After the rainstorm is over, is there an end to this year's extreme weather?

New Weekly

2024-06-30 01:03New Weekly official account

Author | Zhang Wenxi

Edit | Zhong Yi  

Title Picture | Visual China

"There is already more rain in Guangzhou than in the tropical rainforest."

There is absolutely no exaggeration in the comments of netizens. In April this year, Guangzhou's precipitation was close to 600 mm, equivalent to Beijing's annual precipitation, surpassing the "world's rain pole" in the same period, and ranking first in the world.

Since June 13, heavy rainfall has caused flooding in 64 counties (cities and districts) in 11 cities in Guangxi. As of 16:00 on the 19th, 431,000 people have been affected. After that, Meizhou City in Guangdong Province also suffered heavy rains, and Pingyuan County experienced flooding.

And the rain does not seem to be willing to stop in Guangdong, to be precise, not in the south.

At 10 o'clock on June 24, the Central Meteorological Observatory issued the first red warning for heavy rain this year. It is predicted that in the coming period, the rainfall in the provinces of Jiangxi, Anhui, Hunan and Hubei in the south and the northern part of Guangxi may exceed that of Guangdong at the peak of rainfall in April. At the same time, the high temperature and drought in the north have also become a new round of suffering for people.

It is only when the weather concretely affects people's lives that people begin to recognize its importance.

Why is there so much rain in the south this year? Why did the northern region suffer from drought during the same period? What kind of complex weather changes may we face in the coming period? With these questions, the reporter of New Weekly chatted with "Chinese meteorological enthusiasts" (hereinafter referred to as Zhongqi Ai).

It rains non-stop in the south, and drought persists in the north.

Why exactly?

Every summer, the weather in the southern part of the continent is affected by the subtropical high. Zhongqiai observed that this year's subtropical high is more southerly and stronger than in the past, and this change is the main reason for the unusually high rain this year.

In April this year, the average precipitation in Guangdong province broke a historical record. (Photo/Guangdong Meteorological Service Center)

In the past, around April every year, South China would start a flood season that lasted for half a year, and the flood season can be divided into the pre-flood season and the post-flood season. Among them, the dragon boat water, which appears from mid to late May to mid-June every year, is one of the landmark events of the pre-flood season, which generally marks the arrival of the most heaviest precipitation period in South China during the year.

However, this year's heavy precipitation in southern China unusually early in April occurred earlier. The unusually sustained heavy precipitation in April and the dragon boat water in May and June seamlessly combined to make the pre-flood season rainfall and rainy duration in South China set a record. "This is inseparable from the fact that this year's subtropical high was unusually strong, and it was significantly southerly in spring, which made the water vapor transported along the edge of the subtropical high stronger, and the cold and warm air masses continued to converge on the north side of the subtropical high, that is, in South China, which eventually led to protracted ultra-long precipitation." Nakaki Ai explained.

And if we change the perspective of observation from a vast space to a long time, we will find that the abnormal rainfall on the mainland may have begun to lay the groundwork as early as last year.

El Niño. (Photo/UN News)

In July 2023, the World Meteorological Organization (WMO) declared El Niño conditions in the tropical Pacific Ocean for the first time in seven years. The so-called El Niño event occurs on average every 2-7 years and usually lasts 9-12 months, during which time ocean surface temperatures warm in the central and eastern tropical Pacific Ocean. El Niño is actually a naturally occurring climate pattern, but climate change caused by human activities may also be the background to its occurrence.

At the time, WMO Secretary-General Talas predicted: "The occurrence of an El Niño event will greatly increase the likelihood of breaking temperature records, and may cause more extreme heat in many parts of the world and in the oceans." "On November 30, 2023, the World Meteorological Organization announced that 2023 was the hottest year on record in human history.

The Kumutag Desert in Shanshan County, Turpan City. On July 16, 2023, the maximum temperature at 31 meteorological observation stations in Turpan City, Xinjiang, reached more than 45°C, and the maximum temperature at 5 stations exceeded 50°C. (Photo/Visual China)

Even though 2023 has passed, the continent and the entire world are still affected by the El Niño phenomenon a year ago.

Zhongqi Ai told the New Weekly reporter that the El Niño phenomenon is essentially a change in the sea surface of the tropical Pacific Ocean surface of the sea surface of the Zonal Ocean, and the change of the sea surface temperature anomaly leads to the occurrence of abnormal low pressure or high pressure over the Pacific Ocean, thus affecting the atmospheric circulation.

"It takes a long time for sea surface temperature to affect the atmosphere, as little as three months, as much as half a year, or even most of the year." The end result is El Niño's "New Year's Eve impact" on continental climate, which began last autumn and continues into this year, peaking in winter 2024 (January-February) and ending in summer 2024 (June-July).

At the end of June, a plum rain belt was distributed in the Yangtze River basin. (Photo/@中国气象爱好者)

"In general, the year following the occurrence of El Niño has two typical consequences for continental climate. First, there is a lot of abnormal rainfall in the southern part of the mainland, especially in the Yangtze River basin. In addition, it will lead to a decrease in typhoon activity in the western Pacific before autumn. ”

On the evening of June 23, the topic "Hangzhou Lingyin Temple Flood" rushed to the hot search on Weibo, and the water level of the West Lake Scenic Area rose, which was described by netizens as "the scene of the White Lady vs. Fahai". Changsha City, Hunan Province, was also hit by heavy rains, with serious water accumulation on many sections of roads and subway stations in the city, and people jokingly said that migrant workers needed to "drive a boat to work".

On June 24, heavy rain suddenly fell in Changsha, and some low-lying areas in the urban area were seriously flooded. (Photo/Network)

However, almost while the south is suffering from rainfall, many places in the northern part of the mainland are experiencing high temperature and drought weather.

