Polarimetric Radar Signatures of a Simulated Supercell Storm Using a Two-Moment Microphysics Scheme and Polarimetric Radar Emulator

i Abstract A general polarimetric radar emulator is developed based on rigorous scattering calculations using the T-matrix method for reflectivity, differential reflectivity, specific differential phase, and co-polar cross-correlation coefficient. A continuous melting process accounts for the entire spectrum of varying density and dielectric constants. This emulator is able to simulate polarimetric radar measurements at weather radar frequency bands and can take as input the prognostic variables of high-resolution nonhydrostatic NWP model simulations using one-, two-, and three-moment microphysics schemes. The new emulator is tested at 10.7 cm wavelength with a model-simulated supercell storm using a double-moment (DM, or two-moment) microphysics scheme to examine its ability to simulate polarimetric signatures reported in the observational studies. The simulated fields exhibit realistic polarimetric signatures that include Z DR and K DP columns; Z DR arc, mid-level Z DR and ρ hv rings; and hail signature in terms of the general location, shape and strength. We compared the simulation to one employing a single-moment microphysics scheme and found that certain signatures, such as Z DR arc and mid-level Z DR and ρ hv rings, cannot be reproduced with the latter. It is believed to be primary caused by the lack of proper treatment of size sorting in the single-moment scheme. These results suggest that two-or higher-moment microphysics should be used to adequately describe certain important microphysical processes in supercell storms. They also demonstrate the utility of a well designed radar emulator for validating numerical models. In addition, the simulator can also serve as a training tool for forecasters to recognize polarimetric signatures that can be reproduced by advanced numerical weather prediction models.