Recognizing needs to better utilize and improve monitoring of weather and climate extremes from space, the World Meteorological Organization (WMO) established a new flagship initiative - the Space-based Weather and Climate Extremes Monitoring (SWCEM). We started the SWCEM with the demonstration project for Asia-Pacific (2018-2019), and were able to bring clear benefits of translating science of satellite remote sensing to operational services at National Meteorological and Hydrological Services (NMHSs) in Member countries of WMO Regions II and V in a very short time. Recognizing SWCEM achievements in Asia and the Pacific, the Eighteenth World Meteorological Congress (Cg-18) in 2019 adopted the SWCEM Implementation Plan, endorsed its implementation from January 2020 in the region, and requested to consider the possibility of implementing similar projects in Africa and South America.
The demonstration project was focused on monitoring drought and heavy precipitation and it was implemented in geographical domain which covers the South-East Asia region and the Western Pacific Ocean area from 40°N to 45°S; 50°E to 120°W. The Japan Aerospace Exploration Agency (JAXA) and the Climate Prediction Center, National Oceanic and Atmospheric Administration (CPC/NOAA) provide satellite data and products for the region. SWCEM precipitation products produced by JAXA are based on the Global Satellite Mapping of Precipitation (GSMaP). CPC/NOAA provides SWCEM users with a similar set of products using the Climate Prediction Center morphing technique (CMORPH) satellite precipitation estimates. SWCEM space-based observations of precipitation have been incorporated into WMO activities strengthening capacity of Members, especially Small Island Developing States and Least Developed Countries, in climate change adaptation and disaster risk reduction. Satellite precipitation estimates and derived products are a significant contribution to strengthening Multi-Hazard Early Warning Systems. Currently, we are implementing it through the Climate Risk and Early Warning Systems (CREWS) projects.

The World Meteorological Organization (WMO) has been initiated the Space-based Weather and Climate Extremes Monitoring (SWCEM) with the recognizing that there is a need to better utilize and improve the monitoring of weather and climate extremes from space. The Japan Aerospace Exploration Agency (JAXA) has participated in the project as one of meteorological or earth observation satellite operators. JAXA has been developed the Global Satellite Mapping of Precipitation (GSMaP) products with a resolution of 0.1 degrees, which is updated every hour, as part of the Global Precipitation Measurement (GPM) mission. In the SWCEM program, JAXA has provided the GSMaP Near-real-time Gauge-adjusted product with its 21-year climate normal since April 2000 to March 2021.In December 2021, the GSMaP algorithm was updated to version 8 by implementing various improvements to better estimate precipitation. In the new GSMaP retrieval algorithm using microwave radiometers, we expanded the retrieval latitude region to the poles from 60 degrees North and South. Some improvements were made in the retrieval method and newly input observation data of some sounder sensors. We also updated the database using precipitation radar in the retrieval algorithm, improve passive microwave and IR combined algorithm and gauge-adjustment method. Not only the estimation accuracy by updating the algorithm but also the data duration is important for the robustness of detecting extremes using GSMaP in the SWCEM activities. Therefore, JAXA is now reprocessing the GSMaP with the new algorithm (version 8) since January 1998. After the reprocessing, new version of the GSMaP data with 24-year climate normal will be utilized in the SWCEM program, leading to enhancement of the space-based weather and climate extremes detection.

In our study, Australian station data along with the Japan Aerospace Exploration Agency’s (JAXA) Global Satellite Mapping of Precipitation (GSMaP) and the Bureau of Meteorology’s (BOM) Australian Gridded Climate Dataset (AGCD) rainfall analysis are combined to develop an improved satellite-gauge rainfall analysis over Australia that uses the strengths of the respective data sources. We investigated a variety of correction and blending methods with the aim of identifying the optimal blended dataset. The correction methods investigated were linear corrections to totals and anomalies, in addition to quantile-to-quantile matching. The blending methods tested used weights based on the error variance to MSWEP (Multi-Source Weighted Ensemble Product), distance to the closest gauge, and the error from a triple collocation analysis to ERA5 and Soil Moisture to Rain. A trade-off between away-from- and at-station performances was found, meaning there was a complementary nature between specific correction and blending methods. The most high-performance dataset was one corrected linearly to totals and subsequently blended to AGCD using an inverse error variance technique. This dataset demonstrated improved accuracy over its previous version, largely rectifying erroneous patches of excessive rainfall. Its modular use of individual datasets leads to potential applicability in other regions of the world. This dataset possessed strong performance at stations (similar to AGCD), in addition to improving upon AGCD in gauge-sparse regions.

Soil moisture (SM) is a key agrometeorological indicator of drought intensity, severity and duration and is critical in monitoring the time-lagged impacts of drought. In Papua New Guinea and other Small Island Developing States (SIDS), there is a limited number, if any, in situ SM stations that can adequately assess soil-water availability in a near-real time context. Satellite SM datasets provide a viable alternative for SM monitoring and agrometeorological drought provision in these regions. In this study we investigate the performance of Soil Moisture Active Passive (SMAP), Soil Moisture and Ocean Salinity (SMOS), Soil Moisture Operational Products System (SMOPS) and SM from the Advanced Scatterometer (ASCAT) over Australia and key south-west Pacific SIDS. Australia is used as an initial SM testing ground given the presence of several in-situ SM monitoring stations and the Australian Bureau of Meteorology's state-of-art hydrological model – the Australian Water Resources Assessment (AWRA) landscape modelling system (AWRA-L). We further investigate SM satellite datasets in Australia and the south-west Pacific through Triple Collocation analysis that uses other SM reference datasets such as reanalysis SM data from the ERA-Interim mission and the Global Land Data Assimilation System (GLDAS) dataset produced by National Oceanic and Atmospheric Administration (NOAA). Results and study significance will be presented.

Climate is rapidly changing on a global scale; significant changes in frequency and severity of many extreme weather and climate events have been observed since at least 1950. Developing and least developed countries are particularly vulnerable to the impact of climate extremes, including drought. Recognizing the urgency of enhancing early warning systems to assist vulnerable countries with climate change adaptation, the Climate Risk and Early Warning Systems (CREWS) international initiative has been established in 2015. In this presentation, CREWS activities in Papua New Guinea (PNG) are described. In PNG, severe drought caused by the strong El Niño in 2015-2016 affected about 40% of the population, with almost half a million people impacted by food shortages. The CREWS-PNG project aims to develop an improved drought monitoring and early warning system (EWS), running operationally through a collaboration between PNG National Weather Services and the Australian Bureau of Meteorology. The developed drought EWS will enable better strategic decision making for agriculture, water management, health and other climate-sensitive sectors. CREWS-PNG is implemented in partnership with the World Meteorological Organization (WMO) Space-based Weather and Climate Extremes Monitoring (SWCEM) initiative, to assist the PNG NWS with enhancing drought monitoring, observations network and weather forecasting. SWCEM project provides countries in WMO regions II and V, including PNG, with access to satellite precipitation estimates and derived products.

Climate change is increasing the frequency and intensity of natural hazards, causing adverse impacts on vulnerable communities. Pacific Small Island Developing States (SIDS) are of particular concern, requiring resilient disaster risk management consisting of two key elements: proactivity and suitability. User-centred Integrated Early Warning Systems (I-EWSs) can inform resilient risk management. However, an EWS is only effectively integrated when all components are functioning adequately. In Pacific SIDS, the risk knowledge component of an I-EWS is underexplored. Risk knowledge is improved through efficient risk assessment. A case study assessing drought risk in PNG provinces was conducted to demonstrate the development and validate the application of an accurate and tailored risk assessment methodology. Hazard, vulnerability, and exposure indicators appropriate for monitoring drought in PNG provinces were selected. Risk indices for past years (2014-2020) were calculated and mapped in Geographic Information Systems (GIS). Risk assessment results were validated with a literature investigation of sources presenting information on previous droughts in PNG. The risk assessment indicated a strong drought event in 2015-2016, and a moderate event in 2019-2020. The literature corroborated this, confirming the validity of the risk assessment methodology. The methodology and results can be used to inform improved disaster risk management in PNG, by advising decision-makers of their risk and policymakers on which provinces are of priority for resource allocation. The methodology can also be used to enhance the risk knowledge component of a user-centred I-EWS and guide the implementation of such a system for drought in PNG and other Pacific SIDS.

In the present study, two experiments at 1-km grid size are compared on the extreme-rainfall event (up to 635 mm in 12 h) along the northern coast of Taiwan on 2 June 2017. The first is a forecast (F1km) that was driven by the best forecast member in a previous study at 3-km grid size (360 mm) and produced a peak amount of 541 mm along the northern shore (618 mm offshore), and the second is a simulation (S1km), driven by a 3-km simulation, that produced a maximum of 393 mm over land. The frontal moving speed are both slow in the two experiments, and the front spends slightly more time moving across the area in S1km (15 h) than in F1km (12 h). So, under similar conditions in most of the important factors previously identified, the present comparison allows us to examine the main differences between the peak rainfall amounts. The results show that in S1km, multiple rainbands moved slowly across northern Taiwan to produce the rainfall, with a more widespread heavy rainfall area, but the peak amount was less due to the transient nature of these rainbands (however slow they are). In F1km, on the contrary, linked to the presence of a low-pressure disturbance along the front, just to the north-northwest of Taiwan, the low-level westerlies were enhanced to produce a persistent convergence zone with the cold air behind the front, right across the northern tip of Taiwan without movement. Thus, one rainband remained at more or less the same location over several hours and produced the localized peak rainfall reaching 541 mm on land. The results indicate that it is possible to produce a higher peak amount with a finer grid size, but the predictability of such an extreme amount might be relatively low.

On 16 October 2021, localized torrential rainfall (> 70 mm h^-1) occurred in the slope area of northern Taiwan during an approaching surface front. Flash floods downstream of the catchment area resulted in a severe drowning accident without warning. In this observational study, the newly-established C-band disaster prevention rainfall radar in northern Taiwan is used for analysis and comparison. At local time 3-6 pm, extreme values of the specific differential phase K_DP (> 2° km^-1) can be used to identify the heavy rainfall region's location, intensity, and movement. For flash floods downstream of the catchment area, potentially, there is a priori warning capability. In this event, tracking intense and concentrated K_DP on complex terrain has an advantage over radar reflectivity. The direct application of K_DP on quantitative precipitation estimates can effectively complement the transmission-delay problem of ground rain gauges. This case also shows that intermittent lightning does not have much use for heavy rain warnings.

Since Nov. 2018, the Shanghai Meteorological Service (SMS) of CMA and Hunan Eastone Washon Corporation have jointly designed and developed the Shanghai Urban Radar Demonstration Observation Project based on a new X-band Phased Array Weather Radar (PAWR) network.
The Shanghai PWAR network consists of five Eastone Washon X-band phased array radars. Each radar works as a transmitter and receiver (TR) or sub-array. The PWAR uses a flat panel antenna composed of multiple electronic units constituting a one-dimensional phased array, which can electronically scan in the elevation plane without moving the antenna. It achieves fast scanning by using a digital multi-beam technology and a fan-thin beaming method, by using 16 beams to scan 4 times simultaneously to complete the 0–90° elevation scan within 0.125s. The antenna rotates in azimuth to finish a volume scan within 30s, with a radial resolution of 30m and a max range of 45km.
The Shanghai PAWR network has shown advantages in detecting the structure and evolution of local severe storms, MCSs, tropical cyclone rainbands. Some cases related to severe convective storms are analyzed using the PAWR network in this paper. A mini-supercell with a tornado and its tornadogenesis within a mesoscale vortex embedded in a Meiyu front is discussed by using phased array radar, while the mini-supercell could not be identified by the Shanghai S-band radar. Comparisons with the operational S-band radars show that by using higher spatial and temporal resolution reflectivity and more accurate 3D wind retrieval data, the PWAR system can capture the structure and dynamics of precipitation systems or storms in better detail than any other radar systems. The high spatial and temporal information of the PWAR network provides an opportunity to increase lead time of nowcasting of extreme winds, heavy rain, and large hail in Shanghai.

Mesoscale convective system (MCS) is the major contributor to seasonal rainfall and severe weathers in China. This study investigates the climatological characteristics of MCSs in China using 22-yr spaceborne precipitation radar observations, including MCS's spatial distribution, precipitation, environmental condition, convective intensity, and vertical structures. Compared to previous infrared-based studies, the TRMM-GPM MCS climatology shows far lower frequency over the Tibetan Plateau, greater topography-related gradients, and more realistic Meiyu rainband-associated signatures. Linear and non-linear MCSs account for 17% and 83% of the MCSs over China, respectively. Linear MCSs have much stronger convective intensity and heavier precipitation than non-linear MCSs, as indicated by TRMM convective proxies. Interestingly, though broad-stratiform MCSs own the weakest convection, they produce the heaviest (maximum) rainrate and the largest amount of heavy rainfall among non-linear MCSs. Among various types of linear MCSs, bow echoes (BEs) and no-stratiform (NS) systems exhibit the strongest convective intensity, embedded lines the weakest, and convective lines with trailing/leading stratiform in between. BEs and NSs share the most vertically extended structures, strongest microwave ice scattering, and highest lightning flashrates, but NSs have a much lower surface rainrate likely due to a drier environment. Vertical radar profiles suggest that both ice-based and warm-rain processes play an important role in the precipitation processes of linear MCSs over China, including the most intense BE storms. In short, this study helps to better understand the convective organizations, precipitation structures and ensemble microphysical properties of MCSs over China, and potentially provide guidelines for evaluating high-resolution model simulations and satellite rainfall retrievals on monsoonal MCSs.  

Due to the typhoon and its accompanied effect in the western North Pacific, observations have shown that the extreme precipitation areas frequently occur in the Yilan mountains of Taiwan, especially in the southeastern region. However, observations also showed heavy rainfall in this area as the tropical disturbances passed through the Bashi Channel and the northeast monsoon weakened. A long-lasting rainband can be found along the terrain by the radar observations, resulting in the prolonged extreme rainfall. Therefore, this is important for improving the forecast and the disaster prevention on the area under these above weather conditions.

In this study, the downscaled regional climate change information from the Coordinated Regional Climate Downscaling Experiment (CORDEX) – East Asia (EA) is analyzed to find changes and causes of the summer precipitation over the EA monsoon region. The Global/Regional Integrated Model system (GRIMs) – Regional Model Program (RMP) is utilized for the dynamical downscaling of the global climate model results from the coupled model intercomparison project phase 6 (CMIP6) under the shared socioeconomic pathway (SSP) scenarios. It is shown that the downscaled future scenarios (SSP126 and SSP585) depict increased EA summer precipitation in comparison with the historical results. The major two forcing terms (i.e., the vorticity advection and the temperature advection) in the quasi-geostrophic omega equation are analyzed in order to explain causes of the precipitation increase. The increased thermal instability by temperature advection changes in the future period shows contributions to the enhanced upward motions which induce cloud-precipitation processes. The changes of the baroclinic instability are relatively not significant than the thermal instability changes. Presented results describe detailed processes how the global warming changes the future precipitation of the EA monsoon system by enhanced vertical circulation. 

The changes in uncertainty components for future temperature and precipitation projections on East Asia for bias-corrected high-resolution multi-RCMs were quantitatively evaluated. For temperature, the main uncertainty factors in the annual mean and all seasons during the near-term projection are internal variability and model uncertainty, which decrease as time increases. The scenario uncertainty will tend to increase continuously. These results by RCMs are consistent with those of previous studies performed using GCMs. In the case of precipitation, the main uncertainty factors for the annual average and all seasons for the near-term projection are internal variability and model uncertainty. However, the main difference from temperature is that precipitation is predicted to have a significant contribution of internal variability even in the long-term projection from the fraction of total variance. In the results of annual precipitation and summer precipitation, model uncertainty due to differences in dynamical mechanisms between RCMs was found to be a major factor in precipitation uncertainty. Therefore, if the performance of the models is advanced through the improvement of the dynamical mechanism, the model uncertainty will be reduced, which will eventually narrow the total uncertainty. In winter precipitation, the scenario uncertainty due to the strengthening of climate change signals in long-term projection is expected to be the most dominant uncertainty component. In both temperature and precipitation of the near-term projection, the internal variability in the magnitude of fractional uncertainty and the fraction of total variance was predicted to be larger in South Korea than in East Asia. The importance of internal variability at a smaller regional scale during the near-term projection was confirmed not only in the GCMs in the previous studies but also in the RCMs of this study.

This study examined changes in the characteristics of heat waves (HWs) in South Korea by considering the spatial extent, intensity, and duration of the HWs, and projected future changes in electricity demands by identifying the relationship between HW characteristics and electricity demands. The magnitude is a new index that more accurately evaluates the effect of extreme high temperatures, and is calculated as the average intensity of the heat wave day (HWD) weighted with spatial extent. The frequency and magnitude of HWs have significantly increased during 1973-2019. According to the Representative Concentration Pathways (RCP) 8.5 scenario simulations, it was projected that wide, strong, and long-lasting HWs that have not been experienced would occur frequently in the late 21st century (2071-2100). Observations showed that the larger spatial extent, stronger intensity, and longer duration of HWs are associated with the higher demand for electricity. Based on the observed relationship, we provided an improved multiple regression model for electricity demand prediction, which includes the magnitude and duration of HWs as explanatory factors. According to the proposed model, in the late 21^st century, the daily peak electricity demands on HWDs were projected to increase by 9.1% compared to the present. In particular, the extreme value of daily peak electricity demand (30-yrs return level) was projected to increase by 19.1%, which was found to be alleviated to 4.6% when greenhouse gas emission is reduced following the RCP 2.6 scenario. 

East Asian Winter Monsoon (EAWM) is an important system, which has a significant impact on extreme winter phenomena, in East Asia including the Korean Peninsula. EAWM is characterized by Siberian high with cold air and Aleutian low with warm air, north wind in the lower troposphere, East Asian trough in the middle troposphere, and East Asian jet stream in the upper troposphere. According to several previous studies, the variability of EAWM, which can be affected by human activity and climate change, is strongly correlated with the occurrence of cold waves in East Asia and is one of the precipitation mechanisms for winter on the Korean Peninsula. Extreme winter phenomena such as cold waves and heavy snow related to EAWM are closely related to life and socio-economic damage. Meanwhile, the regional climate model (RCM) with an added value in regional simulation for extreme climate phenomena has internal variability, which can increase uncertainty in future climate projection. Therefore, in this study, in order to closely understand EAWM and lower the uncertainty of future climate projection, the simulation performance of multi-RCMs (SNURCM, HadGEM3-RA, WRF, and CCLM) was evaluated through spatiotemporal analysis. Specifically, precipitation, temperature, and atmospheric fields related to EAWM were analyzed using observation (APHRODITE, GPCP, etc.), reanalysis (ERA-Interim, ERA5, etc.), and multi-RCMs data. The results showed that multi-RCMs could capture the spatial distribution of EAWM despite the intensity difference of EAWM. We confirmed that the systematic errors of temperature and precipitation related to EAWM in multi-RCMs were influenced by temperature advection, sea surface temperature, and lower wind. Afterward, we are going to analyze the mechanism of the systematic errors quantitatively and closely.

The newly formed Australian Climate Service (ACS) aims to become an authoritative source of climate and hazard information that enhances our ability to prepare for, respond to, and recover from the impacts of natural hazards in a changing climate. Here we outline the modelling strategy for the production of climate projections data and information that will underpin the ACS. The ACS program will draw on the breadth of data available from the sixth phase of the Coupled Model Inter-comparison Project (CMIP6), including a direct analysis of several CMIP6-based large ensembles such as the 40-member ensemble produced by ACCESS-ESM1.5, a multi-model regional climate modelling ensemble produced under CORDEX2 protocols, and targeted convective-scale simulations for selected regions. The CORDEX2 ensemble will follow a ‘sparse matrix’ approach, including simulations from CCAM and BARPA which have been commissioned for the program, and will leverage work done for NARCliM, the Queensland state projections work, and international contributions to CORDEX Australasia. Host GCM selection from the CMIP6 archive has been guided by several factors, including data limitations, model performance, model independence, and representativeness in the projected change signal. Selection also accounts for the uneven spread of equilibrium climate sensitivities in CMIP6, noting the new ‘likely’ range defined in the IPCC Sixth Assessment Report. There are various challenges and considerations when using climate model data to derive quantitative and reliable projections, and here we outline the proposed model evaluation, model sub-selection and weighting, bias correction, and verification methods that will be deployed to produce these projections.

Climate models are not independent representations of the climate system, often sharing methods and code. This lack of independence means that climate model ensembles are not well represented as statistically independent samples. Hence, existing large climate model ensembles have been estimated to contain the same amount of information as would be contained in a much smaller set of independent models. Dynamical downscaling is usually constrained by computational resources such that only a subset of available models can be used. By choosing the most independent models in the ensemble the maximum amount of information can be retained for downscaling. Several methods to account for this model dependence have been proposed in recent years. These methods use very different approaches to defining and measuring model dependence. Here we apply three different techniques to an ensemble of 78 regional climate model simulations and assess the implications for independence-based model subset selection. While models indicated as most independent can differ between methods, a high level of agreement is found for the 10% most independent models.

In the present work, we analyzed the C-Structures Sporadic layers in the mesospheric metal layers using a high-resolution simultaneous Sodium and Potassium LIDAR, operating at São José dos Campos, Brazil (23°S,46°W). These events have different characteristics from those thin layers of metal concentration enhancement as reported for the first time by Clemesha et al. (1978). The present study focuses on these much rarer events that appear as C-shaped structures in the lidar height/time display. A total of 9 C-Structures events were found within 185 nights of simultaneous Na-K LIDAR data, measured between 2017 and 2019. These events show an averaging height range of 5.1 km. They last from half to a few hours, 90 min on average. We also used ionosonde for Es layer investigation and wind measurements from an all-sky interferometric meteor wind radar, both located at Cachoeira Paulista, a nearby location. An analysis of their formation, together with simultaneous meteor winds and Es measurements, as well their similar characteristics in both Na and K layers, suggests that the observed structures might be the result of the wind-shear distortion of pre-existing clouds of enhanced sodium and potassium concentration.

The Richardson number (Ri), which combines the convective state of the atmosphere with wind shear, describes a criterion which leads to Kelvin-Helmholtz instabilities (KHI) and turbulence when Ri<0.25.  Observations in the MLT using lidars, ground-based imagers, and chemical releases have provided insights to conditions that leads to KHI. The NASA ICON satellite instrumented with the MIGHTI (Michelson Interferometer for Global High-resolution Thermosphere Imaging) instruments provide Doppler winds and separately, molecular rotational temperatures from the O₂ Atmospheric band emissions. These observations were used to determine the Ri between 98 and 106 km, a region where turbulence generated eddy diffusion competes with molecular diffusion, defining the altitude of the turbopause (~100km) and the vertical flux of minor constituents and heat. The analysis reported herein is for 2020, where the intra-annual, diurnal, and latitudinal (four zones between 12^oS and 36^oN) values are determined.  The conclusion from these measurements is that the region is near, or in KHI conditions most of the time, with no discernable change with the day of the year, but a slightly higher probability of unstable conditions in the equatorial region than at midlatitude.  It has been understood that this region is characteristically dominated by large amplitude tides (and shears), but the extent and consistency in time and space strongly supports the importance they have in the generation of KHI near the turbopause.

The Electrojet Zeeman Imaging Explorer (EZIE) is a NASA CubeSat mission focused on studying the auroral electrojet current system in Earth’s atmosphere by measuring for the first time the magnetic signal in the 80 km altitude range. EZIE consists of three CubeSats, each equipped with four beams looking downward toward nadir direction, able to measure the molecular oxygen thermal emission and derive the magnetic field via Zeeman splitting. In addition to the magnetic field, highly precise line-of-sight neutral wind and temperature measurements can be retrieved by observing the O2 emission. This presentation will give an overview of the EZIE mission and details about the anticipated wind retrieval with respect to expected precision, flexible observing geometry, and location.  To gain further insights into the ability to capture the local wind system we use high-resolution Whole Atmosphere Community Climate Model eXtended (WACCM-X) simulations to develop Observing System Simulation Experiments (OSSE). We will show examples of the OSSE used in the wind fitting based on the Spherical elementary current system (SECS) method to demonstrate the capabilities of the EZIE mission. EZIE is scheduled to launch in the fall of 2024.

Recent observational studies have found that the topographic environment has an important impact on the middle and upper atmosphere and ionosphere, and the fluctuation characteristics of the middle and upper atmosphere and ionosphere are different in different latitudes and longitudes. China, from north to south, spans from the middle latitudes to the low latitude both in geographic latitude and geomagnetic latitude. And China has a variety of topography environment, which including high lands, hill, plains, seas, and long coasts. This is a natural laboratory to study the effects of different latitudes and topography on the middle and upper atmosphere. Airglow observation is one of the important means to study the middle and upper atmosphere. We have established a ground-based airglow network in China gradually since 2010, which consists of 16 stations and more than 40 all sky imagers. The network almost covers China and has double-layer detection capability, which focuses on two airglow layers: the red line of atomic oxygen (~250 km) and OH (~87 km) airglow layers. In some stations, we also make observations of green line and 777.4 nm of atomic oxygen and sodium layer airglow at 589 nm.  This report will introduce the airglow network and related research progresses, which include thunderstorm and typhoon effects, influence of Tibet Plateau on gravity waves, characteristic of equatorial plasma bubble (EPB) and medium-scale traveling ionospheric disturbance (MSTIDs), and so on.

PANSY radar at Syowa station (69S, 39E) has been conducting continuous mesosphere, stratosphere and troposphere observations as the only MST/IS radar in the Antarctic [Sato et al., 2014, JASTP]. These observation techniques are characterized by their three dimensional wind velocity measurement ability including vertical wind component with high time/height resolutions. The mesosphere observations, however, need ionized media in the mesosphere and are limited to day-light hours. To compensate this we have developed an external interferometry system for reception which can detect meteor echoes throughout a day in the height region of 70-95 km as purely by-products of the routine mesosphere measurements. A pioneering external meteor system attached to the MU radar, Japan, by Nakamura et al [1997, Radio Sci.] is a proto-type of the current system. The newly developed system, consisting of five Yagi antennas, has continuously been operating since March 2021. The number of detected meteor echoes is comparable to or even more than that of commercial meteor radars. Inter-comparison with the routine mesosphere wind measurements and analyses of mean winds and atmospheric waves are to be made.

Precise and high-resolution carbon dioxide (CO₂) emission data is of great importance of achieving the carbon neutrality around the world. Here we present for the first time the near-real-time Global Gridded Daily CO₂ Emissions Dataset (called GRACED) from fossil fuel and cement production with a global spatial-resolution of 0.1° by 0.1° and a temporal-resolution of 1-day. Gridded fossil emissions are computed for different sectors based on the daily national CO₂ emissions from near real time dataset (Carbon Monitor), the spatial patterns of point source emission dataset Global Carbon Grid (GID), Emission Database for Global Atmospheric Research (EDGAR) and spatiotemporal patters of satellite nitrogen dioxide (NO₂) retrievals. Our study on the global CO₂ emissions responds to the growing and urgent need for high-quality, fine-grained near-real-time CO₂ emissions estimates to support global emissions monitoring across various spatial scales. We show the spatial patterns of emission changes for power, industry, residential consumption, ground transportation, domestic and international aviation, and international shipping sectors from January 1, 2019 to December 31, 2020. This gives thorough insights into the relative contributions from each sector. Furthermore, it provides the most up-to-date and finer-grained overview of where and when fossil CO₂ emissions have decreased and rebounded in response to emergencies (e.g. COVID-19) and other disturbances of human activities than any previously published dataset. As the world recovers from the pandemic and decarbonizes its energy systems, regular updates of this dataset will enable policymakers to more closely monitor the effectiveness of climate and energy policies and quickly adapt.

With the growing ambition and urgency of climate change mitigation, many European Union countries raised time-bound national goals for carbon emissions reductions. However, annual estimates of national CO2 emissions can only provide historical changes and progress. Carbon Monitor has been producing near-real-time daily estimates of global CO2 emissions since 2020 which cover 7 main countries and regions of the world. Using a diverse range of activity data compiled from numerous sources, here we present near-real-time daily country-level and sector-specific emissions of 27 European Union countries and the United Kingdom from 2019 to 2021. Our results not only show the abrupt decreases in CO2 emissions due to lockdowns during the COVID-19 pandemic but the strong rebound in 2021. As EU countries recover from the pandemic, regular updates of this dataset will enable governments to monitor the effectiveness of climate and progress towards carbon neutrality.

National Park, as an important part of the natural protected area, is the cornerstone for effectively maintaining biodiversity and mitigating global climate change. At present, China is in full swing to national parks as the main body of the natural protection system construction work, especially considering the urge target to achieve carbon neutrality and mitigate climate change for China. It is of great significance to accurately predict the carbon source and sink function and carbon storage of the national park ecosystem under global change for the national carbon neutralization strategy. Here based on the integration of advanced modeling, satellite measurements, and scenario analysis, this study will present our recent research about evaluating the carbon sink capacity of the proposed Kunlun Mountain National Park under a multiple management scheme. Our result will provide data and references for interdisciplinary scientists across fields of environmental management, ecology, and nature reserve sciences, as well as policymakers and the public.

The diversification or decoupling of production chains from China to alternative Asian countries such as India or Indonesia would impact the spatial distribution of anthropogenic emissions, with corresponding economic impacts due to mortality associated with particulate matter exposure. We evaluated these changes using the Community Earth System Model, the Integrated Exposure-Response (IER) model and Willingness To Pay (WTP) method. Significant effects on PM_2.5 related mortality and economic cost for these deaths were seen in many East, Southeast and South Asian countries, particularly those immediately downwind of these three countries. Transferring all of export-related manufacturing to Indonesia resulted in significant mortality decreases in China and South Korea by 78k (5 per 100k) and 1k (2 per 100k) respectively, while Indonesia’s mortality significantly increased (73.7k; 29 per 100k), as well as India, Pakistan and Nepal. When production was transferred to India, mortality rates in East Asia show similar changes to the Indonesian scenario, while mortalities in India increased dramatically (87.9k; 6 per 100k), and mortalities in many neighbors of India were also severely increased. Nevertheless, the economic costs for these deaths were much smaller than national GDP changes in China (0.9% of GDP vs. 18.3% of GDP), India (2.7% of GDP vs. 84.3% of GDP) or Indonesia (9.4% of GDP vs. 337% of GDP) due to shifting all of export-related production lines from China to India or Indonesia. Morally, part of the benefits of economic activity should be used to compensate the neighboring communities where mortality increases occur.

International trade allows consumption of any region to be supplied by production worldwide. This affects the magnitude and geographical pattern of consumption associated emissions, which differ greatly from those of emissions associated with regional production (as in a typical emission inventory). Yet the climate influence of aerosols emissions associated with regional consumption remains unknown, despite that understanding this issue offers crucial information to support policymaking and international cooperation in climate change mitigation action from a consumption perspective. Here we quantify for the first time the effects of sulfate aerosol associated with consumption of developed and developing countries on global temperature and precipitation, by integrating a most current-generation fully coupled Earth system model (CESM2), a recent multi-regional input-output table (GTAP) and an updated emission inventory for CMIP6 climate simulations (CEDS). We find that despite large emission differences between developed and developing countries, consumption associated sulfur emissions of both regions lead to comparable impacts on the global mean surface air temperature. This is due to 1) the difference between developed and developing countries in the spatial distribution of consumption associated sulfate, and 2) the response of the nonlinear climate system to the spatial pattern of aerosol forcing. We further discuss the regional patterns of temperature and precipitation responses to sulfur emissions. This study serves as the first step of a comprehensive assessment of the climate response to the whole suite of consumption associated pollutants (black carbon, organic carbon, sulfate, ozone, etc.), complementing prevailing regional attribution analyses of climate change based on production associated emissions and radiation forcing.

Atmospheric transport of PM2.5 and ozone is estimated to exert substantial transboundary effects at present. During the past several decades, human-produced pollutant emissions have undergone drastic and regionally distinctive changes, yet it remains unclear about the resulting global transboundary health impacts. Here we show that between 1950 and 2014, global anthropogenic PM_2.5 has led to 185.7 million premature deaths cumulatively, including about 14% from transboundary pollution. Among four country groups at different affluence levels, on a basis of per capita contribution to transboundary mortality, a richer region tends to exert severer cumulative health externality, with the poorest bearing the worst net externality after contrasting import and export of pollution mortality. The temporal changes in transboundary mortality and cross-regional inequality are substantial. We find that transboundary mortality increases by 27 times from 1951 to 2019, and on average contributes about 27% of global anthropogenic ozone-related deaths. All groups exert and suffer from substantial transboundary mortality. The high-income and upper middle groups have each experienced a reverse U-shaped relationship between its affluence and per-million-people contribution to transboundary mortality. The lower middle group has gradually matched the growth pathway of the upper middle group with a turning point less clear. Effort to reduce transboundary mortality should seek international collaborative strategies that account for historical responsibility and inequality.

El Niño-Southern Oscillation (ENSO) plays an important role in rainfall variability over various regions in Asia, including the Indochina Peninsula (ICP). The influence of ENSO on regional rainfall variability may vary with the season and display interdecadal changes. This talk presents evidence for different impacts of ENSO on the ICP rainfall variability in different stages of the rainy season and interdecadal changes in the relationship of ICP rainfall to ENSO. More May-June, July-August and October-November rainfall falls over the ICP in the La Niña decaying years, La Niña decaying years and/or El Niño developing years, and La Niña developing years, respectively, during 1979-2016. The formation of rainfall anomalies in the three stages is attributed to a combined effect of regional SST anomalies in different regions. The relationship of May ICP precipitation to ENSO experienced interdecadal changes during 1951-2016. During the 1950s through the late-1970s, more (less) ICP rainfall tends to occur in May of La Niña (El Niño) developing years, whereas after the late-1990s, more (less) ICP rainfall tends to appear in May of La Niña (El Niño) decaying years. During the late-1970s through the late-1990s, more (less) ICP rainfall occurs in May of La Niña (El Niño) persisting years. The interdecadal change in the ICP May rainfall-ENSO relationship is related to changes in the developing time of ENSO events and tropical Indo-Pacific SST anomaly pattern. A prominent change is detected in the relationship between August ICP rainfall and tropical Pacific SST around 1980. More August ICP rainfall falls in La Niña developing years during 1959-1979, but in El Niño developing years during 1983-2003. The change is associated with a different temporal evolution of equatorial Pacific SST anomalies before and after 1980.

This study investigates the rainfall anomaly patterns over Asia associated with interannual variations of early summer (May-June) and peak summer (July-August) Indochina Peninsula (ICP) rainfall during 1979-2016. The early and peak summer rainfall variation in the ICP displays an out-of-phase relation to that in central Asia and central China, respectively. The out-of-phase early summer rainfall variation between the ICP and central Asia tends to occur in ENSO decaying years and the out-of-phase peak summer rainfall variation between the ICP and central China tends to occur in ENSO developing years. The early summer out-of-phase rainfall anomaly pattern between the ICP and central Asia forms due to a Rossby wave type response to anomalous heating extending from the ICP to northeast India, which is attributed to a combined influence of same sign SST anomalies in the equatorial central-eastern Pacific and southwestern tropical Indian Ocean and opposite sign SST anomalies in the tropical western North Pacific. The peak summer out-of-phase rainfall variation between the ICP and central China forms due to a meridional atmospheric circulation pattern over East Asia and the western North Pacific, which is resulted from the combined impacts of opposite SST anomalies in the equatorial central-eastern Pacific and tropical southeastern Indian Ocean.

Droughts are among the most damaging natural disasters over Asia. The occurrence of droughts is associated with different factors. For the drought measured by Standard Precipitation Evaporation Index (SPEI), its variations are contributed by both precipitation and temperature. Due to the different sources of precipitation and temperature variations, the characteristics and factors of SPEI-measured droughts may depend upon the time scale and location of droughts in concern. In this talk, we will present an analysis of contributions of precipitation and temperature to the spatial patterns and temporal variations of drought with different durations over Asia measured by SPEI. Our results show that the SPEI displays a large component of trend, which is attributed to the contribution of the temperature trend. The 3-month SPEI (SPEI03) and 9-month (SPEI09) display a dominant dipole pattern and 24-month SPEI (SPEI24) displays a leading tripole pattern, all of which are related to both precipitation and temperature variations. The dipole pattern of SPEI24 is mainly due to temperature trend. The dipole (tripole) pattern of SPEI24 has a closer link to the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO), respectively.

An anomalous strengthening in western Pacific subtropical high (WPSH) increases moisture transport from the western equatorial Pacific to East Asia, inducing anomalous boreal summer monsoonal rainfall, causing extreme events in the densely populated region. Although such positive WPSH anomalies can be induced by anomalous warming in the Indian and/or the tropical Atlantic Ocean, the majority of the events develop concurrently with anomalous cold sea surface temperature (SST) in the central Pacific (CP) where an incipient La Niña occurs, promoting anomalous anticyclonic anomalies over the northwestern Pacific region. How variability of the WPSH might respond to greenhouse warming remains unclear. Using outputs from 32 latest climate models, here we find an increase in WPSH variability translating into a 73% increase in the frequency of strong WPSH events under a business-as-usual emission scenario supported by a strong inter-model consensus. Under greenhouse warming, the response of tropical atmosphere convection to CP SST anomalies increases, as does the response of the northwestern Pacific anticyclonic circulation. Thus, climate extremes such as floods in the Yangtze River Valley of East China associated with WPSH variability are likely to be more frequent and more severe.

Rainbands that migrate northward from spring to summer are persistent features of the East Asian summer monsoon. This study employs a machine learning algorithm to identify individual East Asian rainbands from May to August in the 6-hourly ERA-interim reanalysis product, and captures rainband events during these months for the period 1979-2018. The median duration of rainband events at any location in East Asia is 12 hours, and the centroids of these rainbands move northward continuously from approximately 28°N in late May to approximately 33°N in July, instead of making jumps between quasi-stationary periods. While the length and overall area of the rainbands grow monotonically from May to June, the intensity of the rainfall within the rainband dips slightly in early June before it peaks in late June.  We explore circulation features associated with rainband formation through compositing of rainband days. Extratropical northerly winds on all pressure levels over East China are the most important anomalous flow accompanying the rainband events. The anomalous northerlies augment climatological background northerlies in bringing low moist static energy air and thus generate the front associated with the rainband. Persistent lower tropospheric southerly winds bring in moisture that feeds the rainband and are enhanced a few days prior to rainband events, but are not directly tied to the actual rainband formation.

