“8·31”广东极端强降水过程边界层触发条件分析

Analysis of Triggering Conditions of the Boundary Layer For an Extremely Intense Rain in Guangdong on August 31,2018

利用CFSR再分析资料、Micaps实况以及区域自动站等资料,对2018年8月30—31日广东惠州惠东-汕尾陆河附近出现的一次极端强降水过程进行边界层触发条件分析。结果表明:在具备华南暴雨发生发展必要条件的背景下,强盛西南季风脉冲,季风低压缓慢移动造成西南-偏南气流长时间维持;边界层中尺度能量锋和辐合区的演变激发了季风气流中不稳定能量释放,以及向西南开口的"U"型山谷和迎风坡产生的气流抬升辐合,暴雨雨团遇到莲花山主峰时发生移速减慢停滞,雨强加大,在沿山脉-高潭附近的低地峡谷一带形成明显的"列车效应",致使惠东高潭过程累积和24 h降水量均刷新历史记录。

With Climate Forecast System Reanalysis （CFSR） data, Micaps observations and data from regional automatic weather stations, an extremely intense rain, which took place in the region of Huidong, Huizhou through Luhe, Shanwei on August 30-31, 2018, was analyzed for its triggering conditions of the boundary layer. The result is shown as follows. With the background of having a necessary condition for the generation and development of an intense rain in the south of China, pulses of a prevailing southwest mon-soon and slow movement of a monsoonal low pressure resulted in the maintenance of a southwest-south airflow over extended time. A mesoscale energy front and a convergence zone in the boundary layer evolved to trigget the release of instability energy in the monsoon airflow, and airflows were lifted and converged due to a ＂U＂-shaped, southwest-opening mountain valley and windward slopes. As rain clusters of the intense rain met the main peak of Lianhua Mountain, they slowed down and stagnated with increased rain rates, causing a significant ＂train effect＂ in the low land and valleys along the mountain range through the Gaotan area. All of the conditions presented above resulted in the breaking of historical records of accumulated rainfall and 24-h rainfall in Gaotan, Huizhou.