengdu University of Technology, China
As one of the large basins in Qinghai-Xizang Plateau, Qiangtang Basin attracts increasing attention. It owns good gas and oil accumulation condition and becomes the best potential reservoir. Seismic survey helps quantitively evaluate the reservoir with high resolution. Due to complex geological condition and unstable acquisition condition, groundroll exists and it masks reflections. In order to get accurate interpretation result, groundroll suppression is necessary to improve seismic data quality. In this paper, we apply local bandlimited orthogonalization method to iteratively separate reflections and groundroll. Compared with conventional FK filter, local orthogonalization has better ability to identify reflections and noise in detail. With the help of bandpass filtering, groundroll can be removed with much less reflection missing. Field data application proves that local bandlimited orthogonalization method works well in Qiangtang Basin and it improves the quality of seismic profile a lot. Good seismic profile helps to get an accurate interpretation result, which improves the understanding of the underground resources.
SE09-A011
The Spatial Distribution and Dynamic Mechanism of Low Viscosity Channels in the Middle and Lower Crust of the Sichuan-Yunnan Region
Bin SHAN#+
China University of Geosciences, China
The Sichuan-Yunnan region is located in the southeastern margin of the Qinghai-Tibet Plateau, plays an important role in explaining the dynamic processes of the uplift of the Qinghai-Tibet Plateau, the deformation of lithosphere and the eastward flow of materials from the Qinghai-Tibet Plateau. Therefore, the deep understanding of the lithospheric structure of the Sichuan-Yunnan region is the key to the recognition of the lithospheric deformation mechanism of the Qinghai-Tibet Plateau. Due to the respective limitations of different research methods, the lithospheric structure obtained for the Sichuan-Yunnan region and the modelling of possible tectonic evolution are still controversial, the lithospheric rheological structure is the basis for the understanding of these controversial issues. This paper constructs the lithospheric temperature structure in the Sichuan-Yunnan region with multiple geophysical observations, then the lithospheric lithological structure is constructed combining the petrology, geochemistry and seismic sounding data, finally this paper constructs the lithospheric rheological structure for the Sichuan-Yunnan region. This paper proposes that the impact of collision and compression between the Indian plate and the Eurasian plate since the Cenozoic era, on the one hand, led to the thickening and partial melting of the crust in the Qinghai Tibet Plateau, and on the other hand, led to the upwelling of deep mantle thermal materials in the southern Sichuan-Yunnan region, and weakened the lithosphere of the IndoChina block and the Sichuan Yunnan Diamond block. The weak material heading eastward from the middle and lower crust of the Qinghai Tibet Plateau can only flow to the Sichuan Yunnan Diamond block with relatively low strength and enter the IndoChina block across the Red-River fault zone, because it is blocked by hard formations such as the Sichuan Basin and Emeishan Large Igneous Province. Therefore, the Sichuan Yunnan region has become an important channel for the outflow of material from Tibet.
SE09-A017
Study on the Coseismic Surface Deformation and Seismic Risk Change Caused by the 2008 Wenchuan Earthquake
Mingqian SHI+, Caibo HU#
University of Chinese Academy of Sciences, China
Coseismic deformation of large earthquakes is an important factor in causing significant property and personnel losses, which requires quantitative research of multiple disciplines such as joint geodesy, geological investigation, seismic tomography, and seismic dislocation theory. The 2008 Ms 8.0 Wenchuan earthquake is one of the most complex and strongest intraplate earthquakes. The Longmenshan fault zone, where the Wenchuan earthquake occurred, has an elevation difference of 4 km. The crustal thickness of the Qinghai-Tibet Plateau and Sichuan Basin beside the fault zone differ by tens of kilometers, and there is an obvious difference in composition. We have carried out a series of parallel finite element models to calculate the coseismic surface deformation of the 2008 Wenchuan earthquake. The parallel finite element models introducing split nodes and high-performance parallel computing technology can consider the effects of the regional material heterogeneity and geometric complexity of the earthquake. The correctness of the parallel elastic finite element program is verified by comparing the results of four ideal earthquake cases with the analytical solutions of seismic dislocation theory. The simulation results of the coseismic deformation of the Wenchuan earthquake are consistent with the geodetic GPS and InSAR data. Based on the coseismic stress field obtained by the finite element models, we calculated the Coulomb stress change on the main faults around the earthquake to evaluate the seismic risk change. The parallel finite element models lay an important foundation for the inversion of the coseismic fracture process based on the inhomogeneous model in the future. This research was financially supported by the National Science Foundation of China (42074117) and supported by the Fundamental Research Funds for the Central Universities.
SE09-A019
Seismological Results Reveal That the Upwelling of Magma Led to the Uplift and Surficial Processes of the Namche Barwa Massif as One of the Most Active Areas
Siyuan CHENG+, Xuzhang SHEN#
Sun Yat-sen University, China
High-resolution imaging of the deep structure in the crust may be an important breakthrough to solve the problem of whether the rapid uplift of the Namche Barwa massif (NBM) is led by extremely high erosional exhumation or controlled by deep tectonics. Based on the seismic data recorded by 400 short-period dense seismic array located in the NBM, 4785 P-wave receiver functions (PRFs) are calculated and selected to obtain the migration image. The results show that there is a large range of weak (or missing) Moho under the Yarlung-Zangbo river in the northern margin of the NBM, and the upper crust is pushed upward in an inverted "V" shape. They are simulated and verified with spectral-element method (SEM). The results reveal that the ultrafast uplift and surface exhumation in the NBM may be caused by the upwelling of magma in the upper mantle, with its channel under the Yarlung-Zangbo river.
SE09-A028
The 2021 Luxian Ms 6.0 Earthquake: A Complete Release of the Localized Compressive Stress on a Limited-size Fault
Chaoliang WANG1#+, Liang CHUNTAO1, Jiangtao LIAO1, Zhenxing YAO2, Rui XU1, Yihai YANG3
1Chengdu University of Technology, China, 2Chinese Academy of Sciences, China, 3Shaanxi Earthquake Agency, China
On 16 September 2021, a destructive earthquake with surface-wave magnitude (Ms) of 6.0 broke the seismic quiescence of the Luxian county in the inner Sichuan Basin, China. Here, we explore the seismogenic structure of the Luxian earthquake by characterizing sedimentary faults in the spatiotemporal distribution of aftershocks, via the focal mechanism solutions and via the coseismic rupture model based on synthetic aperture radar interferometry (InSAR) data. Our results show that aftershocks concentrated at two clusters in the broad syncline. Seismicity of the northern cluster reveals that the main shock ruptured an east-southeast striking fault with a dip angle of ~ 45° to the southwest (F0), and activated a gently dipping (~ 18°) fault (F1) below F0 and a nearly vertical shallow fault (F2) on the northern side of F0. These three faults outline the edges of a thrust wedge in the sedimentary cover. The northern cluster occurred on two conjugate fault systems within which steep faults with different dipping direction interlaced downward forming ‘V’ shapes. Evidences from the aftershock focal mechanisms, Coulomb stress change and the post seismic stress field coherently indicate a reversal of the stress regime from the near north-south subhorizontal compressive stress regime before the main shock to the normal slip favored stress regime with the subvertical maximum principal stress. Further, the apparent deficit of seismicity at the periphery of the coseismic slip area on the fault plane indicates a limited size of the seismogenic fault. All these results indicate that complex fault system developed within the thick sedimentary cover, and inhomogeneous deformation of the sedimentary cover might cause localized stress concentration in the Sichuan Basin during multiple phases of tectonic deformation. We suggest that the Luxian Ms 6.0 earthquake as a typical event completely released the localized compressive stress.
SE09-A031
Magnetic Anomaly Characteristics and Magnetic Basement Structure in Earthquake-affected Changning Area of Southern Sichuan Basin, China: A New Perspective from Land-based Stations
Chao DONG#+
Institute of Geophysics, China Earthquake Administration, China
The Changning area is located in the southern Sichuan basin and the western Yangtze Plate and is the most abundant shale gas exploration area in China. In recent years, Changning has experienced frequent earthquakes with moderate magnitudes, attracting extensive interest. To investigate the magnetic characteristics in Changning, 952 land-based stations were employed to establish a magnetic anomaly model with a resolution of 2 km, and the subsurface magnetic basement structure was obtained by an iterative algorithm in the Fourier domain. The magnetic anomaly model shows significant distinctions between the northern salt mine area and the southern shale gas area. The magnetic basement includes the crystalline basement and the Sinian sedimentary rock metamorphic basement, which has strong magnetism. The large intracratonic rift that developed in the Sinian–Early Cambrian plays an important role in the evolution of Changning, which also impacts magnetic anomalies and the magnetic basement structure. Finally, by comparing the seismic wave velocity ratio structure, the deeper magnetic basement that corresponds to the higher seismic wave velocity ratio can be explained. This article implies that magnetic anomalies and magnetic basement depth have a certain correlation with earthquakes in Changning, and it provides a geodynamic reference for Changning and the southern Sichuan basin.
SE09-A038
Seismic Imaging of Crustal Structure Underneath the Foreland Basin and Siwalik in Nepal Himalaya Using Receiver Function Modeling
Sushrat MISHRA1#+, Kajaljyoti BORAH2, Aakash ANAND2, Pousali MUKHERJEE3, Dipok BORA4
1Indian Institute of Science Education and Research, Kolkata, India, 2Indian Institute of Science Education and Research Kolkata, India, 3Kyoto University, Japan, 4Diphu Government College, India
Flexure of the down-going Indian plate beneath the overriding Himalayas resulted in the formation of the Himalayan foreland basin. The thick sediments in the basin can cause local site amplification of seismic waves generated even from small-magnitude earthquakes. Also, due to these thick sedimentary layers, the underlying structure beneath the foreland basin and adjoining Siwalik becomes highly unreachable, and the dominance of multiples in the receiver function due to the sedimentary phase makes crustal imaging highly challenging. Hence the proper seismic image of the crustal structure is extremely important not only to assess seismic hazard in the region but also to get a handle on the mountain-building activity. We investigated the thickness and composition of the sedimentary layer and crust using H-κ stacking and NA (Neighbourhood Algorithm) modelling of receiver functions at 26 seismographs operated in the Siwaliks and Indo-Gangetic Plain in the Eastern Nepal Himalaya. Our study shows that in the foreland basin, sediment thickness varies from ~4.1-5 km, with Vp/Vs varying between ~2.31-2.78. In the Siwalik, the sediment thickness and Vp/Vs ratio are ~2.5-3.5 km and ~2.14-2.78, respectively. Similarly, the thickness and average Vp/Vs ratio of the crust in Indo-Gangetic Plain (IGP) and Siwaliks vary between ~40-44 km, 1.8-1.86 and 42.5-46 km, 1.77-1.87, respectively. In the first ~1-1.5 km of the sediment layer, we have observed very low Vs (<1.5 km/s) due to the very loose sediments having high seismic hazard potential. The average values of Vp and Vs suggest that in the sedimentary layer, the most probable rocks are sandstone and mudstone. Similarly, the possible lower crustal rocks underneath the IGP and Siwalik vary between Mafic garnet granulite and Mafic granulite. Our result has implications for modelling of mountain building activity and seismic hazard assessment in the region.
