Physics of "Saturation-based" dissipation functions proposed for wave forecast models

The dissipation term is one of the three most important source functions of the radiative transfer equation employed by all spectral wave models to predict the wave spectrum. In this paper, the issue of physics of such dissipation functions is discussed. It is argued that the physics presently utilized in the models do not adequately describe currently known features of the wave dissipation process, and the dissipation functions, to a great extent, remain a residual tuning term in spite of important experimental progress in wave breaking studies. A recently suggested 'saturation-based' dissipation function and its connections with the experimental physics are analyzed in detail.