Effects of Aerosols on lightning activity over the Himalayan Region

Abstract

This study attempts to obtain the correlation between lightning activities and aerosol optical depth over the Himalayan and lesser Himalayan region. To investigate the association between Aerosol Optical Depth (AOD) with Lightning Stroke Density (LSD), the lightning stroke data were obtained from Vaisala’s Global Lightning Detection Network (GLD 360), and Aerosol Optical Depth (AOD) data were obtained from the Moderate Resolution Imaging Spectrometer (MODIS) Aqua satellites acquired between 2015 and 2020. We divided the geography of Nepal into three sections namely, Eastern (region 1), Central (region 2), and Western (region 3). It is observed that lightning is strongly and positively correlated with AOD loading, up to AOD ~ 0.75 for the eastern region; up to AOD ~ 0.70 for the middle region; and up to ~ 0.55 and for the western region; above these values the correlation weakens. Region 2 exhibits a much weak linear correlation (R=0.628) as compared to the other two regions (R=0.855 for region 1 and R=0.832 for region 3). The results indicate that moist aerosols have a better correlation to greater optical depth as compared to the drier aerosols over the Himalayan region. Lightning activity is strongly correlated with AOD for lower values but there is a negative correlation for the higher values of AOD.