Date of Award

8-2002

Level of Access

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Oceanography

Advisor

Vijay G. Panchang

Second Committee Member

Neal Pettigrew

Third Committee Member

Huijie Xue

Abstract

In practical applications, numerical wave models are used as reliable tools to provide near future wave predictions and wave climatology for specific region. Obviously models first should go through extensive validation/verification procedures. Once validated, models can be used in scientific applications to investigate methods for improving performance and to develop better understanding of wave associated physical mechanisms and their interactions in specific field experiments. Two wave transformation models, SWAN and CGWAVE, are used to simulate wave conditions at the Field Research Facility, Duck (North Carolina). The motivation is to examine how well these models reproduce observations and to determine the level of consistency between the two models. Stationary wave conditions pertaining to three different storm-induced bathymetric representations are modeled. It was found that SWAN and CGWAVE reproduced the observed wave behavior to a large extent, but CGWAVE results tended to be somewhat smaller than the SWAN results and the measurements. The differences were attributed to wave-wave interactions and breaking. Otherwise the models showed a high level of consistency. SWAN and CGWAVE were also used to explore other mechanisms reported in the recent literature; the results were either consistent with some observations (in the case of the nonlinear mechanisms) or they shed more light on others (in case of the role of the research pier legs). An operational high resolution wave prediction system for the Gulf of Maine was experimentally developed. Attempts were then made to improve the quality of the SWAN model predictions through the assimilation of observed wave data into the model simulations. It was demonstrated that a simple data assimilation scheme that uses only the observed significant wave height to correct the energy level of the predicted full 2D wave spectrum may improve the quality of wave forecasting model predictions for up to 2 days. Shorter relaxation times were attributed to inaccurate predictions of the wind field and/or inadequate representation of the boundary conditions. The results suggests that a simple and computationally inexpensive assimilation scheme is sufficient and would be of a greater benefit to high resolution operational wave prediction systems for the Gulf of Maine.

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Oceanography Commons

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