Key Laboratory of Cloud-Precipitation Physics and Severe Storms,Institute of Atmospheric Physics,Chinese Academy of Sciences
本文针对2012年(“7.21”)和2016年(“7.20”)北京两次特大暴雨过程,利用多源观测和再分析数据,结合多种分析方法,从多个角度,较为系统地对比揭示了两次特大暴雨过程的差异,结果指出：两次过程降水总量相近,但降水历时和小时雨强不同,“7.21”历时更短、雨势更强；两次过程主导天气系统和演变、对流系统演变以及局地探空条件明显不同,“7.21”主降水时段对流有效位能显著,暖区对流性强降水主导,而“7.20”主降水时段对流有效位能小,以低涡系统性降水为主；两次过程小时雨强和短历时降水事件统计差异显著,“7.20”中等强度小时雨量站点数占比显著,而“7.21”短时强降水站点数占比明显,两次过程短历时降水事件累积雨量、持续时间、5分钟和1小时最大雨量差异明显,“7.21”短历时强降水事件占比达一半以上(小时雨量50 mm以上的短历时极强降水事件占比明显),最大5分钟和1小时降水量分别高达20.4 mm和103.6 mm,极端性显著,而“7.20”短历时中等强度降水事件占比最大,最大5分钟和1小时降水量仅为10.7和59.3 mm,“7.21”降水极端性更强、致灾性更大；两次过程水汽来源和源区定量贡献差异明显,来自中国中东部及沿海地区的水汽贡献在两次过程中均最大,但“7.21”过程上述水汽源区的贡献最突出,而“7.20”过程中,印度半岛-孟加拉湾-中南半岛、中国南海和西北太平洋及日本海等区域的贡献也较为明显。上述结论有助于深入理解和认识两次特大暴雨过程致灾程度不同的原因。
In this paper, based on multi-source observation and reanalysis data and combined with a variety of analysis methods, the two torrential rain processes in Beijing on July 21, 2012 (hereinafter referred to as "721") and July 20, 2016 (hereinafter referred to as "720") are analyzed to compare and reveal the differences between them from multiple perspectives. The results show that the total amount of precipitation of the two processes is similar, but the precipitation duration and hourly rainfall intensity are quite different which represents that he duration of "7.21" is shorter and the rainfall intensity is stronger that is corresponding with the dominant weather system and evolution, convective system evolution and local sounding conditions of the two processes. The convective effective potential energy is significant in "7.21" main precipitation period resulting in the dominant convective heavy precipitation in warm area, while the convective effective potential energy is small in "7.20" main precipitation period and it is dominated by low vortex systematic precipitation. Therefore, there are significant differences in the statistics of hourly rainfall intensity and short duration rainfall events between the two processes. The proportion of medium intensity hourly rainfall stations of "7.20" is significant, while the proportion of short duration heavy rainfall stations is obvious. The differences in accumulated rainfall, duration, 5-minute and 1-hour maximum rainfall between the two short duration precipitation events are really significant. The "7.21" short duration heavy rainfall events (the short duration extremely heavy rainfall events with an hourly rainfall of more than 50 mm accounted for a significant proportion) exceeds half, as well as the maximum 5-minute and 1-hour precipitation were 20.4 mm and 103.6 mm, respectively, which is extremely notable. While the short duration medium intensity precipitation events of "7.20" accounts for the largest proportion, and the maximum 5-minute and 1-hour precipitation of only 10.7 and 59.3 mm. Compared with "7.20", "7.21" is more disastrous. The contribution of water vapor from central and eastern China and coastal areas is the largest in both processes, which is more prominent in "7.21". However, the contributions of the Indian Peninsula - Bay of Bengal - Central South Peninsula, South China Sea, Northwest Pacific and sea of Japan are also obvious in the "7.20". The above conclusions contribute to understanding the reasons of the different disaster of the two torrential rain processes.