The Wave Boundary Layer Depth and Actively Coupled Wind-driven Wave Scales

A one-dimensional energy and momentum closure scheme at the air-sea interface is presented for open ocean conditions. The momentum closure was evaluated using two different wave growth parameterizations, including Komen et al. (1984) and Janssen (1991). The results suggest that both wave growth parameterizations are not statistically significantly different under forcing conditions < 1 Pa. The one dimensional energy and momentum balance, combined with an exponential decay of the wave-induced perturbations, indicates the presence of a wave boundary layer above the air-sea interface that is reaching maximum values O(10¹) m under strong forcing. From the wave boundary layer depth an “effective” wave scale, assumed to correspond to the longest waves actively coupled with the wind, was defined. The effective wave scale was analyzed in the context of wave age and ultimately associated to wave breaking dynamics, such as whitecapping intensity and bubble plume penetration depth.