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Oral Presentations of Section AS on Day 5 - Friday, August 11, 2017

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AS42 - Remote Sensing of Fires, Aerosols, Surface Pm2.5, and Aerosol Precursors
Friday, August 11, 2017 | 308 | 08:30-10:30
1.
AS42-D5-AM1-308-001 (AS42-A011)
 
The GaoFen-5 Satellite Mission for Air Quality Monitoring in China
Liangfu CHEN#+
Chinese Academy of Sciences, China
#Corresponding author: tmh1985@163.com +Presenter

The Chinese government has developed GaoFen series of satellites to observe the Earth, with GaoFen-5 for air quality monitoring specially. There are four main instruments onboard GaoFen-5, Directional Polarization Camera (DPC), Environment Monitoring Instrument (EMI), Atmospheric Infrared Ultraspectral (AIUS), and Greenhouse-gases Monitoring Instrument (GMI). DPC is similar as PARASOL, which mainly measures scattering properties of aerosol and clouds with polarization. The EMI with spectrum range in 270-790 nm can obtain information of trace gases such as NO2, SO2, and O3 as OMI. At the same time, AIUS can provide vertical profiles of trace gases such as O3, H­­2O with occultation observation. GMI measures information of greenhouse gases of CO2 and CH4 with shortwave infrared bands. The integrated observation of these instruments can provide a comprehensive insights into the air pollution in China. As all the instrument test and algorithms reached the end, the GaoFen-5 satellite is expected to be launched later in 2017.

2.
AS42-D5-AM1-308-002 (AS42-A001)
 
An Operational Method for Aerosol Optical Depth Retrieval Using High Temporal-Spatial Resolution Data of Geostationary Satellite Gaofen-4
Xingfeng CHEN1+, Zhengqiang LI1#, Weizhen HOU1, Ying ZHANG1, Shaoshuai ZHAO2
1 Chinese Academy of Sciences, China, 2 Henan Polytechnic University, China
#Corresponding author: lizq@radi.ac.cn +Presenter

Geostationary satellite is useful and important for monitoring the aerosol temporal and spatial changes, especially in China. The Chinese Gaofen-4 satellite is a new generation geostationary satellite which has both more spectral bands (6 bands: 1 Panchromatic, 4 Visible and near infrared and 1 Medium-wave infrared) and high temporal and spatial (50m) resolution. Gaofen-4 grabs images in staring and scanning observation modes. Utilizing the ultra-high temporal-spatial resolution satellite data acquired by Gaofen-4, we designed the operational method and software system to retrieve aerosol optical depth. The characteristics of Gaofen-4 observation modes and the band sensibility were investigated. We developed the retrieval algorithm of aerosol optical depth using ultra-high temporal-spatial resolution data, with a core idea of “surface and atmosphere varies differently” special for geostationary satellite. And, a cloud masking method was developed using only four visible and near infrared bands considering the NDVI and WT indexes. The AOD retrieval algorithm is being used for GOCI sensor and has been improved for Gaofen-4 data. In the improved algorithm, the earth-atmosphere signals could be decoupled automatically by the self-updating reflectance using time series data. Then, an operational software system was developed, which has the capabilities of multithreading calculation and automatic operation, which meet the demands of satellite data operational processing. A series of Gaofen-4 satellite data were processed and validated by the ground-based experimental data, which can get from AERONET and SONET. Preliminary results (R2>0.76) were obtained and indicate that the system has good reliability and stability. This remote sensing software system could monitor temporal-spatial changes of the haze pollutions in China.

3.
AS42-D5-AM1-308-003 (AS42-A009)
 
Remote Sensing Observation of Dust Storms and Thier Association with Kawasaki Disease Outbreaks
Hesham EL-ASKARY1#+, Nick LAHYE2, Eric LINSTEAD1, William SPRIGG3, Magdi YACOUB4
1 Chapman University, United States, 2 Jet Propulsion Laboratory, California Institute of Technology, United States, 3 University of Arizona, United States, 4 Imprerial College of London, United Kingdom
#Corresponding author: elaskary@chapman.edu +Presenter

Kawasaki disease (KD) is a rare vascular disease that, if left untreated, can result in irreparable cardiac damage in children. While the symptoms of KD are well-known, as are best practices for treatment, the etiology of the disease and the factors contributing to KD outbreaks remain puzzling to both medical practitioners and scientists alike. Recently, a fungus known as Candida, originating in the farmlands of China, has been blamed for outbreaks in China and Japan, with the hypothesis that it can be transported over long ranges via different wind mechanisms. This paper provides evidence to understand the transport mechanisms of dust at different geographic locations and the cause of the annual spike of KD in Japan. The particle in question is Candida that is carried along with many other dusts, particles or aerosols, of various sizes in major seasonal wind currents. The evidence is based upon particle categorization using the Moderate Resolution Imaging Spectrometer (MODIS) Aerosol Optical Depth (AOD), Fine Mode Fraction (FMF) and Ångström Exponent (AE), the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) attenuated backscatter and aerosol subtype, and the Aerosol Robotic Network’s (AERONET) derived volume concentration. We found that seasonality associated with aerosol size distribution at different geographic locations plays a role in identifying dominant abundance at each location. Knowing the typical size of the Candida fungus, and analyzing aerosol characteristics using AERONET data reveals possible particle transport association with KD events at different locations. Thus, understanding transport mechanisms and accurate identification of aerosol sources is important in order to understand possible triggers to outbreaks of KD. This work provides future opportunities to leverage machine learning, including state-of-the-art deep architectures, to build predictive models of KD outbreaks, with the ultimate goal of early forecasting and intervention within a nascent global health early-warning system.

4.
AS42-D5-AM1-308-004 (AS42-A012)
 
Estimating Regional PM2.5 Through Sophisticated Correction on Satellite AOD: An Attempt of Combining Chemical Model and In Situ Meteorological Observations
Zifeng WANG#+, Liangfu CHEN, Minghui TAO, Jinhua TAO, Li SU
Chinese Academy of Sciences, China
#Corresponding author: wangzf@radi.ac.cn +Presenter

Fine particulate matters with aerodynamic radius less than 2.5 μm (PM2.5) is one of the primary pollutants in most regions of China, which induces substantial adverse impact on public health and ecological safety. The estimation of regional PM2.5 using satellite derived aerosol optical depth (AOD) faces two major sources of uncertainty, namely the vertical distributions and hygroscopic characteristics of aerosols. This study follows a clear pathway of “physical correction on AOD” by integrating chemical model simulations and in situ observations, aiming at reduce the impact of these problems.

Firstly, the aerosol vertical profiles from models are compared with collocated in situ profiles observed by LIDAR or radiosonde. Model profiles will be adjusted based on the constraint of observed profiles as well as local weather conditions, so as to extract and accurate extinction contribution of ground-level aerosols to AOD. We use 0.25° GEOS-Chem to provide regional vertical profiles of aerosols, and after appropriate adjustment these data are used to conduct vertical correction on MODIS AOD to obtain the regional distribution of surface aerosol extinction. Secondly, this study develops an empirical method of dynamically deriving aerosol hygroscopicity over different time and space. Not relying on detailed information of aerosol chemical and microphysical properties, this method simply uses the in-situ observations of visibility (VIS), RH and PM2.5 concentrations to approximate aerosol hygroscopic growth under ambient conditions. The applicability of this method to the routine measurements from meteorological and air quality network guarantees enough spatial and temporal coverages to support the satellite estimation of PM2.5.

Preliminary attempt was conducted over Zhejiang Province in East China based on one year of dataset in 2014. Our results showed that this method effectively improves the AOD-PM2.5 correlation after implementing the vertical and hygroscopic correction, and especially can achieve a satisfactory accuracy in daily satellite estimation of PM2.5.

5.
AS42-D5-AM1-308-005 (AS42-A020)
 
Analysis of Aerosol Information Content in Simulated CAPI/TanSat Observation Over Land
Xi CHEN1#+, Jun WANG2, Yi LIU1, Xiaoguang XU2, Zhaonan CAI1, Dongxu YANG1
1 Chinese Academy of Sciences, China, 2 The University of Iowa, United States
#Corresponding author: chenxilageo@mail.iap.ac.cn +Presenter

Aerosols affect the radiative transfer in the absorption bands of carbon dioxide (CO2), thereby contributing to the uncertainties in the retrieval of CO2 from space. A Cloud and Aerosol Polarimetric Imager (CAPI) has been designed to fly on the Chinese Carbon Dioxide Observation Satellite (TanSat) and provide aerosol and cloud information to facilitate the measurements of CO2. This study aims to assess the information content about aerosol properties that can be obtained from CAPI’s observations of radiance and polarization. We simulate synthetic CAPI observations using the UNified Linearized Vector Radiative Transfer Model (UNL-VRTM), from which the degree of freedom for signal (DFS) and a posteriori error are calculated using optimal estimation theory. It is found that CAPI can provide 3 to 4.5 independent pieces of information about aerosol parameters, mainly related to aerosol total volume (or aerosol optical depth), fine mode fraction (fmfv) of aerosol volume, and imaginary part of refractive index for coarse mode aerosols. At directions around back-scattering, aerosol information content is smaller due in part to the large directional surface reflectance. In addition, due to weaker scattering of coarse aerosol, the information content of large particle is relatively less. Therefore, as fmfv decreases, DFS remains large for fine aerosol and increases for coarse aerosol. Furthermore, the degree of linear polarization (DOLP) is shown to be more sensitive to aerosol properties than reflectance, hence improves CAPI’s aerosol retrieval accuracy. The additional information content from DOLP measurements ranges from 1 to 1.8 in terms of DFS and reaches the largest in conditions of 0.2 < fmfv < 0.4 at SZA < 60o. If AOD is known as a priori (for example, from other A-Train satellites), total DFS for aerosol information content can be improved by 0.8 to 1.6 in most cases, and could exceed 2.0 for AOD < 0.2.

6.
AS42-D5-AM1-308-006 (AS42-A021)
 
A Multi-Platform System for Understanding, Monitoring and Forecasting the Impact of Aerosol Pollutants in South-East Asia
Santo SALINAS#+, Li TAN, Daniel KALBERNATTER
National University of Singapore, Singapore
#Corresponding author: crsscsv@nus.edu.sg +Presenter

In the South-EAST Asia (SEA) region, smokeemissions from biomass burning has become an ever increasing problem that affects the region's major cities and especially Singapore. Trans-boundary smoke episodes triggered by fire events are occurring more frequently and with increasing intensity e.g. 1997, 2006, 2010, 2013 and more recently 2015. These fire events are the result of small and large scale land clearance occurring specially during the region's dry season and periods of severe draught. Satellite observations suggest a strong impact of the Asian summer monsoon on the local and regional tropospheric environment. Such a impact influences surface sources of emission such as local pollution and trans-boundary emissions (biomass burning). Unfortunately, the lack of extensive and reliable measurements, in most parts of the region, makes it difficult to assess and quantify the monsoonal effect. Satellite remote sensing has the capability of delivering non-intrusive, regional wide means of understanding and studying the local and regional sources of aerosol emission. However, the extraction of aerosol physical and optical properties from remote sensing satellites as well as inferring its transport and evolution posses substantial challenges as the region host one the highest cloud fraction in the world. In this work, we will discuss the challenges that the local and regional meteorology imposes on ground and satellite remote sensing observations as well as proposing a framework to overcome these limitations. Such a framework will allow for rapid measurement response during pollution events as well as to study the different aspects of the local and regional aerosol environment. Such an arrangement is crucial andnecessary in order to establish rigorous correlations between tropospheric aerosols and local air quality indicators.

8.
AS42-D5-AM1-308-007 (AS42-A010)
 
Aerosol Microphysical Properties Retrievals from High Spectral Resolution Lidar Data
Xu LIU#+
NASA Langley Research Center, United States
#Corresponding author: xu.liu-1@nasa.gov +Presenter

An Optimal Estimation (OE) inversion method has been developed to retrieve aerosol effective size, volume concentration, and complex refractive indices using three wavelengths backscattering (3β) and two wavelengths of extinction (2α) lidar measurements. The algorithm is capable of retrieving multiple aerosol modes and can retrieve vertical profiles simultaneously using altitude resolved HSRL data. The algorithm is designed in such as way that it can include additional measurements (e.g. polarimeter or Sun photometer) for improved aerosol microphysical property retrievals. In a traditional aerosol retrieval algorithm, one solves for aerosol size distributions under various parameter space (rmin, rmax, real and imaginary refractive index) using Tikhonov (or other) regularization and then selects physically and mathematically meaningful solutions from hundreds of thousand retrievals. In an attempt to speed up the retrieval and to provide retrieval error estimates, the OE method solves for all related aerosol microphysical parameters (e.g. number concentrations, particle size distribution, real and imaginary part of refractive indices) simultaneously in a maximum-likelihood sense by fitting the observed data. Other quantities such as effective particle radius, surface area concentration, volume concentration, and single scattering albedo are also derived from the retrieved size distribution and the number concentrations. Preliminary results using both simulated data and airborne measurements from HSRL-2. Coincident airborne in-situ and surface remote sensing datasets will be used to evaluate the performance of the new OE algorithm.

AS42 - Remote Sensing of Fires, Aerosols, Surface Pm2.5, and Aerosol Precursors
Friday, August 11, 2017 | 308 | 11:00-12:30
1.
AS42-D5-AM2-308-008 (AS42-A005)
 
Improving Nocturnal Fire Detection with the VIIRS Day-Night Band
Jun WANG#+
The University of Iowa, United States
#Corresponding author: jun-wang-1@uiowa.edu +Presenter

Building on existing techniques for satellite remote sensing of fires, this paper takes advantage of the day–night band (DNB) aboard the Visible Infrared Imaging Radiometer Suite (VIIRS) to develop the Firelight Detection Algorithm (FILDA), which characterizes fire pixels based on both visible-light and infrared (IR) signatures at night. By adjusting fire pixel selection criteria to include visible-light signatures, FILDA allows for sig- nificantly improved detection of pixels with smaller and/or cooler subpixel hotspots than the operational Interface Data Processing System (IDPS) algorithm. VIIRS scenes with near-coincident Ad- vanced Spaceborne Thermal Emission and Reflection (ASTER) overpasses are examined after applying the operational VIIRS fire product algorithm and including a modified “candidate fire pixel selection” approach from FILDA that lowers the 4-μm brightness temperature (BT) threshold but includes a minimum DNB radi- ance. FILDA is shown to be effective in detecting gas flares and characterizing fire lines during large forest fires (such as the Rim Fire in California and High Park fire in Colorado). Compared with the operational VIIRS fire algorithm for the study period, FILDA shows a large increase (up to 90%) in the number of detected fire pixels that can be verified with the finer resolution ASTER data (90 m). Part (30%) of this increase is likely due to a combined use of DNB and lower 4-μm BT thresholds for fire detection in FILDA. Although further studies are needed, quantitative use of the DNB to improve fire detection could lead to reduced response times to wildfires and better estimate of fire characteristics (smoldering and flaming) at night.

2.
AS42-D5-AM2-308-009 (AS42-A004)
 
Predicting Pollutant Emissions from Agricultural Waste Burning in Guangdong Province Using Neural Network
Xu FENG+, Tzung-May FU#, Hansen CAO
Peking University, China
#Corresponding author: tmfu@pku.edu.cn +Presenter

The trace gases and aerosols emitted from agricultural waste burning have large impacts on air quality in many parts of China, including in particular the Pearl River Delta. These seasonal emissions are variable in space and time, posing a challenge for air quality forecasts. Here, we used the back-propagation neural network (BPNN) technique to predict the daily variability of agricultural waste burning. We applied hierarchical clustering and K-means clustering techniques to objectively determine spatially-coherent areas for individual BPNNs. The BPNNs were constructed and trained using a decade (2003 to 2012) of daily assimilated meteorological data from NCEP FNL and fire pixels from the Moderate Resolution Imaging Spectroradiometer (MODIS). The data from the year 2013 were used for validation. In forecast mode, we drove the BPNNs with NCEP FNL forecast to obtain daily fire pixel forecasts, which were in turn used to scale the Fire Inventory from NCAR (FINN). We compared air quality forecasts driven by our daily-variable emission inventory, as well as forecasts driven by the monthly mean FINN. We showed that our daily-variable inventory led to significant improvements in the forecasts of PM2.5 and trace gas concentrations in the Guangdong Province.

3.
AS42-D5-AM2-308-010 (AS42-A013)
 
Understanding Sources of Elemental Composition of Particulate Matter in the South China Sea During the 2011 Vasco Cruise
Miguel Ricardo HILARIO1#+, Gabrielle Frances LEUNG1, Annelle Raphayette CHUA1, Melliza CRUZ2, Maria Obiminda CAMBALIZA1,2, Jeffrey REID3, James SIMPAS2, Nofel LAGROSAS2,4, Donald BLAKE5, Sherdon Niño UY2
1 Ateneo de Manila University, Philippines, 2 Manila Observatory, Philippines, 3 Naval Research Laboratory, United States, 4 Chiba University, Japan, 5 University of California, Irvine, United States
#Corresponding author: miguel.hilario@obf.ateneo.edu +Presenter

The South China Sea is a receptor of various natural and anthropogenic aerosols. However, current understanding of their sources is limited. In September 2011, a 2-week research cruise was conducted near Palawan, Philippines. Size-segregated aerosol data was collected using a Davis Rotating-drum Uniform size-cut Monitor sampler, and analyzed for 28 selected elements. Whole air samples were also collected and analyzed for over 60 trace gases.  Positive Matrix Factorization was performed on the PM2.5 size range to determine possible sources and their contributions to the fine particulate matter mass. Additionally, size distribution plots, time series plots, PM1:PM10 ratio slope values and correlation matrix were used in interpreting factors. In the PM2.5 size range, initial results identify five sources: ferrous metal source (2.4%), biomass burning (26.1%), sea spray (36.5%), oil combustion (4.3%), and coal combustion (30.7%). Vanadium was solely apportioned to the oil combustion factor. Furthermore, 91.3% of V was found in the PM0.75 size range, suggesting anthropogenic origins. Nearly 85% of K and 62% of S were apportioned to the biomass burning factor. Spikes in the biomass burning contribution coincided with the arrival of plumes during the cruise, further suggesting the presence of biomass burning emissions in the SCS. Biomass burning tracers (ethane, benzene, CH3I) tracked the time series plot of carbon monoxide. These results coincide well with known biomass burning activity in the region. However, the high contribution of coal combustion was unexpected and our analysis showed it to be ubiquitous throughout the cruise. Selenium, a tracer of coal combustion, displayed a slight increase towards the end of the cruise, possibly due to a coal-fired power plant near Manila Bay. Understanding sources is key to characterizing the aerosol environment in the SCS and its relationship with cloud behavior and precipitation patterns in the region.

