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The strongest sand and dust go south, experts tell you what is the relationship between the sandstorm and floating dust
◎ Our reporter Liu Zhiwei
On March 15, the strongest sandstorm in the last 10 years affected northern China, and 12 provinces, autonomous regions and municipalities were covered with sand; On the 16th, affected by cold air, north-central Anhui, north-central Jiangsu and north Hubei, etc. Some parts of the country are still littered with sand and dust, and severely polluted weather has emerged in many places.
Sandstorms in the north, floating dust in the south. What exactly is happening?
On March 17, the journalist interviewed Hubei meteorological expert Huang Zhimin. He said that in places like Danjiangkou City in northwest Hubei, affected by sand and dust weather, the gloomy sky after 1:00 p.m. on the 16th became darker and horizontal visibility was lower. only three to four kilometers., It is called “floating dust” in meteorology.
“In spring, even in the area south of my country’s Qinling Mountains, floating dust will make the clear sky, the sun and the moon hazy, and the landscape thousands of meters away is often swallowed up invisible. “. Huang Zhimin said that sometimes there is no strong wind and there is no dust in the area. He is obviously an uninvited guest from the dry north. Generally, it is the cold air of Siberia and the Mongolian plateau, the north wind that blows before and after it invades our country, and the dry sand and dust particles rise into the sky. If strong winds are maintained, the dust will continue to be lifted and transported to the local area through the high-altitude northwestern airflow. If the local climate is good and the soil heats up quickly, the sand and dust are difficult to settle due to the weak updraft and buoyancy of the air, which makes the floating dust last for two to three days.
As for the appearance of floating dust, sandstorms usually occur first in the north like this time. Strong winds blew a large amount of dust from the ground into the air, making the air particularly cloudy, resulting in horizontal visibility below 1,000 meters. The dust storm that involves a large amount of dust and other fine-grained substances at high altitude and continues to advance with the high current of air moving thousands of kilometers away. This is the cause of the floating dust that occurs in the southern Qinling Mountains.
Huang Zhimin said that the occurrence of sandstorms must meet three conditions: sources of sand and dust, strong winds and unstable stratification of the atmosphere. The sandstorms in my country are part of the Central Asia Sandstorm Zone, one of the four most sandstorm-prone zones in the world. First of all, there must be deserts and desertified lands as a source of sand and dust. General sandstorm generation requires 6-7 winds, with an instantaneous wind of 8 — Level 9 or higher. Only when the intensity of the cold air is stronger than the intensity of the cold air that forms a general gale, can sandstorms form. In addition to the spring warming, the desert and dust on the surface heat up easily, and continuous sunny days will raise the soil temperature very high. If the cold air passes through the border around noon, the dust will be rolled up to thousands of meters due to the violent upward movement of the air, over the sky, and carried horizontally with the air current thousands of kilometers or even further. , it turns into floating dust in different places.
It is estimated that the floating dust that entered some parts of the south this time will be short-lived due to rainfall. However, under the general trend of global warming, due to increased temperatures, increased evaporation of surface water and reduced vegetation, the wind near the ground will increase, it is not ruled out that storms will occur in the future sand frequently. Therefore, planting trees and vegetation in the desert area or on sandy ground can reduce the dangers of sandstorms.
The Chinese government attaches great importance to countermeasures to prevent desertification and control desertification and has achieved remarkable results. In recent years, the dusty climate has dropped significantly. This will undoubtedly help not only improve the country’s regional air quality, but also benefit countries and regions downwind.
Of course, everything has a “double nature”: although sandstorms or floating dust are to be avoided as disasters, they also bring soil with humus and beneficial trace elements, which spread to farmland and “fertilize” the soil.
At the same time, dust is also a good condensation core in the air, in a sense, it is a natural catalyst to increase precipitation. The key is that people should plant more trees in their habitat to remove dust and purify the air near the ground to benefit and avoid damage.
