SOME EXPERIMENTS WITH EXPLICIT FINITE-DIFFERENCE SCHEMES IN A LINEAR BAROTROPIC OCEAN MODEL

A special explict finite-difference scheme, denoted the TSDM-(Time Staggered lattice D Modified) grid and described by A. M. BRATSETH (1983, Monthly Weather Review, 111, 663-668), is tested in a linear barotropic ocean model with a simple geometry. The grid is based on a time staggered lattice D-grid. The TSDM-grid permits an increase of the timestep relative to the lattice C-grid. It also reduces the problems with nonlinear instability. The results from numerical computations with the TSDM-grid are compared with results from the same computations in which the well known lattice C-grid was used. The TSDM-grid does not show any better performance than the C-grid in any of the computations. In one of the experiments with the TSDM-grid a significant amount of noise showed up in the results. This noise was not seen in the results from the C-grid, and it shows that the TSDM-grid does not manage to handle properly the short gravity waves.