[Explanation] The rain in Beijing this year is extremely abundant, and some netizens even said that this year Beijing has become a "small Jiangnan".
According to data from the Beijing Meteorological Bureau, since the flood season (June 1-August 31), the average precipitation in Beijing has been 627.4 mm, the highest in the past 20 years.
According to Zhang Yingjuan, a senior engineer of the Beijing Climate Center, the precipitation in Beijing in July was 400.4 millimeters, which is the largest in history since 1951.
[Concurrent] Zhang Yingjuan, Senior Engineer, Beijing Climate Center
(Beijing) The precipitation in the whole flood season is 627.4 mm, which is 70% more than the same period of normal year, and it is 373 mm in the normal year.
The precipitation in July reached 400.4 millimeters, which was the highest in history since 1951.
In terms of the number of precipitation days, the precipitation in July reached 20 days, which was more than normal, and obviously doubled, with only 10.8 days in a normal year.
The precipitation throughout the flood season is characterized by less precipitation in the early period, and obviously more precipitation in the middle and late periods.
[Explanation] Zhang Yingjuan said that Beijing entered the main flood season 10 days ahead of schedule this year. During the flood season, the precipitation intensity is strong, and the characteristics of wind and hail are obvious. More than 30% of the rainfall process is accompanied by hail or short-term gale weather of level 6 or higher.
[Concurrent] Zhang Yingjuan, Senior Engineer, Beijing Climate Center
The main rain belt moved to North China on July 11, and Beijing also entered a main flood season, which was 10 days earlier than usual.
The intensity of precipitation this year is relatively large, and the characteristics of wind and hail are relatively obvious. There are 62 precipitations in the entire flood season, which is an increase of 30% over the same period last year.
There were 9 rainfall events of the magnitude of heavy rain and above, of which there were two torrential rains. The maximum hourly rain intensity was 102.6 mm, which occurred in Panggezhuang in Daxing on June 30.
In addition, more than 30% of the precipitation occurs during the flood season, and it has a wind and hail weather process accompanied by short-term strong winds of level 6 or higher.
[Explanation] Why is there so much rain this year?
Zhang Yingjuan introduced that more precipitation is mainly affected by the atmospheric circulation, which is directly related to the transportation of water vapor.
[Concurrent] Zhang Yingjuan, Senior Engineer, Beijing Climate Center
This year’s water vapor transport is mainly affected by the subtropical high in the Western Pacific. This year’s subtropical high was in July. With the start of the rainy season in North China, the subtropical high marked a second northward jump after July 11, and water vapor was directly guided by the periphery of the subtropical high. Transported to our North China region, caused our July precipitation is obviously on the high side.
Compared with the precipitation in the whole August, the average year (August 2021) is still about 20% more than normal. Caused by frequent fluctuations.
[Explanation] Will such a "humid" rainy season become the norm?
Zhang Yingjuan responded.
[Concurrent] Zhang Yingjuan, Senior Engineer, Beijing Climate Center
At present, it cannot be explained by the anomaly of excessive precipitation this year, because precipitation is not only directly related to water vapor transportation, but also has a great relationship with the scale of time and space and geographical location. We can only say According to certain data, it is a certain change in the structure of precipitation, but it is still not easy to say whether this change is a normal change.
Dong Zeyu reports from Beijing
Editor in charge: 【Luo Pan】