An aerosol air pollution episode affected by binary typhoons in east and central China

Previous studies have suggested that pollutant concentrations have the characteristics of initially rising and later falling in the main impact area of a typhoon. Whether this occurs in the typhoon's periphery or in zones even further away is still unknown. Based on ground observations of pollutant concentrations, meteorological parameters, aerosol optical depth, and WRF-Chem simulation, an aerosol air pollution episode affected by binary typhoons were analyzed over different regions in inland China. Before the typhoons made landfall, the weak surface winds and downdrafts were the crucial factors triggering the severe aerosol air pollution in east and central China. After landing, in the main impact area, aerosols were effectively removed due to precipitation scavenging and strong winds. However, beyond that area, the impact of the typhoons on pollution weakened with the increasing distance. Wuhan was at the edge of the typhoon impact zone, the changes of pollutant concentrations were similar to the main impact area, but the pollutants dispersed only due to the gales. Weinan site was farthest away from the typhoons, typhoons hardly affected the air quality. The results provide a scientific basis for understanding the mechanism between binary typhoons and aerosol air pollution and enable more accurate pollution alerts to be made during typhoons.