Simulating a Landfalling Winter Cyclone: Comparison of a Spectral Microphysics Scheme to Bulk Schemes and Remote Sensing Data

A spectral microphysics scheme, HUCM, is recently implemented into the Weather Research and Forecasting (WRF) model and the Goddard Satellite Data Simulator Unit (G-SDSU). With this state-of-the-art numerical representation of cloud and precipitation processes in the WRF model, simulations were conducted for a landfalling Atmospheric River (AR) precipitation event in the US west coast on 30 to 31 December 2005. During this period, the intense AR transported abundant moisture, produced intense precipitation, and resulted in large hydrological impacts over California and Nevada. The Advanced Microwave Scanning Radiometer for EOS (AMSR-E) onboard Aqua satellite and a ground-based precipitation profiling radar sampled this storm. The G-SDSU is used to simulate the brightness temperature and radar backscatter signals at the instruments' operating frequencies. Analysis shows improvement of ice scattering signature in this simulation with HUCM scheme vs. simulations with several other bulk schemes (done in a previous study). It indicates a better representation of precipitation ice water path in the WRF model with the spectral microphysics scheme. The simulated radar reflectivity shows a high bias as compared to observations. Preliminary analysis illustrates that a large amount of snow with relatively large particle size, which might be attributable to the reflectivity bias. The effect of snow riming, break-up threshold, and terminal velocity spectrum on the simulations will also be explored.