Sandstorms "make a comeback"

China Newsweek reporter: Peng Danni

Published on April 2023, 4, the 24th issue of China Newsweek magazine

When sandstorms hit Beijing this year, Liu Song, a 27-year-old Beijinger, said, "Long gone!" In his mind, large-scale dust weather has not been seen for many years. He described a feeling that "dead memories are starting to hit me."

The Central Meteorological Observatory continued to issue a blue warning for sandstorms at 4 o'clock on April 19, and it is expected that from 18:4 on April 19 to 20:20 on April 20, there will be sand or dust storms in parts of central and western Inner Mongolia, southern and eastern Xinjiang, most of Gansu, Ningxia, Shanxi, western Hebei, Beijing and other places, among which, there will be local sandstorms in southern Xinjiang, eastern Gansu, central Ningxia, northern Shaanxi and other places.

According to the monitoring data of the State Forestry and Grassland Administration, in the past 20 years, China's spring (March ~ May) sand and dust weather has generally shown a trend of decreasing frequency and weakening intensity, which has decreased from an average of 3 times a year in the 5s of last century to an average of 60 times a year in the past 21 years, and the number of sand and dust days has decreased by 10.8 days every 10 years. However, the interviewees all felt that in the past two or three years, the dust weather has "returned".

The north has ushered in the 10th sand and dust weather process this year. This year, the frequency of dust weather processes in China is the highest in the same period in the past 10 years. According to the data of the "China Meteorological Disaster Yearbook (2020)", in the past 20 years, the average number of sand and dust weather from March to April is 3.4, and the number has exceeded the average in April this year.

In 2019, the National Aeronautics and Space Administration (NASA) released a study showing that about 2000/2017 of the new green area added by the world from 1 to 4 came from China, and China's contribution ranked first in the world, part of which came from the greening of sandy areas. In this context, how to understand the "relapse" of sandstorm weather in recent years?

Or enter a new active cycle of dust storms

On April 4, there was strong wind and dust in many places in Gansu, and yellow warnings for sandstorms were issued in Jiuquan, Baiyin and other places. According to the information released by the flight travel service APP Flight Changzhun, on the same day, Lanzhou Zhongchuan Airport had a visibility of 19 meters, and by 400 noon, there were more than 12 return and diversion flights.

Dust storms are common meteorological hazards in arid and semi-arid regions. Strong winds act like "sweeping robots," swept large amounts of sand and dust from dry soil into the atmosphere, carrying them hundreds to thousands of kilometers away. The intensity of sand and dust weather is usually distinguished by horizontal visibility, and it is divided into five grades: floating dust, blowing sand, sandstorm, strong sandstorm and extra strong sandstorm from light to heavy. The horizontal visibility of floating dust or blowing sand weather is between 5 km and 1 km, the horizontal visibility of sandstorms is less than 10 km, the horizontal visibility of strong sandstorms is less than 1 meters, and the extra strong sandstorm is less than 500 meters, commonly known as "black wind".

Literature shows that the two main source areas of global sandstorms are the African desert and the Asian region with the Sahara Desert as the main body. There are three main source areas in Asia, namely Mongolia, the Taklamakan Desert and surrounding areas in northwest China, and the source area in western Inner Mongolia, with the Badain Jaran Desert as the main body.

Zhang Xiaotuo, academician of the Chinese Academy of Engineering and researcher of the Chinese Academy of Meteorological Sciences, told China Newsweek that northern China has a desert area of more than 170.30 million square kilometers, while neighboring Mongolia also has more than <>,<> square kilometers of Gobi and desert, because of the existence of these sand sources, China is one of the countries most affected by sandstorm weather in the world.

In their latest paper published in April, scholars from the Chinese Academy of Meteorological Sciences pointed out that there are five main paths for sand and dust weather transmission in China, of which the northwest path is more complex and covers the widest area. It starts from Mongolia and the sandy land outside the territory (including Ulan Bu and Desert and Kubuqi Desert in western Inner Mongolia), and transports sand and dust to the northwest, North China, Huanghuai, Jianghuai and other places as cold air travels from northwest to southeast. Moreover, the northwest path is also the most important transportation route for domestic dust weather, accounting for 4.5% of the dust weather in the past 20 years.

