干旱区绿洲诱发的中尺度运动的模拟及其关键因子的敏感性实验

Numerical Simulation of OasisInduced Mesoscale Atmospheric Flow and Its Sensitivity Test of Key Factors

利用一个非静力平衡的、高分辨的、二维中尺度大气数值模式 ,并在仅考虑简单陆面过程的情况下 ,模拟了干旱区中绿洲所诱发的中尺度运动 ,并进行了这种中尺度大气运动的强度对绿洲水平尺度、绿洲与周围环境的水平热力差异、大尺度背景场水平风速和大尺度地表加热率等一些重要物理参数关系的敏感性实验研究。研究发现 :中尺度大气运动强度随水平热力差异的增大而加强 ,随背景场水平风速和大尺度地表加热率增强而分别减弱。但随绿洲水平尺度的变化并不像前三个因子一样为单调函数 ,而是在绿洲水平尺度为 2 0km时中尺度大气运动最强 ,绿洲水平尺度更大或更小时中尺度大气运动强度均会减弱。通过统计甘肃省河西地区的绿洲水平尺度分布规律 ,发现绿洲分布最集中的尺度在 15 2 5km 。

Using a nonhydrostatic, highresolutional and two dimensional mesoscale atmospheric numerical model, to take account of the condition of a simple land surface process, oasisinduced mesoscale atmospheric flow is simulated. The sensitivities of the mesoscale atmospheric flow to oasis horizontal spatial scale, thermodynamical difference between oasis and near desert, largescale horizontal wind speed, largescale surface sensible heat flux are studied. It is found that the oasis induced mesoscale atmospheric flow becomes strong with an increase of thermodynamical difference between oasis and near desert, and it becomes weak with an increase of large scale horizontal wind speed and large scale surface sensible heat flux, but change of intensity of the mesoscale atmospheric flowwith horizontal spatial scale of oasis isn't a monotonous function. The mesoscale atmospheric flowshall be the strongest when horizontal spatial scale of oasis is about 20 km, and it shall become weak when oasis horizontal spatial scale is smaller or larger. At the same time, the distribution of horizontal spatial scales of the oases in Hexi region is analysed, and it is found that the scale in which oases come in great numbers is 15~25 km. This scale is mainly identical with the scale in which oasis can induce the strongest mesoscale atmospheric flow.