Retrieval of vertical particle concentration profiles by optical remote sensing: a model study

Water-leaving radiance is subject to depth variability of the water constituents. The optical penetration depth is strongly dependent on the wavelength lambda, which allows to retrieve a non-uniform vertical profile of an optically-active constituent C-TSM(z) from remote-sensing reflectance R-rs(lambda,C-z). We define the apparent particle concentration C-TSM,C-app(lambda) of a vertically homogeneous water column whose R-rs(lambda,C-const) matches R-rs(lambda,C-z). Subsequently, we define a vertically-weighted averaged particle concentration C-TSM,C-ave(lambda), only dependent on C-TSM(z), and retrieve C-TSM(z) by minimizing the error between C-TSM,(app)(lambda) and C-TSM,C-ave(lambda) with genetic algorithms. We conclude that the retrieval is excellent if the sub-surface maximum lays close to the surface or the background concentration of C-TSM(z) is low. Conversely, results worsen for opposite conditions, due to insufficient signal strength from superimposed sub-surface maxima. (C)2014 Optical Society of America