边界层动力学中的Ekman动量近似

ON EKMAN MOMENTUM APPROXIMATION FOR BOUNDARY LAYER DYNAMICS

自由大气中,大气运动的基本状态是地转风,近年来发展的地转动量近似,是为了进一步研究非均匀地转流的动力学问题,然而,在边界层大气中,运动的基本状态是经典的Ekman流,所以对边界层运动来说,地转动量近似是不合适的,需作一推广。本文提出了一种所谓Ekman动量近似,它相似于自由大气中的地转动量近似,并讨论了Ekman动量近似的物理基础,对边界层的风场结构及边界屋顶部的垂直速度也作了详细分析。

In the free atmosphere, the geostrophic wind is the basic state of the atmospheric motion. The so-called geostrophic momentum approximation has been well developed to study the dynamics of non-uniform geostrophic wind. However, in the boundary layer, the basic motion is not geostrophic but Ekman flow. Thus, the geostrophic momentum approximation has to make some changes to characterize the feature of boundary layer. The purpose of the present study is to suggest an Ekman momentum approximation, which is similar to geostrophic momentum approximation in the free atmosphere. The physical bases of Ekman momentum approximation are studied in the paper. The wind structure and vertical motion at the top of the boundary layer under the approximation are studied in detail.