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Presentation Mode : All
Conference Day : 03/08/2021
Time Slot : AM2 11:00 - 13:00
Sections : AS - Atmospheric Sciences










Atmospheric Sciences | Tue-03 Aug


AS10-A006
A Statistical Analysis of Downward Propagation of Planetary Wave Packets in the Stratosphere Using Large Ensemble Data

Yuya MATSUYAMA#+, Toshihiko HIROOKA
Kyushu University, Japan


Our former analyses (Hirooka and Matsuyama, AOGS 16th Annual Meeting) investigated downward propagation of planetary wave packets from the stratosphere to the troposphere during winter in the Northern Hemisphere and its influence on the tropospheric circulation by the use of JRA-55 reanalysis data over the past 60 years. In the study, we partitioned the longitudinal circle into eight sectors of 45 degrees longitude and set a criterion value for each sector to the vertical component of Plumb’s (1985) wave activity flux (WAFz) at 30 hPa, to show the geographical frequency distribution of the extracted downward propagation events and features of the composited geopotential height distribution during the event occurrence. However, the numbers of the events were not enough for statistical analysis in some longitudinal sectors, for example, in the Western Hemisphere. Hence, we make a statistical analysis of the downward propagation using the large ensemble data, d4PDF (Mizuta et al., 2017). We introduce following two methods to extract strong downward propagation events. The first method is the same as in our former analysis. In this case, similar results are obtained to those based on JRA-55. Moreover, enough numbers of the events are extracted for statistical discussions, because of the large member number in d4PDF, i.e., 100 members. In the second method, a criterion is set for each grid point (2.5°×2.5°); resultantly, more detailed geographical frequency distribution of the events is successfully obtained. Although the overall feature of the geographical distributions of the events obtained by the two methods is similar each other, significant differences are found in the composited geopotential distribution during the event occurrence.

AS10-A014
Mesopause Temperature Trends and Solar Response in 2002-2019 Observed by TIMED/SABER

Xiaoran ZHAO+, Zheng SHENG#
National University of Defense Technology, China


The mesopause layer, located at the altitude where the kinetic temperature is minimum, acts as a unique tracer for radiative and dynamical processes that occur in the upper mesosphere and low thermosphere (UMLT) region. However, the mesopause temperature long-term variability over global scale is rarely reported due to a lack of data records. In this study, using temperature data collected from SABER/TIMED observations during 2002-2019, we investigate long-term trends and solar responses of the mesopause temperatures between 83°S to 83°N latitude with every 10° interval. A three-component harmonic fit is firstly applied to remove the seasonal variation from the temperature data series. Then a multiple linear regression is performed to deseasonalized temperatures versus constant, linear trend, solar activity, and geomagnetic activity terms. The results show that the mesopause temperature show a cooling trend through all latitudes, which is stronger in the Southern Hemisphere than that in the Northern Hemisphere. For high latitudes (60°-80°) in both hemispheres, significant negative trends are observed during non-summer time, while no significant trends are found for summertime. Additionally, the mesopause temperature shows significant positive responses to solar cycle, which is slightly larger in the Northern Hemisphere. A sufficiently long time interval is necessary for such analyses. Our results, based on 18-year SABER observations, are expected to be a robust measure of the mesopause temperature variability within the UMLT region.

AS10-A021
Modeling Evidence of QBO-MJO Connection: A Case Study

Seung-Yoon BACK1+, Ji-Young HAN2, Seok-Woo SON1#
1Seoul National University, Korea, South, 2Korea Institute of Atmospheric Prediction Systems, Korea, South


The boreal-winter Madden-Julian Oscillation (MJO) is modulated by the Quasi-Biennial Oscillation (QBO). The MJO becomes relatively strong during the easterly QBO (EQBO) winters but weak during the westerly QBO (WQBO) winters. To better understand their relationship, a set of WRF model experiments is conducted with varying lateral boundary conditions. The MJO event in December 2007, during EQBO winter, is chosen as a reference case. The control experiment qualitatively reproduces the observed MJO. When the lateral boundary conditions are switched with those of WQBO or strong WQBO winters, the MJO becomes weak over the Maritime Continent. All eight ensemble members exhibit enhanced outgoing longwave radiation and reduced precipitation from EQBO to WQBO, and to strong WQBO conditions, although the magnitude of changes is smaller than observations. This result, one of the first mesoscale modeling evidences of the QBO-MJO connection, suggests that the MJO is at least partly modulated by the QBO.

AS10-A023
Validation of SMILES HCl Profiles Over a Wide Range from the Stratosphere to the Lower Thermosphere

Seidai NARA1,2+, Tomohiro SATO1, Takayoshi YAMADA1, Tamaki FUJINAWA3, Lucien FROIDEVAUX4, Nathaniel. J LIVESEY4, Kaley WALKER5, Franz SCHREIER6, Jian XU7, Yvan J. ORSOLINI8, Varavut LIMPASUVAN9, Nario KUNO2, Yasuko KASAI10#
1National Institute of Information and Communications Technology, Japan, 2University of Tsukuba, Japan, 3National Institute for Environmental Studies, Japan, 4Jet Propulsion Laboratory, California Institute of Technology, United States, 5University of Toronto, Canada, 6German Aerospace Center (DLR), Remote Sensing Technology Institute, Germany, 7National Space Science Center, Chinese Academy of Sciences, China, 8Norwegian Institute for Air Research (NILU), Norway, 9Coastal Carolina University, United States, 10Tokyo Instutute of Technology, Japan


Hydrogen chloride (HCl) is the most abundant species (more than 95 %) among the inorganic chlorine compounds (Cly) in the stratosphere. HCl molecule is observed to obtain quantitative estimations of the total budget of anthropogenic chlorine in the stratosphere. In this study, global observations of HCl concentration profiles between 16 and 100 km were performed using the superconducting sub-millimeter wave limb-emission sounder (SMILES) from Oct 2009 to Apr 2010. The average SMILES HCl distribution showed an increase with altitude up to the stratopause (~45 km), approximately constant values between the stratopause and upper mesosphere (~80 km), and a decrease from the mesopause to the lower thermosphere (~100 km). This behavior was observed in all latitude regions and reproduced by the Whole Atmosphere Community Climate Model in the specified dynamics configuration (SD-WACCM). The accuracy and precision of the SMILES HCl data were quantified through comparisons with other instruments and a theoretical error analysis. We performed the comparisons versus two satellite data sets and versus balloon-borne data: the Microwave Limb Sounder (MLS) on the Aura satellite, the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on the SCISAT, and the balloon-borne TErahertz and sub-mm LImb Sounder (TELIS). The SMILES HCl profiles agree well with these three sets of measurements between 20 and 40 km. However, the SMILES HCl abundances are about 15% smaller than those of MLS and ACE-FTS at 50 – 60 km. To investigate the reason for the discrepancy and accurately estimate the budget of anthropogenic chlorine, we estimated the total systematic error for SMILES HCl based on the perturbation method and by considering the uncertainties in atmospheric temperature profiles used in the retrievals. We found that uncertainties in the air-broadening parameter and the temperature profile can contribute 40–50% of the SMILES HCl negative biases at 50–60 km.

AS22-A017
Long-term Trend of Surface Wind Speed in Korea: Anemometer Height Adjustment

Yeong-Ju CHOI+, Chang-Hyun PARK, Seok-Woo SON#, Jae-Won LEE, Dong-Chan HONG
Seoul National University, Korea, South


The long-term trend of surface wind speed in Korea is examined for 31 KMA weather stations from 1985 to 2019. Most stations, except Daegwallyeong, have several times of anemometer height changes from tens of centimeters to several meters. To minimize such height change effect on long-term wind trend, the present study adjusts anemometer height in each station to the standard height of 10 m using the power-law wind profile. This adjustment results in non-negligible trend change. For instance, the increasing surface wind speed at Suwon station, which has six times of anemometer height changes in a range of 0.8 m to 20 m, is weakened up to 67% and becomes statistically insignificant. Likewise, the decreasing trend at Andong station, with three times of anemometer height changes in a range of 10 m to 15.5 m, is weakened up to 66%. A similar weakening in long-term trend is observed in most stations regardless of positive and negative trends. However, due to the cancellation between weakened negative trends and weakened positive trends, the station-averaged wind speed trend in Korea does not change much. This result suggests that anemometer height adjustment is crucial for evaluating local wind speed trend but its impact on nation-wide wind speed trend is rather minor.

