When the dry wind rolls up the bare surface sand and dust and blows madly towards the city, it is a scene of yellow sand in the sky, which can be called a sandstorm in severe cases. The result is worsening air quality, obstructed transportation, and health problems such as dry and itchy throat, difficulty breathing, coughing and more.
This past week, the northern region of our country once again encountered widespread sand and dust weather.
Zhang Bihui, director of the Environmental Meteorological Office of the Central Meteorological Observatory, told China Youth Daily that the sand and dust process from March 3 to 19 was the strongest and most extensive since 23, affecting 2023 provinces (autonomous regions and municipalities) and affecting an area of more than 20.485 million square kilometers. Its intensity reached the level of a strong dust storm, the third strongest since March 2000.
Is such a sand and dust infestation just an accidental weather process? Today, when natural forest protection has been implemented and shelter forests in the three north have been established, why is the sand and dust weather still invading? On windy days, how should people protect themselves?
In the face of another round of sand and dust, many people have such questions.
Whether this round of sand and dust weather is abnormal, and where does the wind and sand come from
On March 3, this round of sand and dust weather began to appear in Xinjiang.
From the 20th to the 21st, strong winds carried sand and dust from west to east. On the 22nd, the Central Meteorological Observatory issued a gale cooling forecast and a yellow warning for sandstorms. On the 23rd, the dust turned south. On the 24th, cold air from the south brought strong convective weather to the south.
"Since March this year, there have been four sand and dust weather processes in China, which is more for March, but if it is for the entire spring, we also need to pay attention to the weather conditions in April and May in the future." Zhang Tao, chief forecaster of the Central Meteorological Observatory, said.
During the entire dust process, sandstorms occur in some areas and strong sandstorms in local areas, with minimum visibility of less than 100-200 meters.
Zhang Tao mentioned that the wind and cooling caused by this round of cold air mainly affect northwest, north China, northeast and other places, bringing 6 °C to 8 °C cooling, especially in Inner Mongolia and parts of Northeast China, the cooling range can reach 10 °C.
In the north, when some netizens posted photos of street scenes full of yellow sand, some netizens in the south also posted photos of egg-sized hail.
"The reason for the windy and dusty weather is that the current land is warming up, the sun has loosened the surface, and spring happens to be the season of cold air and wind." Zhang Tao said.
In an interview with a reporter from China Youth Daily and China Youth Network, Zhang Bihui explained that March is the high incidence of sand and dust weather, once the precipitation is low, the temperature is high, how windy the weather, and the vegetation has not yet turned green, with the surface conditions of the exposed sand source, it is easy to have a wide range of sand and dust weather.
Specific to this time, Zhang Bihui said that in mid-to-early March this year, the temperature in Mongolia and northwest China's sand source is 3-5 °C higher than the same period of the year, basically no precipitation, no snow cover on the surface, resulting in a wide range of bare surface, coupled with the strong intensity of Mongolian cyclones this year and more cold air activity, in the process of cyclone and its rear cold air eastward movement, strong winds swept up sand and dust, transported through high altitude, moved south and east, and settled in northeast China, north China, northwest China and Huanghuai and Jianghuai areas to form sandstorms, sandstorms, Floating and sinking weather.
In the words of Wei Ke, deputy director of the Monsoon System Research Center of the Institute of Atmospheric Physics of the Chinese Academy of Sciences, the sand and dust process is a normal weather phenomenon, and human beings reduce its impact more in various ways, but sand and dust are difficult to eliminate fundamentally.
"It is difficult to fundamentally change the climatic state of the arid zone of Central Asia, the windy weather is difficult to fundamentally change, and the unstable weather in early spring is difficult to fundamentally change." "The gyre of tropical easterly winds can blow sand from the Sahara Desert across the Atlantic Ocean all the way to the Amazon region of South America," Weico said. The dust in the deserts of central Asia can be blown all the way beyond Japan. ”
The vegetation coverage in the north has increased, why the sand and dust weather is still difficult to cure
Regarding the dust weather, many people on social platforms asked: Why didn't the Sanbei shelter forest we built block the sand? The forest coverage rate has increased from 5.05% to 13.57%, why is it still difficult to cure the sandy weather?
The Three North Shelter Forest Project refers to the large-scale artificial forestry ecological project built in northwest, north China and northeast China, which began in 1979 and is expected to be completed by 2050, lasting 73 years. Today, the project has been carried out for more than 40 years, and the cumulative afforestation area has exceeded 3000 million hectares.
Wei Ke told the Zhongqing Daily reporter that the role of the Sanbei shelter forest is to fix the ground and protect the soil, and excellent results have been achieved, and the Maowusu Sandy Land is even about to "disappear" from the Shaanxi territory.
However, the sand and dust mainly came from the Gobi Desert in southern Mongolia, following the high-rise north wind, reaching an altitude of more than 4000,<> meters, and was swept to northern China. At this height, the poplars and pike-trees of the shelter forest are completely unstoppable.
