Evaluating microphysics schemes of WRF model in simulating Lightning and Thunderstorm event over Kerala

Abstract

Lightning is an electrical discharge influenced by various cloud microphysical processes like cloud droplet formation and ice crystal growth within a thundercloud. Microphysics Parameterisation (MP) schemes of the Weather and Research Forecasting (WRF) model are responsible for representing cloud droplet formation, ice crystal formation and precipitation formation. Evaluating the performance of different MP schemes is crucial for accurate lightning prediction.

A severe thunderstorm event on May 22, 2022, over the Kerala region, which recorded a peak 30-minute flash count of ~1200 flashes observed by the Indian Lightning Location Network (ILLN), has been simulated in the WRF model. Three Microphysics (MP) schemes: Thompson, Morrison, and WDM6, have been tested using three nested domains (27 km, 9 km, 3km), and the output of the 3km domain has been analyzed.

WDM6 and Morrison schemes have been found to match the observed lightning distribution (both spatially and temporally, with WDM6 capturing flash magnitude). All tested microphysics schemes underestimate the number of lightning flashes compared to observations. While all microphysics schemes captured similar trends in CAPE, there were slight differences in the simulated magnitudes. The vertical distribution of CAPE also showed minimal variation between the different schemes.

Further research is ongoing to understand how thermodynamic parameters beyond CAPE, microphysical processes, and dynamical factors influencing cloud development and electrification contribute to discrepancies between simulated and observed lightning.