沙尘暴的形成需具备4个条件.
一是地面上的沙尘物质.它是形成沙尘暴的物质基础.
二是大风.这是沙尘暴形成的动力基础,也是沙尘暴能够长距离输送的动力保证.
三是不稳定的空气状态.这是重要的局地热力条件.沙尘暴多发生于午后傍晚说明了局地热力条件的重要性.
四是干旱的气候环境.沙尘暴多发生于北方的春季,而且降雨后一段时间内不会发生沙尘暴是很好的证据.
春季沙漠的边缘地区,由于长期干旱,而且地表少有植被覆盖,当有大风来临的时候地表的沙尘很容易被吹起且被输移,但由于沙子粒径较大,不易形成悬移(悬浮移动,是小颗粒物质保证长距离输移的必要条件),因此不能长距离输移,这也是距沙尘较远的地区只有降尘而少见扬沙的主要原因.如果风持续的时间很长,形成悬移的浮尘能够被输送到很远的地方,所经过的地区就会出现沙尘暴；当风速减弱到一定程度后,浮尘就会降落,该地就会出现降尘天气.如果此时降水,就会形成所谓的“泥雨”.
从沙尘暴形成过程所需的4个条件看,黄土高原、广袤的沙漠及由人为因素的破坏正处于荒漠化过程中的土地,北方春季末耕种的土地及处于施工过程中的基础设施(如高速公路等)为沙尘暴的发生提供了充分的物质源；而春季北方地区的干旱,又使沙尘暴发生的可能性增强；大风的产生是一种复杂的大气现象,主要是冷锋活动或经纬向环流调整作用的结果.由此可见沙尘暴的产生是多种复杂因素共同作用结果,人类活动对自然界的破坏导致土地荒漠化的加剧,对沙尘暴发生产生了极其重要的作用,而近几年全球干旱(其原因目前尚未知)等异常天气现象也对沙尘暴的发生起了不可估量的作用.所以说人类活动对沙尘暴的产生只起到一定作用,并不能说沙尘暴就是人为因素造成的.
The formation of the sandstorm to have the four conditions.
One is the dust on the ground material.It is the material basis of form sandstorm.
2 it is winds.This is the power of the formation,is fundamental to the power of the sandstorm long-distance transport of guarantee.
Three is not stable air condition.This is an important local thermal conditions.Sandstorm occurs more often in the afternoon that incorporates the evening the importance of thermal condition.
Four is the dry weather environment.Born in the north of the sandstorm multiple spring,and rain after a period of time within a won't happen very good evidence is dust storms.
The edge of the desert in the spring,due to long drought,and surface vegetation cover,when there is little wind comes on the surface of the earth is easy to be blowing dust and sand,but due to lose move large particle size,is formed not easily movable (suspension movement,it is small particle material guarantee to lose the necessary conditions of long distance move),and therefore can not move long lost,this is far from the dust in the dust and rare only micrometeorology main reason.If the wind last time is very long,form the dust suspended loads can be transported to a very far place,through which areas will appear sandstorm; When the winds weaken to certain degree,floating dust will the landing,the dust weather will appear.If the precipitation,can form the so-called "NiYu".
The formation process from the four conditions look,the loess plateau and vast desert and by the destruction of the human factors in the process of desertification is in the land of the north,at the end of the spring farming land and in the construction process of infrastructure (such as high speed road,etc.) for the dust storm occurrence providing full source material; And the spring drought in the north,and the likelihood of the sandstorm strengthened; The winds generated is a complex phenomenon,mainly is the cold air activities or to the circulation of the regulatory role longitude results.This shows the generation of sandstorm is DuoZhong complex factors results of human activity on the natural world to disruption of the desertification intensifies,dust storms happen to have an important role,and in recent years the global drought (the cause isn't yet known) abnormal weather phenomenon also to the dust storm occurrence have played an important role.So that human activities for the generation of dust storms only play a role,and can't say dust storms are caused by human factors.
