Application of Landsat imagery for the investigation of wave breaking

An algorithm for retrieving the fraction of the sea surface covered by whitecaps (W) from Landsat-8 satellite optical reflectance measurements in the near-infrared channel is described. The distribution of W derived from approximately 100 Landsat-8 scenes was compared with quasi-synchronous scatterometer measurements of wind speed (u10), which allowed us to obtain the W(u10) relation for large whitecaps from high-resolution satellite optical measurements. Further, we demonstrate the impact of various phenomena, includinginternal waves, river plumes, bottom topography, atmospheric stability, ocean fronts, and mesoscale currents on whitecap coverage and its spatial variation in different areas of the ocean. These data are analysed using theoretical models, suggesting that whitecap coverage is a proxy of wave energy dissipation and reflects disturbances in the wind-wave energy balance caused by wave-current interactions and variable wind forcing due to changes in atmospheric stratification over ocean temperature fronts and the movement of wind-waves by surface currents relative to the atmospheric boundary layer.