Rainfall types in the lifecycle of a stationary cloud cluster during the Indian Summer Monsoon: An investigation with numerical simulations and radar observation

Abstract

The performance of three microphysics schemes (WRF Double Moment 6-class (WDM6), Morrison double moment (MORR), and spectral bin microphysics (Fast version) (SBMF)), with increasing complexities, in simulating various rainfall-types during the lifecycle of a tropical continental mesoscale cloud cluster (CC) are presented in this study. The CC spent its entire lifetime over the surveillance area of a polarimetric C-band radar, over the peninsular Indian region in a monsoon environment. Observed and simulated rainfall properties throughout the lifecycle of the CC are intercompared. A rainfall-type categorization algorithm has been applied to the observed and model simulated reflectivity fields. Microphysics scheme with the least complexities produced the highest convective rainfall-type, lowest stratiform rainfall-type, and a remarkable early cessation of the CC. With increasing complexities, the microphysics schemes are found to represent the rainfall-types more close to radar observations. Major differences are noted during the mature and dissipation phases, especially in the stratiform rainfall-type. The rainfall-types derived from radar, as well as three simulations with WDM6, MORR, and SBMF schemes, showed ~18%, ~54%, ~41%, and ~29% of convective rainfall fraction (including isolated convective categories), ~14%, ~33%, ~18%, and ~20% of mixed rainfall fraction and ~68%, ~13%, ~42%, and ~50% of stratiform rainfall fraction respectively during the lifecycle of the CC. The accumulated rainfall derived from radar observations, using a blended rainfall estimation algorithm, indicated substantial differences in the observed and simulated rainfall pattern. The lower moment scheme has a tendency to produce more lighter as well as heavy rainfall compared to the higher moment schemes.