Use of Orthogonal Curvilinear Grids for the Representation of the Littoral Ocean Environment

The effective representation of the littoral ocean environment has been a long-standing challenge for the Modeling and Simulation (M&S) community. The need for such a representation continues to grow, as the U.S. Navy refocuses from deep ocean to littoral missions. One of the greatest challenges of the littoral region is the wide range of spatial and temporal scales that must be represented. For example, the cross-shore gradients of important oceanographic parameters are typically an order of magnitude larger than the along-shore gradients. Unfortunately, the representation techniques typically employed by the real-time M&S community are not well suited to this extreme range of scales. These representations have included regular Cartesian and geodetic grids, as supported by the IEEE 1278.1a-1998 Gridded Data protocol. This paper describes the application of grids based on an orthogonal curvilinear system to the littoral environment. Orthogonal curvilinear grids were originally developed by the computational fluid dynamics community to improve the simulation of fluid flow. Such grids are now routinely used in numerical models of the littoral ocean environment. They allow a wide range of spatial scales while preserving key boundaries and maintaining some of the traditional advantages of gridded representations. One of the distinctive advantages of the use of an orthogonal curvilinear grid systems is the economy of computational and storage resources that can be attained. Methods for generating operational grids and practical aspects of employing them in the STOW Synthetic Natural Environment are discussed.