PM2.5 in the Heavy Haze regions over China: Simulations and Observations

The Beijing-Tianjin-Hebei (BTH) and Yangtze River Delta (YRD) are the two of most heavy haze regions in China due to rapid development of economy and the higher population density. The PM2.5 mass concentrations for the time period of April 15, 2014 to March 31, 2015 simulated by using WRF-Chem are compared with observational data from national air quality monitoring sites managed by the Chinese Environmental Protection Bureau. The discrepancies of PM2.5 mass concentrations between simulations and observations over 2 regions are analyzed. We also explored both meteorological conditions and aerosol physical and chemical processes in order to explain the discrepancies, and possible reasons for the different PM2.5 situations in two regions.