This study investigates future changes in East Asian summer monsoon (EASM) precipitation and the associated atmospheric circulation changes based on ensemble projections with a 60-km mesh atmospheric general circulation model (MRI-AGCM60). The projections at the end of the twenty-first century under the Representative Concentration Pathway 8.5 (RCP8.5) scenario indicate an overall increase in EASM precipitation but with large sub-seasonal and regional variations. In June, the Meiyu–Baiu rainband is projected to strengthen, with its eastern part (i.e., the Baiu rainband) shifted southward relative to its present-day position. This result is robust within the ensemble simulations. In July and August, the simulations consistently project a significant increase in precipitation over the northern East Asian continent and neighboring seas; however, there is a lack of consensus on the projection of the Meiyu–Baiu rainband in July. A small change in precipitation over the Pacific is another feature in August.
Results of sensitivity experiments with the MRI-AGCM60 reveal that the precipitation changes in early summer are dominated by the effects of sea surface temperature (SST) warming (i.e., uniform warming and the tropical pattern change), inducing an increase in atmospheric moisture and a strengthening and southward shift of the upper-level East Asian westerly jet (EAJ), especially over the Pacific. On the other hand, the influence of land warming and successive large SST warming in the extratropics is apparent in the precipitation changes in late summer. These late summer effects oppose and exceed the early summer effects through changes in the EAJ and low-level monsoon winds. These results suggest that the competition between the opposing factors makes the signal of the Meiyu–Baiu rainband response smaller in July than in June. Therefore, there tends to be a larger spread among simulations regarding the future tendency of the rainband in July.

How ENSO has changed during the Pleistocene has remained elusive. Here we present results from the first transient simulation conducted to date with a Coupled General Circulation Model (CESM1.2) which covers earth's history of the past 3 million years. The model simulation uses acceleration of the external forcings by a factor of 5. Therefore, the entire CESM1.2 dataset available comprises 600,000 model years. Our analysis focuses on the combined effects of CO2, orbital and ice-sheet forcing on tropical mean climate, the annual cycle and ENSO dynamics. We will discuss the effect of the mid-Pleistocene transition on ENSO complexity and the forcing combinations that generate the most extreme El Niño events during the entire Pleistocene. We will compare the projected future ENSO changes in CESM1.2 with those from the paleo-simulation to determine the potential emergence of no-analogue conditions.

Sea surface temperature (SST) variability of El Niño-Southern Oscillation (ENSO) underpins its global impact, and its future change is a long-standing science issue. In its sixth assessment, the Intergovernmental Panel on Climate Change (IPCC) reaffirms increased ENSO extreme rainfall anomalies but reports no systematic change in ENSO SST variability under any emission scenarios considered.  However, comparison between the 20^th and 21^st century shows a robust increase in century-long ENSO SST variability under four IPCC plausible emission scenarios.

The majority of future projections in the Coupled Model Intercomparison Project (CMIP5) show more frequent exceedances of the 5 mm day21 rainfall threshold in the eastern equatorial Pacific rainfall during El Niño, pre- viously described in the literature as an increase in ‘‘extreme El Niño events’’; however, these exceedance frequencies vary widely across models, and in some projections actually decrease. Here we combine single-model large ensemble simulations with phase 5 of the Coupled Model Intercomparison Project (CMIP5) to diagnose the mechanisms for these differences. The sensitivity of precipitation to local SST anomalies increases consistently across CMIP-class models, tending to amplify extreme El Niño occurrence; however, changes to the magnitude of ENSO-related SST variability can drastically influence the results, indicating that understanding changes to SST variability remains imperative. Future El Niño rainfall intensifies most in models with 1) larger historical cold SST biases in the central equatorial Pacific, which inhibit future increases in local convective cloud shading, enabling more local warming; and 2) smaller historical warm SST biases in the far eastern equatorial Pacific, which enhance future reductions in stratus cloud, enabling more local warming. These competing mechanisms complicate efforts to determine whether CMIP5 models under- or overestimate the future impacts of climate change on El Niño rainfall and its global impacts. However, the relation between future projections and historical biases suggests the possibility of using observable metrics as ‘‘emergent constraints’’ on future extreme El Niño, and a proof of concept using SSTA variance, precipitation sensitivity to SST, and regional SST trends is presented.

El Niño-Southern Oscillation (ENSO) events occasionally recur one after the other in the same polarity, called multi-year ENSO. To date, multi-year El Niño and La Niña have been investigated separately in the literature. Given the lack of comprehensive understanding to this phenomenon, this study aims at clarifying mechanisms of multi-year El Niño and La Niña in a unified manner. Mechanisms for multi-year ENSO are explored using atmosphere and ocean reanalysis datasets. It is first confirmed that multi-year El Niño and La Niña events account for approximately 30% and 60% of the respective total events. Because multi-year El Niño and La Niña events are, with a few exceptions, roughly symmetric in its characteristics (i.e., duration and magnitude), they are combined to produce a composite time evolution of multi-year ENSO, which is compared with conventional single-year ENSO. For the multi-year ENSO event, anomalous upper-ocean heat content (OHC) in the equatorial Pacific does not change the sign during the first peak, which stimulates another event to occur in the following year. The ocean heat budget analysis showed that this prolonged OHC anomaly is caused by meridional surface Ekman heat transports counteracting geostrophic transports that otherwise act to change the OHC anomaly. A latitudinally wide pattern of sea surface temperature (SST) anomaly observed during the multi-year events is responsible for the net Ekman transport to recharge/discharge the equatorial ocean mass during the first decay phase of multi-year El Niño/La Niña. Climate simulations by Coupled Model Intercomparison Project Phase 6 (CMIP6) Earth System models support the above mechanism and show a significant correlation between the meridional width of the ENSO SST anomalies and the occurrence ratio of multi-year ENSO events across the models.

Regional-scale precipitation responses over Indonesia to major climate modes in the tropical Indo–Pacific Oceans, i.e., canonical El Niño, El Niño Modoki, and the Indian Ocean Dipole (IOD), and how the responses are related to large-scale moisture convergences are investigated. The precipitation responses, analyzed using a high-spatial-resolution terrestrial precipitation dataset for the period 1960–2007, exhibit differences between the dry (July–September) and wet (November–April) seasons. Canonical El Niño strongly reduces precipitation in central to eastern Indonesia from the dry season to the early wet season and northern Indonesia in the wet season. El Niño Modoki also reduces precipitation in central to eastern Indonesia during the dry season, but conversely increases precipitation in western Indonesia during the wet season. Moisture flux analysis indicates that corresponding to the dry (wet) season precipitation reduction due to the canonical El Niño and El Niño Modoki anomalous divergence occurs around the southern (northern) edge of the convergence zone when one of the two edges is located near the equator (10°S–15°N) associated with their seasonal migration. This largely explains the seasonality and regionality of precipitation responses to canonical El Niño and El Niño Modoki. IOD reduces precipitation in southwestern Indonesia in the dry season, associated with anomalous moisture flux divergence. The seasonality of precipitation response to IOD is likely to be controlled by the seasonality of local sea surface temperature anomalies in the eastern pole of the IOD.

Characterizing error structures in precipitation products not only facilitates their proper applications for scientific and practical purposes but also helps improve their retrieval algorithms and processing methods. Despite the fact that multiple precipitation products have been assessed in the literature, factors that affect their error structures remain inadequately addressed. This study presents a novel approach to systematically and objectively analyze the error structure within precipitation products using decision trees. This data-driven method can analyze multiple factors simultaneously and disentangle the performance of precipitation products with various factors. By interpreting 60 binary decision trees, this study disentangles the error characteristics of precipitation products in terms of their spatiotemporal patterns and geographical characteristics. Two satellite-based and one reanalysis precipitation datasets, including the Integrated Multi-satellitE Retrievals for GPM (IMERG), Soil Moisture to Rain-Advanced SCATterometer (SM2RAIN-ASCAT), and the land component of the fifth generation European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5-Land), are evaluated for the contiguous United States (CONUS) from 2010 to 2019. The ground-based Stage IV precipitation dataset is used as the ground truth. Results indicate that IMERG and ERA5-Land perform better than SM2RAIN-ASCAT with higher accuracy and more stable interannual patterns for the analysis period. The conventional bias evaluation finds that ERA5-Land and SM2RAIN-ASCAT underestimate in summer and winter, respectively. The decision tree method cross-assesses three spatiotemporal factors and finds that underestimation of ERA5-Land occurs in the eastern part of the Rocky Mountains, and SM2RAIN-ASCAT underestimates precipitation over high latitudes, especially in winter. Additionally, the decision tree method ascribes system errors to nine geographical characteristics, of which the distance to the coast, soil type, and DEM are the three dominant features. On the other hand, the land cover type, topography position index, and aspect are three relatively weak factors.

This paper proposes a new quantitative precipitation estimation (QPE) technique to provide accurate rainfall estimates in complex terrain, where conventional QPE has limitations. The operational radar QPE in Taiwan is mainly based on each Radar's single R(Z) relation and only utilizes the single-point lowest available echo to estimate rain rates, leading to low accuracy in complex terrain. Here, we conduct QPE using deep learning that extracts features from 3-D radar reflectivities to address the above issues. Convolutional neural networks (CNN) are used to analyze contoured frequency by altitude diagrams (CFADs) to generate the QPE. CNN models are trained on existing rain gauges in northern and eastern Taiwan with the three-year data during 2015−17 and validated and tested using 2018 data. To handle the unbalanced rainfall data and improve the accuracy, the weights of heavy rains (≧10 mm h^-1) are increased in the model loss calculation. Results show that the CNN outperforms the R(Z) relation based on the 2018 rain-gauge data. Furthermore, this research proposes methods to conduct 2-D grided QPE to increase the forecast practicability. Verification based on independent rain gauges shows that the CNN QPE solves the underestimation of the R(Z) relation in mountainous areas. In addition, case studies are presented to visualize the results, showing that the CNN QPE generates better small-scale rainfall features and more accurate precipitation information. This deep learning QPE technique may be helpful for the disaster prevention of small-scale flash floods in complex terrain.

In the present era of big data, artificial intelligence (AI) based machine learning (ML) is an important tool to trawl for the hidden associations between different hydrometeorological precursors and hydroclimatic variables. It is expected to reveal non-linear relationship, thereby, improving the weather forecast and future climate projections. Among several hydroclimatic variables, air temperature is one of the most contributing variables towards several climatic conditions severely impacting the flora and fauna species residing on earth at present and its impact is expected to intensify with time. The present study analyses the potential of a novel hybrid approach, namely Conv1D-LSTM, comprising of a one-dimensional Convolutional Neural Network (Conv1D) and Long Short Term Memory (LSTM) neural network in forecasting multi-step ahead (1-day to 10-day ahead) daily air temperature using hydrometeorological precursors. The proposed approach is applied to a few major highly urbanized areas in India, specifically 9 metropolitan cities, namely Ahmedabad, Bengaluru, Chennai, Hyderabad, Kolkata, Mumbai, New Delhi, Pune, and Surat. The performance is compared with four other popular ML approaches, viz. Conv1D, LSTM, Multi-Layer Perceptron (MLP), and Support Vector Regression (SVR). The aforesaid extensive evaluation is carried out using three statistical measures namely coefficient of correlation, root mean square error, and Nash-Sutcliffe efficiency, and shows a clear dominance of the hybrid approach at all lead times. The developed hybrid ML approach is expected to be useful in many fields of applications, even including electricity demand during different weather conditions and natural hazards such as wildfires, agriculture, design of solar power energy systems, etc.

Raw forecasts from numerical weather prediction models suffer from systematic bias and cannot be directly used in applications such as hydrological forecasting. Statistical post-processing methods can be used to remove the bias and achieve reliable ensemble forecasts. However, traditional post-processing methods only use local precipitation forecasts as the only predictor, which limits their ability to extract information from raw forecasts. Therefore, we develop a LeNet-type convolutional neural network-based post-processing method for precipitation forecasts to fully make use of spatial information and auxiliary predictors and quantify uncertainty of forecasts. We compare the proposed model with a state-of-the-art post-processing model and an ANN-based model. The results show that CNN-based post-processing model performs better than traditional methods in forecast accuracy, especially for heavy rain. Moreover, CNN-based models transcend ANN-based model by using convolution layers to extract spatial information. Existing results illustrate the advantages of CNN-based post-processing models to extract spatial information and different meteorological auxiliary predictors to improve precipitation forecast skill.

The track of tropical cyclones (TCs) formed in the South China Sea (SCS) can be divided into eastward and westward directions. Significant decadal variation during 1980-2020 only exists in the number of eastward-moving TCs, especially during July-September, with 47% TCs moving eastward during 1994-2004 (Period II), 22% during 1980-1993 (Period I) and only 15% during 2005-2020 (Period III). This decadal change is related to the zonal shift of Western Pacific Subtropical High (WPSH). An eastward-retreated WPSH during 1994-2004 leads to upward motion and westerly flow anomaly over the northern SCS, and therefore favors TC genesis and eastward motion. The eastward-retreated WPSH is associated with a warm SST anomaly over the tropical western-central Pacific which induces a cyclonic flow and weakens the WPSH. With the weaker modulation of WPSH, stronger intraseasonal oscillation (ISO) in the SCS during Period II favors eastward-moving TCs due to the westerly flow associated with the ISO.

This study analyzes the spatiotemporal distributions and climate trends of the TC-induced extreme hourly precipitation (EXHP) in the warm season (May-September) during 1975-2018 over China and the involved possible mechanisms. Each TC is classified as a high-, mid-, and low-EXHP TC according to the total number of EXHP it produces over China. Results show that low-EXHP TCs have a greater contribution to the total TC-induced EXHP over southern and southwestern China, whereas high-EXHP TCs make greater contributions over eastern and northeastern China as they tend to move northwestward after making landfall. It is shown that, although the total frequency of EXHP-producing TCs display a decreasing trend, the total frequency of TC-induced EXHP over China shows a significant increasing trend, which is largely contributed by the high-EXHP TCs. To explore the possible mechanisms responsible for the different characteristics in EXHP-producing TC groups, we further analyze the large-scale environmental conditions with respect to three groups by composite analysis. The cooperation of large-scale environmental fields between high- and low-levels provide favorable conditions for the intensification of TCs and the enhancement of the TC-induced precipitation for the high-EXHP group, such as stronger divergence at high-level, weaker vertical wind shear, more sufficient water vapor and more conducive steering airflow over the southeastern and eastern areas of mainland China. The westward and northward movement of western North Pacific subtropical high is conducive to the northward shift of TC tracks, thus contributing to the high frequency of TC-induced EXHP over the eastern area of mainland China.

This paper studies the characteristics of lightning in Shenzhen under the influence of tropical cyclones. Using the historical data of tropical cyclones (TCs) in the Northwest Pacific Ocean from 2012 to 2019, the TCs within 1000 km to the Shenzhen National Meteorological Basic Station from 2012 to 2019 are screened and grouped according to the intensity of tropical cyclones. And using the lightning and temperature observation data in Shenzhen during the same period, the lightning characteristics induced by TCs with different intensity levels at various distances and azimuths in Shenzhen are studied. It is found that the inter-annual variation of lightning in Shenzhen under the influence of TCs is very large, and the lightning activity in Shenzhen is the most active in July and August in a year. Most of the distances where TCs have a great impact on lightning activities in Shenzhen are beyond 400 km. That means Shenzhen is in the outer rainband of TCs. Generally, during TCs’ season, TD, TS, and STS are more likely to cause lightning in Shenzhen, especially when TS is located in the Fujian area, 400-600 km away from Shenzhen. This article can provide scientific and technological references for TCs disasters prevention and mitigation in Shenzhen.

Tropical cyclones are devastating natural hazards that threaten lives, infrastructure and the environment. Impacts can be felt in the form of damaging winds, heavy sustained rainfall leading to flooding and landslides, as well as storm surges leading to coastal inundation. In recent years for the country of Papua New Guinea (PNG), tropical cyclones have taken lives, left people homeless and destroyed infrastructure as well as agricultural crops vital to the country’s economy. With a high percentage of their population situated in the highlands, many communities are susceptible to heavy rainfall hazards such as floods and landslides, while the rest of the population living near the coast are hit by cyclonic winds first and potential coastal inundation due to storm surge. This study collated provincial data on population characteristics, land use/cover, critical infrastructure, elevation, and economical output among other variables to build exposure and vulnerability indices for PNG. Combined with future projections of tropical cyclone hazard’s location and occurrence, a risk index was created. Results were displayed as a risk map, viewable in a web application allowing for a user-friendly interface to compare values and give a snapshot of spatial trends. Resultant trends are discussed in this study, as well as discussion of implications and suggestions for the future.

Recent years have seen a rapid increase in wildfire behaviour and damage in areas including Australia, the United States, Canada and Europe. Meteorology, on all scales, plays a major role in setting the conditions for, and modulating the short-term behaviour of, catastrophic wildfires. Spotfires are a one of many major problems in bushfire management, and in extreme circumstances have been observed to ignite new fires over 30 km ahead of the parent fire. Spotfires result from firebrands transported from the fire plume igniting fuel well ahead of the front. They greatly complicate suppression efforts, contribute to fires breaking control lines, and are implicated in structure loss. Existing forecast techniques provide insufficient guidance on the problem of long-range spotting, and the meteorological and fire conditions that lead to such events are not well understood. We present a computationally inexpensive, physically based model of firebrand transport within bushfire plumes, with four components: an integral plume model, a model of turbulence within the plume, a probabilistic model of firebrand transport within the plume, and a model of transport beneath the plume. The predicted firebrand landing distributions from this model compare satisfactorily to the explicit transport calculations of Thurston et al. (2017). We examine the sensitivity of the simple model to its input parameters. The 90th percentile of spotting distance increases with increasing fire power and decreases with increasing firebrand terminal fall velocity and fire radius. Where there is a meteorological inversion and the plume updraft is sufficiently strong to carry firebrands that high, the inversion substantially limits the transport distance, with increased inversion height favouring longer-range transport. The effect of wind speed is complex, due to the competing factors of faster horizontal transport but suppressed vertical plume development with stronger winds.

Deep convection plays important roles in producing severe weather and regulating the large-scale circulation. However, deep-convection initiation (DCI), which determines when and where deep convection develops, has not yet been fully understood. Here, large-eddy simulations are performed to investigate the detailed processes of DCI, which occurs through the collision of two sea-breeze fronts developing over a peninsula. In the simulation with a maximum total heat flux over land of 700 or 500 W m^-2, DCI is accomplished through the development of three generations of convection. The first generation of convection is randomly produced along the colliding sea-breeze fronts. The second generation of convection only develops in regions where no strong downdrafts are produced by the first generation of convection and is also mainly produced through the collision of the sea-breeze fronts. The third generation of convection mainly develops from the intersection points of the cold pools produced by the second generation of convection and is produced through the collision between the gust fronts and the sea-breeze fronts. Decreasing the maximum total heat flux from 700 to 500 W m^-2 weakens each generation of convection. Further decreasing the maximum total heat flux to 300 W m^-2 leads to only one generation of shallow convection.

Convectively generated low-frequency gravity waves had been found to be greatly coupled with the initialization and development of convection. During convection, alternating wavy pattern of updrafts and downdrafts propagating in the troposphere were recorded. Idealized numerical simulations were performed to examine their generation and figure out how thermal and dynamical forcing may play the role. Moist experiments show that latent heating emerges as a nonnegligible contributor to the generation of gravity waves but cannot fully explain the appearance of multiple wave couplets even under a cyclical-like redevelopment. Spectral analyses of the vertical velocity fields identify gravity wave with similar horizontal phase speed varying from the speed of the second-order (19 m s^-1) and the first-order (38 m s^-1) gravity wave modes, but two different spectrum centers that approximately match latent heating and Brunt-Väisälä frequency at the level of neutral buoyancy (LNB), respectively. Dry experiments with prescribed latent heating further prove that the net buoyancy can force convective updrafts to oscillate around the LNB, and thus initiate wave couplets both in the troposphere and lower stratosphere. Sensitivity experiments show that a much higher model lid, or a strong and deep damping layer may exert influence on wave amplitudes through weakening the overshooting updrafts, which means a much weaker effect of the mechanical oscillator mechanism.

The climate of Indonesia located under the equator is predominated by the monsoon of both northern and southern hemispheres. Climate changes in Indonesia would affect not only agricultural production but also 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. In this study, we aim to clarify the future climate change mainly of Java Island. Various types of bias correction (BC) methods combined with the statistical downscaling/spatial disaggregation (SD) method are applied to the output of CMIP5 GCMs. The seasonal change and amount of rainfall derived from CMIP5-GCMs were different from the observed one, but both GSA (Gaussian Scaling Analysis) and CDFDM (Cumulative Distribution. Function-based Downscaling Method) have well captured the seasonal characteristics of the observed climate. Though the future tendencies of precipitation changes (RCP8.5; 2041-2060) are different in each month, generally decreasing in the onset season and increasing in the dry season. There is a general coincidence that precipitation at the onset of the monsoon is likely to decrease in the future, but the trend of precipitation change may differ from that of the GCM itself depending on the BC method.

To assess the flood and drought risk change by global warming, dynamic downscaling was conducted for the Davao River basin, Philippines (7.5 N), and the Solo River basin, Indonesia (7.5S). The Meteorological Research Institute-Atmospheric General Circulation Model (MRI-AGCM) ver. 3.2S (super high resolution) and 3.2H (high resolution), with horizontal resolution of 20 km and 60 km, respectively, were downscaled into 5 km horizontal resolution by WRF model. We faced difficulty in reproducing realistic rainfall phenomena or appearance of rainfall frequency. Both of target regions with 7.5 degrees latitude, north and south, are close to the equator. Therefore, tropical cyclones have rarely generated in those regions. However, downscaling with adopting cumulus parameterization schemes, such as Kain & Fritsch scheme, generated too many tropical cyclones, even the GCM didn’t generate tropical cyclones. When we downscaled without cumulus parameterization schemes with a single frame of 5 km horizontal resolution, we got better representation of tropical cyclone generation as well as the frequency of rainfall appearances. In the Solo River basin, Indonesia, the MRI-AGCM and its downscaled rainfall in wet season is likely to increase in the end of 21st century in RCP8.5 scenario, while CORDEX-SEA downscaling showed decreasing trend. Our downscaled rainfall in the Davao River basin, Philippines, also showed increasing trend in the end of 21st century in RCP8.5 in wet season, whereas CORDEX-SEA downscaling showed decreasing trend. Careful discussion is required to handle this uncertainty and to plan for getting more robust results.

Further downscaling into the 5 km resolution of the CORDEX Southeast Asia (CORDEX-SEA) 25 km resolution simulations has been implemented using the Regional Climate Model version 4.7 (RegCM4.7) over a subdomain covering the Peninsular Malaysia. There CORDEX-SEA simulations that were forced with EC-EARTH, MPI-ESM-MR and HadGEM2-ES from future emission scenarios of RCP4.5 and RCP8.5 were considered. We used the MIT Emanuel cumulus parameterization scheme (CPS) over the land and Kain-Fritsch over the ocean, and the CLM4.5 for land surface scheme were used in the 5 km simulations. Performance analysis indicated added values in the 5km simulations of precipitation. The 5km simulations were successfully able to simulate the detailed east-west contrast of the DJF rainfall, the north-south contrast of SON rainfall. The biases were much reduced in the 5km simulations. The annual cycles from the 5 km simulations were closer to the observations. The superior performances of the 5km simulations may not necessarily due to the resolution but can be contributed schemes. The projected precipitation showed that a drying tendency over the rest of the 21^st century regardless of the seasons. For precipitation extreme indices such as Rx1day, an increase in DJF Rx1day is projected in the early century under RCP4.5 but to decrease gradually for the rest of the 21^st century. For RCP8.5 scenario, the DJF Rx1day was projected to decrease except over the central part of Peninsular Malaysia. For JJA, under both scenarios, a decrease in Rx1day was projected throughout the 21^st century. For consecutive dry days (CDD), both RCP scenarios are projected to increase for both JJA and DJF seasons. These overall drying trends appear consistent with the 25 km simulations. However, despite improvements in the 5km simulations, the projections have no uncertainty component estimation of different regional climate models.

This study used the Non-Hydrostatic Regional Climate Model (NHRCM) developed by the Japan Meteorological Research Institute (MRI) to simulate the rainfall over Malaysia. The resolution of the model was 2km and it was a convective-permitting model. A simulation from September 1979 until October 2003 was carried out to represent the historical period climate. The forcing data used to drive the NHRCM (NHRCM02) was the 5km × 5km downscaled MRI-AGCM3.2 output (NHRCM05). The simulated seasonal rainfall climatology showed that NHRCM02 had a greater success than NHRCM05 in reproducing the east-west and north-south rainfall contrast for DJF and SON season, respectively. The convective permitting NHRCM02 had the advantage over the cumulus parametrization scheme governed NHRCM05 during the seasons where rainfall was active, but not so much when the rainfall was less active, such as MAM and JJA. In addition, for NHRCM02 the rainfall seasonal biases were much smaller than that of NHRCM05, except for DJF over the east coast of PM, where the wet rainfall bias is much stronger than that of NHRCM05. The seasonal rainfall distribution produced by NHRCM02 matched better the observation than that of NHRCM05. This is due to NHRCM02 that has the tendency to produce more heavy rainfall which was greatly being underestimated by NHRCM05. In terms of rainfall annual cycle, both NHRCM simulations were able to capture the signature bimodal and unimodal pattern for both west and east coast of PM respectively. However, the simulations noticeably overestimated the first rainfall peak over the west coast during MAM. Over the east coast, NHRCM02 tended to overestimate the rainfall from December to May, but closely matched that of observation from June till November. For NHRCM05 on the other hand, the simulation generally underestimated the rainfall throughout the year except during January to April.

This study first evaluates the performance of three model experiments in representing rainfall over part of Vietnam and the Lower Mekong Basin for the historical period 1986–2005. The three experiments include the Coupled Model Intercomparison Project Phase 5 (CMIP5) EC-EARTH Global Climate Model (GCM) and two downscaling runs based on a regional climate model at 25km resolution with the GCM forcing (RCM-25km) and at 5km resolution with the RCM-25km forcing (RCM-5km). Verifications against observations show that the experiments generally capture the spatial distribution of climatological rainfall. While the GCM well represents the observed average rainfall cycles, its coarse resolution limits its capability in reproducing extreme rainfall values. The downscaling experiments do not clearly show their advantage in simulating average rainfall but exhibit significant added values when representing extreme rainfall in the study region. The RCM-5km does not outperform its driving 25km experiment in representing the mean and extreme rainfall values, suggesting that having a better resolution may not compensate for having a good model configuration with appropriate physical schemes. Analysis of climate projection for the far future period 2080–2099 under two representative concentration pathways (RCP) scenarios, RCP4.5 and RCP8.5, reveals that the downscaling experiments can modify the change direction of future rainfall obtained with the GCM. While the EC-EARTH GCM generally projects wetter tendencies of up to 50%, the downscaling experiments project a general decrease of down to -50% under both scenarios over the study domain. Regarding extreme rainfall, the annual maximum 1-day rainfall amount (RX1day) is projected to increase for the three experiments. The simple daily intensity index (SDII) future changes follow those of the annual rainfall values.

The study of variability characteristic and mechanism of extreme events in the South Asian Monsoon region under changing climate comprises 3 major activities including i) the analyses of extreme events over the area of Thailand and Southeast Asia in the historical period or 1970 – 2005 as well as the future projection up to the end of the century under two climate change scenarios, RCP4.5 and RCP8.5, ii) the analyses of the standard precipitation index and iii) the analyses of the correlation between the monsoon onset and climate variables as well as the impacts of climate change on monsoon onset, monsoon withdrawal and extreme indices. The high-resolution climate dataset from the downscaling of 3 GCMs of the Coupled Model Intercomparison Project phase 5 (CMIP-5) of Southeast Asia Regional Climate Downscaling (SEACLID)/CORDEX Southeast Asia Project from the historical period to the future projection was applied for the analyses. The results show that the maximum 1-day and 5 days precipitation total tends to increase as well as heavy precipitation day. This reflects the tendency of flash flood from heavy and very heavy precipitation. However, the annual precipitation total tends to decrease reflecting the signal of drought under the future climate change. Under the future climate change scenarios, the northeastern and southern regions tend to have higher drought impacts than other regions of Thailand. The results also show the impacts of future climate change on the Southeast Asia in terms of drought. The area over the peninsula and islands of Southeast Asia will have higher impacts from drought while the flash flood will be lower. The future climate change tends to affect the delay of monsoon onset and early withdrawal. The annual precipitation total tends to decrease with the shorter period of monsoon season.

The impacts of planetary boundary layer (PBL) parameterizations on tropical cyclone (TC) climatology over the Philippine region is investigated using the RegCM4.7. The findings suggest that the University of Washington (UW) scheme in RegCM4.7 reproduced better count and distribution of TC intensity, including more intense TCs, and stronger wind and thermodynamic structures than the Holtslag scheme. Results show that downscaling ERA-Interim to 25-km resolution has improved the number of detected TCs in the RegCM simulations. The UW scheme simulated a TC count (380 TCs) nearest to the observation (376 TCs) with an increased number of moderate (Category 2 and 3) and strong (≥ Category 4) TCs than the Holtslag scheme (343 TCs) and ERA-Interim reanalysis (96 TCs). A composite analysis on the radial cross-section of the simulated winds shows that the UW parameterization generates stronger wind circulations with narrower and elevated maximum tangential winds in comparison with the Holtslag scheme. UW also enhances low-level momentum convergence and heating inside the radius of the maximum wind (RMW). The radial positioning of the strong diabatic heating of UW simulation within the RMW also supports the needed conditions for warmer core formation, and hence higher intensity TCs.

We present the climatology of mesopause temperatures using high- and middle-latitude meteor radars. The daily mesopause temperatures are estimated using ambipolar diffusion coefficient data from the meteor radars at Davis Station (68.6°S, 77.9°E), in Antarctica, Svalbard (78.3°N, 16°E), Tromsø (69.6°N, 19.2°E) in the Arctic, and Mohe (53.5°N, 122.3°E) and Beijing (40.3°N, 116.2°E) in the northern middle latitudes. The seasonal variations in the meteor radar-derived temperatures are in good agreement with the temperatures from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the TIMED satellite. Interhemispheric observations indicate that the mesopause temperatures over the southern and northern polar regions show a clear seasonal asymmetry. The seasonal variations in the Davis Station meteor radar temperatures in the southern polar mesopause are dominated by an annual oscillation (AO) with a relatively weak semiannual oscillation (SAO), which shows a clear minimum during summer and a maximum during winter. The mesopause temperatures in the northern high and middle latitudes observed by the Svalbard, Tromsø, Mohe and Beijing meteor radars mainly show an AO, with a maximum during winter and a minimum during summer. The AO in the northern polar regions is stronger than that in the southern polar regions, while the SAO in the southern polar regions is relatively strong compared to that in the northern polar regions.

All-sky meteor radars have been a widely used technique to investigate the mesosphere and lower thermosphere (MLT) region. In this study, we present a comparison of simultaneous horizontal winds observed by multistatic meteor radar system using the forward scatter and backscatter models. The mesospheric wind using the forward scatter model was observed by a link consisting of a monostatic meteor radar in Mengcheng (116.49 °E, 33.36 °N) and bistatic Changfeng receiver (117.223 °E, 31.982°N), separated by approximately 167 km. The mesospheric wind using backscatter model was observed by two co-located (about 300 m apart) meteor radars in Kunming (25.6°N, 103.8°E), but with different operating frequency. In order to test the performance between the forward and back scatter meteor radars, the meteor echoes are selected according to the arrival time and the location region. Our results demonstrate highly consistency of both monostatic and multistatic meteor radars and the more accurate multistatic results.

Recent studies reported up to a 10 % average decrease of lower stratospheric ozone at ∼ 20 km altitude following solar proton events (SPEs), based on superposed epoch analysis (SEA) of ozonesonde anomalies. Our study uses 49 SPEs that occurred after the launch of Aura MLS (2004–now) and 177 SPEs that occurred in the WACCM-D (Whole Atmosphere Community Climate Model with D-region ion chemistry) simulation period (1989–2012) to evaluate Arctic polar atmospheric ozone changes following SPEs. At the mesospheric altitudes a statistically significant ozone depletion is present. At the lower stratosphere (<25 km), SEA of the satellite dataset provides no solid evidence of any average direct SPE impact on ozone. In the individual case studies, we find only one potential case (January 2005) in which the lower-stratospheric ozone level was significantly decreased after the SPE onset (in both model simulation and MLS observation data). However, similar decreases could not be identified in other SPEs of similar or larger magnitude. We find a very good overall consistency between WACCM-D simulations and MLS observations of SPE-driven ozone anomalies both on average and for the individual cases, including case in January 2005.

MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is an upcoming Swedish satellite mission designed to investigate atmospheric waves in the Mesosphere and lower Thermosphere by imaging variations in O2 atmospheric band airglow emission between 70 and 110 km, as well as structures in Noctilucent clouds (NLC, PMSE). Performing a tomographic analysis of these images, 3D reconstruction of waves can be done, allowing the MATS mission to provide global properties of atmospheric waves in all spatial dimensions. In this talk we study the capabilities of the MATS gravity wave parameter retrieval, by analysing synthetic satellite data composed from HIAMCM (The High Altitude Mechanistic general Circulation Model) output. 

Since 2017 we monitored three major stratospheric smoke events: A record-breaking western Canadian wildfire smoke amount was observed over Europe for more than 5 months in 2017, strong smoke pollution originating from extreme Siberian forest fires in July and August 2019 was observed with lidar over the High Arctic for more than 7 months (aboard the German ice breaker Polarstern during the MOSAiC expedition 2019-2020), and, in 2020 and 2021, we monitored the stratospheric perturbation by smoke with lidar over Punta Arenas, in southern Chile, originating from record-breaking Australian bushfires, for two years. Large amounts of biomass-burning smoke were lifted into the stratosphere and formed 5-15 km thick aerosol layers from the tropopause up to around 20 km and partly even 30 km height. The smoke particles influenced the Earth’s radiative balance, the dynamics of the atmosphere, ozone depletion in the Arctic and Antarctica, and the evolution of cirrus clouds in the upper troposphere via heterogeneous ice nucleation in which aged smoke particles served as ice-nucleating particles. The fact that the Siberian smoke event and the Australian smoke event coincided with record-breaking ozone hole events in both hemispheres motivated us to discuss a potential impact of the smoke particles on the strong ozone depletion. The discussion is based on the overlapping height ranges of the smoke layers, polar stratospheric clouds, and the ozone hole regions. We will discuss our long-term lidar observations of the three major smoke events with focus on the High Arctic and Punta Arenas observations, we will further present ozone profiles measured during the hemispheric spring seasons in 2020 to illuminate the potential impact of smoke on ozone depletion, and finally we will show cases with clear signs of smoke-cirrus interaction in the High Arctic as well as over the southernmost tip of South America.

Ozone pollution has been a major air pollution issue since the mid-20^th century, and it has been affected by a number of factors. Climate change is one of the primary drivers which may modulate the photochemical reaction rate, transport pathways as well as biogenic emissions. It is urgent to understand the regimes in the climate modulation on ozone formation and accumulation. Based on studies over United States and China, we aim to discuss the following questions in this talk. Firstly, the impact of compound extremes, i.e., co-occurrence of heat waves and atmospheric stagnation, on the ozone enhancement. Secondly, the synergic effect of anthropogenic emissions and biogenic emissions, particularly along the reduction of anthropogenic emissions, on ozone concentrations in typical ozone pollution prone regions such as North China. Lastly, the effect of temperature and water vapor on ozone. In particularly, their competing effects are interestingly delineated based on multi-year simulations. The messages delivered are believed to be useful in understanding the mechanism governing the ozone concentrations as well as providing information for policy markers in regard of ozone pollution control.

Tropospheric ozone is an essential atmospheric component as it plays a significant role in influencing radiation equilibrium and ecological health. It is affected not only by anthropogenic activities but also by natural climate variabilities. Here we examine the tropospheric ozone change in China associated with the Eastern Pacific (EP) and Central Pacific (CP) El Niño using satellite observations from 2007 to 2017 and GEOS-Chem simulations from 1980 to 2017. GEOS-Chem simulations reasonably reproduce the satellite-retrieved lower tropospheric ozone (LTO) changes despite a slight underestimation. Results show that El Niño generally exerts negative impacts on LTO concentration in China, except for southeastern China during the pre-CP El Niño autumn and post-EP El Niño summer. The budget analysis further indicates that for both events, LTO changes are dominated by the transport process controlled by circulation patterns and the chemical process influenced by local meteorological anomalies associated with El Niño, especially the solar radiation and relative humidity changes. The differences between EP and CP-induced LTO changes mostly lie in southern China. The different strengths, positions, and duration of western North Pacific anomalous anticyclone (WNPAC) induced by tropical warming are likely responsible for the different EP and CP LTO changes. During the post-EP El Niño summer, the Indian ocean capacitor also plays an important role in controlling LTO changes over southern China.

New particle formation (NPF) induces a sharp increase in ultrafine particle number concentrations and potentially acts as an important source of cloud condensation nuclei (CCN). As the densely populated areas of China, the Yangtze River Delta region shows a high frequency of observed NPF events at the ground level, especially in spring. Although recent observational studies suggested a possible connection between NPF at the higher altitudes and the ground level, the role played by vertical mixing, particularly in the planetary boundary layer (PBL) is not fully understood. We integrate the measurements in Nanjing on 15-20 April 2018, and the NPF-explicit Weather Research and Forecast coupled with chemistry (WRF-Chem) model simulations to explore the effect of vertical mixing on NPF and CCN. Our results indicate that newly formed particles at the PBL top could be transported downward by vertical mixing as the PBL develops. A numerical sensitivity simulation by eliminating aerosol vertical mixing suppresses both the downward transport of particles formed at a higher altitude and the dilution of particles at the ground level. The resulting higher Fuchs surface area at the ground level, together with the lack of downward transport, yields a sharp weakening of NPF strength and delayed start of NPF therein. The vertical mixing, therefore, leads to a more than double increase of surface particle number concentration in the 10-40nm (CN_10-40) and a one-third decrease of the PBL top CN_10-40. The continuous growth of nucleated ultrafine particles at the PBL top is strongly steered by the upward transport of condensable gases, with close to half increase of particle number concentrations in Aitken mode and CCN at a supersaturation rate of 0.75%. The findings may bridge the gap in understanding the complex interaction between PBL dynamics and NPF events, reducing the uncertainty in assessing the climate impact of aerosols.

