Shulou(Shulou.com)11/24 Report--

This article is from the official account of Wechat: Earth knowledge Bureau (ID:diqiuzhishiju), author: middle-aged Victor, Cartography: sun Lu / Editor: Yoledo

The original title: "just now, the sandstorm is coming!" "

Affected by the first cold wave since the Beginning of Spring this year, northern China will experience a strong sandstorm. At present, the Beijing Meteorological Observatory has issued a blue warning signal for sand and dust. It is expected that there will be sand and dust weather from 14:00 to 23 on the 10th, and the concentration of PM10 in Beijing will rise significantly.

Why is Beijing so different when it is also in March?

(shooting in the same place) ▼

Among them, the period from evening to midnight is the transit period of sand and dust. Affected by the sand and dust weather, the air quality in Beijing is expected to reach a moderate to severe level tonight, and the concentration of PM10 is expected to exceed 500ug / m3. Due to the strong northwest cold high pressure and strong northwest wind, it is expected that the sand and dust will gradually move out of Beijing in the early morning of the 11th.

Thank you. The meter has already exploded.

(figure: air-matters) ▼

In addition to Beijing, a yellow sandstorm warning has been issued in northern Hebei, west-west, north-by-north and central-north of Inner Mongolia. Sandstorms with visibility of less than 1000 meters are expected in these areas, and sandstorms have already occurred in some areas and may continue.

The rout of North China and Inner Mongolia

(figure: air-quality) ▼

This kind of weather is the best way to save the world. (photo: network) ▼

Warm Tip: we have a discussion group on marine meteorology and geography. If you are a researcher or enthusiast of oceanography, meteorology and physical geography, don't miss the way to add groups at the end of the article!

Where the sand comes from is not a new thing that appeared in modern times. It was recorded in the Book of Han Dynasty: "in summer April, there is four clogs of yellow fog. Bo asked the public secretary and doctor, there is nothing taboo."

In the frontier fortress poems of the Tang Dynasty, sandstorm has become an important image to describe the harsh environment of the frontier fortress area. When in high spirits, such as "the desert wind and dust is dim, the red flag is half rolled out of the gate." the former army night war Tao Hebei, has been reported to have captured Guhun. " There is no doubt that the fiery heroism is revealed; when homesickness is eager, the climate becomes cold after getting out of the plug and then entering the plug, and the customs inside and outside the pass are full of yellow grass. The heroes of Hebei and Shanxi have all been old in sand and dust since ancient times. " The pale helplessness will stop.

The ancient frontier fortress is difficult.

To the north is the Great Gobi of the Mongolian Plateau and to the west is the Great Desert of the Western region.

The spring breeze is so short that it blows sand every day.

(figure: March 9, NASA-2013) ▼

The "abnormal" weather phenomenon can always arouse all kinds of emotions that are not easily expressed in the viewer's heart, and how similar the ancient immortal poems are to today's immortal circle of friends. It can be seen that sandstorm is not a rare weather phenomenon in China's border areas since ancient times, and our nation has been feeling about it for thousands of years.

One thing that has not changed for thousands of years is that sandstorms only favor northerners because their formation requires three elements-sand sources, unstable atmospheric circulation and strong winds.

The wind is blowing, and I can't recognize where the next picture is.

(figure: may 11, NASA-2011) ▼

Once the three are available at the same time, strong winds will pick up a large amount of dust from the ground, where the dust passes through, the air becomes dirty and horizontal visibility decreases significantly. The unstable atmospheric circulation allows the dust to be carried further away by strong winds, otherwise the dust will be weakened and blocked more quickly, and it will never allow a small half of China to fall.

I thought this was an inland satellite map, but I didn't expect it to be coastal.

Unfortunately, that's all I can find.

Ladies and gentlemen, Leeuwenhoek, can you find more cities?

(figure: March 20, NASA-2010) ▼

The term "sandstorm" in everyday language actually refers to sandstorm. The sand and dust weather is divided into five grades according to the standards of visibility, air turbidity and wind power, which are floating dust, blowing sand, sandstorm, severe sandstorm and extra-severe sandstorm. This sandstorm is a severe sandstorm that occurs once in a decade.

It is precisely because of a variety of factors that dust storms usually occur suddenly and only last for a relatively short period of time. Although the time is short, it can bring great harm, which is a kind of disastrous weather phenomenon.

Animals are not immune.

The sand source of the dust weather in Beijing comes from southern Mongolia, which is part of a huge desert with an area of 1.3 million square kilometers (the other part is in China). It spans East Gobi, Central Gobi, South Gobi and Gobi Altai provinces. Just as the ancient Chinese Zhongjiang refers to the Yangtze River and the river refers to the Yellow River, the name of this desert is also very straightforward, which is called the Gobi Desert, which is the "desert" that divides Mobei Mongolia and Monan Mongolia.

This is a fairly vast desert area.

When the wind blows, the radiation range of the wind-blown sand will be larger and larger, ▼.

