Assimilation of Dual-polarimetric Radar Observations with Real Case Studies

Dual-polarimetric radar variables 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-scale structure and characteristics of microphysical properties. However, due to the complicated relationships in microphysics processes and uncertainties in dual-polarimetric radar measurements, the assimilation of dual-polarimetric radar variables is a challenging problem.

The purpose of this study is to explore the methodology of the assimilation of dual-polarimetric radar observation with WRF 3DVAR system. A package with ice-phased microphysical processes has been developed in the forward operator of WRF 3DVAR radar assimilation system. The inclusion of ice-processes in the forward operator will better describe the ice particles in cloud. The experiments are conducted with assimilation of the 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) and two snow-storm events (20-22 December 2012 and 6-7 February 2013) will be discussed at the conference. In addition to dual-polarimetric radar data assimilation, an information content analysis is conducted to analyze the uncertainty of dual-polarimetric observations and relationships between the microphysical parameters. Further details of the methodology of data assimilation, the impact of the dual-polarimetric radar data on microphysical properties, and result from the information content analysis of the dual-pol variables will be presented at the conference.