Effects of aerosols on diurnal variation of lightning activity in the Sichuan Basin, China

Aerosols can affect the lightning activity through radiative and microphysical effects. This study attempts to reveal the distinct impact pathways of these two effects on lightning activity. Using data of cloud-to-ground (CG) lightning, aerosol optical depth (AOD), thermodynamic, and cloud-related variables during the summer (June, July, and August) of 2010-2018 in the Sichuan Basin, we investigate the changes in the diurnal variation of lightning activity characteristics between polluted (2010-2013) and clean (2015-2018) years. Polluted years exhibit more thunderstorms during the late afternoon and early evening hours than clean years, but show no significant differences in other time periods. During all time periods, thunderstorms in polluted years are more intense, with a higher CG lightning density. Aerosols exhibit more intense radiative effect during afternoon and early evening hours in polluted years, which reduces the surface temperature, thereby enhancing atmospheric stability and inhibiting the formation of convection. The cloud liquid water and cloud ice water content in polluted years are higher, suggesting stronger aerosol microphysical effects. These results indicate that the radiative effect of aerosols primarily influences lightning activity by altering the frequency of thunderstorms, whereas the microphysical effect of aerosols predominantly affects lightning activity by modulating the intensity of thunderstorms.