Analysis and evaluation of WRF microphysical schemes

13 In the present study, three meteorological events of extreme deep moist convection, 14 characteristic of South Easter South America, are considered to conduct a systematic 15 evaluation of the microphysical parametrizations available in the Weather Research and 16 Forecasting (WRF) model by undertaking a direct comparison between satellite-based 17 simulated and observed microwave radiances. A research radiative transfer model, the 18 Atmospheric Radiative Transfer Simulator (ARTS), is coupled with the Weather Research 19 and Forecasting (WRF) model under three different microphysical paramterizations (WSM6, 20 WDM6 and Thompson schemes). Microwave radiometry has shown a promising ability 21 in the characterization of frozen hydrometeors. At high microwave frequencies, however, 22 frozen hydrometeors significantly scatter radiation, and the relationship between radi23 ation and hydrometeor populations becomes very complex. The main difficulty in mi24 crowave remote sensing of frozen hydrometeor characterization is correctly characteriz25 ing this scattering signal due to the complex and variable nature of the size, composi26 tion and shape of frozen hydrometeors. The present study further aims at improving the 27 understanding of frozen hydrometeor optical properties characteristic of deep moist con28 vection events in South Easter South America. In the present study, bulk optical prop29 erties are computed by integrating the single scattering properties of the Liu (2008) DDA 30 single scattering database across the particle size distributions parametrized by the dif31 ferent WRF schemes in a consistent manner, introducing the equal-mass approach. The 32 equal mass approach consists in describing the optical properties of the WRF snow and 33 graupel hydrometeors with the optical properties of habits in the DDA database whose 34 dimensions might be different (D ′ max) but whose mass is conserved. The performance 35 of the radiative transfer simulations is evaluated by comparing the simulations with the 36 available coincident microwave observations up to 190 GHz (with observations from TMI, 37 MHS, and SSMI/S) using the Chi-square test. Good agreement is obtained with all ob38 servations provided special care is taken to represent the scattering properties of the snow 39 and graupel species. 40