甘肃中东部初夏一次暴雨天气过程的动力诊断

Diagnosis on a Rainstorm in Early Summer in the Middle-east Part of Gansu

利用Micaps常规和ECWMF资料,对造成2004年5月28～29日甘肃省中东部初夏区域性暴雨过程的高、低空急流及锋区等天气系统进行分析,结果表明:(1)500hPa西风带急流轴(≥20m.s-1)从乌拉尔山中底部向巴尔喀什湖移动,其分裂的短波槽和冷空气沿急流底部向甘肃河西至青海省中部发展,为这次大降水的形成和维持提供了能量;(2)在副热带高压快速南压东退中,高压边缘的西南暖湿气流为此次降水过程提供了充沛的水汽来源;(3)垂直速度、水汽通量、水汽通量散度等物理量对此次大(暴)雨有很好的指示意义。从能量场上,总温度平流和差动平流场对这次降水过程也有重要的贡献。

This paper analyzed the synoptic system such as the high and low jet,the front which induced the regional rainstorm in the middle-east part of Gansu province during 28-29 May 2004 by using Micaps and ECWMF data.Results are as follows：（1）The cold air and the shortwave trough disrupted from the westly jet at the level of 500 hPa which moved from the Ural Mountain to the Balkhash Lake,moved along the bottom of the jet to the Hexi Corridor of Gansu and the middle part of Qinghai,which provided energy for the rainstorm;（2） The SW flow at the edge of subtropical high provided abundant vapour for it when subtropical high withdrew rapidly eastward and southward;（3） The vertical velocity,the vapor flux and the divergence of vapor flux have good indication to this rainstorm,and the total temperature advection and the differential advection have important contribution to the rainstorm.