Abstract

By measuring the change of Fraunhofer lines in the solar spectrum in the water column, information on inelastic scattering process can be extracted. In this paper we model the effect of Raman scattering on Fraunhofer lines in ocean water. The change of Fraunhofer lines in ocean was calculated via Monte Carlo simulations. Six lines, 396.8, 422.7, 486.1, 518.4, 589.0, 656.3 nm, were investigated. Here η, defined as the ratio of the irradiance at the center of the Fraunhofer line to the background, was used to characterize the change of the Fraunhofer lines. It was found that η for 589.0 and 656.3 nm goes to 1 quickly as the depth increases, both for upwelling and downwelling irradiance. The 396.8- and 422.7-nm lines show a different behavior: η for the downwelling irradiance is almost constant while for the upwelling irradiance it is largest at the surface and decreases with depth. The 486.1- and 518.4-nm lines appear to be a dividing point between the shortwave and longwave range. At these wavelengths, η does not change with depth and is always larger in the upwelling irradiance than in the downwelling irradiance.

© 1991 Optical Society of America