In which season does dusty weather often appear? What is the dusty weather like?

Dust weather? Dust weather refers to a weather phenomenon in which strong winds roll up a lot of dust from the ground, making the air turbid and the atmospheric visibility extremely low. It is a kind of disastrous weather unique to arid desert areas such as North Africa, the Middle East, the southern United States, Russian Central Asia, northwest China and North China. ? According to the intensity of sandstorm weather, it is divided into three grades: floating dust, sand blowing and sandstorm. Floating dust means that dust and fine sand float evenly in the air, so that the horizontal visibility is less than 10 km. Because the sky is khaki, it is commonly known as falling yellow sand.

Sand blowing weather means that the wind blows up the dust on the ground, and the air is quite turbid. The horizontal visibility is between 1 km and1km. Sandstorm is the strongest and most harmful level in dusty weather. Refers to the strong wind blowing up a lot of dust on the ground, which makes the air quite turbid and the horizontal visibility is less than 1 km. When the visibility is greater than or equal to 0.5 km, it is a light sandstorm, and when it is less than 0.5 km, it is a strong sandstorm. When the visibility is less than 50 meters, it is commonly called black wind. Sandstorm directly affects the living environment of human beings and is extremely harmful.

The strong wind of sandstorm can destroy buildings and trees, cause casualties, blow down communication power facilities, cause fires, scrape off fertile soil on the surface of farmland, expose crop roots and even scrape off seedlings; It buries farmland, channels, houses, roads, grasslands and so on. In the form of wind and sand flow; In addition, sandstorms seriously pollute the environment, causing airport closures and various traffic accidents; Dust not only has a serious destructive effect on precision machinery and chemicals, but also harms people's eyes and respiratory system. There are dozens of chemical elements in dusty weather, which greatly increases the concentration of solid pollutants in the atmosphere. Strong wind makes the ground layer evaporate strongly, reducing the air humidity, and the negative oxygen ions in the air are seriously reduced, which is harmful to people's health. When a strong sandstorm occurs, the maximum wind force can reach 12, and the wind speed is more than 32.6 m/s, which is equivalent to the maximum wind force near the typhoon center that landed in China, and the resulting disaster is very serious.

The occurrence of sandstorm weather generally needs two conditions: one is strong and persistent strong wind and updraft, which provide power conditions for sandstorm weather; Second, there is abundant loose dry dust on the surface, which provides a material basis for dusty weather. The occurrence and development of dust weather can not be separated from rich dust sources. There are many Gobi deserts in northern China and Mongolia, including Gurbantunggut Desert and Taklimakan Desert, covering an area of millions of square kilometers, which provide a large number of dust sources for sandstorms. In addition, under the influence of global climate change, the phenomenon of drought and warm winter in northern China is becoming more and more serious. Unreasonable human activities, such as excessive land reclamation, grazing, deforestation and over-exploitation of water resources, have caused large-scale vegetation destruction, aggravated soil erosion, and caused soil desertification, secondary salinization and deterioration of physical properties. ? April is the prevailing period of dusty weather in China every year.

The appearance of dust weather is closely related to the situation of upper atmosphere circulation. For China, on the 5500m high-altitude circulation map, the eastern coast of Asia is a stable deep trough, and the western part of Asia is a stable ridge of high pressure. The northern part of China is under the northwest airflow behind the ridge trough. This strong northwest airflow continuously transports the cold air near Xindi Island to the southeast, which is a typical high-altitude circulation situation when dusty weather occurs in northern China.

In addition, the appearance of dust weather in China is also related to the strong development of extratropical cyclones from eastern Mongolia to eastern Inner Mongolia, the significant warming of the lower troposphere, the dryness without precipitation before the arrival of strong winds, the thickness of dust on the surface and the invasion path of cold air. According to the present situation of desertification in northern China, the control of sandstorm should start with large-scale ecological environment control, as a systematic project, unified planning, unified deployment and gradual implementation. Through scientific demonstration, according to the climate, vegetation, geography and other conditions, take corresponding measures according to local conditions to carry out comprehensive management; Intensify the adjustment of agricultural structure, develop efficient agriculture, scientifically return farmland to forests and grasslands, rotate grazing by fences, and set livestock by grass to curb the spread of desertification. North China is a region where water resources are very scarce, and water resources are the source of maintaining a good ecological environment. Therefore, it is necessary to focus on water conservation, select appropriate grass species and densities, change the current irrigation methods that are seriously wasted, and do a good job in the utilization and protection of water resources.

Due to the process of urbanization, there are many construction sites in the city and its surrounding areas. It is necessary to strengthen the dust prevention measures of these sites, do a good job in planting trees and grass in time, and reduce the impact of sandstorms on cities. It is necessary to widely carry out popular science education among the broad masses of cadres and people to prevent desertification, protect the ecological environment and love their homes. All kinds of illegal activities such as deforestation, indiscriminate mining and reclamation are strictly prohibited, and the ecological environment is protected by legal means. China has developed and used meteorological satellites to monitor sandstorms since 1993, and has initially mastered the monitoring methods of sandstorms.