湘北一次暴雨过程的天气学诊断分析

Diagnostic Analysis of Heavy Rainfall in North Hunan Province

利用常规观测资料和NCEP/NCAR再分析资料,对2007年5月24日发生在湘北的一次大暴雨天气过程进行了天气学诊断分析。结果表明:这次大暴雨过程的主要影响系统是低涡切变线。暴雨区中低层为对流不稳定层结,并且具有良好的水汽输送和水汽辐合,而低空急流是对流不稳定能量的建立者和不稳定能量释放的触发者。暴雨出现在湿Q矢量散度负值中心激发的次级环流上升气流区,且其辐合区对未来6 h暴雨的强度及其落区具有较好的指示作用,而低层湿Q矢量锋生函数的正值区与同时刻暴雨区有较好的对应关系。

Based on the routine observational data and NCEP/NCAR reanalysis data, a heavy rainfall in North Hunan Province in May 2007 is diagnosed. The results show that the main influencing system of heavy rainfall is a meso-scale vortex with shear line in the lower troposphere. There are instable convection stratification, intensive water vapor transportation and convergence over rainfall center when the rainfall happens, and low-level jet is the creator of the instable convective energy and the trigger of instable energy＇s release. The heavy rainfall region locates at the ageostrophic rising region forced by the wet Q-vector. Convergence of the ageostrophic wet Q-vector has good indication in the forecasting of the intensity and area of the coming 6h rainfall. The region-magnitudes of wet Q-vector frontogenesis function can be used to locate the area of coming rainfall.