What is the relationship between flood or dust storm formation and vegetation

Under the condition of good vegetation growth, the underlying surface can trap more rainwater runoff (replenishing the ground through infiltration on sunny days), and the flood peak arrival time is later and the peak flow is smaller (compared with the latter case). If the vegetation growth is poor (such as Gobi and desert), the ability of the underlying surface to store rainwater runoff decreases, the runoff retention time is shortened, the peak flow increases, and the flood peak arrival time is advanced, which will increase the risk of flooding to a certain extent. Under the conditions of urbanization, the vegetation is destroyed in large quantities and replaced by impervious underlying surfaces, and the in-line drainage method is adopted, which greatly increases the risk of flooding by advancing the arrival time of flood peaks and increasing peak flows!

Of course, the occurrence of floods is also affected by the rain, and during heavy rainstorms, a large amount of rainwater has no proper way out (insufficient storage space or drainage capacity), which will inevitably lead to flooding.

For the second problem, when the vegetation (trees and turf) grows well, on the one hand, it can reduce the speed of the wind at the surface, thereby reducing the uplift of sand and dust; On the other hand, plant roots can fix the soil, and the soil at the root system is generally wetter, so it also reduces the probability of the soil being lifted by the wind to a certain extent. Therefore, the better the vegetation growth and the greater the density, the more unfavorable it is for the formation of sandstorms, and the worse the vegetation growth and the smaller the density, the more serious the sandstorms!

Floods or dust storms are formed because vegetation is destroyed.

Influence of watershed vegetation on flooding: suppressing flood hazards.

Vegetation and its soils absorb water to reduce the amount of flooding;

Vegetation cover reduces soil erosion and downstream siltation caused by flooding; (Vegetation cover changes soil properties and reduces soil erosion; The role of vegetation in blocking and intercepting floods, and the protective effect on slope banks).

Ding Yihui is an academician of the Chinese Academy of Engineering, a special adviser on climate change of the China Meteorological Administration, a deputy director of the National Climate Change Expert Committee, and a winner of the first prize of the National Science and Technology Progress Award, the second prize of the National Natural Science Award, the Ho Leung Ho Lee Science Progress Award and the World Meteorological Organization Outstanding Work Achievement Award.

The first point is that sandstorms are produced through a kind of formation of nature, and the second point is that sandstorms mostly occur in seasons such as autumn and spring, because this season belongs to the season of recovery of all things.

It is more common in spring, mainly because sandstorms can transfer organic matter, which is of great help to the ecology.

It is because our temperature has a tropical monsoon climate, and with the influence of some water and soil, there will be sandstorms, which often occur in summer.

When vegetation is destroyed, the water retention capacity of the surface decreases, and rainfall quickly flows into the water system, resulting in flooding.

On the other hand, the siltation of the topsoil into the river further increases the severity of the flood.

Dust storm. It is because the vegetation is gone, the soil is exposed, and it is easy to dry out and form floating soil, and then it is easy to be hung by the wind.

On the other hand, places with poor vegetation also have a great impact on the local microclimate, worsening the local environment.

It can be said that the destruction of vegetation creates a vicious circle.

The vegetation will be severely damaged, the soil erosion of flowing water will be intensified, and the sediment content of the river will increase. During rainfall, the infiltration decreases, the surface runoff increases, and the water volume and water level of the river during the flood season are larger. The ability of vegetation to conserve water decreased, the amount of water in the dry season of the river decreased, and the seasonal variation of river runoff increased.

The hydrological characteristics of rivers generally include runoff, sediment content, flood season, freezing period, water energy resources, flow velocity, river recharge type and water level.

The destruction of vegetation in the upper reaches of the river is easy to cause soil erosion, resulting in the increase of river sediment content. The function of water conservation is weakened, the catchment rate after rain accelerates and the time becomes shorter, and the precipitation with the same intensity and time as before the destruction increases, the water level of the river increases, and the flood season becomes shorter. Instantaneous runoff values may be elevated, etc.

Sand duststorm is a general term for both sandstorm and duststorm, which refers to a severe wind-blown sand weather phenomenon in which strong winds blow up a large amount of sand and dust materials on the ground and roll them into the air, making the air particularly turbid and the horizontal visibility is less than 1,000 meters. Among them, sandstorm refers to the sandstorm formed by strong winds blowing a large amount of sand into the near formation; A dust storm is a storm formed by high winds that sweep large amounts of dust and other fine particles into the air.

