Assessment of lightning climatology and trends over eastern India and its association with AOD and other meteorological parameters

Lightning is one of the most spectacular and dangerous atmospheric phenomena that can cause serious risks to human life and property. The microphysical and radiative effects of atmospheric aerosols help to form and suppress convective clouds, respectively, which cause lightning activities. The present study has been undertaken to analyse the climatology and trends of lightning flash rate density (FRD) and aerosol optical depth (AOD) and assess the association of FRD with AOD and other meteorological parameters over eastern India, one of the lightning-prone zones in India. For this purpose, gridded FRD data (0.5 degrees x0.5 degrees) developed by WGLC and MODIS-Terra AOD data (1 degrees x1 degrees) have been used over the study area during 2010-2020. Major lightning activities have been observed during the pre-monsoon and monsoon seasons. The eastern part of the region, including parts of West Bengal, Bihar, Jharkhand, and Himalayan foothills has been found to be the annual lightning hotspot. Overall, an increasing trend of annual lightning has been noticed over the study area. Annual AOD over Gangetic Plain has been found to be much higher than in other regions. Seasonal variation of AOD, i.e., an increase of AOD from pre-monsoon to monsoon and declination afterwards, has been observed over Chhota Nagpur plateau. Increasing AOD trends have been found during pre-monsoon, monsoon as well as annually over the majority of the study area. Correlation analysis has indicated that convective available potential energy (CAPE) has played a major role in lightning activities over this region. In general, AOD has been found to affect lightning through microphysical effects. However, contrasting relation has been noticed over the Gangetic plains during winter because of the absence of lightning due to low convective activities and the presence of high AOD due to shallow boundary layer, anthropogenic activities, and prevailing wind patterns.