SE09-A041
Performance of LD-Array During the 2022 Mw 6.6 Luding Earthquake, Sichuan, China
Xinzhong YIN1#+, Qibin SHI2, Wenze DENG3, Jiuhui CHEN1, Shengji WEI4
1China Earthquake Administration, China, 2University of Washington, United States, 3China Earthquake Networks Center, China, 4Nanyang Technological University, Singapore
The 5 September 2022 Mw6.6 Luding earthquake (LDEQ) occurred on the Moxi segment of the highly active Xianshuihe fault (XSHF) zone in eastern Tibetan Plateau, in Sichuan Province, China, causing 93 casualties and 24 people missing, and substantial damages in the epicentral regions. The Luding Array (LD-Array) is covered the mainshock area. The LD-Array is consists of three types of seismographs, including low-cost acceleration intensity sensors (758), strong motion meters (323) and broadband seismographs (106). Using a path-calibration method, we select the highest quality strong motion and broadband stations mostly on the bedrock sites to derive a Multiple-Point-Source (MPS) model for the mainshock. We then perform joint inversion on the static GPS, strong motion and teleseismic body waves to obtain a finite fault model of the mainshock. This is followed by forward modeling of all the LD-Array stations to verify the array performance. The array observations are also used to test the recent ground-motion prediction equations (GMPE) for the Southwestern parts of China. We find: 1) The MPS model composes of three major subevents that are distributed in a compact area where the aftershock seismicity shows a clear gap. 2) Finite fault model shows a compact slip distribution with along strike dimension of ~14 km. 3) LD-Array clearly captured the rupture directivity of the mainshock. Most of the amplitude of the low-cost acceleration intensity sensor waveforms are reliable and part of waveforms could be modeled. The GMPE from Zhao et al. (2017) generally fits well the PGA from observations, but there is still room for improvement, such as considering azimuthal variation (i.e. focal mechanism); 4) The LD-Array can be applied to other areas to enable seismological research such as seismic event detection and location, deep structure imaging, earthquake source physics, as well as earthquake early warning.
SE09-A042
Study on Present Gravity Change and Deep Crust Deformation of the Red River Fault Zone
Jian WANG#+
China Earthquake Administration, China
In order to detect the current material migration and deformation characteristics in the crust along the Red River fault zone (RRFZ), we analyzed and removed the gravity changes caused by vertical surface movement, surface water circulation, denudation, and glacial isostatic adjustment effects based on mobile gravity observation data of 3 profiles in the northern and middle section of the RRFZ from 2013 to 2019, and obtained the trend of gravity change caused by the migration of materials in the deep crust. Based on recent gravity changes and crustal structure models, the deformation characteristics of Moho surface along the northern, middle, and middle- southern sections of the RRFZ are inverted. The results shows gravity change of the RRFZ has segmental characteristics, gravity change rate of the northern /middle/ middle-southern section of the RRFZ are -0.39±1.30, 0.16± 1.57, 0.29±1.25μGal/a. Moho beneath the RRFZ uplifts continuously with an average rate of 0.54 cm/a in recent period. Average deformation rate of the northern, middle, and middle-southern section of the Red River fault zone is -0.06 cm/a, 1.36 cm/a and 0.32 cm/a, reflecting the effect of regional unbalanced tectonic movement to a certain extent.
SE09-A047
Implications of Various Magnitude Scales in Western China
Zujun XIE#+
China University of Geosciences, China
Magnitude is a parameter measuring the size of an earthquake, yielding units of order 1 which are intuitively attractive, and is indispensable in seismic scientific research and seismic hazard assessment. The definition of magnitude has various scales, like ML, mb, MS (MS_BB), mB (mB_BB) and MW, based on different calibration. The discrepancy of the definitions results in the commonly different values, mainly because of diverse seismic phases and frequent bands adopted. Although magnitude conversions are often proposed for scientific research purpose, such as seismicity analysis, their differences revealing the different characteristics of seismic sources should be deserved more of a concern. In this study, the waveform of earthquakes of M > 4.5 in western China since 2009 have been collected and three magnitude scales, MS(BB), mB(BB), re-estimated according to the New National Standard of Magnitude issued in 2017 in China and MW, assessed by waveform inversion, are compared and analyzed statistically. The results show, (1) differences between magnitude scales depend on the research region, implying the differences between tectonic environments. Earthquakes with large MS and mB relative to MW correspond to regions with stronger crustal lithosphere strength, suggesting the accumulated stress on the faults are probably more higher. Contrarily, earthquakes with large MW relative to MS and mB are prone to rupture on the mature seismic faults, implying that the heterogeneities of fault zones maybe not relatively distinct. (2) differences between various magnitudes also rely on the source type of focal mechanism, which may reflect the different frictional strength. (3) those events occurred in the neighboring region, with similar MS (mB) but significant discrepancy of Mw indicate the different rigidity of the medium structure in the local area near the fault zones, which has relatively significant influence on the magnitude of MW.
SE10-A002
Pumice Erupted by Fukutoku-Oka-no-Ba Observed in and Around Taiwan from Satellite Imagery
Sin-Mei NG#+, Hong-Xuan CHEN
Chinese Culture University, Taiwan
Fukutoku-Oka-no-Ba (FOB), a submarine volcano, is situated at approximately 60 km south of Loto Island in the Ogasawara Islands (also known as the Bonin Islands) which are, in turn, a part of the Izu–Bonin – Mariana (IBM) arc system in the eastern Philippine Sea. On 13th August, 2021, a large eruption occurred; and it ended two days later. An approximately 1 km, horseshoe-shaped, new island was formed and reported by the Japan Coast Guard on 15th August, 2021. Besides the formation of the new volcanic island, the large submarine eruption also produced a large quantity amount of pumice. A week after the eruption, pumice with gray, vesicular, and having a groundmass that contains black enclaves were collected in the ocean near FOB. Clinopyroxene, plagioclase and rare olivine phenocrysts were found in the pumice clasts. By the end of November, the drifting pumice had already reached the Green Island in the southeast; and, by the early to mid-December, it appeared in the northern coast of Taiwan. The sudden surge of large amount of pumice from the FOB eruption in the coast may cause marine hazard. Previous studies integrated multiple optical and SAR data to investigate similar pumice raft events and tracked the sequential motions. Pumice is rhyolite glass in which expanding gas bubbles have distended the magma to form a highly vesicular material. In this poster, we are going to show the trace of pumice in and around Taiwan region seen by satellite imagery.
SE10-A010
Tectonic Vertical Land Motions in Southeast Asia Through the Lens of Geodetic Observations and Earthquake Deformation Models
Grace NG1#+, Dongju PENG1, Lujia FENG1, Xin ZHOU2, Haipeng LUO3, Kelin WANG4, Chien Zheng YONG5, Susilo SUSILO6, Irwan MEILANO7, Emma HILL1
1Nanyang Technological University, Singapore, 2Ministry of Emergency Management of China, China, 3University of Victoria, Canada, 4Geological Survey of Canada, Canada, 5University of Otago, New Zealand, 6National Agency for Research and Innovation, Indonesia, 7Bandung Institute of Technology, Indonesia
Regional sea-level changes in Southeast Asia are highly variable due to the influence of both climate and solid Earth processes. In particular, vertical land motions (VLM) due to tectonics are a major source of local spatial variability and uncertainty owing to recent earthquake history and mantle dynamics at regional subduction zones. Over the last two decades, the Sumatran subduction zone hosted a series of large earthquakes starting with the 2004 Mw 9.2 Sumatra-Andaman earthquake. These large earthquakes not only rapidly changed land heights by several meters near the earthquake locations, but also induced longer-term changes in the distant back-arc regions through broadscale mantle processes. At some locations, the tectonic VLM changes can be comparable to or greater than climate-induced sea-level changes. Thus, to generate accurate and robust regional sea-level projection models for coastal risk assessment and adaptation planning, it is imperative to quantify the contribution of tectonic VLM. To quantify the tectonic VLM, we use a variety of modelling techniques to estimate the surface deformation caused by the recent earthquakes, focusing on the postseismic viscoelastic relaxation process controlled by the mantle rheological structure. To constrain our models, we employ new techniques to derive VLM from satellite altimetry and tide gauge data to supplement GNSS observations that are often limited by spatial and temporal availability in our region. From our results, many Southeast Asian countries – including Thailand, Peninsula Malaysia, and Singapore – are vulnerable to postseismic subsidence following the Sumatran earthquakes. The broad subsidence can last for years or even decades. Though some of these countries are far from the trench and the rate of subsidence is small, the total cumulative subsidence over many years is non-negligible and adds to the climate-induced relative sea-level rise.
SE13-A003
Empirical and Physical-based Waveform Simulations for Moderate-large (M6+) Earthquake Scenarios in Taiwan
Min-Hsuan CHANG#+, Yen-Yu LIN, Ming-Che HSIEH
National Central University, Taiwan
Earthquake early warning systems have been used to mitigate injuries and damage worldwide for many years. To improve the efficiency of the systems, more studies account for machine learning approaches to predict the intensity distribution without calculating magnitude and location of the event. However, lack of seismic records for moderate-large (M6+) earthquakes may give unstable extrapolations while predicting intensities. To fill the lack, we demonstrate two approaches, the empirical Green's function (EGF) and the strain Green's tensor (SGT), in simulating seismic waveforms for moderate-large earthquake scenarios in Taiwan. In the EGF approach, we first compute the relative source-time function (RSTF) between the small event with the observed waveforms and the scenario event. We then convolve the RSTF and the observed waveforms to simulate the waveforms of the scenario event. On the other hand, the SGT approach allows us to perform synthetics of the scenarios physically, considering possible rupture dimension, speed, asperity, as well as 3D velocity structure and site effect. Here, three M6+ events in Taiwan, the 2013 Nantou, the 2016 Meinong, and the 2019 Hualien earthquakes, are selected to validate the two approaches. In the EGF approach, the intensities from the synthetic waveforms are similar to those from the observations in the frequency range of 0.2~1 Hz for all events. However, the synthetics of the SGT approach show good intensity predictions for the Hualien event but underestimated intensities for the Nantou and the Meinong events in the same frequency range. It may be due to the underestimates of site effect, which needs further investigation. Our results suggest that both approaches may fill the lack of seismic records for moderate-large earthquakes and have the potential to provide synthetic data as inputs for adjusting the available ground motion models and even machine learning for early warning.
