一次盛夏华北回流暴雨天气过程的诊断分析

Diagnostic Analysis of Return-Flow Event with Rainstorm in North China

利用常规观测资料、历史天气图和NCEP再分析资料,对1998年7月22日发生在华北的一次回流暴雨天气过程进行了动力、热力等诊断分析。结果表明,该回流暴雨天气属于华北回流中的两槽一脊型,导致这次强降水的影响系统是850 hPa高度东北—西南向的低压带和地面西南倒槽,偏东暖湿气流的堆积起了触发作用;此次降水过程比较浅薄,高层没有强烈的抽吸作用,上升运动中心较低且持续时间比较短;过程水汽来自东部渤海,整个降水时段湿层深厚。

Based on the conventional observational data, historical weather maps and NCEP reanalysis data, the dynamic and thermodynamic characteristics of a return flow events with rainstorm in North China was analyzed. The results indicate that synoptic situation of this process is two troughs and one ridge, the influencing system leading to heavy precipitation is the low pressure zone of 850 hPa level and inverted trough of surface, accumulation of warm air triggers this event. The precipitation process is relatively shallow, no strong suction effect at high level, the ascending movement center is fairly low and the upper movement isn＇ t continuing longer; water vapor of return-flow event is mainly from Bohai, and wet layer is relatively thick during all precipitation regimes.