4.
AS42-D5-AM2-308-011 (AS42-A019)
 
Impact of Crop Residue Burning on Air Quality Over China Based on Satellite Data and Field Observations
Meng FAN#+, Liangfu CHEN, Shenshen LI, Mingmin ZOU, Jinhua TAO
Chinese Academy of Sciences, China
#Corresponding author: fanmeng@radi.ac.cn +Presenter

Emissions of fine aerosol particles and gaseous pollutants from biomass burning, including forest/savanna fires and crop residue burning, significantly contribute to the severe degradation of regional air quality, the change of global climate, as well as human health. As a large agricultural country, China faces large-scale burning of crop stubble in the field during the harvesting, post-harvesting and pre-harvesting periods. In China, especially in recent decades, straw burning played a noticeable role in the sudden and extreme haze episodes that combined with the primary and secondary pollutants derived from the industry pollution, engine exhausts and coal combustion. In this study, MODIS and VIIRS data were used to derive crop residue burning spots. And the spatio-temporal variation characteristics of crop residue burning over China for a long time were investigated. Because air quality data in China began to be monitored in 2012 only in important regions,such as the Jing-Jin-Ji region, the Yangtze River Delta Region, the Pearl River Delta Region and provincial capitals. Daily air quality data since 2012, including PM2.5, PM10, O3, NO2, SO2 and CO, were obtained from China's National Environmental Monitoring Center (CNEMC). The Kriging method was applied for analyzing the spatial distribution of PM2.5, PM10, O3, NO2, SO2 and CO during the period from 2012 to 2016. Finally, the daily crop residue burning and air quality data were used to analyze their spatial and temporal relationships. Our results showed that crop residue burning is close related to PM2.5 change in summer, China's middle-east and autumn-winter, China's northeast, they showed a spatial consistency during these two periods. In autumn-winter, crop residue burning can effectively induce the PM2.5 increase in China's northeast, and it is more obvious than summer crop residue burning because of the special weather condition, different crop residue and other sources of PM2.5.

6.
AS42-D5-AM2-308-012 (AS42-A026)
 
The Utilization of Satellite Observations for Improving Global Aerosol Forecasting
Sarah LU1#+, Shih-Wei WEI1, Xiaoyang ZHANG2, Shobha KONDRAGUNTA3, Sheng-Po CHEN1, Qiang ZHAO3, Jun WANG3, Partha BHATTACHARJEE3, Jeff MCQUEEN3
1 University at Albany, State University of New York, United States, 2 South Dakota State University, United States, 3 National Oceanic and Atmospheric Administration, United States
#Corresponding author: sarah.lu@noaa.gov +Presenter

Aerosol modeling, traditionally serving regional air quality and climate communities, has seen rapid development at several operational and research NWP centers in the last few years. The development of global aerosol forecasting capability allows aerosol impact on weather forecasts and climate prediction to be considered. In addition, it enables the NWP centers to provide quality atmospheric constituent products, serving the stakeholders such as health professional, policy makers, climate scientists, and solar energy plant managers.

Satellite observations have been utilized extensively to improve aerosol forecasts. This includes: (1) routine monitoring of model performance, (2) the use of near-real-time biomass burning emissions from satellites, and (3) data assimilation of satellite aerosol observations. This study compared model results with versus without using near-real-time smoke emissions and document the performance gain resulted from satellite emissions information. We then investigate the effects of aerosol data assimilation on improving the initial conditions for aerosol forecast. The model we use is NOAA global aerosol system, NEMS GFS Aerosol Component (NGAC). Real-real-time smoke emissions are blended from MODIS and multiple geostationary satellites. Satellite products we assimilated are VIIRS aerosol optical depth.

AS06 - Spatial and Temporal Variability of Aerosol in an Around Indian Subcontinent and the Associated Radiative Forcing - a Study from In-situ and Satellite Derived Data
Friday, August 11, 2017 | 308 | 14:00-15:30
1.
AS06-D5-PM1-308-001 (AS06-A011)
 
Impact of Forest Fire on Black Carbon Concentration and Tropospheric NO2 Over North Eastern Region of India
Arup BORGOHAIN#+, Nilamoni BARMAN, Shyam Sundar KUNDU, Aniket CHAKRAVORTY, Rekha BHARALI, P.L.N. RAJU
North Eastern Space Applications Centre, India
#Corresponding author: arupborgohain@gmail.com +Presenter

Forest fires are one of the principal sources of air pollution. Smoke from forest fire is a mixture of gases and fine particles from biomass burning. They can have significant impacts on local air quality, visibility and human health. Emissions from forest fires can travel large distances, affecting air quality and human health far from the source. These emissions include: particulate matter, carbon monoxide, atmospheric mercury, ozone-forming chemicals, Nitrogen Oxides (NOx) and volatile organic compounds. The impact of forest fire on air quality is investigated over the North-Eastern region of India, study domain: 20˚N-30˚N and 88˚E-98˚E. It is observed that the region has experienced more than 1 Lakh active fires in a year with a maximum in the months of March/April about 60,000 fire points. In this study active fire data with a minimum 50% confidence level from MODIS, surface mass concentration (kg/m3) of Black Carbon (BC) at 0.5˚×0.625˚ resolution from MERRA-2, tropospheric columnar NO2 from AURA-OMI at a resolution of 0.25˚, and wind vector from MERRA at 0.5˚×0.625˚ resolution has been used from 2006 to 2016. Results show that there is significant correlation between fire counts, BC concentration and tropospheric NOin the months of March and April. MODIS active fire map showed higher density of fire counts over the Indo-Myanmar bordering areas, and the Meghalaya plateau region. Similarly high BC concentration has been observed in the same month over the places except the Meghalaya plateau. This inverse spatial correlation between fire count and BC concentration over the Meghalaya plateau can be attributed to the synoptic wind patterns, which show a strong westerly wind over the Meghalaya plateau. This leads to a wash out of the BC concentration towards the Indo-Myanmar hills range making for a high concentration of BC over the Indo-Myanmar region but not over Meghalaya.

2.
AS06-D5-PM1-308-002 (AS06-A004)
 
Vertical Profiles of Aerosol Optical Properties in the Indo-Gangetic Plain and its Radiative Implications
Aditya VAISHYA#+, V. JAYACHANDRAN, Mukunda M. GOGOI, S. Suresh BABU
Vikram Sarabhai Space Centre, India
#Corresponding author: indyaaditya@gmail.com +Presenter

Vertical profiles of aerosol optical properties were measured prior to the onset of monsoon in June, 2016 as part of the Regional Aerosol Warming Experiment (RAWEX) to study the influence of aerosols on the thermal structure of the atmosphere and subsequent implications to onset of the Indian summer monsoon. Extensive measurement of vertical profiles of aerosol scattering coefficient, extinction coefficient and black carbon concentrations were carried out using an Indian Space Research Organisation (ISRO) instrumented aircraft. Three stations, Jodhpur, Varanasi, and Bhubaneswar in the Indo-Gangetic Plain (IGP) were selected for they represent the west, central and east of the IGP. At each station a minimum of 4 profiles were taken at 6 vertical levels with each level representing minimum 20 minutes of data totalling over 80 minutes.

Aerosol light extinction and scattering coefficients shows a decreasing trend with altitude. In the central IGP, due to large and heterogeneous distribution of anthropogenic aerosol sources, extinction, scattering coefficients, and BC have high values with large standard deviation. The value falls off rapidly with altitude. There is a visible and systematic shift in the size mode of particles from west to east in the IGP. The influence of source region on the size model is evident with larger mode particles dominating in the west of the IGP with dessert dust as source region and fine to very fine particles dominating the central and east of the IGP dominated by anthropogenic sources. SSA decreases as one move from west to east in the IGP. Layer heating due to absorbing aerosols at elevated layers, as evident from low SSA values, may cause radiative imbalance. This has implications to cloud formation and its properties. The radiative implications of the same are presented.

3.
AS06-D5-PM1-308-003 (AS06-A007)
 
Aircraft Measurements of Aerosol Number Size Distribution Over India: Radiative Implications of Elevated Coarse Mode Absorption During Spring
Mukunda M. GOGOI1#+, S. Suresh BABU1, Lakshmi N. B.1, Vijayakumar S. NAIR1, K. KRISHNA MOORTHY2
1 Vikram Sarabhai Space Centre, India, 2 Indian Institute of Science, India
#Corresponding author: mukunda.mg@gmail.com +Presenter

Airborne measurements of size segregated aerosol number concentrations were carried out onboard an instrumented aircraft over geographically diverse locations of the Indian mainland during two contrasting seasons (spring-2013 and winter-2012). The study revealed the vertical homogeneity of aerosols during spring due to enhanced thermal convective mixing; the strongest vertical dispersion of aerosols was noticeable in the central part of India. The fine mode aerosols contributed mostly to this stronger vertical dispersion, enhancing > 50% concentrations (in comparison to winter) in the lower free troposphere (> 2 km). Interestingly, the free tropospheric regions of Himalayan foothill and Indo-Gangetic Plains (IGP) showed an increase in the coarse mode aerosol fraction (nearly twice that of winter) during spring. In contrast to this, the measurements over west and central India showed higher coarse mode aerosol fractions in winter, despite the observed higher fine mode contribution at higher altitude in spring. The CALIPSO - derived particulate depolarization ratio over the study regions indicated that the prevalence of polluted dust at higher altitudes in winter might have contributed to higher coarse mode fraction and geometric mean diameter (Dg) over the central and western India; while the elevated dust hold significance during spring over the Himalayan Foothill and IGP. This is corroborated by the enhancement in aerosol absorption optical depth (AAOD) as well as vertical profiles of absorption coefficients, inferring that the elevated layers of aerosols during spring are coarse and absorbing over the IGP. Presence of biomass burning or dust aerosols over the free-tropospheric regions of northern India caused more than 10 Wm-2 higher absorption during spring in comparison to that during winter and led to enhanced diabatic heating of the atmosphere.

4.
AS06-D5-PM1-308-004 (AS06-A008)
 
Spatial and Temporal Variability of Aerosol Optical Depth (AOD), BC Mass Concentration and Associated Radiative Forcing Over Oceanic Domain of Tropics, Sub-Tropics and Polar Waters of Indian Ocean
Harilal MENON#+, Shrivardhan HULSWAR
Goa University, India
#Corresponding author: harilalm@gmail.com +Presenter

Spatial and temporal variability of composite aerosols have been examined over the years 2011, 2013 and 2015 in the atmospheric domain spanning from 10 o N to 55 o S. This has been carried out during the period between December and February as a part of southern ocean cruise of Ministry of Earth’s science, Government of India. Aerosol optical depths and black carbon mass concentrations (BC) have been estimated from Sunphotometer and Aethalometer measurements. Quartzite crystal microbalance has been employed to derive a spatial pattern of size segregated aerosols. Since marine atmospheric boundary layer is an important component to study aerosol radiative forcing, pisharoty sondes have been launched from pre-determined stations. All these measurements were supplemented by observations of atmospheric pressure, temperature, humidity, wind speed and direction. It is observed that spectral variability of aerosol optical depth (AOD) followed Angstrom formulae in the region north of Inter-tropical convergence zone (ITCZ), while it departed from such a spectra  in the south of it. In this region, it was observed that one of the important sources of aerosol is chlorophyll-a pigment of phytoplankton. Morever, it was also noted that BC mass concentration and the height of marine atmopsheirc boundary layer (MABL) is correlated well in the region south of ITCZ but to the north there is no such relation exists. The paper also explains the microphysical characteristics of aerosols in the study area.  On an average  the direct aerosol radiative forcing is found to be around 10 w/m2 in the region north of ITCZ, however it decreases to 2 w/m2 to south of 40 o S

5.
AS06-D5-PM1-308-005 (AS06-A003)
 
Decadal Climatological Variability of Aerosol Loading in the Upper Brahmaputra Basin and Their Radiative Properties
Tamanna SUBBA1#+, Binita PATHAK1, Mukunda M. GOGOI2, Pradip BHUYAN1
1 Dibrugarh University, India, 2 Vikram Sarabhai Space Centre, India
#Corresponding author: tamannasubbas@gmail.com +Presenter

Aerosol properties have been studied for the period 2001-2016 over eastern India combining in-situ measurements, remote sensing and radiative transfer model simulations. Featuring regional aerosol radiative forcing (ARF) characteristics over the location belonging to Eastern Himalayan foothill states assumes importance owing to its unique topography and transport pathways which mostly experiences the influence of westerly air masses. The maximum/minimum climatologically averaged aerosol optical depth (AOD) is attained during March-April-May (MAM, ~0.61±0.15)/October-November (ON, ~0.26±0.05) respectively. The positive trend of AOD, Ångström exponent (α) and turbidity coefficient (β) signifies the increase in the anthropogenic activities of the region and its surroundings resulting in an increase in the accumulation of the fine mode aerosol species. The intense biomass burning over the region initiates large vertical dispersion of aerosols and thus adds to the total atmospheric burden. The annual mean Fire Radiative Power (FRP) values over Eastern India (~30 MW) is maximum followed by that in Central India (~24 MW), South India/ West India (~19 MW) and North India (~15 MW). During MAM at the peak-time of the burning events, the FRP reaches a very high ~3000MW over the study location. Along with the increase in the aerosol burden, the visibility trend exhibits a decrease at the rate of -0.02 kmYr-1. The AOD anomaly showed a transition from the lower to higher turbidity regime during 2007. The broadband AOD (380-1025nm) showed an increase by 35% from Phase-I (2001-2007) to Phase-II (2008-2016) consequently making the top of the atmosphere forcing more negative from -7.4 Wm-2 to -10 Wm-2respectively. The longwave ARF (ARFLW) estimated over the location showed different characteristics unlike that of the deserts and oceanic aerosol environment. The shortwave ARF (ARFSW) is faintly offset by the ARFLW i.e by ~2%-4% of the ARFSW at the surface.

6.
AS06-D3-PM1-P-007 (AS06-A006)
 
Forenoon and Afternoon Aerosol Radiative Forcing During Premonsoon-2016 at Varanasi
Manoj K. SRIVASTAVA1#+, Rajeev SINGH1, Bharat Ji MEHROTRA1, Pravash TIWARI1, Sahil SHARMA1, Anila H. BHENGRA1, N. P. SINGH1, Abhay K. SINGH1, Suresh TIWARI2, Atul K. SRIVASTAVA2
1 Banaras Hindu University, India, 2 Indian Institute of Tropical Meteorology, India
#Corresponding author: mksriv@gmail.com +Presenter

Although anthropogenic aerosols are one of the major governing factors for Earth’s climate, and they play a very important role in modifying the regional heat budget, yet it is one of the uncertain aspects of atmospheric science research. The radiative forcing of aerosols is an important input for global climate models. The present study analyzes the optical properties of aerosols as obtained by Multi Wavelength Solar Radiometer (MWR) for pre-monsoon season of 2016 at Varanasi (25.3 0N, 83.0 0E, 176 m asl), India. The location is a representative Central Indo-Gangetic Plains (IGP) station in ISRO-ARFI Network.

Using the MWR data, optical properties of aerosols were computed with the help of OPAC model (Version 4.0) for forenoon and afternoon sessions, separately, for each clear sky days. The OPAC model is iterated such that the generated spectral aerosol optical depth (AOD) falls within 5% of the observed spectral AOD. OPAC derived optical properties is then used for aerosol radiative forcing (ARF) estimation by SBDART model.

Preliminary results show that averaged pre-monsoon ARF for forenoon session at TOA was 3.2 ± 11.3 Wm-2, while at the surface it was -75.2 ± 17.6 Wm-2, resulting to the net atmospheric forcing of 78.4 ± 16.7 Wm-2. At the same time, the averaged seasonal pre-monsoon ARF for the afternoon session at the TOA was 4.5 ± 5.0 Wm-2, while at the surface, it was -68.1 ± 15.5 Wm-2 resulting to net atmospheric forcing of 72.6 ± 20.5 Wm-2. Computed heating rate for forenoon is found to be as 2.20 ± 0.5 K/day, which was lesser (2.04 ± 0.6 K/day) during afternoon. Results suggest significant differences in aerosol optical behaviour during forenoon and afternoon.

AS17 - Heavy Rainfall Monitoring and Associated QPE/QPF in the Complex Terrain Area
Friday, August 11, 2017 | 332 | 08:30-10:30
1.
AS17-D5-AM1-332-001 (AS17-A015)
 
An Overview of Radar QPE at NCAR
Wenchau LEE#+
National Center for Atmospheric Research, United States
#Corresponding author: wenchau@ucar.edu +Presenter

This talk presents an overview of the radar QPE activities at NCAR. Several radar QPE algorithms have been developed based on the NCAR S-Pol dual-polarization radar and are available for the community to use. These algorithms will be incorporated into the Lidar Radar Open Software Environment (LROSE) framework to encourage joint algorithm development efforts from the community.

2.
AS17-D5-AM1-332-002 (AS17-A007)
 
Improving C-Band Polarimetric Radar Rainfall Estimation for Summer Precipitation in Eastern China
Kun ZHAO1#+, Gang CHEN1, Guifu ZHANG2
1 Nanjing University, China, 2 Oklahoma University, United States
#Corresponding author: zhaokun@nju.edu.cn +Presenter

In this study, the capability of using a C-band polarimetric Doppler radar and a two-dimensional video disdrometer (2DVD) to estimate monsoon-influenced summer rainfall during the Observation, Prediction and Analysis of Severe Convection of China (OPACC) field campaign in 2014 and 2015 in Eastern China is investigated. Three different rainfall estimators,RZh, RZh,Zdr and RKDP, are derived from two-year 2DVD observations of summer precipitation systems. The radar estimated rainfall is compared to gauge observations from 8 rainfall episodes. Results show that the two polarimetric estimators, RZh,Zdr and RKDP, perform better than the traditional Z-R relation RZh. The KDP-based estimator RKDP produces the best rainfall accumulations. The radar rainfall estimators perform differently across the three organized convective systems (Meiyu rainband, typhoon rainband, and squall line), which can be attributed to the high variability of drop size distribution (DSD) related to the precipitation microphysics in different types of rain. Based on the statistical QPE error in the ZH-ZDR space, a new composite rainfall estimator by combining RZh, RZh,Zdr and RKDP is constructed and proven to outperform any single rainfall estimator.

3.
AS17-D5-AM1-332-003 (AS17-A010)
 
A Study of High Resolution TWRF Model Tropical Cyclone Rainfall Prediction Over High Terrain Area
Tien-Chiang YEH1#+, Der Song CHEN1, Ling-Feng HSIAO2
1 Central Weather Bureau, Taiwan, 2 Taiwan Typhoon Flood Research Institue, Taiwan
#Corresponding author: yeh@cwb.gov.tw +Presenter

With high terrain, the effect of Taiwan on the track and rainfall distribution of tropical cyclones is a very interesting issue for the academic study. Understand the capability of the model prediction on tropical cyclone track and rainfall distribution in such a complex environment is a very important issue for local disaster mitigation operation.

Taiwan’s Central Weather Bureau (CWB) has developed and implemented a version of the Advanced Research Weather Research and Forecasting Model (ARW WRF), named TWRF (Typhoon WRF), for operational tropical cyclones forecasting. The averaged 24/48/72 hours cyclone track forecast errors of TWRF are 91/147/223, 84/133/197, and 74/125/211 km in last three years (2014, 2015, and 2016), respectively. The model configuration is in triple nested at grid intervals of 45/15/5 km before 2016, and is in double nested at grid intervals of 15/3 km in year 2016.

The preliminary results show increasing the TWRF model resolution improving the tropical cyclone track prediction. In this study, cases of the TWRF tropical cyclone rainfall prediction over Taiwan are carefully examined. Results of different resolution TWRF predictions are compared. The detail will be presented in the conference. Besides, a higher resolution in grid intervals at 1 km is currently under developed. We expect to be able to show some results of the rainfall simulation in 1 km TWRF when a tropical cyclone encounters Taiwan.

