Accurate radiative transfer modeling in the coupled atmosphere-sea system is increasing in importance for the development of advanced remote-sensing applications. Aiming to quantify the uncertainties in the modeling of coastal water radiometric quantities, we performed a closure experiment to intercompare theoretical and experimental data as a function of wavelength λ and water depth z. Specifically, the study focused on above-water downward irradiance E d(λ, 0+) and in-water spectral profiles of upward nadir radiance L u(λ, z), upward irradiance E u(λ, z), downward irradiance E d(λ, z), the E u(λ, z)/L u(λ, z) ratio (the nadir Q factor), and the E u(λ, z)/E d(λ, z) ratio (the irradiance reflectance). The theoretical data were produced with the finite-element method radiative transfer code ingesting in situ atmospheric and marine inherent optical properties. The experimental data were taken from a comprehensive coastal shallow-water data set collected in the northern Adriatic Sea. Under various measurement conditions, differences between theoretical and experimental data for the above-water E d(λ, 0+) and subsurface E d(λ, 0-) as well as for the in-water profiles of the nadir Q factor were generally less than 15%. In contrast, the in-water profiles of L u(λ, z), E d(λ, z), E u(λ, z) and of the irradiance reflectance exhibited larger differences [to approximately 60% for L u(λ, z) and E u(λ, z), 30% for E d(λ, z), and 50% for the irradiance reflectance]. These differences showed a high sensitivity to experimental uncertainties in a few input quantities used for the simulations: the seawater absorption coefficient; the hydrosol phase function backscattering probability; and, mainly for clear water, the bottom reflectance.
© 2003 Optical Society of AmericaFull Article | PDF Article