AS28-A003
WRF Simulation of Typhoon-induced Heavy Precipitation Over the Philippines: Applicability and Performance of the Multi-scale Kain-Fritsch Cumulus Scheme

Jose Angelo Arocena HOKSON#+, Shinjiro KANAE, Rie SETO
Tokyo Institute of Technology, Japan


Cumulus parameterization schemes, which handle convection processes such as those involving moisture and precipitation, have been indispensable in simulations using numerical weather prediction models such as the Weather Research and Forecasting (WRF) model. The Kain-Fritsch (KF) is one of the most-used schemes in WRF. An improved and scale-aware version of this scheme, called Multi-scale KF (MSKF), was produced in 2015. Limited studies have proven that using MSKF brings improvement to the simulated precipitation values, which are usually overestimated by KF. However, the applicability and performance of MSKF over the Philippines in simulating precipitation are yet to be verified. Herein, we examined these by simulating Typhoon Koppu and comparing the hourly and daily results with those of two other cumulus schemes – KF and Grell-Freitas (GF). Six simulations were conducted – three use cumulus schemes in high resolution (5 km, innermost domain), and three do not. Based on the results, the MSKF is applicable for use in simulating precipitations, including typhoon-induced heavy precipitations, over the Philippines. It is best used when a typhoon is at its strongest but underperforms when the typhoon is weak and nearing dissipation. However, GF performs best among the three schemes. Additionally, the results show that using cumulus schemes in high resolution (5 km, using nests) does not always improve, sometimes even deteriorate, the performance of simulations in producing accurate precipitation values. Further investigations should be conducted regarding the performance of MSKF in simulating heavy precipitations over the Philippines and neighboring areas.

AS28-A007
Rainfall Prediction with Global Climate Big Data in Chaophraya River Basin

Kiyoharu HASEGAWA#+, Shinjiro KANAE
Tokyo Institute of Technology, Japan


Subseasonal to seasonal (S2S) prediction still remains as a challenge task even today. S2S prediction refers to a lead time ranging from one to several months, which is known to result in rapidly decreasing forecast accuracy. Deep learning (DL), one of the most powerful statistical models, is expected to overcome current difficulty of S2S prediction because of its spatio-temporal locality. In this study, one-month rainfall prediction is carried out for the Chao Phraya River basin in Thailand during the rainy season from May to October, where the introduction of long-term rainfall prediction to dam management is urgently required for flood mitigation. The DL model is constructed using global maps of sea surface temperature and heat content as input values. 17 climate models output from CMIP5 dataset is used to expand the training data from 65 existing observations to 2500, which enables us to train the DL model proper. The prediction accuracy of the DL model is compared with that of the physical model and the linear regression model. The results show that the DL model is slightly inferior to the physical model, but has higher prediction accuracy than the linear model. In addition, the deep learning model has the highest prediction accuracy when trained only on the CMIP5 dataset, indicating that the DL model has potential to outperform the physical model in the future.

AS28-A032
River Runoff Simulation Using DEM Data with Different Spatial Resolutions in a Small-sized River (the Saita River, Kagawa) in Japan

Ryo NISHIKAWA#+, Masahide ISHIZUKA
Kagawa University, Japan


In recent years, large-scale floods have occurred every year in Japan. In this study, we focus on the flood of tributaries rather than the main river, which is a large-scale first-class river. Therefore, river runoff simulation using different DEM data with higher spatial resolution is required. The RRI (Rainfall-Runoff-Inundation) model, which is a distributed runoff model, is applied to the Saita river (basin area: 155.5 km2), which is a second-class river that flows through western Kagawa Prefecture. Different DEM data are used for the river runoff simulations. 

AS32-A028
Looking at Varieties in Urban Carbon Flux to Reduce Carbon Emissions in the City: a Meta-analysis from Nine CO2 Flux Observation Sites in Seoul, Korea

Chaerin PARK1+, Sujong JEONG1#, Moon-Soo PARK 2, Sang-Sam LEE3,4, Sung-Hwa PARK3,4
1Seoul National University, Korea, South, 2Sejong University, Korea, South, 3Korea Meteorological Administration, Korea, South, 4National Institute of Meteorological Sciences, Korea, South


Assessment of urban carbon cycle is a critical issue to understand the global carbon cycle. In addition, exact assessment on urban carbon cycle should be the first step to make a better solution to reduce anthropogenic carbon emissions from urban area. To understand the source and sink of atmospheric CO2 over the Seoul Capital Area (SCA), where is one of the apparent Megacities across the world, we utilize two year period CO2 flux measurements observed from nine sites at different urban landscape including baseline, vegetation, commercial, new town residential, and old town residential area. The results showed that, there is large CO2 flux variability from 1.11 kg C m-2 yr-1 to 16.28 kg C m-2 yr-1 according to its landscape even within a single city. All land type are serving as CO2 sources in SCA. The temporal CO2 flux variability of each landscape is strongly influenced by the degree of human (up to r=0.8) and vegetation (r=0.8) activity. In particular, there was a significant correlation between CO2 flux and temperature, and CO2 flux variability in vegetation and urban areas was different based on 18℃. The land type that produces the most CO2 in SCA is the old town residential area with low combustion efficiency, producing three times more CO2 than common residential area. This is thought to be due to winter heating, and it is expected that effective CO2 reduction policies could be made by utilizing these CO2 flux features by each land type. Further details will be covered in the presentation.   This study was supported by the National Research Foundation of Korea (NRF) grant funded by the Government of Korea (NRF-2019R1A2C3002868) and the Creative-Pioneering Researchers Program through Seoul National University (SNU).

AS18-A003
Investigation of the Relationship Between Infrasound and Extreme Weather

Taisei YAMAMOTO#+, Masa-Yuki YAMAMOTO
Kochi University of Technology, Japan


In this study, we investigate how extreme weather such as thunder affects the measurement of infrasound sensors, and the correlation between the yield energy obtained by thundering infrasound and heavy rain disaster. Infrasound is inaudible sound waves with a frequency of 20 Hz or less. It can be generated by huge scale geophysical everts such as thunders, volcanic eruptions, and a tsunami. Due to its low frequency, it is not easily affected by attenuation due to the viscosity of air, with the characteristics of propagating over long distances. It is known that there is a correlation between the distribution of lightning activity and the area where heavy rain occurs, and this is considered to be effective for elucidating regional meteorological mechanisms and predicting heavy rain disasters. Based on previous researches, the propagation distance of thunder induced infrasound is considered to be about 15 km. Owing to this, ten infrasound sensors were installed at around Kochi University of Technology in November 2019. Separation between the sensors were set within approximately 15 km in each other. An automatic event-extraction program using a simple threshold was created to extract thunder events from the huge amount of infrasound waveform data observed. By comparing the peak time of these waveforms observed at multiple points, it was automatically judged whether the event was simultaneously observed in a wide range of about 300 km². As a result, 354 events were extracted between January and August 2020, including 289 (82%) observed on the days of the thunder storm. In the future, we plan to automate the time integration required to determine the amount of yield energy in the successive thunders by using multiple-site infrasound observation.

AS34-A001
Ultimate: Ultra-site for Measuring Atmosphere of Tokyo Metropolitan Environment

Masaki SATOH1#+, Woosub ROH2, Shuhei MATSUGISHI1, Yasutaka IKUTA3, Naomi KUBA1, Hajime OKAMOTO4
1The University of Tokyo, Japan, 2Atmosphere and Ocean Research Institute, the University of Tokyo, Japan, 3Meteorological Research Institute, Japan, 4Kyushu University, Japan


We propose a collaboration study between numerical models and ground remote-sensing observation data over the metropolitan area of Tokyo. The initiative is called ULTIMATE (ULTra-sIte for Measuring Atmosphere of Tokyo metropolitan Environment), in which using an intensive observation data in the Tokyo area together with satellite observations, cloud microphysics schemes of numerical models are evaluated and improved. We have various kinds of remote sensing data by radars and lidars in the Tokyo area both for operational and research purposes. In particular, we will consider the use of observation data planned for ground validation of the EarhCARE satellite, which is scheduled to be launched in FY2022. We will also use the dual-polarization Doppler weather radar, which is now in operation at the Japan Meteorological Agency. As for the numerical models, we will consider the use and comparison of several models. We particularly focus on the evaluation and improvement of the Non-hydrostatic Icosahedral Atmospheric Model (NICAM), which can be used seamlessly on both global and regional domains, allowing us to quickly test the improved scheme on a global scale, compare it with satellite observations, and estimate climate sensitivity. In addition, this study aims to improve short time forecasts for several hours and beyond by improving the cloud microphysics scheme by using the local model “asuca” of the Japan Meteorological Agency.