4.
AS17-D5-AM1-332-004 (AS17-A013)
 
Comparison Between DSD Parameters Using a Radar and Disdrometer by Rainfall Types in Central Part of Korea
Jui Le LOH1+, Dong-In LEE1#, Cheol-Hwan YOU2, Ji-Hyeon KIM3
1 Pukyong National University, South Korea, 2 Dong-A University, South Korea, 3 Korea Meteorological Administration, South Korea
#Corresponding author: leedi@pknu.ac.kr +Presenter

To estimate accurate precipitation data, information of weather radar and raindrop size distribution are very important. In this study, the S-band polarimetric radar data from the Yongin sites (37.21 °N, 127.29 °E), operated by Weather Radar Center of KMA were used. The drop size distribution using Parsivel disdrometer from Jin Cheon sites (36.87 °N, 127.45 °E), which located 29 km away from radar are analyzed and compared with the radar retrievals in a statistical and functional approach. The rainfall system was identified in three types (stratiform, convective and unclassified rain) at various times of day from June 2015 to July 2016. There are two methods of approach to the rainfall classification; the first is retrievals from polarimetric radar, using Nw (normalized intercept parameter of a gamma DSD) and D0(medium volume diameter) from Zdr (differential reflectivity) and the second is calculated from disdrometer. We compared the different classification algorithms logNw-D0, logN0-R (rain rate), Λ-logN0, and Λ-R to find out the adequate separation of the rainfall types in the central part of South Korea. New rainfall classifications were derived from the Parsivel and Yongin data after compared with existing classification methods based on climatological rainfall data. The classification using logNw-D0 domain was performed well when compared with southern part of Korea from You et al. (2016). However, the other relations between logN0-R, Λ-logN0, and Λ-R domain were unable to classify the precipitation types well in this study region. Nevertheless, if the slope and/or intercept values of Tokay and Short (1996), Caracciolo et al. (2008), Bringi et al. (2009), and You et al. (2016) were changed, the classification methods by logN0-R, and Λ-R domain were reasonable. The new relationship between logNw-D0 , logN0-R, and Λ-R were obtained for the rainfall types at the central part of South Korea.

Acknowledgements

This research was funded by the Korea Meteorological Industry Promotion Agency under Grant KMIPA 2015-1050 and the BK21 plus Project of the Graduate School of Earth Environmental Hazard System. 

5.
AS17-D5-AM1-332-005 (AS17-A014)
 
Comparison of Quantitative Precipitation Estimation from S- and C-Band Dual-Polarimetric Radars Over Norther Taiwan
Wei-Yu CHANG1#+, Ju-Yu CHEN2, Tai-Chi CHEN WANG2
1 Chinese Culture University, Taiwan, 2 National Central University, Taiwan
#Corresponding author: hammon.chang@gmail.com +Presenter

The quantitative precipitation estimation (QPE) from S- and C-band dual-polarimetric radars have different advantages and disadvantages. This study investigates the performance of the RCWF(S-band) and the NCU-CPol (C-band) dual-polarimetric radar QPEs over northern Taiwan. Four different QPE relationships of each rain types, namely 𝑅 − 𝑍, 𝑅 − 𝐾𝐷𝑃, 𝑅 − (𝑍, 𝑍𝐷𝑅 ) and 𝑅 − (𝐾𝐷𝑃, 𝑍𝐷𝑅 ), are obtained from over-six-year NCU 2D-Video disdrometer data and applied to nine events observed by both RCWF and NCU C-Pol from March of 2014 to August of 2015. The performances of radar-based QPE are investigated by comparing with 96 rain gauges. Without considering radar measurement error, in the rain-type coefficients test suggests that most of algorithms improve after applied into the corresponding coefficients with respect to general coefficients. The 𝑅 − (𝑍, 𝑍𝐷𝑅 ) algorithm has the most significant improvement. In the radar data quality control process, the wet radome effect correction of 𝑍 has a positive impact on RCWF as well as NCU C-Pol radar. Overall, 𝐾𝐷𝑃-based relationships which combine with 𝑅 − 𝑍 are the most accurate. In the comparable sampling frequency test, NCU C-Pol radar shows the advantage of 𝐾𝐷𝑃 parameter for QPE at shorter wavelength with lower values of relative root mean square error and higher correlation coefficient.  In summary, the result suggests that when two radars’ data are included whenever available, the QPE performance can be further improved.

6.
AS17-D5-AM1-332-006 (AS17-A001)
 
Developing Himawari-8 Near Realtime System at NSMC/CMA
Min MIN#+
China Meteorological Administration, China
#Corresponding author: minmin@cma.gov.cn +Presenter

Himawari-8 (H8), the next-generation GEO satellite operated by the Japan Meteorological Agency (JMA), was successfully launched on 7 October 2014. Its installed systems include a 16-band AHI with spatial resolution from 0.5 km (visible band at 0.64 μm) to 2.0 km (infrared band) and full-disk observation frequency of 10 minutes. The AHI near real-time (NRT) observation data were released freely by JMA on 7 July 2015. For a better application of H8 data, FengYun 4 (FY-4) satellite Algorithm Working Group (AWG) have used the FengYun Geostationary (GEO) algorithm testbed for imager (FYGAT-I) they develop as a kernel module to develop a Near Realtime (NRT) Processing System for Himawari-8 at National Satellite Meteorological Center (NSMC), CMA. Currently, about 30 Level-2 science products were generated by this NRT system for providing a better service to CMA forecasters and others. Based on FengYun algorithm testbed for imager (FYGAT), we In order to better develop and validation science algorithms for various operational products from China new generation geostationary meteorological satellite (FengYun-4, FY-4) to be launched in 2016 time frame, two algorithm testbeds are developed by the researchers at National Satellite Meteorological Center (NSMC) for FY-4 imager and sounder, respectively. Both algorithm testbeds are programmed in FORTRAN and C languages for Linux or UNIX system, which are successfully tested on IBM/Dell system. Some important science products have been processed with FY-4 algorithms using proxy satellite data from instruments such as Spinning Enhanced Visible Infra-Red Imager (SEVIRI). The sensor specifications (imager) of the first satellite (FY-4A) of FY-4 series, functional structures of the algorithm testbed, and initial results generated by the testbed using proxy satellite data are introduced in this paper. Testbed for imager is also able to be a prototype for operational Data Processing System (DPS) at NSMC. It is our hope that the robust and flexible algorithm testbeds will play an important role in the utilization of FY-4 satellite data.

7.
AS17-D5-AM1-332-007 (AS17-A004)
 
Evaluation of Retrieved Cloud Microphysical Properties Between Himawari-8 and MODIS Observations
Chi-Hao CHIU#+, Chian-Yi LIU
National Central University, Taiwan
#Corresponding author: humor1993@yahoo.com.tw +Presenter

In October 2014, Japan launched Himawari-8 which is the most advanced geostationary orbit satellite in the world. Advanced Himawari Imager (AHI) that provides high quality 16-channels reflectance/radiance data at every 10 minutes temporal resolution is a sensor on-board Himawari-8. Therefore, we can retrieve the cloud microphysical parameters of high temporal and spatial resolution by AHI.

On the other hand, the South China Sea (SCS) is at the west of Pacific warm pool where has not only strong convections but also the features of multiple scales of weather and climate, for instance, summer monsoon, Mei-yu, southwesterly with Typhoons, and Madden-Julian Oscillation (MJO).

The research focuses on SCS and deeply investigates the convections system of summer monsoon onset in May 2016. We retrieve microphysical parameters by AHI and evaluate the results by the observations of Moderate-resolution Imaging Spectroradiometer (MODIS) with NASA EOS A-Train Aqua. It can help us verify and assess the quality of AHI retrievable cloud parameters in this region. In addition to passive observations, we also evaluate the cloud property by active observations, such as CloudSat and CALIPSO. By these cloud microphysical parameters, we can further analyze the structure of clouds of diurnal variability and its lifecycle.

Keyword: Himawari-8, cloud microphysics parameters, convection system

8.
AS17-D5-AM1-332-008 (AS17-A002)
 
On the Assimilation of GNSS-PWV Measurements in Heavy to Torrential Rain Events in Davao City, Philippines
Kristine Mae CARNICER1,2#+, Rui FERNANDES3, Edgar VALLAR1, Maria Cecilia GALVEZ1
1 De La Salle University, Philippines, 2 Ateneo de Davao University, Philippines, 3 University of Beira Interior, Portugal
#Corresponding author: kristine_carnicer@dlsu.edu.ph +Presenter

Precipitable water vapor (PWV) estimates derived from the datasets of a single standalone GNSS receiver was conducted in Davao City, Philippines (7o4’N, 125o36’E) for the years 2013 to 2016. The primary goal of the study is to monitor the variability of the GNSS-PWV estimates during heavy to torrential rain events. Several papers have made case studies on precipitation and atmospheric water vapor and most studies have supported the existence of the positive correlation between PWV and rain. These studies implied that a better analysis of the distribution of water vapor is a key factor to better understand the initiation of precipitation and provide more accurate forecasts of such events.

In the present study, time series plots were made to provide a better picture of the variability of PWV for each rain event. It can be observed that while moderate rain follows small variations in PWV, heavy to torrential rains usually follows a peak in PWV. A time lag of approximately 2-8 hours is observed between the two peaks. Intense to torrential rains would always be followed by a decrease of about 5-10 mm in PWV. In addition, a build-up of PWV is observed prior to intense to torrential rain. However, the maximum PWV value that precedes each rain event varies depending on the season and no cut-off value of PWV had been noted that predicts the occurrence of heavy to torrential rain events.

AS16 - Anthropogenic and Aeolian Aerosols
Friday, August 11, 2017 | 332 | 11:00-12:30
2.
AS16-D5-AM2-332-002 (AS16-A021)
 
Source-Receptor Relationship of PM2.5 Over East Asia and its Validation Using Chemical Measurements and Model Intercomparison
Mizuo KAJINO1#+, Keiichi SATO2, Cheol-Hee KIM3, Jong Jae LEE3, Akinori TAKAMI4, Hiromasa UEDA5
1 Japan Meteorological Agency, Japan, 2 Asia Center for Air Pollution Research, Japan, 3 Pusan National University, South Korea, 4 National Institute for Environmental Studies, Japan, 5 Kyoto University, Japan
#Corresponding author: kajino@mri-jma.go.jp +Presenter

The source-receptor relationship (SRR) of PM2.5 over East Asia for the year 2013 has been studied by using offline coupled meteorology – chemical transport model NHM-Chem (Kajino et al., 2015) under the framework of the Joint Research on Long-range Transboundary Air Pollutants in Northeast Asia (LTP project). Eight source-receptor regions was considered: Northwest China (NWC), Northeast China (NEC), North China (NC), South and Southwest China (SSWC), East China (EC), North Korea (NKR), South Korea (SK), and Japan (JP). In winter, spring, and autumn, 60-90% of PM2.5 concentration in the regions of China was originated to the same region. The rest was originated to the other regions but inside China. 30-40% and 20% of PM2.5 in Korea and Japan were domestic origin and the majority of the rest was originated to NEC and NC. In order to improve the values of SRR, the simulated chemical components were scaled according to the observed v.s. simulated chemical components ratios and the SRR were recalculated. The modified SRR has not been drastically different from the original one, which showed the SRR were not very sensitive to discrepancy in the simulated and observed chemical components of PM2.5.

3.
AS16-D5-AM2-332-003 (AS16-A004)
 
Spatiotemporal Variation and Source Apportionment of PM2.5 for Two Typical Episodes in Central Taiwan
Chung-Shin YUAN#+, Huazhen SHEN, Yubo JIANG, Zongmou YANG, Chung-Min HUNG
National Sun Yat-sen University, Taiwan
#Corresponding author: ycsngi@mail.nsysu.edu.tw +Presenter

Ambient air quality has become worse recently in the Central Air Quality Zone (CAQZ), particularly in Changhua County, in Taiwan. Both local emissions and cross-boundary transport could deteriorate ambient air quality, impair atmospheric visibility, and threaten human heath. Thus, this study aims to investigate the spatiotemporal variation and chemical characteristics of PM2.5, and apportion potential sources for two typical episodes on March 29th-31st (Episode I) and November 14th-18th (Episode Ⅱ) in 2016, representing PM2.5 concentrations in spring and fall, respectively. During the episodes, PM2.5 was simultaneously sampled in three National Ambient Air Quality Monitoring Stations (NAAQMS) located in the northwest, northeast, and southwest of Changhua County. After sampling, quartz fiber filters were conditioned, weighted, and analyzed for their water-soluble ions (WSIs), metallic elements, and carbonaceous contents. Receptor modelling and backward trajectories based on wind fields resolved by meteorological data obtained from NAAQMS. The results showed that the daily average PM2.5concentrations exceeded national PM2.5 standard of 35 μg/m3, ranging from 40 to 81 μg/m3, during the Episodes. Additionally, WSIs and metallic contents accounted for 42-63% and 12-24% of PM2.5, respectively. Carbonaceous content accounted for 13-20% of PM2.5 with OC/EC ratios over 2.2. .During the Episode I, PM2.5 was mainly resulted from poor air dispersion due to strong atmospheric stability in CAQZ. The sources of PM2.5 were secondary sulfate and nitrate, while industrial emissions and other sources such as fugitive dusts, vehicular exhausts and sea salts contributed the second sources of PM2.5. During the Episode Ⅱ, high PM2.5 was mainly caused by cross-boundary transport from upwind sources in central Taiwan. Major PM2.5 sources were secondary nitrate, vehicular exhausts, and secondary sulfate. Particularly, nitrate in PM2.5 increased significantly, resulting from the rise of upwind vehicular exhausts contributed from two major highway junctions located at the northern boundary of Changhua County.

4.
AS16-D5-AM2-332-004 (AS16-A016)
 
The Changing Aeolian Dust Emissions Over South Asia Inferred from Multiple Ground and Satellite Measurements
V. VINOJ1#+, Satyendra Kumar PANDEY1, Kiranmayi LANDU1, Suresh Babu S.2
1 Indian Institute of Technology Bhubaneswar, India, 2 Vikram Sarabhai Space Centre, India
#Corresponding author: vinoj@iitbbs.ac.in +Presenter

Using multiple ground, multi-satellite, model and reanalysis datasets, we investigated the change in dust over the South Asian region. For the first time, we conclusively show that dust emissions have decreased during pre-monsoon season by about 10 to 20% since year 2000. The largest reductions were observed over the Thar Desert. Our analysis further revealed that the increasing rainfall and slowing circulation and hence winds over the source regions were the principle cause. In addition, the increasing rainfall also increased the scavenging efficiency significantly. As a consequence dust emission, atmospheric concentration and long range transport all decreased during this period. Such changes may have far reaching effect on aerosol radiative forcing, decrease in early monsoon rainfall over the subcontinent and possibly changes to air quality.     

5.
AS16-D5-AM2-332-005 (AS16-A006)
 
Simulation of the Dust Aerosol and its Climatic Effect Over East Asia Using WRF-Chem Model
Siyu CHEN+, Jianping HUANG#
Lanzhou University, China
#Corresponding author: jhuang@lzu.edu.cn +Presenter

The Weather Research and Forecasting model with Chemistry (WRF-Chem) is used to investigate the seasonal and inter-annual variations of mineral dust over East Asia during 2007-2011, with a focus on the dust mass balance and its direct radiative forcing and climatic impact. A variety of in-situ measurements and satellite observations have been used to evaluate the simulation results. Generally, WRF-Chem reasonably reproduces not only the column variability but also the vertical profile and size distribution of mineral dust over and near the dust source regions. In addition, the dust lifecycle and processes that control the seasonal and spatial variations of dust mass balance are investigated in seven sub-regions. Dust direct radiative forcing in a surface cooling of up to -14 and -10 W m-2, atmospheric warming of up to 9 and 2 W m-2, and TOA cooling of -5 and -8 W m-2, respectively. The ability of WRF-Chem to capture the measured features of dust optical and radiative properties and dust mass balance over East Asian provides confidence for future investigation of East Asia dust impact on regional or global climate. Over the Tibetan Plateau, dust modifies the atmospheric heating profiles and cloud properties, leading to a decrease of snowfall and hence snow coverage on the ground. These results are from a reduction of surface albedo and increased surface temperature, further accelerating snowmelt. This impact is smallest in summer, when the snow coverage is relative low. Over the East China-Korea-Japan regions, dust modifies the atmospheric heating profiles and cloud properties. Dust induces significant changes in the magnitudes and diurnal variations of surface temperature. Cloud liquid water content is also significantly impacted, as reflected in changes of cloud forcing at the top of the atmosphere (TOA) with a maximum in summer. The dust impacts on spatial distribution of precipitation and wind circulation are also investigated, showing distinct seasonality of dust impact on the regional climate over East Asia.

6.
AS16-D5-AM2-332-006 (AS16-A011)
 
Dust Activity and its Effects on Meteorological Fields Over East Asia
Lin SU#+
Hong Kong University of Science and Technology, Hong Kong SAR
#Corresponding author: lsu@connect.ust.hk +Presenter

The dust activity over East Asia during the spring of 2012 and its direct and semi-direct effects over this region were investigated by a numerical method. The results show that the massive dust aerosol produced by dust storms covered almost all of northern China and was transported to the middle of the Pacific Ocean or even further by mid-latitude westerlies. In general, coarse dust particles tend to settle near the source region whereas finer particles are transported to areas further downstream more efficiently. The proportion of coarse particles in the dust aerosol drops quickly due to their larger gravitational deposition velocity. Generally, the dust aerosol directly causes a warming effect in the atmosphere and a cooling effect at the top and at the bottom of the atmosphere over East Asia. However, the direct radiative effect of the dust aerosol is not significant to the total radiation budget. By contrast, with more cloud condensation nuclei in the atmosphere served by dust aerosol, more cloud droplets are formed with smaller size over the areas with abundant water vapor and higher proportion of fine particles, leading to a significant cloud radiative effect, which is one order stronger than the direct radiative effect induced by dust aerosol.

AS16 - Anthropogenic and Aeolian Aerosols
Friday, August 11, 2017 | 332 | 14:00-15:30
1.
AS16-D5-PM1-332-007 (AS16-A022)
 
To Improve the Flux Estimation of Atmospheric Organic Nitrogen by Using Different Molecular Weight Composition Mode
Hung-Yu CHEN#+, Yi-Cian SHIH
National Taiwan Ocean University, Taiwan
#Corresponding author: hychen@ntou.edu.tw +Presenter

Atmospheric organic nitrogen (ON) is critical in the biogeochemical cycle of nitrogen species and an important atmospheric component that contributes significantly to total nitrogen (TN) in dry and wet atmospheric depositions. However, knowledge of the actual composition and deposition flux of ON remains limited. In the previous studies, the flux estimation for ON of wet deposition or dry deposition is based on the product of ON concentration and rainfall or deposition velocity, respectively.  Without considering the biological utilization degree for different molecular weight ON, this may cause the misunderstanding of atmospheric nitrogen input on marine new production. To understand the error degree between considering and without considering the composition of ON, we employed ultrafiltration to separate ON into low-molecular weight (LMW; <1000 kDa) and high molecular weight (HMW; >1000 kDa) ON. In this study, we collected 53 rain water samples (including 10 typhoon events) and 11 sets of size-fractionated atmospheric particles (six-stage size fractionator), by using a wet deposition collector and a high-volume air sampling system, respectively. Samples were collected from January to December 2014 at a coastal city (Keelung) on the southern East China Sea, and analyzed for dissolved and water-soluble nitrogen in wet and dry depositions, respectively. The results indicate that HMW/LMW contributed 73%/23% and 70%/30% in wet depositions and dry depositions, respectively, to the total ON concentration (35.0 mM for wet and 88.7 nmol m-3 for dry).  To estimate the carbon flux transmitted through the air, C:N is usually assumed to be 6.6. This ratio may be suitable for LMW ON, but for HMW ON the ratio is about 21. The carbon fluxes caused by atmospheric ON were 120 mmol-C m-2 yr-1 and 200 mmol-C m-2 yr-1 for overall ON and different molecular weight composition model, respectively. Therefore, the previous flux estimation for ON may have been underestimated for about 40%.

