Modeling tropospheric ozone formation over East China in springtime

In this study, we investigate the springtime O₃ formation over East China (April 2008) using the Weather Research and Forecasting Model with Chemistry (WRF/Chem). A simple process analysis scheme is added to WRF/Chem, which could calculate the contributions of photochemical and physical processes to O₃ formation. WRF/Chem calculates the hourly 3-D O₃ mixing ratios, photochemical O₃ production rates (CPR) and physical processes contribution rates (PCR) on a two nested domain system, with inner domain focusing on East China. Model evaluation shows that the modeled results agree relatively well with the observations. On the ground level, the high O₃ mixing ratios (>45 ppbv) are located over Fujian and Jiangxi provinces. The O₃ levels over the Yangtze River Delta (YRD) and northern Jiangsu are low (<30 ppbv). The distribution patterns of CPR and PCR over East China reveal that the high O₃ mixing ratios over Jiangxi and Fujian are caused by both local photochemical generation and regional transport, while the O₃ concentrations over the YRD region are transported and diffused from surrounding areas. In addition, the contributions of biogenic and anthropogenic emissions as well as the regional transport from domain’s upstream regions are discussed. On average, the biogenic and anthropogenic emissions account for 2.6 and 4.5 ppbv of daytime mean O₃ mixing ratios in East China, respectively.