Experts analyze two reasons for this year's strong dust weather

OA show ('918 '); Beijing, May 15, this report: the Ministry of Geosciences of the Chinese Academy of Sciences held today in Beijing the academic report meeting on "the causes of sand dust weather in North China and the Countermeasures for its control" After investigation and analysis, academician ye Duzheng and other experts proposed that this year's strong sand dust weather is caused by the anti El Nino event Experts analyze that there are two reasons for the dust weather: first, the increase or decrease of the number of strong wind days in northern China is a reflection of the cyclical climate change, and this year's sharp increase of the dust weather is due to the peak of anti El Nino events Experts explained that the anti El Nino event refers to the abnormal cooling of the sea surface in the equatorial Middle East Pacific Ocean, that is, "La Nina phenomenon" It will disrupt normal atmospheric circulation and further affect other areas 2、 The local improvement and overall deterioration of the surface cover in the north of China is another important reason for this year's strong dust weather In the spring of this year, dust weather has occurred in the north of China, especially in the north of China It is rare in the same period of history because of its early time, high frequency, wide range and high intensity It has brought adverse effects on the transportation, environmental management and people's daily work and life in the north of China, causing direct danger to Beijing, Tianjin and other major cities, especially Beijing and its surrounding areas Harm, caused widespread concern in society For this reason, the Department of Geosciences of the Chinese Academy of Sciences decided to set up a "Consultation Group on Sandstorm of the Department of Geosciences of the Chinese Academy of Sciences" headed by a famous meteorologist, academician ye Duzheng, and composed of more than ten people, including researcher Ju Hongbo, director of the resource information Institute of the Chinese Academy of forestry, researcher Liu Jiyuan, director of the geographical science and Resource Institute of the Chinese Academy of Sciences, and researcher Zhou Zijiang, director of the climate information center of the National Meteorological Center That is to start the research Since April 10, the Advisory Group has analyzed a large number of data and materials, held seven seminars on this basis, formed a report and submitted it to the State Council The report analyzes the causes of strong dust weather and its future trend Three suggestions are put forward to reduce and prevent sand and dust disasters First, we should do a good job in returning forest and grass to restore natural vegetation in a large scale in the near future In particular, we should highlight the key points, establish an effective ecological barrier to reduce and prevent sand and dust disasters in Beijing and Tianjin, and at the same time, control the surrounding areas of the city, and inhibit the local sand rising; secondly, we should attach importance to the construction of ecological environment in the implementation of the western development strategy, and consider the ecological, economic and social benefits together; thirdly, we should establish and improve the monitoring and early warning system of sand and dust weather, and do a good job Scientific research on disaster prevention and mitigation Background news why the sandstorm weather is so rampant this spring The sandstorm weather in North China, especially in North China, has brought adverse effects on the transportation, environmental management, people's daily life and work in North China, and even caused casualties in some places Why is the strong sandstorm this spring so rampant? The "Advisory Group on Sandstorm of the Ministry of Geosciences, Chinese Academy of Sciences" is composed of academician ye Duzheng, a famous meteorologist, and researchers Ju Hongbo, Liu Jiyuan and Zhou Zijiang After detailed investigation and research, the report "causes of Sandstorm in North China and Countermeasures" is put forward and reported to the State Council According to academician ye Duzheng, in meteorology, the dust weather is divided into three levels: floating dust, blowing sand and sandstorm Floating dust refers to the dust and fine sand floating evenly in the air without wind or with small wind force, so that the horizontal visibility is less than 10km; the floating dust and fine sand are mostly the dust far away from the ground spread by the upper air flow, or the dust that has not sunk after the appearance of dust storm and blowing sand Sand blowing refers to that the air is quite turbid and the horizontal visibility is 1-10km due to the strong wind Sandstorm refers to the strong wind that brings a large amount of dust on the ground into the air, making the air especially turbid and the horizontal visibility less than 1 km The strong sandstorm (the instantaneous wind speed is more than 25m / s, and the wind force is more than grade 10) can make the horizontal visibility of the ground lower than 50m, with great destructive power, commonly known as "black wind" Experts pointed out that there are generally two conditions for the occurrence of sandstorm and sand blowing weather: one is strong and lasting wind, and strong cold air is the driving force for the formation of dust weather Second, the surface is rich in loose and dry dust The dust weather in North China mainly originates from the Midwest of Inner Mongolia and the northwest of Hebei Province According to the observation of experts, the dust weather that affects North China this spring mainly originates from the Midwest of Inner Mongolia and the northwest of Hebei Province The dust material on the surface of the birthplace and along the way is the main part of the dust The bare soil on the surface and the building sand stone in the urban expansion area provide the material source of local sand lifting In 2000 (up to April 25), 8 dust storms have occurred in North China According to satellite remote sensing detection, the eight dust weather events affected Inner Mongolia, Ningxia, Gansu, Shaanxi, Shanxi, Hebei, Beijing, Tianjin, Liaoning, Jilin, Shandong, Henan, Hubei, Jiangsu, Anhui and other provinces, cities, autonomous regions, with a total