Effects of Raman scattering across the visible spectrum in clear ocean water: a Monte Carlo study.

Raman-scattering activity in clear ocean waters is documented for the visible spectrum from Monte Carlo simulations. The Raman-scattering activity has a significant effect on the upwelling irradiance value in air and on the submarine light field at the water surface across the visible spectrum. A reduction in Raman-scattering activity at 440 nm that is due to Fraunhofer lines at the Raman source wavelengths is also demonstrated. At wavelengths greater than 500 nm, Raman scattering makes a significant contribution to the in-water light field at depth.

Comparison of numerical models for computing underwater light fields.

Seven models for computing underwater radiances and irradiances by numerical solution of the radiative transfer equation are compared. The models are applied to the solution of several problems drawn from optical oceanography. The problems include highly absorbing and highly scattering waters, scattering by molecules and by particulates, stratified water, atmospheric effects, surface-wave effects, bottom effects, and Raman scattering. The models provide consistent output, with errors (resulting from Monte Carlo statistical fluctuations) in computed irradiances that are seldom larger, and are usually smaller, than the experimental errors made in measuring irradiances when using current oceanographic instrumentation. Computed radiances display somewhat larger errors.

Raman scattering in ocean optics: quantitative assessment of internal radiant emission.

Raman-scattering activity in clear ocean waters is further documented from Monte Carlo simulations and optical data that are collected in the Sargasso Sea. A method is proposed, based on the anomalous absorption coefficient for a nonconservative irradiance field, to assess the percentile composition of internal radiant emission for the irradiance field at any depth.

Lambert-Beer law in ocean waters: optical properties of water and of dissolved/suspended material, optical energy budgets.

The role of the Lambert-Beer law in ocean optics is critically examined. The Lambert-Beer law and the three-parameter model of the submarine light field are used to construct an optical energy budget for any hydrosol. It is further applied to the analytical exponential decay coefficient of the light field and used to estimate the optical properties and effects of the dissolved/suspended component in upper ocean layers. The concepts of the empirical exponential decay coefficient (diffuse attenuation coefficient) of the light field and a constant exponential decay coefficient for molecular water are analyzed quantitatively. A constant exponential decay coefficient for water is rejected. The analytical exponential decay coefficient is used to analyze optical gradients in ocean waters.

Optical modeling of clear ocean light fields: Raman scattering effects.

A Monte Carlo simulation (the NORDA optical model) and the Three-Parameter Model of the submarine light field are used to analyze the effect of water Raman emission at 520 nm in clear ocean waters. Reported optical anomalies for clear ocean waters at longer wavelengths (520 nm +) are explained by the effects of water Raman emission, and the simulation results are confirmed by Biowatt-NORDA observations made in the Sargasso Sea. A new optical parametrization for clear ocean water is proposed.