SE13-A004
Relationship Between Inland Seismicity and Crustal Deformation After the 2011 Tohoku Earthquake Derived from the Refined Earthquake Catalog
Koji TAMARIBUCHI#+, Hisao KIMURA
Meteorological Research Institute, Japan
After the 2011 Mw 9.0 Tohoku earthquake, seismic activity increased throughout Japan. Due to the large number of earthquakes, microearthquakes (M<2 inland, M<3 offshore) were not always catalogued, making it difficult to comprehensively quantify the changes in seismic activity after the 2011 Tohoku earthquake. We developed an automatic hypocenter determination method using machine learning and detected earthquakes that were three times larger than those in the conventional earthquake catalog from March 2011 to February 2012. We then merged the automatically determined catalog and the JMA unified catalog and extracted the inland seismic activity throughout Japan from the obtained merged catalog. In this study, we quantified the seismic activity after the 2011 Tohoku earthquake based on the ETAS model. The obtained relative changes in seismic activity show that, on average, the background seismicity rate in April 2011 is 2-3 times higher than that before the Tohoku earthquake. The background seismicity rate gradually returned to its original level over time. We compared the background seismicity rate with the maximum shear strain rate in the surrounding area based on the one-month difference in GNSS data. We found that a positive correlation. These results should help quantify the impact of large earthquakes on inland seismic activity and lead to future risk assessments. Acknowledgements: We used the waveforms from JMA, NIED, universities, and institutions, and the JMA unified earthquake catalog. We used GEONET (F5) coordinate data from GSI. We used etas_solve from Kasahara et al. (2016) to estimate ETAS parameters, and Shen et al. (1996, 2015) to calculate strain rates.
SE13-A007
An Earthquakes Rate Model of the Sumatran Fault Considering Rupture Complexity and Its Application to Seismic Hazard Assessment
Rizki WULANDARI1#+, Chung-Han CHAN2
1Sumatera Institute of Technology, Indonesia, 2National Central University, Taiwan
The Sumatran fault zone (SFZ) is 1900 km in length in the Sumatran fore-arc. According to geological and geomorphological evidence and ruptures of historical earthquakes, SFZ consists of 40 strike-slip fault segments, however, its potential rupture behaviour and the possibility of multiple-fault ruptures remain controversial. In this study, we aim to develop a more realistic rupture model for seismic hazard assessment of the SFZ. We apply an approach, namely ‘Seismic hazard and earthquake rate in fault systems’ (also known as ‘SHERIFS’), that models fault activities in the form of complex multiple-segment rupture by considering slip rate of the segments, instrumental catalogue data and paleoseismic record. The instrumental catalogue is implemented to defined background seismicity through magnitude frequency distribution. We analyse several fault rupture hypotheses, defined as criteria based on fault geometry, distance, and location of the segments. By comparing seismic rate obtained by paleoseismic data and the partitioning rate of single-rupture and multiple-fault ruptures, we identified the better fit probability of each hypotheses. The earthquake probability for a larger magnitude in the SFZ could be higher due to elevated characteristic magnitude of the rupture in a multiple-segments scenario. The procedure of this study could be applied to other fault system with complex rupture behaviours and our outcomes in the form of magnitude-frequency distribution for seismic activity in the SFZ provide crucial parameters for subsequent probabilistic seismic hazard assessment in Sumatra.
SE13-A008
Time-dependent Seismic Hazard Analysis in Chinese Mainland Based on BPT Model
Weijin XU1#+, Jian WU2, Mengtan GAO3
1Institute of Geophysics, China Earthquake Administration, China, 2China Earthquake Disaster Prevention Center, China, 3China Earthquake Administration, China
The results of probabilistic seismic hazard analysis are important basis for seismic hazard mapping, seismic safety assessment of major engineering sites and seismic risk management, etc. Seismic temporal activity model is the main theoretical basis for probabilistic seismic hazard analysis. In this study, we calculate the time-dependent seismic rate of the seismic sources of characteristic earthquakes in mainland China based on the Brownian Passage Time (BPT) model. By using the probabilistic earthquake hazard calculation method, we select an appropriate ground motion model to evaluate the time-dependent seismic hazard in mainland China. The results are compared with those based on Poisson model. Results show that the time dependent characteristic of earthquake has a significant impact on the result of the probability seismic hazard. Compared with the Poisson model-based seismic hazard results, the time-dependent seismic hazard results are significantly higher than those based on Poisson model in seismic source regions with relatively long elapsed time and large elapsed rate (greater than 1), with the maximum increase of more than 50%. On the contrary, the time-dependent seismic hazard results in the seismic source regions with short elapsed time are significantly reduced compared with Poisson's model, with a maximum reduction of about 50%. The coefficient of variation of earthquake recurrence interval also has significant influence on the seismic risk results, so the study on the uncertainty of earthquake recurrence interval should be strengthened. The results also show that the time-dependent seismic activity characteristics have a consistent effect on the seismic hazard results under different exceedance probabilities. The results of this study are an important supplement to the traditional time-independent (Poisson model) seismic hazard results, and have important significance for earthquake risk management, earthquake insurance and the formulation of earthquake protection and disaster reduction policies.
SE13-A019
Microtremor Analysis Using Horizontal to Vertical Spectral Ratio Method in Central Java, Indonesia
Nur RAHMI#+, Shindy ROSALIA, Zulfakriza
Bandung Institute of Technology, Indonesia
Central Java is known for its complex and active geological conditions, with a variety of geological features such as active volcanoes, tectonic plates, and fault lines. The region is located on two major tectonic plates, the Indo-Australian Plate and the Sunda Plate, which creates a high level of seismic activity and is prone to earthquakes. The existence of active volcanoes including Mount Merapi, Mount Merbabu, Mount Ungaran, Mount Slamet, and the Dieng Plateau is also evidence of the dynamic geological condition in Central Java. In addition, the Kendeng Basin, which is a continuation of the North Serayu Mountains that continues to the eastern part of Java makes the study of the geological conditions in Central Java challenging, especially for seismic hazard analysis. A microtremor analysis study is needed to complete the understanding of the subsurface structures in Central Java. In this study, the HVSR method is used to identify the dominant frequency of the site, the site-specific amplification, and Vs30 which is a key factor in determining the seismic hazard and risk. The data used in this study was data from 120 seismometers of MERAMEX network (July 2004). Our result shows that the dominant frequency values for the Central Java region range from 0.5 to 10.5 Hz with low frequency shown in the west of Jogjakarta to the north. The amplification values of this region are in the range of 0.7-13.6 with high amplification shown in the western part of Central Java, and the shear wave velocity values of 30 meters depth are found between 150-685 m/s.
SE13-A021
Probabilistic Seismic Hazard Analysis Based on Arias Intensity in Chinese Mainland
Xuejing LI1#+, Mengtan GAO2, Weijin XU3
1Institute of Geophysics, China Earthquake Administration, China, 2China Earthquake Administration, China, 3Institute of Geophysics, China Earthquake Administration, China
Arias Intensity is a parameter of ground motion obtained by integrating the square of ground motion acceleration through the whole duration of a seismic record. It is an important index to describe the intensity of ground motion and plays an important role in characterizing earthquake disasters such as earthquake-induced landslides and liquefaction. We carry out probabilistic seismic hazard analysis based on Arias intensity in Chinese Mainland. In this paper, we adopt the Fifth Generation Seismic Source Model of China (FGSSMC), and two sets of Arias intensity prediction equations (Travasarou and Bray(2003), Foulser-Piggott and Stafford (2012)) to calculate the values of Arias intensity at 10% exceedance probability in 50 years in Chinese Mainland. The results show that in Chinese Mainland, the Arias intensity is greater than 0.11m/s in 60% of the area, which has a risk of earthquake-induced landslides, the Arias intensity is greater than 0.32m/s in 30% of the area, which has a high risk of earthquake-induced landslides, and the Arias intensity is greater than 0.54m/s over 15% of the area which has a very high risk of earthquake - induced landslides. The provincial capitals and most prefecture-level cities in western China are located in the regions with Arias intensity values greater than 0.32m/s. The Arias intensity around the main fault zone is above 0.54m/s. It means that western China has a high risk of earthquake-induced landslides and liquefaction. In addition, the probabilistic seismic hazard analysis based on Arias intensity takes into account the impact of large earthquakes more than the probabilistic seismic hazard analysis based on peak ground acceleration, which has important reference value for the seismic safety assessment of major construction projects. The research results of this paper are of great significance to the prediction and prevention of earthquake disasters in mainland China.
SE13-A023
Risk Assessment of People Trapped in Earthquake Disasters Based on Single Buildings: A Case Study in Xichang City, Sichuan Province, China
Benyong WEI#+, Guiwu SU, Wenhua QI
China Earthquake Administration, China
Earthquakes are the most unpredictable natural hazards. A quake occurs almost instantaneously, but the impact lasts for a long time and causes great human losses. Strengthening the study of trapped personnel distribution in an earthquake not only ensures the efficiency and orderliness of earthquake rescue but also maximizes the survival probability of trapped people and reduces casualties. Through distinguishing the use functions of buildings, this study constructed an assessment model of people trapped in a collapsed single building due to an earthquake and evaluated the risk of individuals trapped in Xichang area, China. The results showed that the risk level of people trapped in collapsed buildings in Xichang area is high. Under the influence of seismic intensity Ⅸ, the proportion of people trapped in collapsed buildings has reached approximately 1-2% of the total regional population. The risk level of trapped people in the daytime and at nighttime caused by the same earthquake scenario is significantly different. The number of potentially trapped people at night is nearly two times greater than that during the day. The low seismic performance of buildings is the most important factor causing the high risk of people trapped. The use function of buildings also has an important effect on the risk assessment of the trapped population distribution. Improving the seismic performance of buildings is the basic way to reduce the risk of regional people trapped. It is also necessary to increase the investigations and studies of the law of regional population flow, by introducing mobile big data and high-precision household census data. Building-level data could provide more practical disaster information for ESAR and decision-making, due to it can significantly distinguish the use functions of single buildings and population distribution during the daytime and nighttime.
