The stability of atmospheric stratification is another decisive factor for the formation of dust storms. Taking Hexi area of Gansu Province, where the most frequent regional strong sandstorm occurs, as an example, it is located on the northwest passage under the southeast of cold air. Generally speaking, in winter and spring, especially in spring, there are often strong cold air intrusions, and there are few plants in spring. The temperature of desert and bare surface rises rapidly. As long as it is sunny for two or three days, the temperature of ground can rise very high. If the strong cold air passes through the area around noon, the unstable temperature stratification of upper cold and lower warm can be formed. Sandstorm often occurs at this time.

沙源都是些什么东西呢？它们是怎么来的呢？我们能“消灭”或封闭这些物质吗？下面我们就从沙尘源的形成来寻找答案。

What is Shayuan? How do they come from? Can we "eliminate" or seal off these substances? Let's look for the answer from the formation of dust sources.

从我国北方地区沙尘源的形成看，一类是自然形成的第四纪沉积、堆积物；另一类是人类生产活动堆积物。前者有风成沙、沙砾戈壁、风蚀劣地、沙质粘土、第三纪红色沙岩、现代流水冲积物、湖积物、黄土等。这些沙尘源物质量大且分布面积广，为强沙尘暴的形成提供了丰富的物质基础。后者有尾矿砂、废弃物、炉灰等堆积物和开垦耕地的裸露地面等，比如退化的森林草地、没有植被覆盖的干松土地和城乡建筑工地的沙土堆。近年发生的沙尘暴中，沙质草地和旱作耕地是主要沙源。从自然成因上看，人类无法消除沙尘暴。但从人类自身活动来看，乱砍滥伐和对土地、水资源的不合理利用而加速沙尘暴发生的负面作用是可以消减的，可以在一定程度上消减沙尘暴发生的频率和强度。

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