Sulfate and nitrate formed on dust aerosols can considerably affect particles’ physicochemical properties due to their high hygroscopicity. Dust reverse-transport (DRT) events may occur in eastern China when the trajectory of the dust plume undergoes a distinct turn caused by Asian highs or cyclones, resulting in the re-appearance of the dust plume in the same place but with the altered chemical composition caused by anthropogenic pollutants mixed in. In this study, three DRT events were identified in Qingdao, a coastal city of North China. The secondary sulfate and nitrate in PM_2.5 collected during the DRT events were estimated according to the mass concentration of water-soluble ions and dust tracer metal. Several key factors, including heterogeneous reactions on aerosols, photochemical conversions in the air, and precursors’ abundance in dust plumes, affect the aging of dust plumes. In the presence of adequate ammonium, high-level precursors and oxidants in the air, sulfate and nitrate were efficiently produced under moderate/high humidity conditions during the DRT period. Compared with the first dust arrival stage, the concentration of sulfate and nitrate increased 0.7–3.4 and 6.7–13.2 fold, respectively, in 48 hours since the DRT occurrence. In contrast, when the relative humidity and the molar ratio of [NH₄⁺]/[SO₄²⁻] were low, the growth of sulfate and nitrate was negligible in dust plumes. This study reveals that the efficiency of sulfate and nitrate formation in dust plumes is closely related to the atmospheric properties along the transport pathway.

Biogenic volatile organic compounds (BVOCs), the largest source of VOCs emissions globally, play vital roles in modulating atmospheric chemistry and the formation of ozone and secondary organic aerosol (SOA). A large number of studies have quantified BVOC emissions in the past. However, the source of BVOC emissions in the urban areas, urban green space BVOC (U-BVOC) emissions, is largely neglected due to relatively coarse landcover type data, but also because their important contribution to urban BVOCs was previously unrecognized. In this study, the first BVOC emission inventory emitted by urban green spaces in China was developed based on an ultra-fine landcover dataset at a spatial resolution of 10-m. This U-BVOC emission inventory has a spatial resolution of 27 km, while a high resolution of 1 km is applied in areas with dense U-BVOC emissions, such as the North China Plain, the Yangtze River Delta, and the Pearl River Delta. The new U-BVOC emission inventory shows that nationwide U-BVOC emissions account for only 0.1% of natural BVOC emissions, but they could account for a large fraction of total BVOC emissions in megacities. In particular, the interannual variability in developed regions such as the North China Plain fits well with recent ozone trend changes, emphasizing its potential key role in driving ozone formation. Considering that the U-BVOC emissions emit directly in the core urban area and their high emission intensity, the construction and continuous improvement of the U-BVOC emission inventory may support the understanding of ozone and SOA formation.

The Indian summer monsoon plays a crucial role in India’s agriculture and shapes many other aspects of life affecting the livelihood of a fifth of the world’s population. It is therefore highly relevant to assess its change under potential future climate change. Here, we use 32 of the climate models within the Coupled Model Intercomparison Project Phase 6 (CMIP6) in order to analyze the model projections for the 21^st century with particular focus on the seasonal summer monsoon rainfall, its interannual variability and the occurrence of extremes. All of the models show a substantial increase in June-to-September (JJAS) mean monsoon rainfall under unabated climate change (SSP5-8.5) and most do also for the other three Shared Socioeconomic Pathways analyzed (SSP1-2.6, SSP2-4.5, SSP3-7.0). Moreover, the simulation ensemble indicates a linear dependence of rainfall on global mean temperature with a high agreement between the models independent of the SSP. Most models project that the increase will contribute to the precipitation especially in the Himalaya region and to the northeast of the Bay of Bengal, as well as the west coast of India. Interannual variability is found to be increasing in the higher-warming scenarios by almost all models. Under the shared socioeconomic pathway SSP5-8.5, very wet monsoon seasons as observed in 1 out of 10 years in 1900-1950 are projected to occur in 8 out of 10 years in 2050-2100 on multi-model average. With only 6 out of 10 seasons found to be very wet in 2050-2100 under the SSP2-4.5 scenario, we show that even modest efforts to mitigate climate change can have a strong impact on the frequency of very strong rainfall seasons. The CMIP6 simulations largely confirm the findings from CMIP5 models, but show an increased robustness across models with reduced uncertainties and updated magnitudes towards a stronger increase in monsoon rainfall.

The Indian summer monsoon rainfall (ISMR) is vital for the livelihood of millions of people in the Indian region; droughts caused by monsoon failures often resulted in famines. Large volcanic eruptions have been linked with reductions in ISMR, but the responsible mechanisms remain unclear. Here, using 145-year (1871 – 2016) records of volcanic eruptions and ISMR, we show that ISMR deficits prevail for two years after moderate and large (VEI > 3) tropical volcanic eruptions; this is not the case for extra-tropical eruptions. Moreover, tropical volcanic eruptions strengthen El Niño and weaken La Niña conditions, further enhancing Indian droughts. Using climate-model simulations of the 2011 Nabro volcanic eruption, we show that eruption induced an El Niño like warming in the central Pacific for two consecutive years due to Kelvin wave dissipation triggered by the eruption. This El Niño like warming in the central Pacific led to a precipitation reduction in the Indian region. In addition, solar dimming caused by the volcanic plume in 2011 reduced Indian rainfall.

The spatial and temporal modulation of aerosol species by the monsoon intraseasonal oscillation (MISO) were investigated using the Copernicus Atmosphere Monitoring Service reanalysis data and Moderate Resolution Imaging Spectroradiometer satellite (MODIS) observations from 2003 to 2020. The climatological spatial distribution of aerosol species showed that dust aerosols are dominant over the Arabian Peninsula, East African Himalayan foothills. The predominant aerosols in the Himalayan foothills were organic matter, black carbon, and sulfate. During the MISO, anomalous southwesterly or westerly flow variability was found to be responsible for the transport and spatial distribution of these species. During MISO phases 2 to 5 (the active phase of the Indian summer monsoon), strong southwest monsoon winds transported sea-salt aerosols from the Arabian Sea to the Indian region. In phases 5 to 7, which are associated with the transition from the active to the break phase of the Indian monsoon, dust transport from the Arabian Peninsula and East Africa strengthened. The total aerosols over the Indian subcontinent peaked in phases 6 and 7. Anomalous cyclonic circulation during MISO phases 2–4 over central India controlled the westward movement of organic matter, sulfate, and black carbon along the Himalayan foothills. These dynamic spatial changes in aerosols due to the MISO over the Indian region affected the shortwave and longwave radiation balances, and thus can alter the monsoon circulation.

The Indian Summer Monsoon (ISM) plays an intrinsic role in the global climate system. It is the backbone of India’s economy as it supports the livelihood of the world's one-fifth population. ISM is considered as a giant hydrological cycle associated with several complexities and variabilities of a wide spectrum. Therefore, future changes in ISM are highly relevant for regional socioeconomic assessments. This study highlights the changes in ISM using a suite of the Global Climate Models (CMIP6) by the end of the century. The study also examines the major drivers in controlling these changes, such as mean sea level pressure, low-level jet, and low-level moisture transport. In this regard, the performance of 15 GCMs were analyzed beforehand to get reliability into the future projection, i.e. mid (2041-2070) and far (2071-2100) future under unabated climate change (Share Socioeconomic Pathways; SSP585), respectively. CESM2-WACCM, MIROC6, MPI-ESM1-2HR and NorESM2-MM were found to be the best GCMs that have the ability to capture the mean rainfall over India. All models except CESM2-WACCM shows a substantial increase in mean rainfall over most of the Indian landmass in the mid and far future. The projected strong low-level jet along with enhanced low-level moisture transport towards the region leads to enhanced rainfall over the region. Since ISM plays a vital role in modulating the global climate, it is imperative to analyze the projected changes that can help in better planning and strategies to mitigate the incurred losses.

The interpretation of East Asian monsoon speleothem δ¹⁸O records is heavily debated in the paleoclimate community. Besides developing new speleothem proxies, the use of isotope-enabled climate simulations is one of the key tools to enhance our understanding of speleothem δ¹⁸O records. Here we present results from novel climate simulations performed with the fully coupled isotope-enabled Community Earth System Model (iCESM1.2), which simulates global variations in water isotopes in the atmosphere, land, ocean, and sea ice. The model closely captures the major observed features of the isotopic compositions in precipitation over East Asia for the present-day conditions. To better understand the physical mechanisms causing interannual to orbital timescale variations in δ¹⁸O in East Asian speleothems, we ran a series of experiments with iCESM. We perturbed solar, orbital, bathymetry, ice-sheet. The simulations supporting of observations/reconstructed records from East Asia, help understand the controls on the isotope composition of East Asian monsoon rainfall and how speleothem δ¹⁸O records may be interpreted in terms of climate. The study provides new insights into the mechanisms of East Asian monsoon changes on different timescales.

Understanding the natural variability of Indian summer monsoon (ISM) is a crucial aspect relevant for decadal climate predictions and climate change studies. The multidecadal variability of ISM is known to have a close association with the Atlantic multidecadal oscillations (AMO). Several teleconnection pathways have been suggested to explain the co-variability of the AMO and ISM in multidecadal timescales. One hypothesis is that the AMO modulates the interannual North Atlantic Oscillation (NAO) mode and there by influences the monsoon via Eurasian temperature modulations. Another possibility is the AMO modulating the monsoon via the Pacific pathway through the atmospheric bridge mechanism and associated modulations of the Hadley-Walker circulations. The Last millennial (850-1850) climate simulations part of the PMIP3 gives an opportunity to better understand the fidelity of climate models in capturing the AMO-ISM teleconnection mechanisms. In this study we explore how well the proposed mechanisms are represented in eight global climate models (GCM) LM simulations. Such a study, assessing the validity of different AMO-monsoon teleconnection mechanisms in different model climates provides crucial information about how reliable the respective GCMs may be in making decadal climate predictions.

We use multiple proxies, including pollen, diatom and phytolith assemblages from various archives such as lake sediments, peats and paleosols distributed in different parts of China, to quantitatively and semi-quantitatively reconstruct paleoclimate changes in monsoonal and arid areas over the past ~21 ka. Our data show a significant variability in both monsoonal and arid regions. Comparing with modern observational data between 1961 and 1990, the annual and seasonal temperatures were ~5 ℃ (3-8 ℃) lower during the last glacial maximum, and ~2 ℃ (1-3 ℃) higher during the Holocene optimum; while the annual and seasonal precipitation have 30-150 % variations, with greater seasonality during the middle Holocene at 8-5 ka. A distinct paleoclimate variability was found in transitional zone between the humid monsoon and the dry desert areas. These results generally agree with paleoclimate reconstructions by other independent methods, including temperatures inferred from lacustrine branched glycerol dialkyl glycerol tetraethers (brGDGTs), monsoon intensities based on leaf-wax hydrogen isotopes, as well as monsoon precipitation and paleoenvironment condition derived from carbonate and dolomite contents, stable carbon isotopic composition and environmental magnetism analyses from loess deposits with high-resolution absolute optically stimulated luminescence dating constraints. These quantitative and semi-quantitative paleoclimate reconstructions from different parts of China also show a heterogeneous and notable diversity in regional temperature and precipitation variability, for both annual and seasonal signals. Based on the novel data assimilation method of optimal information extraction (OIE), we find that summer temperature and precipitation during the Current Warm Period in China are not unprecedented over the past ~21 ka, in particular in the monsoonal China, and that changes in summer temperature and precipitation are mainly driven by boreal summer insolation. We do find a conspicuous regional diversity in paleoclimate variations during the past ~21 ka, regarding amplitude, frequency and forcing mechanism.

East Asian monsoon has two important components, East Asian summer monsoon (EASM) and East Asian winter monsoon (EAWM). Studies have found that EASM and EAWM are correlated and have interactions. The relationship between EASM and EAWM at different timescales reveals the corresponding controlling factors of regional climate variabilities in East Asia. At interannual scale, there is a biennial oscillation between the EASM and EAWM variation. A strong EAWM might be followed by a strong EASM, and then a weak winter monsoon which leads to a weak summer monsoon, and a strong winter monsoon, thus forms a quasi-biennial cycle. Such relationship illustrates the basic air-sea-land interactions. At scales from decadal to millennial, the EASM and EAWM are anti-correlated, mainly attributed to the internal variabilities, including e.g., PDO, AMO and AMOC at corresponding scales. These internal variabilities, which we call annual forcings, have prolonged influence from summer to winter climate. At orbital scales, the EASM and EAWM are positively correlated according to the enhanced/weakened seasonality induced by changes of precession and obliquity. The forcings introducing enhanced/weakened seasonality are defined as seasonal forcings. It is worth noting that the topography of icesheet can modify the EASM-EAWM variations at orbital scales, which change from in-phase to out-of-phase after large-scale development of major NH glaciation. We can conclude that EASM and EAWM are anti-correlated when the climate is dominated by annual forcings whereas positively correlated when the climate is dominated by seasonal forcings.

The eastern Asian summer monsoon (EASM) showed obvious multi-scale variability with extreme weakening events during the Holocene, which are of great interests to the broad fields of climatology, geology, and geography.  Besides the recent abundant Holocene paleoclimate archives at relatively high temporal and spatial resolutions, there are also great improvements of the modeling on EASM weakening events during the Holocene. The spatio-temporal characteristics and mechanisms of the multi-scale EASM weakening events, e.g., 4.2ka BP event and decadal megadroughts, have been investigated through two groups of climate modeling (i.e., NNU-Holocene and NNU-2ka) and comparisons between reconstruction and simulations. The results show that, on millennial scale, proxy reconstructions and model simulations revealed significant increases of NHLMP due to the green Sahara during mid-Holocene. on centennial scale, one potential mechanism behind the 4.2ka BP event is the multi-century-scale fluctuations in SSTs across the North Atlantic and AMOC strength, superimposed on the steady decline in SSTs and AMOC led by long-term changes of orbital forcing. On decadal scale, the frequency of EASM weakening events is larger in LIA than MCA, because the EASM weakening are more sensitive to weak PDO phases during LIA. There is also a linear relationship between the SSI intensities and precipitation differences over eastern China between positive PDO and negative PDO phases, which is related to the changes of monsoon circulation and SLP gradient with the SSI intensities. Moreover, the aridification during recent decades over northern China associate with EASM weakening is triggered by phase shifts of PDO and AMO, which could be induced by anthropogenic forcings.

In this study, the data of the last millennium (850~2005) ensemble simulation experiment (CESM-LME) from the Community Earth System Model (CESM) were employed to analyze the synchronization of temperature changes between East Asia and the world over the past millennium on a centennial scale. CESM can provide a reasonable simulation of temperature variation in East Asia. The results from 7 climatic experiments have been analyzed, including all forcing experiment (AF), total solar irradiation experiment (TSI), volcanic eruption experiment (VOL), greenhouse gas experiment (GHG), land use and land cover change experiment (LUCC), orbital elements experiment (ORB), and ozone and aerosols experiment(Oz./Aer.). Moreover, the external reasons for the synchronous change of temperature in East Asia and the world were preliminarily discussed. The results indicate that the temperature change in East Asia during the Medieval Warm Period(MWP) and Little Ice Age(LIA) in the last millennium were approximately consistent with the whole world on the centennial scale, but some differences exist in some centuries. TSI, ORB, and VOL forcings are the main factors for the differences in temperature change between East Asia and the whole world, and some other external forces show a small impact. In the Current Warm Period(CWP), especially in the late 20th century, the temperature changes in East Asia and the world show great asynchrony. The temperature increase in East Asia is less intense than that in the world. Anthropogenic external forcing plays a controlling role in this period. Amplification in climate warming caused by greenhouse gas concentration is found to be obvious in the Earth’s poles, implying the main external reason for the differences in temperature change between East Asia and the world. Meanwhile, Oz./Aer. forcing also causes some impacts.

Thanks to their remarkable development, numerical models have shown high prediction accuracy in short-term rainfall forecasting. On the other hand, in regions where rainfall is closely related to complex meteorological phenomena such as monsoon including tropical regions, there is still a large uncertainty. Deep learning, a powerful statistical method, can learn spatial characteristics and supplement missing values from surrounding data. Applying this method, we propose a method to reproduce rainfall distribution in the tropics from surrounding rainfall information. Using the CMIP6 rainfall dataset, rainfall in regions other than the entire northern region of Thailand is learned from 65 ensembles of global rainfall data, and the model outputs rainfall within the entire northern region. The results showed that the deep learning model tended to overestimate the actual rainfall, but was able to accurately reproduce the rainfall distribution. This method is expected to be applied in practice because of its low computational cost and limited data requirements. It also has the potential to be applied to global regions.

Numerical simulations are the backbone of today's weather forecast and climate projections. Yet due to the ubiquitous turbulence in the atmospheric boundary layer and convective systems, directly resolving all meaningful dynamic scales is prohibiting with current computational capacity. Thus, numerical models run on relatively low-resolution grids and represent sub-grid scale (SGS) processes with parameterization. Traditional turbulence parameterization schemes are built on heuristic assumptions and sometimes tuned without coupling with the dynamic core or other physical parameterizations, therefore in some weather and climate regimes, they exhibit considerable uncertainties and low-fidelity. The development of machine learning (ML) techniques enables the feasibility of data-driven parameterizations, which has been investigated in a lot of studies. Some results suggested that a priori trained ML models perform poorly when they are coupled to dynamic cores and tested. Here we use the evolution of shear instability in a barotropic vorticity equation (BVE) model with a periodic forcing as a prototype problem to develop a model-consistent training strategy, which employs a numerical solver with automatic differentiation and includes it in the loss function. This approach enables the interaction between the dynamic core and the deep learning parameterization during the training phase. Our training set contains only a short period of coarsened high-resolution simulations, but the trained model, given an initial condition long after the training set time, is still able to significantly improve the prediction lead time compared to the low-resolution simulations with or without a Smagorinsky turbulence model. We also investigated the incorporation of attention mechanism and covariance matrix, in our deep learning model to extend the forecast lead time. By conducting transfer learning using a limited number of observations, our model’s performance is further improved. This study demonstrates a potential pathway to use machine learning for enhancing the prediction skills of our climate and weather models.

Surface air maximum temperature over India in the months March to June, the season of heat waves, is predicted using machine learning techniques at a lead time of 10-days (medium-range time scale). Lag correlation between the observed surface air maximum temperature and sea surface temperature as well as soil moisture was used to derive the input attributes for the models. The results indicate the predictions of the Bagging regressor with Multi-layer Perceptron as the base estimator to have higher anomaly correlation skill score along with higher hit rates and lower false alarm rates compared to several other machine learning techniques. The results of the study would be helpful to the society as a whole.

Numerical simulations of a nighttime-generated Tibetan Plateau Vortex (TPV) are conducted using the advanced Weather Research and Forecasting (WRF) model. It is found that the nighttime TPV forms as a result of the merging of convections. Although the WRF model can reproduce the genesis of the nighttime TPV well, colder and drier biases in the lower atmosphere and drier biases in the upper atmosphere are still presented, thus degrading the simulation performance. Inter-comparisons among the experiments indicate that the simulations are more sensitive to land surface schemes than to cloud microphysics schemes. The development of convection is more favorable when daytime surface diabatic heating is vigorous. Surface diabatic heating during daytime plays a dominant role in the development of daytime convection and the genesis of nighttime TPV. Further diagnosis of the PV budget reveals that the obvious increase in PV in the lower atmosphere is associated with the evidently strengthened cyclonic vorticity during TPV genesis. This could be attributed to the increased vertical component of net across-boundary PV fluxes during the merging of convections, as well as the significant positive contribution of diabatic heating effects in the lower atmosphere. Therefore, strong daytime surface diabatic heating, which is essential to convection development, could provide a favorable condition for nighttime TPV genesis. Overall results illuminate the complicated process of TPV genesis. 

We used a High-Resolution Assimilation Dataset of the water-energy cycle in China (HRADC) to study the land-atmosphere interactions and meteorological characteristics in inhomogeneous underlying surface of the Qinghai-Tibet Plateau (QTP). Three different underlying surfaces (i.e., grassland, open shrubland, and barren or sparsely vegetated) of the QTP are selected and the meteorological elements on each underlying surface grid are averaged. We compared and analyzed the Green Vegetation Fraction (GVF), precipitation, soil moisture and soil temperature, and energy fluxes for three different land-use types in QTP. The results showed that the vegetation coverage of HRADC showed a gradual decrease trend from southeast to northwest throughout the Qinghai-Tibet Plateau. The GVF of the grassland in the southeast can reach more than 60% in summer, and only about 20% in sparse vegetation areas. HRADC can well reproduce the seasonal change trend of soil temperature and soil moisture in different underlying surfaces. The annual variation trend of soil temperature shows that the time of the deep soil temperature reaching the peak value lags behind the shallow layer. The annual averaged soil moisture over grassland is higher than that of open shrubland and barren land, which is consistent with the plateau precipitation distribution. The peak value of sensible heat flux over grassland is only 80 W·m^-2 in April, and the latent heat flux can reach 90 W·m^-2, and the net radiation of the barren land can reach 210 W·m^-2 in July. This study is important to discover the water-energy cycle characteristics of QTP.

The dipole pattern of summer precipitation over the Tibetan Plateau (TP) during 1961–2014 is evaluated based on observations and 18 models provided by the Coupled Model Intercomparison Project Phase 6. Of the 18 models, 10 can capture the opposite variation characteristics in the south and north TP. Observational data reveals that the south–north seasaw of TP summer precipitation is essentially driven by a Rossby wave propagating from the Western Europe to East Asia, which is associated with North Atlantic oscillation (NAO). The models successfully simulated the dipole pattern that is closely related to the reproduction of the NAO–TP relationship. Further analysis demonstrates that the reliable simulations of horizontal dynamic processes of moisture transport, which is linked to the NAO–TP relationship, highly contributes to their success in reproducing the dipolar pattern of TP summer precipitation. While unrealistic local vertical circulation and evaporation simulation lead to the failed reproductions. These findings provide significant information for model development and future climate change projections.

Although the frequency and intensity of dust storm event (DSE) have decreased in northern China in recent years, its occurrence and impacts continue, with a more complex formation mechanism under climate change background. Focusing on 7 spring DSEs occurred during 1980-2018 in South Xinjiang, China, this study tries to explain the formation of abnormal atmospheric circulation during the DSE from the perspective of transient eddy fluxes by using the physical decomposition method. The results suggest that 2 days prior to the outbreak of the DSE (“Day -2”), the convergence of transient-momentum transport is beneficial for increasing wind speed to become a jet stream (JS) in the upper level above South Xinjiang. Then, until “Day 0”, wind speed in the mid-high troposphere remains as a JS, with the largest value on “Day -1”. Through downward upper-level momentum, the lower-level wind increases to a maximum value on “Day 0”. Additionally, the direct influence of transient-heat transport convergence and the indirect influence of transient-momentum transport divergence are helpful for the establishment of the Ural ridge under the negative phase of Eurasian (EU) teleconnection pattern, reinforcing the Siberian Highs (SH) and leading to low-level gales. Consistent high winds at the low-high levels and obvious vertical motion (descending from “Day -3” to “Day -1” and ascending from “Day 0” to “Day +2”) result in dust emissions and transport. Thus, the dust column mass density (CMD) begins to concentrate in South Xinjiang on “Day -2” and achieves the strongest on “Day 0”. Although the influence of the transient eddy and the wind speed decrease after the DSE outbreak, atmospheric circulation is also helpful for dust to expand to adjust and downstream regions over the following 4 days.

This work introduces a new framework for identifying the spatial and temporal distribution and magnitude of short-lived climate forcers, and their impacts on air pollution and climate. The approach uses remotely sensed measurements at daily time step and resolutions ranging from kms to tens of kms in connection with a simple mass-conserving first order model of physics and chemistry to quantitatively estimate emissions, in-situ processing, and transport. The approach is self-consistent and has been applied successfully to a few such species. In this work, results from BC, Ozone and Methane will be highlighted. Three important scientific findings include: day-to-day emissions estimates of both means and a robust error quantification, allowing analysis of both source attribution and natural sink potential; overall underestimations of emissions of these species lead to an overevaluation of climate costs associated with CO₂ and air pollution costs associated with PM_2.5; differentiated severe underestimation in some geographic areas at all times and in other geographic areas certain times of the years, coupled with moderate overestimation in some areas all times of the year and other areas during certain times of the years allows for a more nuanced approach to attribution and mitigation. Specific examples demonstrated include vast improvements from coal-fired power plants and steel producing regions, and hidden emissions associated with large-scale biomass plantations. Overall, the idea of simple scaling of existing emissions inventories is shown to not be sufficient to attribution and emissions magnitude quantification, requiring further new collaboration opportunities with both the emissions and mitigation communities. 

Regional transport is one of the major causes of severe haze pollution in the North China Plain (NCP), whereas little is known about its detailed process and its influencing mechanisms. In our study, two regional transport episodes under the two typical synoptic patterns, eastern high-pressure system and cold frontal passage, are investigated by using the WRF-Chem model. Under the eastern high-pressure system, regional transport of pollutants from the south-central area of the NCP could contribute up to 70% of the PM_2.5 concentration to the northern NCP (Beijing-Tianjin-Hebei region). Simultaneously, the pollutants derived from regional transport were located mainly at an altitude of 0.5–1.5 km during the accumulating stage and at 0–3 km during the severely polluted stage, which caused mainly by the height of the inversion layer and the strength of the wind. When cold fronts swept over the NCP region, pollutants led by the regional transport could be lifted to ~3 km along the frontal surface and influence downstream areas. PM_2.5 concentrations near-surface increased temporarily at up to 15 μg·m⁻³·h⁻¹ behind the surface frontal line, owing to the inversion layer triggered by the oblique frontal surface. Cold fronts may also indirectly exacerbate near-surface pollutant diffusion conditions by affecting solar radiation incidence, with a reduction of the 2-m temperature by as much as 1°C, increasing near-surface PM_2.5 concentrations by up to 40 μg·m⁻³. This study emphasizes that the inter-regional cooperation would be essential in improving air quality in the NCP region.

Severe haze occurred in the North China Plain (NCP) from November to December 2015, with a wide spatial range and long duration. In this paper, the combined effect of the anomalous stationary Rossby waves within two westerly jet waveguides on this haze event is investigated based on observational visibility data and NCEP/NCAR reanalysis data. The results show that circulation anomalies in Eurasia caused by the propagation of anomalous stationary Rossby wave energy along two waveguides within the westerly jet originating from the Mediterranean were responsible for haze formation in the NCP. The Rossby waves propagated eastward along the subtropical westerly jet and the polar front jet, causing an anomalous anticyclone over the Sea of Japan and anticyclonic wind shear at 850 hPa over the NCP, which enhanced the anomalous descent in the middle and lower troposphere and subsequently resulted in a stable state of the lower atmosphere. Furthermore, the anomalous stationary Rossby waves propagating along the polar front jet weakened the East Asia trough and Ural ridge and strengthened the anomalous southerly wind at 850 hPa over the coastal areas of eastern China, decelerating the East Asia winter monsoon. The above meteorological conditions modulated haze accumulation in November and December 2015. Meanwhile, continuous rainfall related to ascending motion due to Rossby wave propagation along the waveguide provided by the subtropical westerly jet occurred in southern China. The associated latent heat release acted as a heat source, intensifying the ascending motion over southern China so that the descending motion over the NCP was strengthened, favoring the maintenance of severe haze. This study elucidates the formation and maintenance mechanism of widespread haze in the NCP in late fall and boreal winter.

Online measurements with high time resolution are beneficial to study the atmospheric process of transient pollution events. This study combined the online bulk and single-particle measurements to investigate the biomass burning and firework transition process during the Chinese New Year in Hong Kong from 8^th to 14^th Feb 2013. Single particle aerosol mass spectrometer (SPAMS), a monitor for aerosols in ambient air (MARGA), and sunset OCEC instruments were concurrently deployed to obtain the single-particle and bulk aerosol information. We conducted positive matrix factorization (PMF) to resolve the pollution sources using two different input schemes. Four sources were identified, including Biomass Burning + Fireworks, Secondary Aerosols, Vehicles + Road Dust, and Sea Salt when the input data only contains bulk measurements data. While the PMF result with combined bulk and single-particle datasets can extract the fireworks from the biomass burning and an industry source was additionally obtained. Combustion source (fireworks and biomass burning) is the primary source of particulate matter during the sampling period in this study. We identified two fireworks discharge processes in this study. EP1 (from midnight on the 9^th to 10:00 on the 11^th) was mainly contributed by fresh fireworks, and EP2 (from 21:00 on the 11^th to 00:00 on the 13^th) was contributed primarily by aged fireworks. Overall, the combination of online bulk and single-particle measurement data provides a new perspective for applying source apportionment of aerosols using PMF.

In response to the severe environmental problems, China implemented the Environmental Protection Tax Law in early 2018. Although the tax is levied based on producers, the taxation burden can be transferred to consumers through products’ increasing price. Based on the MRIO model and the official calculation method of environmental tax, our study quantifies the taxation induced by household consumption and the tax intensity of residents from both provincial and city-based perspectives. The national tax revenue due to household consumption is estimated to be 32 billion Yuan in 2012, only one seventh of the related economic loss from premature mortality. Due to China’s regional imbalanced economic development and pollution transfer caused by inter-regional trade, our study reveals that tax intensities in different regions are unmatched with their affluence levels under current environmental tax, which aggravates regional inequalities. We further analyze some scenarios of alternative levy mechanisms. If each province or city imposes taxes to products it consumes (rather than produces, as in the current mechanism), with the tax rate linearly dependent on its per capita consumption expenditure, this would effectively reduce inter-provincial and inter-city inequality. Moreover, if tax revenues could be used to support emission control, such as installing suites of ULE technology in the power and industrial sectors nationally, regional economic inequality would be further alleviated while improving the environment and reducing tax payers’ economic burden.

A deeper knowledge about the spatially coherent patterns of extreme rainfall events in the South and East Asian regions is of utmost importance for substantially improving the forecasts of extreme rainfall as their agro-based economies predominantly rely on the monsoon. In our work, we use a combination of a nonlinear synchronization measure and complex networks to investigate the spatial characteristics of extreme rainfall synchronicity in the Asian Summer Monsoon (ASM) region and gain a comprehensive understanding of the intricate relationship between its Indian and East Asian counterparts. We identify two modes of synchronization between the Indian Summer Monsoon (ISM) and the East Asian Summer Monsoon (EASM) – a southern mode between the Arabian Sea and south-eastern China in June which relates the onset of monsoon in the two locations, and a northern mode between the core ISM zone and northern China which occurs in July. Thereafter, we determine the specific times of high extreme rainfall synchronization, and identify the distinctively different large-scale atmospheric circulation, convection and moisture transport patterns associated with each mode. Furthermore, we discover that the intraseasonal variability of the ISM-EASM interconnection may be influenced by the different modes of the tropical intraseasonal oscillation (ISO). Our findings show that certain phases of the Madden-Julian oscillation and the boreal summer ISO favour the synchronization of extreme rainfall events in the June-July-August season between ISM and EASM. This work is funded by the CAFE project which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 813844.

The East Asian Winter Monsoon (EAWM) is the strongest in its intensity among global winter monsoon system. Many studies have recognized the thermal and mechanical forcing of Tibetan Plateau (TP) can be one on the most important forcing for that. However, quantification of physical mechanism generating climatological circulation pattern of the EAWM has not been fully understood. In this study, based on the general circulation model simulations, the relative contributions of thermal and mechanical effect of orography, and land-sea thermal contrast in generating the zonal asymmetric sea level pressure pattern of EAWM are examined. The experiment with idealized Eurasian continent (EU), TP, Mongolian Plateau (MP) and North American continent and Rocky Mountain provides a decent simulation of the sea level pressure pattern. Sensitivity experiments are designed by applying and withdrawing factors of the possible total forcings. As a results, Land-sea thermal contrast explain most (responsible for ~70%) of the Siberian High (SH) intensity and its center location, with mechanical effect of orographic forcings (accounts for ~29%) playing a secondary role, and thermal effect of orographic forcing (~1%) play only minor role. On the other hand, mechanical effect of orographic forcings (~47%) play major role on the Aleutian Low (AL) intensity and its center location, land-sea thermal contrast (~18%) do not have high influence as for SH, and thermal effect of orographic forcing (~1%) playing minor role as SH. Results of this study suggest that EU with TP and MP is important in forming SH and AL coincide with its climatological intensity and center location. It appears that the mechanical effect (mountain drag effect, mountain uplift effect, and mountain horizontal deflection effect) of TP and MP located in the EU can be the reason why the EAWM is strongest among global winter monsoon system.

The puzzle of recent global warming trend slowdown has captured enough attention, though the underlying cause is still unexplained. This study addresses that area segregating the role of natural factors (the sun and volcano) to that from CO2 led linear anthropogenic contributions. It separates out a period 1976–1996 that covers two full solar cycles, where two explosive volcanos erupted during active phases of strong solar cycles. The similar period also matched the duration of abrupt global warming. It identifies that dominance of Central Pacific (CP) ENSO and associated water vapor feedback during that period play an important role. The possible mechanism could be initiated via a preferential alignment of NAO phase, generated by explosive volcanos. Inciting extratropical Rossby wave to influence the Aleutian Low, it has a modulating effect on CP ENSO. Disruption of Indian Summer Monsoon and ENSO during the abrupt warming period and a subsequent recovery thereafter can be explained from that angle. Interestingly, CMIP5 model ensemble, and also individual models, fails to comply with such observation. It also explores possible areas where models miss important contributions due to natural drivers.

Precipitation is one of the most essential parameters in the Earth system. Especially, the Asian monsoon brings abundant precipitation to densely inhabited regions, and can be a significant water resource for daily human activities. The seasonal precipitation variations over the Asian monsoon region can be the most characteristic worldwide. Not only variations in the amount of precipitation but also changes in precipitation characteristics can be of great concern in terms of intensifying floods and droughts under climate change. This study focuses on the microphysical properties of precipitation which has not yet been addressed in terms of statistical aspects and aims to investigate the climatological characteristics of precipitation microphysical structures over the Asian monsoon region by using eight years of Dual-frequency Precipitation Radar abord Global Precipitation Measurement Mission Core Observatory (GPM/DPR). Precipitation rate, mass-weighted mean diameter (Dm), precipitation top height, frequency of heavy ice precipitation etc. were statistically analyzed in this study. It was confirmed that eight years of accumulated precipitation dataset by GPM/DPR can be used to detect differences in precipitation characteristics between pre-monsoon and monsoon seasons. We found that Dm was larger, and the land-ocean contrast was clearer in the pre-monsoon than in the monsoon season. The region and season with large Dm were consistent with the regions where deep convective core was dominant as explained in previous studies. The results were consistent with that precipitation top height was higher in the region and season with large Dm. It is known that precipitation amount is less but there are more active lightning and deep convections in pre-monsoon season. We investigated frequency of the existence of heavy ice precipitation by GPM/DPR. The results showed that frequency of heavy ice precipitation was larger over land in pre-monsoon season, which can be related to the results of large Dm. 

The impact of the South China Sea summer monsoon (SCSSM) on the Indian Ocean dipole (IOD) has been systematically investigated in observations. This study focuses on the ability of climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) to reproduce the observed relationship between the SCSSM and IOD, and the relevant physical mechanisms. All 23 models reproduce significant correlations between the SCSSM and IOD during boreal summer (June–July–August, JJA), whereas the influence of the SCSSM on the IOD varies considerably across the CMIP5 models. To explore the causes, all models are divided into two groups. Models that successfully simulated both the correlations between the SCSSM and JJA IOD and of the SCSSM and JJA IOD with precipitation over the western North Pacific and Maritime Continent are classified as Type-I, and these produce stronger low-level wind anomalies over the tropical southeastern Indian Ocean. The stronger low-level wind anomalies enhance local sea surface temperature (SST) anomalies via positive wind–evaporation–SST (WES) and wind–thermocline–SST (Bjerknes) feedbacks. This corresponds to a strengthening of IOD events due to the increased zonal gradient of SST anomalies over the tropical Indian Ocean. In contrast, Type-II models perform poorly in representing the relationship between the SCSSM and JJA IOD or relevant atmospheric bridges, corresponding to weaker WES and Bjerknes feedbacks, and produce weaker IOD events. These results demonstrate that the better the model simulation of the atmospheric bridge, the larger contribution of the SCSSM to the IOD.

Trends and tele-connections in the summer monsoon rainfall over South and East Asia are examined. Trend analysis indicates that over South Asia one contiguous region over northern part India exhibits a significant decreasing trend and another region over the southern part of India exhibits a significant increasing trend during summer (June through September). However over East Asia two regions one over the Korea-Japan peninsula and another over South China indicate a significant increasing trend. These trends are evident post 1970s. Outputs from the Coupled Model Inter-comparison Project are investigated using historical simulations and future projections. In spite of large spread among the models, future projections in the summer monsoon rainfall over South as well as East Asia indicate a multi-decadal variability, displaying certain epochs of more rainfall over South Asia than over East Asia and vice versa. Tele-connections between the South and East Asian monsoon rainfall also exhibits a multi-decadal variability with alternate epochs of strengthening and weakening relationship. Thus, in general an out-of-phase relation between these two large monsoon systems is indicated, however the recent Monsoon 2020 witnessed heavy rains over South Asia and devastating heavy rains over East Asia. Possible reasons for such an in-phase relation during Monsoon 2020 will be suggested.