area of about 2 million square kilometers Among them, the dust which has a significant impact on Beijing area mainly originates from the central and Western Inner Mongolia and the Northwest Hebei With the cold air moving to the southeast, the sand is rising along the way, which is increasing The proportion of soil and sandy soil is high, accounting for 93.52% There are many fine-grained materials, which are easy to become the source of dust This area is located in the grassland area of our country, and the land use is mainly grazing grassland and dry farming land Due to land degradation, the vegetation of these pastures is sparse and the desertification is serious; in the dry cultivated land, the water source is short and the topsoil is bare The observation shows that there are abundant dust substances in the surface material composition of the areas affected by the previous dust weather in North China this year In addition, the surface soil is dry and loose, which provides the material basis for the dust weather This fact is totally different from the common concept that the dust material mainly comes from the natural Gobi and desert The sharp increase of dust weather is caused by the peak period of anti El Nino events Experts analyze the causes of dust weather and think that the sharp increase of strong dust weather this year is caused by the peak period of anti El Nino events The anti El Nino event refers to the abnormal cooling of the sea surface in the equatorial Middle East Pacific, which will disturb the normal circulation and further affect other regions In the 1970s, the anti El Nino event was dominant, and the strong dust weather caused by the cold wave and gale in the north of China was very frequent; in the 1980s-1990s, the El Nino event was dominant, and the strong dust weather was less The year 2000 is the peak period of anti El Nino event after the strongest El Nino event in the 20th century The change speed and intensity of this large-scale ocean atmosphere process are faster than before, which results in the frequent occurrence of strong cold wave and gale in the north of China last winter and this spring In addition, the temperature in North China and the eastern part of Northwest China is significantly higher in spring, which is rare in the past 40 years At the same time, the precipitation is rare, and the vegetation has not yet formed Moreover, before the arrival of each gale, there is no obvious precipitation process that can inhibit the sand lifting, resulting in a large area of surface soil dry and loose after thawing, resulting in many times of strong sand and dust weather Experts also pointed out that the local improvement and overall deterioration of the surface cover in northern China is another important reason for this year's strong dust weather Under the influence of global climate change, the phenomenon of drought and warm winter in the north of China is becoming more and more serious, together with the interference of unreasonable human activities, resulting in the destruction of a large area of vegetation, aggravating desertification, soil erosion, soil secondary salinization and the deterioration of soil physical properties The main reason for the frequent occurrence of severe sandstorm is that desertification is spreading and expanding rapidly Experts said that for many years, China has managed and damaged the desertified land, and the overall damage is greater than the governance The study shows that the area of desertified land in China expanded by 1560 square kilometers every year in the 1950s and 1960s, and by 2460 square kilometers every year in the 1990s Under the condition of coexistence of improvement and destruction, the basic situation of land cover change in China is that after the construction and destruction are offset, the land desertification area is still growing rapidly, with partial improvement and overall deterioration This situation provides a material source for the frequent occurrence of dust weather this year Over the past 10 years, the number of degraded grasslands in China has increased from 86.67 million hectares to 130 million hectares, an increase of 43.33 million hectares, with a degradation rate of 4.333 million hectares per year The results of grassland degradation are desertification and salinization The deterioration of the surface cover alone can not constitute a strong dust weather In the climate background of the 80-90's El Nino events dominating and the low frequency of cold wave in northern China, the aggravation of dust weather caused by the deterioration of surface cover is not obvious However, once the frequent cold wave and gale weather such as this spring, coupled with the deterioration of the surface cover, the two causes are superimposed, resulting in the continuous occurrence of strong sand and dust weather, endangering social production and people's lives The analysis of the observational data of the future climate change trend in China shows that in recent decades, the climate in the northern part of China has an obvious aridity trend, and the surface moisture index and soil moisture have decreased significantly, which provides a climate background for the occurrence of sandstorm The analysis results of several global climate models and regional models indicate that in the future decades, under the influence of global warming, the precipitation in the mid latitude inland area of the northern hemisphere will not change much, but the temperature will increase significantly, the evaporation of the surface will increase, and the soil will dry This is a bad climate background conducive to the occurrence of sandstorm In addition, it is difficult to fundamentally reverse the unreasonable use of land resources in a short period of time, the degradation and reduction of grassland resources are difficult to fundamentally change, and the contradiction of water resources shortage is becoming increasingly serious, which should cause our attention Under the condition of global warming and no fundamental improvement of surface vegetation in northern China, it is still possible to have even more severe dust weather like this year if there is another strong winter wind year caused by anti El Nino events in the future Reporter Xue Dong correspondent Longtan China feed industry information network 5BC (author:)