一次由“列车效应”造成的致洪暴雨分析研究

2010年6月25日在粤东南部地区发生了超历史纪录的强降水过程。利用MICAPS 3.1软件系统、多普勒雷达及中尺度地面自动加密观测站等资料进行分析表明：深厚的高空冷涡位置偏南,移动缓慢是造成此次极端降水的直接影响系统。有组织排列的多单体风暴活动、地面准静止锋及其前方锋前暖区内出现的中尺度辐合长时间维持,是形成＂列车效应（Train Effect）＂的主要原因,降水回波沿东北—西南向排列的地面总能量中心移动,特殊的地形作用促使＂列车效应＂形成。反射率因子图上显示强降水回波具有低质心结构且垂直发展旺盛,具有＂牛眼＂结构特征的速度图上表明了强盛的低空西南急流存在。由于＂大风核＂存在,造成中小尺度次级垂直环流,并且这些次级环流有规则的排列,这可能是＂列车效应＂形成和维持的主要原因。在上述研究基础上提出了此次＂列车效应＂暴雨模式。

The Analysis of the Heavy Rainstorm Caused by "Train Effect"

Using MICAPS 3.1,the mesoscale automatic weather stations(AWS) and Doppler radar,the rainstorm in the southeastern Guangdong with the rainfall exceeding 600 mm within 13 hours on June 25, 2010 is analyzed.It is shown that the direct impact system of this extreme precipitation is the deep high-altitude cold vortex which located south and moved slowly;the strong low level jet(LLJ) and LLJ provided sufficient moisture and dynamic conditions;and that the organized arrangement of the multi-single storm activity,the ground quasi-stationary front and the mesoscale warm shear line which maintained for a long time are the main causes for the formation of "train effect".The precipitation echoes move along with the total surface center,and the special terrain is also one reason of the "train effect".The reflectivity images have shown that the banded heavy precipitation echo can be a low-mass center structure and then strong vertical development.The speed image with a "bull eye" structure shows that there was a low level southwest jet.Based on these studies,a "train effect" storm model is proposed.