模式大气对于大尺度地形动力强迫作用的非线性响应

本文与文献1]相对应,利用一个非线性初始方程谱模式,研究了中、高纬度理想化的大尺度地形以及北半球实际地形的动力强迫作用对于冬季行星尺度的大气定常波的影响。计算结果证实,根据线性模式的数值试验结果所做的定性分析在非线性情形下仍然是成立的,同时,非线性扰动流场也与线性流场有明显的差异,在纬向平场基本气流相对较弱的地区或垂直层次上差异尤为显著。数值试验表明,北半球实际地形强迫的大尺度扰动,在对流层低层以及对流层上部的中、高纬均主要表现出纬向波数为2的行星波,但是在对流层上部的低纬地区3波分量比较明显。中、高纬的大地形动力强迫作用,对于低纬太平洋高空的反气旋和气旋环流的形成有重要的贡献。 

NONLINEAR RESPONSE OF A MODEL ATMOSPHERE TO LARGE SCALE OROGRAPHIC FORCING

A nonlinear steady-state, baroclinic, primitive equation, three-dimensional spectral model, in which Newtonian cooling, Rayleigh friction and biharmonic diffusion are included, is used to investigate the effects of idealized and actual topography on the planetary scale, forced stationary waves in Northern winter.Computational results confinn the qualitative analysis of numerical experiments in terms of associated linear model, meanwhile significant differences between linear and nonlinear solution are also found, especially where the basic flow is relatively weak. It is shown that the high-and mid-latitude response of the model atmosphere to Northern Hemisphere topography is dominated by zonal wavenumber two, but for the low latitude response at the upper troposphere the component for wavenumber three is evident. The mid-and high-latitude orographic forcing makes a substantial contribution to the maintenance of the cyclonic circulation over the eastern tropical and sub-tropical Pacific as well as the inverse circulation over the western Pacific in the upper troposphere.