Microphysical processes and hydrometeor distributions associated with thunderstorms over India: WRF (cloud-resolving) simulations and validations using TRMM

Abstract

Thunderstorms are one of the disastrous weather events that affect various parts of the Indian region during the pre-monsoon summer months of March–April–May (MAM). Keeping this societal impact in account, this paper has documented the vertical distribution of cloud microphysical properties and dynamical fields associated with number of thunderstorms over different thunderstorm-prone regions of India. The main objective of this study was to bring out the spatial heterogeneity in the structure of thunderstorms during MAM. In spite of being such an important weather system, the present-day skill of forecasting such systems is particularly poor. This as such prompts us to ponder whether any existing microphysical scheme is able to capture the inherent heterogeneous structure of thunderstorms over different parts of India. To find an answer to this question, the regions are divided based on pre-monsoon lightning distribution obtained from the tropical rainfall measuring mission lightning imaging sensor data. Keeping this observation in background, cloud-resolving simulations are performed using the Weather Research and Forecasting-Advanced Research Weather Model (version 3.2) along with three explicit microphysical schemes for a number of thunderstorm cases those occurred over five different regions of India. The composite structure of all thunderstorms simulated over a region is compared with observation to identify the systematic model bias. It is clearly brought out that the Thompson scheme with the present form is not able to capture different phases of thunderstorms over different parts of the country. However, WDM6 and Morrison are able to capture some of the features reasonably well, along with some degree of uncertainty. The inner structure of thunderstorms is very well brought out by contour frequency altitude diagram. This study therefore provides a framework and a basis of further modifications of WDM6 and Morrison for improving the model forecast for thunderstorms over the Indian region.