Quasi-geostrophic equations revisited: The case of the ocean

Oceanic circulation on the beta-plane demands the presence of (at least) two scales of the motion to describe completely the flow structure and evolution both in the central-eastern area of the basin and in the western boundary layer. In each of the two regions of the basin, well-established quasi-geostrophic vorticity equations govern the flow. However, since these two regions are physically connected, a single and general vorticity equation is requested to hold in the whole basin. In the present investigation, the inference of this last equation is analysed by comparing some methods found in the literature with another which is put forward by the authors.