A Nested Primitive Equation Model for Oceanic Applications

Abstract

An interactive, nested primitive equation model for oceanic applications is introduced. The model has two components that interact, which we shall call the coarse and the fine grid regions. The fine grid region is nested entirely within the domain of the coarse grid region. The interaction is achieved by an interpolation of the coarse grid fields to obtain boundary conditions for the fine grid region and by an averaging of the tendencies of the prognostic variables on the fine grid to force the coarse grid model. The nested model is applied to two test problems relevant to oceanic phenomena?a barotropic modon and a baroclinic vortex. In each case, nested calculations with 3:1 and 5:1 grid ratios perform quite well, and even ratios of 7:1 are able to reproduce the solution reasonably well while the features are mostly contained within the fine grid region. These results indicate that the interactive nested model approach introduced here may provide an accurate and cost-effective approach to problems that have multiple spatial scales and/or open boundary condition requirements.