According to Ding Ting, a researcher at the Climate Prediction Office of the National Climate Center, in recent years, the vegetation in northern China has increased greatly, and the ecological environment has improved significantly, which is generally conducive to the gradual reduction of the number of sand and dust that invades China. However, the Gobi Desert in southern Mongolia is also an important source of sand and dust affecting China, and in the 2022 vegetation growing season, Mongolia's precipitation is less than that in the same period in the past 20 years, the vegetation cover of the sand source is poor, and the bare surface lacks vegetation protection.
In addition, she believes that this year's dust weather is mainly related to recent abnormal atmospheric circulation. Temperatures warmed up significantly in the early spring of this year, and an extremely rare warm-up occurred in early March, resulting in rapid melting of the permafrost sand in the early stage.
"March-April is the windy season in the north. Under certain windy conditions, the sand and dust caused by the source of sand and dust have been transported to China many times, which is the most direct reason for the occurrence of severe sand and dust weather this year. Ding Ting said.
Regarding the general trend of sand and dust weather changes in China in recent years, Ding Ting gave a set of data: from 2018 to 2022, the average total number of sand and dust storms in northern China was more than the average in 2013-2017, but this cannot be considered as a trend of significant increase in sandstorms.
"From a longer time scale, in the first decade of the 21st century, the total number of dust and the number of dust storms are significantly higher than in the past 10 years. This shows that at this stage, it is still in the context of affecting the reduction of sand and dust in China. Ding Ting said.
She also mentioned that the frequency of sand and dust is also directly affected by the atmospheric circulation at middle and high latitudes, so it will show certain inter-annual variations, such as the number of spring dust storms in 2017 and 2022 is only once.
"Dust weather is formed by a combination of long-term climate background, geographical background and short-term climate change." Zhang Bihui said that from the perspective of China's geographical environment, China's northern region and neighboring countries and regions have a relatively large area of sand source areas, in the congenital conditions of sand source existence, combined with climate factors, especially in the early spring of this year The temperature is obviously high, conducive to surface thawing, coupled with the effect of ground wind, will be very conducive to sand and dust winching, and under the air flow transportation, a large number of sand and dust particles to the downstream area to transmit settlement.
Zhang Bihui told reporters that in the context of climate warming, the temperature in the early spring of the northern sand source is high, which is very conducive to the sand soil becoming loose in the sand source, which increases the possibility of sand and dust weather.
How should we deal with it on a windy and sandy day?
The China Meteorological Administration predicts that in the next two months, the sand source areas from southern Mongolia to central and western Inner Mongolia will have less precipitation, the temperature will be higher than the same period of the year, and there will be a phased southward impact of Mongolian cyclones, which is conducive to the formation of sand and dust weather. It is expected that the number of sand and dust processes in northern China is more than the same period in the past 10 years, and the sand and dust intensity is generally the same as in the past 10 years.
Almost every time after the dust weather, the air and water sources will be polluted, the quality of the land will decline, and even cause damage to the ecological environment.
Zhang Bihui suggested that from April to May, the risk of sand and dust weather in northern China is greater, and it is necessary to pay close attention to the weather forecast, do a good job of protection in time, and reduce the impact of sand and dust weather on transportation, agriculture and animal husbandry, human health and urban operation.
"Increase scientific and technological research and departmental cooperation, strengthen research on the origin of sand, dust transport power and other mechanisms and research on numerical model prediction technology of sand and dust weather, and improve the level of forecasting and early warning services." Further strengthen the linkage and interaction between ecological governance of sand sources, monitoring and forecasting of sand and dust weather, early warning assessment and emergency handling of sand and dust disasters, and provide support for disaster prevention and mitigation and scientific and precise sand control. Zhang Bihui said.
The latest forecast from the China Meteorological Administration shows that from March 3 to April 31, there will be a sand and dust weather process from west to east in northwest China, north China, northeast China and other places.
Meteorological experts suggest that we should do a good job in wind reinforcement, traffic safety management and human health protection, and pay attention to preventing forest grasslands and urban and rural fires. Specific defensive measures for sand and dust weather, including closing doors and windows in time, carrying masks, scarves and other dust-proof supplies, sealing precision instruments, fastening structures that are easily blown by the wind, and properly placing outdoor items that are susceptible to sandstorms. Preventing sandstorms requires everyone to work together to reduce environmental damage.
"Our current monitoring methods can predict the weather process more accurately 5 to 7 days in advance. As soon as the sand flew over there, it was immediately visible here. However, the existing technical means can only achieve early warning, and cannot eliminate it. Weike also mentioned that current supercomputers can rehearse and calculate the path of dust.
He lamented: "Being in the lower reaches of the arid desert areas of the inland Central Asia, the conditions are like this, and we may still need to slowly learn to live with the dust weather." ”
Zhongqing Daily / Zhongqing Net reporter Zhang Mi Source: China Youth Daily