Analysis of tropical cloud-to-ground and intra-cloud lightning activity in southern India.

A detailed study of cloud-to-ground (CG) and intra-cloud (IC) lightning over southern India was conducted using new high-resolution gridded data generated from the IITM Lightning Location Network in southern India (8°–13.6°N and 74.5°–80.5°E) during 2019–2021 period. More than 5.3 million lightning strikes were observed during the period in the region. Peak CG activity is seen in a lightning hotspot located in the midland and foothills of the Western Ghats in Kerala and another CG peak is seen over the Kochi coastal belt (75.8°–76.2°E and 9.7°–10.4°N) in the Lakshadweep Sea. Our study shows that peak lightning currents during the pre-monsoon (March–May) season are mainly positive, whereas most of the currents were negative in the post-monsoon (October–December) season. This shows that the storm charge structures are different in both lightning seasons. Diurnal changes indicate that the lightning in the southern lightning hotspot region is primarily influenced by solar heating and the lightning activity peaking at 15–18 hours (local time). Higher IC activity is associated with pre-monsoon taller tropical cumulonimbus clouds (Cb), and IC activity peaks at altitudes between 10 and 18 km. It is observed that the average lightning activity duration (first to last strike) is 1.8 hours in the lightning hotspot region. Analysis of CG controlling factors shows that, over land regions, strong connections are observed with lightning and thermodynamic parameters like convective available potential energy (CAPE). However, convective inhibition (CIN) shows a weak positive correlation with lightning over oceanic regions. Also, a significant correlation (0.01 level) was observed between sensible heat flux in the lightning hotspot and coastal regions. In addition, aerosol optical depth (AOD) shows a significant correlation with lightning over the central region in southern India. [ABSTRACT FROM AUTHOR]