The influence of waves in wind stress direction as from the analysis of buoy direct measurements.

A comprehensive analysis of direct wind stress estimation is performed from a field campaign measurements carried out in the Gulf of Mexico. Air-sea interaction spar buoys were deployed and operated at three locations in order to study ocean-atmosphere interactions under a variety of meteorological conditions. Variability of atmosphere and ocean conditions is a very important issue that provide us with the best analysis of the influence of wave direction in the relative direction of wind stress upon the mean wind direction. Results of relatively simple cases with only one wave system show a gradual direction change of wind stress very much associated with the relative wave direction with respect to wind, specially under low to moderate wind conditions. These type of conditions are always more frequent in the ocean generally. When the calculation of the wind stress is performed in a reference frame aligned with wave propagation direction, a clearer evidence of the wave coherent stress component is observed. Main results of this work are obtained in such a coordinate system aligned with the waves claiming the paramount importance of the wave-coherent stress. The effect of multiple wave systems in the wind stress is addressed taken considering special conditions when atmospheric fronts were present in the region. The ultimate goal is to provide a proper parametrization of the momentum transfer to be used in the next generation of numerical models.