毛乌素沙漠东部边缘中β尺度暴雨和冰雹综合分析

利用多普勒雷达资料、Micaps系统提供的常规观测资料和物理量场,对2006年9月20日发生在毛乌素沙漠东部边缘的一次强对流天气过程进行了分析。结果表明:冰雹和暴雨是由两块呈块状的中β尺度强对流单体造成的;地面能量比中α尺度"Ω"系统的生成,为能量的积聚和集中释放提供了有利条件;地面能量比中β尺度能量比低值舌的生成,为强对流天气的发生提供了抬升触发机制;冰雹和暴雨发生前,涡度场和散度场的耦合、影响雹暴区次级环流的形成,为雹暴的发生维持提供了动力机制;850 hPa等压面上湿正压场和湿斜压场的配合、以及湿位涡的三维空间结构,对雹暴的发生及落区有指示意义;在多普勒雷达径向速度场上,雹暴运动的前方对流层低层有中气旋生成,雹暴运动的后方对流层低层有中反气旋生成,而对流层中高层有辐散生成,且超级单体特征明显。

Comprehensive Analysis on Mes-β- Scale Rainstorm and Hails on the Eastern Border of Maowusu Desert

The process of a strong convective weather occurred on September 20,2006 on the eastern border of Maowusu desert is analyzed by use of observation data and Doppler Radar data.The results show that the hail and rainstorm are cause by two blocks of mes-β-scale strong convective cells.The formation of mes-β-scale"Ω"system provides a favorable condition for concentrating and releasing energy.The formation of low-value tongue in ground energy creates a trigger mechanism for strengthening convective weather.Before the hail and rainstorm,the coupling of strong vorticity and divergence generates the secondary circulation system and provides the dynamical mechanism for the generation and development of the hail storm.The combination of both wet barotropy field and wet baroclinity field on the equal pressure surface of 850 hPa and three-dimensional structure of MPV are the meaningful indicator of occurring of hail and rainstorm.At the field of Doppler Radar speed,a meso-cyclone originates before the strong hail storm in lower troposphere and a meso-aticyclone forms behind the strong hail storm in lower troposphere.The divergence occurs in higher troposphere and the characteristics of the super cell are evident.