At 18: 00 on November 16, the Central Meteorological Observatory issued the latest meteorological disaster warning, announcing the lifting of the yellow warning of meteorological drought in many areas. This also means that from August 18th to November 15th, the 90-day meteorological drought warning was finally lifted today.
The 90-day meteorological drought has caused the drought area south of the Yangtze River to reach 503,000 square kilometers. Under severe drought, such as Poyang Lake in Jiangxi Province, in September, the water area was reduced by more than 90% compared with the maximum water area period; Dongting Lake in Hunan Province, on November 7th, the water area was only 361.09 square kilometers, which was only one seventh of the normal situation.
In addition, in 51 counties and cities of 11 cities and prefectures in Hunan Province, the problem of people having difficulty drinking water due to drought has appeared to varying degrees.
Why does the Yangtze River basin, which is full of water, dry up in flood season? Even the problem of drought in summer, autumn and winter? With the lifting of the drought warning, does it mean that the drought situation in the above areas will recover quickly? Some meteorologists said that the drought in the middle and lower reaches of the Yangtze River will continue until March next year.
↑ According to the Central Meteorological Observatory
There will be moderate to heavy rain in the next three days.
Rainfall is beneficial to alleviate the drought to varying degrees.
According to the above warning issued on November 16, since November 15, there has been obvious rainfall in dry areas such as Jiangnan and South China, moderate rain or heavy rain in northeastern Guangxi, western and southern Hunan, northern Guangdong, southwestern Jiangxi, western Fujian and other places, including local heavy rain in Hunan and Jiangxi. It is estimated that there will be moderate to heavy rain and local heavy rain in parts of Guangxi, Hunan, Jiangxi, Zhejiang, Jiangsu and northern Fujian from 16th to 19th.
On the morning of the 16th, the weather forecast issued by the Central Meteorological Observatory also showed that in the past 10 days (November 6-15), the accumulated precipitation in the eastern part of northwest China, north China, south-central part of northeast China, central and western Shandong, eastern Sichuan, southern Guangdong and other places was 10-30 mm, and the local area exceeded 50 mm, which was significantly higher than normal. The main precipitation process period was 11-12 days.
In the next 10 days (November 16-25), the accumulated precipitation in most parts of the south of the Yangtze River, South China and Guizhou will be 25-40mm, including 50-80mm in parts of the south-central part of the Yangtze River, northern part of South China and southern coastal areas, and more than 100mm in some areas. Among them, Jiangnan, South China, Chongqing, Guizhou and other places are rainy, and the accumulated precipitation is 40-70% more than normal, and the local area is more than double.
The Central Meteorological Observatory believes that the rainfall process is conducive to alleviating the drought in the above areas to varying degrees. After comprehensive judgment, the yellow warning of drought in Jiangnan and South China was lifted. According to the climate forecast, the meteorological drought in northern Jiangxi, Hunan, Guizhou, Yunnan and southern Sichuan may still be maintained, and it is necessary to continue to do a good job in drought monitoring and drought prevention and drought relief.
↑ According to the Central Meteorological Observatory
Persistent rare drought in the Yangtze River basin
The water area of Poyang Lake has shrunk by more than 90%
Since this summer, there has been a persistent and rare meteorological drought in the Yangtze River basin in China. Looking back at the drought changes in the past four months, in June, there was a meteorological drought in the north of the Yangtze River. From July to August, the meteorological drought in the Yangtze River basin developed rapidly. In September, most of the south of the Yangtze River suffered from drought in summer, autumn and winter, and the particularly dry area was further expanded. As of November 14th, Red Star journalists inquired about the data of China Meteorological Bureau and found that the extreme drought area south of the Yangtze River has reached 503,000 square kilometers.