SE13-A025
Multi-sensing Based Approach to Mapping Exposure and Seismic Vulnerability of Buildings in a Context of Rapid Socioeconomic Growth: A Case Study in Tangshan, China
Wenhua QI#+, Guiwu SU, Benyong WEI
China Earthquake Administration, China
Due to dynamic urban growth, exposure and seismic vulnerability of buildings is highly variable over short time scales, especially in areas with rapid socioeconomic development. In this regard the continuous monitoring of building-related conditions is a challenging task, particularly in large-area. Fortunately, Earth Observation (EO) and Information and Communication Technology (ICT) has provided unprecedented hope for addressing the challenging task. Synthetically using EO and ICT, we develop a remote- and social-sensing based approach to mapping exposure and seismic vulnerability of buildings in a context of rapid socioeconomic growth. This approach employs different strategies to extract vulnerability-related parameters of buildings in urban and rural part, respectively. For buildings in urban area, data of VHR imageries and passive social sensing (e.g., internet-resources/mobile signaling), and techniques of deep learning (ARC-Net) and machine learning (Random Forest) were used to derive vulnerability-related parameters at building level. These parameters include footprint/shape, number of stories, structure-type, age, and usage. For buildings in rural area, vulnerability-related parameters were extracted at village level through active social sensing (crowdsourcing). Using Geographical Citizen Science framework, citizens from pilot villages and project members co-determined the collection form to and co-designed the mobile APP to gather building-related data. The structure-type ratio, age ratio, and function ratio of buildings in whole village was obtained. Besides, this co-designed APP can be used to gather more detailed parameters of single typical building, such as construction-material, structural column setting, and soil condition. This approach is demonstrated in Tangshan, China, which was hit severely by the 1976 earthquake with Ms 7.8. The exposure and vulnerability-related parameters of buildings in 2020 were obtained. The verification showed that this approach has good accuracy and substantial labor-/time-/money-saving in covering large areas. Therefore, this multi-sensing based approach might have promising prospects in actual seismic loss risk reduction challenges.
SE13-A028
Macroseismic Map of the 21 July 2022 Keng Tung Earthquake in Eastern Myanmar and the Relationship Between the Felt Intensity and Ground Motion Data
Ei Mhone Nathar MYO1#+, Yu WANG1, Yih-Min WU1, Hsin-Hua HUANG2, Chung-Han CHAN3, Myo THANT4,5, Lin Thu AUNG6
1National Taiwan University, Taiwan, 2Academia Sinica, Taiwan, 3National Central University, Taiwan, 4University of Yangon, Myanmar, 5Myanmar Earthquake Committee, Myanmar, 6Nanyang Technological University, Singapore
In 21 July 2022, a moderate Mw 5.9 earthquake occurred ~ 30 km south east part of the Keng Tung (Kyaing Tone) Township in eastern Myanmar, close to the western end of the Wan Ha fault within the Shan Fault system. Reports from social media and local news suggests the earthquake caused building damages and landslides near the mainshock epicenter, and was felt from the southernmost Yunnan to the central Thailand area. In order to understand the mechanism of this earthquake event, and to built the regional relationship between the felt intensity and the instrumental peak ground motions, we collect felt reports and damaging photos from the social media and digital news to conduct the macroseismic investigation of this earthquake events. Meanwhile, we also use data from the regional seismic network to relocate Keng Tung earthquake sequence to determine the source of this earthquake sequence. After the Double Difference Relocation analysis, we found the relocated Keng Tung earthquake sequence delineate the NE-SW trending Wan Ha Fault trace, with focal depth between 20 to 35 km. This suggests the main trace of the Wan Ha fault is indeed the source of the Keng Tung earthquake. As for the macroseismic investigation, we interpret more than 75 felt reports from the mainshock and compare these felt accounts to the instrumental data. Our analysis suggests the felt intensity fits the PGV data better than the PGA in the region of Myanmar and Thailand, and the building damages near epicenter is likely caused by the combination of poor construction quality and site conditions. We hope these results will help us to establish a better model to describe the earthquake damage and ground motion in the central part of mainland SE Asia in the future.
SE13-A029
Accelerograph Records of Ground Motion in Metro Manila During Two Earthquake Events
Hannah PEÑA1#+, Alfredo Mahar LAGMAY2
1University of the Philippines Resilience Institute, Philippines, 2University of the Philippines Diliman, Philippines
A number of studies explored and quantified the effect of factors that either attenuate or amplify ground motion during an earthquake. Among the earliest predictors of site response include earthquake magnitude and proximity of a site from the earthquake source. In this study, we look at two earthquake events wherein ground shaking was instrumentally recorded in Metro Manila – the 2019 Mwp6.1 Central Luzon earthquake and the 2022 Mw7.0 Northwest Luzon earthquake which ruptured approximately 85 km and 340 km away from Metro Manila, respectively. Values of ground motion are derived from accelerograph data recorded in various measurement sites in the study area. Furthermore, this study explores the relationship of ground motion and subsurface characteristics by using borehole data taken from different locations within the region. In preparation for the next rupture event along the ~100km-long West Valley Fault which runs through Metro Manila, this study aims to contribute new insights to the study of seismic hazards which can help mitigate the effects of the next big earthquake, possibly a >M7 event, in this area which is among the most densely-populated regions in the world.
SE14-A004
Upper Mantle Anisotropy in North China Craton from SKS Splitting
Zhengyang QIANG1#+, Qingju WU2, Yonghua LI2
1Institute of Geophysics , China Earthquake Administration, China, 2China Earthquake Administration, China
The North China Craton (NCC) is one of the oldest continental nuclei in the world. Formed by the amalgamation of the eastern NCC (ENCC) and western NCC (WNCC) along the Trans-North China Orogen (TNCO) at ∼1.9 Ga, the NCC was essentially stable until the Mesozoic when the ENCC experienced significant tectonic reactivation and destruction, despite the apparent lack of internal deformation in WNCC. Being the major part of the WNCC, the Ordos Block is surrounded by Circum-Ordos Rifts. Since the Cenozoic, the Rifts were relatively active and developed strong destructive earthquakes. The Ordos block has a thick crust (40 ∼ 48 km) and lithosphere (160 ∼ 200 km), in contrast to the relatively thin crust (30 ∼ 36 km) and lithosphere (80 ∼ 140 km) beneath the TNCO, indicating lithospheric remobilization and thinning. In order to understand the lithospheric deformation and the possible mantle flow thereby, we estimate over 2,000 shear wave splitting parameters from 84 teleseismic earthquakes recorded at 465 temporary broadband stations dispersed over the western and central North China Craton. A thick Archean cratonic keel has been mapped in the interior of the Ordos Block, where W-E trending fast polarization directions with small delay times are indicative of stable terrane. While a combined effect of the APM-induced mantle fabric and a mantle flow around the southeast edges of the Ordos Block explains the dominant W-E fast orientations with relatively large delay times. The prominent rift-orthogonal fast orientations beneath rifts to the northern Ordos Block imply the existence of active mantle flow. Also, it is inferred that a mantle plume is responsible for generating the parabolic fast direction pattern beneath the Datong Volcano. This work was supported by the National Natural Science Foundation of China (Grants U1839210, 41804084)
SE14-A010
Delineation of Crustal Configuration of the Eastern Ghats Mobile Belt, Odisha, India Using Global Gravity Data and Its Relation with the Non-volcanic Geothermal Systems
Ananya P. MUKHERJEE1, Aurobindo Kumar BASANTARAY2, Animesh MANDAL1#+
1Indian Institute of Technology Kanpur, India, 2Earth Sciences, Indian Institute of Technology Kanpur, India
The Eastern Ghats Mobile belt (EGMB) has a complex tectonic evolution history but is generally considered as a stable continental region. The presence of geothermal systems scattered within the belt are in contradiction to the stable region, whose thermal sources are said to be non-volcanic in nature. Satellite derived globally gridded topography and free-air gravity data are used in this study to investigate the subsurface structures below the region covering three such non-volcanic geothermal systems, namely, Tarabalo, Atri and Taptapani hot-springs, located near the east Indian coastal region in Odisha, India. The calculated Bouguer gravity anomaly shows that the hot-springs are situated in regions showing moderate to high gravity anomalies which lie at proximity to major shear zones making up the EGMB region. The radially averaged power spectrum analysis reveals the deepest interface to be at ~20.7km. The residual Bouguer gravity anomaly obtained by removing the 20 km upward continued regional anomaly from the complete Bouguer anomaly shows the presence of some lineaments lying close to the hot-springs. Applying edge enhancement techniques delineated these lineaments and are correlated with the existing structural information available for the study region. Parker-Oldenburg iterative inversion algorithm is utilized to obtain the Moho structure prevalent below the study area, with depths to the Moho surface ranging from 28 to 38 km. The shallowest Moho is observed around the Mahanadi rift basin region, where the Tarabalo and Atri hot-springs are located and the Taptapani hot-spring region shows a Moho depth of ~34 km. The obtained results from the global gravity data indicates that the moderately shallow Moho structure owing to the crustal reworking and the major lineaments resulting due to past supercontinent reconstructions involving the EGMB, play a significant role in aiding the formation of the heat source and evolution of these non-volcanic hot-springs.
SE15-A008
A Method for Predicting Shallow Landslide Induced by Climate Change in Permafrost Areas
Yu LUO#+
Institute of Mountain Hazards and Environment, Chines Academy of Sciences, China
Landslide is one of the most serious geological hazard in mountainous regions around the world. It is well known that landslide is associated with many environment factors, such as rainfall, earthquake, human activities, and so on. In recent years, with the globe temperature growing, there are more and more landslides occur in permafrost areas. Researchers found that climate change is the main environment factor lead to landslide in permafrost areas. Therefore, this study considers the effect of temperature change on active layer in permafrost areas, combined with the infinite slope theory, propose a new physical-based model to predicting the landslide induced by temperature change in frigid zone. That is a new method proposed here, in order to help researches to producing temperature-change-induced landslide hazards maps in permafrost areas, under the condition that the globe climate change result in the globe temperature growing.
SE15-A009
The Volcanic Ash Dispersion System in Meteorological Service Singapore
Zhong-Yi CHIA1#+, Chee-Kiat TEO2, Efthymia PAVLIDOU1, Boon Ning CHEW2
1Meteorological Service Singapore, Singapore, 2Centre for Climate Research Singapore, Singapore
Singapore is located near the Pacific Ring of Fire. The country’s aviation industry and air quality could be impacted by the volcanic ash, should a volcano eruption happen within the region. Therefore, Meteorological Service Singapore (MSS) monitors the regional volcano eruptions and provides volcanic ash alert to local stakeholders when there is a significant eruption. As part of the effort in volcanic ash monitoring, MSS maintains a volcanic ash dispersion modelling system that forecasts the atmospheric dispersion of the volcanic ash. The system is broadly based on a similar system operated by the UK Met Office (UKMO) for the London Volcanic Ash Advisory Centre (VAAC). It is built on the Numerical Atmospheric-dispersion Modelling Environment (NAME), an atmospheric dispersion model developed by the UKMO. This system estimates the ash plume from a set of prescribed eruption parameters – namely the location and height of the volcano, the eruption plume height, the eruption starting time and duration. The turbulent transport of the volcanic ash within the atmosphere is simulated using the meteorological data from the numerical weather forecast from the Integrated Forecasting System (IFS) maintained by European Centre for Medium-Range Weather Forecasts (ECMWF). Here, we discuss the modelling results of some eruption cases in Southeast Asia. The model uncertainties and potential areas for improvement will also be discussed.
