Abstract

Recent optical probes of clear ocean waters conducted by the Naval Ocean Research and Development Activity and others have indicated that the submarine light field of clear ocean waters at longer visible wavelengths (520 nm +) is comosed of both solar photons and photons ascribable to water Raman emission. The Raman scattering of shorter wavelength photons in the visible waveband shows up most strongly at the longer wavelengths where solar photons are heavily absorbed. The ability to predict the propagation and fate of solar photons requires a knowledge of the water Raman scattering process in ocean waters. We have combined results from a Monte Carlo simulation of light propagation in the sea incorporating water Raman scattering with data collected by NORDA in the Sargasso Sea to make quantitative estimates of the percentage of photons at any given point in the marine hydrosol that are due to water Raman emission. The required measurements are the apparent absorption coefficient of the hydrosol calculated from the measured irradiance field and the true Lambert-Beer absorption coefficient measured directly from the hydrosol. By this method the variability of water Raman emission at a given wavelength due to removal of photons by components other than molecular water can be accounted for. The average cosine parameters of the mean photon paths have also proved to be sensitive indicators of the interaction of water Raman photons and the various scattering components of the marine hydrosol.

© 1989 Optical Society of America