2008—2011年湖北暖干类暴雨特征分析

Characteristics of warm-dry heavy rain events from 2008 to 2011 in Hubei province

选取2008—2011年湖北省7个暖干类暴雨个例,利用GFS的0.5°×0.5°再分析资料进行合成分析。结果表明:湖北暖干类暴雨过程中,正涡度平流不是大范围出现,而是以正涡度平流核的形式出现并随着风场流转,使暴雨区各层涡度平流的配置快速发生变化,易引起上升运动的突然加强;暖平流从中高层扩展至整层,强暖平流中心出现在临近暴雨发生时的边界层,热力强迫导致低层强辐合,950 h Pa上下强暖平流中心与暴雨点位置较一致,对暖干类暴雨的预报有较好的指示意义;中层干空气和低层暖湿空气的侵入是暴雨区对流不稳定增长的主要影响因子,均与副热带高压的西伸发展有关。

Base on the 0.5 °×0.5 °NCEP-GFS reanalysis data,seven warm-dry heavy rain events from 2008 to 20 1 1 in Hubei province were analyzed.The results indicate that positive vorticity advection doesn′t occur in large areas during a warm-dry heavy rain process,but moves with wind as a positive vorticity advection core,which leads to rapid variation of vorticity advection in different tropospheric layers over the heavy rain areas.This is easy to make the upward motion strengthened suddenly.Warm advection expands from mid-upper troposphere to the whole troposphere;strong warm advection center appears in boundary layer where the heavy rains just occur;ther-mal forcing action leads to strong convergence in lower troposphere;locations of upper-lower strong warm advec-tion center of 950 hPa and heavy rain area are similar;the above four conditions are indicative to prediction of warm-dry heavy rain.Invasion of dry air in the middle troposphere and warm-moist air in the lower troposphere is a main impacting factor for increase of convective instability in the heavy rain areas,and both are related to the westward development of subtropical high.