SE15-A015
Long Term Deformation Analysis Inferred from Space Borne Geodetic Observation in NW Himalaya
Somalin NATH1#+, Rajat Subhra CHATTERJEE2, Onkar DIKSHIT1, B. NAGARAJAN1
1Indian Institute of Technology Kanpur, India, 2Indian Institute of Remote Sensing, India
The complex tectonic settings of NW Himalaya have drawn considerable attention from various researchers because of the vulnerability of seismic hazards at different scales. DInSAR offers the typical advantages of the remote sensing techniques. However, it is important to underline that high quality results can only be achieved by employing an adequate InSAR processing (image registration, filtering, phase unwrapping, etc.), coupled with an appropriate statistical treatment of the DInSAR observations. For strain accumulation analysis, we used L band ALOS PALSAR 1 & 2 image pairs with long temporal baselines and large areas of coverage for investigating deformation over NW Himalaya. The data sets were further spatial-temporally analyzed with phase and atmospheric correction. The corrected phase profile with major tectonic structures show the possible areas of strain accumulation with comparatively consistent high phase value over the years. The DInSAR phase profiles using ALOS 1 and 2 data show a maximum value show a maximum phase over the area in and around MCT depicts a major strain accumulation zone around MCT with a LOS displacement of ~2 cm per year. High phase value around MCT suggests the possible area of strain accumulation with considerable number of seismic events with a deformation up to ~100 kms up to HFT. This high phase value near MCT shows no correlation with surface elevation, indicating that the effect of tropospheric delay has been correctly compensated.
SE15-A019
Hazard Assessment of Volcanic Debris Avalanches at the Northwest Flank of Merapi Volcano
Sulistiyani SULISTIYANI1#+, Dary Putra Utama ASMARAKUSUMA1, Raditya PUTRA1, Dwi JAYANTO1, Yulianto YULIANTO1, Agus Budi SANTOSO1, Christina WIDIWIJAYANTI2
1Geological Agency, Indonesia, 2Nanyang Technological University, Singapore
Merapi Volcano entered a new effusive eruption episode on January 4, 2021, manifested by lava dome growth-producing rock falls, pyroclastic density currents (PDC), and lahars. For the first time in history, Merapi has two lava domes in one eruption period that grew simultaneously at the southwest side of the outer crater wall and in the (center) crater. The precursory signs are indicated by the gradual increase in seismicity and deformation (slope-distance of the summit Electronic Distance Measurements (EDM) reflector (RB1) measured from the Babadan Observatory) observed from June to September 2020. Towards the eruption onset, a sectorized shortening that was only observed at this West-Northwest flank’ EDM was accelerated concurrently with the heightened seismicity, which revealed a non-concentric deformation field over the Merapi edifice. The total slope distance shortening until February 13, 2023, was 15.5m, confirmed by measurement at the second reflector (RB2) located 150m below RB1 (2,645m elevation). This posed a new concern on possible flank instability that could initiate sector collapse of the northwest sector of Merapi, which was represented by the 1888 lava block. As part of the hazard mitigation effort, we performed the assessment of different scenarios, e.g., debris avalanche, PDC, and rockfall, with the granular flow simulation model using Titan2D software. Our objective is to delineate areas potentially impacted by such hazards, with a possible range of scenarios reflecting different initial source conditions, source volume, and flow mobility. In addition to the existing volcano hazard map created post-2010 eruption, it is essential to perform short-term hazard evaluation to anticipate the evolving hazards during the ongoing eruption of Merapi, which is useful for contingency planning.
SE15-A021
A Rugged, Portable and Intelligent Analogue Seismometer for Future and Pre-existing Arrays – Güralp Certis
Ella PRICE#, Neil WATKISS+, James LINDSEY, Phil HILL
Guralp Systems Ltd, United Kingdom
Seismic networks often face logistical and financial challenges that require portability, longevity and interoperability with existing equipment.
Güralp have combined proven ocean bottom, borehole and digitiser technology to produce an analogue seismometer with intelligence that benefits networks of all sizes. The Güralp Certis is a broadband analogue instrument that incorporates specific aspects of its sister digital instrument (Certimus) while still remaining compatible with third-party digitisers.
Each Certis stores its own serial number, calibration and response parameters internally and will automatically communicate these to a connected Minimus digitiser. This allows seismometer-digitiser pairings to be changed without manual entry of new parameters. If using GDI-link streaming protocol with the Minimus, these metadata parameters are transmitted within (and therefore inseparable from) the datastream itself. Therefore, this small piece of intelligence in the analogue sensor removes the need for any manual re-entry of response parameters anywhere along the sensor-digitiser-client chain.
Certis enables users to install in locations with poor horizontal stability (e.g., glaciers, dynamic landslide scarps, water-saturated soils), without the need for cement bases or precise levelling, as the sensor can be deployed at any angle regardless of which model digitiser is connected. Due to its small size, low weight and ultra-low power consumption, Certis significantly reduces logistical efforts and makes short term temporary deployments far easier.
Certis addresses many challenges of traditional seismometer deployments, including cost, but provides a flexible and simple solution for seismic monitoring applications across all disciplines.
SE15-A027
Seismic Velocity Changes Associated with the 2020-2022 Activity of Semeru Volcano as Inferred from Auto-correlations of Ambient Seismic Noise
Yasa SUPARMAN1#+, Ahmad BASUKI1, Heruningtyas Desi PURNAMASARI1, Oktory PRAMBADA1, Devy Kamil SYAHBANA1, Hendra GUNAWAN1, Francois BEAUDUCEL2
1Center for Volcanology and Geological Hazard Mitigation, Indonesia, 2Institut de Physique du Globe de Paris, France
Semeru has been the most active volcano in Java manifested by periods of intermittent explosion and lava effusion occurred at the summit crater. The ongoing eruption that started since April 2014 producing various phenomena e.g. explosions, ash plumes, lava flows, pyroclastic flows, lahars, and dome collapse. The 4 December 2021 eruption was the first monitored explosive eruption of Semeru that produced partial column collapse PDC, which characterised by a more energetic PDC compared to the usual gravitational pyroclastic cone collapse event. This explosive eruption produced 16 km PDC runout and syn-eruptive lahars that destroyed settlements area and public infrastructures along the Besuk Kobokan river channel at the southeastern flank. Here we analyze the autocorrelation of seismic ambient noise at Semeru volcano, observed between September 2020 to December 2022 using the vertical component data of short period seismometer located at the flanks of Semeru Volcano. The Moving-Window Cross-Spectral (MWCS) method was employed to measure seismic velocity variation in the 0.5 – 1 Hz frequency band. This study indicated changes in seismic velocity preceded 2 large PDC events of Semeru, observed concurrently with baseline changes between GPS stations: 1) Decreased in seismic velocity observed from early October to mid November 2020, which proceeded the 1st December 2020 PDC event. 2) continuous decreased in relative velocity variation since June until December 2021, proceeded the 4th December 2021 event. We suggest that seismic velocity changes might reflect the stress changes induced by over pressurization of the magma reservoir due to new magma recharge.
SE16-A003
Summary of Oct. 8, 2022 Earthquake Swarm in the Tatun Volcano Group, Northern Taiwan
Ya-Chuan LAI1,2#+, Min-Hung SHIH3, Cheng-Horng LIN4, Hsiao-Fen LEE5,6
1Taiwan Volcano Observatory - Tatun, Taiwan, 2National Center for Research on Earthquake Engineering, Taiwan, 3National Applied Research Laboratories, Taiwan, 4Academia Sinica, Taiwan, 5National Center for Research on Earthquake Engineering, National Applied Research Laboratories, Taiwan, 6Taiwan Volcano Observatory at Tatun, Taiwan
The Tatun Volcano Group (TVG) locates in the north part of Taiwan, only 15 km away from the Taipei metropolitan area, may induce strong impact if it active again in the future. The seismicity is one of most important indices of volcano activity, hence a broadband seismic network was installed in the TVG. A series of earthquake swarm with largest magnitude 3.1 occurred in the TVG during Oct. 7 to 9, 2022. An unexpected number of micro-events were detected by the dense seismic array in the Tatun volcanic area. More than a thousand of events occurred, almost equal to the half of the annual average of the background seismicity of the TVG. Such sequences with a lot amount micro-earthquakes only happened twice before in the past decade. One is the 2014 ML 4.2 Shilin earthquake, the biggest one occurred in the TVG recently. The sequence of earthquakes was majorly located in the northern of Mt. Dajianhou, where is the area with obvious variation of seismicity. Most of the earthquakes were clustered in the Mt. Dajianhou and its northern flank with their focal depths less than 5 km. The major felt earthquakes were located at depths around 3-4 km within a significant dip plane composed of the accompanied micro-earthquakes. Such pattern of hypocenter distribution may be related to the local hydrothermal activity process. The importance of hydrothermal system was also demonstrated by the focal mechanisms of major felt earthquakes. The determination of first P-wave motion was predominantly non-double-couple. It’s notable that the geochemical anomalies may be linked to this sequence of swarm.
SE16-A004
Lidar Observations of Eruptive Products of Sakurajima Volcano, Japan
Haruhisa NAKAMICHI#+
Kyoto University, Japan
Two lidar instruments were installed at Sakurajima volcano, Japan at the end of November 2014. These Sakurajima lidar instruments were the first to specifically observe the eruptive products of this volcano in Japan. Sakurajima volcano is one of the most active volcanoes in the world and is in the best location for observing eruptive products. Volcanic ash is the most fine-grain of eruptive products with the particles size of atmospheric aerosols. The lidar instruments can observe such fine volcanic ash. Small eruptions, unreported by the Japan Meteorological Agency, can be detected by the lidar instruments set up at Sakurajima volcano. The small eruptions detected by the lidar instrument were also confirmed by extension meters and seismometers at an underground tunnel in Sakurajima. Large volcanic eruptions are a concern in Sakurajima Island, during which prevailing westerly winds could disperse volcanic ash to the Japanese Islands. Therefore, this ash is expected to be observed using lidar instruments in the Japanese Islands.
