RADIATIVE PROPERTIES OF OCEANIC PARTICLES
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Date
2020-01-20
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Department
Physics
Program
Physics, Atmospheric
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Distribution Rights granted to UMBC by the author.
This item may be protected under Title 17 of the U.S. Copyright Law. It is made available by UMBC for non-commercial research and education. For permission to publish or reproduce, please see http://aok.lib.umbc.edu/specoll/repro.php or contact Special Collections at speccoll(at)umbc.edu
This item may be protected under Title 17 of the U.S. Copyright Law. It is made available by UMBC for non-commercial research and education. For permission to publish or reproduce, please see http://aok.lib.umbc.edu/specoll/repro.php or contact Special Collections at speccoll(at)umbc.edu
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Abstract
Global ocean color observations provide repeated synoptic coverage of spec- tral water leaving reflectance that are important for better understanding of ocean ecology and biogeochemistry, carbon cycle, and their impact on climate change. Ocean water gets its characteristic color from the absorption and scattering of light by dissolved and suspended water constituents. Historically, the oceanic particles were modeled as a sphere to simulate radiative transfer in water. This practice has shown deficiency in predicting numerous light scattering properties of marine par- ticles. Measurements show that the hydrosols can be of various sizes and shapes, suggesting that general non-spherical models should be considered for the study of single scattering properties of hydrosols. The first part of this work studies light scattering by non-spherical hydrosols modeled by randomly oriented spheroids. This study would lead to better understanding of light scattering properties of oceanic particles, more accurate radiative transfer predictions in ocean waters, as well as new remote sensing techniques of hydrosol compositions. Radiative transfer theory studies multiple scattering of light in turbid media,which often consists of two or more types of scattering particles. It is very important to properly calculate the light scattering properties of mixed medium. There are two schemes of mixing particles, internal and external mixing schemes, respectively. In the internal mixing scheme, light scattering properties are first calculated as weighted sum of the constituent properties and then input to the radiative transfer packages. In the external mixing scheme, light propagation is handled in a radia- tive transfer simulation in which the constituent particles preserve their scattering properties. In the second part, the equivalence of the internal and external mix- ing scheme has been established. The equivalence is significant for many radiative transfer applications involving the mixture of particles of different scattering and absorptive characteristics. The ocean polarized reflectance contains information about the constituents of the upper ocean euphotic zone, such as colored dissolved organic matter (CDOM), sediments, phytoplankton, and pollutants. In order to retrieve the information on these constituents, many remote sensing algorithms rely on radiative transfer models to interpret the spectral remote-sensing reflectance; however, this can be resource- prohibitive for operational use due to the extensive CPU time involved in radiative transfer solutions. In the third part, a fast Neural Network Reflectance Prediction Model (NNRPM) has been developed for polarized ocean reflectance with proper inputs of inherent optical properties of ocean waters. The incorporation of this model into the retrieval algorithm will make the retrieval process more efficient, and thus applicable for operational use with global satellite observations.