At present, Mongolia's national capacity is not enough to deal with illegal coal mining and overgrazing, so that the capital Ulaanbaatar is no longer an imagined tranquil Mobei paradise. It is a bloated city suffering from false urbanization and air pollution. It is even more impossible to carry out effective comprehensive management of such a vast and arid sand sea. The Gobi Desert has naturally become an inexhaustible source of sand and dust storms.

Northern Mongolia, where Ulaanbaatar is located, is already a relatively humid area.

Further north is the wetter forest.

To the south, there is a gradual transition from the grassland to the vast desert.

In fact, the area most seriously affected by this round of sand and dust weather is not Beijing, but Mongolia abroad, which has caused several deaths and dozens of missing people.

In China, it is around the Ciwan of the Yellow River, that is, Bayannur and Hubao-Hubei in Ningxia and Inner Mongolia. It is not only affected by the sand source of Mongolia, but also surrounded by four of China's eight major deserts, such as the Badain Jaran Desert, the Tengger Desert and the Maowusu Sandy Land. However, limited by the size of the population and economic and political status, it often does not attract the attention of people outside the region.

This is the area.

It can be said that it is at the forefront of preventing desertification in China, and it is very important.

(base ©2008-2019 Chelys srl) ▼

The public welfare forest donated by the Earth knowledge Hu Bureau was also built in this area.

How does the wind and sand come in autumn and winter? the mainland cools quickly and the ocean cools slowly. the temperature of the continent will be lower than that of the ocean, and so will the air near the ground. Eurasia, as the largest continent in the world, the difference in thermodynamic properties between land and sea is particularly obvious. In the north or north of Mongolia at high latitudes in the interior of Asia, the air is particularly cold and dense, which naturally spreads to the surrounding areas with higher temperature and lower density. As a result, there is a clockwise rotating air mass with a range of thousands of kilometers, which is the Mongolia-Siberian cold high pressure.

You are the most conspicuous.

(figure: wikipedia@Sinysee) ▼

When the high pressure is generated, it will move to the southeast, bringing strong winds and cooling, making eastern Asia colder in winter than other parts of the same latitude. In the process of high-pressure cold air mass "rolling over" the warm air mass to the south, the atmospheric circulation becomes unstable, so sandstorms occur frequently in autumn. In winter, northern China has been controlled by cold air masses, and the south is too far from the sand source, so although cold northerly winds blow in winter, sand and dust weather is rarely seen.

Although there is no dust, the southward movement of the polar vortex is still very scary.

Various disasters caused by climate change are becoming more and more obvious.

(Super cold wave map at the beginning of this year: central Meteorological Observatory) ▼

After the original high pressure moved southward, Siberia will generate a new high pressure again and again, bringing a round of cold wave because the difference in thermal properties between land and sea has not been reversed. When spring comes and the solar direct point is about to move northward to the Northern Hemisphere, the Northern Hemisphere receives more and more solar energy, bringing about the northward shift of the wind belt of atmospheric pressure. At this time, the cold air mass and the warm air mass rise one after another, and the warm air mass in the south goes northward again and meets the cold air mass in the south again, and the atmospheric circulation becomes unstable.

Early January (top) and early March (bottom)

The cold air retreated to the north

But the desert from northern China to Mongolia has also become a front ▼.

Therefore, the sand and dust weather in northern China often begins in mid-late February, and enters a high incidence period after March, and April is usually the peak of sand and dust weather. In May, there are more and more areas controlled by warm air masses, more and more northward, while cold air masses become very weak, and the frequency of sand and dust weather begins to decline.

▼

For example, during the dust weather in March 2021, the cold air going south was very strong, with strong winds of 20 meters per second in Mongolia and dust of large and small sizes when passing through the Gobi Desert. Dust is rolled up from sand with a diameter of 5-0.05 mm to dust less than 0.05 mm in diameter. Under the influence of gravity, surface buildings and vegetation, the sand with larger diameter falls quickly, and the dust continues to invade south with the wind.

After the cold air mass arrived in China, it gradually squeezed the southern warm air mass and the "sun-heated" cold air mass to a generation along the Yangtze River, and the dust from Mongolia was blown to Beijing. Because of the nearby sand source, the periphery of Ciziwan of the Yellow River shows a strong sandstorm, while Beijing and other cities in North China, whose visibility is between 500 meters and 1,000 meters, have also reached the level of sandstorm.

At present, the intensity of the sand and dust weather is not as strong as that of the year before last, but the causes are similar. The recent significant warming of temperature has led to the thawing of sand sources and increased the particles that can be carried by cold air to a certain extent.

The temperature rebounded and the flowers blossomed, and the sandstorm came to ▼.

▼

Is sand control useful for many years? in fact, sandstorms in Beijing were more serious in the past.

Under the influence of unreasonable development, the sandstorm weather in Beijing set a record of 20 days by 1966. At that time, the nearest sand source to Beijing was Saihanba in Chengde, Hebei Province, only 180 kilometers away, so the sandstorm in Beijing at that time was a real sandstorm that could be chewed into the mouth.

Today, the environment of Chengde Saihan Dam is much better than it used to be.

