Optical propagation within a three-dimensional shadowed atmosphere–ocean field: application to large deployment structures

Estimation of optical shadowing effects that occur on in situ submerged radiance and irradiance measurements conducted in the proximity of a large and complex three-dimensional deployment structure is addressed by use of Monte Carlo simulations. We have applied backward Monte Carlo techniques and variance reduction schemes in three-dimensional radiative transfer computations of in-water light field perturbations by taking into account relevant geometric, environmental, and optical parameters that describe a realistic atmosphere-ocean system. Significant parameters, determined by a sensitivity analysis study, have then been systematically varied for the computation of an extensive set of correction factors, included in look-up tables designed for operational removal of tower-shading uncertainties, which typically induce an approximately 1-10% decrease in absolute radiometric data values near a specific oceanographic tower located in the northern Adriatic Sea. In principle, the proposed correction methodology can be transferred to other deployment systems, instrument casings, and measurement sites if a comprehensive description is provided for the system parameters and their variability.