Investigation of air quality over the largest city in central China using high resolution satellite derived aerosol optical depth data

Urban air pollution in China has gained unprecedented attention under the background of high concentration of particulate matter and increasing haze frequency in recent years. In this study, utilizing the high resolution Aerosol Optical Depth (AOD) dataset derived from Gaofen-1 (GF-1) satellite during 2013-2016, we provide a new insight into the air quality over Wuhan, the largest city in central China. Local AOD (LAOD) was introduced to indicate the aerosol loading from local sources. Annual LAOD was found to increase with urban cover in the district scale, which revealed the potential positive feedback between urbanization and regional air pollution. The seasonal pattern of LAOD was consistent with PM2.5, both presenting a seasonality of highest in winter and lowest in summer. By locating the highly polluted regions from LAOD map, our research highlighted the impact of anthropogenic aerosol loading (especially from industrial parks) on the regional air quality. Noticing the concentrated distribution of anthropogenic aerosol loading over urban areas, we further defined the urban-induced AOD to quantify the urban aerosol effect by comparing LAOD between urban areas and other land types. Consistent with the change trend of PM2.5, annual urban-induced AOD also presented a slight downward trend, which was a reasonable response to the stricter environment policies adopted by local government in recent years. Though carried out as a case study over Wuhan in central China, we believe that the findings presented here would promote the understanding of air pollution in most mega cities of China.