Spectral reflectance of whitecaps: Their contribution to water-leaving radiance

A radiometric system, deployed from a ship, is used to measure directly the influence of the presence of breaking waves (whitecaps) on the upwelling r adiance above the sea surface. Estimates of their remote sensing augmented spectral reflectance, i.e., the temporally averaged or spatially averaged i ncrease in the ocean's reflectance over and above the reflectance in the ab sence of breaking waves, are provided from measurements in the tropical Pac ific. The accuracy of these estimates is dependent on their ability to dete rmine radiometrically the background reflectance of the water. In the visib le the remote sensing augmented spectral reflectance of whitecaps measured in the open ocean was found to be essentially independent of wavelength and in the range 0.001-0.002 for wind speeds of 9-12 m s(-1). This is in reaso nably good agreement (within a factor of 2) with earlier predictions based on the statistical relationship between fractional coverage and wind speed and the estimated average reflectance of individual whitecaps. In the near infrared (860 nm) the remote sensing augmented spectral reflectance falls t o similar to 80% of its value in the visible.