Impact of DWR radial wind on simulation of western disturbances using NCUM-R modeling system

Abstract

The present study evaluates the impact of use of radar observations in data assimilation system by simulating the evolution, propagation and intensity of three western disturbances (WDs). Two numerical experiments were conducted viz. CTL and RAD (assimilation of radar radial velocity plus other observations utilized in the CTL) in this study. The initial conditions generated, after assimilation of radial velocity observations in RAD experiment can simulate evolution, characteristics, structure and associated precipitation with WDs properly compared to CTL. The south-westerly wind bias is seen in CTL analyses over the western Himalayan region due to the scarcity of surface and upper air observations in all cases. But the feature clearly improved in the RAD. The northward transport of moisture fluxes from Arabian Sea and spatial distribution of moisture convergence zone around the WDs are well manifested in RAD analyses which closely matched with ERA5 reanalyses in all cases. But strong magnitude of moisture fluxes is noticed in CTL analyses on many occasions. The magnitude, time and spatial pattern of the high vorticity at the mid-troposphere are adequately simulated by the RAD and are well matched with the corresponding ERA5 reanalyses in all cases. The magnitude, evolution and propagation of various kinetic energy budget terms and precipitation are relatively well simulated in the RAD than the CTL in comparison with ERA5 in all cases. Overall, the assimilation of radial velocity into the high-resolution assimilation-forecast system beneficially impacted the rainfall forecasts, which is validated with various statistical skill scores.