中文摘要：

利用T213L19资料以及地面和高空观测资料,对2008年7月20～25日一次高原低涡东移引发四川盆地暴雨的机制进行了分析,结果表明：降水的发生、发展与湿位涡的时空演变有很好的对应关系,湿位涡高低层正负区叠加的配置是低涡暴雨发展的有利形势,MPV1负值中心和MPV2正值中心及其包围的密集区是暴雨产生的警戒区。中低层z-螺旋度水平分布对降水落区和强降水中心的分布有较好的指示性,z-螺旋度垂直分布能反映暴雨发生时大气的动力特征,雨区上空高层负涡度、辐散与低层正涡度、辐合相配合,是触发暴雨的动力机制;相对螺旋度与降水落区及降水中心亦配合较好,并与未来6h的降水落区和强度分布存在较好的正相关,这对降水落区及强度分布的预报有一定参考价值,强降水中心通常出现在相对螺旋度梯度的高值一侧。

英文摘要：

Using the T213L19 data and the observation data,the mechanism of a case of Plateau Vortex moving east that caused heavy rainfall in Sichuan basin from 20 to 25 July 2008 was analyzed,including the moving of the Plateau Vortex,distribution of rainfall,transportation of water vapor,equivalent potential temperature,moist potential vorticity and helicity.The results show that there is well corresponding relationship between the occurring and developmen of precipition and spatial and temporal changes of moist potential vorticity,especially the superposed allocation in positive and negative zones of midand lower-levels of moist potential vorticity is advantageous situation for development of Plateau Vortex rainstorm.The negative value center of MPV1 and positive value center of MPV2 and its surrounded dense areas are an alert area which the rainstorm occurs.Distribution of z-helicity on midand lower-levels can give good indication to the distribution and center of rainfall,z-helicity can reflect the dynamic character of weather when the rainstorm occurs,and divergence of negative vorticity on higher level matched convergence of positive vorticity on lower leve1 is a dynamic mechanism to trigger heavy rain.Relative helicity also reflects the area and center of rainfall,which has better positive correlation to the area and intensity of next 6 h precipitation.It has certain value to settle in an area for precipitation prediction.Then severe rainfall center often occurs on the positive value side of relative helicity gradient.