Insolation changes play an important role in driving monsoon changes at orbital time scales. One key issue that has remained outstanding is whether the Asian monsoon is driven by local insolation from the Northern Hemisphere (NH) or remote insolation from the Southern Hemisphere (SH) at orbital band. Here, we perform a set of sensitivity experiments to quantify the impacts of local and remote insolation changes on the Afro-Asian summer monsoon at 11ka B.P relative to the present. We show that the Afro-Asian summer monsoon is overwhelmingly driven by the precession induced local insolation change in the tropical-subtropical NH. The insolation from NH high latitudes also affects the Afro-Asian summer monsoon. In contrast, the insolation from SH plays a negligible role. Our model experiments support the idea that the Afro-Asian summer monsoons are driven predominantly by the direct forcing of NH low latitudes summer insolation for the Holocene.

With the expansion of the impact of extreme climate on the economy, environment and human life, extreme climate has received increasing attention in current climate change research. Based on the Holocene (NNU_Holocene) temperature data and atmospheric circulation data from Nanjing Normal University, the spatiotemporal characteristics and attributions of the extreme high temperatures in summer in Asia are analyzed, and the physical mechanism of the spatiotemporal characteristics is further discussed. The results of the characteristics of temporal and spatial variation show that the extreme high temperature in Asia in summer during the Holocene has consistent spatial characteristics and 600-year periodic oscillations. The attribution results show that volcanic forcing has a significant impact on the temporal and spatial characteristics of the extreme high temperature in Asian summer during the Holocene. Analyses of these physical mechanisms show the high pressure of the Asian summer geopotential height field and the sinking motion of the vertical velocity field are conducive to the increase of temperature. At the same time, we found that the decrease in water vapor transport caused by the weakening of the Asian summer monsoon will cause a decrease in cloud cover and an increase in the downward solar radiation flux, thus leading to an increase in temperature. In addition, we found that the 600-year cyclical oscillation of the extreme summer heat in Asia is related to the 600-year cyclical oscillation of AMO.

Solar activity has been suggested to affect Asian summer monsoon (ASM) at various time scales. However, it remains unknown if and how solar activity can influence ASM on a multi-centennial time scale. Using a solar-forced Holocene transient simulation with the Community Earth System Model (CESM), we show that during the middle‒late Holocene ASM precipitation exhibits a significant 300‒600-year periodicity under solar forcing. This model-produced multi-centennial variation is also suggested by high-resolution proxy data. The leading mode of the multi-centennial ASM variation shows a “wet tropics–dry subtropics” pattern, which lags the corresponding solar activity by about a quarter cycle. We find that the key circulation system responsible for the multi-centennial ASM variation is an anomalous western North Pacific (WNP) cyclone, which enhances the climatological south Asia‒WNP monsoon trough. We suggest that solar activity modulates the zonal SST gradients of the tropical Pacific, inducing the anomalous WNP cyclone and enhancing ASM precipitation in a delayed mode. These findings have implications for predicting the influence of the anticipated future solar activity on the Asian monsoon system.

Global monsoon (GM) precipitation has profound impacts on water resources, food security, and the livelihood of about two-thirds of the world's population. Understanding the contrasting changes of GM precipitation (GMP) during the 8.2 ka cold event and the present-day warm event helps better comprehend the common origin of the GMP change and its future projection. We analyzed a suite of transient climate evolutions (TraCE-21 ka simulation). We show that the simulated monsoon rainfall changes during the 8.2 ka abrupt cooling event are qualitatively consistent with the paleoclimate archive collected worldwide. The simulated Northern Hemisphere monsoon (NHM) precipitation significantly decreased by 12.4% per one degree of global mean temperature change (12.4%/°C) while the Southern Hemisphere monsoon (SHM) precipitation increased by 4.2%/°C. The cooling-induced suppressed upward motion plays a dominant role in reducing NHM precipitation, and the reduced moisture adds to the circulation effect, whereas the enhanced SHM precipitation is mainly due to the moisture increase. In the 8.2 ka event, the circulation response reinforces the moisture-induced drought over the NHM region, resulting in an excessive precipitation sensitivity to temperature change (12.4%/°C). In contrast, during the present warm period, the greenhouse warming-induced moisture and circulation effects cancel each other, resulting in a moderate sensitivity (1.8%/°C). Although meltwater and greenhouse gas forcings induce contrasting global temperature change patterns, the GMP changes are governed by common root causes: forced NH-SH thermal contrast, land-ocean thermal contrast, and the tropical SST gradients. The moisture change plays a crucial role in altering precipitation amount but not spatial distribution. We suggest that the external forcing-induced warming (cooling) pattern drives the circulation changes (dynamic effects), determining the spatial structure of the monsoon rainfall change in the past, present, and future.

AMOC is one of the most important poleward heat conveyor belt in the ocean, which has profound impacts on regional climate as well as marine ecosystems. Volcanic eruption, as one of the strongest external forcings, have different impacts on AMOC at different time scales. Previous studies pointed out that the cooling of LIA is associated with weakening of AMOC on centennial time scale, which may be caused by successive volcanic eruptions. However, the timing of the onset and termination of LIA is still under debate. What is the attribution of consecutive volcanic eruption on LIA? Does the volcanic eruption play a role in triggering, maintaining or terminating LIA through AMOC? And what are the mechanisms behind the phase transition of AMOC at decadal and centennial timescales is still unclear.     In this work, based on simulations of CESM-LME as well as an energy balanced model, we explored the impacts of 4 consecutive volcanic eruptions in the past millennium on AMOC at different time scales, and studied their contributions to the onset, maintaining and ending of the LIA. The mechanisms behind the phase transitions of AMOC at different time scales after volcanism are also investigated. Our findings show that the 4 successive volcanic eruptions enhanced AMOC firstly on decadal time scales, and then weakened it centennially. The durations of positive and negative AMOC phases induced by volcanism overwhelm that originating from internal variability. We also found out that the four consecutive volcanic eruptions led to a stepped decline of temperature during the LIA through the long time weakening of the AMOC. This also explained the onset and maintaining of the LIA. Finally, the recovery of AMOC at the end of the LIA is related to the increases of Green House Gases, which plays a pivotal role in the ending of the LIA.

A reliable projection of future decadal precipitation is crucial for large population and social development in eastern China. However, large uncertainties (e.g., model bias, and internal variability) in now available model simulations cause unreliable future projection of decadal precipitation. Using a 90-member ensemble of simulations from Community Earth System Model Large Ensemble Project (CESM2-LE), we find that internal variability contributes most of decadal precipitation variability with 70% to 80% contribution of uncertainties, leads to large uncertainties in future projection of simulations. We further confirm that the interdecadal Pacific oscillation (IPO) can constrain the 30% to 40% internal variability of uncertainties effectively in projections. The length and magnitude of a future megadrought over the eastern China can be accurate estimated by fixing a certain IPO phase. Our results demonstrate that the uncertainties in projections of the decadal precipitation over eastern China can be reduced by improving prediction of IPO and other internal modes of climate variability.

Understanding the decadal variability of land monsoon rainfall in the northern hemisphere (NHLMR) over the past millennium is crucial to the global water cycle and economic development of monsoon countries. However, due to the limitation of time and space scale of observation and reconstruction data, previous studies on the decadal variability of NHLMR over the past millennium are relatively few. In this paper, based on the Community Earth System Model (CESM) climate simulation experiment for the past millennium and the validation of the CCSM4 and FGOALS-s2 experiment and reconstruction data of Paleoclimate Modelling Intercomparison Project Phase III(PMIP3), the characteristics and mechanism of the decadal variability of NHLMR in the past millennium are investigated. The results show that the extended El Niño–Southern Oscillation (XEN) sea surface temperature (SST) index has remained stable in the past millennium, which is mainly controlled by the internal variability of the climate system. The North Atlantic–south Indian Ocean dipole (NAID) sea surface temperature (SST) index shows an unstable state, with an obvious trend of fluctuation near 1212 and 1740. By comparing the single factor sensitivity experiments, it is found that the NAID index in the volcanic experiment shows the same characteristics around 1212 and 1740, which is consistent with the volcanic reconstruction records. Therefore, it is believed that the volcano is an important factor causing the change of NAID and controlling the decadal variation of NHLMR.

Climate change and global warming have become important issues because the continuing increased greenhouse gas concentrations (GHGs). Beside the anthropogenic activities such as energy generation and transportation that emit GHGs, agricultural activity is also believed to be a potential GHG source especially for N₂O due to the overfertilization. The chemical fertilizers may stimulate the soil microbial activities and facilitate the nitrifying and denitrifying processes in the farmland and release N₂O as intermediate product to the atmosphere. This study investigated the temporal changes of soil nitrifiers and denitrifiers after the chemical fertilizers were applied in paddy and dry fields. Triplicate soil samples were collected daily from an 1 ha farmland and determined the changes of soil microbial communities through next generation sequencing for 7 consecutive days after base and top dressing fertilizers were applied. In addition, continuous N₂O fluxes were monitored in situ during the study period. The results showed that both nitrifier and denitrifier populations were similar in the paddy and dry field soils while the compositions of denitrifiers were largely different. Hydrogenophaga sp. and Thiobacillus sp. appeared to be the two most dominant genera in the paddy soils after the chemical fertilizers were applied while Bradyrhizobium sp. and Luteimonas sp. were the two genera that observed in the dry field soils. As both Bradyrhizobium sp. and Luteimonas sp. have in-complete denitrification pathways with the end product of N₂O, the observed N₂O fluxes were also higher in the dry field than the paddy field.

Estuaries are one of the most productive ecosystems and their productivity is maintained by resident microbial communities. Recent changes in climate change further have escalated these stressors leading to the propagation of traits such as antibiotic resistance and heavy metal resistance in microbial communities. Surface water samples from eleven stations along Thakuran and Matla estuaries of the Sundarbans Biosphere Reserve (SBR) of Sundarbans mangrove located in South Asia were sampled in pre-monsoon (June) 2019 to elucidate resident microbial communities based on Nanopore sequencing. Metagenomic analyses revealed the widespread dominance of Proteobacteria across all the stations along with a high abundance of Firmicutes. Other phyla, including Euryarchaeota, Thaumarchaeota, Actinobacteria, Bacteroidetes and Cyanobacteria showed site-specific trends inabundance. Further taxonomic affiliations showed Gammaproteobacteria and Alphaproteobacteria to be dominant classes with high abundances of Bacilli in SBR_Stn58 and SBR_Stn113. Among the eukaryotic communities, the most abundant classes included Prasinophyceae, Saccharyomycetes and Sardariomycetes. Functional annotation showed metabolic activities such as carbohydrate, amino acid, nitrogen and phosphorus metabolism to be uniformly distributed across all the studied stations. Pathways such as stress response, sulphur metabolism and motility associated genes appeared in low abundances in SBR. Functional traits such as antibiotic resistance showed overwhelming dominance of genes involved in multidrug resistance along with widespread resistance towards commonly used antibiotics including Tetracycline, glycopeptide and aminoglycoside. Metal resistance genes including arsenic, nickel and copper were found in comparable abundances across the studied stations. The prevalence of ARGs and MRG might indicate presence of pollutants and hint toward deteriorating ecosystem health status of Sundarbans mangrove. 

In 2013, a category 5 five very severe cyclonic storm ‘Phailin’ hit part of the East coast of India including Chilika, the largest coastal lagoon of Asia facing the north west coastal Bay of Bengal. A study was undertaken in Chilika lagoon to test the hypothesis if benthic faunal communities respond and recover from the impacts of a major cyclonic storm 'Phailin' and implications in terms of carbon parameters. In situ environmental parameters namely salinity, surface water temperature, transparency, dissolved oxygen were measured from surface water and sediment water interface bottom water overlaying the sediment representing 14 stations of Chilika lagoon before cyclone, immediately after cyclone and recovery period. Besides, dissolved nutrients (nitrate, ammonia, o-phosphate and silicate) concentrations were measured for surface water and sediment-water interface. Benthic macrofaunal and meiofaunal community structures were deduced from collected sediments representing the study period from all the stations. Additionally, sediment grain size and total organic carbon (TOC) content of sediment representing the above stations were analyzed. Measured environmental variables such as salinity, water transparency, dissolved nitrate and dissolved o-phosphate values dramatically decreased immediately after the cyclone compared to before cyclone months and subsequently during recovery period the values reached to before cyclone months. On the other hand, TOC concentrations of sediment compared to before cyclone and subsequently reached value found before the cyclone whereas TOC concentrations of sediment steadily increased throughout study period. The abundance of benthic fauna (macro and meiofauna) showed significant decrease but there was only minor changes observed at the species level immediately after the cyclone but eventually there was improvement in terms of an increase in abundance and diversity during recovery period. The observed high TOC could have implications in terms of persistent of hypoxia in sediment and resulting impacts on benthic production.

Consumption of water containing high F^- levels may cause health problems such as dental fluorosis and skeletal fluorosis. High fluoride (F^-) concentration in groundwater and spring has been reported more than 20 years in Aso caldera, Kumamoto, Japan, where they are the main water resources for public water supply. In this study, to understand F^- concentration in recent years and the controlling factors, water samples were collected at two artesian wells and 22 springs. Five of the 24 (20 %) sampling sites showed a mean F^- concentration above the Japanese drinking water standard of 0.8 mg/L. Water samples were classified into Ca-HCO₃, Ca-SO₄-HCO₃ or Ca-SO₄ types. High fluoride water samples showed Ca-SO₄-HCO₃ or Ca-SO₄ types. These water samples evaluated as having an effect of hydrothermal water, based on a higher SO₄^2- concentration or lower Cl^-:SO₄^2- molar ratio. Magmatic gases, including SO₂, HF, and HCl, were considered to form hydrothermal water in the study area, and the effect of hydrothermal water could increase F^-, SO₄^2-, and Cl^- in water samples. The positive correlations between F^- and SO₄^2- and Cl^- indicates this process.

The present study investigated the physicochemical and metal concentrations in water samples collected from Pasur River, Bangladesh. Mongla seaport stands on the bank of this river. Many industries and other commercial sectors situated in this port area are discharging their wastes into the river without proper treatment. The concentration range of TSS, chloride, iron (Fe), and manganese (Mn) were from 363.2 to 1482.7, 108.2 to 708.93, 1.13 to 2.75, and 0.19 to 1.41 mg/L, significantly exceeding the health-based guideline of WHO and Bangladesh (DoE) standards. The average pH value was 8.73, higher than the WHO and DoE standard limit. The water quality evaluation indices such as Metal Index (MI), Comprehensive Pollution Index (CPI), and Water Quality Index (WQI) were used to determine the pollution levels of the Pasur River. WQI (ranging from 391.3 to 1336.1), CPI (6.71 to 23.13), and MI (7.23 to 23.27) were very high and greatly exceeded standard limits indicating that the Pasur River water is highly polluted. The results of Pearson correlation analysis, principal component analysis (PCA), and cluster analysis (CA) indicated that the sources of pollutants were both geogenic and anthropogenic. The spatial distribution of quality indices and cluster groups indicates that the studied river’s urban and seaport areas were more contaminated. The primary anthropogenic sources are municipal wastewater, industrial effluents, runoff from the agricultural area, local Bazar, car garage wastes, highway, and stormwater runoff.

Monitoring of water temperature distribution is important in water quality management in reservoirs. We propose a method to obtain the spatiotemporal variation of surface water temperature using thermal images. In this study, thermal images acquired from satellite (LANDSAT8) and UAV (Mavic Enterprise Dual) were used to measure the surface water temperature distribution in a reservoir. The digital processing of these images was automated by Python codes with OpenCV and QGIS. In the analysis of the satellite images, we analyzed not only the images of infrared waves and visible lights, but also chlorophyll-a concentration by band synthesis. On the other hand, for the UAV images, we have developed a technique to create a synthesized thermal image from individual thermal images using the information of feature matching and Exif data from visible images. In addition, to confirm the accuracy, the estimated temperature from satellite and UAV images were compared with in-situ and laboratory data, respectively. According to the satellite results, it was possible to detect the seasonal change in temperature distribution over the entire surface, and to observe a correlation between the chlorophyll-a concentration and the temperature distribution. From the results by UAV, it was possible to capture the local temperature variation, and it was confirmed that the water temperature increased especially near the river inlet where phytoplankton concentration was relatively high. The study concludes that thermal imaging techniques are effective tool as a method to monitor the surface water temperature in water area where temperature changes spatiotemporally, and the sensor mounted on UAV is particularly effective to grasp the temperature changes in local areas such as river inlet.

The world’s longest trans-basin water diversion project, the Middle-Route (MR) of the South-to-North Water Diversion Project of China (SNWDPC), has officially been in operation for over 7 years. Its water quality status has always attracted special attention because it is related to the health and safety of more than 58 million people and the integrity of an ecosystem covering more than 155,000 km². This study presented and analysed the spatio-temporal variations and trends of 16 water quality parameters, including pH, water temperature (WT), dissolved oxygen (DO), permanganate index (PI), five-day biochemical oxygen demand (BOD₅), fecal coliform (F. coli), total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH_3-N), sulphate (SO4^2-), fluoride (F^-), mercury (Hg), arsenic (As), selenium (Se), copper (Cu), and zinc (Zn), which were determined monthly from samples collected at 27 water quality monitoring stations in the MR of the SNWDPC from March 2016 to February 2019. The water quality index (WQI) was used to evaluate the seasonal and spatial water quality changes during the monitoring period, and a new WQI_min model consisting of five crucial parameters was built. The results demonstrated that the water quality status of the MR of the SNWDPC has been steadily maintained at an “excellent” level during the monitoring period, with an overall average WQI value of 90.39 and twelve seasonal mean WQI values ranging from 87.67 to 91.82. The proposed WQI_min model that uses the selected five key parameters and the weights of those parameters has exhibited excellent performance in the water quality assessment of the project, showing that the proposed WQI_min model is a useful and efficient tool to evaluate and manage the water quality. For the management department, the risk sources near certain stations with abnormally high values should be carefully inspected and strictly managed to maintain excellent water quality. 

The Mt. Gwanak basin was abruptly urbanized when Seoul National University was transferred in 1975. Excessive building construction and road pavement increased the impervious surface, which increased the risk of downstream flooding and water pollution. However, quantitative analysis research on the water cycle distortion was relatively less conducted compared to the research on the realized policies and countermeasures. Therefore, this study aims to quantify water balance components over time and space to analyze the extent of water cycle distortion and suggest directions for improvements. First, the meteorological observation equipment ATMOS-41 was installed to collect hydrological components at time intervals. When compared to the KMA (Korea Meteorological Administration) data, the correlation coefficient showed a great accuracy of 0.98 for both temperature and precipitation. Then, the surface runoff, infiltration, and evaporation were simulated using the SWMM (Storm Wastewater Management Model), a distributed model specialized in simulating the flow rate of urban watersheds. The degree of distortion over time was identified by comparing the past and present water balance ratio by the difference of impermeability. As a result of quantitative analysis over space, the surface runoff of the sub-watershed containing the storage facility was simulated to be higher than the average runoff of the watershed. The SWMM results were verified against previous study results in the target basin. The simulation outputs were also applied to calculate the maintenance flow when restoring waterways to sites with significant surface runoff. The results from this study contribute to the recovery of Seoul National University's water cycle, which ultimately turn out to be a sustainable and eco-friendly campus.

Groundwater pollution by nitrate is a severe problem in Shimabara Peninsula, Nagasaki Prefecture, Japan. Our previous study evaluated the water quality characteristics in the northern part of the peninsula and clarified the spread of groundwater nitrate pollution. This study aims to investigate groundwater quality status in the Southern part of the peninsula and investigate the water quality characteristics in the whole peninsula. Water samples were collected at 56 sampling points in Minamishimabara City from 28 July to 4 August 2021. The spatial distribution of water chemistry was assessed by describing a trilinear diagram and Stiff patterns using major ions concentrations. Only one location in the agricultural area, the western part of the city, exceeded Japanese environmental standards. According to the trilinear diagram, 44 sites (78.6%) were classified as alkaline earth carbonate type, nine sites (16.1%) as alkaline earth non-carbonate type, and three sites (5.3%) as alkaline carbonate type. The Stiff patterns show Ca-HCO₃ type in most of the sites, and Na-HCO₃ type and Mg-HCO₃ type were found in the specific location of the coastal area. The results of the principal component analysis show that the first principal component is the dissolved constituents in groundwater, the second principal component is the effect of geological structure and ion exchange, and the third principal component is the effect of nitrate pollution. As a result of the hierarchical cluster analysis, the water quality in Minamishimabara City was classified into five groups. The first group has relatively higher nitrate concentrations. The second group has relatively high ion concentrations, distributed at lower altitudes. The third group has relatively low ion concentrations, distributed at higher altitudes. The fourth group has predominant concentrations of sodium and bicarbonate ions. The fifth group relates to sea water-affected samples.

The multi-channel collaborative algorithm (MCCA) was developed based on a two-component version of the omega-tau model, which utilizes the information from collaborative channels, that expressed as an analytical form of brightness temperature at the core channel to rule out parameters to be retrieved. In this study, we implemented the MCCA with data from the Soil Moisture Active Passive (SMAP) mission. The MCCA does not require any auxiliary data on vegetation or soil moisture to constrain the retrieval process but uses an information-based technology to obtain the effective single scattering albedo pixel-wisely at a global scale. Initial Results showed that the MCCA has a comparable performance with SMAP DCA (dual-channel algorithm) and outperforms the SMAP SCA (single-channel algorithm) over selected sites. It is worth to note that the MCCA generates vegetation optical depth at both vertical and horizontal polarization, which may improve the understanding of the water-transport process in the soil-vegetation continuum.

Partitioning of evapotranspiration(ET) into its components (ET; the sum of vegetation transpiration [T] and soil evaporation [E])from urban forest land is important for guiding precise irrigation decisions in urban areas and assessing the impact of urbanization on the urban hydrological cycle. So far, the variability of T/ET in natural ecosystems has been extensively discussed, few studies have examined under urban. In this study, high frequency (10 Hz) time series eddy covariance observations collected from January 2020 to December 2021 in an urban forest land located in Tianjin, China. We observed changes in water vapor and carbon dioxide fluxes and the flux variance similarity (FVS) theory based on five water use efficiency(WUE) algorithms was applied to partition ET into E and T. We also combined with oxygen and hydrogen isotopes to verifies the partition results. The results indicated that the partitioning was partially consistent with the isotope-based approach. The growing season average T/ET ranges from 0.68 to 0.96, which can be described well as a function of leaf area index (LAI). Finally, we further discussed the characteristics, uncertainties and applicability of five WUE algorithms in urban forest land.

The Yarlung Zangbo Grand Canyon region in the southeastern Tibet Plateau is a key region for water vapour transfer on the plateau and has an important position in the process of the Plateau water circulation. By using the ECMWF Re-Analyses version5 data, the water vapor transport types are categorized over the Yarlung Zangbo Grand Canyon area. The daily variation characteristics of land-atmospheric water & heat exchanges fluxes are analyzed at different locations under different water vapor conditions by choosing two observation stations in the Yarlung Zangbo Grand Canyon area, namely, the Pailong Station and the Motuo Station, and the results of the simulation of the energy fluxes between the Grand Canyon and the atmosphere by the Community Land Model version 5.0 under seven thermal roughness characterization schemes. The results show that the daily variation of near-surface latent heat fluxes at the two stations during the dry/wet period under typical sunny/overcast skies is more sensitive to atmospheric water vapour conditions and the response is consistent, and the daily variation of latent heat fluxes under strong water vapour conditions is stronger than that under weak water vapour conditions. CLM5.0 significantly overestimates the near-surface sensible heat flux and simulates the near-surface latent heat flux better, with the simulated mean of the sensible heat flux at the Motuo station being 2.39 times the measured mean, with a root mean square error of 117.014 W∙m^-2. The thermal roughness characterization schemes suitable for the Yarlung Zangbo Grand Canyon region was preferably selected to improve the simulation capability of CLM5.0 for the sensible heat flux in the region, and the mean value of the sensible heat flux simulation at the Motuo station was reduced to 1.14 times the measured mean value, with a root mean square error of only 24.502 W∙m^-2. 

The Source Region of the Yellow River (SRYR) is the main runoff producing area and important water conservation area of the Yellow River Basin. It is of great significance for understanding the land surface process and regional water cycle characteristics and revealing the impact of land surface on hydrological process to explore the land surface hydrological process over the SRYR. Based on the Global Land Data Assimilation System (GLDAS), the China Meteorological Forcing Dataset (CMFD) and the station observed precipitation data from 2009 to 2018, the applicability of the Weather Research and Forecasting Model Hydrological modeling system (WRF-Hydro v5.1.1) over the SRYR is explored in this research. Besides, four kinds of sensitive parameters are optimized regionally and the model performance on simulating streamflow, evapotranspiration, sensible heat, latent heat and soil moisture is evaluated by using the optimal model parameters. The results show that the runoff infiltration parameter (REFKDT) is the most sensitive parameter to the streamflow over the SRYR, and the influence of the surface retention depth (RETDEPRT) is not obvious, while the channel Manning roughness parameter (MannN) and the overland flow roughness parameter (OVROUGHRT) have a great effect on the speed of infiltration excess water that flows into channel networks and the streamflow. The WRF-Hydro model has ability to depict land surface and hydrological elements over the SRYR, while the simulation results are better in the high flow years with a Nash-Sutcliffe efficiency (NSE) coefficient of 0.39 than in the low flow years with a NSE of -0.06, which means that the parameters based on the calibration of the high flow years have certain limitations when applied to the low flow years. The high-resolution land surface and forcing data, multi-parameter calibration, and more sophisticated calculation mechanisms of subsurface flow are contribute to improving simulations in the future research.

The Tibetan Plateau is the source of most of Asia's major rivers. Detailed knowledge of its hydrogeology and hydrogeophysics is paramount to enable the further understanding of the water cycle on Tibetan Plateau. We conducted field investigations on hydrogeology and hydrogeophysics in a TP catchment – the Maqu catchment in the Yellow River Source Region (YRSR). For the hydrogeology survey, 40 water table depths were measured during 05-08 August 2018 and 20 August – 05 September 2019, corresponding hydraulic heads were estimated and interpolated in the eastern study area. 11 aquifer tests, including 8 slug tests and 3 pumping tests were carried out to assess aquifer hydraulic conductivity. Eight level-loggers were installed during 27 August – 05 September 2019 to monitor the water level fluctuation for one year. The results suggest that the groundwater flows from the west to the east, recharging the Yellow River. Aquifer hydraulic conductivities range from 0.1 m.d^-1 to 15.6 m.d^-1. The water level fluctuation within a year is between 6.61 m and 0.46 m. The hydrogeophysical survey includes Magnetic Resonance Sounding (MRS), Electrical Resistivity Tomography (ERT), and Transient Electromagnetic (TEM). ERT profiles indicated that an aquifer exits underground and contributed to MRS inversion, MRS soundings provided detailed information on water content and aquifer parameters, TEM provided subsurface resistivity at much deeper depths than ERT and determined the depth of the Yellow River deposits. These in situ data provide valuable information in the TP, and contribute to future hydrology and hydrogeology modeling to improve the understanding of the water cycle at the Maqu catchment in the YRSR. Besides, the one-year water level data can be assimilated to improve the model. And data of groundwater level depth, hydraulic conductivity, and water volume estimated from MRS can be used to calibrate or verify, or directly contribute to related datasets.

Flood-inundation modelling is an essential approach for understanding flood dynamics and implementing flood risk management. Although its computational burden is becoming less owing to increasing computer resources, flexible coarsening techniques and so on, it still remains challenging to perform 2-D flood-inundation simulations at large scales or fine spatial resolutions. Especially for fluvial flooding or lake area dynamics, flood area is far smaller than the computational domain except for limited flood periods, which eventually yields unmeaningful computations of dry-cell simulation or even wet-dry judgement. Against this problem, this study presents a simple but novel algorithm in the 2-D flood-inundation modelling, called the Automatic Domain Updating (ADU) method, which dynamically updates the simulation domain within flooded areas in each time step by tracking the location of wet and dry interfaces. The proposed algorithm has been applied to several case studies of river flooding and long-term lake water dynamics. The results show that the ADU method reduces the computational time for grid-based 2-D flood-inundation simulations typically by 5%–20% for river flooding and 29% to 45% on 8 and 48 cores for lake flow simulations.

This study aims to predict a severe flood event a half-day ahead. We developed an ensemble flood forecast system that predicts the probability of flooding nationwide in three damage levels. This system uses an operational flood forecast model, "Rainfall Index Model," in Japan in combination with a large ensemble weather forecast. This study investigated the impacts of a large ensemble size (1000) on the probability of occurrence of flooding for the different sizes of river basins. The system predicted the maximum probability of exceeding the historical magnitude flood of 60% 11 hours before the flood event.

The 2011 Great East Japan Earthquake caused millions of people in Tokyo to have difficulty returning home, revealing the vulnerability of cities to disasters. Tokyo was not affected by the tsunami, so it didn’t do much damage. However, flooding in a congested metropolis is expected to cause significant damage. In large cities, underground spaces are actively used because there is no land for development above ground, and especially in large cities such as Tokyo and Osaka, underground spaces are constructed in a very intricate way. Given the above conditions, inundation of underground spaces in large cities, which are vulnerable to congestion, is likely to cause large-scale human suffering if evacuation is not carried out properly. In the case of flooding in underground spaces, not all exits can be used safely, and evacuation should be considered in cases where exits are blocked. In this study, we conducted an evacuation simulation in a virtual space that mimics an underground space using a multi-agent system. The results of the evacuation simulation using a multi-agent system is to be presented.

The accuracy of urban flood simulation is highly dependent on the accuracy of the elevation data and flow friction parameters. However, acquisition of high resolution watershed data is conventionally challenging, especially on larger urban domains. A method of modifying existing mid-resolution DEM is proposed in order to supplement the representation of sewer network in the developed urban flood model. The flood calculations were achieved by applying 2D shallow water equation in the surface flow and the kinematic equation in integrated multiscale simulation developed in recent literature. The finite volume method numerical discretization scheme is implemented. With the flux calculated using the Harten-Lax-van Leer Contact (HLLC) approximate Reimann solver. Applying the model in an extreme rainfall event in Marikina-Pasig river basin in 2009. The results area also calibrated to identify manning coefficient corrector for the watershed results show that the simulations were able to capture the flood propagation along the building configurations. This can aid us in identifying flood prone areas where flood action parameters may require modifications. The proposed method can be used as an alternative to perform high-resolution urban flood simulation with limited availability of detailed elevation data.

Floating debris cause deterioration of river environments by exerting an adverse influence on the landscape and water quality. Moreover, they are released into oceans, thus becoming marine debris, which can have bad effects on ecosystems and human health. However, the dynamics of floating debris are still unknown, making it necessary to develop an effective monitoring method; e.g., image analysis techniques using river cameras proved to be effective. In this study, we develop a novel methodology based on previous studies for continuous observation of floating debris in rivers by using deep learning, and we here proved its usefulness. As a next step, we applied this technique to analyze the discharge characteristics of floating debris in the Onchi River in Osaka, Japan. Moreover, our model was applied to a flood event that occurred in August 2021: a flush phenomenon—a characteristic discharge of floating debris—was observed during this event. Furthermore, it was observed that the longer the preceding non-rainy weather period was, the larger the amount of deposits in the river basin, and thus, the larger the number of litter runoff due to rainfall was. Additionally, a correlation was found between the amount of precipitation and the number of floating debris, taking into account the precipitation of the previous day using the API (Antecedent Precipitation Index) of the preceding rainfall index. Consequently, this study constructed an equation to predict the number of floating debris from the amount of precipitation, and the number of floating debris in the river was estimated to be 1.92 × 10⁴ pieces/year. This value was converted to volume and mass, based on the results of the survey conducted on floating debris collected by the oil fence, and the results correspond to 1.02 × 10⁴ L/year in volume, and 1.34 × 10³ kg/year in mass.

There has recently been an urgent concern about whether global climate change and the artificial waste heat from urban regions could significantly affect current stream ecosystems at urban rivers. This presentation tried to analyze the thermal impacts of treated sewage effluent on stream temperatures by the field observation and thermal budget analysis in an urban river. River temperature is one of the essential indices that govern the physical environment of river ecosystems. The urban river analyzed here was the Tama River flowing through the Tokyo metropolitan area. The Tama River treated sewage effluents with a constant temperature inflow from several water reclamation centres, introducing artificial thermal impacts on the river ecosystem. Field observation revealed that advective heat flux from the treated sewage effluent significantly affected the river temperature formation in the midstream. In contrast, the river temperature streamed with a nearly constant temperature downstream near the river mouth. The thermal budget analysis also confirmed that the river temperature in the midstream was more susceptible to the treated sewage effluent than that in the downstream, particularly in winter. Other factors that affected the river temperature formation, e.g., seasonal fluctuations in river and sewage discharges, were further discussed.

Flash droughts have raised a wide concern in recent years. Besides many regional analyses, global distributions of flash droughts have been discussed in a few studies. With certain differences due to different drought indices or datasets, a few hotspots consistently show increasing flash droughts among studies. However, to date, there is no global picture on whether flash droughts have been intensified, or whether the intensification will continue into the future. Here we propose a method to quantify the intensification of global flash droughts, and investigate the historical trends (trends in the past 60 years) by using global reanalysis data and CMIP6 climate models with or without human-induced climate change. The human fingerprint can be identified for the global trends, which suggests the important role of anthropogenic intensification of global flash droughts in the past. Moreover, future projection of flash drought is also carried out over IPCC SREX regions by using CMIP6 future scenarios. The results show that intensification of flash droughts is projected to continue across most regions, with larger increase under higher emission scenarios. This raises an urgent need to adapt to the intensifying flash droughts in the future.

A recent flash drought in 2012 summer caused over 100 deaths and $ 25 billion of economic losses in the Midwestern United States (MIDUS) due to failed forecast of the flash drought with a rapid onset. Prior to the 2012 flash drought, there were extensive wildfires in MIDUS region in late spring, March. Extensive wildfires highly have effects on the change in land covers by affecting surface water/energy budget and land-atmospheric fields. This study focuses on potential impacts of the extensive wildfires on the 2012 flash drought in MIDUS through large ensembles of WRF with change in land cover. Results show that latent heat fluxes are highly affected by the change in land cover, resulting in a contrast between direr top soil layer and wetter root-zone soil layer. Through the framework of convective triggering potential (CTP) and low-level humidity index (HI), we reveal that drier and hotter near-surface by post-wildfire drives drier land-atmospheric coupling. At large-scale, the effects of post-wildfire modulate a blocking system at middle troposphere and the warming of near-surface. This study suggests that wildfires are one of potential triggers of flash droughts and be considered to reduce the risk of 2012-like MIDSU flash drought.

This study proposes a temporally self-calibrating Effective Drought Index (scEDI) using the moving time window for climatology. The scEDI is computed to detect and characterize historical and present droughts, using over 240-year precipitation records from a station in Seoul, the Republic of Korea. The scEDI-based characteristics of detected droughts are compared with those from the original EDI with three different reference periods. In addition, social response to historical and present droughts detected by the scEDI are investigated using drought reports in the Veritable Records of the Joseon Dynasty and public interest in drought from the social monitoring data, such as Google Trends and NAVER DataLab. Results show that the scEDI successfully adapts multi-decadal variability of precipitation, leading to a robust assessment of drought identification and characterization over the study period. This study suggests the importance of self-calibrating on the EDI-based drought assessment and provide an insight about how to investigate interactions between drought and social response at the daily scale (a type of “socioeconomic drought”).

Skillful seasonal prediction of extreme precipitation is crucial to mitigate socioeconomic damage, but current climate forecast models often failed to predict seasonal droughts and pluvials. This study aims to evaluate the prediction skill of springtime (March through May) precipitation over Northeast Asia (NEA) in one lead month. Over 1992–2010, the role of tropospheric jet streams in predicting NEA pluivals and droughts is examined using fully-coupled climate forecast model (CFM) simulations and atmospheric global circulation model (AGCM) simulations forced by observed SST anomalies. Results show a relatively better prediction skill of spring pluvials than that of spring droughts from both CFMs and AGCMs, indicating asymmetry in the seasonal prediction skill of extreme precipitation over NEA. A relatively low prediction skill of spring precipitation deficits in fully-coupled climate forecast models is caused by the warm (cold) biases of sea surface temperature anomalies (SSTA) over the northern Pacific Ocean in droughts (pluvials). This result suggests that the reduced SSTA biases over the northern Pacific Ocean are necessary for a systematic prediction skill of spring droughts and pluvials over NEA.

In a changing climate, climatic extremes are expectedly more common, but interactions between climatic extremes and associated changes in the risk have not well studied. Here, this study aims to investigates the influence of tropical cyclones (TCs) from the western Pacific on droughts over the Korea Peninsula over 1980-2020. First, TC-related daily precipitation are constructed using the ECMWF Reanalysis version 5 (ERA5) hourly precipitation and hourly track information of the center of tropical cyclones. Next, the Effective Drought Index values are computed from precipitation with and without TC-related daily precipitation. The impact of TCs on drought is examined in terms of the drought spatial extent, duration, and intensity. Results show that 1994 is the most beneficial year for drought mitigation (-30% of the spatial extent under extremely drought condition (EDI<-2), -100 days of duration) due to TC landfalls over the Korea Peninsula. The findings of this study suggests the importance of the representation of TCs in climate models on the future drought risk over the Korea Peninsula.

As natural disaster hazard intensifies drastically, attributed to the effect of global warming, the capacity to prevent disaster in Japan has been weakened due to degrading infrastructure and an aging population. We discuss the inundation damage and the adaptation of flood control in the downtown area of the Kase River basin using the existing Hokuzan Dam and Kasegawa Dam for the heavy rain in August 2019 and a future heavy rain event on the basis of d2PDF when the global average temperature would increase by 2 °C since the Industrial Revolution. The Kase River basin is located in the northern part of Kyushu Island in western Japan. Currently, the Kasegawa Dam is a multipurpose structure with the roles of flood control and water utilization, while the Hokuzan Dam is used only for water utilization. We investigated using the water utilization capacity of the two dams for flood control by using a prior discharge. Our results demonstrated that river water flooding can be controlled in the Kase River basin even under the future heavy rain event in d2PDF as well as the heavy rain in August 2019.

