Zero distance
Frequent extreme weather causes global warming to worsen
The extreme weather disasters in the past few days have touched people's hearts.
Since July 17th, Henan has experienced extremely heavy rains that are rare in history. Among them, Zhengzhou, Hebi, and Xinxiang local areas have exceeded 900 mm. The daily rainfall of more than 10 national meteorological observatories has reached the historical extreme value since meteorological observation records. At 12 o'clock on July 26, this round of heavy rains caused 12,907,400 people in Henan Province to be affected, and 69 people died from the disaster. At the same time, the Central Meteorological Observatory issued high temperature warnings for 8 consecutive days, and the south and northwest were "hot purple". ; On July 18, typhoon "Fireworks" was generated, and "Chapaka" followed closely, disturbing coastal areas.
Looking at the world, sudden heavy rains in Western Europe caused floods, killing more than 200 people; historical high temperatures swept North America, killing hundreds of people; coupled with previous super cold waves, extreme sand and dust, tornadoes, and rare weather events hit one after another. These all point to a key word: extreme weather.
As a result, people’s concern is not just "how long will it rain" and "when will they see the sun", but also want to understand how much human weather can play in the face of extreme weather, and it is difficult to warn of extreme weather forecasts. Where, what is the "pushing hand" behind the frequent occurrence of extreme weather, and how should people deal with it?
The reporter interviewed relevant experts from the China Meteorological Administration.
Forecast of extreme rainstorms is a problem in the world
It was the first time to learn about the heavy rain in Henan in July. Luo Yali, a researcher at the Chinese Academy of Meteorological Sciences, was at a review meeting. This explosive news quickly became a new topic among the scientists present.
According to statistics from the China Meteorological Administration, the precipitation at the National Basic Meteorological Station in Zhengzhou, Henan Province from 16:00 to 17:00 on July 20, accounted for almost 1/3 of the total annual rainfall in Zhengzhou-640.8 mm.
"Such hourly rain intensity is extremely extreme in the world, and it is extremely harmful. It is almost inevitable that secondary meteorological disasters such as urban waterlogging will occur." Luo Yali said.
Chen Tao, the chief forecaster of the Central Meteorological Observatory, said that since July 17, the heavy rainfall in Henan has accumulated a large amount of rainfall, a long duration, and concentrated precipitation areas. The extreme features of hourly rainfall are also very obvious.
Among them, the record of 201.9 millimeters in one hour exceeds the extreme value of hourly rainfall since the meteorological record in mainland China.
Why is there such a strong rainfall?
For weather forecasters and meteorological researchers, the major factors that contributed to the heavy rainfall in Henan are relatively clear: the western Pacific subtropical high and the continental high were maintained stably, and the typhoon "fireworks" that is still on the ocean is moving forward. In the process of approaching, our country transports abundant water vapor, coupled with the influence of the special terrain of the Taihang Mountains and Funiu Mountains, and the obvious convective "train effect", and so on.
It is also based on the comprehensive judgment of these phenomena and historical data that meteorologists can continuously release familiar weather forecasts and rainstorm warnings to the outside world.
Chen Tao said, however, this type of weather forecast can only predict the possible range of strong local weather in advance, and cannot predict the exact location of its occurrence in advance.
For this reason, the term "local" often appears in rainstorm forecasts.
The delineation of heavy rain in the meteorological circle is based on the standard that the total rainfall reaches or exceeds 50 mm in 24 hours.
However, whether the rainstorm is evenly finished within 24 hours or poured down in a short period of time, which not only gives the public a different perception, but also has different impacts on social operation and safety production. The rainstorm is increasingly "growing and expanding". Cities, or fragile villages, can also lead to a completely different situation.
"From the perspective of weather, a very heavy rainstorm must not only have very abundant water vapor, but also have a strong vertical upward movement to turn the water vapor into large water droplets and fall down, and it must be coordinated with various weather conditions around it." Li Zechun, academician of the Chinese Academy of Engineering Say.
From August 5th to 8th, 1975, Typhoon "7503" passed through Fujian, Jiangxi, and Hunan, then went northward, passed through Hubei, and stagnated in Henan, resulting in a rare heavy rain and flood in history-1631 in southern Henan within 3 days. Total rainfall in millimeters.
About a month after the heavy rain, Li Zechun, then head of the forecast team of the Central Meteorological Observatory, went to Henan Banqiao Reservoir and other disaster-stricken areas and found that the scene was still horrible.
He said that in recent years, my country's heavy rain research and forecasting have made continuous progress, but the chaotic nature of atmospheric motion determines that weather forecasts will inevitably have a certain degree of error. At the same time, heavy rains are changeable due to their locality, suddenness and activity patterns. The formation mechanism has not been thoroughly studied so far, and it is still a difficult problem in the meteorological field all over the world.
"It is even more difficult to catch the extreme rainstorm of more than 200 millimeters in one hour." Li Zechun said.
A set of templates is difficult to "apply" different extreme events
The different types of rainstorms also aggravated the difficulty of forecasting.
"There are frequent heavy rains in our country, but it is difficult to'apply' every extreme event with a set of established templates. It is the so-called one type of screw with a wrench." Luo Yali said.
According to her, different types of torrential rains often occur in different regions of my country, such as torrential rains in the first flood season in South China, torrential rains in the Meiyu front in the Jianghuai River Basin, torrential rains in the southwest vortex, torrential rains in the North China trough and vortex, torrential rains in the northeast cold vortex, and coastal typhoon rains.
The locations of frequent torrential rains are closely related to the location and duration of the main rain belt of the summer monsoon.
