Improved hyperspectral inversion of aquatic reflectance under non-uniform vertical mixing

Citation

Simis S, Hunter P, Matthews M, Spyrakos E, Tyler A & Vaiciute D (2022) Improved hyperspectral inversion of aquatic reflectance under non-uniform vertical mixing. Optics Express, 30 (6), pp. 9655-9673. https://doi.org/10.1364/oe.450374

Abstract
Estimating the concentration of water constituents by optical remote sensing assumes absorption and scattering processes to be uniform over the observation depth. Using hyperspectral reflectance, we present a method to direct the retrieval of the backscattering coefficient (bb(λ)) from reflectance (> 600 nm) towards wavebands where absorption by water dominates the reflectance curve. Two experiments demonstrate the impact of hyperspectral inversion in the selected band set. First, optical simulations show that the resulting distribution of bb(λ) is sensitive to particle mixing conditions, although a robust indicator of non-uniformity was not found for all scenarios of stratification. Second, in the absence of spectral backscattering profiles from in situ data sets, it is shown how substituting the median of bb(λ) into a near infra-red / red band ratio algorithm improved chlorophyll-a estimates (root mean square error 75.45 mg m−3 became 44.13 mg m−3). This approach also allows propagation of the uncertainty in bb estimates to water constituent concentrations.

Keywords
Atomic and Molecular Physics, and Optics

Journal
Optics Express: Volume 30, Issue 6

People

Dr Peter Hunter

SIEC/Forth-ERA Science Director, Scotland's International Environment Centre

Dr Evangelos Spyrakos

Associate Professor, Biological and Environmental Sciences

Professor Andrew Tyler

Scotland Hydro Nation Chair, Biological and Environmental Sciences