Urban flood events due to alteration in extreme precipitation pattern are increasingly reported in the context of climate change posing bigger challenge for stormwater managers. In this study, an attempt has been made to investigate impact of climate change on extreme precipitation events over Pokhara Metropolitan City which is capital of Gandaki province, Nepal. Pokhara region experiences heaviest precipitation in Nepal. The changes in precipitation extremes have been analyzed by considering climate projections of near-future (2021–2040) and far-future (2081–2100) periods with respect to the baseline period (1995-2014). Global Climate Models (GCM) projections are widely used to understand the impact of climate change on precipitation extremes. Two GCM (BCC-CSM2-MR and MRI-ESM2-0) datasets were used from the CMIP6 models. The daily precipitation under the SSP2–4.5 and SSP5–8.5 scenarios were used to estimate extreme precipitation events. To assess extreme precipitation, the study used five indices: total number of rainy days during monsoon period (June –September); heavy precipitation days (>50mm); very heavy precipitation days (>100mm), annual daily maximum precipitation, and annual three-days maximum precipitation. Annual 24-hr and 3-days maximum precipitation were compared for 5-, 10-, 20-, 50- and 100-year return periods. All five indices revealed an increase in extreme precipitation events in future. The increase in extreme precipitation events are expected to result more traffic disruption in monsoon period, and hence losses due to increasing urban floods. The findings of this study is expected to provide researchers and stormwater managers an opportunity to better understand characteristics of precipitation extremes in changing environment for proper design of urban drainage system. Keywords: Climate Change, CMIP6, GCM, Extreme Precipitation.

Per- and Polyfluorinated Substances (PFAS) have been used in a variety of manufacturing processes and industrial applications. PFAS are persistent, bio-accumulative and potentially toxic. Due to water solubility and surfactant properties, distribution and mobility of PFAS in the aquatic environment represents a serious risk to the environment and human health. In the context of present work, PFAS contamination is connected to historical use of the Aqueous Film Forming Foam (AFFF) at the firefighting facilities and installations. Unconfined release of the AFFF in the fire-training activities, firefighting equipment tests and emergency events can lead to severe contamination of the surrounding aquatic environment. Occurrence of the PFAS and drinking water contamination are investigated for the municipal water supply in Ronneby, Sweden. The general purpose of the study is to reconstruct the drinking water contamination history. The analysis of the water contamination scenarios is conducted considering several interconnected processes/domains. These including the contaminant production/emission, sorption/transport in heterogenous media, far-field transport, water extraction/production, water treatment and distribution. Assessment of the contaminant distribution/transport in the water supply is conducted by means of the hybrid simulation framework. The semi-quantitative retrospective predictions are consequently used for analysis of the drinking water contamination scenarios.

Water quality and scarcity are among the most severe problems humans have been facing in the last decades. Indian surface water quality has deteriorated due to anthropogenic activities, for instance the rapid population growth, urbanization, disposal of wastewater and solid wastes, deforestation, and climate change. For the need of sustainable environment and water resources, there is the need to develop protocols and measures to improve the water quality. Taken the Indian climate into account, we aimed to investigate the influence of the monsoon season on water quality and to seek possible restoration measures for the water bodies. In the present study, seasonal and spatial water quality regarding physical, chemical, and biological parameters from a lake cascading system was assessed. Furthermore, the water quality was assessed and compared by guidelines from different nations. Our results showed clear temporal and spatial variation of water quality in 2019, with better water quality in rainy season (Oct.-Dec.) and downstream lakes while relatively worse water quality was recorded in dry season (Jul.-Sep.) and upstream lakes. Our findings indicate that the water quality is impacted by human activities, discharge of domestic, municipal, and industrial effluents combined with dumping of solid wastes has vital negative impacts in the study area. Suggestions for further restoration have been provided: 1) the water quality is unsuitable for drinking, it is necessary to do some pre-treatments before using it; 2) local authorities should take more preventative measures; 3) it would be better to prevent the pollution than to eliminate it afterwards; 4) a long-term monitoring of water quality will provide a solid base for the restoration project. Apart from the parameters mentioned in this study, heavy metals should be also included in evaluating the water quality; 5) more restoration projects should be continued in other lakes of Chennai.

The number of death by flooding is increasing due to many extreme flood events recent years. Likewise, the damage of cars due to drift by flooding becomes more tangible these days. In order to cope with these tragedy, a model was developed to simulate human/automobile movement in time of flooding. The model was developed based on the relationship between drag force by flow and slope friction on the surface. Once the drag force exceeds the slope friction, the human/automobile starts to move. The slope friction is considered using the relationship between the buoyancy and weight. After the initial movement, the human/automobile continues to move following the flow simulated by a shallow water equation. Some results of this model application are to be presented.

El Niño Southern Oscillation (ENSO) modulates rainfall amount variability and, by extension, river discharge for the Philippines on seasonal to interannual temporal scales. The El Niño period (ENP) of ENSO considerably decreases rainfall amounts on a seasonal scale with varying degrees of heterogeneity across the Philippines. The response of the hydroclimate to ENP on an interannual scale is relatively immature. To investigate the hydroclimate response, a composite time series of 29 rainfall and 61 river discharge stations spanning 1901-2020 and 1908-2017 C.E., respectively, and covering the four major climate types in the Philippines were assessed. Results suggest, regardless of climate type, that river discharge and rainfall data decrease following ENP. The median response suggests the decreasing trend can last up to 7 years. The sign of the hydroclimate response is either decreasing, if at conception of an ENP, or increasing, if at the termination of an ENP. The results have implications for water resource management on an interannual scale.

Changes in precipitation and temperature due to future climate change cause several water-related disasters. In the field of water resource management, the allocation of resources to respond to climate change should be made rationally in consideration of various factors. When allocating water resources, there are constraints such as planned allocated capacity. Therefore, it is necessary to determine and allocate the area that should be allocated preferentially for rational allocation. In this study, an iterative framework for permeable pavement allocation was suggested to improve water cycle in the urban watershed under the future climate environment, and the planned allocated area of permeable pavement was assumed for a rational allocation approach under limited capacity. 15 CMIP6 GCMs according to 2 SSP scenarios were used to estimate future climate variables of the study area. 27 sub-watersheds were selected as candidate sites for permeable pavement and were modeled using ArcMap and storm water management model (SWMM). The iterative framework begins with the assumption that the improvement effect of water cycle in sub-watersheds according to permeable pavement allocation will change the final allocation priorities. The priorities of 27 sub-watersheds are robustly determined using a multi-criteria decision making (MCDM) technique. Each iteration continues until the allocated area of permeable pavement according to priority converges to the area of the initially assumed planned permeable pavement. The results of this study show that the effect of improving water cycle in sub-watersheds by iterative allocation changes the allocation priority of permeable pavement. Since various social, environmental, and economic factors are considered, the iterative framework of this study can be applied to real problems. Acknowledgements: This research has been performed as Project No Open Innovation R&D (21-DC-002) and supported by K-water.

Rising temperatures and uncertain precipitation trends could change the timing of snow melt and snow accumulation over Himalayan mountainous region consequently altering the hydrological cycle. In this study, we investigated the future hydrological changes and uncertainties on climate change impact assessment over one of the snow-fed catchments lies in Western Himalayan region, Astore. To this aim, we forced a processed based hydrological model WRF-Hydro/Glacier under multiple global climate models (GCM), bias correction methods (BCM) and multiple optimized hydrological parameters over three time periods over three period, base line (BL; 2000-2019), mid future (MF; 2040-2059) and far future (FF; 2080-2099). Considering the streamflow, snow covered area (SCA) and evapotranspiration (ET), seasonal changes were evaluated using simulation results from WRF-Hydro/Glacier. Then by using analysis of variance, we segregated and quantified the contribution of GCM, BCM and model parameters (MP) in projecting future hydrology of Astore catchment. The simulated results show that compared to BL period, the peak stream flow is projected to shift from July to Mid-June during MF and a further shift in Mid-May during FF period due to early melt and late accumulation of snow. This shift in the hydrologic regime would trigger the hydrological droughts in the region. Our finding also suggests that the selection of appropriate GCM and MP should be more emphasized than that of BCM in projecting streamflow and SCA. In low flows GCM while in high flows MP is a contributor towards the total uncertainty. The findings of the present study can help drought mitigation as well as long-term adaptation strategies over Astore. / Acknowledgement: This work was supported by the Basic Science Research Program (2020R1A2C2007670) and the Framework of International Cooperation Program (2021K2A9A2A06038429) through the National Research Foundation of Korea (NRF). 

Over the East Asian region where summer monsoon is relatively more associated with droughts, thus a decreasing trend in the summer monsoon could cause intense drought events with longer duration. Aridity Index (AI), the ratio of precipitation (P) to the potential evapotranspiration (PET), is one of the widely used index to quantify the drought, its intensity and duration under variable climatic conditions. There are several methods to estimate the PET, e.g., Thornthwaite (PET-TH), Penman-Monteith (PET-PM), modified Penman-Monteith (PET-MPM), and energy (PET-EN). Here we examined the change in PET by using above mentioned approaches over East Asia during two future periods e.g., mid future (2031-2050) and far future (2071-2100). To this aim we used meteorological data from Couples Model Intercomparison Project Phase 6 (CMIP6). First, we quantified the drought index from CMIP6 during the historical period (2001-2020) and compared it with the drought index quantified from ERA-5 dataset during the same period. The results showed that different approaches to quantify the PET projects different drought trends. / Acknowledgements: This work was supported by the Basic Science Research Program (2020R1A2C2007670) and the Framework of International Cooperation Program (2021K2A9A2A06038429) through the National Research Foundation of Korea (NRF).

In recent years, sediment disasters caused by heavy rains and typhoons have occurred frequently in Japan. Especially within the Fuji River Basin in central Japan, many regions are vulnerable to sediment disasters. For the risk reduction of sediment disasters, it is necessary to develop a sediment disaster risk estimation method that considers both trigger and inherent factors. This study developed and validated a method to estimate sediment disaster risk that directly considers trigger and inherent factors in the areas around the Fuji River Basin (Yamanashi and Shizuoka prefectures) using a deep learning method. A fully connected deep neural network was used as the deep learning method. As the input data for trigger factor, 60 minutes accumulated rainfall and soil water index within each cell were used. The horizontal resolution of cell size was around 1km. As the input data for inherent factors, the maximum slope angle and presence of faults within each cell were used. The sediment disasters caused by typhoons on 6th September 2007, 21st September 2011, 12th October 2019, 3rd September 2011 were used for training, determination of threshold, cross-validation, and validation of the deep learning method. For quantitative validation, we estimated the sediment disaster risk from neural network outputs and validated it by comparing sediment disaster occurrence reports. In the validation, an administrative area is regarded as “True Positive” if there are any” high-risk cells” and any “confirmed disaster cells” in the same area. We calculated the evaluation metrics based on a confusion matrix for validation. Our method shows high accuracy (0.63), indicating that the estimated sediment disaster risk is adequate. Therefore the risk information can help the decision-making of evacuation in the future. However, the False Alarm Rate was still high (0.90), so further improvements are required in future studies.

The Philippines being in a tectonically active setting is affected by vertical land movement (VLM) that significantly affect the observed sea level (SL) along the coast. As it is surrounded by large bodies of water, ocean dynamics and climate pattern also contributed to the variations of SL. The recently concluded Coastal Sea Level Philippines Project investigated the coastal SL trend in 25 out of 50 tide gauge (TG) sites. Similarly, SL trends were also determined from retracked satellite altimeter (SA) products from different satellite missions. The influence of non-climatic factor VLM on the sites were determined using Permanent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) and validated with data from GNSS (Global Navigation Satellite System) receivers collocated with the TG. The investigation of the occurrence of El Niño was undertaken to explain the computed SL trend. The results showed that areas with long period of observations (19 years or more) exhibit an increasing SL trend that varies from 1.38 to 13.13 mm/year. However, majority of the TGs that were installed in 2007 and 2008 recorded only 13 and 12 years of SL observation up to 2020, respectively. A decreasing SL trend were observed on said TGs except for those located in Palawan. Similar trends were also observed from sea surface height (SSH) from satellite altimeter. A 0.96 correlation was computed between TGSL and 20 Hz SSH. Investigation showed the strong influence of El Niño during this short period of observation that caused the SL to fall. The VLM rates from 9 sites with collocated GNSS receivers exhibit land subsidence ranging from -3 to -7 mm/year. The PSInSAR and GNSS VLM derived rates have a correlation of 0.89. For some sites VLM rate is larger than the SL rise rate, thus masking the true TGSL measurement.

The frequency and intensity of hazardous weather events have increased year by year under climate change. For flood early warning, the Water Resources Agency (WRA) applies rainfall thresholds of rainfall observations based on the conditions of the actual rainfall in different hours and coordinate with real-time rainfall observations (such as QPESUMS). However, using observed rainfall data limits the current flood early warning system; more advanced improvement to issue forecasts and relative risky disaster alerts can be built in advance. So as to develop completeness of flooding disaster warning system, radar reflectivity is adopted to improve the spatial resolution from one maximum value to three dimensions in the flood-prone area of Taipei City, Zhonghua village in Songshan District, and hourly rainfall data of its nearest observation stations from 2014 to 2018. An unsupervised neural network (Self-organizing map, SOM) is applied to establish the relationship between the three-dimensional radar reflectivity patterns and pluvial floods. Then using k-means analyzed the clustering vectors corresponding to flooding disaster events through extracting the correlation between the radar reflectivity and the probabilistic. Finally, a hazardous radar reflectivity pattern could be identified, and a hot zone of topological map based on SOM could be carried out for improving pluvial flood warning. Consequently, preliminary research shows that after clustering by SOM and k-means, the vertical distribution of radar reflectivity is highly correlated with the probability of pluvial flood disaster events that could provide a probabilistic flood warning message with enhanced spatial resolution for community emergency response teams to adopt preventive measures.

To implement any reservoir management strategy in reservoir systems, it becomes necessary to investigate the characteristics and dynamics of turbid water. The primary considerations for better desilting efficiency, especially for the inflowing turbid water, are in-time operation and feasible locations of hydraulic works. Therefore, physical and numerical tests were conducted to investigate the factors influencing the performance efficiency of the desilting tunnel in the Zengwen Reservoir, Taiwan. Three inflow rates, i.e., 18 m³/s, 32 m³/s and, 44 m³/s to represent different inflow hydrological conditions, were tested for an outflow rate of 777 m³/s for desilting tunnel whereas, the other outlets were treated as an opening. To examine the performance of the desilting tunnel, we focus on suspended sediment concentration in the approach flow area to the inlet of the desilting tunnel, which acts as a pressure sluicing. The parameter considered to evaluate the desilting efficiency is the inflow rates and the ratio of the distance of the influenced flow field to the diameter of the desilting tunnel. The lowest ratio tested is 0.3, which gives the highest desilting efficiency, around 100% for all inflow rates. In contrast, the highest ratio of 1.5 tested shows the least desilting efficiency of 70%, 55%, and 45% for a flowrate of 18 m³/s, 32 m³/s, and 44 m³/s, respectively. The study shows that ratio and inflow rates have an inverse relationship with desilting efficiency. The experimental results show a 14% average inaccuracy to the theoretical equations. The numerical model used is Ansys-CFX which calculates the flow using Reynolds-averaged Navier-Stokes equations. The model adequately predicted the sediment vented through a desilting tunnel with less than a 10% error percentage. Our findings suggest turbid water is fully drained when it flows within a diameter of the desilting tunnel.

To design the best pumping test strategy, the sensitivity analysis of hydraulic characteristics such as transmissivity (T) and storativity (S) is an important pre-work. In many previous studies, the sensitivity analysis based on the sensitivity map made by the two-dimensional model was discussed. After a long period of data accumulation, it is found that although there will be continuous changes in the discharge, there is no significant change in the hydraulic gradient near the pumping well and the observation well. From this, it was concluded that we could not use a two-dimensional sensitivity map to get the exact location of the sensitivity source in space. In addition, most of the current research is based on the assumption of homogeneous steady-state conditions, but groundwater mostly exists in the form of heterogeneous transient states in nature. Therefore, this research hopes to use the method of inverse calculating the heterogeneous field to plan and use the developed software (VSAFT3) for effective 3D space simulation, so as to use the characteristics of the stereoscopic 3D space concept to confirm and extend discuss the various sources of information. This will make a great contribution to the future analysis of changes in regional flow fields, groundwater replenishment patterns, and control of the diffusion of underground pollution.

The water crisis remains an unsolved issue of freshwater scarcity for sustainable water management due to climate change and human activities to address for various uses. The extent of aquifer recharge and river flows over time and space affects the availability of water supplies varying in the hydrologic nature. Hence, the objective of this study was to evaluate the spatiotemporal variability of groundwater recharge using the Soil and Water Assessment Tool (SWAT) and Bflow Digital Filtering Program for process understanding of a watershed. The SWAT model simulation input and outputs process were performed with digital elevation model soil, land use/cover, and weather data. The performance and simulation uncertainty of the model has been evaluated with the calibration and uncertainty program (SWAT-CUP) the Sequential Uncertainty Fitting (SUFI-2) algorithm. The simulated result was calibrated and validated sensitive parameters at the catchment outlet. The reliability of the model was examined using statistical measure values: coefficient of determination (R²), Nash–Sutcliffe model efficiency (NSE), and Percent of Bias (PBIAS) for streamflow performance. The model results indicate satisfactory agreement between monthly observed and simulated streamflow during calibration and validation time steps at the catchment outlet. The assessment found that surface and groundwater flow parameters significantly affect streamflow simulations in the spatiotemporal variability of groundwater recharge and other water balance components. Therefore, the effects of the base flow recession factor on streamflow hydrograph were considered as a reasonable task. Finally, it was estimated that the base flow separation with Bflow Digital Filtering Program to check the effect of base flow on streamflow hydrograph. The simulated base flow enhanced the SWAT model with the alpha base flow factor. Hence, it was found that the SWAT model reasonably represents groundwater recharge variabilities on shallow aquifers. Funded by Ministry of Science and ICT, Project no. 20220275-001

Outdoor activity and field trip is important for learning earth science. Additionally, the ability for design and preparation before going outdoor is an important literacy, such as to interpret weather forecasting information and personal outdoor risk management. However, students often feel abstract about the relationships among locations, weathers, risks, and personal health-protection, and get unawareness about the forecasting and protection. Board game can be a potential tool for assisting learning. In this study, we proposed a board game named “Weather-Collaboration,” which aimed at immerse students into an environment with outdoor activities. Students need to use the digital weather forecasting APP named “LOHAS Weather,” and discuss with peers about the outdoor activity design, essential materials preparation, and risk management. If students deciding their preparation, the game will show the weathers in the location and the result of risks and personal health. It took 60 minutes to play full game. Questionnaires were developed and used to evaluate the students’ knowledge and attitude. The results revealed that after “Weather-Collaboration” playing, students build better connections between weather foresting and outdoor risk management. The students also showed positive motivation for applying “LOHAS Weather” APP in daily life. The results revealed that the APP-integrated board game can improve students’ knowledge, ability and attitude toward outdoor management. 

The Regional Advisory Committee (RAC) was first established in 2018 with the purpose of promoting the participation of ASEAN and Indian geoscientists in different disciplines and of different age groups in AOGS. In addition, RAC should also work to enhance regional cooperation. The inputs of the RAC members have been useful in the introduction of new initiatives such as the eBook version of the Extended Abstracts and the consideration of a new monograph series in cooperation with Springer. Besides the organization of a webinar with descriptions of possible regional cooperation by Section Presidents, an online seminar series with graduate students and early career researchers from different institutes in Asia has also been held during the COVID-19 pandemic. We plan to continue these lines of activities complementary to the annual on-site meetings in Singapore and other places. More recently, we have begun the formation of a Coastal Zone Risk Mitigation and Management Working Group (CZWG). Joining the working group are experts from China, India, Macau, Singapore and Taiwan. The CZWG is in the process of recruiting scientists from other countries. Another possible topical working group of similar structure is about the study of the equatorial and low-latitude ionosphere. The main purpose of such RAC working groups is to identify and formulate large-scale cooperative geoscience projects of common interest and unique values to the AOGS scientific community.

The Discover Space Camp is conceived as part of the Discover Camp that the School of Science and Technology Singapore (SST) organises for its graduating students. The aims of the Discover Camp are to expose the students to career and academic possibilities that they will be making decisions in the near future. The Discover Camp is designed to incorporate Applied Learning approaches in its delivery. Applied Learning includes activities that are learner centred, active, relevant, process focused, integrated, authentic, or community focused. Space Science encompasses all of the scientific disciplines that involve space exploration and the study of natural phenomena and physical bodies occurring in outer space, such as space medicine and astrobiology. The Discover Space Camp was conceived because of its growing presence in the educational and career landscape that the students in the near future will be exposed to. The programmes consisted mostly of theory lessons, talks by scientists, and hands-on applications of the field of Space Science. The AOGS community plays an important part in helping to shape the development of this programme. In particular, Dr I-Te Lee and Professor Loren Chang were invited to give talks related to Space Weather and Satellite projects. They provided insights to the field of Space Science through their direct research and applications of the Space Science and Technologies. The response from the students were favourable as the information and learning provided were directly from the people in the industry. Through this sharing, I hope to motivate the audience to develop programmes to further the outreach of Space Science and Geo-Science alike. This is also an invitation to gather other interested geoscientists or space scientists to contribute to such programmes in the future.

The term, space weather, refers to all variable physical parameter and conditions on the Sun and in space environment, such as solar wind and radiation, plasma density, high-energy particles, and magnetic fields. When space weather rapidly changing of, it would make significant impacts of technology we use, like radio communication and positioning system or disrupt power lines and satellites. In order to promote preventive notions of disasters and provide information about space weather, the Central Weather Bureau in Taiwan established the Space Weather Operational Office (SWOO) to monitor and forecast space weather conditions as well as conduct education outreach activities. Since 2015, SWOO holds variety lectures and activities for students and general public to introduce knowledge on space weather and associated influences. Meanwhile, SWOO also supports summer intern program of CWB for junior college students to understand application and operations of space weather. From operation to education outreach, this presentation will detailed demonstrate achievements of outreach education for space weather by government meteorology agency.

Existing analytical models usually consider unsaturated flow due to a surface infiltration basin is one-dimensional and the infiltration rate is uniform over the entire surface area. However, the infiltration basin is commonly rectangular or circular in reality (i.e., the infiltration rate is local to the surface area) and causes an environment of two-dimensional flow in unsaturated soils. This study hence develops a two-dimensional mathematical model to describe the steady flow in an unsaturated zone of infinitely horizontal extent with an infiltration basin on the ground surface. This model comprises Richards’ equation for the unsaturated flow. The Gardner exponential formula is hired to designate the relative permeability and specific moisture capacity of the unsaturated zone. Owing to the essential nonlinearity of Richards’ equation, the model is linearized by means of the Kirchhoff integral transformation. The analytical solution to the linearized model is derived via the Fourier cosine transform. The effects of hydraulic parameters on the flow are clearly explored through the solution. The present solution is expected to provide good efficiency in calculations and be a useful tool of predicting the profiles of the pressure head or water content in the unsaturated zone.

Dynamic storage is the part of groundwater storage that is more sensitive to the external factors (e.g. climate change, human activities). It plays a critical role on maintaining the ecological habitat and human water use and mediating the hydrological impact from environmental change. Previous studies have widely explored the storage-discharge relationship through the simple water balance, applying to estimate the groundwater storage at the catchment or basin scale. However, the dynamic storage consists not only streamflow generation but also evapotranspiration, and other possible paths for groundwater loss. Therefore, the aim of this study is using the flow duration curve model to estimate the seasonal recession characteristics and direct storages which represent the aquifer discharge contribute to river, understanding the model applicability to the catchment scale. We then combine the water balance method to estimate the indirect storage which is insensitive to streamflow, exploring the seasonal dynamic storage components. The results showed that the seasonal difference in the recession characteristics is related to the aquifer range that the dynamic storage passes through and the catchment characteristics. The dynamic storage components show a significant difference in additional groundwater storage between the dry and wet seasons. These results can be used as a reference for hydrological simulation and prediction, and future water resources management.

To mitigate tsunami damage, early warning systems are operated around the world. In Japan, the Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) was recently developed in the Nankai trough (Kaneda et al., 2015). DONET are equipped with seismometers and ocean-bottom pressure gauges at 51 points on the sea floor and submarine data can be acquired in real time. These data are useful for early prediction of tsunamis caused by earthquakes and submarine landslides. We studied the relationship between offshore and coastal tsunami heights to use DONET ocean-bottom pressure gauges for early tsunami prediction. For the early tsunami prediction, previous works used only the maximum absolute values of the hydrostatic pressure changes during a tsunami (Baba et al., 2014, Igarashi et al., 2016). Although compressing time series of pressure gauges data, we have presented improved tsunami height prediction algorithms from the water pressure gauge data by linear regression (Baba et al., 2014) and Gaussian process regression (Igarashi et al., 2016). However, the time information from each sensor should not only be useful for predicting the arrival time of the tsunami, but for having information about the direction in which the tsunami arrive. Thus the time information could be important for extracting similar case of tsunami from the database. Here, the maximum tsunami heights in coastal cities were estimated by Gaussian process regression using the maximum tsunami height and the arrival time when the maximum tsunami heights were recorded at sensor point. Since the speed of tsunami depends only on the water depth, the arrival time is determined by the location of the sensor points and the epicenter. We verify the effectiveness of the arrival time by accuracy comparison when normal distribution noise is added and the arrival time is selected or not in the sparse modeling.

In recent years, natural disasters including earthquakes, typhoons, localized heavy rain, linear precipitation zones, and other extreme weather events have occurred frequently. There is a growing demand for essential technologies that provide safety and security to respond to these environmental changes in our everyday lifestyles. Conventional research encourages behavioral change to improve societal safety and security by utilizing real-time disaster prediction. Methods were proposed in local government drills to support smooth decision-making. As the next phase, it is necessary to create an "ultra-resilient society," which will overcome risk by creating a comprehensive system that can flexibly respond to future environmental changes that are difficult to predict by learning from the Great East Japan Earthquake and the subsequent ten years of experience in reconstruction and recovery efforts. We propose a digital twin (DT) for disaster prediction to support decision-making. To enable administrative personnel to recognize the possibility of a disaster at the earliest possible stage and take appropriate measures in the event of a disaster, the DT that allows what-if analysis considering the continuity of time and space will be constructed. We can respond flexibly to unknown disasters and contribute to effective decision-making. It is challenging to raise the level of experience of personnel sufficiently through the annual training alone. We will develop a system that provides additional expertise in responding to disaster risk to rectify this. Through the realization of the DT, we aim to create a change in personnel behavior that leads to an improvement in risk recognition and response capabilities by providing a simulated experience of disaster risk response. This paper will construct the DT for evacuation as an initial response to sediment-related disasters caused by heavy rain.

Climate change is anticipated to have enormous consequences on future hydrologic patterns. Studies on the potential changes in regional and local hydrologic patterns under climate change scenarios have been intense research areas in recent years. In recent years, extreme rainfall has become more frequent over the Korean peninsula, causing severe damage. In a changing climate, traditional approaches based on historical records and various climate change scenarios may be inadequate and may overestimate (or underestimate) design floods. The main objective of this study is to develop a stochastic disaggregation method of daily rainfall to extreme hourly rainfall and offer a way to derive the intensity-duration-frequency curves under climate change scenarios. Here, for this purpose, the design floods are estimated by using the HEC-1 model with multi-model ensemble scenarios constructed by assigning weights based on the L-moments. The proposed model is validated through the entire weather stations in South Korea and climate change scenarios simulated by the ten different RCMs. The results suggested an increase in flood risk, with the increase of design floods in a changing climate.  Acknowledgement This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT). (No. 2019R1A2C2087944)

Pakistan is regarded as most vulnerable to climate change based on the climate risk index(CRI) during the period from 2000 to 2019. Precipitation over Pakistan is concentrated in the monsoon season from 65% to 75%, and moreover, Pakistan’s water resources are heavily dependent on the Indus river. This study investigates the impacts of climate change when the temperature rises from 1.5 to 4 degrees in Pakistan under the SSP climate scenarios. A detailed analysis of changes in the annual temperature and precipitation patterns and the associated extreme climate indices under the SSP scenarios is presented. This study explored the projected annual relative changes for annual climate patterns based on precipitation and temperature from CMIP6 at 1.5℃, 2℃, 3℃, and 4℃ of global warming level relative to the 1850–1900 baseline through information on the regional aggregated signal over Pakistan as time series. For comparison purposes, the number of summer day (SU) values of the simulations estimated from all the climate models under RCP-2.6, RCP-4.5, RCP-6.0, and RCP-8.5 scenarios are explored. Moreover, we illustrate comparisons associated with the likely period of when we will reach warming of mean temperatures 1.5°C, 2.0°C 3.0°C, and 4.0°C under SSP and RCP scenarios, respectively. Overall, temperature extreme indices are more increased in CMIP6 than that of CMIP5. Acknowledgement This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI 2018-07010.

The climate change scenario featured by the IPCC is the main tool to understand future climate variability and climate change, but the associated change can be different due to the capability to simulate observed features of the climate. Moreover, due to the uncertainties of the future scenarios for the hydrologic extreme analysis, a single scenario-based approach has not been widely applied for providing a guideline of amending design criteria. Moreover, the use of the climate change projections could be problematic because each scenario can be different. In this regard, an ensemble approach to various climate change scenarios was developed. Statistical moments (mean, variance and skewness) obtained from a number of climate change scenarios were extracted to simulate hourly rainfall sequences using the NSRP (Neyman-Scott rectangular pulse) model. In order to consider uncertainties associated with climate change scenarios, an MME (multi-model ensemble) construction technique that weights the model based on the ability to reproduce precipitation characteristics is also proposed. This work was supported by Korea Environment Industry & Technology Institute(KEITI) through the Aquatic Ecosystem Conservation Research Program, funded by the Korea Ministry of Environment(MOE). (No. 2021003030004).

China's air pollution is a severe environmental problem. Meteorological factors, which could directly affect the dispersion of air pollutants, are closely related to the air quality index(AQI). Extensive literature describes the non-stationarities between meteorological factors and air quality by using the geographically weighted regression (GWR) or geographically and temporally weighted regression (GTWR). However, most of these studies ignore the case where the rate of numerical variations has spatial heterogeneity. To better reveal the potential spatiotemporal patterns of the impacts of some selected meteorological factors, such as ground pressure, relative humidity, temperature, wind speed and so on, on air quality in China from 2013 to 2018, We employed the spatiotemporal weighted regression (STWR) to explore the spatiotemporal non-stationary. Results show that the R² of the STWR model are higher than that of GWR and OLS when the rate of change of AQI is faster. Some spatially coefficient surfaces corresponding to different variables show significant seasonal variations, and there are significant differences in its spatial distribution in China. Some details are revealed as follows: 1) The impacts of humidity on AQI are more obvious in northwestern China from April to June and July to September. 2) The impacts of humidity on AQI in northwestern China has been different since 2016. In other words, the humidity had positive effects on AQI in most regions from 2013 to 2016 but has had negative effects since then. A possible reason could be that humidity aids sediment deposition and improves air quality by decreasing atmospheric particulates. 3) In most parts of southern China, the negative correlation between temperature and AQI tends to weaken, which may be caused by the gradual weakening of the temperature inversion phenomenon under climate warming. 

A waxy corn harvest date in South Korea is estimated using a coupled general circulation model(CGCM)-regional climate model(RCM) chain. The CGCM-RCM chain adopted in the study is made up the Pusan National University (PNU) CGCM and Weather Research and Forecasting (WRF) model. To estimate the waxy corn harvest date, 30-year (1991-2020) hindcasts (1-6 month lead) are produced by PNU CGCM-WRF chain and the daily predicted temperatures are accumulated from the seeding date (5 April) to the reference temperature (1,650∼2,200°C) for harvest. The model tends to have a cold bias of about 0.1°C in the mean air temperature averaged over the 6 months (April to September). To reduce biases, the monthly mean differences between observations and the predicted temperatures are regarded as systematic biases and removed from the model output. In quantitative terms, the waxy corn harvest date derived from bias-corrected hindcasts is DOY 187∼210, with a slight margin of 1.1∼1.3 days compared to the date from observation (DOY 188∼211). In qualitative terms, the estimated harvest date well simulates the general spatial pattern of observation while reflecting topographical effects. The study demonstrates that both the daily temperature and the waxy corn harvest date information can be obtained several months ahead using this approach. Reference: Hur, J., Y. S. Kim, S. Jo, K. M. Shim, J.-B. Ahn, M.-J. Choi, Y.-H. Kim, M. Kang, W. J. Choi, 2021: Estimation of Waxy Corn Harvest Date over South Korea Using PNU CGCM-WRF Chain, Korean Journal of Agricultural and Forest Meteorology, 23(4), 405~414 Acknowledgements: This study was carried out with the support of “Research Program for Agricultural Science & Technology Development(Project No. PJ014891)”, National Institute of Agricultural Sciences, Rural Development Administration, Republic of Korea.

The North Fiji Basin (NFB) is a large and complex back-arc basin in the southwest Pacific Ocean, located between the Australian and Pacific plates. It was the target of intensive research between the 1970s and the 1990s from American, Japanese and French scientists. However, since then, research in this area has stalled and few new datasets have been acquired. Previous studies date the formation of the NFB back to 12-10 Ma, indicating a relatively fast expansion of the NFB. Different evolution models have been proposed upon since the early 1970s. In order to verify and improve the current understanding on the tectonic evolution of NFB, we utilize a recent global bathymetry and gravity maps to map out the large-scale tectonic structures and its associated seafloor fabrics, as well as a compilation of magnetic data from the early 1980s to the start of the 2000s to lay out the magnetic anomalies of the NFB. Main features in the area include two east-west spreading centers, the Central Spreading Ridge (CSR) and the West Fiji Rift, as well as a N-S spreading belt, the Northern North Fiji Basin Spreading Belt (NNFBSB). The CSR also displays a triple junction, with a limb spreading “en echelon”, further complexifying the magnetic signal. The compilation of shipboard total magnetic field data used as comparison to existing models was acquired during a total of 114 cruises from American and French databases, with the oldest datasets being from the mid-1980s and the latest from the early 2000s. We re-processed these shipboard magnetic data and evaluated the statistical coherence with the global magnetic data, as well as an older set of aeromagnetic data. Our examination would constrain the tectonic evolution stages of the NFB further and reveal new perspectives associated with the surrounding tectonic plates.

The typical deep-sea sedimentation mechanisms are known as pelagic settling and bottom current. While many studies focus on the sedimentation in continental margins and seafloor near mid-ocean ridges, the sedimentation processes in abyssal plain, which accounts for 50% of the Earth’s surface, are only constrained by scarce data. In 2014, Korea Institute of Ocean Science and Technology (KIOST) utilized the IMI120 deep tow system configured to collect 4-kHz sub-bottom profiler (SBP) data, in order to characterize the near-seafloor geology at the Clarion-Clipperton Fracture Zone, northern Pacific Ocean. In the area, the abyssal hills and valleys are alternating in the north-south direction with a 2.5 degrees average slope under the North Pacific Deep Waters currents. Here we processed the SBP data to image near-bottom sedimentation layers based on differences in their acoustic characteristics. We applied an automatic gain control algorithm, normalized the amplitudes and then applied median filter to remove noise. We also automatically traced the reflected signals from the seafloor. Finally, we classified the processed SBP images in four categories with topography: transparent layers, strong-reflection layers, weak-reflection layers, the layers located between the transparent and strong-reflection layers showing intermediate amplitudes. Based on our classification, we can divide three main sedimentation types in the study area. First, truncated reflections or collapsed structures appear to be associated with mass wasting resulting from submarine landslides, as well as depression-like collapse structures initiated by fluid migration and then re-shaped by bottom current. Second, the transparent layers are found close to the truncated reflections, implying sediment gravity flows like turbidity flows may be responsible for such deposits. Third, the transparent layers lie in relatively flat areas. Thus, our high-resolution SBP data suggest the deep-sea geology in the study area may be actively modulated by various tectonic events and deep-sea currents.

The Korea Aerospace Research Institute(KARI) operates two geostationary satellites for Earth observation. Geo-KOMPSAT-2A(GK-2A) is one of the geostationary satellites and has been conducting Earth observations for 24 hours through Advanced Meteorological Imager (AMI) since 2018. The other geostationary satellite, Geo-KOMPSAT-2B(GK-2B), has been carrying out Earth observation missions during the daytime with Geostationary Ocean Color Imager-Ⅱ(GOCI-Ⅱ) and Geostationary Environment Monitoring Spectrometer(GEMS) since its launch in 2020. The Earth observation data of each payload is applied and utilized for each utilization institution corresponding to each payload. In addition, the applied and utilized data are released to the public for free.
By receiving and processing both geostationary satellites data, we can monitor the Earth observation images simultaneously in the KARI ground station. However, since the KARI ground station only preprocess the images, we cannot in-depth monitoring the Earth observation data obtained from each payloads. Therefore, we plan to develop a monitoring system for the Earth observation data from each payload and will show the results that combine the two satellite images.

Satellite images of the Earth Observation Satellite (EOS) can be applied for various fields such as atmosphere, environment, ocean and agriculture. Especially, the low earth orbit (LEO) satellite images with the high-resolution play an important role in studying for the earth surface and the national security. Korea Aerospace Research Institute (KARI) is currently operating five LEO satellites and three geostationary satellites. Among them, KOMPSAT-5 (KOrea Multi-Purpose SATellite-5) with SAR (Synthetic Aperture Radar) payload has an ability to detect the surface underneath the cloud during the severe weather or in the night-time. However, in case of the high-resolution EOS with the visible spectral channel only, the amount of cloud can be intensely affected to acquire the qualified satellite images. It means that the cloud pixel on the near-surface satellite imagery is disturbing to detect the surface area. In this study, in order to improve for acquiring the clear-sky satellite image, we utilize the satellite image data of both LEO and geostationary satellite in operations of KARI. Also, we study for the cloud trajectory using GOCI (Geostationary Ocean Color Imager) cloud masking data, which is applied by the parallax correction for the high accuracy. Since GOCI has a high temporal resolution over East-Asia region, we expect that GOCI cloud detection data is helpful for the LEO satellite image acquision without any cloud pixels.

