Uncertainty in the bidirectional reflectance model for oceanic waters

Abstract

We study the impacts of the bio-optical model variations on the angular distribution (𝑓/𝑄 factor) of the upwelling radiance field in ocean waters. An ocean water bio-optical model has been combined with a vector radiative transfer model to calculate the 𝑓/𝑄 factors systematically. The 𝑓/𝑄 factors are compared to those in [Appl. Opt. 41, 6289 (2002) [CrossRef] ] and the differences are found to be within ±10% for 81% of the total number of cases covering all wavelengths, chlorophyll a concentrations, and solar and viewing geometries. The differences are attributed to the choice of ocean water scattering function and scattering coefficient biases. In addition, we study the uncertainty of 𝑓/𝑄 factor due to three factors: (I) the absorption coefficient of the colored dissolved organic matter (CDOM), (II) the particle scattering coefficient, and (III) the ocean water depolarization. The impacts of ocean water depolarization on the 𝑓/𝑄 variation is found to be negligible. If we perturb the CDOM absorption coefficient by a factor ranging from 0.1 to 10, the 𝑓/𝑄 values vary within ±5% of the average behavior of ocean waters for 93% of the cases. If we perturb the scattering coefficients by a factor ranging from 0.5 to 2.0, the 𝑓/𝑄 variation is within ±5% for 81% of the cases studied. This work contributes to understanding the uncertainty of ocean color remote sensing.