一次切变线暴雨过程的诊断研究和数值试验

DIAGNOSTIC STUDY AND NUMERICAL EXPERIMENT OFA SHEAR LINE STORM RAINFALL PROCESS

本文对 1998年 6月 12～ 13日的一次长江中下游切变线暴雨过程进行了诊断研究并使用一个 η坐标细网格暴雨数值模式对其作了数值试验。结果发现 ,与该暴雨过程相联系的β中尺度系统主要表现在低层的切变线及地面的β中尺度气旋 ,气旋的东移和发展引起长江中下游大范围强降水 ,在启动该场暴雨过程中 ,位势不稳定起了决定性的作用 ;深厚的 β中尺度“涡柱”是该暴雨雨团的明显特征 ;地形对暴雨的强度和范围均有重要影响 ,该切变线强度对暴雨过程的降水量也有明显影响。

In this paper, a process of shear line storm rainfall, which located in the valley of middle and lower Yangtze River and happened from 12th to 13th on June 1998, is diagnostically studied. At the same time, a numerical experiment of this process is made, using a fine-mesh η-coordinate storm rainfall numerical model. It is found that the β-mesoscale system, which is related with this process, mainly shows the shear line on the low level of troposphere and the β-mesoscale cyclone on surface. The eastern move and development of the cyclone brings the wide area intensive precipitation in the valley of middle and lower Yangtze River. Potential instability plays a crucial role in starting this storm rainfall. Deep β-mesoscale vortex pole is a distinct characteristic of this storm rain-mass. Topography has important influence on both the intensity and area of storm rainfall. Intensity of the shear line also has evident effect on rainfall quantity in the process of storm rainfall.