Impact of the COVID-19 lockdown on zonal variability of lightning activity over the Indo-Gangetic Plains.

Abstract

Aerosol optical depth (AOD) and cloud top temperature (CTT) decreased in the Indo-Gangetic Plains (IGP) during the COVID-19 lockdown in India from March 23/25 to May 30, 2020, compared to the same period in 2017-2019. Aerosols, convective vigour, and moisture were pivotal in influencing the lightning flash rate (LFR) across various longitudinal belts. In the arid environment of the 70-82° E belt, coarse-mode mineral particles dominated, and LFR was low and inversely correlated with AOD. However, a fivefold increase in LFR in the 82-85° E belt was associated with the formation of deep convective clouds during the lockdown. In the 85-90° E belt, LFR declined during the lockdown but increased in 2017-2019, supporting the roles of mixed-phase processes in the dry and moist environments. AOD and aerosol extinction (AE) peaked at 0.8 and 1.5-1.6, respectively, at 88° E. In the moist environment of the 90-95° E belt, the influence of heat-absorbing aerosols diminished during the lockdown. Here, the vertical development of clouds was driven by the orography of hill ranges along the India-Myanmar border, rather than thermodynamic processes. Overall, both LFR and CTT declined with longitude due to decreased anthropogenic aerosols during the lockdown. Supporting evidence from related parameters reinforces these conclusions.