AS34-A010
Projection of High Clouds and Its Link to Ice Hydrometeors: an Approach by Using Long-term Global Cloud-system Resolving Simulations

Ying-Wen CHEN1#+, Masaki SATOH1, Chihiro KODAMA2, Akira NODA2, Yohei YAMADA2
1The University of Tokyo, Japan, 2Japan Agency for Marine-Earth Science and Technology, Japan


This study reveals projection of high clouds related to SST change using a 20-year simulation data set conducted by a global cloud-system resolving model (NICAM) with horizontal resolution at 14-km. This study especially focuses on 1) the cloud fraction field responses to the SST pattern spatial structure, both in horizontal and vertical sections, and 2) their link to the ice hydrometeors (cloud ice, snow and graupel), which cannot be resolved by conventional GCMs. Results showed that the simulated tropical high cloud variation against to the SST variation has qualitatively similar behaviors with the observed one. The simulated high cloud behavior is mainly related to that of the cloud ice because of the layered structure of each ice hydrometeor. Under the warming climate, the relation between the tropical high cloud and SST shows a similar behavior with 1.5 times of the amplitude of that under the present climate, and this amplification of cloud fraction contributes an increase in the high cloud increase under the warming climate. We furthermore revealed the increase in the high clouds coverage in the tropics under the warming condition is directly linked to the wider spread of cloud ice in the eastern Pacific region. This study specifically reveals the pattern similarity between the global-warming responses of the high cloud fraction and the cloud ice, indicating that an appropriated treatment of cloud ice in global climate model is a key to simulating high clouds and their response to global warming. 

AS34-A004
Influence of Indochina Biomass Burning Aerosols on Southeast Asia Monsoon Onset

Yu-Yang KUO1#+, Chung-Hsiung SUI1, William LAU2, Kyu-Myong KIM3, Jainn SHI4
1National Taiwan University, Taiwan, 2University of Maryland, United States, 3NASA Goddard Space Flight Center, United States, 4NASA Goddard Space Flight Center, GESTAR, United States


Regional emissions through biomass burning (BB) in Indo-China Peninsula (ICP) are considered to influence the cloud development during March and April. However, it is difficult to identify the aerosol influence and the relevant mechanism by observational approach alone without modeling experiments. As a result, we use the Goddard Earth Observing System Model, Version 5 (GEOS-5) Atmospheric Global Climate Model (AGCM) and the NASA Unified-Weather Research and Forecasting model (NU-WRF) to simulate the aerosol influences on the monsoon development and associated cloud properties. The GEOS-5 AGCM simulations show that the aerosol-radiative forcing results in stronger anticyclonic circulation and reduced precipitation in the ICP region during the pre-onset period. The suppressed condition obstructs the convection propagation from Sumatra to ICP and therefore delays the onset of ICP summer monsoon by 2-pentads. The intensified anticyclonic flow also increases the moisture and precipitation in southeast China and Bay of Bengal. By diagnosing the heat budget in the pre-monsoon period, we show that the effect of aerosol forcing in ICP is associated with enhanced subsidence warming, reduced convective heating, and more longwave cooling, indicating an amplified regional effect of the cumulative radiative heating by circulation and convection in ICP and surrounding areas. The NU-WRF simulations with nested domain of 3-km, 9-km and 27-km resolution are used to simulate the aerosol influences on cloud properties in April 2018. Results show that the low-level stratocumulus in the South China Sea decreases and the frontal cloud in southern China increases if aerosol radiative and microphysical effect is included.

AS34-A012
Analysis and Simulations of a Heavy Rainfall Event Over Northern Taiwan on 2 June 2017

Chuan-Chi TU1#+, Yi-Leng CHEN2,1, Pay-Liam LIN1
1National Central University, Taiwan, 2University of Hawaii at Manoa, United States


With significant upstream moisture transport within the marine boundary layer (MBL), extreme torrential rain (> 500 mm day-1) occurs over Taiwan on 2 June 2017. The orographic blocking of marine boundary layer jet (MBLJ) and synoptic system-related low-level jet (SLLJ) by the Central Mountain Range results in occurrence of barrier jet off and along northwestern Taiwan. The significant horizontal moisture transport by the MBLJ and barrier jet to the mei-yu front, contributing to heavy frontal precipitation over northern Taiwan Strait and Yang-Ming Mountains over northern Taiwan. The lifting effects of moisture-laden LLJs by terrain and the mei-yu front on the development of heavy rainfall are studied using cloud-resolving model (e.g., Weather Research and Forecasting model). Also, the detailed study on the shallow mei-yu front interacting with terrain of Yang-Ming Mountains over northern Taiwan will be presented using observations and cloud-resolving model simulations.

AS18-A010
Study of the Feasibility of a CubeSat-based Hyperspectral Imager to TLE Observation from the Ground

Chien-Chung CHOU#+, Cheng-Ling KUO
National Central University, Taiwan


In response to the international trend of CubeSat launches, we designed and developed an advanced hyperspectral imaging (HSI) system mounted on CubeSat. After launching and integrating other related satellite data, then incorporate atmospheric forecasting model to monitor and forecast PM2.5 air pollution to achieve the purpose of satellite remote sensing. The HSI imager has been tested in the lab and is also complemented by real images on the ground. A motorized rotary stage is used to take a remote facade building image to simulate the CubeSat flight pushbroom scan spectral imaging. It is capable of achieving HSI efficiency, and its performance is in line with expected outcomes. Completed engineering version of the HSI imager prototype, size 11 x 12 x 20 cm3, weight less than 3.1 kg, imaging covering 450-650 nm of visible spectrum range, wavelength resolution of about 5nm. Review 2015, we developed a slitless spectrometer and conducted a sprite campaign at the Lulin Observatory. In order to have a wider FOV of ground-to-air observation, we tried to relocate the CubeSat HSI imager to a motorized rotary stage for precise and smooth 360° motion, and replace the 8mm front lens to increase FOV to 33.4°. The mounting declination axis was pointed vertically, so that the rotation around this axis allowed the imager to be in azimuth pushbroom configuration. Consider adding an Image Intensifier (VideoScope VS4-1845) to meet the requirements for low-light image capture. Finally, develop a practical technology and control software and adjust the parameters to complete the verification operations of the acquisition of TEL HSI panoramic cubic data and the spectral analysis of ground observation.



AS06-A008 | Invited
Roles of Interaction of Convection, Atmospheric and Ocean Circulations in Shaping the Tropical Precipitation Distribution in Global Climate Models

Guang ZHANG#+
University of California San Diego, United States


The distribution of tropical precipitation, especially in the Intertropical Convergence Zone (ITCZ), is a result of complex interactions among convection, clouds, large-scale atmospheric circulation, sea surface temperature (SST), and the upper ocean circulation. The global climate models (GCMs) have tremendous difficulty in simulating it for reasons not well understood. This talk will first review the past research in this area, with a focus on the roles of 1) the southeastern Pacific marine stratus clouds and associated warm SST biases; 2) the extratropical shortwave absorption biases over Southern Ocean; and 3) convective parameterization in contributing to the problem. I will then present results demonstrating the interaction processes that lead to the double ITCZ in the NCAR CESM1 in the central and eastern Pacific and ways to improve the precipitation simulation in the tropics. It will be shown that many factors contribute to the double ITCZ biases, including southeastern Pacific SST, northern ITCZ, and equatorial cold tongue. All these are in one way or another related to convection parameterization.

AS06-A014
Understanding Changes in Tropical Circulations in a Future Warmer Climate Using a Cloud-resolving Model and a Conceptual Model

Sramana NEOGI#+, Martin SINGH
Monash University, Australia


The interaction between large-scale tropical circulations and moist convection has been the focus of a number of studies. However, projections of how the large-scale tropical circulation may change under global warming remain uncertain because our understanding of this interaction is still limited. Here, we use a cloud-resolving model (CRM) coupled with a supra-domain scale (SDS) parameterization of the large-scale circulation to investigate how tropical circulations driven by sea-surface temperature (SST) gradients change in a future warmer climate. Two popular SDS parameterisation schemes are compared; the weak temperature gradient approximation and the damped-gravity-wave approximation. In both cases, the large-scale vertical velocity is related to the deviation of the simulated density profile from a reference profile taken from the same model run to radiative-convective equilibrium. We examine how the large-scale vertical velocity profile varies with surface temperature for fixed background profile (relative SST) as well as how it varies with the surface temperature of the reference profile (background SST). The domain mean vertical velocity appears to be very top-heavy with the maximum vertical velocity becoming stronger at warmer surface temperatures. The results are understood using a simple model for the thermodynamic structure of a convecting atmosphere based on an entraining plume. The model uses a fixed entrainment rate and the relative humidity from the cloud-resolving model to predict a temperature profile. The vertical velocities calculated from these predicted temperature profiles is similar to the vertical velocity structures and their behaviour in a warmer climate that we see in the CRM simulations. The results provide insight into large scale vertical velocity structures simulated by SDS parameterisation schemes, providing a stepping stone to understanding the factors driving changes to the large-scale tropical circulation in a future warmer climate.

