This paper was written by J. J. Voermans, P. B. Smit, T. T. Janssen, and A. V. Babanin.
Compact wave buoys are increasingly used to provide monitoring of coastal and oceanic conditions by measuring surface waves in real time. Due to their relatively compact size, they are generally not suited to measure wind directly. However, since the wave field is intrinsically coupled to the wind field, wave measurements can serve as a proxy observation of ocean surface winds. In this study, we use spectral wave observations to estimate wind speed and direction based on the assumption of a universal 𝓯^-4 shape of the wave energy spectrum in the equilibrium range and the presence of a logarithmic wind speed profile above the ocean surface. The wind speed and direction were estimated between 2014 and 2017 at more than a 100 coastal sites with colocated wave and wind observations. Estimates of wind speed and direction based on wave measurements have a root-mean-square error of 2 m/s for wind speeds between 3 and 12 m/s (and a relative error of 17% for wind speeds between 10 and 20 m/s) and up to 20° for wind speeds between 10 and 20 m/s. The accuracy of proxy measurements of wind depends on fetch, wave steepness, wave age, directional alignment between wind and dominant waves, and temporal variability of the wind. Further, we show that estimates of wind speed and direction improve considerably as the size of the buoy is reduced.
