Frequent extreme weather, flood prevention needs to be paid close attention to (deep reading·Focus on flood season ③)
Recently, many places in my country have been experiencing heavy rainfall, and the flood control situation is very severe.
What are the characteristics of the weather and climate in this year's flood season?
How will the rain and flood situation be in the future?
What issues should be paid attention to in flood prevention and mitigation?
The reporter interviewed many experts.
Since entering the main flood season, the precipitation in eastern China has basically been distributed in the north, more in the south, and less in the south, and extreme rainstorms have occurred frequently.
Since the flood season this year, many places in our country have suffered heavy rainfall.
From July 17 to 22, Henan Province encountered heavy rainfall. The accumulated rainfall was large, the duration was long, the short-term rainfall was strong, and the extremes were prominent. The daily rainfall of 19 counties and cities exceeded the historical extreme value, causing serious impacts.
According to Chen Lijuan, chief forecaster of the National Climate Center, according to the monitoring of the National Climate Center, since the main flood season (June 1 to July 31), precipitation in eastern China has basically been distributed in the north and the south.
It is more than 50% more in western Heilongjiang, parts of central and eastern Inner Mongolia, most of Beijing-Tianjin-Hebei, most of Henan, northwestern mountains, parts of Jiangsu, and northern Zhejiang, and more than 2 times more in parts of northern Henan, showing strong extremes.
The precipitation in the southern part of Jiangnan, most of southern China, and most of the northwestern region was significantly less than normal.
Chen Lijuan said that from the fall of 2020 to the spring of 2021, a moderate-intensity La Niña event occurred in the equatorial Central and Eastern Pacific, and the sea surface temperature continued to be lower than the normal average.
Generally, the summer of the year when the La Niña event decays is conducive to the northerly subtropical high of the western Pacific Ocean, which leads to more water vapor being transported to the northern regions of my country, and the precipitation in the north is higher than usual.
In addition, the overall global climate anomaly has been remarkable this year, especially in the mid-high latitudes of the northern hemisphere.
In addition to the frequent occurrence of extreme rainstorms in North China and Huanghuai areas, extreme weather and climate events also occurred in many parts of the world from June to July.
Chen Lijuan said: "Looking at the global climate situation this year, there have been significant climate abnormal events in winter, spring, and summer. Abnormal weather and climate events continue to emerge due to various reasons. The combination of atmospheric circulation abnormalities is the direct cause. Climate warming has aggravated the instability of the climate system and increased the possibility of certain extreme weather and climate events."
Global warming has led to frequent occurrences of extreme weather and climate events in some areas, increasing their intensity
According to the climate statement issued by the World Meteorological Organization, the global average temperature in 2020 is about 1.2 degrees Celsius higher than the pre-industrial level (average between 1850 and 1900).
2011-2020 is the warmest 10 years since the meteorological record, and the warmest 6 years have occurred from 2015 to 2020.
The United Nations Intergovernmental Panel on Climate Change (IPCC) assessment report pointed out that global warming has led to frequent occurrences and increased intensity of extreme weather and climate events in some regions.
"A large number of studies have confirmed that as the climate warms, the atmosphere can hold more water vapor before it is saturated, leading to an increased possibility of extreme heavy precipitation. Historical statistics show that the frequency of extreme high temperature events in the northern hemisphere has increased in recent decades." Said Dr. Han Zhenyu, who is engaged in climate change research at the National Climate Center.
Han Zhenyu said that the latest climate model forecast simulations show that extreme high temperature events will increase in most land areas of the world, and extreme low temperature events will decrease; heat waves will occur more frequently and last longer.
As the global average surface temperature rises, extreme precipitation events in most land areas of mid-latitudes and humid tropical regions are likely to increase in intensity and frequency; the difference in precipitation between wet and dry regions and between wet and dry seasons will increase .
Climate projections show that in the future, under the scenario of not controlling greenhouse gas emissions, by the end of the 21st century, the probability of occurrence of high temperature and heat waves in terrestrial areas will be 5-10 times that of the present, and extreme precipitation in terrestrial areas will increase by about 20%.
Affected by this, my country's extreme precipitation will increase by about 21%, the eastern coastal areas affected by typhoons will double, and at the same time, the area of farmland affected by drought across the country may increase by more than 1.5 times.
"More and more meteorological experts have reached a consensus: Although it is not possible to attribute every extreme weather and climate event to climate warming and deduce direct cause and effect, every occurrence of extreme weather and climate event strikes humanity. Sounding the alarm-climate change with global warming as its main feature has brought many impacts and risks to the natural ecological environment and human economy and society, and is one of the most severe challenges facing the world." Chief Climate Service Chief, National Climate Center Expert Zhou Bing said.
The forecast shows that the overall climate situation in the midsummer of this year is deviated, and the vigilance of flood prevention cannot be relaxed
Chen Lijuan introduced that the National Climate Center began rolling forecasts of the flood season climate from February this year. In the rolling forecast opinions in May, the forecast of the climate year was adjusted from "normal to bias" to "bias."
The Midsummer (July-August) forecast information released at the end of June pointed out: “my country’s climate conditions are generally deviated, extreme weather and climate events are more frequent, and droughts and floods are more serious. Northeast, Huanghuai, eastern Jianghuai, northeastern Jiangnan, eastern and northern Southwest China, most of Jianghan and southern South China."
According to Chen Lijuan, according to the forecast of the National Climate Center, the East Asian monsoon circulation system, which affects my country’s weather and climate, will have relatively large phase changes in August, but overall it is still conducive to the presence of two rain belts in the north and south of my country’s precipitation. The western Pacific subtropical high is affected by the phased westward extension and northward movement, while the southern rain belt is mainly affected by the typhoon activity and the phased southward setting of the western Pacific subtropical high.
It is expected that the precipitation in western Xinjiang, Inner Mongolia, Northeast China, North China, eastern Northwest China, northern Huanghuai, Jianghuai, Jiangnan, northern South China and other places will have more precipitation than normal. 2-3 tropical cyclones may land or significantly affect southern and southeastern coastal areas. area.
"The vigilance of flood prevention cannot be relaxed." Chen Lijuan said.
On July 30, the State Key Laboratory of Severe Weather organized a seminar on extreme rainstorms in Henan in July this year.
Yu Rucong, deputy director of the China Meteorological Administration, said at the seminar that it is necessary to continue to organize scientific research to improve forecast accuracy and timeliness, to strengthen the awareness of frequent global extreme weather and climate events, and to improve response capabilities, especially to strengthen the response to disasters. Vigilance of sexual weather.
At present, our country is in a critical period of "seven lower and eight upper" flood control.
Experts suggest that all localities and departments should strengthen overall coordination, strengthen inspections of hidden hazards, strengthen the safety protection of important infrastructure, improve the level of early warning and forecast of rainfall, typhoons, mountain torrents, and mudslides, and pay close attention to various flood prevention and disaster relief measures.
For the public, they should pay attention to weather forecasts and warnings in a timely manner to enhance their awareness and ability in disaster prevention and mitigation.
Our reporter Liu Yi