Investigations Of Aerosol Feedback Effects Over The Eastern Region Of China Using Multiple Two-way Coupled Meteorology And Air Quality Models

Atmospheric aerosols can affect the Earth's energy budget and meteorological variables through aerosol radiation interaction(ARI)and aerosol cloud interaction(ACI),and in turn impact the formation,transport and dispersion processes of air pollutants.This two-way feedback between air pollution and meteorology is critical for the research and prediction of air quality and also future climate change.In recent years,China has implemented a series of nationwide pollution emission control strategies to improve air quality and environment,yet the combined fine particulate matter(PM_2.5)and ozone pollution problem remains serious in the Eastern region of China.Therefore,the ecological environment monitoring centers at the provincial and some cities'level have deployed air quality prediction and early warning systems.However,the accuracies of air quality models used in these systems sometimes are not satisfactory that may curb the ability of government agencies to make rational and timely decisions to control air pollution,especially under severe pollution conditions.Prior research studies have indicated that coupling meteorology and air quality in models and turning on the two-way feedback in them can improve models'performance under certain circumstances.In order to answer the following questions:(1)whether the coupled model with aerosol feedbacks can improve regional air quality prediction and enhance the early warning capability;(2)to what extent the aerosol feedback effects influence meteorology and air quality in the Eastern region of China,this Ph.D.dissertation describes the research work aiming at the application and evaluation of two-way coupled meteorology-air quality models for the Eastern region of China during the year2017.The modeling studies focus on(1)evaluating meteorology and air quality variables simulated by the three open source and widely used two-way coupled models((WRF-CMAQ,WRF-Chem and WRF-CHIMERE)by comparisons with surface and satellite observations;(2)quantifying the impacts of aerosol feedback on meteorology and air quality;(3)performing case studies of three typical air pollution episodes utilizing the two-way coupled models.The main conclusions are:(1)comparing to observations,the three two-way coupled models simulated meteorology and air quality variables reasonably well in the Eastern region of China during 2017 and the WRF-CMAQ model displayed the best overall performance;(2)the accuracies of model simulations by the three models with/out feedbacks varied with the simulation period,sub-areas in the model domain,and meteorological and air quality variables;(3)the feedback involving ARI and ACI generally decreased near-surface(vertical)shortwave radiation,temperature,mixing ratio,wind speed,PBL height and O₃(low-level relative humidity and PM_2.5)and increased relative humidity and PM_2.5(low-level temperature,mixing ratio,wind speed and O₃);(4)WRF-CMAQ with ARI,among the three two-way coupled models,well captured the features of three typical pollution episodes occurring in the Eastern region of China during 2017 and utilizing the GSI data assimilation methodology in WRF-CMAQ could further improve the model results under a winter haze condition.This Ph.D.research work attempts to shed light on the application and evaluation of two-way coupled meteorology-air quality models in the Eastern region of China for possible enhancement of current operational air quality forecasting and warning systems.Hence,in the future,to effectively improve these systems'ability to help government agencies with better strategies for controlling air pollution and protecting human health,deploying surface observational data assimilation schemes in models is recommended.Then,when sufficient computational resources become available,current offline air quality models can be upgraded to two-way coupled models with aerosol feedbacks.