On the Nesting of Grids in Nonhydrostatic Computations

Abstract

The use of a nested grid system in the numerical integration of a nonhydrostatic system of hydrodynamic equations is investigated. Computational problems introduced by the abandonment of the hydrostatic approximation are noted. Tests in which a solitary inertial gravity wave is propagated through a periodic domain indicate that the computational noise due to the grid interaction is negligible when an upstream or a two-step Lax-Wendroff differencing scheme is used. A precipitating cumulus cloud is then simulated with several arrangements of grid points. The ?nested? results differ very little from those of the corresponding ?fine grid? simulation. Computational noise cannot be detected in the grid interaction zone even when this zone is in the active cloud area.