Liu Zhao Wang Liang Li Yue

  This summer, "hot" is undoubtedly the most concerned keyword.

Since June, high temperatures have continued in many parts of the country.

Looking at the world, extreme weather and climate events represented by high temperatures in the northern hemisphere are also emerging one after another.

  In my country, in June, the high temperature was "earning the first" in the north, and many places issued high temperature red warnings.

After entering July, the high temperature in the south "came from behind" and started a long "barbecue" mode.

Up to now, the southern heat has not yet exited, and it is even worsening.

Although the high temperature in Beijing this summer does not seem to be extreme, the number of high temperature days (daily maximum temperature ≥35°C) has been as many as 15 days so far, which is significantly more than the 9.7 days in the same period of the year.

  The highest comprehensive intensity of high temperature events since 1961

  How hot is this summer?

Since June (June 1-August 14), the national average number of high temperature days has been 11.8 days, 4.9 days more than the same period of normal years, the highest in history since 1961.

  Zhou Bing, chief expert of climate services at the National Climate Center, introduced that the regional high temperature weather in my country since June 13 has the characteristics of long duration, wide range, high intensity, and strong extremes.

  From June 13 to August 14, my country's regional high temperature process has continued for 63 days, including Hubei Zhushan (44.6 ℃), Chongqing Beibei (44.5 ℃), Hebei Lingshou (44.2 ℃), Gaocheng (44.1 ℃) , Zhengding (44.0℃) and Yunnan Yanjin (44.0℃), the daily maximum temperature reached 44℃ and above, covering an area of ​​more than 5 million square kilometers and affecting a population of more than 900 million people.

  This year's high temperature event is extremely rare in a sense. Compared with several high temperature events since this century, the start time is significantly earlier and the extreme is significantly enhanced.

Combined with the regional high temperature process monitoring indicators of the National Climate Center, and combined with the intensity, influence range and duration of high temperature events, the comprehensive intensity of high temperature events this year is the strongest since 1961.

  Under the high temperature, the five provinces of Jiangsu, Henan, Anhui, Zhejiang and Sichuan have the highest number of high-temperature days in the same period since 1961.

The daily maximum temperature of 716 national meteorological observation stations across the country reached the extreme high temperature event standard, and the daily maximum temperature of 133 national meteorological observation stations in Hebei, Shaanxi, Sichuan, Zhejiang, Fujian, Guangdong and other places remained the same or exceeded historical extremes.

The temperature at Shanghai Xujiahui Station reached 40.9°C at 14:30 on July 13, tying the highest temperature record since the local meteorological record (1873).

  The continuous high temperature has adversely affected the production activities and people's health in many places.

Since June 13, the power load of Hebei, Shandong, Zhejiang, Henan, Shaanxi, Gansu, Ningxia, Xinjiang and other provinces (autonomous regions), as well as the Northwest Power Grid and the Southern Power Grid, have reached record highs. It increased by 33.56% last year; many people in Zhejiang, Jiangsu, Sichuan and other places were diagnosed with heat stroke. From July 1 to 14, Shenzhen 120 received a total of 73 heatstroke emergency alarms; eastern Zhejiang, western Henan, southern Shaanxi, southern Gansu, In northern Sichuan and other places, due to the deviation of soil moisture due to high temperature and little rainfall, meteorological drought continued or developed in some areas.

  Up to now, the southern heat has not yet exited, and it is even worsening.

  The Central Meteorological Observatory continued to issue a high temperature red warning at 6:00 on August 16, which was the 27th consecutive day that the Central Meteorological Observatory issued a high temperature warning.

The forecast shows that in the next 10 days, there will still be persistent high temperature weather in Sichuan Basin, Jianghan, Jianghuai, Jiangnan and other places, and the cumulative number of high temperature days will reach 7 to 10 days; 40°C.

  Beijing's high temperature this summer is not extreme, but there are many days

  "Beijing doesn't seem to be so hot this year." For Beijing residents, this year's high temperature seems to be relatively ordinary.

  The data proves that Beijing is indeed "not so hot" this summer, and there is no particularly extreme high temperature.

Since the flood season this year (June 1 to August 15), the average temperature in Beijing has been 25.5 ℃, which is slightly higher than the same period of the year (25.0 ℃).

However, it should be noted that the number of high temperature days in Beijing is as high as 15 days, which is significantly more than 9.7 days in the same period of the year.

  The high temperature in Beijing this year is not too late.

