THESIS
2010
xii, 85 p. : ill. (some col.) ; 30 cm
Abstract
Observational studies showed that intensified upwelling over the continental shelf in the North South China Sea (NSCS) is strongly controlled by the topography of a widened shelf. A two-dimensional frictional model based on linear barotropic vorticity equation is developed to explore the driving mechanism of this phenomenon under the assumption of small Rossby and Burger number. Physical relations that govern the shelf circulation and upwelling/downwelling are derived to illustrate the mechanism of flow-topography interaction that leads to the intensified over the widened shelf. An elliptic equation solver was then used to solve the model which is nearly elliptic system. The model results show that upwelling/downwelling alongshore winds enhance onshore/offshore cross-isobath transport a...[
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Observational studies showed that intensified upwelling over the continental shelf in the North South China Sea (NSCS) is strongly controlled by the topography of a widened shelf. A two-dimensional frictional model based on linear barotropic vorticity equation is developed to explore the driving mechanism of this phenomenon under the assumption of small Rossby and Burger number. Physical relations that govern the shelf circulation and upwelling/downwelling are derived to illustrate the mechanism of flow-topography interaction that leads to the intensified over the widened shelf. An elliptic equation solver was then used to solve the model which is nearly elliptic system. The model results show that upwelling/downwelling alongshore winds enhance onshore/offshore cross-isobath transport around the head of the widened shelf where a shelf is the narrowest. Shoreward/seaward winds induce the relative maximum alongshore velocity around the head of the widened shelf where a shelf is the narrowest. Curvature of isobaths over the shelf significantly modifies cross-isobath transport. It was found that the maximum cross-isobath transport increases while the slope of the widen shelf increase with a linear relation. The asymmetry circulation of upwelling/downwelling occurs in the linear system while the effect of nonlineaity in the momentum equation is investigated by using a three-dimensional, primitive equation Regional Ocean Model System (ROMS). It was found that the upwelling favorable wind can generate the flow oscillation along the isobaths but the downwelling favorable wind cannot, as a result of conservation of potential vorticity. The water oscillation is depth-dependent when water column is stratified.
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