一次东风波及其诱生低涡发生发展的诊断和数值试验

DIAGNOSTIC STUDY AND NUMERICAL EXPERIMENT OF A MOST HEAVY SHOWER CAUSED BY THE EASTLY WAVE

利用NCEP 1x1再分析资料诊断2001年8月3～4日发生在浙南闽北的东风波及其诱生中尺度低涡的暴雨过程。根据螺旋度（Helicity）分析了过程中的暴雨演变以及雁荡山脉诱生中尺度低涡发生发展的原因。同时，利用中尺度有限区域模式MM5V2对该东风波诱生中尺度低涡进行模拟。结果表明：螺旋度大值中心和锋区的强度和位置的演变较好反映了暴雨落区和中尺度低涡的诱生、移动。螺旋度的时空演变对暴雨发生有很好的预示意义，高、低层螺旋度的低层正值辐合与高层负值辐散的配置是引起降水的重要机制；螺旋度计算较中尺度模式诱生低涡的初生位置、路径预报准确率高，两者集成可以提高诱生低涡的预报准确率。

Abstract It introduces mainly the process of the most heavy shower occurring in south seacoast of Zhejiang caused by the eastly wave from August 3 to 4, 2001. At the same time, we discuss the low cyclonic eddy caused by the eastly wave. Helicity and its effects on the all process are found. The MMSV2 model is used to simulate the most heavy shower and the low cyclonic eddy. The results show that there exits close relationship between helicity and the most heavy shower, the higher helicity might be one of the mechanisms for rain storm development. Helicity and MM5 model used together can offer more correct low cyclonic eddy and rain strom forecast.