一次西南低涡暴雨过程特征分析

An Analysis of Heavy Rain Caused by Southwest Vortex

利用NCEP/NCAR提供的逐日4次的FNL全球再分析格点资料和CMORPH融合逐时降水格点数据,对2016年6月29日~7月2日发生的一次西南涡东移引发的强降水过程的降水变化特征、大气环流背景、水汽输送和动力特征进行了分析,结果表明:本次西南涡主要发展在850 hPa附近,西南地区上空500 hPa高原深槽东移、700 hPa的气旋切变和低空暖湿气流的增强促使西南涡生成并迅速东移发展,副高的稳定维持和深厚的中低空西南急流为特大暴雨的产生提供了有利的条件。本次西南涡暴雨降水过程的水汽主要来源于孟加拉湾。西南涡在湖北东部滞留发展的主要原因是受到588线的阻挡,高原低槽和冷槽合并发展,副高西侧的西南急流作为充足的水汽来源和强烈的动力触发条件,导致了该天气过程的发生。降水中心位于涡度大值区与负散度区和垂直运动中心重合区域,有利于降水进一步增强。

In order to study a strong precipitation process caused by the eastward movement of the southwest vortex from June 29 to July 2, 2016, the FNL global analysis data provided by NCEP/NCAR and the CMORPH hourly precipitation data were used to analyze the weather circulation background, dynamic and thermal properties of the process. The results show that the formation and rapid eastward movement of the southwest vortex are caused by the eastward movement of the deep trough at 500 hPa, the cyclone shear at 700 hPa and the enhancement of the warm and humid air flow at low altitude. The stable maintenance of the subtropical high and the combination of the two troughs at high altitude cause the abnormal rainstorm in Hubei Province. During the period of vortex development, the convective upward movement develops violently and the unstable energy is released in large quantities, which is the favorable condition for the rainstorm weather. The en-hancement of southwest low level jet and the addition of East wet air flow are conducive to the rainstorm. The warm and humid air from the bay of Bengal and the South China Sea converges with the dry and cold air from the north, providing sufficient water vapor supply for this precipitation process. The center of the wet Q convergence area basically coincides with the center of the heavy rainfall.