2.
AS16-D5-PM1-332-008 (AS16-A003)
 
Emissions of Polybrominated Diphenyl Ethers During the Start-up Incineration Procedure by the Multi-Fuel- Combustion of Diesel and Waste
Sheng-Lun LIN1#+, Farran REDFERN2, Lin-Chi WANG1, Jhong-Lin WU2
1 Cheng Shiu University, Taiwan, 2 National Cheng Kung University, Taiwan
#Corresponding author: cbmsgml@gmail.com +Presenter

This study focuses on the effect of using waste cooking oil (WCO) as an alternative of diesel on PBDE emissions during the start-up procedure of an industrial waste incinerator (IWI). The multi-fuel-combustions were designed with 0, 40, and 60% WCO injection (D100, W40D60, and W60D40). The polybrominated diphenyl ethers (PBDEs) were sampled from the flue gas during 4 temperature stages of the combustion chamber: 200°C, 200–450°C, 580–700°C, and >850°C). The highest PBDE level was found in the 1st stage and sharply decreased in the 2nd, when the reduction of total PBDE was a competitive result between residue releasing and thermal decomposition. The WCO were found to slightly increased the PBDE emissions during the 3rd and 4th stages, which provided the suitable temperature for PBDE formation (600–800°C), which could be enhanced by the higher viscosity of WCO injection spray. The accumulated PBDE emissions during the start-up procedure were 1,099, 1,253, and 1,207 µg by using D100, W40D60, and W60D40, respectively. Additionally, the annual PBDE emissions contributed by start-up procedures increased up to 4.60%, 5.47%, and 5.20% by three fuel combinations, respectively, if the IWI restarted once per month, and became a noticeable issue. Therefore, avoiding unnecessary start-ups was an essential criterion for IWI operation. Fortunately, the small increases (<1%) of PBDE emissions by altering 40% and 60% diesel with WCO provided a useful information for WCO treatment.

4.
AS16-D5-PM1-332-009 (AS16-A018)
 
Influences of Aeolian Dusts and Anthropogenic Particles on Ambient Particulate Air Quality in Southern Taiwan During Rainy Season - Effect of Typhoon Outflows
Chung-Shin YUAN#+, Chun-Chung LU, Tsung-Chang LI, Huazhen SHEN
National Sun Yat-sen University, Taiwan
#Corresponding author: ycsngi@mail.nsysu.edu.tw +Presenter

Aeolian dusts emitted from the bare lands of the Kaoping River in southern Taiwan exhibited distinct characteristics with specific weather conditions during the typhoon seasons (May–September), which are emerging disasters and could deteriorate local air quality severely. To investigate the influence of aerolian dust episode (ADE) on air quality, four sampling sites located along the Kaoping River were established to collect PM10 with high-volume samplers in a typical ADE and on regular days in 2012, respectively. The chemical contents including a total of 13 metallic elements, 9 water-soluble ionic species, and 2 carbonaceous species were analysed for PM10. Receptor modelling was further employed to apportion possible sources of aeolian dusts. The results showed that hourly average PM10 concentrations increased drastically from noon to evening, and maximum PM10 concentration levels reached within 3–4 hours. Sea-salt particles (SSs) in PM10 accounted for 3.56%-5.17% on regular days and 11.66%-16.47% during the ADE. Cl- deficit percentages during the ADE (6.33%-14.12%) were much lower than those on regular days (29.49%-40.38%), indicating acidic particles mainly produced by chemical reactions of acidic aerosols with aeolian dusts and SSs. The CMB receptor modeling results showed that aeolian dusts and sea-salts were major contributors of atmospheric particles during the ADE. The contributions of aeolian dusts emitted from the bare lands to PM10 concentration were in the range of 11.5%-33.1% along the Kaoping River during the ADE as well as 7.2%-23.0% after the ADE, indicating that a small amount of finer aeolian dusts emitted from the bare lands of the riverbed were still suspended in the ambient air after the ADE.

5.
AS16-D5-PM1-332-010 (AS16-A015)
 
Evaluations and Modification of Emissions Using 3D-Var Data Assimilation Technique Over Northeast Asia
Hyun-Young JO+, Hyo-Jung LEE, Yu-Jin JO, Cheol-Hee KIM#
Pusan National University, South Korea
#Corresponding author: chkim2@pusan.ac.kr +Presenter

It is highly important to characterize and to verify the emissions over Northeast Asia, especially over eastern Chinese region because Korea Peninsula has been influenced by air pollutants transported in long-range distances from upstream regions, especially from eastern China. In an effort to quantify the emissions, WRF-Chem modeling system using the updated emission inventory has been used to evaluate the impact of emission uncertainties based on the measurements in and around Korean Peninsula. We first analyzed the spatial and temporal variations and evaluated against measurements, and then employed Gridpoint Statistical Interpolation (GSI) for assimilating surface and satellite measurement with the WRF-Chem model to assess the emissions by the analysis of the differences between with and without data assimilation process. The GSI technique is a 3D-VAR assimilation tool by which an analysis is obtained by minimization of a cost function and calculating background error covariance statistics. Here measurements include in-situ measurements obtained from the regional and sub-regional atmospheric background stations in China and South Korea, Satellite column concentrations, aircraft data, and other optical properties. We also tried to further modify the emission using the GSI technique. The result shows that the simulated spatial distribution is found to be similar in comparison with observation, but simulations were overall underestimated and sometimes peak values were not captured in some region. The results have been analyzed how data assimilation technique improve the prediction capabilities of particle concentrations in and around Korean Peninsula, and also discussed are the results of how GSI data assimilation process will contribute to improve the prediction performance as well as emission modifications in and around South Korea

*This study is supported by National Institute of Environmental Research(NIER), Korea

6.
AS16-D5-PM1-332-011 (AS16-A013)
 
Study on the Chemical Characteristics of Aerosols Associated with Long-Range Transport Over East Asia Using WRF-Chem Model
Yu-Jin JO+, Hyo-Jung LEE, Hyun-Young JO, Cheol-Hee KIM#
Pusan National University, South Korea
#Corresponding author: chkim2@pusan.ac.kr +Presenter

This study aimed to evaluate the simulation of the chemical components of aerosols by employing the results of chemical transport model WRF-Chem, and to compare characteristics of chemical compositions according to the different source regions. It has been well recognized that atmospheric aerosol particles originate from a wide variety of natural and anthropogenic sources. Due to the various sources and transformation process, aerosols are generally composed of very complex and variable chemical components. The simulated results were compared with observed ones obtained at intensive air quality monitoring site in Bulgwang-dong(urban) one of the supersites in Seoul, and Baengyeong-do national background site. Baengyeong-do is one pof the representative background sites in South Korea to identify effects of the air pollutants flowing into the western part of Seoul from East China.

We classified case days into Long-Range Transport(LRT) and Local Emission Dominant(LED) cases, and chemical and meteorological characteristics have been explored for the classified two cases. There were three airflow patterns: LRT-natural source, LRT-anthropogenic source and LED. Each pattern showed the different typical chemical composition and especially ratio of SIA was high in LRT-anthropogenic and LED case. And even though WRF-Chem model underestimated the PM10 and PM2.5 concentrations in comparison with the observed ones, the characteristic of chemical composition was found to be similar to observation. Because chemical composition of aerosol depends on source region and meteorological condition, the results of our study has been also discussed for the potential use of the indicator of long-range transport process over East Asia.

*This study is supported by National Research foundation (NRF-2015R1D1A1A01060088) and National Institute of Environmental Research, Korea

AS36 - Extreme Weather Resiliency: Prediction and Response Strategies
Friday, August 11, 2017 | 333 | 08:30-10:30
1.
AS36-D5-AM1-333-007 (AS36-A018)
 
New Development and Prospective of NTU Microphysics Scheme for Simulating Extreme Precipitation
Jen-Ping CHEN#+, Tzu-Chin TSAI
National Taiwan University, Taiwan
#Corresponding author: jpchen@as.ntu.edu.tw +Presenter

The role of ice microphysics on deep convections has been evaluated extensively in earlier modeling studies. Yet, many important microphysical properties of ice-phase hydrometeors such as crystal shape, apparent density, and fall speed are still crudely treated in current cloud microphysics schemes. A multi-moment four-category-ice (pristine ice, aggregate, graupel, and hail) bulk microphysics scheme developed by the National Taiwan University (hereafter called the NTU scheme) has been implemented into the Weather Research and Forecasting (WRF) model version 3.5.1 to improve the microphysical representations. The NTU scheme includes four major improvements over current schemes in WRF: (1) hydrometeors’ size distribution based on a triple-moment (the zeroth, second, and third moments) closure method, (2) the shapes of pristine ice and snow aggregate evolve in a realistic manner, (3) apparent density of pristine ice, aggregate, and graupel can vary freely according to the growth conditions, and (4) fall speed calculation for frozen particles considers the dependence on shape and density. Two extreme precipitation cases were selected for simulating the impact of ice parameterizations: an afternoon thunderstorm with violent rainfall over the Taipei metropolis in Taiwan and a heavy precipitation over the New York State in the U.S.A. Validations with observations and further evaluations through sensitive analyses will be presented.

2.
AS36-D5-AM1-333-008 (AS36-A032)
 
The Importance of Microphysical Process Parameterizations on Extreme Weather
Kara SULIA#+, Fangqun YU, Qilong MIN, Gan LUO, Matthew GIBBONS, Lauriana GAUDET, Yuyi DU, Yanda ZHANG
University at Albany, State University of New York, United States
#Corresponding author: ksulia@albany.edu +Presenter

Extreme weather resiliency relies on accurate model prediction. Predictive model accuracy is controlled by a number of critical components and the interactions of those components. With the increase in high-performance computing resources, it has become increasingly evident that the predictive accuracy of research forecasting models depends not only on larger scale dynamical and physical interactions, but also on microphysical processes. It is found that, at times, microphysical processes can largely impact the thermodynamic structure of a system through the varying release of latent heat and also the quantity and type of precipitation. Such microphysical processes include, but are not limited to, detailed aerosol-cloud interactions, cloud condensation and ice nucleation, ice crystal growth through deposition and collection, and sedimentation processes. Through the National Science Foundation Program for International Research and Education (NSF PIRE), micrometeorology experts at the University at Albany in concert with National Taiwan University, National Central University, and others, have been tasked with the responsibility of investigating the impact of microphysical processes on extreme weather. Investigations using existing detailed aerosol and ice microphysical schemes are employed, and resulting parameterization refinements will provide a necessary component to the improved accuracy of extreme weather predictability.

3.
AS36-D5-AM1-333-009 (AS36-A036)
 
Numerical Simulation of a Winter Storm in Upstate New York: Comparisons Between Bulk and Spectral Bin Microphysics
Qilong MIN#+, Matthew GIBBONS, Yuyi DU
University at Albany, State University of New York, United States
#Corresponding author: qmin@albany.edu +Presenter

Accurate numerical simulation of ice and mixed phase processes that occur during cloud and precipitation formation and growth remains a challenge. This is due to the complex and non-linear interactions between aerosols and liquid and ice particles occurring in a mixed phase environment. In order to improve the understanding of these processes, a 6 January 2014 winter storm in the upstate New York region has been simulated using the Weather Research and Forecasting (WRF) model. Results from a bulk and two different spectral bin (SBM) microphysics schemes are compared to test the sensitivity of cloud and precipitation formation processes to different mechanisms. Comparisons between observations and model results suggest that spatial distribution and surface accumulation of precipitation are represented fairly well by the numerical simulations. However, the total contributions of liquid and ice water content to the final results are significantly different between the bulk (more liquid) and SBM (more ice) simulations. Unlike predetermined particle size distributions (PSD) in the bulk schemes, SBM microphysics allows for a naturally evolving PSD to be simulated. As the PSDs in the SBM can be easily converted into radar reflectivity values, comparison with radar and in-situ observations will be used to further assess model agreement and gain a deeper insight into the cloud and precipitation formation processes.

5.
AS36-D5-AM1-333-010 (AS36-A034)
 
Investigation of Cloud-Aerosol Interaction for Extreme Precipitation Events Using NCEP Global Models
Sarah LU1#+, Sheng-Po CHEN1, Wei-Chyung WANG1, Huang-Hsiung HSU2, Qilong MIN1, Kara SULIA1, Fangqun YU1
1 University at Albany, State University of New York, United States, 2 Academia Sinica, Taiwan
#Corresponding author: sarah.lu@noaa.gov +Presenter

While understanding the climate impacts of the complex cloud-aerosol-radiation interactions remains a major frontier in climate sciences, there have been significant processes in developing process-level representations of clouds and aerosols as well as in understanding the processes relevant to aerosol-cloud-radiation interactions. NASA Global Modeling and Assimilation Office (GMAO) is revamping the existing treatments of clouds and aerosols in Goddard Earth Observing System Model, Version 5 (GEOS-5) by introducing a double-moment cloud microphysics scheme and coupling it with a modal aerosol model. This physically-based cloud/aerosol package at GMAO is later implemented into NOAA Global Forecast System (GFS). In this presentation GFS is used to simulate two extreme precipitation events: New York snow storm in January 2014 and Louisiana flooding in August 2016. The GFS results are then compared with the simulations from regional Weather Research and Forecasting (WRF) model with fully size-resolved microphysics. These comparison could provide an insight on optimal configuration for NWP models in the contexts of representing aerosol process. We will also investigate aerosol-cloud microphysics-precipitation interaction and the uncertainty in model precipitation simulation under different climate regimes.

6.
AS36-D5-AM1-333-011 (AS36-A037)
 
Study of Aerosol Impacts on Extreme Precipitation Using WRF-Chem Coupled with an Advanced Particle Microphysics Model
Fangqun YU#+, Yanda ZHANG, Gan LUO
University at Albany, State University of New York, United States
#Corresponding author: fyu@albany.edu +Presenter

Tropospheric aerosols impact cloud microphysical processes, latent heat release, thermodynamic structure, and precipitation by acting as cloud condensation nuclei (CCN) or ice nuclei (IN). These aerosol effects depend strongly on the size distribution, composition, hygroscopic properties, and mixing state of atmospheric particles. We have incorporated a size and composition resolved advanced particle microphysics (APM) model into a recent version of WRF-Chem. The APM model separates secondary particles (represented by 40 bins and composed of sulfate, nitrate, ammonium, and secondary organic aerosol) from four different types of primary particles (20, 15, 15, and 15 bins for sea salt, dust, black carbon, and primary organic carbon, respectively) while it explicitly predicts the amount of secondary species coated on each type of primary particles. Here we employ WRF-Chem-APM to investigate the impact of aerosols on extreme precipitation events in Eastern United States and East Asia, both under the influence of anthropogenic and natural emissions. The contributions of long range transported dust particles, which are known to be good IN, are considered by using the aerosol concentrations at the WRF-Chem boundaries from a global aerosol model (GEOS-Chem-APM). The simulations with aerosol effects included (i.e, WRF-Chem-APM) are compared to those without (i.e., WRF). The differences in simulated cloud properties (cloud droplet and ice particle sizes, liquid and ice water contents, etc.) as well as locations and timing of precipitation will be presented. We will also discuss the uncertainties associated with aerosol and cloud microphysics representations in the model and implications for improving the model to better forecast extreme precipitations.

7.
AS36-D5-AM1-333-012 (AS36-A001)
 
Aerosol Effects on Clouds and Precipitation Over East Asia
Wei-Chyung WANG1#+, Pay-Liam LIN2, Jen-Ping CHEN3, Guoxing CHEN1, Yangyang SONG1, Bo-Yi LU4, Tzu-Chin TSAI3
1 University at Albany, State University of New York, United States, 2 National Central University, Taiwan, 3 National Taiwan University, Taiwan, 4 University of Hawaii at Manoa, United States
#Corresponding author: wcwang@albany.edu +Presenter

Progress of a coordinated research task using WRF model to study aerosol effects on precipitation over monsoon Asia is reported. Two studies are conducted: the first on the responses of vertical cloud properties (microphysics and fraction), the circulation and precipitation over the eastern China; and the second on the sensitivity of heavy precipitation to cloud microphysical schemes used in simulating Mei-Yu front over the northern Taiwan. Both studies employ the NTU cloud microphysical scheme.

For eastern China, the effects of more aerosols produce more but smaller cloud droplets (and also larger cloud water); and more low- and high-clouds but fewer mid-clouds. However, these characteristics exhibit strong regional variations. For example, the cloud liquid water content increases in South China and the Yangtze-Huai River Valley (YHRV), but decreases in North China; low- and high-cloud fractions decrease in South and North China, but increase in the YHRV. The precipitation changes are highly correlated with the intensification and westward extension of the western North-Pacific Subtropical High, which favor more (and longer duration) rainfall over the YHRV but less (and shorter) rainfall over other regions.

In addition to the NTU scheme, the Goddard 4ice microphysics scheme was also used to simulate the June 11, 2012 Mei-Yu front event, which brought heavy rainfall to the northern Taiwan. Although both schemes capture the observed landing time, but the spatial distribution of precipitation is different owing to the different time evolution of ice and rainwater mixing ratios associated with the front movement. Compared to observations, the NTU scheme captures the strength of reflectivity and rainfall when the front landed, but the location was further south. On the other hand, the 4ice scheme simulates a weaker reflectivity but better landing location yields more reasonable precipitation distribution.

8.
AS36-D5-AM1-333-013 (AS36-A040)
 
A Pilot Study on Warm Rain Process in Aerosol-Rich Environment
Sheng-Hsiang WANG1#+, Ying-Chieh CHEN1, Pay LIAM1, Kao-Shan CHUNG1, Qilong MIN2, Everette JOSEPH2
1 National Central University, Taiwan, 2 University at Albany, State University of New York, United States
#Corresponding author: shenghsiang.wang@gmail.com +Presenter

Taiwan is located in the downwind area of Asian continental outflow where frequently received polluted air mass (i.e. aerosols) and clouds, especially for winter monsoon seasons. Potentially, aerosols can alter cloud life cycle and precipitation distribution through the radiation and microphysical effects. Previous study shows that an increase in aerosol loading could suppress precipitation, adjust the stability of the boundary layer. In order to explore the nature of aerosol-cloud-precipitation interactions, a pilot experiment was carried out at National Central University (NCU) (24.97N, 121.19E) during Oct 24 – Nov 30, 2016. We integrated observations those include rain gauge, Joss-Waldvogel Disdrometer (JWD), radiosonde, unmanned aerial vehicle (UAV), sun-photometer (AERONET), lidar (MPLNET), and other meteorological measurements in NCU observatory. A radar located in Wufenshan Weather Radar Station (25.04N, 121.46E; ~60 km north of NCU) provided the information of precipitation echo from warm clouds. In this study, we will use various observations to establish a preliminary understanding of aerosol impacts on cloud microphysical properties and changes in rain particle size, concerning (i) regional properties of aerosols from MPLNET and AERONET, (ii) cloud properties from radar, (iii) drop size distribution from JWD, (iv) vertical distribution of aerosols and clouds.