AS06-A005
Observed Long-term Trends of the Atmospheric Circulation and Moist Energies

Christian FRANZKE1#+, Nili HARNIK2
1Pusan National University, Korea, South, 2Tel Aviv University, Israel


The atmospheric circulation response to global warming is an important problem which is theoretically still not well understood. This is a particular problem since climate model simulations provide uncertain, and at times contradictory, projections of future climate. In particular, it is still unclear how a warmer and moister atmosphere will affect the atmospheric circulation and mid-latitude storms. Here we perform a trend analysis of various atmospheric circulation measures and of the budgets of dry and moist static energy transports, which will contribute to our understanding of the role of moisture in circulation changes. Our analysis is based on the JRA-55 reanalysis data covering the period 1958 through 2018 for both winter and summer seasons. We focus our analysis on zonal mean quantities for the full latitudinal circles as well as for the Atlantic and Pacific sectors. We find significant trends in zonal wind, eddy kinetic energy, Eady growth rate, diabatic heating rates, and specific humidity. The zonal wind changes appear to be in thermal wind balance. We also find that the increase in specific humidity is intensifying the trend in eddy moist static energy transport when compared with eddy dry static energy transport. Since band-pass filtered eddy moist static energy transports are related to storm tracks this suggests that increasing moisture in the atmosphere is contributing to the intensification and meridional shifts of storm tracks. Furthermore, our results suggest that global warming predominantly enhance heat fluxes and to a lesser extend momentum fluxes.

AS06-A006
Evaluate the Aggregation in Moisture Space of CMIP6 Models

Jin-De HUANG+, Wei-Ting CHEN#, Chien-Ming WU
National Taiwan University, Taiwan


This study aims to evaluate the aggregation in moisture space of ERA-Interim reanalysis data (ERA-I) and Coupled Model Inter-comparison Project Phase 6 (CMIP6) models. The moisture space, conditionally sampling data based on the column water vapor or column saturation, can effectively separate the different characteristics between dry and moist areas. This method is widely applied in idealized simulations to study the mechanisms of aggregation. The aggregation in the real world is regarded as the large-scale circulation, such as the Hadley and Walker circulation. The 35-year (1980-2014) daily column saturation in the tropical region (30S-30N) is investigated in the moisture space to understand the performance of the aggregation in CMIP6 models compared to ERA-I. The reanalysis has a double-peak distribution of the column saturation, which indicates the separation of the dry and moist areas. Some models can better represent the aggregation, while the distribution in other models has a bias shifting toward the more moist region. A simple parcel model is used to diagnose the relationship between the large-scale circulation and the environmental stability in the moisture space. The transition of the environmental stability at 60 % is corresponding to the boundary of the ascending circulation in ERA-I. Those models with the moist bias do not capture the coupling between the circulation and stability. We will further evaluate the changes in aggregation in the moisture space under the warming scenario.

AS06-A003
How Well Do Recent Reanalyses Represent the Dry-to-wet Season Transition over the Southern Amazon?

Jonathon WRIGHT#+, Liu ZHANG, Lan DAI
Tsinghua University, China


Rapid land-use changes and repeated severe droughts have placed the southern Amazon ecosystem under increasing stress in recent years. Key mechanisms behind the dry-to-wet season transition in this region remain unclear, and it is uncertain how this transition might change in future. Atmospheric reanalyses are potentially useful for studying these mechanisms; however, such analyses must account for uncertainties associated with parameterized physics and assimilation-related adjustments that disrupt temperature and moisture budget calculations. Here, we examine the performance of ERA5 and MERRA-2 with respect to the timing and mechanisms of the dry-to-wet season transition over the southern Amazon. Average wet season onset is slightly earlier than observed in ERA5, but interannual variability is captured well. MERRA-2 also performs well on average after 1998, but struggles to capture observed interannual variations and relationships with sea surface temperature. Atmospheric moistening during the transition is accomplished mainly through physical (deepening shallow convection) and dynamical (increasing moisture flux convergence) processes in ERA5. By contrast, large positive assimilation increments in lower tropospheric humidity play a central role in MERRA-2. Likewise, we find an earlier, smoother transition to deep convective heating in ERA5 relative to MERRA-2, with a vertical structure that better promotes the regional-scale convergence needed for wet season onset. Analysis of the vertically-integrated moisture budgets shows that the data assimilation contribution in MERRA-2 is comparable in magnitude to the physical and dynamical terms through much of the transition. The net result is a more thermally-driven monsoon onset in MERRA-2, as opposed to a more moisture-driven onset in ERA5. Although the evolution in ERA5 is more consistent with observations, the large differences between the two reanalysis representations may present an opportunity to deepen understanding of common issues in the dry-to-wet season transition as represented in climate models.

AS06-A004
Toward Tropical Circulation Vector Vorticity Cloud-resolving Model (TCVVM)

Jin-De HUANG+, Chien-Ming WU#, Chun-Yian SU
National Taiwan University, Taiwan


The vector vorticity cloud-resolving model (VVM) was developed based on the three-dimensional vector vorticity equations (Jung and Arakawa 2008). The use of the vorticities as the prognostic variables in VVM can better capture the circulation induced by the local buoyancy gradient which plays a critical role in the development of the aggregated convection (Chen and Wu 2019). In the tropics, convective aggregation is regarded as a process to understand the cyclogenesis, the initiation of the Madden-Julian Oscillation, and the impacts of the convection on the large-scale circulation. This study extends VVM to the tropical circulation VVM (TCVVM), which covers the tropical region with mesoscale permitting resolution. TCVVM can be used to study the interactions between the large-scale circulation and the convective-scale systems. The free-slip wall boundary conditions are implemented in the vorticity equation to simulate the tropical region with beta effects to achieve this goal. The unified parameterization with Relax Arakawa-Schubert scheme (URAS) is also implemented to better represent the evolution of the convective systems. In the simulation with URAS, the outgoing longwave radiation (OLR) shows that the convection develops with broad high and middle clouds. On the other hand, the high clouds occur in a sporadic distribution, and the convection organization is less evident in the simulation without URAS. The results suggest that the convection tends to develop on the larger horizontal scale when URAS is applied. In the future, the land-sea distribution of the maritime continent will be included in TCVVM to study the interactions between MJO and the diurnal cycle.



AS01-A011 | Invited
WMO Activities in Promoting Cooperation of Members on Climate Change Adaptation and Strengthening Early Warning Systems

Roberta BOSCOLO#+, Robert STEFANSKI, Maxx DILLEY
World Meteorological Organization, Switzerland


Between 1970 and 2019, 79% of disasters worldwide involved weather, water, and climate-related hazards. These disasters accounted for 56% of deaths and 75% of economic losses from disasters associated with natural hazards reported during that period. As climate change continues to threaten human lives, ecosystems and economies, risk information and early warning systems (EWS) are increasingly seen as key for reducing these impacts. The majority of countries, including 88% of least developed countries (LDCs) and small island developing states (SIDS), that submitted their Nationally Determined Contributions (NDCs) to UNFCCC have identified EWS as a “top priority”.  The World Meteorological Organization (WMO) is a specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology and geophysics. Addressing urgency of concrete actions on climate change adaptation, WMO coordinates cooperation of Members on strengthening EWS. In this presentation, we highlight progress made in EWS capacity, with focus on Asia and Oceania, and identify where and how governments can invest in effective EWS to strengthen countries’ resilience to multiple weather, water and climate-related hazards. Strategic recommendations to improve the implementation and effectiveness of EWS worldwide include (i) Invest to fill the EWS capacity gaps, particularly in LDCs, in Africa and in SIDS, and (ii) Focus investment on turning early warning information into early action, through improved communication and preparedness planning. Being prepared and able to react at the right time, in the right place, can save many lives and protect the livelihoods of communities everywhere.