SE16-A005
Hazard Assessment and Modeling of Lava Flow Hazard on Tatun Volcano Group, Northern Taiwan
Huai-Yu TANG1+, Sheng-Rong SONG1, Yu-Ming LAI2#
1National Taiwan University, Taiwan, 2National Taiwan Normal University, Taiwan
Lava flows, one of the hazards of volcanoes, can extend tens of kilometers from an erupting vent, destroying everything in their path. To better understand volcanic hazard of lava flow and prepare for emergencies at active volcanoes, lava flow simulations can be useful. The Tatun Volcano Group (TVG) is a Quaternary dominantly andesitic active volcano located near the capital of Taiwan, Taipei City. Two nuclear power plants and a city with a large population (about seven million people live in the vicinity) are located only a few kilometers away from the TVG, any volcanic hazards would be catastrophic for life and cause huge economic losses. In this study, we focus on the lava flows of the TVG and provide two main highlights of our work: (1) Measurements of the length and volume of past lava flow eruptive events as a reference for assessing the eruptive characteristics and physical properties of lava flows in the TVG. (2) To predict the likely extent of future lava flow eruptions by simulating several potential eruptive craters or sites(ex: Mt. Qixing, Mt. Huangzui, Mt. Shamao…etc) within the TVG using the Q-lavHA simulation software. Provide quantitative scientific data for volcanic hazards assessment and emergency preparedness planning.
SE16-A007
Dive Into Volcano Earthquake Swarm Beneath Active Fumarole Area in the Tatun Volcano Group, Northern Taiwan
Min-Hung SHIH1#+, Ya-Chuan LAI2,3, Cheng-Horng LIN4, Hsiao-Fen LEE5,6, Hsin-Chieh PU7
1National Applied Research Laboratories, Taiwan, 2Taiwan Volcano Observatory - Tatun, Taiwan, 3National Center for Research on Earthquake Engineering, Taiwan, 4Academia Sinica, Taiwan, 5National Center for Research on Earthquake Engineering, National Applied Research Laboratories, Taiwan, 6Taiwan Volcano Observatory at Tatun, Taiwan, 7Central Weather Bureau, Taiwan
Qixingshan (aka Qixing Mountain) is the highest volcanic peak in the Tatun Volcano Group in northern Taiwan. In this mountain area, a series of active fumaroles, hot springs, and ancient phreatic eruptions can be found on the surface. Meanwhile, a lot of microseismic events were detected underground. Due to the Qixingshan neighboring the Taipei Metropolitan Area, the monitoring of volcanic activity is an essential topic for local governments and research institutes. To looking more details of the velocity structure in Qixingshan area, we had been deployed a dense seismic array around the mountain, which consists of 60 FairfieldNodal ZLand 3C nodes with a station spacing of 100-200 meters. On April 25, 2022, there was an earthquake swarm occurred in this area, which followed by ~60 smaller earthquakes determined by the real-time broadband seismic network. This sequence is also well recorded by this highly dense array. In this study, we will process the Zland data for the period of this earthquake sequence to detect more micro signals. More details will be discussed in the future.
SE16-A008
A Preliminary Rock Magnetic Results of the Kusatsu-Shirane Volcano, Japan
Nagisa SAWADA1#+, Nobuko KAMETANI2, Kazuo KAWASAKI1, Yasuo ISHIZAKI1, Akihiko TERADA3
1University of Toyama, Japan, 2Yamanashi Prefectural Government, Japan, 3Tokyo Institute of Technology, Japan
The active Kusatsu-Shirane volcano in Gunma, Japan is composed of three pyroclastic cones and has repeatedly produced small phreatic eruptions (JMA, 2013). This study was a test to see if magnetic analyses could estimate the eruption styles and contrast unit boundaries between two outcrops, and thereby, to show that detailed magnetic characterization are useful for active volcanoes that repeatedly erupt on a small scale. The samples used for analyses were 54 and 35 levels of Holocene sediments collected from two natural outcrops, a "hairpin" turn along Route 292 and Sessyogawara geothermal area, respectively. Samples were dried at room temperature for at least 72 hours after collection. Based on the results of room temperature, high and low temperature magnetic analyses, the main magnetic mineral of the sediments is pseudo-single domain titanomagnetite. Further, the high-temperature magnetic analyses showed one or two Curie temperature, suggesting two different Ti content in the titanomagnetites. The results of low-temperature magnetic analyses showed that the magnetite and maghemite are almost negligible. Thus, the observed different magnetic characteristics of the samples are found to be largely effects of their Ti content. The heating curves of temperature dependence of magnetic susceptibility (k-T) is different the ones of strong-direct field thermomagnetic curves and the k-T heating behavior are divided into two obvious trends. These trends could be caused by the different mineralogy such as sulfides and/or iron-oxides and may help to characterize the eruption styles. In addition, the observed different trends of k-T curves appear alternately and repeatedly at both outcrops, suggesting the possibility of contrasting unit boundaries. Therefore, magnetic characterization of sediments by detailed rock magnetism can be an effective method to contrast the outcrops surrounding an active volcano.
SE16-A015
Direct Observation of Dynamic Stress Waves from Turkey Earthquakes of Feb. 2023, Which May Trigger the Japanese Volcanoes Eruption
Yongqian CHEN1,2+, Fuzhen LI1, Tianxiang REN3, Huai ZHANG1, Yaolin SHI1#
1University of Chinese Academy of Sciences, China, 2Shanxi Earthquake Agency, China, 3Chinese Academy of Geological Sciences, China
Two days after the two Ms7.8 earthquakes occurred on February 6, 2023, at 9:17:37 AM and 18:24:50 PM (UTC+8) in Turkey, At around 10:00 AM (UTC+8) on February 8, two successive eruptions occurred at Sakurajima Showa caldera in Japan, which was the first eruption after nearly five years since 2018. Dynamic triggering of volcanic eruptions by great earthquakes has been suggested. However, the lack of direct observations of the dynamic stress waves makes the research on triggering full of uncertainty. For the Turkey earthquakes, we have two(Yingxian and Yuyu) four-component borehole strainmeters right located on the great arc between the Turkish earthquake epicenter and the Sakurajima volcano. The distance of the Japanese volcano from the epicenter in Turkey is 73.84°. Although we have no direct stress record at the volcano, there is a directly observed stress record at the epicenter distance of 56.88° on the great circle, which is only 16.96° away from the volcano, it is helpful to interpret the stress record of the station to understand the dynamic stress condition at the volcano. In this work, different seismic phases such as P-wave, S-wave, and surface waves are identified, their characteristics are analyzed by the stress petal method, the dynamic stress changes caused by each of them are calculated, the largest stress fluctuation occurred when the surface wave arrived, with oscillation period of about the 20s, an amplitude of up to 14kPa. The triggering mechanisms of remote earthquakes on volcanic eruptions are discussed based on the results. The ideas and methods of this work provide useful insight into research on the possible triggering effects of remote earthquakes on volcanoes.
SE17-A003
Subsurface Imaging of Short-offset Field Seismic Data Using Time- and Depth-processing
Woohyun SON#+, Byoung-Yeop KIM, Dong-Geun YOO, Gwangsoo LEE
Korea Institute of Geoscience and Mineral Resources, Korea, South
In general, seismic processing results depend on the velocity structure. So, a reasonable initial velocity should be used as input data to image accurate subsurface structures in the depth domain. To generate a reasonable initial velocity, various processing techniques were applied in the time domain. For example, to remove noise, data processing techniques such as frequency filter, trace editing, and swell noise attenuation were applied. In addition, various demultiple techniques such as deconvolution, surface-related multiple elimination, and Radon filter were applied to attenuate water-bottom (WB) multiples. By applying these processing techniques, the first and second WB multiples with strong amplitudes were greatly attenuated. A reasonable velocity in the time domain was derived by performing velocity analysis on the data after signal processing with noise and WB multiples attenuated. Then, the tomography-based MVA (migration velocity analysis) method was applied to accurately image the subsurface structures in the depth domain. Depth-processing using MVA is performed as follows. First, the initial velocity for depth processing is derived by converting the velocity generated by time processing into the depth domain. Then, the data after time-processing are sorted into common offset data. We perform Kirchhoff pre-stack depth migration using common offset data. We sort the migrated data into CRP (common reflection point) gather and perform RMO correction. Finally, we update the depth-domain velocity. After the application of MVA, the reflection events are aligned flatter. Through this result, we could confirm that the updated depth-domain velocity is reasonable. Therefore, by applying various time- and depth-processing methods to short-offset (250 m) field data, we could generate reasonable velocity structures. From the final migrated section in the depth domain, we could also confirm that the processing techniques proposed in this study improve the connectivity of the strata.
SE17-A007
Depth Dependency in High-frequency Source Radiation Energy of Small Earthquakes in Japan Estimated from Full Seismogram Envelopes
Masashi OGISO#+
Japan Meteorological Agency, Japan
Structural heterogeneities have been believed to affect little the amplitude of seismic coda waves, especially late coda waves. The Coda normalization method is based on such an assumption and is widely used to estimate site amplification factors and/or source spectra. On the other hand, recent progress in the theory of seismic wave scattering has shown that the excitation of coda waves depends on hypocentral depth, and analyses of coda waves recorded by dense seismic networks have revealed heterogeneous excitation of coda waves, which leads to the violation of the assumption of coda normalization method. Hence, we propose a method to estimate source radiation energy from seismogram envelopes considering heterogeneous seismic structures. In the proposed method, we calculate synthetic envelopes using the Monte Carlo simulation based on the radiative transfer theory and the Born scattering coefficients with a 3-D velocity structure. We conduct a grid search to find appropriate parameters of intrinsic and scattering attenuation that reproduce the shape of each observed envelope, then we calculate source and site amplification terms by an envelope fitting method. We applied the proposed method to small to moderate earthquakes that occurred around central Japan. The range of magnitude was 3.0 to 4.5, and the depth was down to 100 km. Because of the limitation of the Born approximation, we calculated source radiation energy at the frequency ranges of 1-2 and 2-4 Hz. The estimated source radiation energy correlated with magnitude in both frequency ranges. In addition, we found that deeper earthquakes tended to have larger energy than shallower earthquakes. This result may reflect the depth dependency of the physical properties of the earth. Acknowledgments: We used the seismic records of the Hi-net (doi: 10.17598/NIED.0003). This work was partly supported by the JSPS KAKENHI Grant Nos. JP18K13622 and JP21K14002.
SE17-A009
Understanding the Infantile-to-mature Subduction in Southwest Japan Via Self-consistent Formation of a Weak Slab Interface
Changyeol LEE1#+, Young-Hee KIM2
1Yonsei University, Korea, South, 2Seoul National University, Korea, South
The weak slab interface controls the long-term subduction dynamics. In particular, a weak hydrous layer at the slab interface promotes slab-mantle decoupling and converts a hot forearc mantle to a cold mantle, often referred to as a cold nose, which plays a key role in the transition from infantile to mature subduction. This study was first to numerically demonstrate the self-consistent formation of a weak hydrous layer with permeability anisotropy, based on the case of the Southwest Japan subduction zone, where the transition-related geological features were present. Our models showed that mechanical decoupling by spontaneous downdip growth of the weak hydrous layer created a cold nose by converting a hot forearc mantle to a cold mantle. This result explained (1) the migration of the forearc-to-arc volcanic front, expressed as the formation of mid-Miocene forearc high-magnesium andesite and Quaternary arc adakite, and (2) present-day geophysical and geochemical observations in the forearc.
