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Analytic techniques for short-term ocean current forecasting

White, Andrew James; (2005) Analytic techniques for short-term ocean current forecasting. Doctoral thesis , UCL (University College London). Green open access

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Abstract

This thesis concerns the motion of oceanic vortices and comprises two parts. Part I examines the dynamics of point vortices in a two-layer fluid near large amplitude, sharply varying topography, e.g. continental shelf regions. Topography takes the form of an infinitely long step change in depth and the two-layer stratification is chosen such that the height of topography in the upper layer is a small fraction of the overall depth, enabling quasi-geostrophic theory to be used in both layers even though the topography is large amplitude. An analytic expression for the dispersion relation of free topographic waves in this system is found. Weak lower-layer vortices are studied using linear theory and, depending on their sign, are able to produce significant topographic wave radiation in their wakes. Upper-layer vortices produce relatively small amplitude topographic wave radiation. Contour dynamics results are used to investigate the nonlinear regions of parameter space. For lower-layer vortices linear theory is a good approximation, but for upper-layer vortices complicated features evolve and linear theory is only valid for weak vortices. The motion of hetons (two vortices, one in each layer) and dipoles are also studied. Part II involves the investigation and prediction of the motion of Loop Current Eddies (LCE's) in the Gulf of Mexico. By incorporating the major features of LCE's into a simple eddy model it is attempted to discover if it is possible to deduce the characteristics of a distant eddy from a set of measured velocities at a fixed location and further, predict the subsequent motion of the eddy. First, a circular model for the eddy shape is adopted and the Helmholtz equation is solved in the far-field. Second, a more sophisticated, precessing, elliptical model is developed, the solution involving Mathieu functions. In both cases comparison with actual current meter data is used to demonstrate the validity of the models.

Type: Thesis (Doctoral)
Title: Analytic techniques for short-term ocean current forecasting
Identifier: PQ ETD:602805
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Mathematics
URI: https://discovery.ucl.ac.uk/id/eprint/1446863
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