AS01-A021 | Invited
Seamless Forecasting From Sub-seasonal to Seasonal Time Scales

Andrew W. ROBERTSON1#+, Frederic VITART2
1Columbia University, United States, 2European Centre for Medium-Range Weather Forecasts, United Kingdom


The World Weather Research Program (WWRP) and World Climate Research Program (WCRP) launched a joint research initiative in 2013, the Sub-seasonal to Seasonal prediction project (S2S) whose main goal is to improve forecast skill and understanding of the sub-seasonal to seasonal timescale and to promote its uptake by operational centres and exploitation by the application communities. A major achievement of this project has been the establishment of an extensive database containing sub-seasonal (up to 60 days) near real-time forecasts (3-weeks behind real-time) and re-forecasts. This presentation will describe the S2S project and show some results from the analysis of the S2S database. This presentation will also review the main achievements of the S2S project, including the launch of the S2S Real-Time Pilot which provides real-time sub-seasonal forecasts to 16 application projects for a 2-year period and the launch of an S2S artificial Intelligence/Machine Learning competition in 2021.

AS01-A008
Climate Risk and Early Warning Systems (CREWS) International Initiative: Assisting Most Vulnerable Countries with Climate Change Adaptation

Yuriy KULESHOV1,2#+
1Bureau of Meteorology, Australia, 2Royal Melbourne Institute of Technology University, Australia


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. In Papua New Guinea (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. 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 PNG are described. 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 and the PNG Capacity Development Project PNG-CDP), 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. PNG-CDP is a project which is focused on enhancing the meteorological observation network in the country. Synergies between the projects are outlined.

AS01-A013
Sub-seasonal to Seasonal (S2S) Climate Prediction for Australia and the Pacific Island Countries

Andrew WATKINS1#+, Yuriy KULESHOV1,2
1Bureau of Meteorology, Australia, 2Royal Melbourne Institute of Technology University, Australia


The importance of sub-seasonal-to-seasonal (S2S) climate prediction to improve climate change adaptation, resilience and decision-making is recognized by users from climate-sensitive sectors around the world. S2S climate outlooks at various levels – national, regional and global - are operationally produced by National Meteorological and Hydrological Services (NMHSs), Regional Climate Centres (RCCs) and the World Meteorological Organization (WMO) providing users with vital information about state of the El Niño-Southern Oscillation and its likely development, as well as S2S climate outlooks for air temperatures, rainfall, ocean temperatures and other variables. Recently, a high-resolution dynamical climate model – the Australian Community Climate Earth-System Simulator (ACCESS) – was introduced at the Australian Bureau of Meteorology (BoM) for use in weather and climate prediction. Since August 2018 the BoM's operational climate forecast system for multi-week, monthly, seasonal and longer-range climate outlooks is ACCESS–Seasonal (ACCESS–S). The atmosphere and land model components of ACCESS–S operate at an approximate global resolution of 60 km, providing far greater detail than its predecessor, POAMA (Predictive Ocean and Atmosphere Model for Australia), which had an approximate resolution of 250 km. For decades, seasonal climate prediction in Australia and the Pacific Island Countries was based on statistical models. However, in a rapidly changing environment the skill of statistical models - which use past relationships as an indication of future state - deteriorates. Hence dynamical climate models such as ACCESS, which are based on laws of physics rather than historical correlations, are preferable for forecasting climate on time scales from weeks to months and beyond.  The WMO Global Producing Centre for Long-range Forecasts (GPC LRFs) at BoM disseminates ACCESS-S S2S climate prediction products through a specialised portal. Availability of these products, accompanied by training programs in projects such as WMO-CREWS, strengthens the capacity of NMHSs in the Pacific and other regions.

AS01-A002
SWCEM and ACCESS-S Products for "Climate Information Services for Resilient Development Project in Vanuatu"

Sunny SEUSEU1#+, Yuriy KULESHOV2,3
1Secretariat of the Pacific Regional Environment Programme, Vanuatu, 2Bureau of Meteorology, Australia, 3Royal Melbourne Institute of Technology University, Australia


Vanuatu is one of the world's most vulnerable countries to natural disasters. The main climate hazards for Vanuatu include tropical cyclones, heavy rainfall resulting in flooding, extended periods without rain causing drought, rising sea levels threatening coastal environments and property, as well as sea temperature increase and ocean acidification impacting highly valuable coastal ecosystems and resources (including coral reefs, seagrass and fisheries). The Vanuatu Klaemet Infomesen blong Redy, Adapt mo Protekt (Van-KIRAP) project is delivering climate science to support decision makers and communities in Vanuatu to prepare for and adapt to climate variability and change. Van-KIRAP will support the Vanuatu Meteorology and Geohazards Department (VMGD) to provide five target sectors - tourism, agriculture, infrastructure, water management and fisheries – and their stakeholders with climate information ready to be used in current and planned activities. Van-KIRAP implementing partners – SPREP, VMGD and Australian Bureau of Meteorology (BoM) – are working closely with five target sectors to co-design user-centred Climate Outlook Bulletins. WMO Space-based Weather and Climate Extremes Monitoring (SWCEM) products were specifically designed to assist with extreme precipitation monitoring, including drought and heavy precipitation. WMO Global Producing Centre for Long-range Forecasts (GPC LRFs) Melbourne hosted by the BoM disseminates sub-seasonal to seasonal (S2S) climate information from the Australian Community Climate Earth-System Simulator – Seasonal (ACCESS-S) on global, regional and national scales, including climate forecast products for Vanuatu. This presentation provides an overview of a conceptual design of Climate Outlook Bulletins for tourism, agriculture, infrastructure, water management and fisheries, with emphasis on utilising WMO SWCEM satellite-derived precipitation products for climate monitoring and ACCESS-S S2S products for climate prediction.

AS01-A012 | Invited
Geographic Information System for Drought Risk Mapping - Drought Risk Analyser Web App

Chayn SUN1, Suelynn CHOY1#+, Yuriy KULESHOV2,1
1Royal Melbourne Institute of Technology University, Australia, 2Bureau of Meteorology, Australia


Droughts have a significant negative impact on populations and economy, and it is projected that anthropogenic climate change will result in increase of drought frequency and severity. To improve preparedness for drought, decision-support tools which provide comprehensive information about current dry conditions are essential. In this presentation, we provide an overview of a conceptual design for a Drought Risk Analyser (DRA) – a web-based information App for drought risk mapping designed using geographic information system (GIS). The developed DRA is based on combining Drought Hazard/Vulnerability/Exposure Indices (DHI, DVI and DEI respectively) into a final Drought Risk Index (DRI). Modern technology - space-based observations - provides global uniform coverage and in this way complements conventional in situ observations. Recognising the importance of enhancing the capacity of meteorological services in providing users with accurate precipitation monitoring products, in 2017 the World Meteorological Organization (WMO) established the Space-based Weather and Climate Extremes Monitoring (SWCEM) international initiative; the first demonstration project was successfully implemented in East Asia and Western Pacific. WMO SWCEM products were specifically designed to assist with extreme precipitation monitoring, including drought. In our conceptual design of the DRA, WMO SWCEM products were used to assess drought hazard and map DHI. This is a novel approach which we first explored for Australia. The developed methodology of using space-based observations for assessing drought hazard could be applied for developing similar web-based information tools in drought-prone areas of other countries. 

AS01-A022
Drought Detection Over Papua New Guinea Using Satellite-derived Products

Zhi-Weng CHUA#+
Bureau of Meteorology, Australia


This study evaluates the World Meteorological Organization's (WMO) Space-based Weather and Climate Extremes Monitoring (SWCEM) Demonstration Project precipitation products over Papua New Guinea (PNG). The products evaluated were based on remotely-sensed precipitation, vegetation health, soil moisture, and outgoing longwave radiation (OLR) data. The satellite precipitation estimates of the Climate Prediction Center/National Oceanic and Atmospheric Administration's (CPC/NOAA) morphing technique (CMORPH) and Japan Aerospace Exploration Agency's (JAXA) Global Satellite Mapping of Precipitation (GSMaP) were assessed on a monthly timescale over an 18-year period from 2001 to 2018. Station data along with the ERA5 reanalysis were used as the reference datasets for assessment purposes. In addition, a case study was performed to investigate how well the SWCEM precipitation products characterised drought in PNG associated with the 2015–2016 El Niño. Overall statistics from the validation study suggest that although there remains significant variability between satellite and ERA5 rainfall data in remote areas, this difference is much less at locations where rain gauges exist. The case study illustrated that the Vegetation Health Index (VHI), OLR anomaly and the Standardized Precipitation Index (SPI) were able to reliably capture the spatial and temporal aspects of the severe 2015–2016 El Niño-induced drought in PNG. Of the three, VHI appeared to be the most effective, in part due to its reduced incidence of false alarms. It is concluded that SWCEM satellite-derived precipitation products could be recommended for operational use for drought detection and monitoring in PNG, and that even a modest increase in ground-based observations will increase the accuracy of satellite-derived observations remotely.

