Dust weather and sandstorm
Dust weather and sandstorms are two concepts that are both connected and different. Dust weather refers to a weather phenomenon in which the wind scatters dust and sand into the air and makes the air turbid. According to visibility and wind speed, it can be divided into five levels: floating dust, sand, sandstorm, strong sandstorm, and strong sandstorm. Sandstorms are one of the ranks. The meaning of dust storms in daily life often refers to sand and dust weather, and it is not strict to say that any level of sand and dust weather is a sandstorm.
Meteorologists said that China has entered a period of frequent dust and sand weather. Dust weather in most parts of China occurs mainly in spring, from March to May. More than 50%, or even 80% to 90% of the dusty weather in most parts of northern China occurs in the spring. From the seasons, the dusty weather in spring is the most, accounting for more than half of the total year, followed by summer, and autumn (the winter is the lowest in Xinjiang). According to the month, the highest frequency of sandstorms occurred in April. And in May, the lowest in September (Xinjiang is December or January).
Monitoring and forecasting sand and dust weather is one of the key points of the meteorological department's spring work. The meteorological department has adopted various means to monitor and forecast it, and conduct monitoring and forecasting through satellites, sandstorm stations, conventional forecasts and numerical forecasts. For the moment, the most important measure is to establish a sound monitoring network system and a dust storm forecasting system to prepare disaster prevention work in advance.
Floating dust refers to the weather phenomenon in which the dust sand floats in the air when the weather conditions are no wind or the average wind speed is less than or equal to 3.0 m/s, so that the horizontal visibility is less than 10 km.
Yangsha refers to the weather phenomenon in which the wind blows the ground dust to make the air quite turbid and the horizontal visibility is less than 1 to 10 kilometers.
Dust storms are weather phenomena in which strong winds blow the ground dust to make the air turbid and have a horizontal visibility of less than 1 km.
Strong sandstorms are weather phenomena in which strong winds blow up the ground dust, making the air very turbid, and having a horizontal visibility of less than 500 meters.
Extra strong dust storms refer to weather phenomena in which the wind blows the ground dust to make the air particularly turbid and the horizontal visibility is less than 50 meters.
The frequency and intensity of dust weather in recent years is below average
In recent years, dusty weather has received more and more attention. Relevant statistics show that in China, sand and dust weather has occurred more frequently and intensively than in the past few decades. From the long-term trend, from the 1960s to the 1970s, the average number of sandstorms per spring was relatively high; after the mid-1980s, the trend of sandstorms was relatively obvious. It has been below the average line since 1985 and reached the lowest in 1997. Point, there has been a relatively large increase since 1997, but it has not exceeded the multi-year average. After 2000, the dust storms were most frequent in 2001 and 2006, but their overall intensity was below the multi-year average.
The formation of sandstorms requires four elements: one is the dusty material on the ground, which is the material basis for the formation of sandstorms; the other is the strong wind, which is the driving force for the formation of sandstorms; the third is the unstable air state, which is an important local area. Thermal conditions; Fourth, arid climate. The intensity of sand and dust weather depends mainly on weather and climate factors. In China, if there is a severe drought in Mongolia and northern China, and the cold air in the spring is strong, the dusty weather will be stronger. Conversely, if the precipitation in the north is sufficient, the cold air activity will be weak, and the dusty weather will be weaker. It must be emphasized that sandstorms are a natural phenomenon, and even when there are no humans millions of years ago, there are dust storms on the earth. The impact of desertification caused by human activities on sandstorms is very limited. Of course, under the same weather and climate conditions, desertification has a certain effect on the intensity of sandstorms and the increase in duration.
Dust storms in China are part of the Asian sandstorms, and their main source areas are arid and semi-arid regions in mid-latitude Asia. Due to insufficient annual precipitation and sparse vegetation in these areas, it is very easy for sand to pass through the wind.
From the point of view of the circulation situation, the dust storms in spring in northern China are mostly caused by the adjustment of the circulation in the Eurasian region, the increase of the circulation and the longitude of the circulation, and the influence of the cold air of the West Siberia to the south. When the East Asian trough is obviously deep, the meridional warp direction of the middle and high latitudes of Asia and Europe is significantly increased, and when the cold air invading China is obviously strong, there will be many occurrences of dust storms, large range and strong intensity in China.
China takes the lead in carrying out numerical prediction of dust storms
China is the first country in the world to carry out the numerical forecasting business of sandstorms. The numerical assimilation technology of sandstorms in China is at the international advanced level, and the satellite dust detection technology is also very advanced and comprehensive. Fengyun No. 2 C star, D star and Fengyun No. 3 A star are all conducting observations in this regard.
The Center for Atmospheric Composition Observation and Service of the China Meteorological Administration has worked closely with the National Meteorological Center, the National Satellite Meteorological Center and the National Meteorological Information Center to establish the CUACE-Dust numerical forecasting system for dust storms in Asia, making China the first effective development in the world. Countries with numerical predictions of sandstorms. The forecasting system is equipped with a complete three-dimensional data assimilation system, which can assimilate satellite data, ground conventional observation data and sandstorm station network observation data into the forecasting mode. In the spring of 2006, the system was run twice a day for a 72-hour rolling forecast, providing real-time forecasting products and forecasting services. The TS score for the average 24-hour sandstorm forecast in spring reached 0.31, which has officially become the dust storm forecasting service of the China Meteorological Administration. mode.
In addition to the National Meteorological Center and the Atmospheric Composition Observation and Service Center, the CUACE-Dust forecasting system has been extended to three regional meteorological centers in Urumqi, Lanzhou and Shenyang, and two provincial meteorological bureaus in Inner Mongolia and Hebei, starting in the spring of 2007. The system plays a role in the prediction of dust storms.
In-depth international cooperation
China is a country heavily affected by sand and dust storms in the world, and international cooperation in this regard is indispensable. Our country has participated in many international cooperation. For example, the World Meteorological Organization's International Sandstorm Program (WMMDS), which was initiated by China, is one of the program sponsors of the Institute of Chinese Academy of Meteorological Sciences, Zhang Xiaoshao. The International Sandstorm Program focuses on establishing a global sandstorm warning system. The system has two nodes, one of which is the Asia Pacific Regional Forecast and Warning Center of the China Meteorological Administration. The Center for Atmospheric Composition Observation and Service of the China Meteorological Administration is responsible for coordinating and coordinating the forecasting and service of sandstorms in the Asia-Pacific region. This work will further enhance and consolidate China's international leading position in the field of sandstorm numerical prediction and research, and effectively promote the in-depth development of China's sandstorm numerical forecasting field.
In the area of â€‹â€‹sandstorm monitoring, some meteorological stations in China have realized data sharing as an exchange meteorological station of the World Meteorological Organization.
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