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A Semianalytical Ocean Color Inversion Algorithm with Explicit Water Column Depth and Substrate Reflectance ParameterizationA semianalytical ocean color inversion algorithm was developed for improving retrievals of inherent optical properties (IOPs) in optically shallow waters. In clear, geometrically shallow waters, light reflected off the seafloor can contribute to the water-leaving radiance signal. This can have a confounding effect on ocean color algorithms developed for optically deep waters, leading to an overestimation of IOPs. The algorithm described here, the Shallow Water Inversion Model (SWIM), uses pre-existing knowledge of bathymetry and benthic substrate brightness to account for optically shallow effects. SWIM was incorporated into the NASA Ocean Biology Processing Group's L2GEN code and tested in waters of the Great Barrier Reef, Australia, using the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua time series (2002-2013). SWIM-derived values of the total non-water absorption coefficient at 443 nm, at(443), the particulate backscattering coefficient at 443 nm, bbp(443), and the diffuse attenuation coefficient at 488 nm, Kd(488), were compared with values derived using the Generalized Inherent Optical Properties algorithm (GIOP) and the Quasi-Analytical Algorithm (QAA). The results indicated that in clear, optically shallow waters SWIM-derived values of at(443), bbp(443), and Kd(443) were realistically lower than values derived using GIOP and QAA, in agreement with radiative transfer modeling. This signified that the benthic reflectance correction was performing as expected. However, in more optically complex waters, SWIM had difficulty converging to a solution, a likely consequence of internal IOP parameterizations. Whilst a comprehensive study of the SWIM algorithm's behavior was conducted, further work is needed to validate the algorithm using in situ data.
Document ID
20150022925
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Mckinna, Lachlan I. W. (Curtin Univ. of Technology Perth, Australia)
Werdell, P. Jeremy (NASA Goddard Space Flight Center Greenbelt, MD United States)
Fearns, Peter R. C. (Curtin Univ. of Technology Perth, Australia)
Weeks, Scarla J. (Queensland Univ. Brisbane, Australia)
Reichstetter, Martina (Queensland Univ. Brisbane, Australia)
Franz, Bryan A. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Shea, Donald M. (Science Applications International Corp. Greenbelt, MD, United States)
Feldman, Gene C. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
December 11, 2015
Publication Date
March 19, 2015
Publication Information
Publication: Journal of Geophysical Research: Oceans
Volume: 120
Issue: 3
Subject Category
Oceanography
Report/Patent Number
GSFC-E-DAA-TN23423
Funding Number(s)
CONTRACT_GRANT: NNG14HZ03C
Distribution Limits
Public
Copyright
Other
Keywords
Great Barrier Reef
Shallow water
Ocean Color