梅雨锋中尺度切变线雨带的动力结构分析

利用密集的地面观测网资料以及中尺度数值预报模式输出产品 ,分析了 1 991年 7月 8～ 9日江淮地区梅雨锋中尺度切变线雨带的中尺度动力结构。发现沿切变线走向有一条中尺度涡管 ,位于对流层中低层 ,高度呈波状起伏。波峰处有较强经向环流 ,强降水位于波峰附近的经向垂直环流之下。降水强度与涡管强度密切相关 ,涡管增强时降水增强。涡管强度与中低空的条件性对称不稳定有关。

THE DYNAMICAL STRUCTURE OF A MESOSCALE SHEAR-LINE RAIN BELT ON MEIYU-FRONT

Based on the products of the mesoscale numerical model MM4 and surface observational data,the dynamical structure of a typical mesoscale shear line rain belt occurring on Meiyu front in the Changjiang Huaihe River Basin during July 8-9,1991 has been analyzed in this paper.The results showed that there was a mesoscale vortex tube along the mesoscale shear line on the middle low troposphere,and its altitude varied in a wave shape.There was stronger longitudinal circulation near the wave peak.The surface mesoscale cyclonic and anti cyclonic circulations were located at east and west sides of the wave peak respectively.Heavy rain area located under the vertical longitudinal circulation near the wave peak.The precipitation intensity was closely related with the intensity of the vortex tube.The latter was closely related with the conditional symmetric instability in the middle low troposphere.