Key Laboratory of Cloud-Precipitation Physics and Severe Storms,Institute of Atmospheric Physics,Chinese Academy of Sciences
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.