Under the severe drought, farmland has been cracked and water level has been low in many places in the Yangtze River Basin. According to meteorological drought monitoring, as of November 13th, moderate to severe meteorological droughts still exist in most parts of the south of the Yangtze River, the eastern part of southwest China and northern South China, among which, most of Hunan, eastern Guizhou, southeastern Chongqing, western Jiangxi, southeastern Hubei and northeastern Guangxi have special droughts.
The severity of drought in various places is self-evident. On November 9, Hunan Provincial Water Resources Department announced that 116 counties and cities in Hunan Province have entered severe meteorological drought and 69 counties and cities have experienced severe drought. The number of continuous severe drought days in 77 counties and cities has exceeded 60 days, and the longest in Xinshao is 91 days.
Affected by drought, 51 counties and cities in 11 cities and prefectures in Hunan Province have difficulty drinking water due to drought to varying degrees. Official website, Hunan Provincial Water Resources Department, shows that the above-mentioned people who need water for drinking water are mainly distributed in Zhangjiajie, Chenzhou, Xiangxi and other places. In addition, all kinds of water conservancy projects in Hunan Province have a total water storage capacity of 24.198 billion cubic meters, accounting for 50.23% of the available water storage capacity, 30.5% less than the same period of the previous year, and the available water consumption is 12.176 billion cubic meters. In the past three days, the daily average has decreased by about 50 million cubic meters.
The drought situation in Jiangxi Province is also not optimistic. According to the statistics of official website, Jiangxi Provincial People’s Government, at 16: 00 on November 15th, there were 331 stations with mild drought, including 55 stations with severe drought and 84 stations with severe drought. On that day, the storage capacity of small reservoirs in the province was 1.236 billion cubic meters, with a filling rate of 21.2%. Of the 10,560 small and medium-sized reservoirs in the province, 3,743 were below the stagnant water level.
The drought in the Yangtze River basin can also be seen from the shrinking water areas of Dongting Lake and Poyang Lake. Taking Poyang Lake in Jiangxi Province as an example, affected by the continuous drought and lack of rain in Jiangxi Province since July, the middle and late September of this year is the migration season of winter migratory birds to Poyang Lake, but Poyang Lake has entered the dry season two months earlier due to drought.
According to the red warning of low water issued by Jiangxi Hydrological Monitoring Center on September 27th, the water level of Xingzi Station, the representative station of Poyang Lake, dropped to 6.97m, which is 0.14m lower than the lowest water level in history. The water area of Tongjiang in the lake area is 240 square kilometers. According to Fengyun meteorological satellite monitoring, the largest water area of Poyang Lake in 2022 should be 3,331 square kilometers. In other words, compared with the period of maximum water area, the water area of Poyang Lake at that time was reduced by more than 90%.
On October 5, the water level of Xingzi Station in Poyang Lake dropped to 6.83 meters again, which was 0.28 meters lower than the lowest water level in history.
Dongting Lake, located in Hunan, was affected by the lack of rain in the whole province. By November 9, the water level of rivers and lakes continued to be dry. According to the satellite monitoring on November 7th, the water area of Dongting Lake is 361.09 square kilometers, which is only one seventh of the normal situation. At 8 o’clock on the 9th, the water level of Chenglingji Station, the representative station of Dongting Lake, was only 19.21 meters. There are also 29 stations in Hunan whose water levels are close to or lower than the historical lowest water level. According to the statistics of Hunan Water Resources Department, as of November 9, there were 88 rivers and 49 rivers with a basin area of over 50 square kilometers and 100 square kilometers, and the length of the cut-off river was about 1061 kilometers. Kangjiagang Station of Ouchi River has been cut off for 121 days.
Does the lifting of the early warning mean the end of the drought?
Hunan, Jiangxi and other places will last until March next year.
In people’s impression, the Yangtze River basin is rich in water resources, especially from early June to mid-July every year, after entering the "Meiyu" period in the middle and lower reaches of the Yangtze River, most of the water levels in the basin will rise to varying degrees. But why is there a "drought in flood season" in the south this year? There are even rare droughts in summer and autumn?
