Study On The Influence Of The Earth's Rotation On Oceanic Internal Wave

Ocean internal waves is a kind of waves occurred in continuous density- stratified ocean, the largest amplitude of the fluctuations occurred in the interior of the ocean. Investigation on them is very important not only on studying the phenomena related to themselves but also is helpful for us to understand the interactions of internal waves on the exchange process of mass, momentum, energy, environmental and climate change in the ocean. Furthermore, the understanding for internal waves'behaviours will increase the knowledge about the interactions between internal waves and many other multi-scale ocean processes (for example: internal waves-surface waves, internal waves–current, internal waves-eddy, etc, especially the contribution for large scale movements). In addition, it has great significance guidance to the marine engineering and marine military and so on.In this thesis, a kind of WKB approximate solutions is derived by using WKB method for the internal waves in continuous density-stratified ocean under the'non-traditional approximation'that is to include a complete effect of the earth'rotation. The vertical velocity modes obtained from the WKB approximate solutions are compared with the numerical result in detail in order to test the validity of WKB approximate solutions. The study shows that the WKB approximate solutions proposed are consistent with the numerical results for the buoyancy frequency N(z) varies gradually with the ocean depth z. Furthermore, the effects of the earth'rotation on the internal waves are studied in the present of background current. The results indicate that the horizantal component of the earth'rotation can not be ignored generally. Therefore, it is very important to retain the horizantal component of the earth'rotation in the studying on internal wave about its generation, evolution and dissipation.The interface wave is a special case of internal wave, it is usually studied by using the model with two-layers fluid with different density. Although the existing investigations described the basic behaviours of the interfacial waves from different aspects, there appear to be no one taking into account of the influence of the earth rotation on the interfacial waves. However, this influence could not be neglected when we study the wave-induced stress and its driven effect on currents of the earth's rotation, at least for surface waves. In this thesis, the results of Sun et al. (2003) for surface waves were extended to a more general case of two-layer fluid with a top free surface and a flat bottom, the solutions were deduced from the general form of linear fluid dynamic equations with the f-plane approximation for geostrophic small amplitude surface waves and interfacial waves, and wave-induced tangential stress were obtained based on the solutions presented. The results obtained here have potential important applications for understanding the behaviours of the interfacial waves, the interaction between the surface wave and the interfacial wave, ocean dynamics and in ocean engineering.