一次罕见的特大暴雨物理量场特征分析

Physical Features Analysis of a Rare Torrential Rain in the Land

通过对 1 998年 7月 9日丹凤县特大暴雨发生时的主要影响系统、各种物理量场特征、卫星云图演变实况、地形特征的综合分析表明 ,“7· 9”特大暴雨是在副高减弱东退 ,其外围的西南气流发展成急流 ,850 h Pa切变线过境的情况下发生的 ,地面冷锋和中尺度扰动及有利地形的叠加作用是这次大暴雨发生的触发机制 ;停滞少动的暴雨云团的持续影响是这次特大暴雨产生的主要原因。特大暴雨产生在中低层对流不稳定、高能舌和低层暖平流、高层冷平流以及低层辐合。

The '7·9' torrential rain,which occurred under the weather situation of a shrinking subtropical high,jet developed from the peripheral southwest current and shear line passing at 850hPa level is analyzed by taking into consideration the main influential system,various physical features,satellite images as well as topography.It is shown that the torrential rain is triggered combinedly by the cold front,the middle-scale turbulence and the topography,mainly caused by the stagnant rain storm cloud cluster,and initiated in an ascending motion area with convective instability at the middle level,high energy tongue,warm advection convergence in the low level and cold advection divergence at the high level.