The 2022 Hunga Tonga submarine volcano explosion tsunami was a unique global disaster in the Pacific Ocean. This study pointed to a region of the northwestern Pacific Ocean, Japan coastline, based on data from Numerical modeling. First, we estimated the explosion vent size based on the satellite image and the diameter was approximately 2.5 km. Next, the initial water level from the submarine explosion was calculated from the explosion vent size with a maximum height was approximately 325.403 m. The shape of the initial water level was assumed and distributed by the Gaussian function. The calculated initial water level was used to simulate tsunami using the linear long-wave model with Boussinesq type. Finally, we used the continuous wavelet transform to analyze the spectral energy of the tsunami waveform from the simulation and observation. Findings indicate that the tsunami arrived 13 hours at Chichijima Island of Japan after the explosion from the simulation result that delayed from the observed data approximately 4 hours. However, the wave amplitude from the simulation data is close to the observation data, based on the comparison in the time series. By comparing the frequency domain at Chichijima Island station, it found that the peak period of both (simulation and observation) was the same approximately 16 minutes of 1.0 sq.m/minute on spectral energy. Then, we discussed the tsunami generated by explosion energy based on spectral analysis from the wavelet. The energy from wind was smaller than the energy from the water uplifted by the explosion was approximately 5 times. The spectral energy according to the shelf, provided and identified the coastal communities prone to tsunami hazards.

A Lamb wave in the atmosphere is a type of acoustic waves traveling at about 300 m/s. Lamb waves propagate in the horizontal directions only, in the case of an isothermal atmosphere at rest. They are generated by large pressure pulses, such as volcanic eruptions, earthquakes, meteors, and atomic bombs. One of the most famous events was the 1883 eruption of Krakatau in Indonesia. The major eruption of volcano Hunga Tonga-Hunga Ha’apai in Tonga on 15 January 2022 generated the atmospheric Lamb waves, that propagated over the whole globe. The wave propagation was clearly captured by geostationary weather satellites. Because the magnitude of the event is the largest since the start of weather satellite observations, it is worth investigating. Therefore, this study attempts to visualize the Lamb waves clearly, using state-of-the-art geostationary satellite Himawari-8. In this study, one of the water vapor channels of Himawari-8 is used. The second time derivatives of 10-minute interval images clearly visualized the wave patterns. The propagation speed is estimated as 3.12 × 10² m/s, which matches the theoretical value well. Himawari’s differential images could track the waves for more than a week while the waves traveled five times round the earth. In contrast, if the time interval of the time derivative was changed to 30 minutes, which was a typical value for the previous-generation geostationary satellites, the wave patterns were not clearly visualized. The signal in the satellite imagery was consistent with the surface pressure observations in Japan.

The shallow landslide-generated debris flow on hillside catchments plays a critical role in the change of landscape features caused by natural hazards. When these debris flows occur in dams or reservoirs, they reduce the efficiency of facilities, and when they occur in residential areas, they cause many casualties and property damage. To minimize such damages, some methods can be performed through 1) installation of the warning system and 2) construction of check dam. However, in the case of rainfall-induced debris flow, preparation through a warning system is challenging because debris flows very rapidly. Therefore, to reduce the damage caused by debris flow events, the check dam needs to be installed, and for an efficient installment, a study on numerical modeling needs to figure out. Therefore, in this study, the Deb2D numerical model was used to analyze the mitigation effect through the check dam. This model is a two-dimensional debris flow simulation software based on quadtree-grid. The debris flow was simulated by Voellmy rheology, and the erosion, entrainment, and deposition processes need to be considered through the algorithm suggested in our recent study. The Raemian apartment and Galram-ri debris flow events were analyzed which occurred at Mt. Umyeon in 2011 and Gangwon-do in the Republic of Korea. We estimate the best check dam location using the most influential factor on the mitigation effect by changing the distance from the collapse zone. In addition, Spearman's rank correlation method has been used to analyze the simulation results quantitatively.

In a factory, there is a lot of equipment such as machines and electrical control panels. So, tsunami damages to not only building structure but also equipment and production after tsunami. For example, after the Great East Japan Earthquake some factories had to stop production due to machine failure. Constance et al. (2020) developed a tsunami fragility function for eight major port industries by considering the structural damage of buildings. Many tsunami damage functions for structures have been constructed after the Earthquake, but there are few studies about equipment and production stoppages at factories. Therefore, this study aims to clarify the effects of the tsunami force on the equipment damage and the shutdown period, and to develop a damage function. In addition, this study evaluate the tsunami risk of the factory at Sendai Port due to the possible huge tsunami in the future. Interviews were conducted with the companies affected by the Earthquake, the relationship between the maximum depth of inundation, the rate of damage to equipment, and the period since the disaster and the production rate were determined. And, scenario-based numerical tsunami calculations were carried out. Then, the tsunami risk of the factory was evaluated by multiplying the fragility functions. As a summary, it was shown that the damage rate of the structure may underestimate the damage. Therefore, this study shows the importance of a damage function that takes into account equipment damage. In the future, it will be possible to construct industry-specific damage functions by increasing the number of companies surveyed.

Resonance is one of the common phenomena, which commonly occurred inside the bay or continental shelf. The excitation of resonance is highly dependent to coastal topography, and can largely enhance the coastal hazard, such as tsunami. The common consequence of the tsunami resonance is that the first wave is not recorded as the largest and the prolonged duration. These are important factors to tsunami warning advisory since these can significantly determine the issued warning level and the timing of cancellation. Important issues but have not been researched thoroughly worldwide, especially on island domain of Taiwan. The primary aim of this study is to investigate the range of potential tsunami-genic earthquake scenarios that might induced resonance, and the resonance-prone region in Taiwan. For such purpose, the numerical Tsunami simulation and spectral analysis were performed. The Tsunami simulation was conducted based on three potential earthquake scenarios of M8.8 along Ryukyu Trench. And the tsunami waveforms outputted from simulation were adopted as inputs for spectral analysis. In theory, resonance might be excited when the dominant periods of spectral peaks are consistent to the fundamental mode of an embayment or a bay. On that sense, it was found that all three scenarios along Ryukyu Trench can cause tsunami resonance to Taiwan and west coast rather than east coast is risky because of the coastal topography feature of wide-shallow seafloor extended from the shoreline. These results indicated that if a tsunami generated along Ryukyu Trench, the disaster manager should be aware of the magnification of wave height and people should stay away from coast area for a longer time to ensure the safety. This study highlighted the resonance issues in Taiwan, which have not been addressed before. However, more investigation and detail analysis should be applied to fulfill the conclusion of this work.

Modern tsunami events such as the 2011 Tohoku, 2018 Palu and 2022 Tonga tsunami have demonstrated the vulnerabilities of seaports to extreme coastal events. The impact of a tsunami on ports can result in considerable economic losses beyond just physical damage. The 2011 Tohoku tsunami resulted in an estimated loss of US$ 3.4 billion in seaborne trade a day in the months following the tsunami. Any port inoperability affects trade flows in and out of the affected port and disrupts shipping routes connected to it, which then propagates throughout the rest of the maritime network. The South China Sea (SCS) basin is home to some of the world’s busiest ports. However, the threat of a tsunami hazard within the region is generally underestimated due to poor historical evidences and the lack of modern tsunami events. However, previous studies have shown that the Manila megathrust, which lines the eastern boundaries of the SCS basin, is capable of generating basin-wide tsunami waves. With many major ports concentrated in the region and most of them located in low-lying coastal areas, a tsunami event from the Manila trench could result in detrimental economic consequences beyond the affected port. The objective of this study is to develop an approach to quantify tsunami impacts on the global port network through network analyses, using a potential Manila-trench tsunami as a case-scenario.

The number of natural hazards is expected to increase due to climate change. In particular, tsunami disasters are expected to increase due to sea level rise. Studies have been conducted on tsunami hazard assessment and the impact of sea level rise. As the tsunami hazard of sea level rise increases, the amount of tsunami damage may also increase. However, little work has been done on tsunami risk assessment considering the impact of sea level rise on the economic stock damage suffered by coastal areas. In this study, tsunami numerical simulations were carried out for a part of Miyagi Prefecture in Japan under several tsunami scenarios in the coastal areas of East Japan, and different values of sea level rise were analyzed. The numerical tsunami simulation model "TUNAMI-N2" was used. The stock damage was calculated from the tsunami inundation calculation results, and the effect of sea level rise was evaluated. As a result, it was found that even tsunami scenarios that would not cause significant damage under the current sea level conditions would have significant economic risks due to sea level rise.

Transient electromagnetic methods (TEM) have a wide application in locating a resource near the surface. The characteristics of a signal originating from the earth are contaminated with the instrument impulse response unless care is taken during data acquisitions and processing. Also, the data is affected by the coupling of local noises. The coupling of noises results in poor quality of the data and model resolutions. Because of these effects, the TEM signal's decay rate decreases and results in misinterpretation of model parameters. TEM data were collected using FastSnap Telemetric equipment with a transmitter loop of 50x50 and 25x25 m in the central loop configuration nearby power lines, metal fences, buildings, and other man-made noises. Considering loop parameters, a Comparison of results in the decay curves with the two configurations highlights the noise effects. The interpretations of the data were considering these effects.

In Taiwan, the natural hazard cognition and disaster reduction education in scientific museum, it is also play important role for general people understanding due to numerous earthquakes and typhoons occurring. “National Disaster Prevention Day”, which observed at 21th September results from the 1999 Chi-Chi earthquake, reminds persons the importance of the well preparation before and after the large disaster. Therefore, the government, schools, and associated institutions conduct the outreach and education activities for disaster prevention in that day. In this study, we present the outreach activities of disaster reduction technique and disaster prevention education in National Science and Technique Museum from 2016-2011. We introduce the educational method and exhibition designs, and display and evaluate the effectiveness. Finally, we discuss the suggestions and challenges in future work.

Influenza virus, characterized by easy mutation, easy transmission, and high morbidity, which has caused many disease outbreaks around the world. These diseases have become major public health problems of global concerns. IbarraZapata identified 19 areas at high risk of influenza A (EOITA) by using the geographically weighted regression (GWR) , along with a transmission type analysis. This method obtains the spatially varying coefficient surfaces corresponding to different variables, but it does not consider time dimension. Guo employed the geographically and temporally weighted regression (GTWR) to explore the impacts of some socioeconomic and environmental factors on the mortality of chronic obstructive pulmonary disease (COPD). Although taking the time dimension into account, current GTWR ignores the spatial non-stationary of the rate of numerical variations, which in results the configuration of weight matrix is imprecise. In this study, the spatiotemporal weighted regression (STWR) was utilized to analyze the relationships between the county-level case numbers of influenza in Fuzhou and some main meteorological factors such as temperature and humidity, and social factors and NDBI from 2013 to 2019. Results show that the sharp fluctuation of the temperature difference between day and night in spring and autumn was an important factor for the increase of influenza cases in Fuzhou, and the dry environment in Minhou County and Jin'an District was more conducive to the growth and spread of influenza virus. Compared to OLS and GWR, the significant areas, that are strongly affected by socioeconomic and environmental drivers, in the spatial coefficient surfaces generated by STWR are more interpretive, especially in those areas where high influenza prevalence.

The Yangtze River Delta is the most densely populated and economically developed region in China, where the interaction mechanism between the river and the sea has been a hotspot in recent years. As a key physical phenomenon of the Yangtze River Estuary (YRE), the salinity front has an important influence on salinity distribution, sediment transport and settlement. There are three major projects around the mouth in the YRE, the North Passage Deepwater Channel Project (NPDCP), the Hengsha East Shoal Reclamation Project (HESRP) and the Nanhui East Shoal Reclamation Project (NESRP), which have different impact on salinity front due to the different locations and scales. In this study, a two dimensional hydrodynamic and salinity transport model of the YER was established by MIKE21 to study the influence of the responses of the three major projects on the horizontal salinity front in the YER. The model has been well validated by the measured data of tidal level, current speed and direction and salinity. The numerical results show that: (1) the salinity front in the North Channel (NC) shows a single-front pattern, however, the salinity fronts in the North Passage (NP), the South Passage (SP) and the North Branch (NB) show a double-front pattern. (2) the NESRP can make the main salinity front of the NP and SP move downstream, and increase main salinity front strength of the NB, NC and SP. (3) compared with the NESRP, the three joint projects can also make the main salinity front of the NP and SP move upstream, and decrease main salinity front strength of the NB, NP and SP in different degrees with those caused by the NPDCP and HESRP, due to the complex interactions of different currents in four branches and three projects.

Driven by interactive multiscale motions, the water exchange between the Pearl River Estuary (PRE) and coastal seas exhibits complex spatial structures and significant temporal variability. In this study, the exposure time (θ‾) was calculated using the adjoint method to examine the spatiotemporal characteristics of water exchange and illustrate the substance movement pathway in the PRE and the adjacent shelf. Seasonal variations in water exchange are generally determined by subtidal motion in the estuary and adjacent shelf. In summer, the θ‾ gradually increases from approximately 5 days near the lower estuary to 15 days in the upper estuary. In winter, associated with the weaker river discharge and prevailing northeasterly winds, the water exchange is suppressed and θ‾ increases to approximately 35 days in the upper estuary. Owing to the surface/bottom subtidal offshore/onshore transport in the water column, the θ‾ of the bottom water increases by 10 days compared to the surface water. Outside the estuary, the seasonally reversing shelf current and onshore transport move the shelf substance back into the PRE. The θ‾ to the southwest and northeast of the PRE is approximately 5 and 10 days in summer and winter, respectively. Temporally, the interplay between the periodic tidal motion and shelf current induces a significant intra-tidal variation of θ‾, predominantly in the middle estuary, where the water exchange is sensitive to the initial release time. The θ‾ with the initial release time of high/low tide generally has shorter/longer values. The intra-tidal variation of θ‾ is approximately three days and two weeks in summer and winter, respectively. The distinct three-dimensional structure and intra-tidal variability of water exchange illustrated in this study help to better utilize fluid motion that refreshes the water inside the estuary.

Estuarine saltwater intrusion is a dynamic process which is mainly controlled by river discharge and tide. However, an unexpected severe saltwater intrusion happened in the Yangtze estuary (YE) during the February 2014 under the normal conditions. Previous studies have not dealt with the effects of wind and wave on the saltwater intrusion in the YE. In this study, we apply a numerical model based on Delft3D to simulate the dynamics of the saltwater intrusion in the YE during the dry season (2014). The model is validated against the observed data and reproduces the characteristics of the salinity distribution. Several diagnostic model cases are conducted. Flux analysis method is used to elucidate mechanisms of the saltwater intrusion. The model results show the wind-induced flow push the high saline water southward to the mouth of the North Channel (NC) and blocked by the deep draft channel project. Amount of water flow landward to the NC and spilled over the Changxing island into the South Channel (SC). the wind forms a counterclockwise wind-induced circulation. Wind direction determines the wind-induced circulation direction in the YE. Wave increase the water mixing. It gives a marked rise in the advective salt transport combined with the wind. Ignoring the wind impact, wave has a slight influence on the saltwater intrusion.

Using Pearl River Estuary (PRE) as an example, the residence time (RT) was calculated by adjoint method to explore the dominant processes determine the water exchange and substance transport pathway in estuary-shelf system. The results showed that the spatial-temporal characteristics of water exchange is largely controlled by river discharge and tide. The RT, which indicates the time taken by the substance to leave defined region of interest, gradually increases from lower estuary to upper estuary with significant seasonal and intra-tidal variabilities. Vertically, the bottom RT is larger, particularly in the low estuary during summer because of the interactive motions of shelf current, river discharge and wind. The lowest domain-averaged RT and strongest water exchange occur in summer, while associated with the decrease of river discharge, the RT was nearly doubled during fall and winter. The tidal motion has limited influence on the mean value of RT, but induces a strong intra-tidal variability of water exchange through the interplay with the shelf. Based on the water exchange time scale in different subdomains, the substance transport pathway is revealed to be controlled by river discharge inside estuary and strong shelf current out of the estuary. The spatial structure and temporal variability of water exchange in this study indicate the influence of different forcings and help to realize substance water refresh motion in the estuary and coastal regions.

The nonlinear influence of river discharge on tides complicates the analysis of estuarine tides. To analyze the response of estuarine tides to upstream river discharge, the nonstationary tidal harmonic analysis (NS_TIDE) tool was used to hindcast the water levels along the Yangtze estuary. The results of the NS_TIDE model clearly show the time-dependent characteristics of the tidal properties (amplitudes and phases) with significant seasonal and semi-monthly variations related to the upstream river discharge and the neap-spring cycle of tides. Because of the consideration of the time-dependent tidal properties, the NS_TIDE model achieved the root-mean-square error (RMSE) values being in a range of 0.18 ~ 0.23 m along the Yangtze estuary, better than the RMSE values (0.19 ~ 0.70 m) of the classical harmonic analysis (T_TIDE) model. The tidal species reconstructed by the NS_TIDE model is further compared with the observed tidal species fully separated by the variational mode decomposition (VMD) signal analysis method. The comparison of the tidal species from the NS_TIDE and the observed tidal species clearly shows that the NS_TIDE model has much more significant errors in modelling the subtidal tides (D0) than other tidal species. This finding is further validated by the spectral analysis results again. The error series of the NS_TIDE model has the most significant energy in the D0 frequency band. Therefore, this study proves that the main errors of the NS_TIDE model come from modelling the D0 tides.

Topographic Rossby waves (TRWs) are reported to make a significant contribution to the deep-ocean current variability. On the northern South China Sea (NSCS) continental slope, TRWs with peak spectral energy at ;14.5 days are observed over about a year at deep moorings aligned east–west around the Dongsha Islands. The TRWs with a group velocity of O(10) cm/s contribute more than 40% of total bottom velocity fluctuations at the two mooring stations. The energy propagation and source are further identified using a raytracing model. The TRW energy mainly propagates westward along the NSCS continental slope with a slight downslope component. The possible energy source is upper-ocean 10–20-day fluctuations on the east side of the Dongsha Islands, which are transferred through the first baroclinic mode (i.e., the second EOF mode). These 10–20-day fluctuations in the upper ocean are associated with mesoscale eddies. However, to the west of the Dongsha Islands, the 10–20-day fluctuations in the upper ocean are too weak to effectively generate TRWs locally. This work provides an interesting insight toward understanding the NSCS deep current variability and the linkage between the upper- and deep-ocean currents.

The presence of seamounts impacts the ocean’s hydrodynamic environment. A 5-year numerical simulation is conducted over the Northwestern Pacific Ocean (NWPO) to investigate the influence of seamounts. The results are validated against satellite remote sensing data and in-situ measurements. Sensitivity experiments show that the presence of seamounts increases the complexity of the flow field, leading to enhanced relative vorticity, divergence, and strain rate. Additionally, eddy activity is enhanced while eddy propagation is suppressed. Five main physical processes that affect the hydrodynamic environment are examined around the Caiwei (CS), Weijia (WS) and Niulang (NS) seamounts. 1) Seamount-induced negative vorticities are found above the three seamounts most of the time and extend to about 600 m above the summit of the seamounts; 2) density fronts, a few kilometers in width, are present in the bottom boundary layer of the three seamounts, with accompanying jets occurring at the same locations; 3) seamount-induced topographic Rossby waves (TRWs) signals are extracted when a 7- to 10-day band-pass filter is applied to the temperature and velocity anomaly fields around CS (WS and NS) at 5,350 m (5,350 m and 4,500 m); 4) seamount-eddy interactions result in abundant eddies generated and trapped around the three seamounts; and 5) lee waves are found at the three seamounts. The systematic discussion of these physical processes near the deep seamounts provides a new understanding of how these processes enhance biological connectivity among seamounts.

Variations in the Southern Ocean (SO) mixed layer plays an important role in regulating global heat and the carbon budget, which includes multiple-scale: intraseasonal, seasonal, and interannual. The MLD variability in the SO is analyzed using a series of Argo floats from 2005 – 2017, and its response to the Southern Annular Mode (SAM) is investigated. It is demonstrated that the SO MLD decreases over the study period but decreasing rate is larger after 2011. It is also confirmed that the zonally asymmetric response of MLD to SAM is robust in both summer and winter. Wind anomalies associated with SAM dominate MLD asymmetric anomalies in the summer, but heat forcing plays a more important role in winter during SAM events.

Clarifying contributions to the surface mixed layer (SML) dissipation from dynamic processes including winds, waves, buoyancy forcing and submesoscales is of significance for quantifying exchanges between the atmosphere and the ocean. Based on two observation sections across an anticyclonic eddy in the South China Sea, the SML dissipation is investigated and the contributions from different dynamic processes are quantified. The potential vorticity indicates instability events including symmetric instability (SI), gravitational instability and centrifugal instability at the eddy. Despite of a dominant role of wind&wave-induced dissipation rates estimated at 10⁻⁵~10⁻⁴ Wmkg⁻¹, SI is highlighted with a mean estimated dissipation rate of 9.9×10⁻⁶ Wmkg⁻¹. Including the SI dissipation elevates the median rate in the SML by up to 2.4 times above the dissipation excluding SI. The SI dissipation is believed to play a role in the eddy kinetic energy budget by extracting energy from the vertical geostrophic shear of the eddy.

Mesoscale eddies are ubiquitous in the world ocean and are heavily involved in the transmission of heat, momentum, matter, and ocean mixing. The interaction between these eddies and wind stress is an important component of air-sea coupling and relevant parameterization schemes in numerical models. The current literature suggests that relative wind stress inhibits the development of eddies through negative wind work, characterizing wind as an ‘eddy killer’. However, results from a regional ocean model suggests that wind does not solely inhibit eddy generation and growth; rather, under certain conditions, wind stress can do positive work and hence, wind stress does not always kill eddies. Numerical results are validated through remote sensing observations. This work will further enhance our understanding of mesoscale air sea interaction processes.

Ocean bottom pressure (OBP) from Gravity Recovery and Climate Experiment (GRACE) has been widely used to estimate transport of the Antarctic Circumpolar Current (ACC), based on the reliability of satellite measurements. In this study, the reliability of GRACE products has been evaluated by comparisons with CPIES records in the Drake Passage. Correlations between in-situ records and 5 GRACE products (3 spherical harmonics products and 2 mascon products) all show large spatial differences: correlation coefficients are large in south and small in north. The coefficient reaches its minimum in the Local Dynamics Array (LDA) region, characterized by local high eddy kinetic energies (EKE). In addition, mascon products perform better in low EKE regions but poorly or even worse in high EKE regions. Therefore, it is necessary to use different GRACE products under different oceanic dynamic backgrounds. GRACE products could only be used to monitor the ACC when improving their poor reliabilities in high EKE regions.

The Humen and Jiaomen outlets, which locates in the eastern estuary of the Pearl River Delta, are adjacent to each other, connecting by the Fuzhou Channel (FC). In the past several decades, the FC has been developed from small branch to be the main branch of the Jiaomen outlet. Under changing environment and increasing human activities in the estuary, it is important to understand the evolution mechanism of the FC for coastal flood protection, safety of navigation etc. Existing studies have mainly focused on the division of water via the FC and its relationship with discharge of the Jiaomen outlets. However, it is still unclear on the quantitative relationship between the upstream discharge and diversion ratio, as well as the impacts of the Humen on the diversion ratio of the FC. In this study, we have constructed a schematized scaled model in a flume, representing general features of the FC, Humen and Jiaomen outlets. The upstream discharge of Humen and Jiaomen were controlled and varied independently, in order to analyze the influence of Humen on the diversion ratio of the FC. Results of the scaled model are in good agreement with the filed measurements under two different flow conditions. Experimental results suggested that the diversion ratio of the FC showed a positive relationship with the flow velocity ratio between Humen and Jiaomen, this indicates that division of water in the FC depends on both Human and Jiaomen. According to experiments, under present geomorphic situation, the critical value for the FC switches from the main branch to minor branch is the upstream velocity ratio between Humen and Jiaomen less than 0.35. Furthermore, we found that Jiaomen south channel tends to shrink and die out when the relative velocity ratio is more than 1.7.

Using laser scanner (LiDAR) to measure wave surface directly is a noval wave observing technology. Based on the operation principle of time of flight, LiDAR can capture the time-varying wave surface with high precision and spatial resolution on the surf zone and swash zone. In order to verify the accuracy of LiDAR, a flume experiment with a cement slope was conducted and test runs with different wave conditions were grouped. LiDAR is calibrationed by two different methods. One method is to use the least square method to determine tilt angle based on the static water surface point clouds. The other method is to use the improved Iterative Closest Point (ICP) algorithm to realize the real time and automatic calibration throughout the measurement process. Then, wave surface and terrain are reconstructed from the point clouds. Finally, runup is retrieved through the time series variance at every point and reflection intensity gradient on each thread. Compared with the wave gauge, runup obtained by LiDAR was very good agreement. The error of runup is less than 10%, showing the great potential of 3D LiDAR to be used to monitor wave transformation and runup in the field and laboratory.

Harbor resonance (also called harbor oscillations or seiches) refers to the trapping and amplification of the low-frequency waves inside harbors, which may interrupt the operation of docks, create excessive movements of moored ships cause unacceptable mooring forces, and even lead to the break of mooring lines. Hence, it would have significant engineering value if an effective measure could be put forward to mitigate the harbor resonance. Based on the Bragg reflection over periodic undulating topographies parallel with harbor entrance, Gao et al. (2021. Investigation on the effects of Bragg reflection on harbor oscillations. Coastal Engineering, 170: 103977) revealed for the first time its effectiveness in mitigating harbor resonance. A possible mechanism was also proposed therein. That is, the incident waves can be perfectly reflected back into the open sea because they propagate orthogonally to the periodic topographies. However, the radiated waves from the harbor entrance are mostly cylindrical. They propagate with a variable direction with the periodic topographies and are not in the optimal condition for Bragg reflection. Furthermore, the radiated waves reflected by the periodic topographies do not go back directly into the harbor, but more likely attack the surrounding coastline. Although the above explanation is reasonable, there may exist other unknown mechanisms. In other words, if the effectiveness could also be obtained when the periodic topographies are arranged in an arc layout outside the entrance, it would prove the existence of the unknown mechanisms. On the other hand, considering that the incident waves may come from any direction, the periodic topographies with an arc layout may be a better choice than those parallel with the entrance. Therefore, this present study focuses on the influences of Bragg reflection over arc periodic topographies on harbor resonance. Detailed results and findings will be reported in the conference.

The objective of this study is to specify the shoreline moving features during the non-breaking solitary wave runup process. A series of laboratory experiments with different incident solitary wave heights were conducted using a wave flume. In experiments, the still water depth was kept constant and no breaking occurred in the wave runup process. Two different slopes (10° and 45°) were considered and in the flume, the slope was divided into two transverse sections in which different bottom slope surfaces (smooth steel and rough sandpaper) were applied. Time-varying shoreline positions were recorded using high-speed video cameras, upon which the temporal shoreline moving velocity could also be estimated. Experimental results show that the temporal variation of the shoreline movement over the 10° slope is affected by the bed roughness, but not over the 45° slope. The maximum shoreline moving distance and velocity over 10° slope are obviously larger than those over 45° slope. In addition, different bed roughness shows little influence on the variation of shoreline moving velocity with respect to the normalized time, especially in the case of 45° slope. It is confirmed that the variation of the shoreline moving velocity presents different characteristics over two different slopes. For the small slope, the acceleration process of shoreline moving velocity is short and the deceleration process is long. With the increase of the incident wave height, the peak velocity appears slightly early. For the large slope situation, however, it shows an   opposite scenario with a long acceleration process and a relatively short deceleration process. For which, variation of the wave height has little effect on the occurrence time of the peak velocity. These phenomena could also be confirmed after considering observations from other existing experiments.

Coastal bridges are widely constructed due to their high efficiency in connecting cities. Extensive investigations have been carried out focusing on the waves and current forces on bridge decks and local scour around piers. However, the effects of bridges on hydrodynamic of a coastal bay, which are related to coastal sediment transport, water quality and marine ecology, are seldom studied. This paper aims to study the effects of bridge piers on the hydrodynamics of a coast bay based on the case of Hangzhou Bay, China. A numerical software of Delft-3D was used in modeling the waves and two-dimensional tidal current. The model was verified with the coast topography, waves heights, flow velocity that were measured or monitored in field. Cases of both non-bridge-existing and bridge-existing in once a year, 10-years, 50-year, 100-year and 200-year waves and current conditions are to be simulated and analyzed. Results of the varied waves and flow fields under the influences of constructed bridges are believed to be meaningful on the Coastal environment protection.

The slope area northeast of Taiwan Island in the southern East China Sea (ECS) is well known as a hotspot for both internal tides and internal solitary waves (ISWs) despite uncertainties regarding their specific source and generation mechanism. This study investigates the generation and evolution processes of internal tides and ISWs northeast of Taiwan Island in the southern ECS, based on a super-high resolution and non-hydrostatic numerical simulation. ISWs create a complex spatial pattern in both satellite images and our simulation, with wave propagation in multiple directions, including onshore and offshore. These ISWs, with the largest amplitudes reaching ~50 m, are mainly generated by two mechanisms: local tide-topography interactions and disintegration of internal tides remotely generated over I-Lan Ridge. Locally generated ISWs propagate in various directions owing to the complex topography, whereas ISWs generated by the disintegration of remote internal tides are more consistent in their pathways. The internal tides remotely generated over I-Lan Ridge propagate northward to the Okinawa Trough and steepen nonlinearly into ISWs ~80 km north of I-Lan Ridge, before finally reaching the continental shelf region. Furthermore, the Kuroshio Current is important for modulating both the propagation and evolution of the internal tides and ISWs. Most of the radiated baroclinic tidal energy dissipates over the double-canyon region, where strong mixing occurs.

 In Hiroshima Bay, Seto Inland Sea (SIS), the Itsukushima shrine is located. This high cultural value structure is preserved as one of the World Heritage Sites in Japan. The shrine was built offshore, 30 cm above the highest tide to prevent it from being submerged. However, from 1991 to 2012, the shrine has been submerged 6 times during September due to internal surges. This surge called an abnormal tide was caused by a remote typhoon passing through the far east off the Hiroshima Bay. To study the abnormal tide case that occurred on September 29 in 2011, we set a numerical ocean circulation model. The model used is Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM), which supports unstructured grids. As an elevation forcing at the open boundary, with tidal components, nontidal components from storm surges and basin-scale resonance of SIS were considered also. Subtidal components of surface elevation in the northern part of the bay decreased due to northerly winds when the typhoon passed east off the bay. After 7-8 days of typhoon passage, the component increased abnormally in the northern part of the bay. From transects of water density, disturbed stratifications were found after typhoon passage. It means the seawater was prone to form internal waves due to a remote-typhoon-induced surface shear. From the kinetic energy of internal waves, propagation of the wave after the typhoon was found. Sensitivity tests with various scales of typhoon were performed and the test results revealed a positive relationship between the abnormal tide level and typhoon intensity to some extent. The results can be generally applied to a semi-closed bay or closed water body for internal wave generations and propagation under specific meteorological conditions, and used for safety and disaster management for not only shrines but also coastal structures close to the shoreline.

Understanding how the atmospheric drivers impact the swell trends assist adaptation effort for islands where coastal flooding can lead to destructive impacts. We aim to explain the relationship between the generation characteristics of the strong cyclones and northwest swells hitting the Hawaiian Islands using modeling and in situ observations. The strong extratropical cyclones are identified using minimum mean sea level pressure and geopotential height and maximum relative vorticity from the hourly forecast dataset of NCEP Climate Forecast System six-hourly Reanalysis. The sea state hindcast is obtained from the third-generation nested wave model WAVEWATCH III using wind field data 10 m above the surface level. The swells are separated, and their characteristics during the high wave energy season are obtained on the grids surrounding the island in hourly intervals. We examined the strong extratropical cyclones trends in cyclogenesis location and their storm identification characteristics, and swell significant wave height and peak period in decadal (2007-2017) and overall (1979-2017) perspectives. Our results show a rise in the number and intensity of strong extratropical cyclones during 1979–2017, and this increase accelerates during 2007–2017. We found a significant amount of swells generated by the strong extratropical cyclones (almost one-third) of the Hawaiian Islands during 1979–2017 and one-quarter of it during 2007–2017.​ The deseasonalized trend analysis on maximum daily significant wave height and peak period slightly decreased during 1979–2017; however, it significantly increased during 2007–2017. Our trend patterns align with annual and seasonal fluctuations of storm cycles and El Niño-Southern Oscillation fluctuations and intensity.

Bangladesh is one of the most exposed countries in the world to typhoons. Meanwhile, due to its unique topography, the storm-surge at the coastal area is very significant, especially in the Chittagong region. This study simulates the typhoon-driven storm-surge using the hydrodynamic model - Mike 21 HD, considering the synchronized variation of tidal levels. Based on the JTWC typhoon information in the Northern Indian Ocean, several typical tropical storms passing through the Chittagong within a 200 km search radius for the period from 1980 to 2015 are selected for this study. The information from the selected typical tropical storm events are used to generate the wind fields through the Young and Sobey Typhoon Empirical Model, which are then acting as driving forces for the subsequent HD modelling. Model results of the storm-surge time series, as well as water level time series are extracted from the numerical simulation, after which extreme value analysis is conducted to estimate the extreme storm-surge and water level conditions corresponding to different return periods.

On August 14, 2021, a tragic incident of 11 drownings occurred on the southeastern coasts of China East Sea. The most suspected cause of the drownings is rip current, which is a strong seaward water jet that can sweep unexpected swimmers into deep water. Though this tragic incident had increased public awareness of the rip current hazard, the causes and nearshore processes that result in the formation of rip currents during the reported incident remain less understood. In this talk, we will investigate the hydrodynamic processes of rip current formation at the incident beach by reconstructing the event through integrated atmospheric-hydrodynamic modeling. The numerical simulation aims to reveal the occurrence of rip currents and depict circulation patterns of rip currents with strong offshore flows to sweep people to the deep water. A coupled wave-current model SCHISM-WWM III is employed. Detailed nearshore mesh with the high-resolution grid at O(1m) along the beach coastline is constructed to resolve the rip currents and wave-induced vortices. Atmospheric pressure and wind fields as atmospheric forcing to the model are constructed by compiling the ERA5 reanalysis data and local metrological observations. Boundary conditions are created using observation data of wind waves and tidal water levels which are compiled from nearby stations. In particular, the roles of wave-current interactions including wave breaking induced vortices and shear instability of wave-driven longshore currents which are key processes to the generation of rip currents are examined. In short, the numerical simulation of the 2021 rip current event will reveal critical information about the generation conditions and evolution processes of rip currents at a typical sandy beach in China southeastern coasts. This study will also provide a crucial beach safety message to beachgoers and managers of coastal communities.

Coast and ocean environments are viewed as indispensable conditions that help life in the upland areas. Humans rely on the ecological services offered in these environments. However, humans are also the cause of the depletion of resources due to over-exploitation. With this study, an expert-driven coastal and ocean health index (CoZHI) framework is developed with an aim to assess the environmental sustainability status of the Island Countries. The principle of the coastal and ocean zone’s management under the CoZHI framework is to maintain a healthy environment where humans and nature co-exist harmoniously hence, the CoZHI framework is developed based on the environmental views of the decision-makers. Environmental health status is assessed in terms of the identified ten indicators namely, natural products, fisheries, biodiversity, marine culture, tourism, recreation, carbon storage, clean water, coastal livelihood, sense of place, including the changes that might happen in the future caused by the effects of global warming. The identification of the weight of the indicators for the CoZHI score can be done subjectively using expert-driven multicriteria analysis. Furthermore, this study also shows that the generation of the CoZHI framework is adaptive to the perceptions and knowledge of the decision-makers. Thus, this study provides a geographically relevant understanding of the state of the co-existence of humans living in the coastal zone environment.

Since the successful Venusian Orbiter Insertion of Akatsuki in December 2015, Long Infrared Camera (LIR) onboard Akatsuki has achieved continuous observation of temperature at the Venusian upper cloud level for almost 10 Venusian years. For such a long-term observation, validation of stability of sensor performance and calibration are key issues for providing reliable data products. In early observation period of LIR, it was found that temperature of LIR’s sunshade baffle affects observed Venus temperature in LIR images. The effect was modeled and canceled by monitoring the baffle temperature (Fukuhara et al., 2016). On the other hand, even after the calibration of the baffle temperature effect, observed temperature in LIR images has shown gradual increasing (e.g., 20 K increasing in the lower limit of observable temperature from 2015 to 2022). Based on bolometer characteristics, the gradual temperature increase can be caused by LIR’s sensitivity degradation. From deep space observations for calibration, the magnitude of the sensitivity degradation was measured as ~1 %/year. After correcting the degradation effect, the gradual increasing of the temperature was significantly reduced. While the absolute value of measured temperature requires calibration, temperature resolution (0.3 K, Fukuhara et al., 2011) has been stable during the mission period. As LIR is the first sensor observing Venus temperature globally for such the long-term period, LIR has provided many new observational insights of Venusian atmosphere, such as the discovery of global scale mountain waves (Fukuhara et al., 2016) and their location and local time dependence (Kouyama et al., 2017), revealing the global structure of thermal tides in the upper cloud layer from temperature and wind perturbations (Kouyama et al., 2019; Fukuya et al., 2021). In addition, thanks to the long-term calibration, we found a long-term variation in temperature that may correlate with zonal mean zonal wind speed.

The 2-um infrared camera (IR2) onboard Akatsuki observed a remarkable cloud feature in the Venus' night-side disk, a sharp discontinuity of cloud opacity which subtends latitudinally to some thousands of km (Peralta et al., 2020). Though obvious and seemingly common in the Venus' atmosphere as similar features can be identified in imagery since the beginning of the night-side observations (Allen and Crawford, 1984), the mechanism of this emormous cloud cover (ECC) has not yet been explained.
To characterize this ECC (aerosol size parameters and column numbers), we have analyzed the Akatsuki/IR2 data, as well as the Venus Express/VIRTIS data. Six sets of the Akatsuki/IR2 data (MM-DD = 03-27, 07-22, 08-09, 08-18, 08-27, and 09-06) are measurable with varying photometric uncertainties, due to contaminations from the intense day crescent. Seven VEx/VIRTIS data, as tabulated in Peralta et al. (2020), are also measured by the consistent method with that for IR2 data. A reference region, which is just west of the discontinuity and is seemingly not affected by the ECC, is defined as the background cloud (BC) region. Radiances at the BC and the ECC regions are measured for two IR2 filter passbands (1.735 and 2.26 um). They are plotted in the correlation plot (radiance at 2.26 um in horizontal axis and radiance at 1.735 um in vertical axis). The BC-to-ECC slope can be used to infer the aerosol size and abundance that changes the BC region to the ECC region. Comparison of obtained characteristics of the ECC for different observing times will be presented and implication to the possible mechanism of this large-scale phenomenon will be discussed.

