POSTER Session 3

THE EMERGENT FEATURES IN THE DISTRIBUTION OF LINEAR POLARIZATION FROM THE DIFFERENT LIGHT PATHS

In this work, images of the downwelling and upwelling spectral polarized radiance distributions captured by PixPol were compared with Monte Carlo model simulations of the coupled atmosphere-ocean system. As part of the optical closure assessment, the modeling used Mueller matrices for water column scattering derived from measurements made with the MASCOT instrument. There was good closure in the overall pattern of polarization between measurements and the model, especially for the downwelling radiances. However, the measured degree of linear polarization was systematically slightly lower in blue and green wavelengths. Neutral points (locations where the polarization vanishes) emerge where the polarization contribution from single scattering balances with that from higher order scattering events. Therefore, their locations are a useful metric in describing the polarized distribution of light and its formation under multiple scattering. The model could disassociate photon paths, and so illustrate how neutral point locations are altered by different components of the system. Modeling and measurements both supported the emergence of non-principal meridian neutral points in the downwelling skylight due light reflected off the sea surface. Additionally, the results indicate the conditions necessary for neutral points in the in-water upwelling radiance to occur off the principal meridian. Here, the diffuse skylight field plays an essential role, but their occurrence is also extremely sensitive to instrument self-shading. These patterns in the distribution of linear polarization can be used to help interpret polarized water-leaving radiance distributions now measured by the SPEXone and HARP2 polarimeters for the PACE mission and guide future closure experiments.

E. Riley Blocker, Science Systems and Applications Inc. (SSAI), and Ocean Ecology Laboratory, NASA Goddard Space Flight Center, USA, [email protected], https://orcid.org/0000-0003-3278-4527

John D. Hedley, Numerical Optics Ltd., USA, [email protected]

Michael Twardowski, Harbor Branch Oceanographic Institute, Florida Atlantic University, USA, [email protected]

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