Albedo of a water surface, spectral variation, effects of atmospheric transmittance, sun angle and wind speed

Abstract

Some properties of sea surface albedo have been investigated. (1) With aircraft data of upward and downward hemispheric irradiances in three broad bands of the solar spectrum we have investigated albedo as a function of transmittance (variations in windspeed and solar altitude were small). Transmittance measures the depletion of the solar radiation on its path through the atmosphere. For short solar wavelengths, 0.28–;0.53 μm, surface albedo shows little dependence on transmittance, while for longer solar wavelengths, 0.53–2.8 μm, albedo increases with decreasing transmittance. This behavior results from the observation that the short wavelengths are mostly diffuse for all degrees of cloudiness, whereas longer wavelengths become more diffuse with increasing cloudiness. (2) With measurements from broadband pyranometers on a mast over Lake Washington (Seattle, Washington) and from ships in the North Atlantic and the Tropical Atlantic during summer we have investigated the variation of albedo with solar altitude and transmittance. Our results are in general agreement with those of Payne (1972), but some deviations are indicated at high solar altitudes with low transmittances and for solar altitudes below 20°. The effects of wind speed on normalized albedo measured in the Joint Air‐Sea Interaction (JASIN) experiment agree with previous findings of Payne (1972) and Simpson and Paulson (1979).