Inherent optical properties-reflectance relationships revisited

Lo Prejato, Marilisa and McKee, David and Mitchell, Catherine (2020) Inherent optical properties-reflectance relationships revisited. Journal of Geophysical Research: Oceans, 125 (11). e2020JC016661. ISSN 0148-0227

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    Abstract

    Understanding the relationship between remote sensing reflectance, Rrs(λ) and the inherent optical properties (IOPs) of natural waters is potentially a key to improving our ability to determine biogeochemical constituents from radiometric measurements. These relationships are usually described as a function of absorption, a(λ), and backscattering, bb(λ), coefficients, with the literature providing various forms of equation operating on either bb(λ)/a(λ) or bb(λ)/[a(λ)+bb(λ)] to represent the impact of variations in light field geometries and changes in sea-water composition. The performance of several IOP-reflectance relationships is assessed using HydroLight radiative transfer simulations covering a broad range of Case 1 and Case 2 water conditions. While early versions of IOP-reflectance relationships assigned variability to associated proportionality factors (e.g., f/Q) or low-order polynomial functions, recent studies have demonstrated relationships between Rrs(λ) and bb(λ)/[a(λ)+bb(λ)] are wellcharacterized by nonlinear (high-order polynomial), monotonic functions. This study demonstrates that this approach is also valid for relationships operating on bb(λ)/a(λ) and that there is no intrinsic benefit to functions operating on bb(λ)/[a(λ)+bb(λ)] compared to bb(λ)/a(λ) for Case 2 waters, contrary to recent suggestions in the literature. In all cases it is necessary to carefully consider the performance of best fit relationships across the full range of variability of IOPs and Rrs(λ), with higher order polynomials required to enable equivalent performance across the range of natural variability. The analysis further demonstrates insignificant wavelength sensitivity across the visible region, limited sensitivity to changes in solar zenith angle and extends to relationships for below surface remote sensing reflectance, rrs(λ).

    ORCID iDs

    Lo Prejato, Marilisa, McKee, David ORCID logoORCID: https://orcid.org/0000-0001-8023-5923 and Mitchell, Catherine;
    • Item type:Article
      ID code:74660
      Dates:
      Date
      Event
      30 November 2020
      Published
      31 October 2020
      Published Online
      16 October 2020
      Accepted
      Keywords:marine optics, ocean colour, reflectance, remote sensing, inherent optical properties, Physics, Earth and Planetary Sciences (miscellaneous), Geophysics, Atmospheric Science, Space and Planetary Science
      Subjects:Science > Physics
      Department:Faculty of Science > Physics
      Strategic Research Themes > Ocean, Air and Space
      Depositing user: Pure Administrator
      Date deposited:20 Nov 2020 11:41
      Last modified:11 Jun 2021 00:42
      URI:https://strathprints.strath.ac.uk/id/eprint/74660
    CORE (COnnecting REpositories)