During the day on June 19, the highest temperature in some areas of Xinjiang along the Tianshan Mountains, central Shaanxi, and central and southern Hebei reached 37-39°C. Among them, the Henan Provincial Climate Center issued an orange warning for drought at 8 o'clock on June 12: according to the latest meteorological drought monitoring, 72 national meteorological stations in 16 cities in Henan Province have monitored meteorological drought to reach the level of severe drought or above, and have lasted for 10 days. Villagers in Jinkou Village, Zhengzhou City, Henan Province, told the media that they had lived to be 50 years old and had never experienced a drought as severe as this one.

Zhongqi Ai explained that there is relatively little vegetation on the northern land, and there are more deserts and wastelands. Every year when the weather starts to heat up in May, the sun hits these dry surfaces, and the surface temperature rises rapidly, and the hot air rises rapidly, forming a strong continental high pressure. Under the control of the continental high pressure, the weather in the northern region is hot and sunny.

Map of the highest temperature distribution in Henan Province. (Photo/Henan Provincial Meteorological Observatory)

Extreme weather is on the rise,

Maybe it will become an inevitability

With more and more complex and volatile climate events, it is difficult to deny the existence of extreme weather.

In the climatology community, observers and researchers often use the concept of "anomaly" to determine anomalies and extreme weather. To put it simply, an anomaly is the difference between a certain value and the average value, and the larger the difference, the more the current value deviates from the original average.

The heavy rainfall in the southern region, which is much higher than the average average, is a case in point. Many people have the impression that it is normal for the southern region to receive a lot of rainfall. However, in Zhongqiai's view, this year's heavy rainfall in the south is significantly higher than in the past, which can definitely be regarded as an extreme weather.

 (Photo/@中国气象爱好者)

The reason for this is that it came earlier and stronger than before. The main summer precipitation in the southern part of the continent comes from the summer monsoon, which carries water vapor from the sea. Not only the mainland, but also southern Asian countries such as India, Pakistan, Laos, Cambodia, and Myanmar belong to the monsoon climate region.

One of the characteristics of the monsoon climate is that it is "hot and rainy at the same time". Rain and heat at the same time, as the name suggests, rain and heat come together. When the climate is hot, the rain becomes abundant. For many countries in southern Asia, the summer monsoon erupts, usually after mid-May. In April, the summer monsoon has not yet broken out, so the precipitation on the mainland is not very prominent at that time.

However, due to the combined influence of the unusually strong subtropical high and the El Niño phenomenon, the premature arrival of heavy precipitation this year has become an exception to the common sense, breaking the original "rain and heat at the same time" law.

Zhongqiai predicts that there will be some extreme weather that needs to be paid attention to in the mainland this year, including floods caused by heavy rainfall that the northern region may face when the main flood season arrives from July to August, and the high temperature weather in the Yangtze River basin from mid-to-late July to August.

Chongqing in the Yangtze River basin has suffered major floods. (Photo/Visual China)

Extreme weather is on the rise, and it may have become a necessity.

"If you look at the frequency of extreme rainstorms, droughts, high temperatures and other weather on the mainland in the past few decades, you will find that they are becoming more and more frequent," said Zhongqiai, "not necessarily every year, but it will generally be an upward curve." ”

(Photo/"Deadly Weather Forecast")

The small and trivial things in life, food, clothing, shelter and transportation are actually closely related to the larger weather and ocean current system:

Continuous heavy rainfall can cause flooding, resulting in slower crop growth or even crop failure, which may lead to an increase in vegetable prices. For some low-lying and loose areas, heavy rainfall also means the risk of natural disasters such as flash floods, waterlogging, and mudslides. The high temperature and heat will not only affect the rising electricity bills in the summer electricity bill, but also the sanitation workers who sweep the streets, the traffic police on the road, and the workers on scaffolding, who work outdoors for a long time, are more vulnerable to the high temperature.

According to the report "Human Losses from Disasters 2000-2019" released by the United Nations Disaster Prevention and Reduction Agency, due to the impact of global warming, the first 20 years of the 21st century have increased by 232% compared with the previous 20 years, and the number of floods has increased from 1,389 in the previous 20 years to 3,254. In addition, the number of disasters such as droughts, wildfires, and extreme temperatures has increased significantly.

After a rainstorm, a Vietnamese man uses a small boat to drive on the water. (Photo/Visual China)

Global warming affects not just one country, but the whole world.

This year, extreme heat has swept many countries in South Asia, with temperatures reaching as high as 52.9°C in New Delhi, the capital of India, making it the hottest summer in the country in 120 years. Meanwhile, more than 1,300 people have died in Saudi Arabia due to extreme heat during this year's Hajj; Since March, many countries in East Africa have been hit by unprecedented heavy rainfall, causing floods that have displaced hundreds of thousands of people.

It is only at the moment when the weather affects our lives, or we see disasters with our own eyes, that we briefly appreciate the important impact of climate on human beings. After the heat, drought, wildfires and floods have passed, people can no longer pretend that things have passed, nor can they be perfectly invisible in the future of climate change: learning how to live with more and more extreme weather is the harsh reality that modern people must face.

Proofreading: No ginger fish

Operations: Ono

Typesetting: Huang Lu

[1] UN News, WMO: El Niño is shaping in the tropical Pacific

[2] UN News, IOM: Unprecedented floods have displaced hundreds of thousands of people in East Africa

[3] Global Digital Platform for Disasters, https://www.gddat.cn/newGlobalWeb/#/majorDisasterBriefing

[4] Interface News, directly hitting the drought in Henan, villagers: "I have lived for 50 years, and I have never seen such a drought"

[5] UN Report, Human Toll from Disasters 2000-2019

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