【摘要】 本文用P-σ混合坐标系五层初始方程模式,模拟了索马里过赤道低空气流的发展过程并对其形成机制进行了讨论.指出,索马里低空气流的发展可分为二个基本阶段:第一个阶段为低空气流在贴近地面的层次上发展,略高的层次上有序的气流尚未形成;第二个阶段为低空气流在近地层继续加强,同时较高层次上也出现了有序的气流.结构分析表明,索马里低空气流一般在700hPa以下,在索马里海岸附近有一个热力性垂直环流,索马里低空气流穿过其中。有关形成机制的模拟实验表明,在边界层中,气流的发展主要决定于非绝热加热的海陆不均匀分布,与地形高低的关系较小.但地形高低对气流的强度、垂直伸展高度和风速轴线随高度的倾斜有影响.在不考虑非绝热加热作用而只考虑地形的模拟实验中,索马里低空气流不能完整地模拟出来.更多还原

【Abstract】 The development of the somali low level jet has been simulated by use of a 5-layer numerical model which includes diabatic physical processes. The results show that the Jet develops first at the boundary layer with 50 hPa thickness above the surface and then at the higher layers. The flow patterns at the lower tropospheric layers are generally the same when the quasi-stationary state arrives. The horizontal and the vertical configurations of the Jet are also described. It is found that there is a thermal vertical circulation between the east African mountains and the west part of the Indian ocean through which the Somali Jet flows. Five different numerical experiments have also been conducted by the same model, with 8-day time integration for each experiment. The purpose of the comparative experiments is 10 understand the dynamics of the Somali Jet and to compare the relative importances of some factors such as mountains, radiative heating and diurnal variation of the solar radiation. The land-sea contrast and large-scale condensation are both included in all the experiments.The simulated results show that the main determinative factor for the development of the Jet in the boundary layer is the differential heating caused by the land-sea contrast, the topo-praphic feature over the east Africa has a less impact on the pattern of the Jet, but it has an evident influence on the intensity and the tilt of the Jet axis. The experiment with only topography can not reproduce the Somali Jet fairlv, it further proves the relative importance of diabatic heating over the topography.更多还原