Retrieval of marine inorganic particle concentrations in turbid waters using polarization signals

Abstract

ABSTRACT The polarization properties of water-leaving radiance (L w) contains rich information about hydrosols, which has great potential to improve the retrieval accuracy of oceanic constituents. However, current ocean colour inversion algorithms are only based on the water-leaving radiation intensity, and the polarization properties have been ignored. Here, based on the radiative transfer simulations, the possibility of retrieving suspended particulate matter in turbid waters based on the polarization properties was investigated. The results showed that the degree of polarization (DOP) of the upward radiation just beneath the water surface has significant angular and spectral variations with respect to the observational geometries, inorganic particle concentrations, solar zenith angles and aerosol optical thicknesses (AOTs). The directional variations in DOP along with viewing zenith angles are typically characterized by a double peak feature with a maximum of 0.5 in the principal plane. In addition, the DOP in the visible bands is highly sensitive to inorganic particle concentrations. The DOP gradually decreases from 412 nm to 555 nm and increases with wavelengths beyond 555 nm, particularly for wavelengths larger than 620 nm. An empirical relationship between the DOP at 670 nm and the inorganic particle concentration was established for different viewing geometries with determination coefficient (R 2) up to 0.9996. Overall, our simulation results indicate that the polarization property of underwater upward radiance has great potential for suspended particulate matter retrieval in coastal waters.