[ Objective] The aim was to analyze the regional rainstorm in Hunan from August 5 to 6 in 2011. [ Method] Based on regional automatic station data,air-exploration data,upper air data and radar data in Hunan Province,the formation mechanism ot rainstorm in Hunan was analyzed. The changes of reflection rate,horizontal speed and relevant physical quantity factors in Dongting Lake were explored,and the reports of height field and wind pattern in Europe center were testified. [ Result] During this process,the regional rainstorm occurred when the typhoon influenced east coast. The coastal circulation background is a two-ridge-one-trough situation. The leading influential system is the lower trough in the upper air, shear line in the middle and lower layer and ground weak cold air. There was bypass at 200 hPa. CAPE value enlarged and SI indexcdecreased. Enough vapors can make up the transportation of water vapor in the middle and lower layer. Two echo cloud entered strong convection wind storm,and dry air entered into the storm,which resulted in slowly movement of strong wind storm. There was back wind area and strong convergence area in the lower layer. Headwind and strong convergence areas were in the lower layer of speed product. Comparing the report of 500 hPa height with the reality, it was found that the height value of the typhoon was higher than the reality, the high pressure center was smaller than the reality,48 h forecast showed more mistakes than the 24 h report. The UV report at 500 and 800 hPa was larger than that at 24 h. The error in report typhoon was large,especially around the shear line or trough line. [ Conclusion] The study provided reference for the forecast of rainstorm.%[目的]分析2011年8月5～6日发生在湖南的局部大暴雨过程.[方法]利用湖南省内区域自动站资料、探空资料、高空资料和雷达资料对2011年8月5～6日发生在湖南的暴雨过程的形成机理进行了深入分析,重点探讨洞庭湖局部区域大暴雨中反射率、径向速度及相关物理量因子的演变情况,同时检验欧洲中心高度场和风场的模式预报.[结果]此次过程是在东部沿海有台风的影响情况下局部发生的大暴雨天气过程,大气环流背景是两脊一槽形势,主要影响系统是高空低槽和中低层切变线附近以及地面弱冷空气,且200hPa存在分流现象,暴雨落区位于850 hPa的东侧和南侧;强对流的发生前,维特高K指数或K指数迅速增大,CAPE值迅速增大和SI指数的快速减小,同时当地环境有足够的水汽弥补了因中低层没有急流存在而产生的水汽的输送;在雷达回波上有2务路径的回波云团输入到强对流风暴,同时中层有干空气侵入风暴内,造成强风暴单体的缓慢移动及强度维持,在速度产品上低层存在逆风区和强的辐合区.EC 500 hPa高度预报场与实况对比发现预报的台风内部高度值比实况偏大,高压中心比实况偏小,48h预报比24h预报误差大些;500和850 hPa的UV分量的预报场48h的误差比24h大,500比850 hPa的误差大,对台风的预报误差均较大,在切变线附近或槽线附近误差亦较大.[结论]该研究为暴雨预报提供参考.
展开▼
