Evaluation of The Sensitivity of The Dual-Polarization Doppler Warm-Rain Radar Data Assimilation to Radar Forward Operators for a Convective Storm

Abstract

The dual-polarization (dual-pol) Doppler radar provides more information on precipitation particles compared with the traditional Doppler radar. In this study, the dual-pol radar observations of differential reflectivity (ZDR), specific differential phase (KDP), and radial velocity (VR) collected by the C-band Advanced Radar for Meteorological and Operational Research are assimilated for a convective storm on June 23,2008. Two different warm-rain radar forward operators for ZDR and KDP data assimilation are built on the basis of empirical relationships between the dual-pol variables and water content in precipitation. The advanced research version of the Weather Research and Forecasting (WRF) model and three-dimensional variational (3DVAR) data assimilation system are used in this study. The main goal of this study is to demonstrate the sensitivity of initialization and prediction of a real case event to the dual-pol radar data assimilation with different radar forward operators. The results show that both forward operators successfully assimilate the ZDR, KDP, and VR data and help with the initialization and short-term forecast for the thunderstorm event. In addition, significant sensitivity caused by the use of different radar operators is found in the thermodynamic, kinematic, and microphysical fields of the storm, especially over the storm region. However, the storm location and movement are not largely influenced; hence, short-term precipitation forecast is not largely affected by the use of different radar operators.