一次低涡东移引发的大暴雨过程诊断分析

Diagnostic Analysis of Heavy Rain Caused by a Low Vortex

利用气象常规观测资料和NCEP 1°×1°格点再分析资料,对温州地区2007年梅汛期雨量最大的一次降水过程做了较为全面的分析。分析结果表明:低涡东移是造成这次局地大暴雨的直接原因;强降水往往发生在低涡移动的前部和右侧,大暴雨落区与水汽通量散度负中心有着较好的对应关系;并指出华南低涡在沿海地区和内陆地区产生强降水的水汽源地有所不同;此次局地大暴雨过程的水汽输送源地有两个,分别是南海和西太平洋;在沿海地区来自西太平洋的偏东气流对华南低涡暴雨有增幅作用;低涡前部中、低层强烈的上升气流为浙南沿海持续强降水的产生提供了十分有利的动力条件。

An event with the maximum precipitation in the Meiyu period of WenZhou in 2007 is generally analyzed based on the conventional observation data and the 1°×1°NCEP/NCAR reanalysis data. The moving vortex is the efficient reason for causing the local heavy rain. It is hard to forecast the area, the intensity and the total precipitation of the heavy rain caused by a vortex in practice. By analyzing the pattern development, the influencing system and the physical parameter field, some forecasts respect of heavy rain caused by a vortex and the characteristics of the physical parameter are summarized, it is found that the heavy rain usually occures in front and the right area of the vortex, there are corresponding relationship between the area of the heavy rain and negative center of the moisture flux divergence. It is also found that the moisture of the heavy rain happened in costal area and inland area is derived from different places, the South China Sea and the North Pacific Ocean are the two moisture sources of the heavy rain. The heavy rain caused by the vortex is reinforced by the easterly airflow which comes from the North Pacific Ocean. As the dynamical condition, the strong upward current in middle-level and low-level layer in front of the vortex is in favor of the persistent heavy rain in the costal area of south ZheJiang.