LAUSR

Sea salt aerosols are mostly distributed over the oceans and they can significantly affect the atmospheric radiative transfer. This article investigated sea salt aerosol impact on the polarization state of radiance at the top of the atmosphere (TOA) through the use of sea salt particle models. Specifically, six models of sea salt aerosols, including a homogeneous sphere, two super-spheroids, and three inhomogeneous spheres with both spherical and nonspherical cores, were considered and their optical properties were computed using the Lorenz–Mie theory and the invariant imbedding T-matrix method. The polarized radiance at the TOA was simulated by using a vector adding–doubling radiative transfer model. It was demonstrated that the inhomogeneous sphere-modeled TOA polarized radiance had a minimum at the backscattering angles ranging from 170° to 175°, whereas such features disappear when a homogeneous sphere or nonspherical model is used. To prove this effect, the satellite marine aerosol vertical feature mask data from the Cloud Aerosol Light Detection and Ranging (Lidar) and Infrared Pathfinder Satellite Observations (CALIPSO) over global ocean areas were collocated with the measurements from Polarization and Anisotropy of Reflectance for Atmospheric Science Coupled with Observations from a Lidar (PARASOL). It was found that the PARASOL polarized radiance also had negative values at the backscattering angles ranging from 170° to 175°. Thus, the obvious negative polarized radiances at these backscattering angles could be indicative of inhomogeneous sea salt aerosols. Both homogeneous and inhomogeneous sea salt models related to ambient relative humidity (RH) should be considered for accurate radiative transfer simulations.