Studying the Impacts of Future Climate and Emission Changes on Air Quality in China Using the Two-Way Coupled WRF-CMAQ

Air quality in China is of great concern especially for its impacts on public health, atmospheric environment, and regional and global climate. However, predicting future air quality is challenging due to changing climate and emissions as well as their complex interactions. The Community Earth System Model (CESM) with advanced chemistry and aerosol treatments (hereafter CESM-NCSU), has been recently applied for decadal global climate predictions and air quality simulations under the representative concentration pathways (RCPs). Such simulations were performed at a grid resolution of 0.9° × 1.25° that may not resolve well mesoscale features over a regional domain of interest. In this study, we investigate the impacts of projected climate and emission changes on air quality in China around 2050 under the RCP4.5 scenario at a spatial resolution of 36 km by using the two-way coupled Weather Research and Forecasting - Community Multiscale Air Quality (WRF-CMAQ) modeling system (hereafter WRF-CMAQ). Both meteorological downscaling and chemical dynamical downscaling are applied to fully take an advantage of global climate-chemistry models that can predict well large-scale global changes and regional models that can better represent regional phenomena. CESM-NCSU outputs at every 6 hours are used to provide initial and boundary conditions (ICs and BCs) for WRF-CMAQ simulations. The emission scenarios of air pollutants over China are developed to consider possible stringent control measures from regional air quality control perspectives. Simulations of regional air quality over East Asia during current years (2006-2010) and future years (2046-2050) will be conducted at a horizontal grid resolution of 36-km to examine the impacts of simulated future climate and emission projections on air quality (i.e., PM2.5 and O3 concentrations) over China. Current meteorological and chemical predictions will be evaluated against observations from surface networks and satellites to assess the model's performance. Future climate and emission changes will be assessed. Their impacts on China's air quality will be examined separately and together through sensitivity simulations. This study will provide valuable insights into long-term changes in climate and air quality in China.