In this paper the author presents two simplified methods of calculating natural frequency for multi-degree-of-freedom systems, one of which is equivalent stiffness a n d equivalent mass method, the other of which is dynamic displacement method.

Taking Songliao Plain as an example, the proposition that strong stress makes a fragile environment into catastrophe is demonstrated for the first time.

Many factors have impact on local circulation such as surface friction,topography,thermal forcing and so on.

For the barotropic potential vorticity equation (named the barotropic model) on a β-plane channel its solution is a stationary, wave-like pattern under a certain thermal forcing, while a quasi-periodic oscillation between two essential flow patterns appears if north-south thermal heating and wave-like topography are added as the .

Dynamic and numerical methods are used to discuss the atmospheric response imposed by SST thermal forcing.