P86  Impact of Cloud Microphysics Schemes in WRF Model on the Simulation of a Winter Storm as Compared to Radar and Radiometer Measurements

Han, Mei, Scott A. Braun, Toshihisa Matsui, National Aeronautics and Space Administration, Christopher R. Williams, NOAA/CIRES, Takamichi Iguchi, NASA/ESSIC

The unique assumptions of particles size distribution (PSD), number concentration, shape, and fall velocities in different microphysics schemes in NWP models are critical in simulating precipitation profiles and microwave radiative properties. Using observations from a space-borne radiometer and ground-based precipitation profiling radar, the impact of cloud microphysics schemes in WRF model on the simulation of brightness temperature, radar reflectivity, and Doppler velocity, is studied.

Customized simulations of the radiative properties are conducted for four different schemes in the WRF model, including GSFC, WSM6, THOM, and MORR. It is found that simulations with different schemes show large variations in the brightness temperature, reflectivity, and Doppler velocity. A general bias of ~ 20 K or larger is found in the (Polarization-Corrected) microwave brightness temperature in these schemes, which is linked to overestimate of the precipitating ice aloft. The simulated reflectivity with the THOM scheme appears to agree well with the observations. We also find a high bias of ~5 and ~10 dBZ in the simulated radar reflectivity with the GSFC, WSM6, and MORR schemes. These biases are attributable by the snow intercept parameter, N0s, for the 1-moment schemes, and by the snow number concentration, Ns, for the 2-moment scheme. Doppler velocity simulations based on the GSFC scheme show a reasonable agreement with the observation, while other schemes appear to have a ~ 1 m s-1 high bias.

A spectral bin microphysics scheme, HUCM, is recently being added into this study.  Preliminary results on the reflectivity and microwave brightness temperature simulations based HUCM will also be discussed.