The model domain is composed of one or more regions in latitude, longitude, and depth. Latitude and longitude are specified in degrees east of Greenwich and depth is in centimeters from the surface downwards. Each region is defined by its bounds and resolution at those bounds. Within each region, resolution may be constant or smoothly varying but there must be an integral number of grid cells contained within the region`s bounds.
If the resolution at both bounds of a region is the same, then resolution within the region is constant. If the bounding resolutions differ, resolution varies smoothly across the region to make the transition. The functional for the variation is arbitrarily taken to be a cosine. Regions sharing a common boundary have the same resolution at that boundary and the first derivative is zero at the boundary to minimize effects of discrete jumps in the numerics. In the vertical, the last region allows a stretching factor applied to the analytic function to provide a more drastic fall off of resolution to the bottom if desired.
In each of the following examples, a grid domain and resolution is built by specifying bounding coordinates and resolution for each region.