A 2-DIMENSIONAL COMPOSITE GRID NUMERICAL-MODEL BASED ON THE REDUCED SYSTEM FOR OCEANOGRAPHY

The proper mathematical limit of a hyperbolic system with multiple tim e scales, the reduced system, is a system that contains no high-freque ncy motions and is well posed if suitable boundary conditions are chos en for the initial-boundary value problem. The composite grid method, a robust and efficient grid-generation technique that smoothly and acc urately treats general irregular boundaries, is used to approximate th e two-dimensional version of the reduced system for oceanography on ir regular ocean basins. A change-of-variable technique that substantiall y increases the accuracy of the model and a method for efficiently sol ving the elliptic equation for the geopotential are discussed. Numeric al results are presented for circular and kidney-shaped basins by usin g a set of analytic solutions constructed in this paper.