Angular momentum transport due to the thermal tides excited by the absorption of the solar heating in the Venus cloud layer is regarded as one of the most likely mechanisms to maintain the Venus atmospheric super-rotation. Some theoretical studies about the thermal tides indicate that the vertically propagating thermal tides transport the eastward momentum upward and downward from the cloud layer, thereby accelerating the cloud-level atmosphere westward because of the conservation of angular momentum. In particular, the downward propagating thermal tides are thought to be important in these studies: it is possible that they propagate downward to the ground and transport eastward momentum to the atmosphere near the ground, and then this momentum is dissipated by the surface friction. As a result, it is expected that the atmospheric super-rotation can be maintained by the supply of the net angular momentum from the solid body. Therefore, it is essential to confirm the downward propagation of thermal tides below the clouds to examine the validity of the theoretical studies. In this study, we obtained the local time-height distributions of the temperature fluctuations associated with the thermal tides at 40–90 km altitudes in the equatorial region by using the Akatsuki radio occultation data. We detected the zonal wavenumber-1 (diurnal tide) and -2 (semi-diurnal tide) components from the temperature fluctuations. The phases of the diurnal and semi-diurnal tides tilt toward earlier local times with increasing (decreasing) altitude above (below) ~60 km and 50–55 km altitudes, respectively. This suggests that the thermal tides propagate upward (downward) above (below) these altitudes; it is the first discovery to detect the downward propagation of the thermal tides. We also compared the observations with a Venus general circulation model named “AFES-Venus” and found that the simulated vertical structures are qualitatively consistent with the observation.

Akasuki has been in operation since its orbital insertion in Dec 2015, and UVI onboard Akatsuki has been nearly continuously observing dayside UV radiance from around the cloud top. Horinouchi et al (2018) documented the mean winds and their variations obtained over the first ~1.5 years. Here, we update the study with the observation until 2021, and we further report long-term statistics of planetary-scale waves, updating the case study of Imai et al (2019). The topics include hemispheric asymmetry and its variability, long-term and low-frequency variations of the superrotation, thermal tides, and statistics of the Rossby and the equatorial Kelvin waves. Some aspects of the super-rotation dynamics are discussed. References: Horinouchi, T., et al., 2018: https://doi.org/10.1186/s40623-017-0775-3Imai, M., et al., 2019: https://doi.org/10.1029/2019JE006065.

Images of Venusian clouds at ultraviolet wavelengths frequently exhibit small-scale (<1000 km) cellular structures at low latitudes. The origin of these structures has been unclear, and the condition where they are enhanced is unknown. Here we explore the temporal variation of the contrast of small-scale structures using ultraviolet images taken by UVI onboard Akatsuki spacecraft to search for possible periodicities. The 283-nm channel of UVI provide SO2 distribution at the cloud top and the 365-nm channel visualizes UV absorbers of unknown composition. Periodicities of planetary-scale UV contrasts associated with planetary-scale waves were also investigated to study the relationship between small-scale structures and planetary-scale waves.
We discovered quasi-periodical oscillations of the standard deviation of small-scale UV structures with periods of around 4 and 5 Earth days. Planetary-scale oscillations with similar periods were also seen. This apparent synchronization suggests that the generation of small-scale structures is influenced by planetary-scale waves. We also found that small-scale structures tend to be enhanced when the UV albedo decreases in the course of the propagation of planetary-scale waves. This correlation might suggest that the heating of clouds by solar radiation feeds small-scale convection, which appear as cellular structures.

We investigated the three-dimensional structure of thermal tides in the Venus atmosphere excited by the solar heating in the cloud layer by using a GCM named as AFES-Venus. Though the results were roughly consistent with past observation, there remains the discrepancy in the zonal wind, meridional wind and temperature fields associated with thermal tide between the numerical study and recent observational results by Akatsuki. In order to resolve the discrepancy, we investigated how the thermal tides are affected by the static stability in and above the upper cloud layer by using three different distributions of the static stability. The results show that the vertical structure of the semidiurnal tide, which propagates vertically, is strongly affected by the static stability, while that of the diurnal tide is not so affected by it. The horizontal distribution of the thermal tides is improved in the case where the realistic stability distribution, which is consistent with that derived by radio occultation measurements, is reproduced. The meridional angular momentum flux associated with the thermal tides is equatorward in low latitudes near the altitude where the equatorial zonal-mean wind takes its maximum. This result is consistent with the recent Akatsuki UVI observations, suggesting that the thermal tides could contribute to the meridional circulation mechanism. In the most realistic case, the zonal-mean zonal wind is effectively accelerated at rates of 0.2–0.5 ms⁻¹ day⁻¹ in low latitudes at altitudes of 52–76 km by both the meridional and vertical angular momentum transports. The thermal tides also induce significant meridional heat flux, which cannot be ignored in the dynamical effect on the zonal-mean zonal wind.

To understand the dynamics of Venus’s atmosphere, Bred Vector (BV) analysis is applied to the Venus atmospheric general circulation model “AFES-Venus” (Sugimoto et al. 2014). BV analysis identifies the growing modes of the system and therefore the unstable regions (Toth and Kalnay 1993, 1997). It has been used in the studies of the earth and Martian atmospheres (Greybush et al. 2013) to investigate the dynamics of the atmosphere in different seasons and regions. We first produced a 5-year free run of the AFES-Venus model initialized from an idealized super-rotation zonal wind profile at 0 year. The states on January 01 and September 01 in the 5^th year were used as the initial conditions for the control run and the perturbed run, respectively. The norm of the BV is defined by the temperature norm from 60 km to 80 km altitude of the atmosphere with more active dynamics. At every rescaling interval, if the norm is bigger than the prescribed rescaling norm, the BV is rescaled to the rescaling norm. The rescaling interval and norm are the two parameters of the breeding cycle. Different combinations of the parameters were tested. The norm decayed at the beginning, then it started capturing the growing modes after 6~15 Earth days. The growth rate remains stable throughout the following Venus year without significant seasonal variability. In addition, the growth rate is higher when the rescaling norm is smaller, which indicates that the faster growing mode of the system is dominant in this case. In comparison, there are seasonal variabilities of the growth and decay modes in the Martian atmosphere. Further BV analysis will be conducted to study the dynamics of the thermal tide, super-rotation, and other important features of Venus’s atmosphere.

Based on the state-of-the-art Venus Global Climate Model (GCM) developed by our team, we have generated a Venus Climate Database (VCD) (see http://www-venus.lmd.jussieu.fr/). This tool was developed with funding from ESA in the context of the preparation of the upcoming EnVision mission.
The VCD provides mean values and statistics of the main meteorological variables (atmospheric temperature, density, pressure and winds) as well as atmospheric composition and related physical fields. It extends from the surface up to and including the thermosphere (~250km). The database contains high resolution temporal outputs (using 24 hourly bins) enabling a good representation of the diurnal evolution of quantities over a climatological Venusian day.
As the goal of the VCD is to provide information about the state of the Venusian atmosphere, various realistic settings have been used to run a series of baseline GCM simulations, namely:
- Simulations using various Extreme UltraViolet (EUV) input from the Sun, as this forcing influences significantly the thermosphere (~120km and above).
- Some supplementary simulations with extreme values of UV cloud albedo, to bracket the state of the atmosphere below the thermosphere.
In addition to the aforementioned VCD scenarios, the following features are available:
- A "high resolution" mode based on a high resolution topography map (at 23 pixels/degree).
- Access to the Venusian intra-hour variability (RMS) of main meteorological variables, as well as the Venusian day-to-day variability thereof.
- The possibility to add perturbations to the climatological fields in order to generate realistic weather conditions.
The VCD is distributed as (i) a main Fortran subroutine that users can interface and directly call from their own programs, interfaces to call this gateway routine using other programming languages (e.g. C, Python, IDL, Matlab, ...) are also provided; (ii) a web interface, for quick looks (http://www-venus.lmd.jussieu.fr).

The quadrupole mass spectrometer of the Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) Curiosity rover conducts periodic sampling and measurement of the volume mixing ratios (VMRs) of CO₂, N₂, Ar, O₂ and CO in the ambient atmosphere. Over the observation period spanning Mars Years 31–34, the O₂ VMR was found to exhibit significant variation. Even after accounting for transport effects driven by the seasonal condensation and sublimation of CO₂ at the poles that also affect the N₂ and Ar VMRs, the O₂ VMR has residual variations of ~20%. With the photochemical lifetime of O₂ being >10 years, variations of such magnitude on a seasonal and interannual timescale are unexpected. Variations of similar relative magnitudes have also been observed in column-averaged O₂ VMR from MSL’s ChemCam spectrometer. These variations are unlikely to be driven by atmospheric photochemistry. The O₂ variations are at a larger magnitude than the total VMR of minor O-containing species, and with interannual variations not correlated with UV radiation fluxes measured by MSL’s Rover Environmental Monitoring Station (REMS), photodissociation rates of CO₂ and H₂O are not expected to vary significantly either. Unlike atmospheric processes which act on a global or regional scale, surface processes can be more spatially limited. The smaller spatial scale implies that we do not need a mechanism for drawing out the O₂ from the atmosphere, and the O₂ decreases can simply be explained by mixing with the background atmosphere. Nonetheless, a surface reservoir and a mechanism for release from the reservoir have to be identified, as well as a mechanism for reservoir recharge. We evaluate the potential for reservoirs of perchlorates, H₂O₂ and brines to act as O₂ sources that can release O₂ under Martian conditions.

The MAVEN NGIMS team produces the computation of Ar scale height and temperature at ~200 km. Members of the MAVEN team have used various methods to compute scale heights leading to significant variations in values depending on fits and techniques within a few orbits even. We compute Ar scale height as it is most stable and reacts least with the instrument. The NGIMS team has chosen to expand these fitting techniques to include fitted scale heights for CO₂, N₂, CO, and O. Having compared multiple techniques, the method found to be most reliable for most conditions was determined to be a simple fit method by fitting the slope of altitude vs log(density) is -1/H where H is the scale height of the atmosphere for each species. This is between the homeopause and the exobase, and each species will have a different scale height. For the primary and first two extended missions (2014-2019) the apoapsis was ~6500km and periapsis ~150km. In April 2019 MAVEN performed an extended deep dip campaign to lower the apoapsis to ~4500km. A more fuel efficient and stable orbit required that MAVEN raise the periapsis to ~180-220km which occurred in August of 2020. NGIMS is optimized for observation between ~300-125km for neutral and ion species. Post-periapsis raise NGIMS has continued to conduct the same science operations as before including nominal science. While the NGIMS data does have more statistical noise at the higher altitudes, there is still substantial signal over the background. In this higher altitude region we have had to make considerable changes to our density and scale height computations in order to accommodate the lower range of measurement. This paper covers previous methods of scale height and density computations and compensations made post periapsis raise.

Using the Neutral Gas and Ion Spectrometer (NGIMS) on the Mars Atmosphere Volatile and Evolution spacecraft (MAVEN) we collected data from Mars Year (My) 32, 34, and 35 to examine the He bulge during the northern winter solstice (Ls ~200-280) specifically focusing on the effects from the planet encircling dust event (PEDE-2018). The MAVEN orbit precesses around Mars allowing for a variety of latitude and local time observations throughout the Martian year, for this reason, we selected He observations from My 32 and My 35, we make a comparison for a non-dust year to the PEDE observations in My 34. NGIMS observations during the PEDE during My34 are considerably lower that observations during My 32 and My 35 indicating the PEDE directly impacted the He bulge. Updates in modeling indicate changes in circulation and winds that caused He to shift further north and dawn-ward than MAVEN was able to observe.

Mars Gravity waves generated by non-orographic sources have dramatic impacts on the atmospheric wind fields higher than ~40 km, result in heating/cooling of the atmospheric temperature by altering the circulation. A non-orographic gravity waves (nonoro-GW) scheme which accounts for these in a stochastic way was implemented in the LMD-MGCM and applied from the surface to 120 km by Gilli et al. 2020.
We have extended this scheme into the thermosphere (i.e. up to the exosphere ~300 km) which implied revisiting the scheme and adopting a new set of parameters. In summary, the main results to be presented and discussed at AOGS include:
1) the description of the improvements to the original parameterization that have been made, and which ensure that the scheme is now working when extended into the upper atmosphere.
2) The analysis of the thermal structure below 100 km simulated by the GCM with the nonoro-GW scheme parametrization, which is found to be highly consistent with MCS observations.
3) A description of recent improvements in the LMD-MGCM dust/water cycle model, which when coupled to the non-oro-GW scheme tends to correct some known biases in the modeled thermal tides amplitudes and phases.
4) An analysis of the impact of the nonoro-GW parametrization on the thermospheric winds and density (temperature), and how the later compares with MAVEN observations.

The NEXT generation of Iridium satellites were launched and commissioned from January 2017 through January 2019 and the original “Block 1” satellites were decommissioned. Magnetic field data from the 75 NEXT satellites required on-orbit calibration with engineering telemetry to calibrate satellite-generated magnetic fields specific to each satellite. New pre-processing algorithms and software have been developed to derive corrected magnetic field data from all 66 satellites in the NEXT communication network. AMPERE products using exclusively NEXT data are now available for the period from March 2019 to the present. In addition, new algorithms developed to select the optimal combination of available Block 1 and NEXT satellites during the transition phase allow seamless processing for producing AMPERE data from a mix of Block 1 and NEXT satellites. The magnetic field residuals have a noise level of ~30 nT rms for NEXT, whereas for Block 1 the noise was ~70 nT rms, consistent with the substantially improved attitude knowledge accuracy for NEXT. One of many applications of this global, continuous data set is the study of asymmetries in ionospheric electrodynamics between the northern and southern hemispheres. The lower noise of NEXT data allow study of the dynamics of Birkeland currents at lower levels than previously possible. Using AMPERE products from NEXT, we present analysis of the diurnal variation in total Birkeland current and the distributions of these currents as they change with season. Both the diurnal total currents and distributions exhibit a strong dependence on solar-EUV ionospheric conductance. For active times, the hemispheric asymmetries are greatly reduced and the total currents and distributions have comparatively little dependence on time of day or on season. The results suggest that particle precipitation and convection increasingly dominate the ionospheric conductance over the EUV sources thereby muting hemispheric asymmetries in the currents.

The Earth’s magnetosphere is the outermost layer of the geospace system deflecting energetic charged particles from the Sun and solar wind. The solar wind has major impacts on the Earth’s magnetosphere, but it is unclear whether the same holds for solar flares—a sudden eruption of electromagnetic radiation on the Sun. Here we use a recently developed whole geospace model combined with observational data from the 6 September 2017 X9.3 solar flare event to reveal solar flare effects on magnetospheric dynamics and on the electrodynamic coupling between the magnetosphere and its adjacent ionosphere, the ionized part of Earth’s upper atmosphere. We observe a rapid and large increase in flare-induced photoionization of the polar ionospheric E-region at altitudes between 90 km and 150 km. This reduces the efficiency of mechanical energy conversion in the dayside solar wind–magnetosphere interaction, resulting in less Joule heating of the Earth’s upper atmosphere, a reconfiguration of magnetosphere convection, as well as changes in dayside and nightside auroral precipitation. This work thus demonstrates that solar flare effects extend throughout the geospace via electrodynamic coupling, and are not limited—as previously believed—to the atmospheric region where radiation energy is absorbed.

Thin-layer approximation has been widely used for considering the magnetosphere and the ionosphere. In reality, the Hall current flows at lower altitudes than the Pedersen current does, implying that the current closure is 3-dimensional. However, such a 3-D current closure is not well known. We have investigated the 3-D current closure of field-aligned currents (FACs) in the polar ionosphere by using a simplified three-dimensional Hall-magnetohydrodynamics simulation. An electric field perturbation is applied to the high-altitude magnetosphere to excite Alfven waves. The Alfven waves propagate downward, and proceeds into the region where ion-neutral collision is significant. When the electron density was initially uniform in the horizontal direction, most of the FACs are connected with the Pedersen current due to electrostatic processes. Some of them are connected with the Hall current due to inductive processes. When the electron density was initially enhanced in a longitudinally elongated region (high-density band), overflow of the Hall current takes place near the edge of the high-density band. This situation may correspond to the Cowling channel. We found additional, localized FACs appear to bridge between the Pedersen current layer (high altitude) and the Hall current layer (low altitude). The 3-D current lines (which were obtained by line integral of the current density vector) are fully different from those obtained by the traditional thin-layer assumption. In the full 3-D simulation, current lines flowing in the Hall layer can pass underneath the current flowing in the Pedersen layer. Such “intersection” is not allowed in the thin-layer assumption. We believe that the 3-D model offers advantages for fully understanding the closure of the FACs together with the current closure on the magnetospheric side.

We conducted a statistical analysis of the nighttime neutral wind responses for four different geomagnetic activity levels with a particular interest on the effects of ion drag. Neutral winds between 90--125 km derived from the observations made by Poker Flat Incoherent Scatter Radar (PFISR) during the winter from 2010-2019 are collected and divided into 4 different groups according to the disturbance level indicated by the geomagnetic perturbations recorded by a local magnetometer. Our analysis showed that (1) meridional wind shows increasing effects of ion drag in both evening and postmidnight sectors above 110 km with the increase of geomagnetic activity. The largely enhanced equatorward wind in the postmidnight is consistent with previous studies. (2) Zonal wind above 110 km shows increasing effects of ion drag in the evening sector and shows effects from a combination of ion drag and other factors in the postmidnight. Consistent westward winds above 120 km, which depart from the prediction of the pure effects of Pedersen component of the ion drag, are observed. This indicates that other factors such as Joule heating, changes in background winds, which interplay with the ion drag and create a complex scenario, should be considered. 

In this study, the impact of improving soft (0.1-1 keV) electron precipitation in the whole auroral zone on the F-region neutral mass density has been evaluated using the Global Ionosphere Thermosphere Model (GITM). Two types of electron energy spectra having the same total energy flux and average energy but different spectral shapes have been used to specify the electron precipitation in GITM. One is the typically assumed Maxwellian spectrum and the other is from a novel empirical model, Auroral Spectrum and High-Latitude Electric field variabilitY (ASHLEY), which substantially improves soft electron precipitation specifications over the Maxwellian spectrum. Data-model comparisons indicate that the storm-time F-region neutral mass density was markedly better estimated if the soft electron precipitation is better specified. This study reveals the importance of accurate soft electron precipitation specification in the whole auroral zone to improving the F-region neutral mass density estimations in GITM. 

Polar UVI and an all-sky camera at Longyearbyen contemporaneously detected an aurora with vortex structure (auroral spiral) on 10^th January 1997. Particularly, from space, the auroral spiral was observed as a small spot in the poleward region of the main aurora oval near midnight, which was formed after substorm-associated auroral bulge subsided and several poleward elongated auroral streaks appeared during the late substorm recovery phase. To pursue the spiral source region in the magnetotail, we try to trace each UVI image along the field line to the magnetic equator using an empirical geomagnetic field model (Tsyganenko 96 model). Interestingly, the magnetotail region corresponding to the auroral spiral broadly covered from X_gsm ~ -40 to -70 R_E at Y_gsm ~ 8 to 12 R_E. Appearance of this auroral spiral may suggest that plasmas are transported from the magnetotail to ionosphere extensively and actively even during the late substorm recovery phase. To further discuss a possible formation process of the auroral spiral based on a global MagnetoHydroDynamic (MHD) simulation of the Open Geospace General Circulation Model (OPEN-GGCM), which is served in the Community Coordinated Modeling Center (CCMC). We tried to reproduce the ionospheric field-aligned current structures of the aurora spiral and corresponding magnetotail conditions, which are represented with magnetic field, plasma velocity, number density, magnetic and plasma pressures. However, in this global MHD model, the auroral spiral cannot be reproduced in the ionosphere, and associated significant magnetic field and plasma variations cannot also be found in the magnetotail, suggesting that the spiral formation mechanism might not be explained by plasma processes within a framework of MHD dynamics. In this paper, we mainly discuss the auroral morphological changes before and during the auroral spiral in the late substorm recovery phase but try to consider a possible spiral formation process.

Magnetic reconnection is a significant driver of energetic particles in flares both on the sun and the broader universe. Single x-line models fail to explain the large number of energetic electrons seen in flares. However, simulations reveal that reconnection becomes turbulent in the flare environment, consistent with observations of non-thermal broadening of spectral lines. Magnetic energy release and particle acceleration therefore take place in a multi-x-line environment. A major surprise is that the energy gain of the most energetic electrons is dominated by Fermi reflection in growing and merging magnetic flux ropes rather than parallel electric fields. The implication is that the kinetic scale boundary layers that control the parallel electric field are not important in flare energy release where the separation of scales can reach 10^{10}. A new computational model, {\it kglobal}, has been developed that blends MHD dynamics with electron particles but eliminates all kinetic scales. Feedback of the energetic electrons on the MHD is included. Simulations of reconnection in a macro-scale system reveal electron powerlaw distribution that extend nearly three decades in energy and that the dominant control parameter is the ambient out-of-plane magnetic field. PIC models fail to produce such spectra because of inadequate separation of scales. The electron spectral indices match those measured by RHESSI and EOVSA for the September 10, 2017, flare. Major challenges are to understand how relativistic electrons are "confined" as they gain significant energy. The results also suggest that modeling of particle acceleration in realistic macro-scale flare geometry will be possible.

Solar Orbiter, a joint ESA/NASA mission, is to study the Sun and inner heliosphere in greater detail than ever before. Launched in February 2000, Solar Orbiter already completed its first two orbits, reaching perihelion of 0.5 au from the Sun in June 2000 and February 2021. Understanding the physical processes operating in Solar Energetic Particle (SEP) events is a major goal of the Solar Orbiter mission because of the importance of acceleration processes in solar system and astrophysical sites, and because of the potential impact of these events on space hardware. The Energetic Particle Detector (EPD) investigation on Solar Orbiter is a suite of four different sensors plus the instrument control unit to measure the energetic particles from slightly above solar wind energies to hundreds of MeV/nucleon. We report here data from Suprathermal Ion Spectrograph (SIS) sensor of the EPD that covers the energy range of 0.1 – 10 MeV/nucleon for H-Fe with high mass resolution during the first orbit. SIS observed several ³He-rich SEP events inside of 1 au. Even though these events were small, their spectral forms, ³He content, and association with type III bursts convincingly identifies them as ³He-rich SEP events with properties similar to those previously observed at 1 au. 

Solar energetic electron (SEE) events are one of the most common particle acceleration phenomena occurring at the Sun, and their energy spectrum reflects the crucial information on the solar electron acceleration. Here we present a statistical survey of the energy spectrum of 427 SEE events at energies from ≤ 4.2 keV to ≥ 108 keV measured by WIND/3DP from 1994 December through 2019 December. Among the 427 SEE events, the energy spectrum can be classified into three types: 335 are power-law (PL) including 253 downward double-power-law events, 39 upward double-power-law events and 43 single-power-law events, 33 are Ellison-Ramaty (ER), and 59 are log-parabola (LP). The break energy E_B of downward DPL also shows a double-peak distribution: the first peak at ∼6 keV and the second peak at ∼70 keV.

Observations from the Large Area Telescope (LAT) on board the Fermi mission have revealed that many sustained gamma-ray emission (SGRE) events from the Sun are associated with soft-spectrum solar energetic particle (SEP) events. Under the paradigm that shocks driven by coronal mass ejections (CMEs) are the source of high-energy particles that diffuse to the solar surface, interact with the ambient particles, and produce neutral pions that decay into SGRE. The soft-spectrum SEP events indicate the lack of high-energy particles (>300 MeV), contradicting the shock paradigm. We examine the source location of the associated CMEs and find that the soft spectrum results from the lack of magnetic connectivity between the shock nose and an Earth observer because high-energy particles are accelerated near the shock nose, while low-energy particles are accelerated from all over the shock surface. The lack of connectivity is indicated by the ecliptic distance of the source locations that is much larger than that of CMEs producing ground level enhancement (GLE) in SEP events. In other words, the SGRE-associated CMEs do produce high-energy particles, but these particles do not reach an Earth observer. The results confirm the idea that the shock surface area over which particles are accelerated is energy dependent.

With the onset of solar maximum and the likely increased prevalence of interplanetary shock waves, Parker Solar Probe is likely to observe numerous shocks in the next few years. An outstanding question that has received surprisingly little attention has been how turbulence interacts with collisionless shock waves. Turbulence in the supersonic solar wind is described frequently as a superposition of a majority 2D and a minority slab component. We formulate a collisional perpendicular shock-turbulence transmission problem in a way that enables investigation of the interaction and transmission of quasi-perpendicular fluctuations such as magnetic flux ropes/islands and vortices as well as entropy and acoustic modes in the large plasma beta regime. We focus on the transmission of an upstream spectrum of these modes, finding that the downstream spectral amplitude is typically increased significantly (a factor of 10 or more), and that the upstream spectral index of the inertial range, and indeed the general spectral shape, is unchanged for the downstream magnetic variance, kinetic energy, and density variance. A comparison of the theoretically predicted downstream magnetic variance, kinetic energy, and destiny variance spectra with those observed at 1 au, 5 au, and 84 au by Wind, Ulysses, and Voyager 2 shows excellent agreement. The overall theoretically predicted characteristics of the transmission of turbulence across shocks observed in the solar wind appear to be largely consistent with recent observational studies by Pitna et al. 2016, Pitna et al. 2020, and Borovsky 2020. We conclude with some recent simulations of the interaction of current sheets and turbulence with perpendicular shocks and related particle acceleration.

We report observations of <100 keV/nucleon suprathermal (ST) H, He, O, and Fe ions in association with three separate crossings of the heliospheric current sheet that occurred near perhelia during PSP encounters 7, 8, and 9. In particular, we compare and contrast the ST ion time-intensity profiles, velocity dispersion, pitch-angle distributions, spectral forms, and maximum energies during the three HCS crossings. We find that these unique ST observations are remarkably different in each case, with those during E07 posing the most serious challenges for existing models of ST ion production in the inner heliosphere. In contrast, the ISOIS observations during E08 appear to be consistent with a scenario in which ST ions escape out of the reconnection exhausts into the separatrix layers after getting accelerated up to ~50-100 keV/nucleon by HCS-associated magnetic reconnection-driven processes. Finally, ST ions during the E09 HCS crossing have properties that are somewhat similar to those seen during both E07 and E08 crossings, with ion intensities being higher outside the exhausts and the separatrices, but significant intensity increases are also observed inside the reconnection exhausts. We discuss these new observations in terms of local versus remote acceleration sources as well as in terms of expectations of existing ST ion production and propagation, including reconnection-driven and diffusive acceleration in the inner heliosphere.

Thermospheric OI 630.0nm (redline) dayglow emissions serve as a useful tracer to infer the dynamics of the upper atmospheric regions. The dynamics can originate due to Gravity waves (GWs), tides, winds, and solar flux, all of which are known to be time varying. We are carrying out OI 630.0nm dayglow emission measurements from ground-based large field-of-view spectrographs for over a decade from the low- and off-equatorial latitudes which resulted in several new insights, a few salient ones being: the efficiency of upward coupling of atmospheres especially during low- solar activity period being higher than that in the high solar activity period, setting up of meridional circulations during stratospheric sudden warming events, existence of longitudinal differences in equatorial electrodynamics in short spatial distances, the daytime electric field effect being nearly constant until the crest regions of the equatorial ionization anomaly, and the meridional winds to be having an effect on the magnitudes and variability of the OI 630.0nm dayglow emissions. The effect of meridional winds on the latitudinal variation of OI 630.0nm dayglow gave crucial insights into the role of different production mechanisms on the OI 630.0nm dayglow. It is known that out of all the mechanisms producing the OI 630.0 nm dayglow emissions, the dissociative recombination mechanism originates at the highest altitude. Thus, the ionospheric height plays an important role on the resultant column integrated redline dayglow emissions. Detailed analysis carried out on the diurnal dayglow emission variability over a tropical latitude on a given day is seen to be correlated with the electron densities at higher altitudes, whereas, on the days with lower electrojet strengths the diurnal behavior of dayglow matched closely with the electron densities at lower altitudes. The intriguing dependence on the electrojet strength variation versus the diurnal dayglow emissions will be discussed in this paper. 

A narrow latitudinal band of the enhanced eastward ionospheric current about the dip equator, where the geomagnetic field is horizontal, is called the equatorial electrojet (EEJ). In this study, we use the ground-based two-station technique to remove the contribution of the global Sq and to estimate the EEJ magnetic field contribution from available pairs of magnetometers in South America. Each pair of magnetometers consists of one located near the dip equator and another ~6° to 9° away from the dip equator but within the same longitude sector. We investigate the variability of the EEJ at very narrow longitudinal separation and associated phenomena over the American low-latitude regions using data from at least five pairs of magnetometers. The behavior of ground-based Global Positioning System (GPS)-total electron content (TEC) in response to the EEJ is also examined. The strength of the EEJ is seen stronger in the western longitude sector of the American low latitudes than that in the eastern sector. In brief, the possible mechanism, as well as origins, drivers, and effects of the longitudinal variability of the EEJ in the low-latitude ionospheric electrodynamics, will also be discussed.

The Global-scale Observation of Limb and Disk mission observed distinct hemispherically asymmetric evolution of the equatorial ionization anomaly post-sunset between 40°- 50°W on Nov 19, 2018, with the southern crest shifting poleward but the northern crest remaining at the same latitude. The Whole Atmosphere Community Climate Model-eXtended captured this phenomenon. Diagnostic analysis revealed that this asymmetric evolution was due to the hemispheric asymmetry in plasma transport by E x B drifts and neutral winds. The pre-reversal enhancement occurred earlier in the northern hemisphere (NH) but was latitudinally more expansive in the southern hemisphere (SH). In the NH, northward neutral wind transport dominated around sunset, causing the crest to be lower and decay faster. Thereafter neutral wind and E x B transport largely balanced each other, and the crest remained in the same latitude region. In the SH, E×B transport augmented wind transport, lifting the crest and pushing it poleward.

Equatorial Plasma Bubbles (EPBs) are an interesting and important nighttime ionospheric plasma irregularity phenomenon that occur over the equatorial- and low-latitudes. The seeding, development, and persistence of EPBs depend on factors such as alignment of dusk terminator with the magnetic field lines, thermospheric winds and waves, electric fields, etc. At a given longitude sector, these factors change with season, producing longitudinal differences in the EPBs occurrence rate. These variabilities can change with the solar activity. The NASA Global‐scale Observations of the Limb and Disk (GOLD) mission takes far‐ultraviolet images of the Earth from geostationary orbit. Individual EPBs, measured as depleted N-S elongated regions in the OI 135.6 nm emission, can be detected multiple times after the sunset over the South America, Atlantic, and West African longitude sectors. In these three longitude sectors we compared EPBs occurrence rates from 2019 to 2021. Preliminary observations suggest that EPB occurrence increased linearly with the solar activity increase. Over the South American and Atlantic longitude sectors, EPBs occurrence rate was around 95% in December solstices. The occurrence rate over the West African longitude sector in the same month was 10%. The seasonal and longitudinal variations of EPBs occurrence rates and their solar activity dependence will be discussed in this work.

We performed a superposed epoch analysis of solar wind, IMF, geomagnetic index, and the rate of total electron content (TEC) index (ROTI) derived from global GNSS-TEC data during geomagnetic storms from 2000 to 2018 (617 events) in order to clarify the dependence of ionospheric responses on solar wind dynamic pressure. In this analysis, we defined the time of the SYM-H minimum as a zero epoch time. The 617 events were classified according to the integrated value of a dawn-dusk (Ey) component of interplanetary electric field (IEF) for 12 hours before the zero epoch time. We selected 233 events with an integrated value of IEF Ey in a range of 1000-2000 mV/m∙min to minimize the IEF Ey dependence. The 233 events were also classified according to whether the integrated value of solar wind dynamic pressure for 12 hours before the zero epoch time exceeded 2200 nPa∙min (high pressure: 117 events) or not (low pressure: 116 events). During the storm main phase, high-latitude ROTI enhancements extended to more equatorward (2-3°) in the dusk and midnight sectors for the high pressure than for the low pressure. This result indicates that the ionospheric two-cell convection region extended to lower latitudes for the high pressure than for the low pressure. This suggests that the magnetospheric convection and associated ionospheric convection electric fields are stronger as the dynamic pressure becomes large. On the other hand, low-latitude ROTI enhancements extended to more poleward (~4°) in the dusk-midnight sectors for the high pressure than for the low pressure. This result suggests that a penetration electric field from the high-latitudes to equator is large under the high dynamic pressure. Therefore, not only IEF Ey but also solar wind dynamic pressure plays an important role in the spatiotemporal variations of ionospheric response during geomagnetic storms.

The equatorial electrojet (EEJ) is an important manifestation of ionospheric electrodynamics. Day-to-day changes of the EEJ result from E-region dynamo processes are primarily driven by the day-to-day changes of atmospheric waves propagating up from the lower and middle atmosphere. In particular, the past findings point out that the day-to-day variation of the semi-diurnal westward propagating tide with zonal wave number 2 (SW2) plays an important role in the day-to-day variation of the EEJ. People traditionally use a monthly average window to estimate tides from observations so the signals of the day-to-day changes are smoothed in the estimations. In this study, we show hourly variations of the EEJ can be estimated globally from ground-based magnetometers data by using a new data-driven approach. This new approach is based on an ensemble transform adjustment method and is applied to the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) lower boundary conditions (LBCs) at about 97 km altitude in order to make the model’s tidal characteristics to be more consistent with observed magnetic perturbations associated with the EEJ. The data-driven approach yields a better agreement of modeled magnetic perturbations with the ground-level and LEO-level magnetometer data. even over the Pacific ocean where the data coverage is sparse. The analysis results confirm the past findings that the day-to-day variation of SW2 wind fields play an important role in generating the day-to-day variation of the EEJ. The use of routinely available ground-based magnetometer data to constrain the TIE-GCM LBCs could provide an opportunity to investigate how day-to-day tidal variability drives equatorial electrodynamics variability on global scales.

Increased availability of multipoint measurements of SEP events has revealed their sometimes wide longitudinal extents in the inner heliosphere. But the question of how much the process of diffusive transport perpendicular to the interplanetary magnetic field contributes to their spatial spread continues to be open. Related, and essential to the answer, is the extent to which the underlying coronal and heliospheric field geometries play a role. A standard practice in analyzing SEP events is to trace interplanetary field lines from the spacecraft back to the solar surface to determine how close the observer’s magnetic connection is to a flare or eruption site. However many back-mappings use simple Parker Spiral Field assumptions that neglect both the coronal field geometry and structures in the heliospheric fields. A realistic description of the geometry of an observer’s magnetic connectivity during a SEP event requires fields derived from coupled corona and heliosphere simulations, which are not generally available. Nevertheless, some insights can be gained by breaking down the geometry problem into its contributions. The initial spread in observer magnetic connections - when the SEP sources are still close to the Sun – can be inferred from coronal field geometry described by PFSS models. To better understand how the coronal field structure contributes to early SEP event spreads under the full range of solar activity conditions, we consider the geometry of the open fields reaching low heliolatitudes over the previous 4+ solar cycles. Their angular departures from radial, suggest how widely the coronal open fields, into which SEPs are initially injected, may diverge. Estimations of the later-event spreading in the heliosphere requires examining heliospheric models, such as those available from archived WSA-ENLIL cone model simulations. We consider a selection of CCMC results, toward illustrating the influences of coronal and heliospheric field geometry in SEP event spread interpretations.

During a solar flare, a large number of particles is accelerated. Information on the pitch angle distribution of such accelerated particles is important for understanding the acceleration and propagation processes. Yokoyama et al. (2002) estimated the pitch angle of accelerated electrons from the propagation velocity of a nonthermal microwave source, using Nobeyama Radioheliograph (NoRH) data. After that, however, almost no such direct observational results have not been reported. In this situation, we found another event (an M-class flare on 22 October 2014) which clearly showed fast propagation of a nonthermal microwave source. Based on the loop structure observed with SDO/AIA, it is recognized that the observed propagation corresponds to the motion from the looptop region to one of the footpoint regions. Using the coronal magnetic field model obtained from the NLFFF calculations, the parallel velocity to the magnetic field of accelerated electrons is about 98,000 km/s. The velocity of electrons emitting 17 GHz microwaves is close to the speed of light. Following the Yokoyama et al. (2002), the pitch angle of the accelerated electrons was estimated at about 65 degrees. From the magnetic field strength of the NLFFF model, the size of the loss cone is estimated at about 36 degrees. Considering these facts, most of the accelerated electrons could be reflected at the footpoint region. In fact, we found the second propagation of faint microwave feature following the first one. Assuming that the second propagation is produced by the bouncing motion of the accelerated electrons in the flare loop, the velocity along the loop is about 105,000 km/s. This is consistent with the velocity obtained from the first propagation from the looptop. This is the first observational evidence of a bouncing motion of accelerated electrons actually trapped in a flare loop. 

Magnetic reconnection is a primary electron acceleration process in space and solar plasmas. Understanding how electrons are accelerated and the resulting particle energy spectra are among the central topics in reconnection studies. This talk summarizes some recent advances made by kinetic particle-in-cell simulations in revealing the primary acceleration mechanisms, particle transport due to 3D reconnection physics, and their roles in forming power-law particle energy spectra. Despite these advances at kinetic scales, we highlight the challenges and efforts in studying electron acceleration and transport in a large-scale turbulent reconnection layer (e.g., solar flares). We show that energetic particle transport equations, combined with high-resolution MHD simulations, can reproduce several observational features of the energetic electrons accelerated in the large-scale solar flare reconnection layers. These results have important implications for understanding electron acceleration and transport in magnetic reconnection.