"Compared with other countries in the same climate zone, the intensity of heavy rains in my country is very high, and the extreme values of heavy rains of different lengths of time are very high." Luo Yali said that before the extreme value of Zhengzhou Station this year, the one-hour precipitation extreme value was 1975. During the "75·8" rainstorm, 198.3 mm in Linzhuang, Henan, the 24-hour precipitation extreme value was 1,248 mm in Taiwan on September 10, 1963.
These values are "countable" in the world.
Li Zechun introduced that the main means of forecasting heavy rains in my country is to use numerical weather forecast model products and combine the knowledge and experience of the forecasters themselves.
In recent years, although the resolution of numerical weather prediction models has gradually increased, generally speaking, the probability of extreme events is very small.
He told reporters that although the general circulation situation is stable and clear when some extreme rainstorms occur, there are also small and medium-scale convective systems that are at work. The scale may only be one or two hundred kilometers, and the life cycle is only a few hours. The current value It is difficult to "exactly and clearly express" the forecast model.
Lan Yuzeng, deputy director of the Strong Weather Forecast Center of the Central Meteorological Observatory, said: This is like fishing with a net. If the mesh is too large, a small-scale weather system will inevitably become a fish that slips through the net.
Li Zechun said that the most fundamental way to tackle the problem of heavy rain forecasting is to strengthen the precise monitoring of atmospheric changes and improve the accuracy of numerical forecasts.
He also mentioned that the improvement of the numerical model cannot be achieved overnight. Another focus on the accurate improvement of the rainstorm forecasting ability and the fine service is placed on the forecasters like Chen Tao who have been "nailed" to the duty room for a long time.
Chen Tao believes that it is necessary to have a keen and profound insight into the process of rainstorm formation, analyze and forecast key impact systems from massive observations and forecast information, and its correlation with the time, location and precipitation of future rainstorms, so as to detect weather system forecast deviations early. And so on, in order to finally form a forecast of the major rainstorm process.
Li Zechun is also very concerned about science popularization for the public and decision makers. Disaster prevention and mitigation cannot do without weather, and the people cannot do without weather.
"I hope to strengthen the awareness of disaster prevention and mitigation and improve the ability of decision makers, to have a deeper understanding of how to make rainstorm forecasts, where the difficulty is, and how high the risks are, and to make better use of weather forecasts and warnings to make preparations and arrangements." Li Zechun said.
What's wrong with active extreme weather
On the one hand, human beings are pursuing the accuracy of extreme weather forecasting, and on the other hand, they are also reflecting on why so many extreme weather have appeared in recent years, and how to avoid and reduce abnormal weather?
Regarding this issue, meteorological experts at home and abroad have actually concluded that in the context of global warming, the frequency of extreme weather will increase.
Jia Xiaolong, deputy director of the National Climate Center, said that global warming has exacerbated the instability of the climate system and is the root cause of the frequent and increased intensity of extreme weather and climate events.
He further explained: As the climate warms, the atmosphere can hold more water vapor before it is saturated, so the possibility of extreme heavy precipitation increases.
The recent severe floods in Western Europe and the extreme rainstorms in Henan in my country are all concrete manifestations of the frequent occurrence of extreme heavy rainfall events.
Since 1990, the China Meteorological Administration has conducted greenhouse gas monitoring in Wariguan, Qinghai, my country.
Monitoring results show that the concentration of greenhouse gases in the atmosphere continues to increase, indicating that greenhouse gases emitted by human activities are still increasing.
Greenhouse gases mainly include carbon dioxide, methane, nitrous oxide, sulfur hexafluoride, hydrofluorocarbons, perfluorocarbons), nitrogen trifluoride, and ozone depletion restricted by the Montreal Protocol. substance.
"Greenhouse gas emissions have been repeatedly proven to be the main feature of global climate change in the past 100 years, and the direct cause or main cause of climate change." said Song Shanyun, a spokesperson for the China Meteorological Administration, which brought the development of human society. Many risks and challenges.
Zhang Xiaoyi, an academician of the Chinese Academy of Engineering, explained that the uniform scale of climate change is to look at the 30-year average temperature change. At present, people can see an obvious warming trend line.
Global warming does not necessarily mean "this year is a warm year", but with the warming of the average climate, extreme weather events that did not occur frequently have followed.
Faced with this situation, one of the key measures for mankind is to reduce emissions-reduce greenhouse gas emissions.
In September 2020, my country clearly put forward the carbon peak and carbon neutral goals, and made efforts in tackling climate change and implementing the Paris Agreement to control greenhouse gas emissions.
"To reduce emissions, we must accurately know the emission situation and distinguish between natural emissions and emissions generated by human activities, so that we can test the effect of emission reduction and the effect of emission reduction." Song Shanyun said.
Not long ago, the China Meteorological Administration released the latest China Greenhouse Gas Bulletin, which echoes the Greenhouse Gas Bulletin issued by the World Meteorological Organization in November 2020.
The results show that the global carbon dioxide concentration continues to rise.
Zhang Xiaoyi said that before the industrial revolution, the concentration of carbon dioxide in the earth's atmosphere was around 280ppm. The temperature of the earth produced by this concentration was suitable for human habitation.
Later, this concentration became higher and higher. In the 1980s, the concentration of atmospheric carbon dioxide was around 340 ppm, and in 2020, the highest concentration has reached 417 ppm.
"Human carbon neutralization has a long way to go." Zhang Xiaoyi said.
China Youth Daily·China Youth Daily reporter Qiu Chenhui