Once the MIKE 21 SW has been successfully completed, the Matlab processes an output in a flexible mesh format and generate hourly figures for the whole simulation time with color contours and arrows indicating the significant wave height and the wave direction, respectively. The last step is visualizing the model outputs. In order to run MIKE 21 SW on the Matlab shell, which emulates the DOS prompt, the ASCII setup file for MIKE 21 SW should be edited according to the starting time of each forecast simulation. The second step is running MIKE 21 SW on the Matlab shell with the converted wind file from the previous step. The first step is converting the aforementioned wind file to a form readable in MIKE 21 model using the Matlab-MIKE DLL functions, which is developed by DHI and open to public. The Matlab automation sequence program for this study mainly consists of three steps for each cycle of forecast simulation. A series of Matlab programs reformat the wind data and make it suitable to be read by the MIKE 21 model. The wind data is downloaded daily (1:00 AM CDT) into the local machine using automated routines. Also, the model runs in a forecast mode and simulates the wave fields for 60 hours using the wind data from the NCEP NAM wind model.
Along the northern Gulf of Mexico a fine resolution mesh is embedded with a mesh resolution of 0.0005 deg2 while for the rest of the domain the mesh resolution is 0.1deg2. Also, the bathymetric data is converted from Mean Lower Low water (MLLW) datum to Mean Sea Level (MSL) using a correction grid based on NOAA tide gage benchmarks.
The data resolution of 3 arc-second is used for the Louisiana coast and for the rest of the US coast 15 arc-second resolution data is used. The mesh grid for the domain, Gulf of Mexico, is generated using the bathymetric data from US coastal relief model (NGDC/NOAA) and ETOPO-2 model. Detailed description of all the source functions and the numerical methods used in the model are elaborated in Sorensen et al (2004). The integration in time is based on a fractional step approach, where the propagation step is solved using an explicit method. The spatial discretization of the conservation equation for wave action is performed using an unstructured finite volume method. For small-scale applications, the basic conservation equations are usually formulated in Cartesian co-ordinates, while spherical polar co-ordinates are used for large-scale applications. The unstructured mesh approach gives the model maximum degree of flexibility. MIKE 21 SW is a third generation spectral wind wave model based on unstructured meshes.
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