Dissertation/Thesis Abstract

Polarimetric light fields in the open ocean and coastal waters and retrieval of water parameters from polarimetric observations
by Ibrahim, Amir, Ph.D., The City College of New York, 2015, 209; 3681084
Abstract (Summary)

Remote sensing has relied mainly 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 including the polarimetric characteristics of the light in measurements provides more intrinsic information about scattering particles. To take advantage of this, we used vector radiative transfer (VRT) simulations and we analytically developed a relationship to retrieve the micro and macro-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 the water, from which the scattering coefficient is readily computed (b = c - a), for different bio-optical models of Case I and II waters. This relationship was parameterized for all possible viewing geometries, including sensor zenith/azimuth relative to the Sun's principal plane, and for varying Sun zenith angles. An inversion model was also developed for the retrieval of the microphysical properties of hydrosols, such as the bulk refractive index and the particle size distribution. This relationship was tested and validated against a dataset of in-situ measurements using a custom built underwater polarimeter and an in-water instrument package (WET Labs ac-s) that measure the absorption and the attenuation coefficients. These measurements confirmed the approach, with retrievals of attenuation coefficients showing a high coefficient of determination, over 93%, depending on the wavelength. The benthos effects on the underwater polarized light field in shallows waters was also examined and discussed. A Lambertian model of the benthic reflectance showed that different types of bottoms of the ocean floor have a depolarizing effect on the polarized light underwater. As a consequence, these results can facilitate detection of benthic materials, as well as aid future studies of camouflage by benthic biota. Thus to effectively hide underwater, animals must reflect light with the same polarization characteristics as the background benthic materials. The thesis also investigated and discussed polarization effects at the top of the atmosphere, in which the impacts of the types of aerosols and/or their optical thickness, can be significant on the retrieval algorithms developed.

Indexing (document details)
Advisor: Ahmed, Samir, Gilerson, Alexander
Commitee: Cao, Changyong, Chowdhary, Jacek, Gross, Barry, Moshary, Fred
School: The City College of New York
Department: Electrical Engineering
School Location: United States -- New York
Source: DAI-B 76/06(E), Dissertation Abstracts International
Subjects: Electrical engineering, Remote sensing
Keywords: Ocean color, Polarimetry, Polarization of light, Remote sensing
Publication Number: 3681084
ISBN: 9781321536256
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