Sensitivity of Simulated Great Salt Lake Effect Precipitation to the Parameterization of Microphysical Processes

Weather Research and Forecasting model simulations of the 27 Oct 2010 Great Salt Lake Effect (GSLE) snowstorm are compared to determine sensitivity of simulated precipitation to the choice of microphysics scheme. The simulated liquid equivalent precipitation amount and location are very sensitive to the choice of microphysics scheme in this case. Sharp differences are seen in the hydrometeor composition of the simulated GSLE snowstorms despite all simulations sharing identical initial conditions and identical model configurations other than microphysics parameterization. To better understand these differences, the values of source and sink terms in the hydrometeor tendency computations are compared between microphysical schemes. In addition, the differences in physical processes represented by the tendency equations are compared. The differences in snow and graupel tendency equation formulation and the values of source and sink terms shared between tendency equations determine the hydrometeor composition of the simulated storm, which ultimately determines the amount and location of liquid equivalent precipitation generated by the simulations. These results highlight the consequences of parameterization choice that may be unknown to the researcher or forecaster when they design a simulation or forecast. The results also highlight specific aspects of the microphysics schemes that may be altered to improve GSLE forecasting.