On May 28, the highest temperature during the day at the Southern Suburb Observatory, which represents the "Beijing temperature", rose to 35.3°C. The first high temperature day this summer was born, 13 days earlier than normal.

The high temperature came early, but the follow-up development is not extreme. Shi Hongbo, deputy director of the Beijing Climate Center, introduced that the extreme high temperature since the flood season this year was 39.2 ℃, which appeared on June 25.

In history, the extreme maximum temperature in summer has exceeded 39.2 ℃ in 13 years, and even reached 41.9 ℃ in 1999.

Compared with these years, this year's highest temperature is still normal.

  The reason why the high temperature in Beijing is not extreme is the trend of high pressure.

"During the continuous high temperature weather in Beijing in the early part of this year, the continental high pressure ridge was westward, at the junction of Xinjiang and Inner Mongolia, and there was a trough over the northeast region. Beijing was just at the boundary of the high pressure ridge and the low trough, and at the edge of the high pressure range, so it was affected by high pressure. The impact is relatively small." Shi Hongbo said.

  After entering August, Beijing ushered in a period of "sauna days", with high temperature and high humidity, and the public felt unbearably hot.

Shi Hongbo introduced that the main flood season of Beijing's "seven down and eight up" (ie from late July to early August) happens to be the period when water vapor is relatively abundant throughout the year.

Recently, with the northward lift of the subtropical high in the western Pacific, the humidity in Beijing has increased, and the air flow has subsided, which has led to an obvious warming effect, triggering a sultry weather with high temperature and high humidity.

The actual temperature of this kind of weather is generally not very high, but when it is combined with the humidity, it will increase the sultry feeling and make people sweat.

In the absence of precipitation, the weather will remain stable in this state.

This is also the normal state of Beijing's climate, which is a normal phenomenon.

  Shi Hongbo also reminded the public that the summer is not over yet, and the vigilance against the high temperature cannot be relaxed.

From the perspective of the midsummer stage (July to August), as of August 15, there have been 10 high-temperature days in Beijing, and now that August has not ended, high-temperature days may still occur.

"The average number of high temperature days from July to August in previous years was 6.1 days. From the historical data, it was 15 days in 2000, 14 days in 2010, 13 days in 1999, and 12 days in 1997. From the data of recent years There are 11 days in 2017 and 10 days in 2018." Shi Hongbo said that the possibility of a temperature higher than 39.2 °C in the later period is very small, but the number of high temperature days may increase.

  Sustained heat event ravages the entire northern hemisphere

  The world is also hot and cold, and the high temperature is not only raging in the country, but has formed a "warm atmosphere" in the entire northern hemisphere.

  The UK, which has always been cool, issued the first ever red warning for abnormally high temperatures on July 15.

Four days later, on July 19, local time, the highest temperature in the UK exceeded 40°C for the first time in history.

Several fires broke out in London that day, and the fire department announced a "major incident".

Previously, the highest temperature ever recorded in the UK was 38.7°C, which was measured at Cambridge University Botanic Gardens on July 25, 2019.

  In southern Europe, high temperatures and heat waves have sparked raging wildfires. The French and Spanish governments on July 17 deployed more than 1,000 firefighters to try to control the spread of the fires.

The Greek fire department also pointed out that 71 wildfires broke out in the local area in 24 hours.

French President Emmanuel Macron said that three times as much forest land has been burned this year as in 2020. "We are going through an exceptionally difficult summer."

  The impact of high temperature in Japan is equally serious.

According to the Japan Meteorological Agency, at 14:30 local time on August 11, a high temperature of 40.5°C was observed in Isesaki City, Gunma Prefecture, Japan, the highest in Japan this year.

In addition, a high temperature of 39.3 ℃ was also observed in Hachioji City, Tokyo.

From August 1st to 10th alone, five elderly people aged 70 to 80 died of heatstroke in Tokyo.

  Even the cold Arctic Circle cannot escape the effects of high temperatures.

CNN reporter Rene Marsh recently appeared in the news about Greenland wearing short sleeves.

She said in the video that the temperature in Greenland is close to 60 degrees Fahrenheit (about 15.5 degrees Celsius), and the weather like this is warm enough to wear short sleeves.

Greenland's ice sheet is melting at an alarming rate due to rising temperatures, René Marsh said.

  In June this year, the global average temperature was about 0.4°C higher than normal, the highest since 1979.

