Assimilation of Dual-Polarimetric Radar Observations Using WRFVAR with Ice Particles in Control Variables

The dual-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 dual-polarimetric radar data may provide additional benefit to better describe the storm structure and microphysical properties in cloud. However, due to the complicated relationships in microphysics processes and uncertainty in dual-polarimetric radar measurement, the assimilation of dual-polarimetric radar variables is a challenging problem.

This study explores the methodology to assimilate the dual-polarimetric radar observations with WRF 3DVAR system. A package has been developed to include the ice-phased microphysical processes into the tangent linear and adjoint of precipitation model of WRF 3DVAR system. Snow and cloud ice have been added into the WRF 3DVAR moisture control variable. The inclusion of ice-processes in the forward operator will better describe the ice particles in cloud. The experiments are conducted with assimilation of horizontal reflectivity, radial velocity, and differential reflectivity. The presentation will highlight the difference between warm-rain and ice-phased processes in assimilation of the observations from the dual-polarimetric radars. Preliminary result from the assimilation experiments for a convective storm (15 March 2008) will be discussed at the conference. Further details of the methodology of data assimilation, the influences of the dual-polarimetric radar variables, and the impact of the dual-pol data on microphysical properties will be presented at the conference.