AS01-A029
Drought Risk Assessment for PNG

Isabella AITKENHEAD#+
Bureau of Meteorology, Australia


Increased intensity and frequency of climate extremes and disaster’s resultant of a warming global climate are already seen to have destructive impacts on the world’s most vulnerable communities. Future effective climate adaptation and disaster risk reduction (DRR) is vital for the resilience of vulnerable communities. Vulnerable communities requiring efficient DRR and resilient climate adaptation include small island developing states (SIDS) and least developed countries (LDCs) in the Pacific. In this study, a disaster risk analysis, with focus on drought, was conducted for a vulnerable country in the Pacific - Papua New Guinea (PNG). PNG has experienced severe impacts from natural hazards in the past. Notably, the 1997/98 El Niño contributed to severe drought in PNG causing immense loss of life, destruction of crops, and forest fires subsequently causing regional pollution problems. Remote communities in PNG continue to have limited resources and capacity to effectively manage such impacts. Local communities in PNG must be able to self-initiate strategies that are effective and appropriate to them. In this context, community-scale DRR is an increasingly important focus for PNG. The importance of developing a unique drought risk index, specific to the area of investigation when assessing agricultural drought risk on local community scales, has been consistently emphasised in previous studies on effective Early Warning Systems (EWSs) and disaster risk management. In this study, space-based monitoring products were used when gathering data for index calculations to ensure accuracy. Historical data detailing conditions before past disaster events which have occurred in PNG were used to develop a risk index for that period to see if it would have indicated high disaster risk or not. GIS methodology for mapping risk in the study region was used to display risk levels. Results of drought risk assessment for PNG are presented.





AS09-A021
The Nonlinear Response of Fine Particulate Matter Pollution to Ammonia Emission Reductions in North China

Zehui LIU1#+, Lin ZHANG1, Qi CHEN1, Mi ZHOU1, Youfan CHEN1, Dan CHEN2, Yuepeng PAN3, Tao SONG3, Dongsheng JI4
1Peking University, China, 2Institute of Urban Meteorology, China, 3Chinese Academy of Sciences, China, 4Institute of Atmospheric Physics, Chinese Academy of Sciences, China


Recent Chinese air pollution actions have significantly lowered the levels of fine particulate matter (PM2.5) in North China via controlling emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) together with primary aerosols, while the emissions of another precursor, ammonia (NH3), have not yet been regulated. This raises a question that how effective the NH3 emission controls can be on the mitigation of PM2.5 pollution along with the reduction of SO2 and NOx emissions. Here we use a regional air quality model to investigate this issue focusing on the PM2.5 pollution in North China for January and July 2015. We find that the efficiency of the PM2.5 reduction is highly sensitive to the NH3 emission and its reduction intensity. Reductions in the population-weighted PM2.5 concentration in the Beijing-Tianjin-Hebei region are only 1.4-3.8 μg m-3 (1.1-2.9% of PM2.5) with 20-40% NH3 emission reductions, but could reach 8.1-26.7 μg m-3 (6.2-21%) with 60-100% NH3 emission reductions in January 2015. Besides, the 2015-2017 emission changes (mainly reduction in SO2 emissions) could lower the PM2.5 control efficiency driven by the NH3 reduction by up to 30% for high NH3 emission conditions, while lead to no change or increase in the efficiency when NH3 emissions become low. NOx emission reductions may enhance the wintertime PM2.5 pollution due to the weakened titration effect and can be offset by simultaneously controlling NH3 emissions. Our results emphasize the need to jointly consider NH3 with SO2 and NOx emission controls when designing PM2.5 pollution mitigation strategies.

AS09-A033 | Invited
Ship, Aircraft and Satellite Observations of Greenhouse Gases and Air Pollutants in the Monsoon Asian Region

Hiroshi TANIMOTO1#+, Astrid MUELLER1, Tamaki FUJINAWA1, 2, Hideki NARA1, Shin-ichiro NAKAOKA1, Takafumi SUGITA1, Isamu MORINO1, T. MACHIDA1, Yasunori TOHJIMA1, Satoshi INOMATA1, Akihiko KUZE3, 2, Kohei IKEDA1, Yosuke YAMASHITA1, Tomohiro SATO4, Yasuko KASAI5, Tsuneo MATSUNAGA1, Nobuko SAIGUSA1
1National Institute for Environmental Studies, Japan, 2, , 3Japan Aerospace Exploration Agency, Japan, 4National Institute of Information and Communications Technology, Japan, 5Tokyo Instutute of Technology, Japan


The Monsoon Asia region is home to many countries undergoing rapid industrialisation in response to the demand for economic growth. In addition, the region is characterized by complex meteorology, with regular pollution transport from seasonal and perennial anthropogenic sources. The National Institute for Environmental Studies (NIES) has been operating a long-term program for monitoring trace gases of atmospheric importance in Asia and the Pacific. Both long-lived greenhouse gases (LLGHGs, e.g., carbon dioxide, methane, nitrous oxide, etc) and short-lived climate forcers (SLCFs, e.g., tropospheric ozone, black carbon, carbon monoxide) are observed with commercial cargo vessels and passenger aircraft that are in regular operation in constant routes for long periods over a wide area between various ports/airports. These routine platforms offer the advantage of systematic measurements of trace gases and aerosols, providing long-term datasets for pristine background air over the Pacific Ocean and regionally polluted air around Asia. In addition, there is an ongoing plan to launch a satellite observing CO2, CH4, and NO2, named “Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW)”. Hence, the challenge imposed to us is how to combine these multiple observing platforms into one integrated system that can be best used for better understanding of the changing emissions and resulting impacts on the atmospheric composition, including LLGHGs and SLCFs. We will provide an overview of the program, provide some recent highlights, and discuss future perspectives.

AS09-A004 | Invited
Sources and Gas/Aerosol Partitioning of Atmospheric Ammonia and Amines and Their Particulate Partners in Coastal and Marine Atmospheres

Xiaohong YAO#+
Ocean University of China, China


In the last decade, we studied sources and gas/aerosol partitioning of atmospheric ammonia and amines and their particulate partners in coastal and marine atmospheres. No significant change in seasonal average NH3gas concentration in winter continental atmospheres of northern China over the decade, although the concentrations of gaseous dimethylamine (DMAgas) increased by approximately one order of magnitude. The concentrations of trimethylamine (TMAgas) surprisingly decreased by approximately two orders of magnitude. The unique changes of the observed basic gases were possibly related to the application of Selective Non -Catalytic Reduction to remove NOx and a large decrease in manure application. In marine atmospheres of China marginal seas, the concentrations of NH3gas observed during winter cruise campaigns were comparable to those observed during other seasonal campaigns, but those of DMAgas and TMAgas in winter campaigns were substantially larger possibly because of their enhanced accumulation in sea microlayer and the release to the atmosphere under favorable ambient conditions. The accumulation also led to the primary sea-spray aerosols contained DMAH+ and TMAH+ increased by 1-2 orders of magnitude than those observed in other seasons. In general, China marginal seas acts as a net sink of NH3gas because of the long-range transport from the upwind continents except for the bloom decay period. The seas acts as a net source of TMAgas and particulate TMAH, but acted alternatively as a net source or a net sink for both DMAgas and particulate DMAH+. Gas/aerosol partitioning of TMAgas and particulate TMAH+ did not follow previously recognized thermodynamic equilibria, but NH3gas and DMAgas with their particulate counterparts did.

