EFFECTS OF NUMERICS ON THE PHYSICS IN A 3RD-GENERATION WIND-WAVE MODEL

Numerical errors in third-generation ocean wave models can result in a misinterpretation of the physics in the model. Using idealized situations, it is shown that numerical errors significantly influence the initial growth, the response of wave fields to turning winds, the scaling behavior of model results with wind speed, and the propagation of swell. Furthermore. the numerics may influence the dynamic interaction between wind sea and swell. Surprisingly, fetch-limited model behavior is hardly influenced by numerical errors in wave propagation. Simple modifications of the numerics are presented to reduce or eliminate such errors. The impact of numerical improvements for realistic conditions is illustrated by performing hindcasts for the Atlantic basin and for a smaller region off the east coast of the United States.