江汉平原一次突发性特大暴雨的诊断分析

Diagnostic Analyses of an Abrupt Torrential Rain at Jianghan Plain

利用NCEP 1°×1°逐6 h分析资料和湖北省自动气象站雨量资料分析了2006年5月24日夜间江汉平原南部一场突发性大暴雨、局部特大暴雨过程的成因。结果表明,这次强降雨发生之前,高空急流南界先向北移出湖北省上空,伴随着强降雨的发展与减弱,急流南界又重新南扩到湖北南部;急流核在强降雨发生之前在35～40°N之间东移,特大暴雨发生时已位于暴雨区东北方向渤海湾一带。这次特大暴雨发生在边界层中尺度正涡度区合并加强过程中。暴雨过程伴随着高层惯性稳定度的减小与低层位势不稳定的维持;南海西北部到华中地区西南水汽通道的建立是特大暴雨发生的有利条件,水汽输送主要集中在中、低层。特大暴雨发生之前低层正值湿螺旋散度增加明显。

An abrupt torrential rain occurred at the south of Jianghan Plain at the night of 24th May, 2006. Using NCEP analyzed data and automatic meteorological station data, a research is conducted. The results are reached as follows： before the heavy rain, the south border of upper level jet （ULJ） stream retreated from Hubei province to the north, with the occurring and weakening of the rain, the border came back to the upper level over Hubei province again; before the heavy rain, the core of the ULJ moved from the west to the east within the zone from 35°-40°N, and when the heavy rain began, it was at the northeast of Hubei province already, The occurrence of the torrential rain coincided with the strengthening of a meso-scale zone with positive vorticity at boundary layer; water vapor was transported from northwestern South China Sea to Central China at low levels; during the rain there were decrease of inertial stability at high level and maintaining of potential instability at low levels; before the heavy rain, large positive moisture helicity divergence appeared at 950 hPa level.