AS09-A008
Impacts of a Spring Dust Storm on Beijing Air Quality: Implication of UI-WRF-Chem in Studying Long-range Transport Events

Huanxin ZHANG#+, Jun WANG, Nathan JANECHEK, Cui GE, Lorena Castro GARCIA, Meng ZHOU, Tong SHA, Yanyu WANG
The University of Iowa, United States


The Multi-Angle Imager for Aerosols (MAIA), scheduled to launch in 2022, seeks to understand how different types of particulate matter (PM) affect human health with a focus on 12 Primary Target Areas (PTAs) globally, which are large metropolitan areas. The MAIA investigation integrate satellite, ground observations and chemical transport models to generate maps of surface total and speciated PM for the PTAs. Here, we have developed a Unified Initial and boundary conditions for WRF-Chem (UI-WRF-Chem) model that serves as the chemical transport model for the MAIA mission. These developments include: (a) application of NASA GEOS-5 data to provide both meteorological and chemical initial and boundary conditions for performing WRF-Chem forecasts of air quality in a finer spatial resolution, (b) a stand-alone emission preprocessor that ingests both global and regional anthropogenic emission inventories as well as fire emissions,(c) application of MODIS land cover data to update surface properties, (d) application of GLDAS and NLDAS data to constrain surface soil conditions, and (e) a new soil NO emission scheme. The development of (a) is motivated by the fact that the GEOS 5 system assimilates satellite observations of aerosols. Utilizing GEOS 5 aerosol products to provide boundary conditions for finer scale simulations of WRF-Chem provides a computationally efficient way of studying the long-range transport of aerosols. To illustrate this capability, we show the case study of a dust storm that impacted Beijing, a PTA, March 26 – 28, 2018 transported from the Taklimakan and Gobi deserts. We perform UI-WRF-Chem simulation to study this dust intrusion with MERRA-2 data proving boundary conditions for dust and non-dust aerosol species. We use satellite, ground observation and MERRA-2 data to evaluate model performances. Preliminary results show that 4 km UI-WRF-Chem runs show more resolved spatial signals compared with MERRA-2 simulated surface PM2.5 concentrations.

AS09-A023
Evaluating Wrf-chem Aerosol Transport Capabilities Over South-east Asia: A Case Study for the 2019 Smoke Event

Santo V. SALINAS1#+, Srikanth MADALA1, Li TAN1, Jun WANG2
1National University of Singapore, Singapore, 2The University of Iowa, United States


Singapore is regularly affected by severe smoke/haze episodes due to regional forest fires and open biomass burning that occur during the region’s season of draught and drynesses. First satellite observations of such events were recorded in 1997 and subsequently in 2006, 2010, 2013, 2015 and more recently in 2019. However, the high degree of cloud cover over the South-East Asia (SEA) region poses a substantial handicap to satellite observability even with the availability of high frequency satellite observations. To complement satellite and in-situ observations, tools such as numerical modeling is used to generate model representation of smoke/haze transport and evolution over Singapore and the SEA region. In the present work, we present model implementation and results for the core part of the SEA smoke event of 2019 (September 2019). We conducted simulations within a single domain grid using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) at a spatial resolution of 9 km × 9 km. Simulations are initialized by both, the 1x1 degree, 6 hourly Final Analysis (FNL) data and 0.5x0.5 degree, 3 hourly Global Forecasting System (GFS) data for all meteorological fields for initial and boundary conditions. The Naval Research Laboratory’s Fire Locating and Modeling of Burning Emissions (FLAMBE) emission inventory with 800 m injection height is used as as source allocation framework. Results show that, WRF-Chem is able to capture the spatial distribution of smoke/haze reasonably well for both FNL and GFS data sets. A slight under prediction of the PM2.5 mass concentration for FNL_30days simulations and over prediction with FNL_4days and GFS_4days simulations when compared to five available PM2.5 observation stations over Singapore. Qualitative and quantitative comparisons between the model results show that the FNL_30days best simulated smoke transport event over the study region, followed by FNL_4days and GFS_4days.

AS09-A029
Tracking Prevailing Dust Aerosol Over the Air Pollution in Central China with Integrated Satellite and Ground Observations

Minghui TAO1#+, 2, Zhongting WANG3
1The Aerospace Information Research Institute of the Chinese Academy of Sciences, China, 2, , 3Center for Satellite Application on Ecology and Environment, China


Besides intense dust storms, transport of dust particles in the extensive deserts of East Asia have been rarely concerned. In this study, we present a comprehensive insight into sources, transport process, and potential influence of the prevalent coarse particles in central China during October 2020 based on integrated satellite and ground observations. Although dust events are usually considered concentrated in spring, satellite observations show that dust sources are usually active during fall. Thick dust layers with high uplifted altitudes at ~5 km are found in their downstream path, which can be carried to northern China and even the Sichuan Basin by predominant northwestern winds at 700 hPa. Despite a lack of air masses directly from active dust sources, dust plumes from both Taklimakan Desert and Gobi deserts can be blown to central China in their transport path or when they have arrived over northern and eastern China. Unlike dust storms with strong winds cleaning local atmospheric pollutants, these floating dust plumes tend to suspend over the air pollution near surface. In particular, the slow dust-pollution mixing process in central China can last for as long as ~3-4 days due largely to the common temperature inversion in fall. Despite a dominant contribution (> 50%) in particle pollution, these dust transport with much smaller scales than dust storms can be unnoticeable. Our results suggest that more attention should be paid to the role of these unnoticeable but frequent dust plumes in regional atmospheric environment and climate effects.

AS09-A042
Evaluation of PM2.5 Surface Concentrations Simulated by Nasa’s MERRA Version 2 Aerosol Reanalysis Over the Tibetan Plateau

Juanxiao GONG1,2#+, Jun WANG2, Shichang KANG3, Xiangao XIA3, Huanxin ZHANG2, Lorena Castro GARCIA2, Yi WANG2
1Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences., China, 2The University of Iowa, United States, 3Chinese Academy of Sciences, China


The Tibetan Plateau (TP) and its surroundings are known as the Third Pole. While the Tibetan Plateau air is overall clean, but its surrounding areas are associated with some of the most intensive air pollution emissions in the world. Little is known about the spatial and temporal variability of atmospheric pollution and their transport pathways to the Tibetan Plateau. Here, we study this topic by a combined use of three-year (2011-2013) surface-based measurements of PM2.5 and the decadal Modern-Era Retrospective analysis for Research and Applications, Version 2, or MERRA-2 dataset. The results showed that MERRA-2 generally underestimates the ground measurement PM2.5 mass concentration. The correlation coefficient between MERRA-2 and observation generally lower (<0.5) than in other regions, like the North China Plain (0.77). However, MERRA-2 overall captures the PM2.5 concentration seasonal variations, especially in the pre-monsoon and monsoon season, but in winter it was simulated worst. The ratio of BC and OC to PM2.5 from MERRA-2 generally underestimates measurement. This may be because MERRA-2 does not assimilate the local biomass combustion emission source. The spatial seasonal pattern of PM2.5 concentration using MERRA-2 is winter greater than post-moon greater than pre-moon greater than moon season in the central TP, and in the north TP, the pattern is pre-monsoon greater than monsoon greater than post-monsoon greater than winter. The highest PM2.5 in the pre-monsoon and winter period in the central TP is mainly due to transmission from south Asia and local emission, and the highest PM2.5 in the pre-monsoon and monsoon period in the north TP is mainly due to dust and local emission. The conclusion can provide a theoretical basis for the use of MERRA-2 aerosol reanalysis over the Tibetan Plateau.

AS09-A024
Physical and Chemical Effects of Diurnal Evolution of NOx Concentration in Idealized Simulations

Yu-Hsuan FAN+, Chien-Ming WU#
National Taiwan University, Taiwan


This study aims to investigate the diurnal evolution of local emissions based on the physical and chemical views in idealized simulations with ocean, land, and mountain distribution. Under the weak synoptic condition in Taiwan during the winter, it is difficult to understand how local emissions influence the air quality due to interactions between the local circulation and complex topography. Idealized simulations using the VVM coupled to a chemistry parameterization are performed to study the impacts of physical and chemical processes on the local emissions. Two nitrogen reactions are applied to simplify the chemical interactions to a conservative chemical system, and the local emissions are based on the real air pollution data in Taiwan (TEDS 10.1). The traffic emission is broadly distributed in the urban region in the plain areas, while the high-concentration industrial pollutants are emitted in very limited coastal areas. In the plane areas, the industrial emissions are majorly controlled by the sea breeze in the daytime, and the highly polluted air moves with the sea breeze front. On the other hand, the traffic emissions are influenced by the planetary boundary layer, and the concentration of the pollutants is diluted in the morning due to the development of the boundary layer. In the mountain area, both emissions are transported by the sea breeze from the plain areas in the afternoon. The concentration of industrial emission is slightly larger because of the preference for diffusing horizontally rather than vertically. Besides, the transformation between NOx in the daytime is dominated by photodissociation, and the increase of ground-level ozone concentrations tends to worsen the air quality in the plane areas. During the nighttime, NO and ozone react to produce NO2, which is the precursor of secondary aerosol that would lead to a polluted condition in the mountain areas.