AS36 - Extreme Weather Resiliency: Prediction and Response Strategies
Friday, August 11, 2017 | 333 | 11:00-12:30
1.
AS36-D5-AM2-333-014 (AS36-A028)
 
Impacts of Data Assimilation and Microphysics Schemes on Simulations of Heavy Rainfall Event
Pay-Liam LIN1#+, Bo-Yi LU2, Wei-Kuo TAO3, Ching-Sen CHEN1, Jen-Ping CHEN4
1 National Central University, Taiwan, 2 University of Hawaii at Manoa, United States, 3 NASA Goddard Space Flight Center, United States, 4 National Taiwan University, Taiwan
#Corresponding author: tliam@atm.ncu.edu.tw +Presenter

In the evening of 11 June and early morning of 12 June 2012, a heavy rainfall event with the accumulated rainfall of 434.5 and 476.5 mm occurred over northwestern coast of Taiwan and Taipei Basin, respectively. This event occurred under a favorable large-scale environment including: a quasi-stationary upper-level East Asia trough; upper-level divergence; middle-level short-wave trough; low-level high equivalent potential temperature; low-level high moisture flux; a low level of free convection (LFC); a quasi-stationary surface front over northern Taiwan and subsynoptic-scale ascending motion over the northern Taiwan Strait and northern Taiwan. On 10 and 11 June, high moisture flux was transported from Indian Ocean and Bay of Bangle through Indochina Peninsula, South China Sea to Taiwan. The low-level moisture air was lifted and produced heavy rainfall in the windward side of central and southern Taiwan and mountainous areas. In the late night of 11 and the morning of 12 June, a surface front moved from southeastern China coast to northern Taiwan and became quasi-stationary. The convergence between the southwesterly barrier jet and the westerly/northwesterly wind behind the wind shift line associated with the low-level trough axis occurred over northeastern Taiwan Strait and northwestern coast of Taiwan. Because of the quasi-stationary surface front was present over northern Taiwan, intense radar reflectivity frequent occurred over the convergence area and moved into northwestern Taiwan and Taipei Basin. In addition, the orographic lifting of the prevailing wind over southern Taipei Basin enhanced rainfall. As a result, heavy rainfall occurred in the low land of northern Taiwan. The favorable conditions for the occurrence of heavy rainfall are investigated by observational data analysis and numerical simulations with the Weather Research and Forecast (WRF) model. The impacts of data assimilation and several microphysics schemes on simulations of the mesoscale convective systems associated with this heavy rainfall event will be discussed.

2.
AS36-D5-AM2-333-015 (AS36-A019)
 
Predicting the Heavy Precipitation Episode on 16 June 2008 with the WRF-LETKF Radar Assimilation System
Hsiang-Wen CHENG+, Shu-Chih YANG#, Chih-Chien TSAI
National Central University, Taiwan
#Corresponding author: shuchih.yang@gmail.com +Presenter

This study applies the WRF-Radar Local Ensemble Transform Kalman Filter to investigate the short-term predictability of a heavy rainfall event in Taiwan on 16 June, 2008. We investigate the impact of assimilating radar observations on rainfall prediction and key factors for making the convective-scale assimilation effective during Meiyu seasons.

Results suggest that assimilating radar radial velocity improves the wind field from offshore to coastal of southwestern Taiwan, while assimilating reflectivity increases the total water content. Only when both observations are assimilated can the temporal variations and spatial distribution of rainfall be correctly represented. For convections associated with multi-scale interactions, how to initialize the ensemble for convective-scale assimilation is crucial. The impact of radar data on rainfall prediction becomes more effective when the ensemble was initialized from an ensemble with a strong moisture transport over South China Sea through the southwesterly jet. Also, strategies, such as improving the procedure of the data quality control and additively perturbing the ensemble, can further improve the rainfall prediction for forecast hours longer than 6 hour.

3.
AS36-D5-AM2-333-016 (AS36-A017)
 
A Sub-Kilometer Modeling Study of the Severe Thunderstorm Event with Urban Flooding at Taipei on 14 June 2015
Jyong-En MIAO1,2#+, Ming-Jen YANG1
1 National Taiwan University, Taiwan, 2 Central Weather Bureau, Taiwan
#Corresponding author: jjackm123@gmail.com +Presenter

On 14 June 2015, a severe afternoon thunderstorm event associated with cell merger developed within the Taipei basin, which produced an hourly rainfall of 131 mm/h and resulted in urban-scale flooding.  Cloud-resolving numerical simulations were performed to capture reasonably well the development and evolution of the afternoon thunderstorms observed on that day. The mesoscale model WRF was used in this study with the horizontal grid size nesting down to 0.5 km and 55 vertical layers in order to explicitly resolve the deep convection. The merging between three intense convective cells was realistically reproduced by the simulations and the model results were in good agreement with radar observations. The low-level convergence was essential to provide the lifting mechanism necessary for the cell merger. The convergence between the cold-air outflow with see-breeze circulation, as well as the interactions between the two cold-air outflows associated with downdrafts, were the main factors that enhanced the low-level convergence. The formation and development of new convection from the cloud bridge was the main reason for the occurrence of the cloud merger. The influence of latent cooling by evaporation and melting on the occurrence of the cell merger was further analyzed. Evaporation cooling played an important role in the cell merger process, whereas melting cooling played a relatively minor role. The experiments with the removal of local topography (Mount Datun) indicated that the channel effect by Mt. Datun intensified the sea-breeze circulation and then enhanced the low-level convergence within the Taipei basin. Finally, the experiments of the microphysical parameterizations showed that ice-phase microphysical processes were critical for the development of thunderstorm outflows and the associated intense rainfall.

4.
AS36-D5-AM2-333-017 (AS36-A003)
 
Impacts of Including Rain-Evaporative Cooling in the Initial Conditions on the Prediction of a Coastal Heavy Rainfall Event During Timrex
Chuan-Chi TU1#+, Yi-Leng CHEN2, Shu-Ya CHEN3, Bill KUO3, Pay-Liam LIN1
1 National Central University, Taiwan, 2 University of Hawaii at Manoa, United States, 3 University Corporation for Atmospheric Research, United States
#Corresponding author: beth0509@gmail.com +Presenter

A cycling run, which began 36 h before the model forecast, was employed to assimilate special Terrain-influenced Monsoon Rainfall Experiment (TiMREX) soundings, Global Telecommunications System (GTS) data, and Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) global positioning system (GPS) radio occultation (RO) refractivity profiles to improve the model initial conditions provided by the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) to study a coastal, heavy rainfall event over southwestern Taiwan during 15–16 June 2008. The 36-h cycling run with data assimilation (DA_ALL_DATA run) has a positive impact on the depiction of subsynoptic flow in the model initial conditions at 1200 UTC 15 June, including the warm moist tongue and southwesterly monsoon flow over the open ocean. Furthermore, the cold pool caused by the evaporative cooling of antecedent rains and orographic blocking over southwestern Taiwan are better resolved in the nested high-resolution domain in the DA_ALL_DATA run as compared to the initial conditions provided by the NCEP GFS. As a result, the heavy rainfall along the southwestern coast and afternoon localized heavy rainfall over northern Taiwan are better predicted in the DA_ALL_DATA run.

Model sensitivity tests are also performed to diagnose the effects of terrain and rain-evaporative cooling on the intensity and depth of the cold pool and degree of orographic blocking on the southwesterly flow over southwestern Taiwan. It is apparent that including rain-evaporative cooling from antecedent rains and orographic effects in the model initial conditions are important to account for the predicted rainfall distribution of this coastal rainfall event.

AS22 - Enso and Iod Theory, Impact and Prediction
Friday, August 11, 2017 | 333 | 14:00-15:30
1.
AS22-D5-PM1-333-001 (AS22-A008)
 
Atmospheric Energetics Over the Tropical Pacific During the ENSO Cycle
Jianping LI1#+, Di DONG2, Lidou HUYAN2, Jiaqing XUE2
1 Beijing Normal University, China, 2 Chinese Academy of Sciences, China
#Corresponding author: ljp@lasg.iap.ac.cn +Presenter

The atmospheric perturbation potential energy (PPE) over the tropical Pacific is calculated and analyzed in a composite ENSO cycle. The PPE over the tropical Pacific troposphere increases during El Niño and decreases during La Niña, displaying two centers symmetrical about the Equator and delaying the central–eastern Pacific SST anomaly by 2 months. Generated from atmospheric diabatic heating, the smaller part of PPE in the lower troposphere varies synchronously with the central–eastern Pacific SST through sensible heating, while the larger part of PPE occurs in the middle and upper troposphere and lags the central–eastern Pacific SST about one season due to latent heat release. As the tropical Pacific PPE peaks during the boreal late winter in an El Niño event, two anticyclones form in the upper troposphere due to the Gill Model response. More PPE is converted to atmospheric kinetic energy (KE) above the central–western Pacific, but less over the eastern Pacific, leading to intensified Hadley circulations over the central–western Pacific and weakened Hadley circulations over the eastern Pacific. The strengthened Hadley circulations cause surface easterly wind bursts through KE convergence in the western equatorial Pacific, which may trigger a La Niña event. The reverse situation occurs during La Niña. Thus, the response of the Hadley circulations in the central–western Pacific provide a negative feedback during the ENSO cycle.

2.
AS22-D5-PM1-333-002 (AS22-A010)
 
Target Observations for Improving Initializations of Two Types of El Nino Predictions
Wansuo DUAN#+
Chinese Academy of Sciences, China
#Corresponding author: duanws@lasg.iap.ac.cn +Presenter

In this paper, the spring predictability barrier (SPB) problem for two types of El Niño events and related target observations are investigated. This is enabled by tracing the evolution of a conditional nonlinear optimal perturbation (CNOP) that acts as the initial error with the biggest negative effect on the El Niño predictions. We show that the CNOP-type errors for Central Pacific-El Niño (CP-El Niño) events can be classified into two types: the first are CP-type-1 errors possessing a sea surface temperature anomaly (SSTA) pattern with negative anomalies in the equatorial central western Pacific, positive anomalies in the equatorial eastern Pacific, and accompanied by a thermocline depth anomaly pattern with positive anomalies along the equator. The second are, CP-type-2 errors presenting an SSTA pattern in the central eastern equatorial Pacific, with a dipole structure of negative anomalies in the east and positive anomalies in the west, and a thermocline depth anomaly pattern with a slight deepening along the equator. CP-type-1 errors grow in a manner similar to an Eastern Pacific-El Niño (EP-El Niño) event and grow significantly during boreal spring, leading to a significant SPB for the CP-El Niño. CP-type-2 errors initially present as a process similar to a La Niña-like decay, prior to transitioning into a growth phase of an EP-El Niño-like event; but they fail to cause a SPB. For the EP-El Niño events, the CNOP-type errors are also classified into two types: EP-type-1 errors and 2 errors. The former is similar to a CP-type-1 error, while the latter presents with an almost opposite pattern. Both EP-type-1 and 2 errors yield a significant SPB for EP-El Niño events. For both CP- and EP-El Niño, their CNOP-type errors that cause a prominent SPB are concentrated in the central and eastern tropical Pacific. This may indicate that the prediction uncertainties of both types of El Niño events are sensitive to the initial errors in this region. Especially, hindcast experiments verify this inference. The region therefore represent a common sensitive area for the targeted observation of the two types of El Niño events, which may provide useful information to the new observing plan of tropical Pacific (TPOS20).

3.
AS22-D5-PM1-333-003 (AS22-A005)
 
Was 2016 a La Nina Year? A Maritime Continent Perspective
Thea TURKINGTON1#+, Bertrand TIMBAL2, Raizan RAHMAT1
1 Centre for Climate Research Singapore, Singapore, 2 National Environment Agency, Singapore
#Corresponding author: thea_turkington@nea.gov.sg +Presenter

Towards the end of 2016 there was confusion around declaring a La Nina event across the Maritime continent; various ENSO indices had reached only borderline La Nina values, while broad scale La Nina like conditions had been present since mid-2016. Accounting for the effect of rising global sea surface temperatures (SSTs) could have potentially made the declaration more straightforward. The Nino 3.4 index has been valuable in determining the ENSO state, however, as a raw measure of SST anomalies, on-going global warming is expected to partly mask the colder La Nina state. Removing the warming is complex as it is embedded within naturally occurring modes of variability of inter-annual (ENSO itself) and decadal timescales. Therefore, a method is proposed to robustly remove tropical warming from ENSO SST based indices. The method takes into consideration uncertainties in the estimation of the warming trends due to the analysis period and the existence of several SST datasets. Once this detrending is applied to commonly used ENSO indices, 2016 appears to have witnessed a La Nina episode starting from the end of July. The state of the atmosphere responded well to the SST anomalies providing evidence of a coupling of the ocean-atmosphere system. Low level wind, OLR, and rainfall anomalies all matched the detrended SST patterns and composites based on previous La Nina cases. In addition to the classical center Pacific signature, a strong signature in the western Pacific in 2016 may further explain particular aspects of the 2016 La Nina and its responses across the Indian Ocean. These results have significance for the way future ENSO variability should be monitored and how dynamical seasonal predictions should be used, both in the Maritime Continent and beyond.

4.
AS22-D5-PM1-333-004 (AS22-A011)
 
Modulation of Bjerknes Feedback on the Decadal Variations in ENSO Predictability
Fei ZHENG1#+, Xiang-Hui FANG2, Jin-Yi YU3, Jiang ZHU1, Xichen LI4
1 Chinese Academy of Sciences, China, 2 Indian Academy of Pediatrics, China, 3 University of California, Irvine, United States, 4 Scripps Institution of Oceanography, United States
#Corresponding author: zhengfei@mail.iap.ac.cn +Presenter

Clear decadal variations exist in the predictability of the El Niño–Southern Oscillation (ENSO), with the most recent decade having the lowest ENSO predictability in the past six decades. The Bjerknes Feedback (BF) intensity, which dominates the development of ENSO, has been proposed to determine ENSO predictability. Here we demonstrate that decadal variations in BF intensity are largely a result of the sensitivity of the zonal winds to the zonal sea level pressure (SLP) gradient in the equatorial Pacific. Furthermore, the results show that during low ENSO predictability decades, zonal wind anomalies over the equatorial Pacific are more linked to SLP variations in the off-equatorial Pacific, which can then transfer this information into surface temperature and precipitation fields through the BF, suggesting a weakening in the ocean-atmosphere coupling in the tropical Pacific. This result indicates that more attention should be paid to off-equatorial processes in the prediction of ENSO.

5.
AS22-D5-PM1-333-005 (AS22-A007)
 
The Influence of ENSO on an Oceanic Eddy Pair in the South China Sea
Xiaoqing CHU1#+, Changming DONG2,3, Yiquan QI1, Gengxin CHEN1
1 Chinese Academy of Sciences, China, 2 Nanjing University of Information Science & Technology, China, 3 University of California, Los Angeles, United States
#Corresponding author: chuxq@scsio.ac.cn +Presenter

An eddy pair off the Vietnam coast is one of the most important features of the summertime South China Sea circulation. Its variability is of interest due to its profound impact on regional climate, ecosystems, biological processes, and fisheries. This study examines the influence of the El Niño–Southern Oscillation (ENSO), a large-scale climatic phenomenon, on the interannual variability of this regional eddy pair using satellite observational data and historical hydrographic measurements. Over the last three decades, eddy pair events were absent in 1988, 1995, 1998, and 2010, coinciding with strong El Nino-to-La Nina transitions. Composite analyses showed that the strong transition events of ENSO led to radical changes in the summer monsoon, through the forcing of a unique sea surface temperature anomaly structure over the tropical Indo-Pacific basin. With weaker zonal wind, a more northward wind direction, and the disappearance of a pair of positive and negative wind stress curls, the eastward current jet turns northward along the coast and the eddy pair disappear. Such regional oceanic response to large-scale climate variability is of scientific interest and societal importance to the regional community. It helps to improve regional eddy activity modeling, such as importance to resolve the eddy pair in a numerical model.

6.
AS22-D5-PM1-333-006 (AS22-A006)
 
Optimal Error Analysis of the Intraseasonal Convection Due to the Uncertainties of the Sea Surface Temperature in a Coupled Model
Xiaojing LI1+, Youmin TANG1,2#, Zhixiong YAO1
1 State Oceanic Administration, China, 2 University of Northern British, Canada
#Corresponding author: ytang@sio.org.cn +Presenter

The predictability of the convection related to the Madden-Julian Oscillation (MJO) is studied using a coupled model CESM (Community Earth System Model) and the climatically relevant singular vector (CSV) approach. The CSV approach is an ensemble-based strategy to calculate the optimal initial error on climate scale. In this study, we focus on the optimal initial error of the sea surface temperature in Indian Ocean, where is the location of the MJO onset. Six MJO events are chosen from the 10 years model simulation output. The results show that the large values of the SVs are mainly located in the bay of Bengal and the south central IO (around (25°S, 90°E)), which is a meridional dipole-like pattern. The fast error growth of the CSVs have important impacts on the prediction of the convection related to the MJO. The initial perturbations with the SV pattern result in the deep convection damping more quickly in the east Pacific Ocean. Moreover, the sensitivity studies of the CSVs show that different initial fields do not affect the CSVs obviously, while the perturbation domain is a more responsive factor to the CSVs. The rapid growth of the CSVs is found to be related to the west bay of Bengal, where the wind stress starts to be perturbed due to the CSV initial error. These results contribute to the establishment of an ensemble prediction system, as well as the optimal observation network. In addition, the analysis of the error growth can provide us some enlightment about the relationship between SST and the intraseasonal convection related to the MJO.

AS41 - Exploration and Science of the Earth’s Lower and Middle Atmosphere: Past, Present and Future Perspectives
Friday, August 11, 2017 | 334 | 08:30-10:30
1.
AS41-D5-AM1-334-009 (AS41-A019)
 
Toward Vertical Profiling of Atmospheric Species from Space: Recent Advances and Future Prospect
Sachiko HAYASHIDA1#+, Naveen CHANDRA1, Prabir PATRA2,3, Naoko SAITOH4, Yasuko KASAI5
1 Nara Women's University, Japan, 2 Japan Agency for Marine-Earth Science and Technology, Japan, 3 Tohoku University, Japan, 4 Chiba University, Japan, 5 National Institute of Information and Communications Technology, Japan
#Corresponding author: sachiko@ics.nara-wu.ac.jp +Presenter

Satellite measurements have a great advantage in observing the earth’s environment at wide coverage, which are expected to fill the measurement gaps in high-precision ground-based station network. Recent technological advances have made it possible to observe concentrations of various atmospheric minor species from space such as ozone and ozone precursors as well as the major greenhouse gases, such as carbon dioxide (CO2), methane (CH4). However, most of passive sensors in the spectral range of ultraviolet (UV), visible (VIS) and short-wavelength infrared (SWIR) can provide the information only on column amount of those species, and thus improvement of our understanding on spatial distribution of those species is still limited.

For example, the deriving vertical distribution of ozone in the lower troposphere is a big challenge in satellite-borne measurements because almost 90% of ozone resides in the stratosphere. In spite of the difficulty, recent feasibility studies (e.g., Kasai et al., paper in preparation) have proved that combined use of measurements by Thermal Infrared (TIR) and UV/VIS sensors raise the possibility to extract information on lower tropospheric ozone. Liu et al. (2010) successfully derived ozone profiles from the surface up to 60 km into 24 layers from only the UV spectra observed by Ozone Monitoring Instrument (OMI). Hayashida et al. (2015) examined the lowermost layer, corresponding to a layer from 0 km to about 2.5~3 km, of their products and assured the reliability of the ozone in the lower troposphere under enhancedconditions.

On the other hand, satellite-borne measurements have revealed high concentrations of columnar amount of CH4 over Asia, which have been often discussed in terms of a linkage with high methane emission sources. However, finding a connection between high columnar concentrations and local emissions is not straightforward because of complex atmospheric transport mechanisms. We will show those examples and discuss future prospect of profiling of atmospheric minor species from space.

2.
AS41-D5-AM1-334-010 (AS41-A003)
 
Investigation of Extinction and Lidar-Ratio of Cirrus Clouds by Using Multichannel Raman Lidar Over Western Site: A Case Study
Krishna Kumar SHUKLA#+, Som Kumar SHARMA, Rajesh VAISHNAV
Physical Research Laboratory, India
#Corresponding author: kkshukla.prl@gmail.com +Presenter

The presence of Cirrus clouds in the lower and upper troposphere have significant impact on the atmospheric radiative balance and it became essential to quantify their role in the atmospheric processes. Its measurements using the state-of-the-art techniques are limited, especially over the Indian region. In order to describe the temporal and spatial evolution of Cirrus cloud in the troposphere, we have required a high resolution remote sensing techniques. In this paper, we analyse the Cirrus clouds properties by using the multichannel Raman Lidar observation at two wavelengths, @ 355 nm and @ 532 nm for different cases during pre-monsoon season over) a western site, Ahmedabad (23.02o N, 72.5o E, 55 m, amsl), in India. The Lidar backscattering signal is a main indicator for the presence of Cirrus cloud in the lower atmosphere and also we can see their impact on tropopause layer. During all the cases, the Cirrus cloud altitude vary from 6-12 km over the site. An upward and downward movement of clouds is also found during day-time and night-time, respectively. It is also observed that the Lidar ratio is higher in the height range of 6-12 km and above about 12 km, it is smaller. Furthermore, the vertical extent of cirrus clouds will also be used as an important input parameter in further refinement of regional weather forecast models over the site. 

