Seasonal variability of upwelling radiance polarization over the Southern Baltic surface

Abstract. Polarization of light may be used to improve the remote colour sensing of sea water. This can be done in a number of ways, such as limiting of sun glints, obtaining information about atmospheric aerosol properties for atmospheric correction as well as improving the interpretation of the water-leaving signal results. However polarization signals at the top of atmosphere (ToA), that include the waterleaving signal, is strongly influenced by atmospheric molecular scattering and by direct sun and sky reflections from sea surface. For these reasons, it is necessary to better understand the factors that change the polarization of light in the atmosphere-ocean system. In this paper, the influence of seasonal variability of inherent optical properties (IOPs), wind speed and solar zenith angle (SZA) on the polarization of upwelling radiance over the sea surface is discussed. The presented results come from Monte Carlo simulations, which used averaged measurements of IOPs, collected for several years, as input data. The effects of simulations are presented in the form of polar plots of the upwelling radiance degree of polarization (DoP). The results indicate that regardless of the wavelength and type of water, the highest value of the above water DoP is strongly correlated with the absorptionto-attenuation ratio. The correlation is a power function and it depends on both the SZA and the wind speed. The correlation versatility for different wavelengths is very unusual in optics of the sea and is therefore worth emphasizing.