AS17-A001 | Invited
Spatial-Temporal of Unusual Temperature Events

Yulizar YULIZAR#+
Universitas Pertamina, Indonesia


Changes in the temperature series might not only affect as an extreme from a single observation station but might also result in a change of 'extreme' on the multivariate scale. This change is called unusual events, where different anomalies occurred simultaneously due to the interaction of series in time and space. A statistical approach based on the outlyingness function is being used to identify the occurrence of unusual events based on the geometrical position of a point series on the multivariate set. To illustrate the methodology, the daily historical of mean temperature series from several selected observation stations in Germany were used in this study. The result showed the variability of unusual temperature events was clearly shown on temporal and spatial scales. Some events were appearing, which have never occurred before, and others were disappearing from the different time interval. A bootstrap-based methodology was used to test the statistical significance of the results.  

AS17-A002 | Invited
Performance of a Small Doppler Sensor Towards Vehicle-based Precipitation Observation

Shiho ONOMURA#+, Hikaru SAITO, Makoto NAKAYOSHI
Tokyo University of Science, Japan


With the increasing number of intensive and severe rainfalls in the Asia region, more importance is given to the precipitation observation. In addition to current observation systems such as tipping bucket gauges and meteorological radars, new methods have been explored to enhance those observation networks. One of the new ideas is vehicle-based observation utilizing wiper frequency information, but it provides only qualitative information about rain. In this paper, we applied a small Doppler sensor (IPM-165, 25╳25╳10 mm) to the precipitation observation, which is low-cost and could be easily mounted on cars. In order to investigate the best mounting orientation as well as the performance of the Doppler sensor in precipitation measurements, the sensors mounted at different orientations (four cardinal directions, vertically upward and diagonally upward) were tested at a fixed point in the summer of 2020, together with a standard laser precipitation monitor (LPM), a cup anemometer and a wind vane. The sensor’s response to rainfall was evaluated by the fluctuation components of the output voltage from the 1s moving average. In comparison with rainfall intensity measured by LPM, the sensor sufficiently reacted to a wide range of the intensity from 0 – 100 mm/h. The relation between the sensor’s signal and rainfall intensity was approximately modelled by a second order polynomial curve. However, the relation became poorer with the time probably due to distress in the severe outdoor environment so that the proper housing of the sensor is needed. An insight on the mounting orientation is that mounting the sensors to face upward was better for the sensitivity compared to horizontally. The responsiveness of the sensors facing horizontally is strongly influenced by wind directions. The sensor facing to the wind reacted most, while the one with the following wind did little.

AS17-A004
Role of Baroclinic Trough in Triggering Vertical Motion During Summertime Heavy Rainfall Events in Korea

Chanil PARK1#+, Seok-Woo SON2, Jung-Hoon KIM2
1Boston College, United States, 2Seoul National University, Korea, South


The nature of the vertical motion responsible for the summertime (June–September) heavy rainfall events (HREs) in Korea is quantitatively examined. By compositing 318 HREs in 1979–2018, it is found that the synoptic conditions of the HREs are typically characterized by a developing surface cyclone with a southwesterly low-level jet on its southeastern flank and an upper-level trough to the west of the HREs. This baroclinic environment allows for well-organized vertical motion over Korea at the equatorward side of the upper-level jet entrance. The relative importance of dynamic and diabatic forcings in driving the vertical motion is further quantified by solving the quasi-geostrophic omega equation. It turns out that the dynamic forcing, defined as Q-vector convergence, is comparable to the diabatic forcing in the developing stage of the HREs. The diabatic forcing, however, becomes more important in the mature stage as latent heating rapidly increases. The decomposition of Q-vector into the transverse and shearwise components reveals that the dynamic uplift is largely caused by the shearwise Q-vector convergence which is closely related to the developing trough in the upper-to-middle troposphere on the west of the HREs. This result indicates that the HREs in Korea are organized by the baroclinic trough coupled to moist processes, with a minor contribution of the thermally-direct secondary circulation at the entrance region of the upper-level jet.

AS17-A006 | Invited
Increasing Super-typhoons and Their Detected Predominant Assisting Seasonal Environmental Factors in the North West Pacific

Ravi Shankar PANDEY#+, Yuei-An LIOU
National Central University, Taiwan


Previous 17-year (2001-2016) data analysis clearly shows a gradually increasing pattern in the strength of typhoons in the Northwest Pacific (NWP) basin. As NWP alone accounts for 30% of the whole world’s typhoons so it is a frightening situation. This study investigates the predominant favorable seasonal environmental factors for the recent (2013-2017) all (30) most intense typhoons, also referred to as Super-Typhoons (STY). The incorporation of remote sensing imagery and wind vector plots using U and V wind component data, successfully identifies a dominant and crucial role of southwest air flow and northwest cold air mass in intensifying STYs in summer and winter seasons, respectively. Study emphasis that most winter STYs are also partly assisted by southwest air flows, and, thus, exhibit higher intensities than summer STYs. All summer STYs merely take recurvature once they finish their individual maximum intensity stage. It is observed that the Siberian-Mongolian High (SMH) originated cold air masses push the genesis positions of winter STYs more down in latitude than summer STYs, which cause not only a big genesis angle but also a big turning angle on average in winter STYs in the NWP. Locating the zones of the turning points and super-typhoon stage points of super-typhoons in the NWP is of crucial importance. It helps us understand the environmental components responsible for causing variation in the direction and strength of STYs in the NWP ocean basin. These results are critical to investigate the relationship between STYs and their season-dependent environmental factors to mitigate their risk in the region.

AS17-A007
Organization and Internal Structure of Typhoon Induced Precipitation Over Japan

Sridhara NAYAK1#+, Tetsuya TAKEMI2
1Japan Meteorological Corporation, Japan, 2Kyoto University, Japan


This study explores the temporal precipitation organization of 120 landfalling typhoons around Japan during 2006-2019. The internal structure particularly the cell sizes and spell durations of precipitations induced by these 120 typhoons are investigated from the Radar Automated Meteorological Data Acquisition System (Radar-AMeDAS) observed hourly precipitation dataset. The best track data from the Regional Specialized Meteorological Center (RSMC) Tokyo are utilized to identify the typhoon locations. We first stratified the independent precipitation cell sizes and precipitation spell durations with intensity exceeding various thresholds into different bins. Then the frequency distribution of the precipitation sizes and durations in each bin are computed. Our results indicate that the occurrence of typhoon induced heavier precipitations is higher compared to the typhoon induced lighter precipitations. The typhoon induced heavier precipitations over Japan last up to a day, while the lighter precipitations last about 12 hours. The long-lived precipitations are also noticed that last up to 2 days, but they don’t occur so frequently. We analyzed the spell durations over different regions of Japan with various radii from the typhoon center starting from 10 km to 300 km. The results also indicate that the pattern of spell durations are mostly same over all the regions within 300 km radius.

AS17-A008
Observed Synergies Between Urban Heat Islands and Heat Waves and Their Controlling Factors in Shanghai, China

Xiangyu AO1#+, Dan LI2
1Shanghai Typhoon Institute of China Meteorological Administration, China, 2Boston University, United States


There is an on-going debate as to whether the UHI intensity (UHII) is enhanced or dampened under HWs. Using a comprehensive dataset including continuous surface energy flux data for three summers (2016-2018) and automated weather station data for six summers (2013-2018) in Shanghai, China, we find synergies between UHIs and HWs when either a coastal or an inland suburban site is used as the reference site. We further find that during HWs, the increase of net radiation at the urban site is larger than that at the suburban site. More importantly, the latent heat flux is slightly reduced at the urban site but is slightly increased at the suburban site, while the increase of the sensible heat flux is larger at the urban site. This change of surface energy partitioning, together with the increased anthropogenic heat flux during HWs, exacerbates the UHII. The change of surface energy partitioning is consistent with the observed decrease of relative humidity ratio between urban and suburban areas. The UHII is stronger when the regional wind speed is reduced and under sea breeze, both of which are found to be associated with HWs in our study region. This study suggests that there are multiple factors controlling the interactions between UHIs and HWs, which may explain why synergies between UHIs and HWs are only found in certain metropolitan regions and/or under certain HW events.