3.
AS41-D5-AM1-334-011 (AS41-A007)
 
Assessment of Seasonal Variations of BTEX Hydrocarbons and Their Ozone Forming Potential in Ambient Urban Atmosphere of Delhi, India
Pallavi SAXENA#+
Jawaharlal Nehru University, India
#Corresponding author: pallavienvironment@gmail.com +Presenter

Ambient Benzene, Toluene, Ethylbenzene and Xylene (BTEX) samples were analyzed in three seasons viz. summer (Apr-Jun), monsoon (July – Sept) and winter (Nov – Feb) during the period 2010-2011 to determine seasonal variations at three different sites in Delhi, India. The samples were analyzed by gas chromatography (GC-FID) to determine BTEX by active sampling method. BTEX is considered as most hazardous group among VOCs by USEPA because they are known to cause impacts on health and environment. At all the sites Toluene was found to be highest among BTEX. The maximum mean concentration of BTEX was observed during winters and lowest during monsoon season. Two way ANOVA test showed statistically significant differences seasonally (p<0.05). High toluene to benzene T/B (>1) ratio was found which indicates vehicular emissions was the main source of these pollutants. BTEX were also evaluated for their ozone forming potential (OFP). It was found that Toluene and xylenes were found as the highest contributing hydrocarbons towards ozone forming potential among BTEX.

4.
AS41-D5-AM1-334-012 (AS41-A011)
 
Study of Middle and Upper Atmosphere Using Lidars and Incoherent Scatter Radar at Arecibo
Shikha RAIZADA#+, Jens LAUTENBACH, Eframir FRANCO, Christiano GARNETT MARQUES BRUM
SRI International, Puerto Rico
#Corresponding author: shikha@naic.edu +Presenter

The unique instrument cluster at Arecibo Observatory (AO) is well suited for studying coupling between the middle and the upper atmosphere. This paper will focus on the recent developments and highlight some interesting topics that have been investigated from Arecibo recently.

The AO houses three lidars, two of them are configurable either as resonance or Rayleigh systems, and the third one is a Doppler K lidar tuned to the resonance line of potassium (K) at 770 nm. The other resonance lidar can be tuned to one of metallic species (Na, Ca, Ca+, Fe) deposited through meteor input between the altitudes ~ 80 – 120 km. This provides excellent opportunity to probe 30 – 120 km region by combining Rayleigh and Resonance techniques. Also, simultaneous ISR and resonance lidar measurements allow us to perform ion-neutral coupling and validate mesospheric chemistry. One such studies from Arecibo combined electron density (Ne) observations from ISR, Ca and Ca ion from resonance lidar to examine the characteristics of neutral and ionized layers along with their neutralization lifetimes as predicted by mesospheric models.

We will also present some case studies pertaining to neutral Sporadic layers observed in Na (NaS) and Fe (FeS) along with their relationship to Sporadic E (ES) as seen in ISR data. This study revealed that Nais stronger than FeS for these events and factors responsible for such behavior will be discussed.

5.
AS41-D5-AM1-334-013 (AS41-A013)
 
Determination of Branching Ratios for the O(1S) and O2(0,0) Airglow VERs
Yolian AMARO-RIVERA1#+, Tai-Yin HUANG2, Julio URBINA1
1 Pennsylvania State University, United States, 2 Penn State Lehigh Valley, United States
#Corresponding author: yua120@psu.edu +Presenter

A virtual experiment using the MACD-90 model is conducted to investigate the Volume Emission Rates (VER) of O(1S) greenline and O2(0,0) atmospheric band when using different branching ratios for their productions. The VER profiles are simulated by the MACD-90 model using the same atmospheric conditions in the WINDII observations. We then match the simulated VERs to the measured VERs to determine the branching ratios. The branching ratio, alpha, determines the O(1S) VER production whereas the branching ratios, epsilon and alpha, determine the O2 atmospheric band VER production. Previous simulation results using the MACD model show that the airglow emissions vary with different branching ratios in terms of the emission magnitude, the shape, and the wave-induced response. Therefore, the selection of the branching ratios is important because it also affects the wave-induced secular variations and fluctuations of airglow emissions, particularly atmospheric bands. Our study makes it possible to determine the branching ratios by using WINDII's airglow VER measurements and our model simulations.

6.
AS41-D5-AM1-334-014 (AS41-A024)
 
F-Region Response to St. Patrick Storm (17 -19 March, 2015) Over Arecibo
Shikha RAIZADA1#+, Christiano GARNETT MARQUES BRUM1, Bela FEJER2, Raj Kumar HAJRA3, Ezequiel ECHER4
1 SRI International, Puerto Rico, 2 Utah State University, United States, 3 Centre National de La Recherche Scientifique/ Université d'Orléans, France, 4 National Institute for Space Research, Brazil
#Corresponding author: shikha@naic.edu +Presenter

The influence of a strong magnetic storm that occurred between 17 -19 March 2015 on F-region of the ionosphere will be discussed. During this storm, Dst dropped to -225 nT on 17th March. The impact on the F-region has been over Arecibo, a low latitude, has been investigated by using both ISR and ionosonde data. The Fof2 varied between 4 – 6 MHz with a decrease during the main phase of the storm around local noon, a behavior similar to the negative storm. However, during the rest of the disturbance, the F-region showed an increase in the electron concentration, in particular during the nighttime periods. Large fluctuations are observed in hmf2 with variations ~ 75 km relative to quiet time period. Periodicities ranging between 6 – 32 hours resulting from high altitude current drivers are observed, a result different from the previous storms.

7.
AS41-D5-AM1-334-015 (AS41-A029)
 
Water Soluble Inorganic Ions, OC and EC Characteristics of Winter Time Aerosols in N-NW India
Sudesh YADAV#, Sushil KUMAR+, Supriya NATH
Jawaharlal Nehru University, India
#Corresponding author: sudesh27@hotmail.com +Presenter

PM2.5 (finer) and PM2.5-10 (coarser) aerosols, collected during winter season from two Amritsar and Delhi in N-NW India, were studied for their mass concentrations, water soluble inorganic ions (WSIIs), organic carbon (OC) and elemental carbon (EC) and spatial variations. The average load of finer and coarser aerosols were 357µg/m3 and 98 µg/m3 over Delhi, and 148 µg/m3 and 53 µg/m3 over Amritsar, respectively, and exceeded the national ambient air quality standards of 60 µg/m3. The % contribution of WSIIs to total aerosol load was nearly 25% for both size aerosols over Delhi whereas at other site it was 25.8% for finer and 18.36% for coarse aerosols and limited by contribution of anthropogenic sources. Among the all WSII the order of abundance of ions in finer aerosols were SO42-> NH4+> NO3-> K+>Cl-> Ca2+> Mg2+> F- over Amritsar and SO42-> NH4+>Cl-> K+> Ca2+> NO3-> Na+> Mg2+> F- over Delhi. Similarly, the order in coarser aerosols over Amritsar was Cl-> NO3-> SO42-> NH4+> K+> Na+> Mg2+> F- and SO42->Cl-> NO3-> NH4+> Ca2+>K+> Na+> Mg2+ > F- over Delhi. Total carbon (TC) was dominated by OC over EC at both site and follows the similar trend in their mass concentrations. The OC/EC ratio was higher (2.8) in Delhi compared to Amritsar (2.0). The data revealed multiple sources such as vehicular and fossil fuel combustion, plastics and biomass burning for carbon content and WSIIs. In addition secondary process in ambient atmosphere are responsible for formation of SO42-, NH4+, NO3-from their precursorgases and secondary organic carbon (SOC) over both sampling sites. Overall, both sources and processes along with the prevailing meterological parameters including temperature inversion conditions influence the aerosol load and composition in this region.

AS18 - Advances in Understanding and Simulation of Land-atmosphere Interactions
Friday, August 11, 2017 | 334 | 11:00-12:30
1.
AS18-D5-AM2-334-001 (AS18-A006)
 
Effects of Land-Atmosphere Interactions on the Regional Climate Over Northeast Asia Based on the Simulation Results of Regional Climate Model
Myoung-Seok SUH#+
Kongju National University, South Korea
#Corresponding author: sms416@kongju.ac.kr +Presenter

I will provide here a brief review on the role of land–atmosphere interactions for the simulation of weather and regional climate over East Asia using a numerical weather prediction (NWP) and regional climate models. First, an overview on the simplified physical and biophysical processes for the heat, moisture and momentum exchanges between land and atmosphere is presented. And then, I will discuss on the current status of various land cover map over the East Asian continent which commonly used for the bottom boundary conditions of models. It is well known that land use or cover over East Asia has been changed significantly due to the rapid development of economy and increase of population. I will present the impacts of land cover changes (LCC) on the simulated surface variables over South Korea using the simulation of NWP. In addition, the impacts of land surface conditions, land cover map and leaf area index, on the short range weather forecast will be examined by using the simulation results of NWP model. After that the effects of irrigated cropland on the local and regional climate over Northeast Asia according to the intensity of East Asian monsoon will be presented using a regional climate model version 4.0 (RegCM4.0) with biosphere-atmosphere transfer scheme (BATS). In general, the LCC induces changes of biophysical parameters (e.g., albedo, roughness length, soil moisture availability…), and the interactions of land-atmosphere. In this context, I will discuss the impacts of LCC and soil moisture changes on the local and regional climates based on findings from climate models across a number of spatial and temporal scales. Finally, the dependency of land-atmosphere interactions on the regional climate and climate regimes will be discussed.

2.
AS18-D5-AM2-334-002 (AS18-A001)
 
Large-Scale Human Alteration of Land Surface Hydrology and Climate
Yadu POKHREL1#+, Tomohito J. YAMADA2
1 Michigan State University, United States, 2 Hokkaido University, Japan
#Corresponding author: ypokhrel@egr.msu.edu +Presenter

This study examines the human-induced changes in land surface water and energy balances and the associated climate impacts by using a coupled hydrological-climate model framework which also simulates the impacts of human activities on the water cycle. We present three sets of analyses using the results from two model versions-one with and the other without considering human activities; both versions are run in offline and coupled mode resulting in a series of four experiments in total. First, we examine climate and human-induced changes in regional water balance focusing on the widely debated issue of the desiccation of the Aral Sea in central Asia. Then, we discuss the changes in surface temperature as a result of changes in land surface energy balance due to irrigation over global and regional scales. Finally, we examine the global and regional climate impacts of increased atmospheric water vapor content due to irrigation. Results indicate that the direct anthropogenic alteration of river flow in the Aral Sea basin resulted in the loss of ~500 km3 of water during the latter half of the 20th century which explains about half of the total loss of water from the sea. Results of irrigation-induced changes in surface energy balance suggest a significant surface cooling of up to -3.3K over 1° grids in highly irrigated areas but a negligible change in surface temperature when averaged over sufficiently large global regions. Results from the coupled model indicate a substantial change in 2 m air temperature and outgoing longwave radiation due to irrigation, highlighting the non-local (regional and global) implications of irrigation. These results provide important insights on the direct human alteration of land surface water and energy balances, highlighting the need to incorporate human activities such as irrigation into the framework of global climate models and Earth system models.

3.
AS18-D5-AM2-334-003 (AS18-A009)
 
Impacts of Changes in Climate and Vegetation on Mercury Emissions from Wildfires
Shiliang WU1#+, Aditya KUMAR1, Yaoxian HUANG2
1 Michigan Technological University, United States, 2 Yale University, United States
#Corresponding author: slwu@mtu.edu +Presenter

Wildfires constitute an important source of atmospheric mercury (Hg) which is a global pollutant. We estimate the global Hg emissions from wildfires for the present-day and also the potential impacts from the 2000-2050 changes in climate and land use/land cover by combining statistical analysis with global data on vegetation type and coverage as well as fire activities. Global Hg emissions from wildfires are estimated to be 730 Mg year-1 for the present-day, with Africa being the largest source region, followed by Asia and South America. We find large perturbations to wildfire emissions of Hg in the context of global change, driven by the projected changes in climate, land use and land cover which all show significant spatial variations. The projected changes in land use by 2050 could decrease the global Hg emissions from wildfires by 65% mainly driven by a decline in African emissions due to significant agricultural land expansion. On the other hand, the future changes in land cover could lead to significant increases in Hg emissions over some regions (by 45% for North America and 32% for Eurasia). We also find that climate change by the 2050s could increase Hg emissions both globally (by ~30%) and regionally. Our results indicate that the future evolution of climate and land cover/land use are all important factors affecting the Hg emissions from wildfires in the coming decades.

4.
AS18-D5-AM2-334-004 (AS18-A007)
 
Improved Representation of Surface Spectral Emissivity in the GCM and its Impact on the Simulated Climate
Xianglei HUANG1#+, Xiuhong CHEN1, Mark FLANNER1, Ping YANG2, Daniel FELDMAN3, Chaincy KUO3
1 University of Michigan, United States, 2 Texas A&M University, United States, 3 Lawrence Berkeley National Laboratory, United States
#Corresponding author: xianglei@umich.edu +Presenter

Surface longwave emissivity can be less than one and vary significantly with frequency. However, in a dominant majority of climate models, the surface is assumed to be blackbody in their atmospheric modules. This study incorporates realistic surface spectral emissivity into the atmospheric component of the NCAR CESM (Community Earth System Model) version 1.1.1 and evaluates its impact on simulated climatology. By ensuring the broadband longwave flux being the same across different modules of the CESM, the TOA energy balance in the simulation can be attained without additional tuning of the model. As far as the global surface energy budget is concerned, the largest changes due to the inclusion of surface spectral emissivity are a decrease of net upward longwave flux at surface compensated by an increase of latent heat flux in similar magnitude. Global-mean surface temperature difference between the modified and standard CESM simulation is 0.54 K for the fully coupled run and 0.78 K for the slab-ocean run. The largest surface temperature difference between the modified and standard CESM simulations is over Sahara desert. The surface temperature differences in Polar Regions are also noticeable. Accordingly the sea ice fraction in the modified CESM simulation is less than that in the standard CESM simulation by as much as 0.1. Previous studies suggest a possible ice emissivity feedback when ice and water emissivities are considered. The broadband all-sky LW sea ice emissivity feedback here is estimated to be only about -0.003 Wm-2 per K, two orders-of-magnitude smaller than the surface albedo feedback.

AS18 - Advances in Understanding and Simulation of Land-atmosphere Interactions
Friday, August 11, 2017 | 334 | 14:00-15:30
1.
AS18-D5-PM1-334-005 (AS18-A014)
 
Understanding the Impact of Land Use/Cover Changes on Regional Climate Modeling for Taiwan
Chia-Jeng CHEN1#+, Chu-Chun CHEN2, Che-Min CHANG1, Jehn-Yih JUANG2, Min-Hui LO2
1 National Chung Hsing University, Taiwan, 2 National Taiwan University, Taiwan
#Corresponding author: cjchen@nchu.edu.tw +Presenter

Socio-economic development and climatic change can induce regional land use/cover changes (LUCCs) over time and subsequently alter land surface fluxes. Coping with the changing land use/cover conditions is thus critical to the accurate simulation of land-atmosphere interactions as well as regional climates.  Over the past few decades, Taiwan has experienced significant LUCCs, some of which might be accountable for disastrous weather events, impairing sustainable management. This study aims to investigate how Taiwan’s atmospheric conditions respond to LUCCs by employing the Weather Research and Forecasting (WRF) model with several versions of land use data released by the National Land Surveying and Mapping Center (NLSC) in different years (e.g., 1995 and 2007). A multi-year control run for a specific season will be set up for the WRF simulation forced with the U.S. Geological Survey land use data by default. This baseline simulation will be compared with other simulations forced with different NLSC land use data, and the specific emphasis of the comparison will be placed on some key surface variables (e.g., temperature and precipitation) to examine the changes in diurnal cycle and seasonal variations. As part of the Land Resources Core Project, whose goal is to develop prediction models for land use and diagnose how economic development shapes land use, the outcome of this study will be ultimately coupled with dynamic land use and economic models as a “one-tier” modeling framework to account for the interactions between LUCCs, regional climates, and economic activities.

2.
AS18-D5-PM1-334-006 (AS18-A015)
 
Weakened Indian Summer Monsoon is Caused by Decades of Deforestation in the Maritime Continent
Shih-Ming HUANG+, Leo OEY#, Ting-Yu LIANG
National Central University, Taiwan
#Corresponding author: lyo@princeton.edu +Presenter

The Indian Summer Monsoon (ISM) is the strongest of all monsoons on earth, and impacts the global climate [Rodwell and Hoskins 2001], as well as the lives of billions in a region of the world of rising economic and geopolitical importance [Egberink 2011; Winchester 2015]. Recent studies have indicated that the ISM has weakened [Naidu et al 2009; Turner and Annamalai 2012], due to various factors: such as increased land use [Devaraju et al 2015; Paul et al 2016] and aerosol loading [Ganguly et al 2012; Sanap et al 2015], and/or reduced land-sea thermal contrast [Saha et al 2014; Roxy et al 2015]. Here we show data indicating a prominent trend of warming and drying of the Maritime Continent, caused by decades of deforestation [Hansen et al 2013]. The warming results in a Gill’s [1980] Rossby-Kelvin wave response forced by ascending air over Sumatra, accompanied by descent over the Bay of Bengal and cyclonic wind over the western tropical Pacific and eastern Indian Ocean, which together weaken the ISM.

3.
AS18-D5-PM1-334-007 (AS18-A018)
 
Impact of Land-Atmosheric Interaction on the Severe Summer Heat Waves Over South Korea
Yeon-Woo CHOI1#+, Joong-Bae AHN1, Kyo-Moon SHIM2, Myung-Pyo JUNG2
1 Pusan National University, South Korea, 2 National Academy of Agricultural Science, South Korea
#Corresponding author: choiyw@pusan.ac.kr +Presenter

The influence of land-atmosphere interaction on the extreme heat waves in South Korea is investigated through correlation and composite analyses. Our results reveal that severe heat waves over South Korea are likely to occur more frequently and persist for longer periods particularly when precipitation deficit occurs from spring to summer. In order to identify the contribution of land-atmosphere interactions, sensitivity experiments is conducted using Weather Research and Forecasting (WRF) model with perturbed soil moisture fields. These sensitivity experiments explicitly demonstrate that spring precipitation deficit could play an important role in amplifying the summer temperature extremes over South Korea through land–atmosphere interaction. That is, precipitation deficit during warm season (February-August) can induce loss of soil moisture which subsequently results in the reduced latent cooling in summer. The reduced latent cooling can significantly amplify the summer temperature extremes in South Korea. This finding provides further evidence of relationship between spring precipitation deficit and summer temperature extremes.

