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UBC Theses and Dissertations

Geophysical observations of nonlinear internal solitary-like waves in the Strait of Georgia Wang, Caixia


A novel observational method for studying internal features in the coastal ocean is devel- oped and tested in a study of large nonlinear internal solitary-like waves. Observations were carried out in the southern Strait of Georgia in the summers of 2001 and 2002. By quantitatively combining photogrammetrically rectified oblique photo images from a circling aircraft with water column data we track a number of internal wave packets for periods of up to one hour and obtain a more complete view of internal waves, including propagation, oblique interaction, and generation. First, the applicability of various weakly nonlinear theories in modeling propagation of these large waves is tested. Both two-layer and continuous linear, KdV (Korteweg-de Vries), and BO (Benjamin-Ono) models are applied with and without background shear currents. After background shear currents are included, it is found that a continuously stratified BO equation can be used to model propagation speeds within ob- servational error, and that this is not true for other theories. Second, four observed oblique wave-wave interactions including two Mach interactions, one interaction which varied from known interaction patterns, and one very shallow angle regular interaction are analyzed. An existing small-amplitude theory is applied but is found to overestimate the likelihood of Mach interaction at large amplitude. Finally, large-scale aerial surveys are mapped. Using speeds typical of observed waves, their time and place of origin are predicted. It is found that the observed waves are generated at the passes to the south of the Strait of Georgia and are released into the Strait after ebb tides.

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