“2015.08.27”黔西南大暴雨天气学成因分析

Analysis on Torrential Rain during Aug. 27, 2015 over in the South-West of Guizhou Province

利用常规观测资料、自动站降水资料、MICAPS资料及1? ×1? NCEP再分析资料,对发生在黔西南2015年8月27日夜间的大暴雨过程进行了分析,结果表明:此次暴雨过程中对流层中高层西太平洋副热带高压稳定维持,东亚大槽南压,引导冷空气南下,配合两高切变共同影响造成了此次大暴雨过程;暴雨发生前,水汽辐合区主要在贵州中西部,在该水汽输送带的北侧,由于弱干冷空气的侵入,水汽输送急剧减少,形成了明显的水汽通量梯度区,暴雨发生时,在西南暖湿气流的引导下,贵州西部出现了大片强水汽输送带,且伴随有强烈的水汽辐合,为该地区暴雨的发生发展提供了有利的水汽条件;暴雨中心在发生强降水的时候,中低层均为正涡度区,且正涡度的梯度明显加大,高层为明显的散度,说明在暴雨发生时暴雨站的上空对应着高空辐散、低层辐合,为暴雨的发生发展提供了有利的动力条件;暴雨中心在强降水发生时位于暖湿不稳定层结中,低层有冷空气向南侵入,促使其南侧的暖湿气流被迫抬升;FY-2G资料显示,影响此次暴雨天气的两个对流云系先后从云南东部东移进入黔西南,在发展过程中合并,形成列车效应,三个暴雨、大暴雨中心是由不同的对流云团造成的,降水主要出现在云团冷云区、梯度大值区及对流云团合并区域,气流沿切变北侧的偏北气流向东南方向移动,途径黔西南的大部,造成全州性的暴雨、大暴雨天气。

Based on the conventional observation data, automatic station precipitation data and NCEP/NACR reanalysis data, the rainstorm process at 20:00 27 Aug to 20:00 28 Aug in south-west of Guizhou province was analyzed. The results are as follows: the western Pacific subtropical high maintained stable, east Asia large tanks guided the cold air southward, and they joint caused the torrential rain process by cooperating with projects shear;before the heavy rain, the water vapor convergence zone is mainly in the Midwest of Guizhou. On the north side of the conveyor belt, the water vapor transmission decreased dramatically due to the invasion of the weak dry cold air, and the obvious water vapor flux gradient zone was formed. When the heavy rain occurred, leaded by the warm moist air flows, big strong water vapor conveyor belt appeared in the west of Guizhou with strong vapor convergence, which provided favorable moisture conditions;when rainstorm occurred, the lower-level was positive vorticity area, and the gradient of it increased obviously;while the high-level was of obvious divergence, which indicated that the divergence in high-level and convergence in low-level over the rainstorm station provided a favorable dynamic condition for the development of heavy rain;storm centers were located in the warm wet unstable stratification, and low-level cold air invaded to the south, forcing the warm moist air in southern to raise. FY–2G satellite data showed that: two convective clouds from east Yunnan went eastward into the southwest of Guizhou province, merged in the process of development, forming the train effect;three rainstorm, heavy storm centers were caused by different convective clouds;precipitation mainly appeared in the cold cloud area, large gradient value area and convective cloud merging area;air flow along the north side of shear flowed to the southeast of the north direction, passing the most parts of the southwest of Guizhou province, and caused statewide, torrential rain.