Importance of the polarization in the retrieval of oceanic constituents from the remote sensing reflectance

Abstract

The influence of marine particles on the polarized radiation exiting the ocean is studied, and the implications for the retrieval of particulate concentration from remotely sensed data are investigated. Simulations were carried out using a vector radiative transfer model. Open ocean and coastal waters conditions were examined separately. In phytoplankton dominated waters, the polarized reflectance is virtually insensitive to the variations in chlorophyll concentration when observing at the top of atmosphere. The polarization effects induced by phytoplankton cells are too weak compared to those induced by the air-water interface and the atmospheric particles (especially molecules) to significantly contribute to the polarized reflectance at this level of atmosphere. The use of the polarized information at short wavelengths is thus proposed to improve the retrieval of the spectral variation of the aerosol model in atmospheric correction algorithms. In coastal zones, the sensitivity of the polarized signal to the water content is much greater. The analysis demonstrates that the measurement of the polarized reflectance just above the sea surface may not be relevant to reduce the skylight reflection effects when the water mass is mainly dominated by highly refractive particles. It is shown that polarization measurements can be of great interest to separate the fraction of inorganic particles from biogenic cells. This study also highlights that an empirical-based inversion approach relying on the polarized reflectance measured in the green and at longer wavelengths could be efficient to retrieve the concentration of inorganic particles regardless of the phytoplankton content in coastal waters. Copyright 2007 by the American Geophysical Union.