A Polarimetric Radar Forward Operator and Application for Convective Storm Initiation

The dual-polarimetric radar transmits and receives both horizontal and vertical power returns. The polarimetric radar variables can be used to estimate hydrometeor size and shape, hydrometeor correlation, and better precipitation intensity. The application of the polarimetric radar data may provide additional benefit to better describe the rapid variations in updraft, convergence, thermodynamic structure, and microphysical properties within growing cumulus clouds during convective storm initiation. The primary goal of this research is to investigate the performance of numerical model in depiction of convective clouds in terms of polarimetric signature.

In this research, we have developed a scheme-specific forward operator for polarimetric radar based on the 2-moment Morrison microphysics scheme. A high resolution (~1-km) numerical simulation is conducted with the Weather Research and Forecast (WRF) model for a convective initiation event occurred on 15 July 2018. The radar forward operator is used to convert the model output into polarimetric radar variables. Statistical analysis will be conducted to evaluate the sensitivity of the radar forward operator to microphysics properties. NEXRAD Level-2 observation from multiple radars will be processed and compared with the results from the radar operator as a mean of assessing the performance of the WRF model and the microphysics scheme. The presentation will highlight the differences between modelled and the observed polarimetric signatures within growing cumulus clouds associated with the convective initiation event. Details of the polarimetric radar forward operator and model verification results will be discussed at the conference. The presentation will also discuss the preliminary results on an analysis of derived cloud-top properties based on use of 1-min GOES satellite images, and their relationship to the radar-based polarimetric variables observed for in-cloud processes.