Spatial and Diurnal variation of Lightning activity and CAPE over Indian region and their correlation with various indices

Abstract

Thunderstorms and Lightning need three essential ingredients for their occurrence: Instability, Adequate low-level moisture, and some lifting mechanism. Among all the three ingredients, Instability represented by the positive Convective Available Potential Energy (CAPE) plays a vital role in Thunderstorm and Lightning activity. Instability allows the air parcels in the lower levels to rise into the upper levels of the atmosphere.

In this study, we have studied the spatial and diurnal variation of Lightning activity and CAPE over the Indian region. Five year ILLN Lightning data and Hourly ERA5 CAPE data has been used for the study. On a seasonal scale, Lightning flash counts and CAPE have a correlation of around 0.62. For the Indian region, Intra-cloud (IC) discharges are higher than Cloud-to-ground lightning discharges. Higher Thunderstorm and Lightning activity are observed during Pre-monsoon and Monsoon periods. On a diurnal scale, peak Thunderstorms and Lightning activity occur during the late afternoon (3 PM - 5 PM IST). Higher CAPE values are observed during the early afternoon (12 PM - 2 PM), which leads to severe convection activity in the following few hours. Spatially, we observe more thunderstorm events near the Northeast region, East India, and the windward side of Western Ghats. In addition to the high CAPE value, moisture availability and some triggering mechanisms are necessary to initiate and maintain small-scale convection. Despite lower CAPE values in fewer regions, the prevailing meteorological conditions and orography provide favorable conditions for Thunderstorm formation and lightning activity over those regions in India.