NASA - National Aeronautics and Space Administration

The effects of non-breaking surface waves on upper ocean dynamics enter the wave-averaged primitive equations through the Stokes drift. Through the resulting upper ocean dynamics, Stokes drift is a catalyst for the fluxes of heat and trace gases between the atmosphere and ocean. However, estimates of the Stokes drift rely crucially on properly resolving the wave spectrum. In this paper, using state of the art spatial measurements (in-situ and airborne remote sensing) from a number of different field campaigns, with environmental conditions ranging from 2 to 13 ms−1 wind speed and significant wave height of up to 4 m, we characterize the properties of the surface wave field across the equilibrium and saturation ranges and provide a simple parameterization of the transition between the two regimes that can easily be implemented in numerical wave models. We quantify the error associated with instrument measurement limitations, or incomplete numerical parameterizations, and propose forms for the continuation of these spectra, in order to properly estimate the Stokes drift. Depending on the instrument and the sea state, predictions of surface Stokes drift may be underestimated by more than 50%.