In the northern hemisphere, Western Europe, Southern Europe, West Asia, Central Asia, East Asia, the United States, Africa and other places have successively experienced continuous high temperature events, and high temperatures of over 40°C have occurred in Spain, Portugal, France, the United Kingdom and other places; in July, the temperature of the Arctic Circle once soared to 32.5 °C.

  World Meteorological Organization (WMO) Secretary-General Pettieri Talas pointed out on July 19 that in addition to seriously affecting human health, extreme high temperature weather will have a further negative impact on agricultural activities, exacerbating the current situation caused by the conflict between Russia and Ukraine. Serious crop yield reduction.

  Three reasons cause the weather "high fever" to persist

  Frequent heat waves, "high fever" does not go away, what is the reason?

Zhou Bing believes that there are three levels of causes of extreme high temperature in the northern hemisphere: the abnormal atmospheric circulation creates the basic conditions for high temperature; the "La Nina" event adds fuel to the flames and makes the high temperature "a higher level"; global warming further amplifies the impact of high temperature.

  The so-called atmospheric circulation anomaly refers to the degree of deviation between the atmospheric circulation situation in different seasonal processes and geographical space operations and the annual climate average.

If the degree of deviation exceeds a threshold (such as 1 or 2 standard deviations), it can be considered that there is an abnormal atmospheric circulation.

For example, when the originally straight east-west circulation turns into a zigzag north-south circulation, it can be considered that the atmospheric circulation is abnormal.

  This summer, the atmospheric circulation system in the northern hemisphere appeared abnormal, showing a consistent control state of the warm high-pressure circulation system.

Warm high pressure is an important source of high temperature. Under the influence of the high pressure system, the hot air stays near the ground and cannot be blown away or dissipated, causing the local area to continue to heat up.

In the northern hemisphere this summer, the western Pacific subtropical high, the Atlantic subtropical high and the Iranian high have all strengthened in stages, forming a large-scale overall global warm high pressure belt.

  At the same time, the "La Niña" climate event spanning three years has contributed to the anomaly of atmospheric circulation.

"La Niña" refers to the abnormal cooling of the water in the central and eastern Pacific Ocean, which will lead to the strengthening of the tropical latitudinal circulation and trigger the gear effect of the latitudinal secondary circulation.

Since this spring, the "La Niña" event has not weakened, but has continued to intensify. During this time, the sea temperature in the Indian Ocean has also been relatively abnormal, both of which have contributed to the continuous strengthening of the western Pacific subtropical high.

  What cannot be ignored is the ubiquitous impact of global warming.

In this high temperature process throughout the northern hemisphere, it has played a role in the amplification and modulation of warming.

Under the background of global warming, the instability of the global climate system has intensified, and extreme weather and climate events have occurred frequently, widely, strongly and concurrently. strong.

  Global warming effects go from "behind the scenes" to "front stage"

  Extreme heat events are the weather phenomena most easily associated with global warming, but they are far from the only impact of global warming.

Today, global warming has moved from "behind the scenes" to "front stage".

Carbon emissions are well-recognized as a major contributor to global warming, and record concentrations of greenhouse gases are driving up temperatures and making weather more extreme.

  In addition to high temperatures and heat waves, global warming will bring more heavy rainfall and floods.

Data show that for every 1°C rise in global temperature, atmospheric water vapor will increase by about 7%, increasing the probability of extreme precipitation.

Rising temperatures will also lead to melting glaciers, land drought, desertification, accelerated water evaporation and soil erosion, and ultimately more extreme weather.

  The effects of global warming are increasingly being felt: Arctic sea ice is shrinking, Greenland ice sheet melting is accelerating, fires and insect infestations have begun in the boreal forests of North America, Russian permafrost in the Northern Hemisphere Unblocking begins, the meridional overturning current in the Atlantic Ocean begins to slow down, the Amazon rainforest reduces rainfall and causes frequent droughts, Australia's warm water corals begin to die, the melting rate of the West Antarctic Ice Sheet is accelerating, and the Wilkes Land Ice Sheet in the East Antarctic Accelerating melting... In the face of these phenomena, people cannot ignore the "red alert for all mankind" issued by the Intergovernmental Panel on Climate Change (IPCC) and the World Meteorological Organization's warning that human beings need to face" A hotter, drier, more flooded future."

  Faced with more severe climate challenges, people need to be fully aware of the potential crisis and take practical action.

Finding breakthroughs in reducing greenhouse gas emissions is the only way to meet the challenge.

(Thanks to China Meteorological News for the support of this article)