At a regular press conference held by the Ministry of Ecology and Environment in March, Liu Bingjiang, director of the Department of Atmospheric Environment of the Ministry of Ecology and Environment, said that since March this year, there have been more sand and dust weather in China, firstly, because the underlying surface is conducive to sand and dust activities. In 3, Mongolia's precipitation was less than that in the same period of 3 years, and the vegetation cover in the sandy source area was poor; Moreover, since March, the temperature in southern Mongolia and northwest China has been 2022~20 degrees higher than the same period of the year, which has led to rapid melting of permafrost sand, while the sand source is basically free of precipitation, and the surface is not covered with snow, resulting in a large area of bare surface.

Second, meteorological conditions are conducive to sand and dust transmission. This year, Mongolian cyclones are strong in intensity and cold air activity is more, and in the process of cold air moving eastward to the south, strong winds provide favorable meteorological conditions for the winding of dust particles into the sky.

In the past 40 years, the frequency of sand and dust weather in northern China has shown a slow downward trend. However, according to the National Climate Center's Climate Prediction Office, the average total number of dust weather and the number of dust storms in the north between 2018 and 2022 are higher than the average from 2013 to 2017.

In March 2021, many places in the north were hit by sandstorms, and on March 3 of that year, the Central Meteorological Observatory characterized it as "this process reached the intensity of strong sandstorms, which is the strongest sand and dust weather process in China in the past 3 years". According to the Ministry of Ecology and Environment, during the sandstorm, the concentration of PM16 in Beijing rose rapidly in a short period of time, rising fourfold in one hour, reaching 10 micrograms per cubic meter; The PM10 concentration in the sixth district of the city reached 1 micrograms per cubic meter.

"In the past few years, everyone felt that sandstorms were becoming fewer and fewer, thinking that sandstorms had disappeared, but from the perspective of the past two or three years, sandstorm weather has slowly increased in the past two years, and it is in a shock trend." A domestic atmospheric science scholar said in an interview with China Newsweek.

In recent years, does the frequent sandstorm weather mean that we have entered a period of active sandstorms? In this regard, the experts interviewed said that it was not possible to give an accurate judgment. "There is a cyclical change in the climate system, but this cyclical change is not actually very clear now, and it is difficult to judge the trend based on the short-term situation of several years." Wu Chenglai, an associate researcher at the Institute of Atmospheric Physics of the Chinese Academy of Sciences, told China Newsweek.

Zhang Xiaotuo believes that from the perspective of monsoon activity, we may have entered a new period of active sand. He further analyzed that the winter wind has a large cycle of 50~70 years. In the 1970 years of the 10s, sandstorms in China were more serious, and the occurrence of sandstorms was in a downward trend. In the large cycle, the winter wind has a short and medium cycle of 20~30 years, in this process, in 2002 Beijing had a very large range of sandstorms, since then the wind has been in the process of weakening. If you look at the 50-year cycle, the 2020s is the beginning of a new cycle.

Wu Chenglai also observed this change. Since 2018, the increase in surface wind speed may largely be a cyclical change, but this needs further study. He said that because the entire sand and dust source area is very large, specific to different areas, it depends on the local surface conditions, geographical environment, etc., and the difference between different areas can sometimes be very large.

Why did Mongolia become the hardest hit area for sandstorms?

In mid-March 2021, when China was hit by the "strongest sandstorm of the decade", severe weather such as snowstorms and extra-large sandstorms occurred in Mongolia in many provinces, with winds reaching 3 meters per second. On April 20 this year, the National Meteorological and Environmental Monitoring Bureau of Mongolia issued another warning of strong sandstorms, and the strong sandstorms that are forming in the western and northwestern regions of the country will sweep the entire territory of Mongolia from the 4th.

Mongolia is an important "source" of sandstorms in China. For example, during the strong sandstorm on March 3~19 this year, according to satellite observations, on the morning of the 24st, a clear distribution of sand and dust could be observed in southern Mongolia, and since then the range of sand and dust has continued to expand.

Wu Cheng said that it is actually not very clear how much to contribute to a certain place. Because the upstream situation of the sandstorm is obtained through satellite observation, some overall characteristics can be grasped, such as the content of sand and dust in the atmosphere, but because the movement process of the sandstorm will be accompanied by sand and settlement, so how much sand and dust on a certain ground is rolled up such information, more first-hand data is required.

