The possible impact of atmospheric aerosol and other factors on lightning over the rugged terrain of Nepal

Abstract

Electrification of thunderclouds and lightning initiation from within the cloud remain the mysteries among scientists and researchers. Meteorological and atmospheric factors that play a vital role in generating thunderstorms over the mountainous terrain of Nepal further add ambiguity. Atmospheric aerosol contents and Convective Available Potential Energy (CAPE) are believed to play major roles in generating thunderstorms. In this study, thunderstorm activities over the mountainous country Nepal have been investigated in association with Aerosol Optical Depth (AOD) and the CAPE for six years between 2015 to 2020. Lightning stroke density was used to measure thunderstorm activity and their possible association with atmospheric aerosol, and CAPE. For the investigation, we chose the pre-monsoon period that begins in March and ends in June, because thunderstorm activities are prevalent during this period. Our preliminary investigation shows that atmospheric aerosol plays a significant role in generating thunderstorms, and those thunderstorm activities significantly dropped in the year 2020, corresponding to the reduction in the value of Aerosol Optical Depth (AOD). However, AOD alone does not play a pivotal role in thunderstorm activities. The correlation coefficient of average AOD with that of stroke density was about 0.57 exhibiting a weak correlation in March. Similarly, CAPE has also been found to play a significant role for thunderstorm activities. Its correlation coefficient with stroke density is found to be about 0.59 during the pre-monsoon exhibiting a weak correlation in the month of March and exhibits highest correlation during the Month of April, 2015 as compared to the other months. Although CAPE and Aerosol play significant roles in generating thunderstorms, they alone are not the determiner and that other climatic factors should also be considered.