## Abstract

An analysis of coherent measurements of winds and waves from data collected during the Office of Naval Research (ONR) High-Resolution air–sea interaction (HiRes) program, from the *Floating Instrument Platform* (R/P *FLIP*), off the coast of northern California in June 2010 is presented. A suite of wind and wave measuring systems was deployed to resolve the modulation of the marine atmospheric boundary layer by waves. Spectral analysis of the data provided the wave-induced components of the wind velocity for various wind–wave conditions. The power spectral density, the amplitude, and the phase (relative to the waves) of these wave-induced components are computed and bin averaged over spectral wave age *c*/*U*(*z*) or *c*/*u*_{*}, where *c* is the linear phase speed of the waves, *U*(*z*) is the mean wind speed measured at the height *z* of the anemometer, and *u*_{*} is the friction velocity in the air. Results are qualitatively consistent with the critical layer theory of Miles. Across the critical height *z _{c}*, defined such that

*U*(

*z*) =

_{c}*c*, the wave-induced vertical and horizontal velocities change significantly in both amplitude and phase. The measured wave-induced momentum flux shows that, for growing waves, less than 10% of the momentum flux at

*z*≈ 10 m is supported by waves longer than approximately 15 m. For older sea states, these waves are able to generate upward wave-induced momentum flux opposed to the overall downward momentum flux. The measured amplitude of this upward wave-induced momentum flux was up to 20% of the value of the total wind stress when

*C*/

_{p}*u*

_{*}> 60, where

*C*is the phase speed at the peak of the wave spectrum.

_{p}*Corresponding author address:*W. Kendall Melville, Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0213. E-mail: kmelville@ucsd.edu