沙漠-绿洲大气边界层结构的数值模拟

利用美国NCAR新版中尺度MM5V3．6非静力平衡模式，采用三重嵌套的模拟方法，模拟研究了沙漠绿洲的环流及边界层特征。结果表明：在没有西风气流背景的影响下，绿洲沙漠环流和大气边界层结构是对称的。沙漠绿洲改变了原有沙漠地区环流结构及温、湿场的分布，绿洲上空大气下沉，沙漠上空大气上升，从而产生了绿洲上空大气冷干，沙漠上空大气暖湿的边界层特征。绿洲边缘形成了由干到湿的强湿度梯度带围绕着绿洲，起到了保护绿洲的作用。在有西风背景气流的影响下，绿洲沙漠环流和大气边界层结构是非对称的。但是，西风背景气流的存在可以破坏绿洲系统对称的环流结构，不利于绿洲系统的稳定发展。

Numerical Simulation of Boundary Layer Structure in Desert-Oasis

Using the NCAR nonhydrostatic mesoscale model MM5V3. 6 and triple-nested simulation method, the circulation and boundary layer characteristic over desert and oasis were simulated. The results showed that the oasis-desert circulation and atmospheric boundary layer structure are symmetric without the influence of the background westerly air flow. The desert-oasis changes the circulation structure, temperature and humidity fields of original desert area. The vertical motion is downwards over oasis and upwards over desert, then the air is dry and cold over oasis; but warm and moist over desert. There is the wet air colume around oasis, which plays a key role in protecting the oasis. The oasis-desert circulation and atmospheric boundary layer structure are asymmetric due to the influence of the background westerly air flow. Because of the background westerly air flow, they can break the circulation structure of oasis system symmetry, which is unfavourable for the steady development of oasis system.