In the past decade, the number of sandstorms in the Gobi region of Mongolia has increased fourfold compared with the 20s of the 60th century. In 4, Enkhbat, director of the Department of Climate Change of the Ministry of Natural Environment and Tourism of Mongolia, said in an exclusive interview with Xinhua News Agency that Mongolia is one of the countries most affected by global climate change, and the incidence of sandstorms is on the rise.

Most of Mongolia is covered by grasslands, with mountains in the north and west, and the Gobi Desert in the south. In the southern part of the country, many provinces have the word "Gobi" in their names. Overall, Zhang pointed out that Mongolia's main source of sand, more than 39,<> square kilometers in the south, is not mainly due to the destruction of the surface by human activities in recent years, which has made the sand and dust active, in fact, it is sparsely populated, and the desert and Gobi are there.

Mongolia is located in the middle and high latitudes of the Inner Asian steppe, the whole territory is deep inland and far from the sea, belongs to the temperate continental climate zone. To add insult to injury, the natural geographical location and global climate change have made the natural conditions in this region even harsher.

In November 2020, a paper published in the journal Science, "East Asia's inland climate crosses the critical point to become suddenly hot and dry", mentioned that in the past 11 years, the inland region of East Asia, centered on Mongolia, has experienced an unprecedented "heatwave-drought" concurrent phenomenon, which clearly exceeds the scope of natural variability and forms a vicious circle: soil drying accelerates local high temperatures, which in turn exacerbates the decline of soil moisture.

In the past 80 years, the average temperature in Mongolia has risen by about 2.25 degrees Celsius, much higher than the global average temperature rise rate, and during the same period, Mongolia's annual precipitation has decreased by 7%~8%, especially in warm seasons such as spring and summer. Up to now, 76.8% of Mongolia's total land area has suffered from varying degrees of desertification, and the situation is still deteriorating. According to official data, the past 10 years have been the hottest in the country in nearly 80 years, with drought and heat causing 10,1244 large and small rivers and lakes to dry up or stop flowing.

However, on April 4, at the sixth assessment report presentation of the United Nations Intergovernmental Panel on Climate Change (IPCC), IPCC expert Zhai Panmao said that the current research on tipping points and irreversible phenomena is far from enough, and to reach conclusions, different researchers and different methods are needed to provide multiple evidence from observations, mechanisms, models and other aspects.

Zhai Panmao said that although Mongolia's dry heat conditions exist for a long time and intensify, which will affect land vegetation cover, under the background of climate warming, there is still a trend of increasing vegetation and precipitation in many mid- and high-latitude areas.

In 1998, in order to provide scientific support for the development, ecological restoration and environmental governance of natural resources in the international arid zone, the Xinjiang Institute of Ecology and Geography of the Chinese Academy of Sciences was established. Li Shengyu is a senior engineer of the institute, in 2018~2020, he led the implementation of an international scientific and technological cooperation project, called "China-Mongolia grassland desertification control technical cooperation research and demonstration", and in 2019 went to Mongolia for research and experimental research.

He told China Newsweek that northern Mongolia's South Gobi is a grassland belt that is more affected by global climate change and local economic development activities. His field research found that the degradation of grasslands in these areas is very obvious, and the center of gravity of desertification tends to move northward, increasing the source of sand and dust in Mongolia, which is a new problem.

Mongolia is the world's second largest landlocked country after Kazakhstan, but with a population of only 330.90 million, it is the world's least densely populated sovereign state. Livestock production accounts for about 4% of the country's agricultural production, and 1 in <> Mongolians is engaged in animal husbandry, which is higher than any other industry in Mongolia.

　　2019年底，国际货币基金组织发文指出，蒙古国的畜牧业曾是国民经济的主要引擎，现在面临着气候变化和过度放牧的威胁。自1990年以来，牲畜数量增加了三倍，达到7000万头，大大超过了土地的承载能力。该机构研究还指出，蒙古的过度放牧与全球羊绒价格飙升有关，同时也与缺乏适宜的土地使用法规或草场管理标准有关。

Nomadic herding was originally a human activity with a relatively small burden on grassland, but Li Shengyu said that driven by the demand for the international cashmere trade, the local area is now not only overgrazing, but also prefers to breed goats, goats will eat grass close to the ground, and even cut out the grass roots to eat, which is more damaging to the grassland. On the other hand, unlike domestic pasture regulations, pastures in Mongolia are communal, which leads to a "tragedy of commons", where people want to use pasture to the maximum extent possible, but do not care about its sustainable use.

