热带大气中的地形强迫运动

The orographic forced motion in tropical atmosphere

摘要:

本文研究了在基本气流无切变和有切变的情况下地形对低伟大气大尺度定常运动的影响。从赤道β平面的线性化正压原始方程出发,求得一个解析形式的地形影响函数。对它的分析表明:大气的受迫运动不仅取决于越过山脉的基本气流的方向,而且还与山脉所处的纬度以及山脉的尺度有关。当适度的西风越过山脉时,会在背风侧形成地形槽。在线性模式中,基本气流的东西风切变对地形强迫波的经向伸展范围起限制作用。利用本文的模式,对东南亚近赤道地区的气压场和流场进行模拟,其结果与观测事实定性一致。最后,本文还讨论了越赤道气流通道的形成机制。

Abstract:

The effeet of terrain on large scale steady atmospheric motion in tropics is studied for uniform and non-uniform basic flows. The analytic formula of orographic influence function is derived from the lineanized barotropic primitive equation on equatorial β-plane. The analysis shows that the forced atmospheric motion depends not only on the direction of the basic flow which crosses over the mountain,but the latitudes and scale of the mountain as well. As moderate westerly crosses a mountain; orographic troughs form in the leeside. It seems that some kind of non-uniform basic flow may make the meridional extent of orographic forced motion confined.Using this model,the pressure and flow patterns near the equatorial area of south east Asia are simulated the result qualitatively consists with the observed features,Finally,the formation mechanism of the channels of cross-equatorial curent is discussed.