Marine asymptotic daylight field: effects of inelastic processes

• DOI: 10.1364/ao.35.004194
• Publication Date: 2008-11-12T20:50:30Z
• Authors: Howard R. Gordon; Xin Xu
• Keywords: 13. Climate action; 0103 physical sciences; 14. Life underwater; 01 natural sciences

The governing equations are developed for the marine asymptotic daylight field in the scalar approximation, including the effects of inelastic processes-Raman scattering and chromophoric dissolved organic matter fluorescence. The governing equations are solved numerically and compared with Monte Carlo simulations. It is found that these solutions are the actual radiance distributions approached by the asymptotic field in the Monte Carlo simulations. Sample solutions are provided to show the sensitivity of the light field to the various parameters of the medium. For certain values of the parameters, inclusion of inelastic processes can drastically alter the radiance distribution, e.g., from a near-Dirac delta function in the absence of inelastic processes to a near-isotropic distribution in their presence. The results suggest that in a real ocean, the asymptotic (and near-asymptotic) radiance distribution will tend to become more uniform as the wavelength increases beyond ~500 nm. Finally, it is shown that even for depths far from the asymptotic regime, the radiance distribution of the inelastic component of the light field can be well approximated by the asymptotic theory developed here for inelastic processes. Two exact analytical solutions to the governing equations are also provided.