4.
AS18-D5-PM1-334-008 (AS18-A011)
 
Decadal Variation of Precipitation in Saudi Arabia Induced by Agricultural Irrigation
Min-Hui LO1#+, Hao-Wei WEY1, Yoshihide WADA2,3, Eun-Soon IM4, Rong-You CHIEN1, Ren-Jie WU1
1 National Taiwan University, Taiwan, 2 NASA Goddard Institute for Space Studies/ Columbia University, United States, 3 Utrecht University, Netherlands, 4 Hong Kong University of Science and Technology, Hong Kong SAR
#Corresponding author: minhuilo@ntu.edu.tw +Presenter

Decadal variation of wet-season precipitation has been found in the arid region of central Saudi Arabia. 1980s has been a rather wet decade compared with the decades before. Previous studies have mentioned that the irrigation moisture may contribute to the precipitation anomalies in Saudi Arabia. In the current study, we show from observational data that the contribution of the variation comes mostly from February to May. As the irrigation is a localized forcing, we therefore use the Weather Research and Forecasting (WRF) Model to simulate the response of the land-atmosphere interaction to the wet soil moisture resulted from additional irrigation moisture supply. Preliminary result shows in the irrigated simulation that precipitation in central Saudi Arabia is enhanced, indicating the possible link between irrigation expansion in the 1980s and the decadal precipitation variation over central Saudi Arabia. We propose it is the anomalous convergence induced by irrigation as well as additional moisture that contribute to the enhanced precipitation over heavily irrigation region in the central Saudi Arabian. In addition, analysis on the daily precipitation from the WRF outputs indicates that positive rainfall anomalies tend to happen when there is rainfall originally; that is, irrigation enhances rainfall but not creates rainfall. The study with the same experimental design except for using the Massachusetts Institute of Technology Regional Climate Model (MRCM) is presented by Im et al. (2017).

AS31 - Regional Climate Downscaling and CORDEX: Challenges and Prospects
Friday, August 11, 2017 | 335 | 08:30-10:30
1.
AS31-D5-AM1-335-001 (AS31-A012)
 
Global and Regional Climate Model Ensembles in the CORDEX South-Asia Domain
Arun RANA#+, Grigory NIKULIN, Erik KJELLSTROM
Swedish Meteorological and Hydrological Institute, Sweden
#Corresponding author: arunranain@gmail.com +Presenter

In this study we investigate possible changes in temperature and precipitation on a regional scale over South Asia. We use data from two ensembles of climate simulations, one global and one regional, over the South Asia CORDEX domain. The global ensemble includes ten coupled atmosphere ocean general circulation models (AOGCMs) from the CMIP5 project with horizontal resolution varying from about 1º to 3º, namely CanESM2, CSIRO-Mk3, CNRM-CM5, HadGEM2-ES, NorESM1-M, EC-EARTH, MIROC5, GFDL-ESM2M, MPI-ESM-LR and NorESM1-M. In the regional ensemble all 10 AOGCMs are downscaled at the Rossby Centre (SMHI) by a regional climate model – RCA4 at 0.44º resolution under the RCP4.5 and 8.5 forcing scenarios and five of ten under the RCP2.6 one. The experimental setup allows us to illustrate how uncertainties in future climate change are related to forcing scenario and to forcing AOGCM at different time periods. Further, taking both global and regional ensembles and focusing on seasonal mean temperature and precipitation over Central Asia we, i) evaluate ability of the ensembles and their individual members to simulate the observed climatology in South Asia, ii) analyze similarities and contradictions in future climate projections between two ensembles and iii) assess how both ensembles capture the spread of the grand CMIP5 ensemble. We also address higher-order variability by showing results for changes in temperature extremes and for changes in intensity and frequency of extreme precipitation. The downscaled RCA4 ensemble has been made available through Earth System Grid Federation (ESGF).

3.
AS31-D5-AM1-335-002 (AS31-A032)
 
Projected Changes in Mean Precipitation Over Southeast Asia Region Based on the Multi-Model Simulations of SEACLID/CORDEX Southeast Asia
Fredolin T. TANGANG1,2#+, Jing Xiang CHUNG1, Ester SALIMUN1, Ju Neng LIEW1, Supari SUPARI3, Gemma NARISMA4, Tan Van PHAN5, Thanh NGO-DUC5, Jerasron SANTISIRISOMBOON2, Patama SINGHRUCK6, Dodo GUNAWAN3, Edvin ALDRIAN3, Grigory NIKULIN7, Hongwei YANG8
1 National University of Malaysia, Malaysia, 2 Ramkhamhaeng University, Thailand, 3 Agency for Meteorology Climatology and Geophysics, Indonesia, 4 Ateneo de Manila University, Philippines, 5 Vietnam National University, Viet Nam, 6 Chulalongkorn University, Thailand, 7 Swedish Meteorological and Hydrological Institute, Sweden, 8 APEC Climate Center, South Korea
#Corresponding author: ftangang@gmail.com +Presenter

The Southeast Asia (SEA) is one of the most vulnerable region to climatic changes especially extreme weather events and sea level rise. However, gaps remain in understanding how climate change affects the region due to lack of robust regional climate change information. Under the framework of WCRP Coordinated Regional Climate Downscaling Experiment (CORDEX), the Southeast Asia Regional Climate Downscaling (SEACLID)/CORDEX SEA has been established (2013-2017) to provide multi-model regional climate information (http://www.ukm.edu.my/seaclid-cordex). More than ten CMIP5 Global Climate Models (GCMs) have been successfully downscaled to 25 km resolution over the CORDEX SEA domain based on the collaboration of scientists from 20 institutions from 14 countries (Malaysia, Thailand, Vietnam, Indonesia, Philippines, Cambodia, Lao PDR, Australia, South Korea, UK, Sweden, Germany, Hong Kong, and Japan). Three Regional Climate Models have been used including RegCM4, RCA4 and also WRF. This paper summarizes key findings of model perfromances and projected future changes of mean precipitation over SEA based on these simulations. Generally, the ensemble mean showed wet biases during baseline period primarily contributed by wet biases from the RegCM4 simulations. For both RCP4.5 and 8.5 emission scenarios, the projected annual and seasonal on-land rainfall over Southeast Asia consistently showed  ~10 – ~15% drier than the current climate by  end of the 21st century, especially over the Maritime Continent. Comparison in GCM and RCM projected changes also showed inconsistency of sign of changes between the two, particularly those projected using RegCM4. This paper will also discuss more of this issue.

4.
AS31-D5-AM1-335-003 (AS31-A027)
 
Future Climate Changes in the Philippines from Multi-Model Simulations of SEACLID/CORDEX-SEA
Faye Abigail CRUZ1#+, Rochelle CORONEL2, Shane Marie VISAGA1, Darwin PEREZ3, Lyndon OLAGUERA3, Angela Monina MAGNAYE1,3, Jennifer TIBAY1,3, Emil GOZO1, Gemma NARISMA1,3, Fredolin T. TANGANG4,5, Ju Neng LIEW4, Tan Van PHAN6, Thanh NGO-DUC6, Jerasron SANTISIRISOMBOON5, Patama SINGHRUCK7, Dodo GUNAWAN8, Edvin ALDRIAN8
1 Manila Observatory, Philippines, 2 Ateneo de Davao University, Philippines, 3 Ateneo de Manila University, Philippines, 4 National University of Malaysia, Malaysia, 5 Ramkhamhaeng University, Thailand, 6 Vietnam National University, Viet Nam, 7 Chulalongkorn University, Thailand, 8 Agency for Meteorology Climatology and Geophysics, Indonesia
#Corresponding author: faye.cruz@gmail.com +Presenter

The Philippines is at high risk to climate change given the hazards experienced by the country compounded by its vulnerability. Appropriate adaptation measures need to be prepared in response to future changes, which requires robust high-resolution climate change information. In this study, future changes in Philippine climate are examined using multiple regional climate model simulations under two Representative Concentration Pathway (RCP) scenarios (RCP 4.5 and RCP 8.5) conducted under the Southeast Asia Regional Climate Downscaling / Coordinated Regional Climate Downscaling Experiment Southeast Asia (SEACLID/CORDEX SEA) Project. Since there are four types that describe the Philippine climate based on the seasonal variability in rainfall, the analysis is done for each climate type. Comparison of simulated present climate (1986-2005) with observations indicates an overall cold model bias with a dry bias over eastern Philippines particularly during the wet season of that region. The model is generally able to represent the annual cycles in temperature and rainfall. However, it is unable to capture the distinct peak in temperature from April to May for sites with climate types 1 and 3. There is also a tendency to underestimate the high rainfall at the end of the year for sites with climate types 2, 3 and 4. Initial results show comparable warming in the early 21st century under both scenarios but with larger changes under the RCP 8.5 scenario by the end of the 21st century for all climate types. On the other hand, rainfall is projected to initially increase then decline towards the end of the century for both scenarios. Projected changes in climate extremes will also be examined and discussed since these are anticipated to have more significant impacts on various sectors.

5.
AS31-D5-AM1-335-004 (AS31-A034)
 
Projected Future Changes of Mean Precipitation Over Thailand from Multi-Model Regional Climate Simulations of SEACLID/CORDEX Southeast Asia
Jerasron SANTISIRISOMBOON1#+, Fredolin T. TANGANG1,2, Jing Xiang CHUNG2, Ester SALIMUN2, Ju Neng LIEW2, Supari SUPARI3, Gemma NARISMA4, Tan Van PHAN5, Thanh NGO-DUC5, Patama SINGHRUCK6, Dodo GUNAWAN3, Edvin ALDRIAN3, Grigory NIKULIN7, Hongwei YANG8, Jaruthat MILINDALEKHA S.1, Waranyu WONGSAREE9, Kamphol PROMJIRAPRAWAT1, Yod SUKAMONGKOL1, Prayat LEWAN1
1 Ramkhamhaeng University, Thailand, 2 National University of Malaysia, Malaysia, 3 Agency for Meteorology Climatology and Geophysics, Indonesia, 4 Ateneo de Manila University, Philippines, 5 Vietnam National University, Viet Nam, 6 Chulalongkorn University, Thailand, 7 Swedish Meteorological and Hydrological Institute, Sweden, 8 APEC Climate Center, South Korea, 9 King Mongkut’s University of Technology North Bangkok, Thailand
#Corresponding author: jerasorn@ru.ac.th +Presenter

This paper describes the performance of ensemble mean of multi-model simulations of the Southeast Asia Regional Climate Downscaling (SEACLID)/CORDEX Southeast Asia over Thailand during the historical period and also the future projections of near term, middle of century and end of the 21st century for the emission scenarios of RCP4.5 and RCP8.5 for wet months (June, July, August and September) and dry months (December, January, February and March). The SEACLID/CORDEX Southeast Asia multi-model simulations considered in this study comprises of eight GCMs (CNRM-CM5, HadGEM2-AO, MPI-ESM-MR, EC-Earth, CSIRO Mk3-6-0, IPSL-CM5A-LR, GFDL-ESM2M, HadGEM-2ES) and 3 RCMs (RegCM4, RCA4 and WRF3.5). Based on the comparison of station-averaged rainfall over the nine sub-regions and those of APHRODITE, CRU, TRMM and GPCC, it was found that the GPCC was a much better product for the modelled output to be compared with. The subsequent comparison of modeled ensemble mean precipitation during both wet and dry months with those of the GPCC during the historical period indicated reasonable performance with slight wet biases in some areas and dry in others. For future projections, almost entire region of Thailand is expected to experience an increase of mean rainfall by 20 – 40% from baseline period (1976 – 2005) during dry months of early century (2011 – 2040) except the southern region for RCP4.5. However, for middle (2041 – 2070) and end of 21st (2071 – 2100) century, drying condition (by 10 – more than 40%) is projected, except the northern and central region during March. However, during the dry months of January and December of RCP8.5, mean rainfall is projected to increase by 10 to > 40% over Thailand throughout the 21st century except in the southern region. However, during February and March, drying trend is indicated in the southern and eastern regions during middle and end of the century.

6.
AS31-D5-AM1-335-005 (AS31-A002)
 
High Resolution Climate Downscaling Over Southeast Asia Using WRF
Srivatsan RAGHAVAN#+, Jina HUR, Ngoc Son NGUYEN, Jiandong LIU, Shie-Yui LIONG
National University of Singapore, Singapore
#Corresponding author: tmsvs@nus.edu.sg +Presenter

In the light of climate change studies over Southeast Asia, this study describes recent high resolution regional climate modelling performed over Southeast Asia at a spatial resolution of 20 km. The study downscaled some of the CMIP5 GCMs under the climate change scenarios RCP 4.5 and 8.5. The study describes some evaluation of the WRF model's performance over the region driven by the reanalyses data and compares the results against gridded observations. The talk also provides assessments on the climate changes in key climate variables temperature and precipitation over Southeast Asia in the future.

7.
AS31-D5-AM1-335-006 (AS31-A010)
 
Detecting Tropical Cyclones in Regional Climate Model Simulations Over the CORDEX-Southeast Asia Domain
Jennifer TIBAY1,2+, Gemma NARISMA1,2#, Faye Abigail CRUZ2, Rochelle CORONEL3, Emil GOZO2, Tan Van PHAN4, Fredolin T. TANGANG5,6
1 Ateneo de Manila University, Philippines, 2 Manila Observatory, Philippines, 3 Ateneo de Davao University, Philippines, 4 Vietnam National University, Viet Nam, 5 National University of Malaysia, Malaysia, 6 Ramkhamhaeng University, Thailand
#Corresponding author: narisma@observatory.ph +Presenter

The study analyzes the capability of the downscaled simulations of the Southeast Asia Regional Climate Downscaling / Coordinated Regional Climate Downscaling Experiment – Southeast Asia (SEACLID/CORDEX-SEA) in representing tropical cyclone (TC) climatology, in terms of intensity, track, and frequency. A modified vortex tracking algorithm based on the methodology of Phan et al. (2015) is used as the detection method to detect TCs in hindcast simulations of SEACLID/CORDEX-SEA from the period of 1986 to 2005. The detection method examines a wide range of criteria in detecting TCs: vorticity, outer core wind strength, sea level pressure anomaly and temperature anomaly from four pressure levels (300-, 500-, 700-, and 850 hPa). Results are validated using the best tracks of the Joint Typhoon Warning Center (JTWC) from 1986 to 2005. Based from the preliminary results, the model simulations underestimated the total number of TCs and the average TC days for the said period but it captured the annual variation of the total number of TCs. The physical processes and typhoon dynamics are also analyzed further to understand the success or failure of capturing tropical cyclones characteristics in the regional climate model. This study is a good first step in efforts to help understand and consequently mitigate TC-related disasters for regions in SEA.

8.
AS31-D5-AM1-335-007 (AS31-A020)
 
Future Changes of Precipitation Extremes in Southeast Asia as Simulated in Cordex-Sea Models
Supari SUPARI1#+, Fredolin T. TANGANG2,3, Ju Neng LIEW2, Jerasron SANTISIRISOMBOON3, Patama SINGHRUCK4, Tan Van PHAN5, Thanh NGO-DUC5, Faye Abigail CRUZ6, Gemma NARISMA6,7, Edvin ALDRIAN1, Dodo GUNAWAN1, Grigory NIKULIN8, Hongwei YANG9
1 Agency for Meteorology Climatology and Geophysics, Indonesia, 2 National University of Malaysia, Malaysia, 3 Ramkhamhaeng University, Thailand, 4 Chulalongkorn University, Thailand, 5 Vietnam National University, Viet Nam, 6 Manila Observatory, Philippines, 7 Ateneo de Manila University, Philippines, 8 Swedish Meteorological and Hydrological Institute, Sweden, 9 APEC Climate Center, South Korea
#Corresponding author: supari.bmg@gmail.com +Presenter

The possible changes of precipitation extremes under warming environment is investigated over Southeast Asia Region using the output of the Coordinated Regional-climate Downscaling Experiment for Southeast Asia (CORDEX-SEA) project. In total, this exercise involved eight different CMIP5 global climate models and three regional climate models (RegCM4, RCA4 and WRF). Four indicators were used to express the precipitation extremes i.e. the annual rainfall total (PRCPTOT), consecutive dry days (CDD), frequency of extremely heavy rainfall (R50mm) and annual maxima of daily rainfall (RX1day). We analyzed the changes by comparing three 20-year period (2016-2035 as early-century; 2046-2065 as mid-century and 2081-2100 as end-century) with respect to reference period (1986-2005) under two the representative concentration pathways (RCP4.5 and RCP8.5). The ensemble mean was generally able to simulate the observation realistically. However, high variability across the model was observed. In general, we found changes in the end-century are more significant and more intensified than those in early and mid-century. The decrease in annual PRCPTOT is projected for all periods over Southeast Asia region, except for Myanmar and Northern Thailand with magnitude of 1-20% (1-30%) under RCP4.5 (RCP8.5) scenario. The CDD may increase in the future and become much longer in the end of century, up to 30% in RCP4.5 and 60% in RCP8.5, particularly over Maritime Continent. The positive changes are also dominant feature from R50mm projection indicating a higher frequency of daily extreme rainfall in the future. The extreme intensity (RX1day) is projected to increase in all periods with magnitude 1-30% (1-60%) for RCP4.5 (RCP8.5). Overall, we found that future climate of Southeast Asia are projected to have longer dry spell (CDD) accompanied by increasing frequency and intensity of extremes (R50mm and RX1day) and hence suggesting an intensification of both dry and wet season.

AS31 - Regional Climate Downscaling and CORDEX: Challenges and Prospects
Friday, August 11, 2017 | 335 | 11:00-12:30
1.
AS31-D5-AM2-335-008 (AS31-A021)
 
Performance Of RegCM4 Over Major River Basins in China
Xuejie GAO#+
Chinese Academy of Sciences, China
#Corresponding author: gaoxj@cma.gov.cn +Presenter

A long term simulation for the period of 1990–2010 is conducted with the latest version of the International Centre for Theoretical Physics (ICTP) regional climate model (RegCM4) driven by ERA-Interim boundary conditions at a grid spacing of 25km. The Community Land Model (CLM) is used to describe land surface processes, with updates in the surface parameters, including the land cover and surface emissivity. The simulation is compared against observations to evaluate the model performance in reproducing the present day climatology and interannual variability over the 10 main river basins in China, with focus on surface air temperature and precipitation. Temperature and precipitation from the ERA-Interim reanalysis are also considered in the model assessment. Results show that the model reproduces the present day climatology over China and its main river basins, with better performances in June-July-August (JJA) compared to December-January-February (DJF). In DJF we find a warm bias at high latitudes, underestimated precipitation in the south and overestimated in the north. The model in general captures the observed interannual variability, with greater skill for temperature. We also find an underestimation of heavy precipitation events in eastern China, and an underestimation of consecutive dry days in northern China and the Tibetan Plateau. Similar biases for both mean climatology and extremes are found in the ERA-Interim reanalysis, indicating the difficulties for climate models in simulating extreme monsoon climate events over East Asia.

2.
AS31-D5-AM2-335-009 (AS31-A005)
 
Dynamic Downscaling of Current Climate (1981-2005) Over CORDEX East Asia Phase 2 Domain Using RegCM4.0
Seok-Geun OH+, Myoung-Seok SUH#
Kongju National University, South Korea
#Corresponding author: sms416@kongju.ac.kr +Presenter

We conducted dynamic downscaling using the RegCM4.0 with 25 km of horizontal resolution over CORDEX-East Asia phase 2 domain for the current climate (1981-2005) and evaluated its performance using various reference dataset. The HadGEM2-AO with about 110 km provided by the Korea Meteorological Administration (KMA) was used as the forcing data of RegCM4.0. The RegCM4.0 generally well simulates the spatial characteristics of temperature and precipitation by geographical and topographic conditions, compared with HadGEM2-AO. In particular, the warm biases in Mongolia, northern China, and Russia during summer and cold biases in Tibetan Plateau, Mongolia, northeast China, and northern India during winter were reduced. However, the systematic wet (dry) biases pattern in the most of model domain (South Korea) in summer precipitation were still remained. It is associated with southward shifted low level jet caused by the weakened North Western Pacific High of HadGEM2-AO. In South Korea, the RegCM4.0 shows a better performance than HadGEM2-AO in terms of the magnitude and spatial variability of both temperature and precipitation. In particular, the RegCM4.0 (12.3%) shows a better performance in simulating the ratio of extreme precipitation over 100 mm/day to total precipitation than HadGEM2-AO (3.2%), compared with KMA observation (19.6%). Also, the RegCM4 reasonably reproduced the extreme climate events (e.g., the number, interannual variability, and trends of heavy rainfall, frost day, and tropical night) over South Korea compared to the HadGEM2-AO.

