Model Grid and Topography

The sea floor is represented by model cells, where the normal horizontal and vertical flux from the bottom into the cells is set to zero. This requiies a data set with information on the Baltic Sea bathymetry. In the late 1980s, at the outset of three-dimensional modeling of the Baltic Sea, gridded topographic data with sufficient accuracy and resolution were constructed from nautical maps, data from research cruises, and other data sources. One of the most complete data sets, used today for many Baltic Sea model projects as a standard, was compiled and regularly updated by Seifert et al. (2001), see Section 20.2.5. 

A critical issue is the proper choice of the horizontal and vertical model resolution. The baroclinic Rossby Radius is a typical horizontal scale for eddies and wavelike processes. If this scale, that varies in the Baltic from less than 1 km to 7 km (Fennel et al., 1991), is not resolved, adjustment processes by waves are filtered out and the model dynamics is 

FIGURE 19.1 Configuration of the 3 nautical mile model. Grid lines indicate (10x10) model cells, the bold line shows the uniform resolution area, black squares denote the model river boxes, and the gray scale corresponds to water depth in meters. 

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