Comparison of Simulated Polarimetric Signatures in a Squall Line Case over South China Using Two-Moment Bulk Microphysics Schemes in WRF

To compare the microphysical process produced by different microphysics schemes in the Weather Research and Forecasting (WRF) model, simulations for a squall line case over south china is examined in this study. Polarimetric variables of four different double-moment microphysics schemes: Morrison, Milbrandt and Yau (MY2), Thompson and WRF DM 6 category (WDM6), are computed from WRF model output using a polarimetric radar emulator. And the polarimetric radar signatures from these microphysics schemes are compared with polarimetric radar observation of the squall line. It shows that the leading edge convection of the squall line is basically emulated by the four schemes while polarimetric signatures differ a lot, values of ZDR are much higher in the Morrison and MY2 schemes compared with observation, vertical analysis indicates it is the result of graupel overproduction. As for the stratiform regions, the Thompson scheme produces anomalous high values of ZDR compared to the polarimetric radar results, it is related to the overestimation of aggregation process in vertical direction, and the WDM6 scheme produces a persistently smaller stratiform rain area because of the one-moment design for frozen species.