阳江复杂地形对特大暴雨影响机理的数值研究

采用中尺度天气预报模式WRF (Weather Research Forecast)对广东省阳江地区2019年5月26日00时—28日00时暴雨事件进行数值模拟,并通过一系列的地形敏感试验,讨论地形对暴雨发生和发展的影响。结果表明:地形对暴雨的影响显著,地形的高度影响暴雨的强度和位置;与未作任何改变的控制试验相比,地形降低试验和细网格地形高度取平均试验无山脉的阻挡,阳江地区无爬流和绕流运动及相对涡度减小,南风将低层水汽和能量带到更北的位置,暴雨中心随之北抬;增高地形试验,由于山脉阻挡,更多水汽和能量堆积,以及地形的阻挡产生绕流和爬流运动,绕流有利于局地涡旋生成,爬流运动会增加垂直运动速度,正涡度中心增强,低层的水汽辐合上升凝结,造成更大暴雨。 

A NUMERICAL STUDY ON THE INFLUENCE MECHANISM OF YANGJIANG'S COMPLEX TOPOGRAPHY ON AN EXTREME RAINFALL EVENT

In the present study, the mesoscale Weather Research Forecast model was used to simulate the rainstorm event which occurred from 00:00 May 26 to 00:00 May 28, 2019 in Yangjiang, and a series of topographic sensitivity tests were conducted to discuss the impact of topographic conditions on the occurrence and development of rainstorms. The results showed that topography had a significant effect on the intensity and location of rainstorms. Compared with the control test, the topographic lowering test and the fine grid topographic height averaging test showed that there was no climbing or circumfluence movement and the relative vorticity decreased in Yangjiang because there was no mountain obstruction. The southerly wind brought the low-level water vapor and energy further north, and the rainstorm center moved northward. On the contrary, the terrain elevation test resulted in more water vapor and energy accumulation due to the obstruction of mountains. Meanwhile, the circumfluence movement generated by terrain obstruction was conducive to the generation of local vorticity and the increase of vertical movement speed of climbing flow. As a result, the positive vorticity center was enhanced, and water vapor in the lower layer conversed, rose, and condensed, resulting in heavier rain.