2004年云南秋季强降水位涡诊断分析

A Diagnostic Analysis of Potential Vorticity for Yunnan Heavy Rain in Autumn 2004

利用NCEP格点资料和常规观测资料对2004年云南秋季强降水进行位涡诊断分析,结果表明,干湿位涡均能较好地反映天气系统的演变特征,干位涡能很好地反映滇黔辐合强弱和地面冷空气的移动路径。湿位涡则能反映暖湿气流活动特征。强降水发生期间,中高层强干湿位涡向低层传送,低层负湿位涡向上伸展。对流层中高层的干湿位涡强中心向低层传送方向和强度变化与强降水雨带移动方向及雨强变化一致。此次强降水对流层中层的强干位涡源位于川东,表明该过程与9月2—6日川东大暴雨有关。

Based on NCEP grid data and routine observational data, the characteristics of the potential vorticity （PV） of heavy rainfall occurring in Yunnan Province during autumn of 2004 are analyzed. The results show that both DPV and MPV can well present the features of the weather systems. The DPV reflects both convergence intensity between Yunnan Province and Guizhou Province and surface cold air moving activities more particularly. The MPV can reflect well cold and warm air flowing characteristics. During the heavy rainfall in the upper troposphere the strong DPV and MPV tend downwards to the low-level, and vice MPV in the lower troposphere stretch up. The direction and intensity changes of the big center of DPV and MPV in the upper troposphere tend to downward the lower-levels are consistent with the moving direction of heavy rainfall belts and the variation of the rain intensity. The origin of the middle tropospheric strong DPV lies in the east of Sichuan Province in this rainfall process, which indicates some relation between the heavy rain in the eastern Sichuan Province during 2-6 September and the rainfall process in Yunnan Province.