高原涡与西南涡相互作用引发MCC暴雨的形成机制分析

Analysis of formation mechanism of MCC heavy rain caused by interaction between plateau vortex and southwest vortex

使用常规观测资料、ERA-Interim再分析资料和卫星资料,以2014年7月8—10日西南涡和高原涡相互作用引发MCC产生大暴雨的天气过程为例,分析了两涡作用导致大暴雨的形成机制。结果表明:相互作用前期,两涡涡心间距较远,在500 hPa高度上两者同处于青海南部的气旋及其向南延伸的低槽前。约24 h后,高原涡东移与西南涡在不同高度上垂直叠加,耦合作用形成,导致四川盆地的大暴雨。利用卫星云图分析两涡作用伴随的MCC特征,发现强降水区与云团黑体亮温的冷中心吻合。西南涡与高原涡相互作用时,对流层低层形成强烈的辐合,垂直上升运动加强,大气流场呈强烈不稳定性,与涡心附近形成的水汽辐合作用结合,促进MCC发展成熟,导致四川盆地大暴雨天气形成。

Based on conventional observation data,ERA-Interim reanalysis data and satellite data,the two vortex effects by taking the weather process of the MCC from heavy rain caused by the interaction between the southwest vortex and the plateau vortex from July 8 to 10,2014 were analyzed,as well as the mechanism led to the formation of heavy rains.Results show that in the early stage of interaction,the distance between the two vortex cores is far,and both of them at 500 hPa height are sited in front of the cyclone in the southern part of Qinghai and the low trough extending southward.After about 24 hours,in the eastward movement,the plateau vortex vertically overlap with the southwest vortex at different heights,and the coupling effect is formed,which leads to the formation of heavy rain in the Sichuan Basin.The satellite cloud image is used to analyze the MCC characteristics that the two vortices accompany.It is found that the strong precipitation area coincides with the cold center of the cloud black body.When the southwest vortex interacts with the plateau vortex,the lower troposphere forms a strong convergence,the vertical ascending motion is strengthened,and the airflow field is strongly unstable,which combine with the water vapor radiant formation formed near the vortex core,so as to promote the maturation of MCC and lead to the formation of heavy rainstorms in the Sichuan basin.