Potential impacts of aerosol on diurnal variation of precipitation in autumn over the Sichuan Basin, China

This study investigates the autumn precipitation in Sichuan Basin (SB), China in combination with reanalysis datasets of aerosol and meteorological fields from 2008 to 2018. To identify the aerosol impacts on precipitation, we carefully selected and divided the data into multiple groups according to vorticity, precipitation amount category, aerosol pollution level and the geopotential height in the upper troposphere. Our data shows that the precipitation in SB are generally reduced and weakened in afternoon to evening, but enhanced and intensified after mid-night under the aerosol polluted condition. By analysing data contrasts between different groups, we find that aerosol pollution in SB reduces shortwave heating near surface, which enhances the tropospheric stability and inhibits the vertical motion and rainfall in the afternoon to early evening. As the stability reduces within the basin, the vertical motions are invigorated to enhance and intensify the rain after mid-night. Therefore, we conclude that the aerosol pollution in SB and the rapid adjustment of aerosol-radiation interaction amplify the diurnal features of precipitation in autumn.