“7·20”华北和北京大暴雨过程的分析

Analysis of the 20July 2016Unusual Heavy Rainfall in North China and Beijing

本文对2016年7月19—21日华北及北京的特大暴雨作了研究和讨论。研究表明,该次暴雨为诸多有利因素所致:前期副热带高压呈带状稳定维持,中旬末东退,后呈"东高西低"分布,华北处于槽前辐合上升区,有利对流发生。高空西来槽停滞加深(并切断)与低层江淮暖性倒槽叠加,快速发生发展成为一深厚的气旋,出现了高低空系统的耦合。有一支暖(湿)输送带自南向北推进至关重要,源地可追踪至南中国海等低纬度地区,水汽通量辐合大值区先后经长江、黄淮至华北,有明显的中低纬度系统的相互作用。2016年的"7·20"暴雨和2012年"7·21"暴雨均存在明显的多尺度特征,但其具体特征有所不同。前者强烈对流活动稍弱于后者,降水趋势平稳,然而由于其大尺度强迫持续时间长,累积降水量仍然较大。本文主要集中于一些事实的分析,对于该次暴雨的机理尚需作进一步研究。

In this paper, both CMA and NCEP data are used to analyze the extremely severe rainfall in North China and Beijing which occurred during 19-21 July 2016 and brought the serious damage to people and society. The results are as follows. （1） At the end of the second ten days of July, the subtropical high moved eastwards and then maintained. The short wave trough was stopped and was almost stationary which was very favorable to the occurrence of the severe rainfall, （2） The coupling between the short wave trough in upper troposphere and the warm inverse trough at the surface caused rapid cyclogenesis. （3） The warm conveyor belt as the moisture passage transported very rich water vapor to North China and the obvi- ous interaction between middle and lower latitude systems existed. （4） There were obvious multi-scale characteristics in the 20 July 2016 heavy rain and the 21 July 2012 rainstorm, but they are different. The large scale forcing of the former was slight stronger, whereas the convection of the latter was more active, The mechanism and mesoscale systems of the rainstorm in 20 July 2016 need to be investigated in future.