正压准地转模式中大地形作用下的低频波

利用包含大地形和常速纬向基本气流的正压准地转位涡度方程，研究了大地形对低频波激发的作用，结果表明，起作用的地形因子主要是地形的最大高度和地形坡度。地形最大高度的作用主要是使Rossby波趋向低频，而地形坡度的作用主要是对Rossby波的稳定性起决定作用，同时适当的地形坡度也可导致低频波的形成。而常速纬向基流在总体上的作用是使波动变得趋向低频，且西风基流更有利于低频（30～60天）波的形成。从纬向波数上看，纬向3波以上的波动更容易出现低频（30～60天）。

Low-frequency Waves Forced by Large-scale Topography in the Barotropic Quasi-geostrophic Model

A barotropic model, including large scale topography and constant zonal basic flow, was used to discuss the effects of large scale topography on the low frequency waves. The results show that the topographic factors which affect low frequency waves are mostly maximun height of topography and topographic slope. The former makes frequency of topographic Rossby waves decrease, and the latter makes Rossby waves instable. Moreover, when topographic slope is optimum, it could also make Rossby wave turn into low frequency waves. Constant zonal basic flow also plays a very important role in determining the instability of forced Rossby waves. In all zonal wave numbers, only the wave at large wave number(3 waves or larger) could be low frequency waves.