Meso-scale Numerical Simulation And Analysis Of Different Precipitation Schemes And Initial Fields For A Southwest Vortex Rainstorm

Using GRAPES_meso numerical model and the LAPS meso-scale data, a case ofsouthwest vortex rainstorm during July,2008is numerically simulated with6testprograms that contain2.5km and5km resolutions, explicit precipitation scheme andtwo kinds of mixed precipitation schemes. The results of contrasting various programsshow that using explicit precipitation scheme and2.5km resolution, the LAPS initialfield can best simulate the rainbands and convective rain groups of the "southwest vortex-shear line ". Then the best simulation results are used for diagnostic calculation andanalysis of meso-scale synoptic precipitation movement. The results show that the"southwest vortex-shear line" system can gather water vapor, and high humidity areamoves with the system. The divergence field determines the vertical field to cause"positive"/"negative" condensation precipitation rate in the saturated gas,and theconvergence/divergence of cloud water and rain water increases precipitation. The"southwest vortex-shear line" storm is rising in the high unstable energy ofstratification that can result in the secondary circulations and maintenance of meso-scaleconvective heavy precipitation (rain clusters) and convective precipitation area in thebackground of systematic upward motion, accompanied by meso-scale convective rainclusters. And the diagnostic calculation and analysis shows that the cumulus convectiveactivity simulated by the explicit precipitation scheme has a higher altitude and strongerwarming and humidifing role in the atmosphere between500to850hPa and strongerevaporative cooling effect of water substances from genting,and the probability of cloudwater touching and increasing into rain is higher than the mixed precipitation schemes.LAPS initial field which integrates real–time observational data simulated quality,energy and wind can reach equilibrium in a shorter time, and its process of dynamic andthermal adaptation is faster,performancing in simulated vertical velocity andprecipitation of the initial stage are better than NCEP initial field, thus the simulated rainbands and meso-scale convective precipitation live closer to fact.