Using satellite multi-angle polarization measurements to characterize atmospheric aerosol above Bohai Bay

Abstract

The paper analyzes data from the PARASOL optical multi-angle polarization radiometer over the waters of Bohai Bay under various atmospheric conditions and different seawater optical types. The study considered cases of clear atmosphere, haze, dust aerosol, and cloud coverage. The waters of Bohai Bay were categorized into areas heavily influenced by river inflows and relatively clear waters. By utilizing PARASOL data, the degree of polarization (DoP) values of optical radiation at scattering angles of about 90° between incident solar radiation and recorded radiation were determined. Appropriate scatterplots were created using measurements from the 490, 670, and 865 nm bands. Polarimetric pseudo-color maps were presented to classify various atmospheric states. The scatterplots successfully identified atmospheric dust, dust in clouds, haze, and water areas with high levels of suspended particles. The results obtained are consistent with the experience of using the Umov effect to study dust aerosol, which consists in the negative correlation between the maximum polarization of radiation and geometric albedo. The presence of suspended particles in water led to decrease in correlation coefficients between analyzed DoP at different wavelengths within the investigated sea area. The strong influence of river inflows on Bohai Bay in polarimetric data was observed only under clean atmospheric conditions.