Retrieval of macro- and micro-physical properties of oceanic hydrosols from polarimetric observations

REMOTE SENSING OF ENVIRONMENT

卷:186

Article

Ibrahim, Amir^1,2,3  Gilerson, Alexander¹  Chowdhary, Jacek^4,5  Ahmed, Samir¹ 

[1] CUNY City Coll, Dept Elect Engn, Opt Remote Sensing Lab, New York, NY 10031 USA

[2] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA

[3] Univ Space Res Assoc, Columbia, MD 21044 USA

[4] Columbia Univ, Dept Appl Phys & Appl Math, New York, NY 10025 USA

[5] NASA, Goddard Inst Space Studies, New York, NY 10025 USA

关键词: Remote sensing;    Polarization;    Hydrosol;    Ocean color;    Case-I waters;    Case II waters;    Bio-optics;    Chlorophyll a;    CDOM;    Plankton;    Minerals;    Scattering;    Vector radiative transfer modeling;    Aerosol;    Cloud;    Ocean ecosystem;    PACE;   

DOI  :  10.1016/j.rse.2016.09.004

来源: Elsevier

【 摘 要 】

Remote sensing has mainly relied on measurements of scalar radiance and its spectral and angular features to retrieve micro- and macro-physical properties of aerosols/hydrosols. However, it is recognized that measurements that include the polarimetric characteristics of light provide more intrinsic information about particulate scattering. To take advantage of this, we used vector radiative transfer (VRT) simulations and developed an analytical relationship to retrieve the macro and micro-physical properties of the oceanic hydrosols. Specifically, we investigated the relationship between the observed degree of linear polarization (DoLP) and the ratio of attenuation to-absorption coefficients (c/a) in water, from which the scattering coefficient can be readily computed (b = c - a), after retrieving a. This relationship was parameterized for various scattering geometries, including sensor zenith/azimuth angles relative to the Sun's principal plane, and for varying Sun zenith angles. An inversion method was also developed for the retrieval of the microphysical properties of hydrosols, such as the bulk refractive index and the particle size distribution. The DoLP vs c/a relationship was tested and validated against in-situ measurements of underwater light polarization obtained by a custom-built polarimeter and measurements of the coefficients a and c, obtained using an in-water WET Labs ac-s instrument package. These measurements confirmed the validity of the approach, with retrievals of attenuation coefficients showing a high coefficient of determination depending on the wavelength. We also performed a sensitivity analysis of the DoLP at the Top of Atmosphere (TOA) over coastal waters showing the possibility of polarimetric remote sensing application for ocean color. (C) 2016 Elsevier Inc. All rights reserved.

【 授权许可】

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