Beijing's rainfall lasted for 83 hours! China Meteorological Administration: There are three reasons for rainfall | Beijing Tianjin Hebei | China Meteorological Administration
The China Meteorological Administration held a press conference on the 3rd to release and interpret the recent heavy rainfall situation in the Beijing Tianjin Hebei region.
Zhang Hengde, deputy director of the National Meteorological Center, said at the press conference that from July 29 to August 1, Beijing, Tianjin, Hebei and other places experienced historical extremely heavy rainfall processes, and the regional rainfall process intensity exceeded the three extreme rainstorm processes in the history of North China, which is rare in history. The heavy rainfall process this time has the characteristics of long duration, large cumulative rainfall, and strong extremes.
Long duration. The process started on July 29 and ended on August 1. It lasted nearly four days. The duration of rainfall in Beijing was 83 hours. heavy rainstorm to extremely heavy rainstorm occurred in Handan, Xingtai, Shijiazhuang, Jinzhong, Shanxi, Hebi, Henan and southwest Beijing for two consecutive days.
Accumulated rainfall is high. The cumulative rainfall in southwestern Beijing, central and southwestern Hebei, and other areas is 350-600 millimeters, with some areas receiving 700-800 millimeters. The maximum cumulative rainfall is 1003 millimeters, with a rainfall area of 170000 square kilometers above 100 millimeters.
Rainfall is highly extreme. The average process rainfall in Beijing is 276.5 mm and the maximum rainfall is 744.8 mm, while the average process rainfall in Hebei Province is 153.2 mm and the maximum rainfall is 1003 mm, all exceeding the three extreme rainstorm processes in the history of North China. The maximum cumulative rainfall occurred in Zhaozhuang and Liangjiazhuang, Lincheng, Xingtai, Hebei, at 1003.0 millimeters. In normal years, the total annual precipitation in Xingtai City is about 500 millimeters, which means that in just two days, Xingtai has received two years of normal rainfall.
There are also two stations in Beijing with accumulated precipitation of more than 700 mm, far exceeding the extreme value of the "July 21" extremely heavy rainstorm in Beijing by 541 mm in 2012. According to statistics from the meteorological department, 14 national meteorological observation stations in Hebei and Beijing have exceeded historical extremes in daily precipitation, and 26 national meteorological observation stations have exceeded historical extremes in cumulative rainfall over three days.
When it comes to why extreme heavy rainfall occurs in Beijing, Tianjin, Hebei and other areas, Zhang Hengde said that there are mainly three reasons:
One is abundant water vapor conditions. The weakened low-pressure circulation of Typhoon No. 5 "Dussuri" brought sufficient water vapor to converge with the southeast airflow around the subtropical high. In addition to the water vapor transported by Typhoon No. 6 "Kanu" over a long distance, the two streams of water vapor converged directly to the North China Plain.
The second is the obstruction of the high-pressure system. The subtropical high pressure system and the northern continental high pressure ridge are located on the east and north sides of the precipitation system, respectively. The two major high pressure systems merge to form a high pressure "dam", blocking the progress of the precipitation system and causing long-term heavy rainfall in Beijing, Tianjin, Hebei and other areas.
The third is the uplift effect of mountain terrain. The existence of the Taihang Mountains and Yanshan Mountains forces the transported water vapor to be uplifted by terrain dynamics in front of the mountains, causing more water vapor to condense into rain, enhancing the intensity of rainfall.
"This round of heavy rainfall in the Beijing Tianjin Hebei region is a rare event in history, with a large cumulative rainfall, extreme intensity, and short-term rainfall in mountainous areas. It has led to waterlogging, flash floods, and geological disasters in many areas, as well as large-scale floods in the Haihe River basin, posing serious challenges to the prevention and response of the Beijing Tianjin Hebei region." Zhang Hengde said that under the influence of such extreme heavy rainfall, it is easy to cause urban waterlogging and accumulation, which will have extremely adverse effects on transportation, urban operation, agricultural production, and residents' lives. In addition, villages, towns, and mountainous areas are prone to geological disasters such as loose soil, flash floods, landslides, and rockfalls in the event of short-term heavy rainfall and heavy rainfall, making defense difficult.
This round of rainfall has seen a sharp increase in rainfall throughout the entire area, causing significant flooding in the Haihe River Basin. The overall flood control situation in the Beijing Tianjin Hebei region is severe.
Zhang Hengde stated that it is recommended to pay attention to the weather forecast and warning information issued by the meteorological department at any time and prepare for defense in advance.