A body of theoretical work following J. Miles (1957) predicts that the wave-coherent fluctuations of the pressure and the velocity in the air flow above the ocean contribute the most to the wind-wave momentum and energy exchange. The ability to identify these fluctuations from real world data would let us directly quantify wind-wave coupling and verify preexisting models. The turbulent fluctuations of the pressure and the velocity in the wind considerably exceed the wave-coherent fields by magnitude and make these fields difficult to observe and measure.
Here we propose linear (non-Wiener) and non-linear filters to extract the wave-coherent fields from point measurements of the sea surface elevation, and the velocity and pressure fluctuations in the wind above. The filters are introduced heuristically, but their formal justification and properties are also discussed. Both filters we present are optimal in least squares sense. We use the identified wave-coherent fields to address the issue of their scaling with height, obtain spectral information about the wind-wave coupling, as well as to estimate the energy exchange and waves growth. Comparisons with theory predictions are presented and discussed. The data analyzed in this work are from the Marine Boundary Layer Experiment, which took place 50 kilometers off the coast of California.