Forced synoptic coastal-trapped waves along the southern African coastline

Master Thesis


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University of Cape Town

The presence of subinertial (2 to 20 day) oscillations in sea levels and currents over the continental shelf surrounding southern Africa is well-documented, however presently available observational data alone are largely ~nsuitable or insufficient to adequately characterise the shelf circulation in terms of coastal-trapped wave (CTW) theory. In this dissertation, an analysis of atmospheric pressure and sea level data from 1980 to 1990, a scale analysis of the equations of motion and numerical modelling are used to characterise the subinertial coastal-trapped wave motions off the west coast and south coasts of southern Africa. Appropriate scaling of the equations of motion and numerical analyses of the subinertial CTW response at a number of locations along the west and south coasts of southern Africa indicate that the large scale response of shelf waters to synoptic scale or "weather band" atmospheric forcing is predominantly barotropic. This permits the use of the linear, vertically integrated, shallow water wave equations on a J-plane to model the response of the West Coast shelf waters to "weather band" atmospheric forcing. The CTW dispersion curves have been calculated for a number of shelf profiles along the West and South Coast and are used in the interpretation of the sea level analyses and the numerical modelling results, and further to investigate the effect of increasing water column stratification on the subinertial CTW response

Bibliography: pages 209-221.