3.
AS31-D5-AM2-335-010 (AS31-A009)
 
Comparison of Regional Climate Simulations from Three Different Horizontal Resolution Using the HadGEM3-RA
Hyun-Suk KANG#+, Song-Yee HONG
Korea Meteorological Administration, South Korea
#Corresponding author: hyunsuk306.kang@gmail.com +Presenter

Under the CORDEX framework, the horizontal resolution has been recommended as 50 km in world-wide CORDEX domains except for a few regions, which are Europe, Southeast Asia, and East Asia. It was also set up as 50 km for East Asia domain in the CORDEX Phase 1, however; its resolution has been examined more than decades in this domain, so that the standard resolution for the East Asia domain has been increased to 0.22 degrees, approximately 25 km, in the CORDEX Phase 2. Because the orographic forcing is one of the most major factors to produce added values in dynamical downscaling, East Asia domain might be the most appropriate region to investigate the impacts of horizontal resolution in regional climate simulations because it covers the highest Plateau and complex topography in the world. In this context, we conducted long-term integration with the HadGEM3-RA driven by ERA-interim reanalysis data for the three different horizontal resolutions, that are, 0.44, 0.22, and 0.11 degrees, respectively. When we compared the model results with the APHRODITE gridded-observation, in general, both the precipitation and surface air temperature show better performance in medium (0.22 deg) than in low (0.44 deg) resolution’s simulation, but those from high (0.11 deg) resolution show worse performance in terms of domain average. We need to note the limitation of resolution of gridded-observation and its uncertainties as well. Further investigation on added values from high-resolution regional climate simulation is on-going by using in-situ measurements and satellite observation. Results will be discussed in the presentation.

4.
AS31-D5-AM2-335-011 (AS31-A040)
 
Climate Change Projection Over East Asia and the Korean Peninsula
Dong-Hyun CHA1#+, Gayoung KIM1, Dong-Kyou LEE2,3, Myoung-Seok SUH4, Joong-Bae AHN5, Seung-Ki MIN6, Song-You HONG7, Hyun-Suk KANG3
1 Ulsan National Institute of Science and Technology, South Korea, 2 Seoul National University, South Korea, 3 Korea Meteorological Administration, South Korea, 4 Kongju National University, South Korea, 5 Pusan National University, South Korea, 6 Pohang University of Science and Technology, South Korea, 7 Yonsei University, South Korea
#Corresponding author: dhcha@unist.ac.kr +Presenter

To estimate regional climate change over East Asia, global climate model results by the HadGEM2-AO are dynamically downscaled using 5 RCMs, which have two different horizontal resolutions (50km and 12.5km). In general, RCMs with higher resolution more reasonably capture the spatial distribution of precipitation over the Korean Peninsula compared to those with lower resolution. In particular, large precipitation regions related to complex mountain ranges are well simulated due to detailed topography in RCMs with higher resolution. The difference between RCMs with dissimilar resolutions is relatively robust in summer compared to other seasons indicating that higher resolution and detailed topography lead to more realistic simulation of large precipitation in summer related to mesoscale phenomena.

Changes in extreme precipitation indices over South Korea and changes in typhoon over the western North Pacific are also analyzed based on simulation results by 5 RCMs. Differences in extreme precipitation between 25-year (1981-2005) historical experiment and 30-year (2071-2100) RCP 8.5 experiment are compared. In late 21C, both precipitation intensities and a maximum number of consecutive dry days tend to increase. This indicates that heavy precipitation as well as drought could more frequently occur in the future climate compared in the present climate. Particularly, the occurrence of heavy precipitation more prominently increases in spring and winter, while that of drought more robustly increases in autumn. These changes in extreme precipitation are associated with the changes in low-level moisture and monsoon circulation. The tracks of typhoons tend to expand northward in the future, indicating that mid-latitude region such as Korea and Japan will be more frequently affected by typhoons. The reason for the northward expansion of typhoon tracks in the future can be related to the weakened vertical wind shear, increasing sea surface temperature, and expanded subtropical high.

5.
AS31-D5-AM2-335-012 (AS31-A041)
 
Future Changes in Extreme Precipitation Over South Korea Using Multi-Regional Climate Models
Sera JO1#+, Joong-Bae AHN1, Myoung-Seok SUH2, Dong-Hyun CHA3, Dong-Kyou LEE4,5, Song-You HONG6, Seung-Ki MIN7, S.C. PARK5, Hyun-Suk KANG5
1 Pusan National University, South Korea, 2 Kongju National University, South Korea, 3 Ulsan National Institute of Science and Technology, South Korea, 4 Seoul National University, South Korea, 5 Korea Meteorological Administration, South Korea, 6 Yonsei University, South Korea, 7 Pohang University of Science and Technology, South Korea
#Corresponding author: seta43@pusan.ac.kr +Presenter

The change of extreme precipitation is assessed with the HadGEM2-AO - 5 Regional Climate Models (RCMs) chain, which is a national downscaling project undertaken cooperatively by several South Korean institutes aimed at producing regional climate change projection with fine resolution (12.5 km) around the Korean Peninsula. The downscaling domain, resolution and lateral boundary conditions are held the same among the 5 RCMs to minimize the uncertainties from model configuration. Climatological changes reveal a statistically significant increase in the mid-21st century (2046-2070; Fut1) and the late-21st century (2076-2100; Fut2) precipitation properties related to extreme precipitation, such as precipitation intensity and average of upper 5 percentile daily precipitation, with respect to the reference period (1981-2005). Changes depending on the intensity categories also present a clear trend of decreasing light rain and increasing heavy rain. In accordance with these results, the change of 1-in-50 year maximum precipitation intensity over South Korea is estimated by the GEV method. The result suggests that the 50-year return value (RV50) will change from −32.69% to 72.7% and from −31.6% to 96.32% in Fut1 and from −31.97% to 86.25% and from −19.45% to 134.88% in Fut2 under representative concentration pathway (RCP) 4.5 and 8.5 scenarios, respectively, at the 90% confidence level. This study suggests that multi-RCMs can be used to reduce uncertainties and assess the future change of extreme precipitation more reliably.

Acknowledgements

This work was funded by the Korea Meteorological Administration Research and Development Program under grant KMIPA 2015-2081

Reference

Ahn et al., 2016: Changes of Precipitation Extremes over South Korea Projected by the 5 RCMs under RCP Scenarios, Asia-Pac. J. Atmos. Sci., 52(2), 223-236

6.
AS31-D5-AM2-335-013 (AS31-A006)
 
Heat Waves in Taiwan: Western North Pacific Subtropical High and Climate Variability
Mien-Tze KUEH#+, Chuan-Yao LIN, Yin-Jui CHUANG, Yangfan SHENG, Yi-Yun CHIEN
Academia Sinica, Taiwan
#Corresponding author: kuehmt@gmail.com +Presenter

This study investigates the heat waves in Taiwan and the relevant mechanism based upon observations and dynamically downscaled simulations and future projection. The downscaling is performed using the Weather Research Forecasting (WRF) model with 5-km grid spacing, both recent past (1979-2003) and future (2075-2099) simulations are conducted. Taking the global datasets from NCEP/CFSR and ECHAM5 as boundary conditions, two sets of downscaled simulations are carried out respectively for the recent past period. The ECHAM5 model output under the A1B emissions scenario is used as the global driver for the downscaled future projection. A 95th percentile threshold is used for identifying hot extremes over a period of consecutive days. Heat waves are becoming more severe in the future projection. This future change is primarily a result of the shift in the mean of daily maximum temperature and not a result of change at higher moments. Apparent warming in daily minimum temperature suggests elevated heat stress in nighttime during future heat waves. Heat waves in Taiwan are associated with abnormal warming and drying atmospheric conditions under the control of enhanced western North Pacific subtropical high. The surrounding waters serve as vast moisture source to suppress the drying magnitude in surface layer as temperature rise, thereby ensuring a high humidity level during the hot spell. The associated warming and drying anomalies cover certain spatial extents, suggesting that the extreme situation identified here is not confined to just an island-wide hot spell, the abnormal hot weather can take place across a broad geographical areas.

AS31 - Regional Climate Downscaling and CORDEX: Challenges and Prospects
Friday, August 11, 2017 | 335 | 14:00-15:30
1.
AS31-D5-PM1-335-014 (AS31-A014)
 
Convection-Permitting Regional Climate Modelling of the Maritime Continent and the Impact of Urban Areas
Jason EVANS1#+, Daniel ARGUESO2, Alejandro DI LUCA1
1 University of New South Wales, Australia, 2 University of Hawaii, United States
#Corresponding author: jason.evans@unsw.edu.au +Presenter

The Maritime Continent has consistently been identified as a challenging region in terms of simulating precipitation. Its intricate configuration of islands with complex topography surrounded by a warm and shallow ocean makes this tropical archipelago an unequaled setting to test potential benefits of very high-resolution models. In this study, we focus on the western Maritime Continent to determine features of precipitation that are better represented with increased horizontal resolution, as well as those characteristics that deteriorate at finer grid spacing.

We investigated the impact of spatial resolution on rainfall amounts and diurnal cycle using the Weather Research and Forecasting model. A set of simulations running over a 5-year period at resolutions of 50, 10 and 2 km were completed and compared against satellite-derived observational products. While annual biases over the mountains are larger as resolution increases, our results suggest that precipitation is physically more realistic in the convection-permitting experiment performed at 2-km grid spacing. For example, the shape and phase of the diurnal cycle in the region, which are traditionally misrepresented in models, are substantially improved at higher resolution when comparing with the observational datasets. The amplitude of the diurnal cycle is also improved over most areas, although deficiencies still exist in that the strength of the cycle is overestimated.

The influence of cities on precipitation characteristics is quantified for two major urban nuclei in the region (Jakarta and Kuala Lumpur) and results indicate that their presence locally enhances precipitation by over 30 %. This increase is mainly due to an intensification of the diurnal cycle. Cities increase near surface temperature, generating instability. They also make land-sea temperature contrasts stronger, which enhances sea breeze circulations. Together, they increase near-surface moisture flux convergence and favour convective processes leading to an over-all increase of precipitation over urban areas.

2.
AS31-D5-PM1-335-015 (AS31-A024)
 
Future Changes in Extremely Heavy Winter Precipitation Around Japan Projected by Regional Climate Models
Hiroaki KAWASE1#+, Hidetaka SASAKI1, Akihiko MURATA2, Masaya NOSAKA1, Izuru TAKAYABU1, Rui ITO3, Takahiro SASAI4, Takeshi YAMAZAKI4, Shiori SUGIMOTO5
1 Japan Meteorological Agency, Japan, 2 Meteorological Research Institute / Japan Meteorological Agency, Japan, 3 National Research Institute for Earth Science and Disaster Resilience, Japan, 4 Tohoku University, Japan, 5 Japan Agency for Marine-Earth Science and Technology, Japan
#Corresponding author: hkawase@mri-jma.go.jp +Presenter

We performed large ensemble regional climate experiments to investigate future changes in extreme weather events using Non-Hydrostatic Regional Climate Model with 20 km (NHRCM20). The initial and lateral boundary conditions are derived from global climate projections using Meteorological Research Institute-Atmospheric General Circulation Model based on the past and future sea surface temperatures when global-mean surface air temperature rises 4 K.

The winter total snowfall decreases in the most parts of Japan, while the extremely heavy daily snowfall occurring less than once every ten years could increase at mountainous areas in the Central Japan. Composite analyses indicate that the extremely heavy snowfall occurs when the convergence zone appears over the Sea of Japan. Since the warmer ocean could supply more water vapor in the warmer future climate, the cumulus convections could become stronger around the convergence zone. We also compare these results with the CORDEX East Asia simulations with 20 km grid spacing.

The 20 km horizontal resolutions is, however, too coarse to simulate the regional climate around complex Japanese mountains. We conducted the dynamical downscaling with 5 km grid spacing, hereafter NHRCM05, from the NHRCM20 simulations. The NHRCM05 well simulates winter maximum and minimum temperature in the Central Japan. Analyzing the heavy snowfall events at some stations in the Central Japan, the heavy snowfall events are caused by winter monsoon, a convergence zone over the Sea of Japan, extra-tropical cyclone passing over Sea of Japan and Pacific Ocean, and their complex mechanisms.

3.
AS31-D5-PM1-335-016 (AS31-A013)
 
Projection of Heavy Precipitation Over Japan in Ensemble Simulations with a Convection-Permitting Regional Climate Model
Akihiko MURATA1#+, Hidetaka SASAKI2, Hiroaki KAWASE2, Masaya NOSAKA2, Toshinori AOYAGI2, Mitsuo OH'IZUMI3
1 Meteorological Research Institute / Japan Meteorological Agency, Japan, 2 Japan Meteorological Agency, Japan, 3 Meteorological College, Japan
#Corresponding author: amurata@mri-jma.go.jp +Presenter

Future changes in heavy precipitation over Japan by the end of the 21st century (from 2076 to 2096) under the RCP8.5 scenario were projected by a convection-permitting regional climate model, called the non-hydrostatic regional climate model, with a grid spacing of 2 km, hereafter referred to as NHRCM02.

The performance of NHRCM02 in heavy precipitation in the present climate (from 1980 to 2000) was first evaluated based on observations. The 99th percentile of hourly precipitation in the period of a year was averaged over 20 years and was used as an index of heavy precipitation. The results were compared with those for the driving model, hereafter referred to as NHRCM05, which has a grid spacing of 5 km and includes the Kain-Fritsch convective parameterization.

The magnitudes of root mean square error (RMSE) and systematic error (bias) in the index of heavy precipitation averaged over Japan simulated by NHRCM02 were less than those obtained from the NHRCM05 simulation, indicating that model performance was improved by using a higher resolution model. Although difference in the magnitude of bias in the index between NHRCM02 and NHRCM05 was not statistically significant at the 5% level, difference in RMSE between the two simulations was statistically significant.

The projected future climate showed robust increases in the index of heavy precipitation over the northern regions of Japan although the index averaged over the whole area of Japan did not show robust changes. Uncertainties in the projected heavy precipitation were evaluated with the results obtained from ensemble simulations, consisting of four ensemble members, using NHRCM02. At least three out of four members showed statistically significant increases in the index of heavy precipitation over the northern regions of Japan, whereas one member or less indicated statistically significant changes in other regions.

4.
AS31-D5-PM1-335-017 (AS31-A039)
 
Statistical Versus Dynamical Downscaling in the Tropics: What are the Challenges?
Bertrand TIMBAL#+
National Environment Agency, Singapore
#Corresponding author: bertrand_timbal@nea.gov.sg +Presenter

The need to develop downscaling approaches to capture small-scale regional climate features of interest for climate impact and adaptation studies is well understood. The due process to develop, evaluate and establish the added value of the various technical option available to deliver on this challenge is not necessarily as well understood. As a cornerstone, resides the paradigm that small-scale climate features can be driven by large-scale forcings; the applicability of that paradigm to the Tropics is what we are discussing here. It requires some specific soul searching when considering that in general downscaling techniques have their conceptual roots and original applications in mid-latitude climate regimes. As climate is by definition the emergence of statistical properties from daily weather situations is it commonly accepted that local climate feature can either be obtained by averaging high resolution simulations of the daily weather (e.g. Regional Climate Model or dynamical downscaling) or by bypassing the physical resolution of the primitive equations and focus on the statistical properties of the local climate which can be captured by large-scale properties (e.g. transfer function between predictors and predictands or statistical downscaling). In this talk we will review the advantages and disadvantages of various approaches when applied to the Tropics.

5.
AS31-D5-PM1-335-018 (AS31-A019)
 
Monthly Bias Correction of Simulated Historical and Projected Daily Precipitation and Temperature in the Philippines
Shane Marie VISAGA1+, Emilio GOZO1, Rochelle CORONEL2, Faye Abigail CRUZ1, Gemma NARISMA1,3#
1 Manila Observatory, Philippines, 2 Ateneo de Davao University, Philippines, 3 Ateneo de Manila University, Philippines
#Corresponding author: narisma@observatory.ph +Presenter

Despite the advances in climate models, biases present in hydro-meteorological output limit the applications of the model result especially in impact studies. With available observation data, bias correction can reduce the biases of the model by matching its statistical distribution with that of the observed. This study aims to a) assess the performance of monthly bias correction in capturing the seasonality of temperature and precipitation in the observed data for four climate types in the Philippines, b) establish the reliability of the method to correct projections and c.) define the conditions on which the method is recommended.

Bias correction at a monthly scale is applied to multi-model downscaled climate output using the 25 km- gridded historical observation dataset APHRODITE (Asian Precipitation – Highly- Resolved Observational Data Integration Towards Evaluation). Since monthly correction is highly dependent on the reliability of the dataset used to correct the simulated data, APHRODITE is first validated with station data from PAGASA (Philippine Atmospheric Geophysical and Astronomical Services Administration). Transfer functions are then derived using 1971-1990 observed and simulated data and then applied to 1991-2000 for evaluation. Initial validation of the transfer functions with the 1991-2000 simulations show correspondence between the observed and corrected model output in terms of magnitude and seasonality. Thus, the 1971-1990 transfer function will also be applied for the 2011-2065 projection data. The performance of monthly correction per climate type will be further investigated to potentially establish a set of conditions (e.g. baseline period length, climate type, and location) on which the bias correction method performs best in the Philippines.

6.
AS31-D5-PM1-335-019 (AS31-A033)
 
Evaluation and Comparison of Multi Agro-Meteorological Elements Between Regression-Based Statistical Downscaling and Dynamical Downscaling Results Over Japan
Motoki NISHIMORI#+, Nobuhiko ENDO
National Agriculture and Food Research Organization, Japan
#Corresponding author: mnishi@affrc.go.jp +Presenter

In this study, a multivariate multiple linear regression (MMLR) -based empirical statistical downscaling (ESD) method that comprehensively analyzed for seven surface predictands, daily averaged, maximum and minimum temperatures (TM, TX and TN), precipitation (PR), solar radiation (SR), relative humidity (RH) and wind speed (WS), was applied over Japan by using atmospheric circulation factors derived by reanalysis dataset as predictors. The characteristics of this study are, first, to include not only major climate elements (TM and PR) but also other agro-meteorological ones such as SR, RH and WS for input to agricultural (crop) models. Then, this experiment are basically operated in accordance with the CORDEX-ESD protocol- 2014 to set various calibration and validation periods. 

The linearly-estimated data applied by this ESD method are further adjusted to have the same variance as observed climate (scaling method). The scaling method is, however, insufficient for the bias correction of PR, because weak rainfall tended to drizzle in the linear regression method. This feature was associated with significant overestimation of precipitation and also caused underestimated SR. Here, additional bias correction techniques, adjusting the number of the rainy days and different linear regression equations to explain the anomaly of the predictands in wet and dry days respectively, were both developed. Thus, the physical interrelationships among these elements should be considered, for example, to improve the underestimated SR in the Baiu (early summer rain) season over the region along with the Sea of Japan. 

The ESD-estimated current climate were compared with those of the regional climate models (RCMs) output driven by the same boundary conditions. Our ESD output obtained the good estimation with observed climate relative to the RCMs. It was also found that the RCMs-derived SR tended to overestimate though that of TM was mostly coincided with the observed value.