SE17-A011
Discrimination of Explosions and Earthquakes Using Amplitude Ratio of Body-wave
Mikyung CHOI#+, Jayoung YANG, Kyungmin MIN, Jimin LEE, Sun-Cheon PARK
Korea Meteorological Administration, Korea, South
The Korean Meteorological Administration uses various methods to distinguish between earthquakes and explosions. The methods of discriminating explosions from earthquakes are ratio of regional P/S amplitudes and infrasound analysis. We are also trying to develop a method to separate seismic events associated with the collapse of underground cavities from explosions and earthquakes. Recent analysis such as amplitude ratios of body-waves shows separation between three different types of events (Walter et al., 2018).
In this study, we review the method for distinguishing between explosions, collapses and earthquakes using the amplitude ratio of body-wave suggested by Walter et al. (2018). The amplitude ratios of body-waves (Pn, Lg) according to frequency bands are analyzed and compared using the data from regional seismic station on regional earthquakes, the 1st to 6th explosions by the Democratic People’s Republic of Korea (DPRK) and collapse that occurred after the 6th explosion. In addition, the same method is applied to mining collapse in South Korea to distinguish between collapses and earthquakes.
SE17-A014
The Relationship Between Seismic Swarm and Fluid Migration Beneath the Western Foothills of Taiwan
Chia-Nan LAI+, Strong WEN#
National Chung Cheng University, Taiwan
Taiwan is located at the junction of the collision of the Eurasian plate and the Philippine Sea plate, and in the western foothills at the front of the orogenic belt, this provides a good environment for the occurrence of seismic swarms. Swarms tend to occur in areas with high subsurface heterogeneity and fractured structures, and these will triggered by stress variation, high fluid pressure, or aseismic slip. For example, two seismic swarms occurred in Zhushan area in Nov. 2017, which is in the deformation front of orogenic belt. From the analysis, we observed that the velocity structure in this area exhibited significant variation before and after the seismic swarms, and we found that the stress field rotated horizontally at different time period as well. The results we obtained in temporal and spatial distribution are highly consistent with the “seismic clouds” caused by hydraulic fracturing. Hydraulic fracturing is the technique of injecting high-pressure fluids into subsurface rock formations, which can propagate along existing fractures or create new cracks, and these processes can generate many small earthquakes. Since there was no stress disturbance provided by moderate earthquakes during the time period when the seismic swarms occurred, and there was no known aseismic slip zone in this area, through the analysis of this study, it is believed that the seismic swarm that occurred in the western foothills is associated with the fracture zone and related to fluid migration. Since the western coastal plain and the western foothill belt in Taiwan were passive continental rift margins before orogeny, and developed a series of normal faults, most of these fault systems have re-active at the deformation front due to orogeny process. Therefore, using the results obtained in this study, the mechanism of the seismogenic activity in the western foothills of Taiwan can be clarified.
SE17-A020
Tortoises or Hares – Characterizing the Turbidity Currents Observed in the Manila Trench, South China Sea
Meng LIU1+, Zhiwen WANG2, Kaiqi YU1, Jingping XU1#
1Southern University of Science and Technology, China, 2National Marine Environmental Monitoring Center, China
Sediment gravity flows are the most direct and efficient transport mechanisms for moving terrestrial sediments into deep oceans. Scarcity of firsthand measurements, however, has hindered the quantitative, even qualitative characterization of such flows. Here we present a unique year-long data record from ~4000 m depth in the Manila Trench that captured two very different gravity flows in terms of their hydraulic and sedimentary properties. The first flow was of slow speed (~40 cm s-1) and long duration (~150 hours), thus nicknamed ‘Tortoises’, and carried very fine sediment with low concentration (~0.01%). The fast (~150 cm s-1) but short-lived (~40 hours) flow, nicknamed ‘Hares’, carried much coarser sediment with higher concentration (~1.2%). Notably, tidal current in the deep trench modulated the ‘Tortoises’ flow and had likely prolonged its lifespan. Clay mineral compositions suggested that the ‘Tortoises’ originated from upstream canyon wall slumping, whereas the ‘Hares’ was likely submarine canyons Southwest of Taiwan Island due to typhoon. Grain size is a key factor in determining whether a turbidity current evolves into ‘Tortoises’ or ‘Hares’. Finally, the sediment load by turbidity currents accounts for about 17.8% of the yearly average sediment flux of the Gaoping River.
SE17-A029
Forearc Structures in the Manila Subduction Zone and Its Effects on Gas Hydrate BSR Distribution
Elisha Jane MAGLALANG#+, Karla May SAYEN, Leo ARMADA, Carla DIMALANTA
University of the Philippines Diliman, Philippines
Along-strike variations in the forearc character of the Manila Trench control the distribution of gas hydrate BSRs in the area. To the north, BSRs are concentrated in two regions – within the accretionary prism with depths ranging from 285 m to 526 m below the seafloor, and in the western portions of the North Luzon Trough, at depths of 714 m to 812 m. To the south, the BSRs occur within the basin fill of the West Luzon Trough, with an average depth of ~720 m. In the northern segment of the forearc, the accretion of the continent derived sedimentary cover of the subducting crust provides hydrocarbon sources and promotes the formation of thrust faults and gas chimneys, resulting to pervasive fluid migration and forming widespread BSRs within the accretionary prism. In the North Luzon Trough, the sedimentary fill is mostly composed of arc derived turbiditic sequences and mass transport deposits (MTDs) sourced from the collapse of the frontal wedge, possibly due to the oversteepening of slopes or gas hydrate dissociation. Fluid migration along the landward tilted sedimentary sequences of the North Luzon Trough further contributes hydrocarbon-rich fluids needed for gas hydrate formation in the accretionary prism and western parts of the basin. Along the southern segment of the forearc, the incoming South China Sea crust is characterized by a thinner sedimentary cover and bathymetric highs, forming an erosive margin that prevents the accumulation of gas hydrates within the accretionary prism. The BSRs are mainly found within the West Luzon Trough. Fluid migration is facilitated by the normal faults cutting through the basin sediments. Disequilibrium conditions caused by the uplift of the Stewart Bank and by seamount subduction led to the formation of double BSRs in the northern parts of the West Luzon Trough, which reflect changes in gas hydrate stability.
SE17-A030
Forearc Heterogeneity Along Manila Trench Forearc Region: Seamount Subduction or Differential Erosion?
Karla May SAYEN#+, Elisha Jane MAGLALANG, Leo ARMADA, Carla DIMALANTA
University of the Philippines Diliman, Philippines
The complex forearc morphology in offshore western Luzon is attributed to the subduction of the heterogeneous South China Sea basin along the Manila Trench. The Vigan High is one of several bathymetric features in the Manila Trench region. This bathymetric high is a flat-topped feature bounded by submarine canyons. Previous models proposed that it was associated with the forearc uplift due to accreted fragments of the Scarborough Seamount Chain (SSC) (South China Sea extinct spreading ridge) subducted at 16ºN latitude. This preliminary study attempted to map the bathymetric high using new seismic reflection data to understand its geologic characteristics. The seismic reflection data were gathered from the recently concluded LGD-2201 marine scientific cruise and the ORV-041 cruise. Analysis of the seismic reflection profiles indicates faults and fractures bounding the Vigan High. NW-SE trending major faults were identified in the seismic profiles, bounding the Vigan High to the north and south, corresponding to the submarine canyons. The delineated major faults are interpreted as offshore strands of the Philippine Fault Zone (PFZ). Available gravity and magnetic data were also used in this study to complement the seismic reflection data. A combination of the first and second-order horizontal and vertical derivatives indicate NW-SE trending major faults bounding the bathymetric high. The derivative maps support the idea that these faults may correspond to the offshore extension of the PFZ. The gravity and magnetic data show that high gravity and magnetic signature patches characterize the Vigan, and this might suggest that the Vigan High is unrelated to a subducted seamount. Instead, we propose that the present configuration of this bathymetric high is affected by differential erosion across the offshore faults, resulting in the submarine canyons bounding the Vigan High.
SE19-A010
Rupture Model of the 2017 Mw 5.5 Pohang Earthquake, South Korea
Eunbyeol CHO1+, Jeong-Ung WOO2, Junkee RHIE1#, Tae-Seob KANG3, So-Young BAAG1
1Seoul National University, Korea, South, 2Stanford University, United States, 3Pukyong National University, Korea, South
On November 15, 2017, about two months after the last fluid injection was conducted at the enhanced geothermal system development site in Pohang, South Korea, a MW 5.5 earthquake occurred at a distance of about 600 m from the site. It was concluded that the Pohang earthquake was a “runaway earthquake” triggered by the hydraulic stimulation on the critical-state fault. To estimate the spatiotemporal slip history and analyze the characteristics of the rupture process of the Pohang earthquake, which is an uncommon type of earthquake, the finite fault inversion was performed using an empirical Green’s function method. The rupture process can be identified as three phases: first, slip initiated and propagated only to the southwest from the hypocenter during the initial 0.6 s; after then, in the second phase until 2.4 s, the slip propagated to the both southwest and northeast; at last, in the third phase until 6.0 s, slip is diffused around the edge of the fault plane, especially in the deep northeast. The seismic moment was released in each phase as approximately 6%, 59%, and 35%, respectively. The first phase can be interpreted as a separate foreshock, but it is difficult to determine quantitatively whether it is a foreshock. Overall, most of the slip distributed to the southwest well agrees with the rupture directivity result of the apparent source time function analysis. Despite the average stress drop (~1 MPa) of the Pohang earthquake rather lower than that (~20 MPa) of the MW 5.5 Gyeongju earthquake which naturally occurred in a nearby area, it is difficult to conclude that the cause is only the fluid injection. These results improve our comprehension of the source process of the Pohang earthquake and the rupture model can be helpful to understand the complex source process of the triggered earthquake.
SE19-A014
A Preliminary Attempt to Study the Assimilation Analysis of Earthquake Precursor Data Using EMD-LSTM Method
Yibo TIAN1+, Fuqiong HUANG2,1#, Baiyang CHEN1
1Institute of Disaster Prevention, China, 2China Earthquake Administration, China
Assimilation analysis of various observation data is the first step for the development of numerical seismic prediction. EMD-LSTM neural network is an effective method for predicting time series data developed in recent years. The empirical modal decomposition method is used to decompose the original time series data to obtain the IMFs(Intrinsic Mode Functions) signals, and the EMD-LSTM neural network is used to predict the decomposed individual IMF signals, and the final results can be obtained by superimposing the prediction results of each component. EMD-LSTM as a precursor data processing method, a section of actual monitored gravity data is selected for decomposition and prediction, and the relative error between its prediction results and the actual measurement results is The relative error is 0.091%, and in the inverse normalized data, the mean square error is 17976.796, the root mean square error is 134.077, the mean absolute error is 90.871, and the relative error level is 0.091%. EMD-LSTM method provides a new method for predicting time series data, and solves the non-smooth and non-linear prediction problems. The next step is to analyze different types of precursor data in combination with the dilation diffusion model with physical constraints proposed by Scholz, and observe whether the variation of the data in the frequency domain matches the development of the model.
