Improved Spectral Wave Modelling of White-Capping Dissipation in Swell Sea Systems

An improved method for computing the dissipation by whitecapping in full spectral discrete wind wave models is presented. In this method the rate of dissipation of a certain spectral wave component is determined by the cumulative wave steepness of all spectral components with lower frequencies. This method is known as the cumulative wave steepness method (CSM) and was described by Van Vledder and Hurdle (2002). In this paper some improvements of the CSM are presented which are related to directional and scaling effects. The improved CSM was implemented in the latest release of the SWAN model (version 40.31 of February 2004) and a calibration against a parametric growth curve was performed. Further, the benefits of the CSM in swell-sea systems are illustrated and compared to the method of Komen et al. (1994).