湖北一次梅雨大暴雨分析

应用加密探空资料、NCEP再分析资料与自动气象站雨量资料,分析2009年6月29日湖北梅雨大暴雨。结果表明:暴雨期间700hPa江淮较长切变线维持准纬向特性,850hPa低空急流北上到江南北部。700hPa鄂西北等地准东西走向θse锋区有所加强并南移,湖北暴雨区位于θse锋区南侧且θse数值有所增加的地区。垂直积分水汽辐合大值区与强降雨带位置对应比较好,且整层水汽辐合比强降雨发生要早6h以上。恩施、武汉两站暴雨发生除了受低层切变线等较大尺度系统影响外,局地气象要素配合也很重要,尤其是低层较为充足的水汽是降雨维持的条件。当高层低槽移过,高、中层之间出现水平风垂直切变后恩施降雨明显加强。武汉站前期高层或中层干空气向下伸展,中、低层不稳定层结加强后降雨发展,其最强降雨和低层冷式切变线过境同时发生。

A Case Study of Meiyu Torrential Rainfall in Hubei Province

The Meiyu torrential rain rainstorm took place on 29 June 2009 in Hubei Province is analyzed by applying intensive meteorological radiosonde data, reanalysis data from NCEP, and precipitation data of automatic meteorological stations in Hubei Province. The results show that during the heavy rain, there existed a long quasi-zonal Jianghuai shear at 700 hPa; the north frontier of the low level jet stream at 850 hPa moved to the northern Jiangnan. The 0se front at the northwestern Hubei Province moved southward and enhanced slowly, and the rainstorm region was to the south of the 0so front, where the local change of 0se was always positive though the change amount was little. The convergence of vertically integrated moisture flux occurred before the heavy rain, and the convergence area was in accord with the location of the rainstorm. In both Enshi and Wuhan radiosonde stations, besides the large-scale low-level shear line, the occurrence of heavy rainfall was influenced bY the local meteorological elements, especially plenty of water vapor at low levels, which was a necessary condition for heavy rainfall. The rainfall became severer after the high-level trough passing Enshi and the vertical shear of horizontal wind between middle and high levels appearing. The descending dry air at high or middle levels was a good condition for heavy rainfall at Wuhan for unstable stratification was intensified accordingly. The abrupt increase of rainfall coincided with the southward passing of the horizontal wind shear at low levels.