A Two-Time-Level, Three-Dimensional Semi-Lagrangian, Semi-implicit, Limited-Area Gridpoint Model of the Primitive Equations

Abstract

A two-time-level, three-dimensional semi-Lagrangian, semi-implicit primitive equation gridpoint model that incorporates a sophisticated physics package is presented. It is shown to give accurate 24-h forecasts when integrated over a limited area using a 1.5°?1.5° Arakawa C grid in the horizontal and 16 levels in the vertical for time steps up to 2 h. Also, it is shown to be as accurate as, and approximately twice as efficient as, a three-time-level semi-Lagrangian scheme for time steps up to 2 h but slightly less accurate for a 3-h time step. Finally, it is shown to give accurate forecasts on a 0.5°?0.5° horizontal grid, again using 16 vertical levels, for time steps up to 40 min.