A comprehensive observation and analysis was made on 173 stations in Sichuan, Chongqing, Guizhou, Hubei, Hunan, Jiangxi, Anhui, Jiangsu, Zhejiang and Shanghai in the document "Study on the Characteristics and Causes of Major Drought in the Yangtze River Basin in Summer of 2022" written by relevant authors of Lanzhou Institute of Drought Meteorology of China Meteorological Bureau, Key Laboratory of Drought Climate Change and Disaster Reduction of Gansu Province and Key Laboratory of Drought Climate Change and Disaster Reduction of China Meteorological Bureau.
The study found that the drought began in June and developed rapidly in July. After entering August, the scope was further expanded and the intensity was further intensified. According to the above literature analysis, the drought event in the Yangtze River Basin in 2022 was accompanied by persistent high temperature and abnormal evaporation, which was an abnormal drought event caused by multiple factors.
According to the literature analysis, the overall temperature in the Yangtze River Basin is on the high side, with the highest temperature above 35℃ in most areas and even over 40℃ in some areas, and the number of high temperature days in some areas exceeds 40 days. In addition, the summer evapotranspiration anomaly of the whole basin is the second largest in history since 1960, which further aggravates the water shortage in the whole region and leads to the rapid development of high temperature and drought.
At the same time, Zhang Juan, a meteorologist of China Weather Network, had previously responded to Red Star News. The main reason for the long duration of this round of drought is the low precipitation and high temperature since this summer.
According to the statistics of China Meteorological Bureau, from June 1 to November 13 this year, the average precipitation in the southern region was 606 mm, which was 26.2% less than the normal period, the lowest in the historical period since 1961. The average temperature is 24.4℃, 1.1℃ higher than normal, the highest in the same period since 1961.
It is also mentioned in the above literature that during July and August, the western Pacific subtropical high was large in area and strong in intensity, and controlled the Yangtze River basin in China for a long time. At the same time, the polar vortex is small in area and weak in intensity, and the South Asian high is large in area, strengthened and moved eastward. These factors jointly affect the whole circulation pattern, resulting in weak water vapor transport conditions in the Yangtze River basin and prevailing in downward flow, thus causing serious high temperature and drought events.
Zhang Juan also added that there were fewer typhoons generated and landed in China this summer, which also caused a large-scale, long-lasting and strong drought in the middle and lower reaches of the Yangtze River and Sichuan and Chongqing areas. In addition, since September, the subtropical high is still extremely strong, and there is no effective rainfall in Jiangxi and Hunan. During the National Day holiday, the high temperature in the south broke records, which also led to the drought in Jiangnan and other places.
Zhang Juan said that in addition, under the strong control of subtropical high, autumn tigers have been raging in the south since September, and the drought in the south continued to develop in November, and it suffered a rare summer and autumn drought.
"This year’s drought in the Yangtze River Basin began in the middle and late June, and it has been more than four months now. In addition, it is now entering the autumn and winter season with little rain, and the situation of continuous drought in summer, autumn and winter has basically taken shape." Lv Juan, director of the Center for Flood Control, Drought Relief and Disaster Reduction of China Academy of Water Resources and Hydropower Research, said in an interview with Science and Technology Daily recently.
Then, as the Central Meteorological Observatory announced today that the yellow warning of meteorological drought has been lifted in many areas, does this mean that the dry weather in various places has come to an end?
In this regard, Lv Juan believes: "According to the analysis of the distribution law of precipitation during the year and the characteristics of historical drought and drought in the region, it is preliminarily judged that the drought in Hunan, Jiangxi and other places in the middle and lower reaches of the Yangtze River will last until March next year, and it is necessary to further calculate the clear water account and make the best use of water resources to ensure the safety of urban water supply."
Red Star News reporter Yang Yuqi Zhang Yanliang
Editor Ren Zhijiang Editor Pan Li