Estimating Wind Speed and Direction Using Wave Spectra

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. Plain Language Summary Coastal marine weather conditions are continuously monitored by meteorological buoys and satellites to inform the public, authorities, and emergency services. However, observations of wind and waves from meteorological buoys and satellites are strongly restricted by either their spatial or temporal resolution. Wave buoys, which measure waves only and not wind, can be more compact, which makes them easier to deploy, relatively low cost, and therefore much better suited to deploy in larger numbers. Here, we explore whether we can exploit the coupling of short surface waves to the near‐surface wind to quantitatively estimate surface wind properties based on wave measurements. We use an extensive data set of collocated wind and wave measurements to show that measurements of short wind waves can indeed provide a useful estimate of wind speed and direction. We also show that the accuracy of the estimates are considerably improved when the size of the buoy is reduced. The fidelity of surface wind estimates based on wave measurements is comparable to estimates based on remote sensing satellite data. This suggests that n