Mining is another issue. Mongolia is rich in mineral and coal resources and is known as the "Saudi Arabia of coal mining". Thanks to mining production and investment from foreign mining companies, Mongolia achieved unprecedented economic growth and entered the ranks of middle-income countries in 2012. By 2019, the total output value of mining accounted for 23.8% of Mongolia's GDP, and mineral exports accounted for more than 70% of the total, and there was a trend of increasing year by year.

Li Shengyu said that many coal mines are located in the Gobi in southern Mongolia, and they are all open-pit mines. Open-pit mining requires peeling off the surface soil layer, the mining area is very large, and there are not many environmental protection measures, once it encounters dry, windy weather, the excavated dust is flying with the wind. Moreover, mining has changed conditions such as groundwater or rivers, exacerbating the deterioration of the growing environment of grasslands.

Since 2007, the Chinese Academy of Sciences has carried out cooperative research with Mongolia on desertification prevention and control, and has given experience in desertification control through local investigations. Since 2013, the former State Forestry Administration has organized the Institute of Desertification of the Academy of Forestry Sciences and other scientific research institutes to hold desertification prevention and control seminars for Mongolia to promote mutual learning and mutual learning from the experience of China and Mongolia in desertification control.

"Affected by many factors, Mongolian sandstorms have entered a new active period, which requires a lot of research in the future. Mongolia's relative lack of field research stations, monitoring equipment and instruments is very detrimental to the development of research work. Huang Ning, professor of the School of Civil Engineering and Mechanics of Lanzhou University and director of the Key Laboratory of Disaster and Environmental Mechanics of the Ministry of Education in Western China, once said. Zhang Xiaotuo, who once went to Mongolia as a United Nations expert to investigate, said that the China Meteorological Administration and Mongolia have long cooperated to help each other build an observatory, but there is no way to invest in people, money and materials, and the observatory remains in a very loose state.

Fighting sandstorms: what can humans do?

Han Bin, a 32-year-old Beijinger, also noticed that in earlier years, Beijing was rarely affected by sandstorms in the spring. He attributed the good weather to China's desertification control achievements. When cities such as Beijing have been hit by sandstorms again in the past two or three years, some people have asked: Why has all these years of afforestation failed to stop the sandstorms?

In 1978, the Sanbei shelterforest project named "Great Green Wall" began to be implemented, which became a landmark project for wind and sand control in China. The Sanbei region is home to China's eight deserts, four sandy lands and vast Gobi, with a total area of 149.85 million square kilometers, accounting for about <>% of the country's aeolian and sandy land area.

Since then, China has successively launched key ecological projects such as returning farmland to forest and grassland, protecting natural forests, and controlling wind and sand sources in Beijing and Tianjin. At the legal level, the Law of the People's Republic of China on Desertification Prevention and Control has been promulgated, and policies such as subsidies for desertification land closure reserves, compensation for ecological public welfare forests, and subsidies and incentives for grassland ecological protection have been formulated.

"Among the many countries affected by sandstorms in the world, the Chinese government is one of the countries that has really put effort into desertification prevention and control." Li Shengyu said that China has invested a lot of money, established many professional management institutions, and a large number of scientists are engaged in related scientific research. Zhang Xiaotuo also pointed out that compared with its neighbors, China's efforts and efforts are the most, which is to be affirmed.

In terms of desertification control, China can be called a global benchmark. However, many experts interviewed pointed out that more careful analysis is needed to determine the extent to which desertification control has slowed sand and dust storm pollution.

In the Taklamakan Desert, the largest desert in China, a study published in 2022 by Huo Wen, a researcher at the Urumqi Institute of Desert Meteorology of the China Meteorological Administration, found that in the central area of the desert, artificial green space can reduce the wind speed near the ground by about 70%. Huo Wen told China Newsweek that the shelter forest project is conducive to preventing desertification, improving the soil environment, reducing the wind speed near the ground, and is a good manual intervention means to overcome the severe weather of wind and sand; In addition, the vegetation root system makes it easier for the soil to retain moisture, reduce evaporation, and produce a "water lock" function, making it difficult for the ground to become sandy.