SE19-A015
Preliminary Results of Investigation North-south Trending Blind Fault Associated with November 21, 2022 Cianjur Earthquake from Relocated Mainshock-aftershock Analysis
Aditya RAHMAN1#, Aprilia Nur VITA1+, Retno Agung PRASETYO KAMBALI1, Asep NURACHMAN1, Rahmat Setyo YULIATMOKO1, Abraham ARIMUKO1, Ade Andika SAPUTRA1, Nova HERYANDOKO2, Supriyanto ROHADI1, Suko Prayitno ADI1, Dwikorita KARNAWATI1
1Indonesian Agency for Meteorology, Climatology and Geophysics, Indonesia, 2Institute of Technology Bandung, Indonesia
At 13:21 local time on November 21, 2022, a magnitude-5.6 inland earthquake occurred in Cianjur-West Java Indonesia region, resulting at least 602 deaths and damage to 58 thousands houses. We deployed 6 temporary seismic stations soon after the mainshock around aftershocks region. We carried out preliminary auto-detection of seismic events using Lassie and detected 770 aftershocks events in the two-weeks dataset. The preliminary detection result then located using SeiscomP and we relocated the hypocenter of the mainshock and aftershock from temporary station using Hypo-DD. Our relocated mainshock-aftershock show that the earthquake sequence ruptured on hidden and unmapped fault within Cianjur Area. The distribution of seismicity reveals a previously unknown North-South trending fault (N350E) which in this study we proposed as Cugenang Fault in the northern of known Cimandiri fault. The newly identified fault calls for further investigation for future seismic hazard assessments in the region.
SE19-A016
The Application of Optical Fiber Clinometer to Solid Tide Measure
Wentao ZHANG#+, Wenzhu HUANG, Minggan LOU
Chinese Academy of Sciences, China
Solid tide is the only geophysical phenomenon that can be calculated theoretically. Therefore, solid tides measurement would have significant application prospects in geodynamics, earthquake prediction, etc. However, the solid tide phenomenon is very weak, and high performance of the instrument is required. Previously, we had observed earthquakes and solid tides using optical fiber sensors. In this paper, an optical fiber clinometer based on fiber optic Michelson interferometer was proposed and crustal deformation was measured and analyzed. The optical fiber clinometer was a Michelson fiber interferometer with an arm length difference of 0.4 m. The clinometer received signals based on the pendulum's vertical principle. The Michelson interferometer adopted Faraday rotator mirrors was able to eliminate polarization fading. A high-precision fiber-optic general signal demodulation device with resolution better than 0.0001 rad/√Hz from 0.01 Hz to 50 Hz was used. The optical fiber clinometer was installed in the borehole. The sampling rate of the system was set to 10 Hz. After the clinometer was stabilized, the phase change has good consistency with temperature change measured by a platinum resistance temperature sensor on a long-time scale, and the correlation coefficient was 0.964. Solid tide signal was covered by temperature. But solid tide waveform was recorded when the temperature change was gentle. The recorded phase waveform was basically consistent with the theoretical solid tide. Additionally, the power spectral density (PSD) showed a peak at 0.000023 Hz, which corresponded to a main period of solid tide. Therefore, although the fiber optic clinometer was affected by temperature, it had the potential to record solid tide. We believe that if several methods such as reference temperature compensation are used, better results of solid tide can be obtained.
SE19-A017
Analysis and Statistical Validation of Global Ionospheric Perturbation Using Arima as Seismogenic Precursory Signature for Western Nepal Earthquake on 8th Nov 2022
Bijoy DUTTA#+, Javed MALIK
Indian Institute of Technology Kanpur, India
Global navigation satellite systems (GNSS) derived Total Electron Content (TEC) data are being used extensively for analyzing ionospheric perturbations to detect earthquake precursory signals. In this paper we have reported prominent evidences for pre-seismic ionospheric anomalies along with its statistical validation using ARIMA over the epicentral region for a devastating earthquake in western Nepal on 8th November 2022 (Mw 5.7) and its several aftershocks (Mw 5.4, 4.2) in and around Uttarakhand. Temporal variation of TEC of the nearest grid point to the epicentre was analyzed based on median, upper and lower bounds (defined by standard deviation) for a time span of a month prior to the quake. After ruling out all possible contributions from solar terrestrial environment, anomalous (-ve) behaviour of TEC (~12 units) is observed 3-22 days prior to the earthquake. In order to visualize the TEC anomaly in spatio-temporal domain, we have plotted 2D latitude-longitude time (LLT) maps considering the nearest plate boundary and Global Ionospheric Map (GIM). Using these we have determined the probable epicenter which showed very promising correlation in comparison to actual epicenter; the offset is found to be ~85 km and 125 km respectively. In order to validate this anomaly as seismogenic origin we have also used a statistical model ARIMA. After choosing proper ARIMA model from ACF and PACF we have forecasted the data for those anomalous days. After optimizing hyper parameters and training the model, a significant number of –ve anomalies have been observed on those anomalous days. The forecasted data gives a promising accuracy in trend with the GNSS derived data. This model has an adequate potential to forecast ionospheric TEC and to detect anomalous behaviour with considerable accuracy prior to any disastrous quake. This will provide some new beneficial insight to study seismo ionospheric coupling from new aspect.
SE19-A020
Slip Rate and Locking Status of the Xianshuihe Fault Inferred from Dense Geodetic Observations
Faqi DIAO#+, Yage ZHU, Xiong XIONG
China University of Geosciences, China
The Xianshuihe-Xiaojiang fault (XXF) that lies in the southwest of China, is one of the largest left-lateral faults surrounding the Tibetan Plateau. The northern segment of the XXF is called Xianshuihe fault, which is a well-known seismogenic fault due to the high frequency of strong earthquakes. Therefore, the present seismic risk of this fault has aroused wide concern. The slip rate and locking status of seismogenic faults are crucial for seismogenic mechanisms and regional seismic hazard assessments. Presently, elastic models have been routinely used in probing the fault slip rate and locking status with geodetic observations. However, recent studies revealed that elastic models could highly affect the fault parameter estimate, while models incorporating viscoelastic effect of substrate ductile layers can yield reliable results. Here we construct viscoelastic deformation models based on dense GPS velocities near the Xianshuihe fault to invert for the slip rate and locking status of the fault. Our results suggest that elastic models will highly overestimate the fault locking depth, and thus seismic moment accumulation rate. Besides, the block division strategy also plays an important role on resulted fault slip rate and locking distribution. Based on the inverted fault locking distribution, we identify four potential asperities along the Xianshuihe fault, which show clear spatial correlation with the historical ruptures. This result suggests that the fault locking status may control the rupture extent of strong earthquakes on this fault, which has important implications on future seismic hazard assessment. Moreover, the 2022 M 6.8 Luding earthquake was found only ruptured a part of an identified asperity, while the seismic moment accumulated on the unruptured segment is corresponding to an Mw 6.8 earthquake, highlighting that the potential seismic risk there should be carefully monitored.
SE19-A029
Rupture Press of Large Earthquake Based on Seismic Signals Recorded by Gravimeter
Hongbo TAN#+
Institute of Seismology,China Earthquake Administration, China
Gravimeters can provide 1Hz sampling data, including a large number of complete seismic wave records. Frequency spectrum analysis have been done after analyzing the data of Lushan Ms7.0 earthquake in 2013 recorded by gravimeters and seismometers in the same stations. The rupture process of Luding Ms6.8 earthquake in 2022 have been inversed and the following preliminary understanding can be obtained. 1) The relationship between P-wave travel time and epicentral distance recorded by gPhone and STS-1 are consistent well. 2) The dominant frequency spectrum of the P wave is quite similar, mainly concentrated in the range of 0.05 to 0.3 Hz. With the increase in the epicenter distance, the consistency between the two is better. The power spectrum image shows that the main energy of the seismic wave is concentrated between 0-0.5 Hz. 3) Based on the 1Hz gravity data, the rupture model of the Luding Ms6.8 earthquake in 2022 is inversed. The results show that the fault strike direction is 163° and the dip Angle is 77°. The rupture area is about 42 km along the strike direction and 6-27km in the dip. The main rupture zone is near the epicenter, with a maximum slip of 1.05m. The average slip angle of the fault is 9.8°. The seismic moment of the earthquake is 1.33×1019 N∙m, corresponding to a magnitude of Mw6.7. The picture of the source time function shows that the earthquake has two major sub-events: the first peak of moment release rate reach to 1.50×1018 N∙m/s at 5s; the second peak reach to 6.74×1017 N∙m/s. at 14s. The whole rupture time is about 22s. These results are basically consistent with the results of other seismograph inversion and can have reflected the main process of this earthquake rupture.
SE19-A031
The Significance of Seismic Signal Recorded by Gravimeter
Hongbo TAN#+
Institute of Seismology,China Earthquake Administration, China
The records of continuous gravimeters contain seismic wave signals that were conventionally removed as noise in the past for tidal processing analysis. However, with the Crustal Movement Observation Network of China, 80 digital stations have been formed, in which more than 60 sets of gPhone and GWR gravimeters can provide 1Hz sampling data, including a large number of complete seismic wave records. Whether these seismic data can become a new source for the study of the focal mechanism has been plaguing earthquake scientists. Whether it can be effectively unified is a good topic worthy to be analyzed. In this study, the frequency spectrum analysis and the rupture process inversion have been done after analyzing the data of Lushan Ms7.0 earthquake recorded by gravimeters and seismometers in the same stations, and the following preliminary understanding can be obtained. 1) The relationship between P-wave travel time and epicentral distance recorded by gPhone and STS-1 are consistent well. But the differences in amplitude are larger while the epicentral distance become smaller. 2) The waveforms of the seismic waves recorded by the two instruments are basically the same. The dominant frequency spectrum of the P wave is quite similar, mainly concentrated in the range of 0.05 to 0.3 Hz. With the increase in the epicenter distance, the consistency between the two is better. The power spectrum image shows that the main energy of the seismic wave is concentrated between 0-0.5 Hz. The gPhone gravimeter can record the main signal energy. The seismic waves recorded by the gravimeter can be used in the study of the earthquake rupture mechanism and it is an important supplement to the seismograph records.