Impact of Doppler Weather Radar Data on Numerical Simulation of Heavy Rainfall

In this paper, impact of Doppler Weather Radar (DWR) data has been examined for numerical simulation of heavy rainfall events using numerical weather prediction system Advance Regional Prediction System (ARPS) model at 3 km horizontal resolution. Weather radars transmit electromagnetic waves that receive and process backscattered signals and receive information of size, shape, class and precipitation rate. Fundamental variable measured by weather radars includes reflectivity and radial velocity. The reflectivity and radial velocity observations from DWR station Delhi are assimilated into ARPS model using ARPS Data Assimilation System (ADAS) and cloud analysis scheme.

The main objective of this study is to evaluate the impact of Delhi DWR data on hydrometeor initialization (rain, snow and hail) of Numerical Weather Prediction (NWP) model, using hydrometeor analysis procedure within framework of ADAS and thence spin up problem. An initial results show that hydrometeor analysis procedure of ADAS is successfully able to convert observed reflectivity of Delhi radar to the model's precipitating hydrometeors (rain, snow and hail). The use of hydrometeor analysis for DWR data has significantly improved precipitation field in the initial conditions. It also significantly reduces spin up problem when model has been initialized with improved initial conditions.