一次冷涡暴雨的中尺度对流云团分析及数值模拟研究

Mesoscale Convective Cloud Cluster Analysis and Numerical Simulation of a Cold-Vortex Heavy Rain Event

利用MM5模式对2000年8月发生在河北省的一次暴雨过程进行了模拟,发现本次过程是由蒙古东部的低涡与副热带高压共同作用形成的,而局地大暴雨的直接原因是中尺度对流云团的作用。中尺度对流云团形成前期有一个能量急剧积累的过程。通过改变地形、低层东南风大小的敏感性试验,发现这次暴雨虽然发生在河北东部,但华北西部、北部的地形对暴雨影响很大:当降低地形高度后,雨区的位置和强度都发生变化;减弱低层东南风后,蒙古东部冷涡的强度和移动速度都有不同程度的改变,并且层次越低影响越明显。

The MM5 model is used to simulate the heavy rain process occurred in August 2000 in Hebei Province. The results show that the process was caused by a cold vortex over the eastern Mongolia and the subtropical high, and the direct trigger for the local severe heavy rainfall was a mesoscale convective cloud cluster. There was rapid accumulation of energy before the mcsoscale system took shape. Sensitive experiments on ter rain effect and southeast winds at low levels for the heavy rainfall process are conducted. It is concluded that although the heavy rain occurred in the eastern Hebei Province, this process was greatly affected by the mountains over the west and north parts of North China. When the terrain is removed, the location and intensity of the heavy rainfall change obviously; and when the low-level southeast wind is weakened, the movement speed and intensity of the cold vortex over the eastern Mongolia change in different degrees; and thc lower the level is, the more obvious the effect.