从地气耦合角度讨论沙漠的成因

Discussion on desert formation from viewpoint of coupling of the earth and atmosphere

沙漠的成因是干燥气候和强大风力的产物。中国的大沙漠多在地壳运动相对稳定的地区,如塔里木地区、准噶尔地区、阿拉善地区、鄂尔多斯地区以及内蒙古东部地区等,因此可以认为,可能还有地下因素参与了沙漠的形成。其形成机制可能是:地壳运动稳定地区地下的携热水汽或其他携带热量的气体不易逸出,这样就不易在稳定地区大气中造成低气压状态,因而不易吸引冷热气团来交会降雨以及不易形成水汽的垂直对流降雨,这些后果叠加在更大范围的气候干燥背景上,使这些地区更加干旱,于是形成大沙漠。这种沙漠的扩展又在一些原来不是沙漠的农业区形成沙漠或沙地。

It is well known that the formation of the desert is due to the dry climate and the strong wind. It is found that big deserts in China lie in the relatively stable geological region, for example, Tarim region, Jongger region, Alshan region,Erdos region, and lnner Mongolia region etc. It indicates that some subterranean causes also play a role in the desert formation. The mechanism is maybe that the water vapor and other hot gases are difficult to emit out from the underground in the geologically stable region,and so it is difficult to form low air pressure in the region. Therefore it is difficult to attract the intersection of the cold and warm air mass or form the vapor vertical convection to cause precipitation. These consequences superpose on the large background of climatic dryness to strengthen the drought and form the big desert. The extension of the desert will cause the desertification of the surrounding agricultural regions.