5. DYNAMIC SIMULATION OF COASTAL CURRENTS WITHIN THE 

 MISSISSIPPI SOUND AND ADJACENT CONTINENTAL SHELF 



The three-dimensional numerical model of coastal currents as described in 

 previous chapters has been applied to simulate the tide- and wind-driven 

 currents in the Mississippi Sound and adjacent continental shelf waters of the 

 Gulf of Mexico. As shown in Figure 5.1, the horizontal grid is composed of 

 116 grid points in the y-direction and 60 grid points in the x-direction. The 

 smallest grid spacing in the computational domain is on the order of 1 Km. 

 Figure 5.2 shows the bathymetry of the domain in meters. The domain consists 

 of two open boundaries, one along the East and one along the South. Boundary 

 conditions along these open boundaries must be properly prescribed. For the 

 computation of tidal currents in our study, these boundary conditions are 

 provided by a numerical tide model for the entire Gulf of Mexico (Reid and 

 Whitaker, 1981). The numerical grid used in their study is shown in 

 Figure 5.3. 



5.1 Tidal Currents 



Tides in the Gulf of Mexico 



Gulf tides differ from tides in most other places in the world due to the 

 dominance of the diurnal components Kl, 01 and PI collectively over the 

 semi-diurnal components M2 and S2, except along the western Florida coast. 

 Platzman (1972) and Hensen (1974) found that the period of the lowest mode of 

 long gravity waves in the Gulf might be quite close to the diurnal tide 

 period, hence suggesting a quasi-resonant condition. Garrett (1975) accounted 

 for the possible influence of the tidal impedance of the adjoining seas, which 

 can influence the possible reasonant modes. Reid and Whitaker (1981) 

 developed a numerical tide model for the Gulf based on the 

 vertically-integrated, linearized, Laplace tidal equations in spherical 

 coordinates to portray the barotropic response of the Gulf to tidal forcing. 

 Forcing at ports (Florida strait and Yucatan Channel) was also included with 

 an impedance type condition. Detailed data from 20 tidal gages located in 

 open coastal waters of the Gulf were used for the fine tuning of their model. 

 Their study on the Gulf tides, while confirming that diurnal tide is primarily 

 a co-oscillating tide driven by the adjoining Atlantic Ocean and Caribbean 

 Sea, is by far the most complete and provides a useful option to supply 



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