Wave–current interaction in the Southern North Sea

The wave–current interaction process in the Southern North Sea is studied using a coupling scheme which allows the synchronous data transfer between a wave and a tide/surge model. The procedure is carried out up to coastal waters by means of a grid nesting procedure. During the analysis period, an underestimation of wave parameters and surge effect was observed, mainly as a result of the misrepresentation of the wind field. The effect of coupling on wave height (Hs) and wave period (Tm02) is about 3% and more than 20%, respectively. The nesting procedure (which is equivalent to increasing the spatial resolution of the simulation) tends to improve the qualitative agreement between computed wave parameters and measurements. The same trend is observed for the computed surge effect. Spectral characteristics, like directional spreading and energy distribution, are also improved when nesting is included. In the fine grid, which covers the Belgian coastal area, the radiation stress effect was quantified and was found to be as important as considering the effect of a wave-dependent surface stress in the fully coupled system. The order of magnitude of the excess current (with respect the uncoupled version) produced by this latter effect is about 10 cm/s.