An ice-phase forward model for radar data assimilation with WRFVAR and preliminary result for polarimetric radar data assimilation

This research explores the methodology to assimilate Doppler radar observation using the Weather Research and Forecasting (WRF) 3-Dimensional Variational (3D-Var) data assimilation system with ice-phase microphysical processes. The ice-phase processes play important roles in precipitation formation, especially for deep convection. The publicly-released WRF 3D-Var only includes the warm-rain processes in precipitation. An update to the precipitation physics in the WRF 3D-Var is developed by including the ice-phase microphysics. Snow and cloud ice have also been added into the moisture control variable of WRF 3D-Var. The inclusion of ice-processes in the forward operator will promote better description of the ice particles in mid to high troposphere. Results are compared for experiments that assimilate radar reflectivity and radial velocity data using the warm-rain and ice-phase radar packages. The presentation will highlight the benefit that the ice-phased radar data assimilation provides to convective storm initialization and short-term forecast.

The polarimetric radar transmits and receives both horizontal and vertical power returns. It can provide information on hydrometeor size and classification that radar reflectivity alone cannot discern, such as shape, hydrometeor correlation, and better precipitation intensity approximations. The assimilation of the polarimetric radar data may provide additional benefit to better describe the storm structure and microphysical properties. Case studies have been conducted in attempt to assimilate the polarimetric radar data using the ice-phase WRF 3D-Var package. Preliminary result from the case studies will be discussed at the conference. Further details in the high resolution simulations, the influences of the polarimetric radar variables, and the impact of the polarimetric data on initial condition and short-term forecast will be presented at the conference.