Since June, southern my country has witnessed continuous heavy rainfall, showing a wide range of impact, long duration, extreme extremes, and high local rainfall overlap. From July 4 to 10, Chongqing, Guizhou to the middle and lower reaches of the Yangtze River experienced the strongest rainfall process this year.

　　Wang Yongguang, chief forecaster of the National Climate Center, explained that the heavy rainfall was caused by Mei Yu. Specifically, the early entry into Mei and the strong Meiyu front were the reason for the excessive rainfall during the Mei flood season in the middle and lower reaches of the Yangtze River.

How violent is the recent southern heavy rain?

　　From June 2 to July 12, at 6 o'clock, the Central Meteorological Observatory issued a rainstorm warning for 40 consecutive days, becoming the longest time since the rainstorm warning business was launched in 2007. The intensity of the recent heavy rain in the south is evident.

　　Meteorological data also confirmed this. According to statistics from the National Climate Center, since the flood season, as of July 10, there have been 15 large-scale heavy rainfall processes in southern my country. Among them, from June 11 to July 10, the main rain belt extended north to the middle and lower reaches of the Yangtze River, the rainy center is located in northern Hunan, northwestern Jiangxi, eastern Hubei, southern Anhui, central Zhejiang and other places, Zhejiang, Anhui, Jiangxi Bureau The cumulative precipitation in the area exceeds 800 mm.

　　Daily rainfall in many places broke through historical extremes. For example, during the heavy rainfall from July 4th to 10th, the daily rainfall of Huangmei, Xishui, Hubei, Ji'an, Xiajiang, and Longhui, Hunan, and other national meteorological observatories broke through extreme values.

　　From June 1 to July 9, Hubei, Anhui, Jiangsu, Guizhou, Zhejiang, Chongqing, Hunan, Jiangxi, Shanghai, Guangxi, Sichuan and other provinces totaled 85 stations with cumulative precipitation exceeding half of the annual precipitation.

　　The heavy rain brought pressure on the flood control of the Yangtze River Basin. From June 1 to July 9, the average precipitation in the Yangtze River Basin reached 369.9 millimeters, 54.8 millimeters more than the same period in 1998, the most in the same period since 1961.

How does the recent rain compare with the same period in 1998?

　　At 0:00 on July 12, the water level in the water well of Xingzi Station, the iconic hydrological station of Poyang Lake, covered a red mark-"1998 flood level 22.52M". Historical extreme value.

　　A worrisome question is, compared with the 1998 heavy rain event in southern my country, how strong was the rainfall in the middle and lower reaches of the Yangtze River?

　　"Comprehensively considering the scope, duration and rainfall, it is found that since June 27 (as of July 9), the comprehensive intensity of the regional heavy rain weather process in southern China is the fifth strongest since 1961 (first in 1998)." National Climate Center Associate Researcher Zhai Jianqing said.

　　Compared with the 1998 flood, the southern regional heavy rain weather process from June 27 to July 9 this year has the characteristics of long duration and wide range of influence.

　　From a regional perspective, the 1998 rainstorm process covered most of the area south of the Yangtze River, with more than 250 mm areas concentrated in northern Jiangnan and eastern Guangxi, etc.; this year, the rainstorm process was located to the north, concentrated in Jianghuai, eastern Jianghan, most of Jiangnan and Chongqing , Guizhou and other places, more than 250 mm area is concentrated in northwestern Hunan, southeastern Hubei, northwestern Jiangxi, southwest Anhui, western Fujian and other places.

Why did the southern rainstorm fall into the "wheel war" this year?

　　Since June, there have been frequent heavy rainfalls in southern my country. The frequency is not only reflected in the process of heavy rainfall, but also the heavy rainfall round by round, the intermittent period is very short. Why does this happen?

　　Ma Xueke, chief forecaster of the Central Meteorological Observatory, explained that this is mainly related to the atmospheric circulation situation since June this year.

　　The Northwest Pacific Subtropical High (the subtropical high for short), which has a huge impact on my country, is a stable and less active warm deep weather system. The southwestern airflow on the northwest side of the periphery is just an important channel to transport water vapor to the rainstorm area.

　　Specifically, since June this year, the subtropical high has been stronger than in the same period of previous years. The southwestern airflow around its periphery transports abundant water vapor from the Bay of Bengal or the southern sea area of ​​China to southern China. At the same time, the cold air activity in the north is also relatively frequent, causing The situation where cold and warm air continue to converge in the southern region has resulted, resulting in frequent and continuous heavy rainfall.

Is Mei Yu making trouble?

　　In recent years, extreme weather and climate events have been increasing, and the climate seems to be becoming more and more abnormal. So is the unusual climate behind the continuous heavy rainfall?

　　According to Wang Yongguang, it was Meiyu who caused the heavy rainfall. Specifically, the early entry into Meihe and the strong Meiyu front are the reasons for the abnormally high rainfall during the Meihong season in the middle and lower reaches of the Yangtze River.

　　This year's Meiyu in the Jiangnan region was 7 days earlier than in previous years, and Meiyu's "main battlefield", the middle and lower reaches of the Yangtze River, had already entered Meimei on June 9. It turned out that the onset of the South China Sea summer monsoon was earlier this year, and the location of the ridge line of the Western Pacific Subtropical High in the first half of mid-June, the two together led to the early arrival of plum in the middle and lower reaches of the Yangtze River.

　　In addition, this "monster" also obtained energy from other places, causing Mei Yufeng to be strong. A weak El Niño event occurred in the autumn of 2019, and the temperature of the North Indian Ocean was abnormally warm, resulting in a significantly stronger secondary high. At the same time, the meridional circulation at middle and high latitudes develops and the cold vortex is active. The cold air exploded on the way to the middle and lower reaches of the Yangtze River. As a result, the cold and warm air converged in the middle and lower reaches of the Yangtze River, which caused the Meiyu front to be stronger and the precipitation in the middle and lower reaches of the Yangtze River to be significantly higher.

How will the rain belt move in the future and will the pressure on flood control be reduced?

　　Since July, my country's main rain belt has maintained from the east of the southwest to the middle and lower reaches of the Yangtze River. From July 11 to 12, the main rain belt lifted northward in stages.

　　After a short intermittent period, according to the forecast of the Central Meteorological Observatory, from July 13 to 16, the main rain belt will fall southward to the middle and lower reaches of the Yangtze River. During this period, the main areas of heavy rainfall will appear in the middle and lower reaches of the Yangtze River, and some areas in eastern Chongqing, northern Guizhou, Hubei, northern Hunan, northwestern Jiangxi, central and southern Anhui, southern Jiangsu, Shanghai, northern Zhejiang, etc. To the rainstorm, the local heavy rainstorm.

　　Ma Xuejian reminded that this coincides with the heavy rain on the 4th to 7th, and it needs to pay attention to the superimposed impact of precipitation.

　　Even if the eastern section of the rain belt lifts north in mid-to-late July, the pressure of flood control in the Yangtze River Basin will not be reduced. The obvious precipitation in the middle and upper reaches of the Yangtze River will still pose a threat to the rivers and lakes with high water levels. (Peng Mei News Trainee reporter Chen Shaoying Zhang Hui intern Wen Qi reporter Han Xiaorong)

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