But when the cold air from Mongolia swept south into China, Hovin said it affected thousands of meters in the air, and its height was no longer enough for the Sanbei shelterforest. A shelter forest twenty or thirty meters high can block part of the coarse sand on the surface, but it is far from blocking the dust particles carried high up by the wind. However, the shelter forest system can reduce the "sand and dust relay" on the sand and dust transmission path, which is still of great ecological significance.

Wu Chenglai's research work, in addition to monitoring sandstorm weather, also includes reviewing and analyzing the evolution of sandstorms to understand some major sandstorm occurrence mechanisms and main drivers. After 2000, his team analyzed the reasons for the decline of sand and dust activity in East Asia between 2001~2017.

In this article, published in Nature Communications in 2022, research shows that weakening surface wind speeds contributed 46% of the decline in sand and dust activity during this period, playing a leading role; Soil wetting and greening contribute the remaining 54%. Among them, the contribution rate of vegetation greening is about 30%, including human tree planting and grass planting projects, as well as naturally growing vegetation. In this sense, the role that human sand control projects can play is much smaller than the impact of changes in meteorological factors.

There is a view that finer sand and dust from a large number of dry lakes and desertified land is a more important source of sand and dust, but it has not received due attention and active treatment. However, Zhang Xiaotuo said that these finer dust fluxes are relatively large, but compared with the traditional sand and dust source areas of the desert, their proportion is very small. Flux refers to the sand that can be released into the atmosphere per unit time and area.

Different from the public's optimism, many scholars engaged in desertification control and sandstorm research have emphasized that people are small in the face of sandstorm problems and the impossibility of eradicating sandstorms.

Compared to other air pollution, dust storm weather is a phenomenon in which nature dominates, it has been around for millions of years, and it can hardly even be called a "disaster" if it were not for human likes and dislikes. As some scholars have pointed out, about 2800 million tons of sand and dust from the Sahara Desert in Africa cross the ocean to South America every year, bringing about 2,2 tons of phosphate fertilizer to the Amazon rainforest, thereby nourishing and compensating for the lost nutrients of the tropical rainforest; millions of years of dust fall is the source of the deep loess layer in the north, and also "nourishes" the fishing grounds of the Sea of Japan and the North Pacific region.

Compared with the vast desert and Gobi area, China's efforts for decades have only "greened" a very small part. The official circular of the State Forestry and Grassland Administration in March this year mentioned that in recent years, China's desertification and desertification land area has continued to shrink, and good results have been achieved in desertification prevention and control. However, China still has 3,257,37 square kilometers of desertified land and 168,78,<> square kilometers of desertified land, especially large areas of desert and Gobi, which have always been huge and permanent sources of sand and dust.

"In general, we have done some governance work on the edge of the desert, near the river, but this accounts for 170%~6% of the more than 7.<> million square kilometers of desert. Fundamentally, most deserts are in extremely arid areas, with average annual rainfall of tens of millimeters or less, and the human impact is very weak. Zhang Xiaotuo stressed to China Newsweek.

On the other hand, some unscientific and irrational behaviors in the process of desertification control have played a counterproductive role in the ecological environment. Xue Xian, researcher at the Northwest Institute of Eco-Environment and Resources of the Chinese Academy of Sciences and director of the Desert and Desertification Research Office, said in an interview with the media that in recent years, due to the single vegetation and high density of shelter forests, shelter forests have degraded and died.

A scholar engaged in desertification control at the grassroots level said in an interview with China Newsweek that in reality, there are still many problems in desertification control, "We may still overemphasize the new area of desertification prevention and control and afforestation, and even turn it into an administrative indicator."

Zhang Xiaotuo said that today, in the scientific community, the study of sandstorms has shifted from its scientific understanding to how to prevent and control sandstorms, especially forecasting and early warning. In his view, in the future, humans can change relatively limited, and more accurate forecasts and warnings can slow the harm of sandstorms to society and individuals.

"Dust storms are large-scale land surface processes that involve climate change and regional anthropogenic activities." The grassroots researchers who have been engaged in desertification control for many years hope that the public will not completely deny China's achievements in desertification prevention and control over the years because of the revisit of sandstorms. Perhaps, when the next sandstorm comes, we will still think: how can we better prevent and control sand? What ordinary people can do may just be close doors and windows, reduce going out, and wear masks.

(Intern Li Jinjin also contributed to this article, in which Liu Song and Han Bing are pseudonyms.) )

China Newsweek, Issue 2023, 15

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