THE IMPACT OF PHYSICS PARAMETERIZATION SCHEMES ON MESOSCALE HEAVY RAINFALL SIMULATION

Based on the non-hydrostatic version of Mesoscale Model version 5(MM5) and the data sets of four heavy rainfall scenarios occurring in Aug.2001 in China, the impacts of three non-adiabatic physic processes including cumulus parameterization scheme, planetary boundary layer schemes and radiation paramet erization schemes on dynamic and thermodynamic element predictions of heavy rain in China are investigated, with deeply analyzing the effect of cumulus paramet erization schemes on mesoscale heavy rain simulations and discussing the feasibility of using model physics perturbations in ensemble simulation of heavy rain.The results show that non-adiabatic physic processes have less ef fects on the short-range forecast of geopotential height.Planetary boundary layer schemes and cumulus convection schemes have more impacts on heavy rain than radiation schemes, the most influences of two schemes of planetary boundary layer and cumulus convection are on the divergence of moisture flux, vertical velocity, unstable strat ification, which are the three basic conditions of torrential rain.The great influence of planetary boundary layer is on the thermal fields in the low levels.The forecast variance between convection schemes grows fast in the beginning to 12-h time periods of simulation, with the variance structure being a good correlation to that of subgrid rain, in the later periods of simulation with less correlation and decrease during 12-18h time periods, then oscillates in the subsequent integral period.The structures of dynamic and thermal fields and the initial field using for model integral are all different since 12-h.