Description of the Navy Coastal Ocean Model Version 1.0

Abstract : This report provides a description of the Navy Coastal Ocean Model (NCOM) Version 1.0. The model has a free surface and is based on the primitive equations and the hydrostatic, Boussinesq, and incompressible approximations. The model uses an Arakawa C grid, is leapfrog in time with an Asselin filter to suppress timesplitting, and uses second-order centered spatial finite differences. The propagation of surface waves and vertical diffusion is treated implicitly. A choice of the Mellor-Yamada Level 2 or Level 2.5 turbulence models is provided for the parameterization of vertical mixing. The horizontal grid is curvilinear. The vertical grid uses sigma coordinates for the upper layers and z-level (constant depth) coordinates for the lower layers, and the depth at which the model changes from sigma to z-level coordinates can be specified by the user. The combined vertical coordinate system provides some flexibility in setting up the vertical grid and easily allows comparisons to be made between simulations conducted with sigma and z-level coordinates. The inclusion of a source term in the model equations simplifies input of river and runoff inflows. Some limitations of the model are discussed.