Boundary Conditions in the Navy Coastal Ocean Model

Abstract

Abstract : The explicit treatment of boundary conditions (BCs) implemented in the Navy Coastal Ocean Model (NCOM) is described for the cases of lateral cyclic boundaries, thc air-sea interface, and open lateral boundaries. Cyclic BCs can be specified to configure the NCOM for one dimensional simulations within a vertical plane. The air-sea BCs permit surface focusing using atmospheric pressure, wind stress, surface fluxes for scalar fields (temperature, salinity), and penetrating solar irradiance. A relaxation of sea surface temperature (SST) and sea surface salinity (SSS) to observed or climate fields can also be applied. For the vertical mixing submodels, the surface roughness can be specified and the BC for the turbulent kinetic energy (TKE) can be either the value or flux of the TKE at the surface. A variety of horizontal BCs at the open boundaries are available for the elevation, velocities, and scalar field at the open boundaries. A clamped on a Flather radiation condition can be applied to the elevation and normal depth-averaged velocity. Boundary conditions that can be used for the tangential depth-averaged velocity and baroclinic velocities include a zero gradient, Orlanski radiation, and advective BC. For scalar fields, BC options include prescribed values, Orlanski radiation, and an advective BC. Zero gradient BCs in the horizontal are implemented for the vertical velocity and vertical mixing variables.