Statistics of breaking wave fields with a multilayer numerical framework*

Wave breaking is a distinct feature of ocean surface waves at moderate to high wind speeds. They generate widely observable whitecaps and greatly enhance the air-sea gas exchange and upper ocean mixing. Wave breaking is highly nonlinear, intermittent in space and time, and multi-scale as the underlying wave spectrum is; these features create difficulties for both analytical and numerical models. We simulate an ensemble of phase-resolved breaking wave fields in the physical space, where strong non-linearities including wave breaking are modeled despite no surface overturning. This is achieved using a novel multi-layer framework, which generalizes the single-layer Saint-Venant system into a multi-layer and non-hydrostatic formulation of the Navier-Stokes equations. The modeled wave fields show statistics of breaking that are in good agreement with field measurements. We propose a scaling of the breaking statistics solely based on wave properties and discuss the implications for previous empirical formulations.