MODELING THE RESPONSE OF AN IDEALIZED COASTAL OCEAN TO A TRAVELING STORM AND TO FLOW OVER BOTTOM TOPOGRAPHY

To validate a three-dimensional hydrodynamic model for use in coastal waters, two test cases with idealized geometry and forcing functions w ere performed. The tests involve the barotropic and baroclinic respons e of a coastal ocean with a uniform alongshore shelf to the passage of a storm and the circulation induced by flow over a topographic featur e. The model used in this study is the estuarine, coastal, and ocean m odel developed by Blumberg and Mellor. The model is three dimensional and solves for three components of the current field, temperature, and salinity. The model has a terrain-following sigma (sigma) coordinate system, a coastal-following curvilinear grid in the horizontal, and an embedded second-order turbulence closure submodel to provide vertical mixing coefficients and uses the free surface as a prognostic variabl e. At the open boundaries, a flow relaxation scheme (FRS) has been imp lemented to pass out internally generated disturbances with minimum re flection. The results from the first test case demonstrate that the mo del successfully reproduces the expected theoretical response to a tra veling storm. Both standing and propagating shelf waves with the prope r spatial structure are found. In the upper part of the ocean, wind-ge nerated oscillations are the dominant response. In the second test cas e, a stationary anticyclone forms over the topographic feature and a c yclonic eddy is shed downstream in a time of the order of the advectiv e timescale, in agreement with theory and previous studies. When inves tigating the long-term evolution, the model simulations reproduce the baroclinic instability mechanisms expected from analytical considerati ons.