Shocks are efficient particle accelerators. Depending on the shock geometry, particles are often believed to be accelerated via the Diffusive Shock Acceleration (DSA) mechanism at parallel shocks and via the Shock Drift Acceleration (SDA) mechanism at perpendicular shocks. However, ripples can develop at the shock surface due to various in-homogeneity in the plasma, and have been seen in both observations and simulations. We examine the effect of shock ripples on particle acceleration process at a quasi-perpendicular shock using numerical simulations based on the backward stochastic differential equation method. We show that both the particle spectrum and particle pitch angle distribution are affected by the shock ripples. Our numerical results may help to better understanding energetic particle observations at various heliospheric and astrophysical sites.

We investigated the relationship between the spectral structures of type II solar radio bursts in the hectometric and kilometric wavelength ranges and solar energetic particles (SEPs). To examine the statistical relationship between type II bursts and SEPs, we selected 26 coronal mass ejection (CME) events with similar characteristics (e.g., initial speed, angular width, and location) observed by the Large Angle and Spectrometric Coronagraph, regardless of the characteristics of the corresponding type II bursts and the SEP flux. Then, we compared associated type II bursts observed by the Radio and Plasma Wave Experiment on board the Wind spacecraft and the SEP flux observed by the Geostationary Operational Environmental Satellite orbiting around the Earth. We found that the bandwidth of the hectometric type II bursts and the peak flux of the SEPs has a positive correlation (with a correlation coefficient of 0.64). This result supports the idea that the nonthermal electrons of type II bursts and the nonthermal ions of SEPs are generated by the same shock and suggests that more SEPs may be generated for a wider or stronger CME shock with a longer shock duration. Our result also suggests that considering the spectral structures of type II bursts can improve the forecasting accuracy for the peak flux of gradual SEPs.

Global-scale, synoptic imaging of daytime, thermospheric composition and temperatures and of nighttime equatorial ionization anomaly densities is dramatically enhancing the understanding of thermosphere-ionosphere (T-I) responses to forcing from below and above. NASA’s GOLD mission, imaging the Earth from geostationary orbit at 47.5° W longitude, provides simultaneous, synoptic imaging of the composition and temperature near 160 km for locations on the dayside from 06:10 to 23:10 UT (03:00-20:00 LT at the satellite) daily, as well as the nighttime equatorial ionization anomaly (EIA) over the Atlantic and South America every evening. Recent examples of puzzling (i.e., yet to be fully understood) observations that will be discussed include the January 15, 2022 volcanic eruption in Tonga, the solar eclipse over Antarctica in December 2021 and the February 3, 2022 geomagnetic storm responsible for the loss of 40 Starlink satellites. All these events produced dramatic changes in the T-I system that are observed by both other satellite missions (e.g., ICON and COSMIC-2) and ground-based instruments. The quantitative changes observed in many of these cases are significantly greater than is predicted in model calculations. Recent additions to our observing capabilities provide an unprecedented opportunity to overcoming these differences and advance both our understanding of the T-I system and capabilities to forecast space weather conditions.

FORMOSAT-7/COSMIC-2 is a joint satellite program between Taiwan and the United States that is providing expanded neutral atmosphere and space weather data for operational and research communities. This six-satellite constellation was launched into a 23-degree inclination equatorial orbit on June 25, 2019. Completion of orbital phasing of the constellation finished in February of2021. With six orbital planes, the satellites simultaneously observe longitudinal variations with~30 degree spacing. The mission payload is the Tri-GNSS Radio Occultation System (TGRS), designed by the Jet Propulsion Laboratory (JPL). Science payloads include the Ion Velocity Meter(IVM) designed by the University of Texas at Dallas (UTD), and the Radio Frequency Beacon (RFB)designed by SRI. The payloads provide a range of observation types relevant space weather applications including GNSS limb and overhead TEC, electron density profiles, amplitude/phase scintillation (TGRS), in-situ ion density, composition, and velocities (IVM), and TEC between the satellite and ground-stations (RFB). Data collected from the constellation of satellites can resolve large, medium, and small-scale ionospheric structures. This presentation summarizes the space weather data products available for operations and research applications.

It is increasingly evident that a few global-scale waves from the tropical wave spectrum with periods between about 0.5 days to 3.5 days, commonly referred to as ultra-fast tropical waves (UFTW), preferentially propagate upward from their sources and significantly impact the dynamics and mean state of the ionosphere-thermosphere (IT, 100-600 km). Two of the most prominent and well-established UFTW are the eastward-propagating 2-3-day period ultra-fast Kelvin wave with zonal wavenumber s = -1 (UFKW1) and the diurnal eastward propagating tide with zonal wavenumber s = -3 (DE3) that are excited by deep convective processes in the tropical troposphere. In this work, ion densities from Ion Velocity Meter (IVM) instruments onboard the Ionospheric Connection Explorer (ICON) and Scintillation Observations and Response of the Ionosphere to Electrodynamics (SORTIE) satellites and horizontal winds from ICON’s Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument are combined to provide a comprehensive study of UFTW-induced IT variability during May 2020 - September 2020. Focus is placed on UFKW1 and DE3 and their day-to-day and latitudinal variability. Lower and middle atmospheric fields from the Specified Dynamics (SD) Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) with Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) nudging are then used to infer their vertical propagation characteristics and evolution with time.

The Ion Velocity Meter (IVM) on NASA's Ionospheric Connection Explorer (ICON) reports the in-situ ion density, ion temperature and 3-component ion drift velocity, retrieved from the measurement by a retarding potential analyzer and an ion drift meter. The uncertainty of the drift velocity is known to be influenced by the ion density and O⁺ fraction, according to the pre-flight performance test. ICON was launched into a deep solar minimum in late 2019, followed by a solar quiet (F10.7 < 80) period until September 2020. In order to quantify the uncertainty of the IVM’s drift velocity in the low plasma density environment, the cross-comparisons among Swarm’s equatorial electric field (EEF), the vertical drift from ground-based JULIA coherent radar, and IVM’s meridional drift (vertical component at the equator) is presented in this study. Three main results are discussed in this presentation: 1) Swarm’s EEF is in good agreement (R > 0.8) with the zonal electric field derived from the JULIA’s vertical drift regardless of F10.7 value. 2) The zonal electric field derived from the IVM’s meridional drift is in good agreement with Swarm’s EEF in 2021, but we were unable to find a significant correlation between Swarm EEF and IVM's meridional drift in the deep solar minimum in 2020. 3) An ad hoc IVM correction based on the 24-hour running mean of meridional drift can bring the IVM data into better agreement with Swarm and JULIA. An additional quality control based on O⁺ density and O⁺ fraction may be needed to interpret IVM’s meridional drift. 

Solar flares are the most powerful energy release phenomena and important sites for particle acceleration in the solar system. Although many particle acceleration mechanisms have been proposed, it remains controversial which process plays a dominant role and can explain various observational signatures of particle energization. In solar flares, HXR and radio observations provide primary diagnostics of the acceleration and transport of energetic electrons. Nonthermal looptop sources have suggested that particle acceleration takes place above the top of flare loops and the flare termination shock is one of the promising candidates as the acceleration mechanism. Here we investigate the acceleration of energetic electrons in solar flares by combining a large-scale MHD simulation of a solar flare with a particle acceleration and transport model. We find that the accelerated electrons are concentrated in the looptop region due to the acceleration at the termination shock and confinement by the magnetic trap structure, in agreement with HXR and microwave observations. Numerous plasmoids can be produced in the reconnection current sheet and interact dynamically with the shock. We find that the energetic electron population varies rapidly in both time and space due to plasmoid-shock interactions. We also present the first numerical modelling of nonthermal double coronal X-ray sources based on electron acceleration by a pair of termination shocks. Our simulations have strong implications to the interpretation of coronal nonthermal emission sources.

Double-power-law energy spectra have been observed in many large solar energetic particle (SEP) events. It is an important feature for understanding the acceleration and propagation of high-energy particles, but its formation mechanism remains unclear. We 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 spectrum integrated over the simulated domain can be described by a double power law, and the break energy depends on the charge-to-mass ratio of the ions as Eb~(Q/A)^α. 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 due to particle diffusion. Our simulations suggest that the particle spectral forms can vary significantly along the shock front and depend on the region to which the observer is connected. We also examine the double-power-law formation mechanism by analyzing the variation of particle energy spectra during propagation in the interplanetary space.

The energy spectrum of solar energetic electron (SEE) events carries crucial information on the origin/acceleration of energetic electrons at the Sun. Using the electron measurements from the Wind 3D Plasma and Energetic Particle instrument at ~1 to 300 keV during 1998-2015, we find 35 SEE events with a bump break in the electron flux energy spectrum, different from the typical SEE events with a double-power-law energy spectrum. Among these 35 SEE events, we select 11 good events with a spectral bump observed at no less than three energy channels, to investigate the spectral characteristics. For all the 11 events, the background-subtracted electron peak flux versus energy spectrum fits well to a single-power-law distribution plus/times a Gaussian function with a bump at ~15-70 keV and a power-law index of 2.6±0.5. For these SEE events, the associated ³He/⁴He ratio is positively correlated with the central energy of bump, while ~67% are ³He-rich events. Compared to typical SEE events, the 11 events show a stronger association with GOES SXR flares (~73%), RHESSI HXR flares (~89%), west-limb CMES (~90%) and type II radio bursts (≥55%). In addition, for the 3 events with good measurements the HXR peak flux energy spectrum, the estimated power-law index of HXR-producing electrons via thick-target bremsstrahlung model is strongly larger than that of SEEs. Finally, we will investigate the acceleration/formation of these SEE events with a bump spectral break.

We present a theoretical explanation of the observed energy spectrum of acceleration suprathermal electrons at interplanetary shocks and bow shock, by analytically solving the parker transport equation with the shock drift acceleration term for a 1-dimensional shock with a finite shock thickness (D_ramp). We define a dimensionless parameter K^*=k/v_upD_ramp to describe wether the diffusion or the convection is stronger, where k is the diffusion coefficient and v_up is the shock’s normal velocity in upstream. We find that for a shock with K^*<<1 (weak diffusion limit), the electron acceleration would be weak and thus the energy spectrum of shocked suprathermal electrons would remain the same shape as the seed electrons in the ambient upstream. This is consistent with the observations of Interplanetary shocks at 1AU (Yang et al., 2018). For a shock with K^*>>1 (strong diffusion limit), the acceleration would be strong to produce a power-law energy spectrum of shocked electrons with a spectral index β_∞~3r/2(r sin²θ₁-sin²θ₂), where r is the shock’s compression ration, θ₁ and θ₂ are the angles between shock normal and magnetic field in upstream and downstream. This is consistent with the electron observations of the Earth’s bow shock (Liu et al., 2020) at 1-20 keV, however, the observed spectral index is 1.5-2 times of β_∞, suggesting that the drift acceleration term should be corrected to reproduce the shocked suprathermal electron observations of the Earth’s bow shock.

The acceleration of high-energy charged particles is ubiquitous in space and astrophysical plasmas. The collisionless shocks have been recognized as among the most efficient particle accelerators in nature. Diffusive shock acceleration (DSA), the standard model for particle acceleration at shocks, has achieved considerable success over the decades. However, it has been known that electron acceleration via DSA at shocks is rarely seen at interplanetary shocks or planetary bow shocks, which is in clear contrast to more commonly seen ion acceleration. One of the reasons for the poor electron acceleration efficiency is the lack of an injection mechanism that accelerates a fraction of thermal electrons to the threshold energy beyond which DSA becomes effective.
We have proposed stochastic shock drift acceleration (SSDA) as a mechanism for electron injection that can take place within the transition layer of quasi-perpendicular shocks [Katou & Amano, 2019]. It is essentially shock drift acceleration (SDA) that takes into account the effect of stochastic pitch-angle scattering within the shock transition layer. We will present its theory [Katou & Amano 2019, Amano & Hoshino 2022], signatures obtained with multidimensional kinetic simulations [Matsumoto et al. 2017, Kobzar et al. 2021], and in-situ observational evidence at Earth’s bow shock [Amano et al. 2020]. We demonstrate that the novel injection theory can consistently describe the electron acceleration from a few times thermal energy to ultra-relativistic energy. We find that the most important parameter regulating the electron acceleration efficiency is the Alfven Mach numbers defined in the Hoffmann-Teller frame.

The energy spectra of energetic particles carry important information on the origin and acceleration of these particles. Here we present a statistical survey of the quirt-time 50-600 keV electron energy spectra in the terrestrial radiation belt measured by the Image Electron Spectrometer (IES) on board a Chinese Navigation Beidou satellite in an inclined (55°) geosynchronous orbit, during quiet times from 2015 October to 2020 February. We selected 6704 quiet-time samples and fit the quiet-time omnidirectional electron flux energy spectra to a pan-spectrum fitting function, after considering the uncertainties both in electron flux J and energy E. After a series of statistical study concerning the spectral parameters, we move on to the electron flux’s relationship with the solar wind parameters and/or the geomagnetic indices (AE, SYM-H), aiming to suggest a possible source of these quiet-time energetic electrons in the radiation belt. We found that the electron flux (the spectral index) is strongly (weakly) correlated with the solar wind speed. According to the cross-correlation analysis, a possible time lag of ~ 0-2 days is linearly correlated with log(E), and the maximum cross-correlation coefficient (MCC) first increases with energy from 50 keV to ~200 keV and then decreases with energy.  Generally, the MCC is larger at lower MLATs and at the nightside. Further studies will examine the relationship between the electron fluxes and the geomagnetic indices (AE, SYM-H).

Radio occultations are applied to improve the performance of weather observations. The receiving signal contains integrated information along the GNSS-LEO link that penetrates both the lower and upper atmosphere. However, owing to the fluctuations in the angle of arrival, phase, and intensity of the receiving signals are proportional to the overall length that the density irregularities occupy. It makes the ionosphere effects non-negligible when applying the RO technique to the weather observations. In this presentation, the irregular RO profiles that possibly result in the occurrence of plasma irregularities are identified. These RO profiles are found to frequently occur adjacent or collocated to the confirmed equatorial plasma bubbles identified by the IVM in-situ measurements of FORMOSAT-7/COSMIC-2 and ICON mission, and the 135.6nm nightglow emission of the GOLD mission. Furthermore, the irregular profiles are especially sensitive to the plasma bubbles embedded in low background plasma density during the post-midnight sector or June months.

So far, variations in atmospheric electric field associated with volcanic lightning discharges, plumes and eruption cloud due to volcanic eruptions have been reported (Firstov et al., 2017). There was one report that VLF amplitude largely varied during Mt. Kirishima eruptions during 18-27 January, 2011, which suggested that atmospheric gravity waves generated by the eruptions (Rozhnoi et al. 2014). However, effects of neutral atmospheric waves excited by volcanic eruptions are not revealed. In this study, we investigate response of the atmospheric electric field/D-region ionosphere to Tonga volcanic eruptions. The Hunga Tonga-Hunga Ha‘apai volcano explosively erupted during 04:10-04:30 UT on 15 January, 2022. The atmospheric electric field has been observed in Chiba University (CHB), Japan, and Studenec (STU), Czech. The distances of CHB and STU from the Tonga volcano were 7789.5 km and 16634.7 km, respectively. The VLF/LF transmitters used in this study were NWC (19.8 kHz), JJY(40 kHz and 60 kHz), JJI(22.2 kHz), BPC(68.5 kHz), KRA(24.1 kHz), and INS(18.2 kHz). The receivers were Tainan in Taiwan, and Kagoshima in Japan. The first variations in pressure data were seen around 10:57 UT and 19:03 UT on 15 January in CHB and STU, respectively. The propagation velocity was 310-320 m/s, which is typically horizontal velocity of atmospheric Lamb waves. There were variations in atmospheric electric field with a period of 10-100 minutes at CHB at the first and second arrival times of the Lamb waves. The VLF/LF amplitudes for almost propagation paths showed the similar period of 10-100 minutes around the first arrival time of the Lamb waves. This could be signatures of changes in global electric circuit via Lamb waves excited by Tonga volcanic eruptions. In this presentation, we will report and discuss the phenomena in detail.

The low solar atmosphere is highly gravity stratified and the total hydrogen density decreases by 7 orders of magnitude within a thin layer of several Mm. The temperature in this region is generally only several thousand K and the plasmas are partially ionized. Thanks to the high resolution telescopes, plenty of small scale reconnection events at different altitudes in this region have been observed. The interactions between ions and neutrals may strongly affect the reconnection process and make the reconnection mechanisms to be very different from those in fully ionized plasmas. What’s more, the radiative transfer and cooling process make the studies of magnetic reconnection in this region to be more difficult. In this talk, we will present our recent progresses on numerical studies of magnetic reconnection in the low solar atmosphere with different plasma beta, and discuss the mechanisms which lead to plasma heating in different reconnection events.

Working in pressureless magnetohydrodynamics, we examine the consequences of some peculiar dispersive properties of linear fast sausage modes (FSMs) in one-dimensional cylindrical equilibria with a continuous radial density profile. As recognized recently on solid mathematical grounds, cutoff axial wavenumbers may be absent for FSMs when the density profile varies sufficiently slowly outside the nominal cylinder. Trapped modes may therefore exist for arbitrary axial wavenumbers and density contrasts, their axial phase speeds in the long-wavelength regime differing little from the external Alfven speed. If these trapped modes indeed show up in the solutions to the associated initial value problem (IVP), then FSMs have a much better chance to be observed than expected with classical theory, and can be invoked to account for a considerably broader range of periodicities than practiced. However, with axial fundamentals in active region loops as an example, we show that this long-wavelength expectation is not seen in our finite-difference solutions to the IVP, the reason for which is then explored by superposing the necessary eigenmodes to re-solve the IVP. At least for the parameters we examine, the eigenfunctions of trapped modes are characterized by a spatial extent well exceeding the observationally reasonable range of the spatial extent of initial perturbations, meaning a negligible fraction of energy that a trapped mode can receive. We conclude that the absence of cutoff wavenumbers for FSMs in the examined equilibrium does not guarantee a distinct temporal behavior.

Sunspot rotation has been found a century ago and has long been considered as an important process in association with solar eruption, because it is an efficient mechanism for transporting energy and helicity from below the photosphere into the corona. Nevertheless, there is still no 3D MHD simulation of solar eruption produced directly through sunspot rotation, in particular, in the realistic, complex coronal magnetic configurations. In this talk, we will present such a simulation. We take the evolution of AR12158 as an example, in which there is a clearly-observed, continuous rotation of a major sunspot leading to an eruptive X1.6 flare on 2014 September 10.  We start with a potential field extrapolated from the HMI magnetogram of the AR, and then apply surface rotation flow to the major sunspot. For a long time, the magnetic energy and helicity increased monotonically while the kinetic energy keeps a small value, as the MHD system evolves quasi-statically. At a critical time, there is a clear transition from the quasi-static state to an eruptive phase in which the kinetic energy impulsively rises by orders and the magnetic energy drops quickly. During the rotation phase, it is found that there is an vertical current sheet created in the sheared arcade, and once tether-cutting reconnection sets in the current sheet, the eruption is inevitably triggered even we turn off the boundary driving, and a highly twisted flux rope originates from the eruption, forming a CME.

It is widely accepted that coronal magnetic flux ropes are the core-structures of large-scale solar eruptive activities, which inflict dramatic impacts on the solar-terrestrial system. Previous studies have demonstrated that varying magnetic properties of a coronal flux rope system could result in catastrophes of the flux rope, so that trigger solar eruptive activities. Since the total mass of a flux rope also plays an important role in stabilizing the rope, we use 2.5-dimensional magnetohydrodynamic (MHD) numerical simulations in this letter to seek for flux rope catastrophes associated with the mass, so as to investigate how a flux rope evolves as its total mass varies. It is found that mass unloading processes that decreases the total mass of the rope could result in an upward catastrophe of the flux rope, during which the rope jumps upward and the magnetic energy is released. This indicates that mass loading processes could initiate the eruption of the flux rope. Moreover, there is also a downward catastrophe that could be caused by mass loading processes, via which the total mass accumulates. The magnetic energy, however, is stored during the downward catastrophe, indicating that mass loading processes could cause confined activities that might be responsible for the energy storage before the onset of coronal eruptions.

Microflares are small solar activities in the low atmosphere. Recent instruments have brought unprecedented high-resolution images, derived from which some surveys have suggested that microflares may be triggered by magnetic reconnection. Here, based on 3D radiative magnetohydrodynamic simulation of the solar quiet region, which is conducted with MURaM code including the upper convection zone, photosphere, chromosphere, and low corona, we investigate the 3D magnetic structures and heating mechanism of a microflare. It is found that the microflare originates from local hot plasma in the chromosphere. The hot plasma is almost co-spatial with the maximal heating rate normalized by the density. The 3D velocity field reveals a pair of low-speed converging flows toward and high-speed outflows moving away from the hot plasma. These features support that magnetic reconnection plays a critical role in heating the local chromospheric plasma, giving rise to the observed microflare. The magnetic topology analysis further discloses that the reconnection is located near quasi-separators where both the current density and squashing factors are maximal although the specific topology varies from location to location.

Surface rupture is a well-known key aspect in controlling the severity of earthquake hazard, as vividly illustrated by numerous examples including the recent Ms 6.9 Menyuan earthquake in Qinghai, China, that severely damaged the Lanxin high-speed railway. Although large earthquakes were often accompanied with surface ruptures, it is not clear whether magnitude solely determined whether ruptures may break the ground. Furthermore, the mechanisms controlling whether or not earthquake ruptures may extend to the surface remain elusive. Here we first collect data for earthquakes with moment magnitudes (Mw) over 6 in the past two decades in China and other regions. The results show that most earthquakes surrounding the Tibetan plateau may produce surface rupture if their magnitudes are greater than 6.7. However, magnitude is not the sole factor that controlled surface-breaching ruptures, as evidenced by outliers such as the 2014 Mw 6.2 Ludian, Yunnan, and the 2014 Mw 6.0 Napa Valley, California, earthquakes. Since the shallow portion of faults is usually rate-strengthening and thus unfavorable for rupture propagation, earthquakes need to compensate the shallow energy deficit before reaching the surface. Based on heterogeneous distribution of initial stress on faults, we conduct numerical simulations of rupture propagation by prescribing the nucleation zone (hypocenter). We find that different hypocenter positions can result in a small change in moment magnitude (0.2) but a significant transition from buried to severely surface-breaking ruptures. As such, we propose that those distinct rupture behaviors may result from heterogeneities of fault zones. The indeterministic rupture behaviors on heterogeneous faults serves as a viable mechanism to explain the various observed surface rupture behaviors.

Continuous waveforms from 2008 to 2018 recorded by 13 seismic stations deployed by Qinghai Seismic Network around the boundary of the Songpan-Ganzi and Qiangtang Block in Yushu, Qinghai are applied to a high-resolution similar-waveform workflow for small earthquake detection, selection and location. We explore the GPU-based Match & Locate method which accelerates calculation speed, making it possible to detect earthquakes of long-term data. We then select true positive detections by removing noises from earthquake signals using a deep-neural-network-based techniques called DeepDenoiser. The PhaseNet algorithm and hypoDD program are conducted to pick seismic phases and relocate detected events. The double-difference relocations delineate a nearly vertical dipping fault plane of the Ganzi-Yushu fault. The average cumulative slip rate estimated from 19 repeating earthquakes clusters is 6.5 mm/yr. The space-time evolution of foreshock sequences of the 2010 ML 7.1Yushu earthquake shows the ruptured fault geometry and our static coulomb stress changes model suggests that hypocenters locating in a high-stress region indicates the mechanism of the nucleation of the mainshock. Our observations are consistent with a triggered cascade of stress transfer, where previous foreshocks load adjacent fault patches to rupture as additional foreshocks, and eventually the mainshock. The study also demonstrates a complete small earthquake detection, selection and location for long-term data using well‐trained deep‐learning methods.

Thrust-fold belts are commonly developed in and around the Tibetan Plateau. Investigations of their structural development and landscape response through space and time have important implications for hydrocarbon exploration and geological hazard assessment. A fold may grow both vertically (increasing in amplitude) and laterally (lengthening along strike), with complex deformation histories. Besides geophysical methods for subsurface characterization, geomorphic indicators (the spatial pattern and density of river channels, topographic profile along fold crest, and wind gaps) have also been proposed to identify lateral fold propagation. Nevertheless, whether these present-day topographic expressions are able to demonstrate fold growth processes requires validation. Here, we carry out a series of numerical models to reproduce fold growth in three dimensions. The results verify that the stream deflections at the end of the folds and the decrease in topographic gradient along the crest are reliable geomorphic features to indicate lateral fold propagation. In particular, segmented crest profile supports pulsed lateral propagation. We compared these results to two natural examples at the leading edge of the southern Tian Shan. It is suggested that the Yaken anticline has experienced the acceleration of tectonic uplift, and at least two periods of lateral fold propagations occurred along the Kashi anticline. The consistency with geological evidences verifies that the spatial pattern of river channels and the topographic profile along fold crest can be applied to unravel the deformation histories of thrust-fold belts.

The study of dynamic processes of orogenic belts is a key factor in our understanding of the formation mechanisms, kinematics and dynamics of different orogenic belts, as well as in the prediction of future trends. Previous analog and numerical models have been used to address the cause of continental deformation, either in terms of lateral forces transmitted through the lithosphere, or forces at the base of the crust from the underlying subducting mantle lithosphere. To study the process of the Qilian orogenic belt on the northern margin of the Qinghai-Tibetan Plateau, we establish a series of finite element models to discover how continental underthrust generates a bivergent lithospheric-scale thrust wedge. The models reproduce the Cenozoic reactivation of the Qilian Shan, the initiation and evolution of the topographic uplift and fold-thrust belts. It is found that the inflection point of the southward underthrusting of the Asian lithospheric mantle (ALM) has an important influence on the architecture of the Qilian Shan fold-thrust belts. Simulation studies of dynamic processes explain dynamical and kinematic processes constrained by the geophysical observations. Based on the results, we qualitatively discuss the relevance of the formation mechanisms of the main frontal thrust of Himalayan, the Tian Shan orogenic belt and the Greater Caucasus orogenic belt comparing with the Qilian orogenic belt. Reference：Zuza, A. V., Wu, C., Wang, Z., Levy, D. A., Li, B., Xiong, X., & Chen, X. (2019). Underthrusting and duplexing beneath the northern Tibetan Plateau and the evolution of the Himalayan-Tibetan orogen. Lithosphere, 11(2), 209-231. Ye, Z., Gao, R., Lu, Z., Yang, Z., Xiong, X., Li, W., Shi, Z. (2021). A lithospheric-scale thrust-wedge model for the formation of the northern Tibetan plateau margin: Evidence from high-resolution seismic imaging. Earth and Planetary Science Letters, 574, 117170.

Xinjiang is located to the northern part of the Tibetan Plateau. In this paper, we link microseismic localization methods based on the neural network P and S seismic phase picking algorithm Phasenet to construct a process for automated generation of microseismic catalogs, which is applied to a oil production area A in Xinjiang. The main production activity is using the steam flooding, and a new fire flooding was added in 2018 to improve the production of oil and gas. We deploy stations centered on the fire flooding area and spread to the steam flooding area. We performed P and S seismic phase identification, automatic correlation of seismic phases, and initial and repositioning on 78 days (July 25-October 11) of continuously recorded waveforms to verify the accuracy of Phasenet pick-up times and obtain an accurate seismic catalog. The relocation results show that the microseismic events are roughly along the NE-SW striking fault spreading in the steam flooding area, and there are only a few events in the fire flooding area. The Focal depths are in the range of 0-5 km, with a mean depth of about 2 km, far deeper than the production activity depth, and the magnitude is between -1 and 4. The present-day stress direction of the large rupture passing through the area A is the same as the regional stress direction, so this area is affected by the tectonic earthquakes. Therefore, the seismicity in this region is mostly caused by the high stress level due to the influence of the regional faults and the production activities of steam flooding may promote the stress release, which triggers the microseismics.

In the past decades, several mechanisms (e.g., the crustal flow and thin viscous sheet models) and combinations of them have been proposed to explain the uplift and outgrowth of the Tibetan Plateau. These mechanisms, however, cannot account for all the features observed and the issue is still highly debated. In this study, we computed receiver functions based on teleseismic events recorded by 254 permanent and portable stations in the Tibetan Plateau and its adjacent regions, to provide large-scale constraints for the crustal deformation. A harmonic analysis, which has been recently proposed to help distinguishing a dipping Moho from crustal anisotropy, was employed here to investigate the accurate crustal anisotropy. We further applied the H-k stacking technique to determine the crustal composition using the RFs harmonic corrected or directly the RFs move-out corrected. Our results showed the following: (1) Harmonic corrections on Ps phases led to average differences of 2.6 km and 0.04 in crustal thickness and in the V_p/V_s ratio, respectively; notably, the weighting factors of the Ps, PpPs, and PpSs+PsPs phases affected the uncertainties more obviously than the harmonic corrections. (2) The crustal deformation of the central–southern Tibetan Plateau was controlled by the faulting and subduction of the Indian Plate; meanwhile, faulting played a dominated role in the crustal deformation of the northern and eastern Tibetan Plateau. (3) Widespread upper-crustal/crustal shortening and thickening should have occurred beneath the entire study region, except for the Chuan–Dian Block (which likely underwent tectonic extension). (4) Crustal partial melting might have enhanced the crustal anisotropy, and promoted the accumulation and release of strain, increasing the probability of fracture in the upper crust.

On 21 May 2021, the M_S 6.4 Yangbi earthquake in Yunnan province and the M_S 7.4 Maduo earthquake in Qinghai province occurred consecutively within ~4.3 hours in the eastern Tibetan Plateau. According to the alignment of regional fault systems and their earthquake mechanisms, both earthquakes were likely related to the lateral expansion of the eastern Tibetan Plateau. In this study, stress drops of the Yangbi and Maduo earthquake sequences are estimated from Lg-wave spectra for all M>3.0 earthquakes. The observed spectral data are corrected for the path attenuation and site effects based on a broadband Lg wave attenuation model and the site response database in east Tibetan Plateau. In both sequences, rapid decreases of stress drops were observed immediately after mainshocks, indicating abrupt stress releases by mainshocks. The relatively high stress drops observed from Yangbi foreshocks may suggest stress accumulation in the fault system. We refine the spatial distribution of stress drop for both Yangbi and Maduo sequences using HypoDD. The results demonstrate that high stress drop can be found where the orientations of seismogenic faults changed. In particular, high stress drops in the Yangbi sequence could also be associated with several earthquake clusters that were distributed roughly perpendicular to the strike of main fault, suggesting stress concentration at intersections between the main fault and secondary fault system. The complicated pattern of stress drop for the Yangbi sequence might be resulted from significant rotation of the Chuandian block in southeastern Tibet. In contrast, the fault system around the northern margin of Bayan Har block are probably smoothed and hotter due to relatively faster eastward movement, resulting in relatively lower stress drop for the Maduo aftershocks. This research was supported by the National Natural Science Foundation of China (42104055, U2139206, 41974054) and the China Seismic Experimental Site (2019CSES0103).

Zoning of Ground Motion Parameters in the Downstream Area of Yarlung Zangbo River Keyword: catalogue, seismotectonic model, potential sources in order to ensure the safety of hydropower development in the Downstream area of the Yarlung Zangbo River proposed in the 14th Five-Year Plan, the zoning of ground motion parameters in the Downstream area of the Yarlung Zangbo River is recalculated. Firstly, the missing catalogue of overseas earthquakes in the Himalayan seismic belt is supplemented, and the seismicity parameters of the Himalayan seismic belt in the seismic belt are re-counted. Secondly, the seismotectonic model of the relevant area of the East Himalayan tectonic junction is studied, and the seismogenic capacity of the main structural zones in the relevant area of the East Himalayan tectonic junction is comprehensively evaluated. Thirdly, the activity parameters of the main earthquake producing faults in the region are determined: Jiali fault, Yarlung Zangbo River fault, Bianba Luolong fault, SANGRI Cuona fault, Himalayan collision orogenic belt and Motuo fault. Fourthly, based on the division of potential sources in the five generation zoning map, the potential source areas are redivided and the spatial distribution function is calculated. Finally, the seismic risk in the Downstream Area of the Yarlung Zangbo River is analyzed and calculated by using the comprehensive probabilistic seismic risk calculation method.

Previous studies have indicated an eastward-extrusion of the Tibetan plateau since the Miocene, the sinistral strike-slip of the eastern Kunlun fault zone is strong evidence. Numerous models are proposed to explain the growth of the plateau, the most dominant of which are the crustal flow model and the extrusion model. However, The Tibetan Plateau is composed of many blocks, and a single growth model is not suitable for all. Low-resolution data do not show the fine deformation inside the crust, obscuring the true growth process of the plateau, especially at the edge of the plateau. This also results in the inability of these models to portray the interaction between the blocks. Therefore, the actual location of the East Kunlun Fracture Zone as evidence of the extrusion model becomes very unclear at the northeastern margin. In this study, We traced the eastern Kunlun fault zone by using the high-frequency receiver function technique on a dense seismic array in Roergai basin, and a total of 404 stations have been deployed. The CCP stacking was applied to create a 3D amplitude volume throughout a study area. The crust is decoupled by a ~15-20km layer, upper of that is Triassic flysch and the lower, overlapping folds. And then we identified the eastward extension of the eastern Kunlun fault zone by the flower structure and a west-to-east Moho discontinuity though the basin. It implies that the growth of Tibetan plateau is ongoing in Roergai basin. Additionally, the existence of discontinuity at the Moho in the north-south direction was first discovered in the basin along the strike of Riyueshan fault, it is considered that have a strong association with the evolution of East Kunlun fault and the expansion of Tibetan plateau.

The tectonic uplift occurring in the petroleum province of the Ordos Basin, including the Upper Palaeozoic shale, made a great decrease of pressure and leaded to underpressure as well. However, the researchers of the tectonic uplift origin of underpressure generally focus on the analysis of the geological conditions, which is an indirect method that does not involve an identification mechanism. This study focuses on the identification and calculation of the unloading underpressure caused by tectonic uplift. Firstly, the piezometric surface was identified and accurate underpressure was obtained on it. Then the pore rebound of shale during tectonic uplift was studied by experiments, and based on the results, underpressure caused by tectonic uplift is identified using the modified Bowers’ method, and how much of the abnormal low pressure is formed by the uplift was calculated using the updated mathematical model. The results show that the error between the abnormal pressure calculated from the ground surface and the piezometric surface is almost 5.64 MPa, while the present pressure calculated from the piezometric surface is almost characterised as underpressure, with a decline from northwest to southeast in the study area. Pressure of the Upper Paleozoic Shanxi Formation in the Ordos Basin decreased by 38.5 MPa, on average, during the tectonic uplift, which can be divided into two stages: in the first stage, the pressure quickly decreased to hydrostatic pressure, and the underpressure, with an average value of 7.3 MPa, mainly developed at the second stage via pore rebound. In this study, we proposed the method to obtain the piezometric surface with oil field data, modified the Bowers’ method to identify underpressure and pointed out some limitations of this common method to identify overpressure. Also, the pore rebound is misjudged in the calculation formula of underpressure, which is updated in this study.

During the collision and convergence of the Indian and Eurasian plates in the Cenozoic, the Tibet Plateau shortened in the north-south direction and the crust thickened. From Oligocene to Miocene, the Tibet Plateau changed from surface uplift to lateral extrusion. Due to the stable Yangtze Block, the crust in the eastern and southeastern margin of the Tibet Plateau has undergone strong deformation, which is a region with complex modern structures and strong activities. Many hypotheses, such as block extrusion plastic deformation and crustal flow, have been proposed for the study of crustal deformation and dynamic process in this area. The results of the study on the crustal material structure and deformation in the study area provide new evidence for the tectonic evolution and dynamic process of the crust and upper mantle in the southeastern margin of the Qinghai-Tibet Plateau. The seismic anisotropy of the upper crust in the eastern and southeastern margin of the Tibet Plateau is basically the same as the strike of the adjacent strike-slip fault zone and the direction of the GPS horizontal velocity field, which rotates clockwise around the Eastern Himalayan Syntaxis (EHS). However, the anisotropy of the mid-lower crust is obviously different from the upper crust. For example, in both the Muli-Yanyuan basin and Central Yunnan block, the seismic fast wave directions have been changed from the NE direction in the upper crust to the NW direction in the mid-lower crust. The anisotropy directions in the middle and lower crust are consistent with the distribution trends of the low velocity zone. In the range of the bottom of lower crust and the top of the upper mantle, the direction of the seismic fast wave changed again, which is consistent with the anisotropic distribution of the upper crust.

The Wave Gradiometry (WG) method measures the spatial gradients of the wavefield within a subarray to extract phase velocity, wave propagation direction, geometrical spreading and radiation pattern within a subarray (Langston 2007). The geometrical spreading extracted by the WG method is used to find the attenuation of the materials. The method is applied to the Chinarray deployed to the eastern Tibetan plateau. The array has an average station spacing of 30km, and it makes the WG method applicable to measure phase velocities and azimuthal anisotropies for periods down to 20s. The phase velocity and azimuthal anisotropy maps for periods 5-20s are inverted using ambient noise tomography, while that for periods 20-80s are obtained from WG method (Cao et al. 2020). The phase velocity dispersion curves for different azimuths with periods 5-80s are then constructed to obtain a 3D velocity and anisotropy model. Large variations in fast propagation directions (FPD) and magnitude of anisotropy (MOAs) with depth and blocks. The FPDs are positively correlated with GPS data in a large area, and with strikes of regional faults for the South Chuandian block. The low-velocity zones (LVZs) in middle to lower crust are widely distributed in the Songpan Ganze Terrence, the north Chuan-Dian block. But the LVZs are not well present across the Kunlun fault to the NE, and across the LJH fault to the SE of the Tibetan plateau. The coexistence of LVZs in middle-lower crust and uppermost mantle surrounding the Sichuan basin is dramatic and it may suggest that large-scale deformation is coupled vertically from surface to uppermost mantle. It may further suggest that the pure shearing crust shortening model, which involves the thrusting and folding of the upper crust and the lateral extrusion of blocks, may be the major mechanism causing the growth of the eastern Tibetan Plateau.