Wind and sand is still frequent in the 1970s, in order to change this environmental problem, the three-north shelterbelt project was officially launched in 1979. The project, which starts from the Uzbek Mountain pass in Xinjiang in the west and reaches Binxian County in Heilongjiang Province in the east, is divided into three stages and eight phases, with a planned afforestation of 534 million mu, which is expected to be officially completed by 2050.

The scope of the three-north shelterbelt project roughly corresponds to the area of wind-blown sand belt in China.

(slide to the right, the approximate scope of the three-north shelterbelt project) ▼

The root system of plants can fix the soil and gravel, reduce the source of sand, slow down the north wind, filter sand, and reduce the intensity and frequency of sandstorms.

Now the construction of the three-north shelterbelt has achieved initial results, the sand and dust has become denser and thicker, and the shelterbelt has been significantly weakened and filtered, so that the number of sandstorm days in Beijing each year in recent years has indeed shown a trend of fluctuation and decline. From 5.3 days and 6.6 hours in the 1960s to 0.9 days in the 1980s and 0.72 hours in 5 years, and then to 0.1 days in the 2010s. Not only in Beijing, but also across the country, the number of sand and dust weather dropped to 2011-2019, with an average of 11.4 times a year.

Of course, the construction of shelterbelts does not mean planting trees in a wide range.

The most serious desertification in the north is actually the former grassland.

And the grassland ecology and desert ecology are quite fragile.

In addition to planting trees, how to gradually restore the desertified grassland is the root of the problem.

The protective forest is indeed effective in resisting sandstorms, but it can not put an end to the windy and sandy weather. Because the height of the sand in the dust is usually only 40 centimeters, the surface vegetation can well block and filter. But the light dust can be blown very high by the updraft, even into the stratosphere about 5000 meters above the ground, the role of vegetation is very limited.

The Siberian high pressure in autumn and winter will not disappear, and strong winds and unstable atmospheric circulation will not disappear. In order to solve the problem of sand and dust weather completely, we can only solve the source of sand and dust storm, but this is also not realistic.

Controlling the source of sand is fundamental, but it is also the most difficult.

(Horqin Ta Min Chagan Desert, Empress Dowager Xiaozhuang is very sad)

Preventing wind and fixing sand requires both cost and natural conditions. Afforestation can turn the Saihanba, which has an annual precipitation of 490 mm, into a forest, and gradually restore the desertified grassland into green space. But for areas where the area is too large, too far away from the sea, and large evaporation, it is a question whether plants can survive after planting.

But also carry out agricultural development.

There is often little water left outside agriculture.

(West Liao River Basin, figure: google map) ▼

After paying attention to environmental protection and environmental control for many years, the annual rainfall in Northwest China shows a fluctuating upward trend, but its rising range is very small, with an average increase of only 0.11 mm per decade, and the precipitation in some areas even shows a slight downward trend. The work of wind prevention and sand control in Northwest China is still not simple.

The precipitation in the eastern part of Inner Mongolia can still support the grassland of considerable scale.

It gets worse and worse in the west.

The integration of the vast desert with Mongolia's Gobi province can only curb its expansion of ▼.

A more embarrassing problem is that the most important source of sand is in Mongolia. China is obviously unable to directly extend the three-north shelterbelt to other countries and can only rely on international cooperation, while the Gobi Desert has been in a bad environment since ancient times, and the cost of transformation is probably huge. And the outcome is unpredictable.

Therefore, sandstorms in Beijing may become history in the future, but the weather of blowing sand and floating dust is unlikely to disappear. It is better to face these natural phenomena with a different state of mind, thinking of the dust flying 5000 meters through the wilderness, farmland and cities, and finally landing in the sea, becoming gluttonous nutrients for plankton, and eventually nourishing the whole ocean with the food chain. Sand and dust has become romantic.

After all, sandstorms are also part of the meteorological system of East Asia.

The formation of the Loess Plateau and the North China Plain both benefited from this.

We should not only solve the problem, but also adapt to the environment.

(figure: NASA) ▼

References:

1. Huang Xiaoyan, Wang Shengjie, Wang Xiaoping. Variation characteristics of atmospheric precipitable water in Northwest China from 1960 to 2015 [J]. Meteorology, 2018 VAT 1191-1199.

two。 Wang Biao, Zeng Xinmin, Liu Zhengqi, Zhou Xiaolin, Suo Jingdong. Estimation and variation characteristics of reference crop evapotranspiration in Northwest China [J]. Dry weather, 2016 VAT 34-42.

3. Guo Junning. A new interpretation of sandstorm in Beijing [J]. Encyclopedia knowledge, 2009 VAT 22-23.

4. Song Li-ning, Zhu Jiaojun. Sandstorms, dust storms and sandstorms [J]. Shelterbelt science and technology, 2015 Vera 5-7.

5. Zou benefits. Tracing to the Source of Sandstorm in Beijing [J]. Nature, 2008 Vera 61-63.

6. Http://124.205.185.62:8080/lssbs/18/20200515/142357552882883.html

7. Http://www.weather.com.cn/zt/tqzt/2859615.shtml#p=1

* the content of this article is provided to the author and does not represent the position of the Earth knowledge Bureau

Cover: Xiao Xie

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