Impact of aerosols on atmospheric electrification over East and West Africa

Abstract

Studies have shown that atmospheric aerosols can modify cloud microphysics . The influence of atmospheric aerosols on mechanisms that lead to generation of lightning is very complex and not fully understood. Recent studies have also revealed that, west Africa has high concentration of atmospheric aerosols due to localized wind which diverge from Sahara desert to this area. This study investigates the impact of atmospheric aerosols on lightning flash rate over east and west Africa by utilizing aerosol optical depth (AOD) from Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) reanalysis data, convective available potential energy (CAPE), potential temperature, surface relative humidity, clouds and lightning flash rate. Pearson correlation and partial correlation have been applied between lightning flash rate and AOD, humidity, clouds, CAPE as well as potential temperature. Quantitative results show that there is a strong positive correlation ( ∼ 0.75) between lightning flash rate and aerosols under low concentration of aerosols (AOD ≤ 0.6) due to aerosol microphysics effect. In the presence of high aerosol concentration (AOD > 0.6), the correlation coefficient between lightning flash rate and aerosols is somehow weak ( ∼ 0.45) due to decrease in the number of ice particles as well as radiation effect of aerosols. However, the correlation coefficient between lightning flash rate and CAPE, clouds and potential temperature are all positive under both high and low concentration of atmospheric aerosols. • Atmospheric aerosols modify cloud microphysics. • There is strong positive correlation between lightning flash rate and aerosols due to aerosol microphysics effect. • The weak correlation between lightning flash rate and aerosols is due to aerosol radiation effect.