Favorable weather conditions for the generation of high winds or strong winds, favorable distribution of sand and dust sources and favorable air instability conditions are the main reasons for the formation of sand and dust storms or strong sand and dust storms. Strong wind is the driving force of sandstorms, and the sources of sand and dust are the material basis of sandstorms, and unstable thermal conditions are conducive to the increase of wind and the development of strong convection, so as to entrain more sand and dust and roll higher.

In addition, the drought and lack of rain in the early stage, the warming weather and the rising temperature are the special weather and climate background formed by sandstorms. The development of convective cells in front of the surface cold front into clouds or squall lines is a small and medium-scale system that is conducive to the development and strengthening of sand and dust storms. The topographic conditions that are conducive to the increase of wind speed, i.e., the narrow tube action, are one of the favorable conditions for the formation of sandstorms.

When the drought and little rain and the temperature warms, the silicic acid on the surface of the silicate loses moisture, so that the surface of the silicate soil colloids and sand particles will have a negative charge, which has a repulsive effect on each other, and becomes an aerosol that cannot be coagulated together, thus forming a sand and dust storm. Dust storms are essentially silicate aerosols with a negative charge.

In summary, these three conditions are required for the formation of a dust storm:

One is the sand and dust material on the ground. It is the material basis for the formation of sandstorms.

The second is strong winds. This is the power basis for the formation of sandstorms, and it is also the power guarantee that sandstorms can be transported over long distances.

The third is the unstable air state. This is an important local thermal condition. Sandstorms tend to occur in the late afternoon and evening, which illustrates the importance of local thermal conditions.

It seems that the problem of mulching and water evaporation must be solved first! Then there is the issue of vegetation (afforestation)! I heard that there is a kind of mulching called mulching, which works very well in Australia and Texas (where there are many tornadoes)!

Among the weather disasters brought by the winter monsoon, there may be cold waves and sandstorms, which are characterized by cold and dryness, and among the weather disasters brought by the summer monsoon, there may be floods and typhoons

Dust storm. The formation of sandstorms is due to:

Global warming.

Deforestation, vegetation destruction, species extinction,

The climate is abnormal. and other factors are inseparable. Among them, the population is expanding.

The resulting overexploitation of natural resources, excessive deforestation, and over-clearing of land are the main causes of frequent sand and dust storms.

So sandstorms are not caused by monsoons.

The research on sandstorms points out that there are four conditions for the formation of sandstorms: first, the sandand and dust materials on the ground, which are the material basis for the formation of sandstorms; the second is the strong wind, which is the power basis for the formation of sandstorms and the power guarantee that sandstorms can be transported over long distances; The third is the unstable air state, which is an important local thermal condition, and sandstorms mostly occur in the afternoon and evening, which shows the importance of local thermal conditions. Fourth, the arid climate environment, sandstorms mostly occur in the winter and spring in the north, and sandstorms will not occur for a period of time after rainfall is good evidence.

1.In winter and spring, the cold air of Siberia enters our country strongly, and it has a strong sand driving force.

2.A large amount of desertified land and desert have been stockpiled with the material to be carried.

3.China's monsoon climate, the winter is mostly northwesterly, and the wind brings sediment above.

In the edge area of the desert, due to long-term drought and little vegetation cover on the surface, the sand and dust on the surface are easy to be blown up and transported when there is a strong wind, but because the sand particle size is large, it is not easy to form a suspension (suspension movement is a necessary condition for small particulate matter to ensure long-distance transport), so it can not be transported over long distances, which is also the main reason why there is only dust and sand is rarely blown in areas far away from sand and dust.

If the wind lasts for a long time, the suspended floating dust can be transported over a long distance, and a sandstorm will occur in the area it passes; When the wind speed weakens to a certain level, the floating dust will fall, and the dust will fall in the area. If it rains at this time, it will form a so-called "mud rain".

China has a monsoon climate, with northwest winds blowing in winter and southeast winds in summer.

The source of sandstorms is the northwest region, which happens to blow northwest winds in winter, so sandstorms in China mostly occur in winter.