Increasing efforts are devoted by the Ocean Color Radiometry community to explore the polarization features of the underwater light field in order to enhance possibilities for retrieving inherent optical properties (IOPs) of coastal waters. New instrumentations and data inversion algorithms are being developed to take into account the supplementary information contained in polarization data. However, estimating the Stokes vector components of the polarized water radiance from above water measurements is a challenging task, mainly because of their small magnitude and the strong contamination by the polarized sky light reflected from the sea surface. In this study, above-water measurements are used to assess the feasibility of such retrievals and their utility for retrieving IOPs.
The Long Island Sound Coastal Observational platform (LISCO) near Northport, NY, was established in October 2009 to support satellite data validation. In June 2010, three customized hyperspectral HyperSAS systems (HyperSAS-POL) were added to LISCO platform enabling polarization measurements. A data processing algorithm, which includes vector radiative transfer computations, was developed and used to remove the polarization signal due to sky light reflected from the sea surface (sky glint) and derive the underwater polarization field. The spectral shape of the retrieved underwater degree of polarization was then evaluated against theoretical radiative transfer computations and in situ underwater measurements. The results confirmed the validity of the polarization measurements by the LISCO site, thus validating a continuous time series starting from the beginning of June 2010 to the present which can be used for retrievals of IOPs from polarization measurements.