荒漠绿洲边界层结构的数值模拟

Numerical Simulation of the Atmospheric Boundary Layer Structure Around Oasis

陆-气相互作用和中小尺度天气系统的研究中,水平不均匀边界层和水平不均匀地表的强迫作用都是重要的物理过程.本文用已建立的陆面过程与大气边界层耦合模式(BLCM),较详细地研究了草地周围为荒漠(半沙漠)的地表植被不均匀而造成的边界层结构特征和局地环流及其昼夜变化.通过边界层顶影响自由大气不同尺度的运动.模式结果揭示出最强的上升和下沉运动是发生在荒漠-草地间动力和热力不连续的界面附近,且呈现出不对称性.

The horizontal heterogeneity of surface forcing and the structure in the planetary boundary layer is of importance for the studies of air-land interactions and small and mesoscale atmospheric processes. In this paper, a two-dimensional model in which atmospheric boundary layer is coupled with a land surface process model (LPM) has been developed. It is indicated from the simulation of the model that non-homogeneous vegetational distribution, a patch of grassland is embedded in semi-desert, results in the local thermal and dynamical structure of the PBL and corresponding circulation. These characteristics influence on different scale motions of upper atmosphere through the transports of water vapor, heat and momentum at the top of PBL. Modeling results also show that the maximum updraft and downdraft occur around the grass-desert marginal areas where the dynamical and thermodynamical properties of PBL are uncontinuous.