A Comparison of Several Coastal Ocean Models

Several ocean models that are being used for coastal ocean simulation and prediction were tested for their ability to simulate physical processes of importance in the coastal ocean. The models tested were the Princeton Ocean Model, the Estuarine and Coastal Ocean Model, semi-implicit version (ECOM-si), the Sigma/z-level Model, and the S-Coordinate, Rutgers University Model (SCRUM), Version 2.1. The basic processes for which the models were tested included advection, vertical mixing, propagation of surface, internal, and coastal trapped waves, and the formation of upwelling and downwelling fronts. The model tests revealed some particular problems and limitations of the individual models and parameterizations. The forward time-differencing scheme used by ECOM-si suffers from significantly higher truncation error than the leapfrog and Adams- Bashforth schemes used by the other models. The sigma vertical coordinate system can suffer from advective overshoot if there are large changes in depth between adjacent gridpoints, and also from spurious diffusive effects, depending on how the horizontal diffusion is treated. The step-like bottom of a z-level vertical grid in which the bathymetry is rounded to the nearest model level can incur error due to the inaccurate representation of the bottom depth. The Crank- Nicolson treatment of vertical mixing in SCRUM 2.1 generates noisy, inaccurate vertical mixing due to diffusive overshoot when the vertical eddy coefficients are large.Naval Research Lab Stennis Space Center MS Coastal and Semi- Enclosed Seas Section is the author of 'A Comparison of Several Coastal Ocean Models' with ISBN 9781423554035 and ISBN 1423554035.