Modeling hyperspectral normalized water-leaving radiance in a dynamic coastal ecosystem

Bausell, J.; Kudela, Raphael M.

doi:10.1364/oe.426246

Cited by 4 publications

(2 citation statements)

References 23 publications

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“…14% (Table 2). Fluorescence in green wavelengths was dominated by 𝑓 DOM and these results are consistent with the findings of other studies [5,8,12]. Tzortziou et al ( 2006) [5] showed that inclusion of 𝑓 DOM improved the closure in green by 2-5% in the Chesapeake Bay.…”

Section: Optical Closure In Absorbing Waters: Significance Of Inelast...supporting

confidence: 89%

Optical closure in highly absorptive coastal waters: significance of inelastic scattering processes

Mukherjee¹,

Hedley²,

Fichot³

et al. 2023

Preprint

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In hydrological optics, "optical closure" means consistency between the apparent optical properties (AOPs) determined from radiometric measurements and those derived from radiative transfer modelling based on concurrently measured Inherent optical properties (IOPs) and boundary conditions (sea and sky states). Good optical closure not only provides confidence in the data quality but also informs on the adequacy of the radiative transfer parameterization. Achieving optical closure in highly absorptive coastal waters is challenging due to the low signal-to-noise ratio of radiometric measurements and uncertainties in the measurements of IOPs, namely the spectral absorption and backscattering coefficients. Here, we present an optical closure assessment using a comprehensive set of in situ IOPs acquired in highly absorptive coastal waters optically dominated by chromophoric dissolved organic matter (CDOM). The spectral remote sensing reflectance, Rrs(λ), was modeled using the software HydroLight (HL) with measured IOPs and observed boundary conditions. Corresponding in-water Rrs(λ) was derived from radiometric measurements made with a Compact Optical Profiling System (C-OPS; Biospherical). The assessment revealed that the inclusion of inelastic scattering processes in the model, specifically Sun-induced CDOM Fluorescence (fDOM) and Sun-Induced Chlorophyll Fluorescence (SICF) from Chlorophyll-a ([chl]), significantly improved the optical closure and led to good agreement between measured and modeled Rrs (i.e., for 440 ≤ λ ≤ 710 nm with no inelastic processes: R2=0.90, slope=0.64; with inelastic processes: R2=0.96, slope=0.90). The analysis also indicated that f_DOM and SICF contributed a substantial fraction of the green-red wavelength Rrs in these waters. Specifically, fDOM contributed ~18% of the modeled Rrs in the green region and SICF accounted for ~20% of the modeled Rrs in the red region. Overall, this study points out the importance of accounting for fDOM in remote sensing applications in CDOM-dominated waters.

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Section: Optical Closure In Absorbing Waters: Significance Of Inelast...supporting

confidence: 89%

Optical closure in highly absorptive coastal waters: significance of inelastic scattering processes

Mukherjee¹,

Hedley²,

Fichot³

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…Nonetheless, the launch of PACE and SBG and the lack of readily available validation-quality hyperspectral instrumentation that can collect data at relevant spatial and temporal scales for inland and coastal waters is problematic. One potential solution is to combine high-fidelity multiwavelength point measurements with spectrometers [35] or to rely on numerical models to recreate full spectral data [76,77]. A third approach would be to rely on a variety of sensors with varying performance characteristics deployed as a sensor web [32,78,79].…”

Section: Discussionmentioning

confidence: 99%

Expanded Signal to Noise Ratio Estimates for Validating Next-Generation Satellite Sensors in Oceanic, Coastal, and Inland Waters

Kudela,

Hooker,

Guild

et al. 2024

Remote Sensing

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The launch of the NASA Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) and the Surface Biology and Geology (SBG) satellite sensors will provide increased spectral resolution compared to existing platforms. These new sensors will require robust calibration and validation datasets, but existing field-based instrumentation is limited in its availability and potential for geographic coverage, particularly for coastal and inland waters, where optical complexity is substantially greater than in the open ocean. The minimum signal-to-noise ratio (SNR) is an important metric for assessing the reliability of derived biogeochemical products and their subsequent use as proxies, such as for biomass, in aquatic systems. The SNR can provide insight into whether legacy sensors can be used for algorithm development as well as calibration and validation activities for next-generation platforms. We extend our previous evaluation of SNR and associated uncertainties for representative coastal and inland targets to include the imaging sensors PRISM and AVIRIS-NG, the airborne-deployed C-AIR radiometers, and the shipboard HydroRad and HyperSAS radiometers, which were not included in the original analysis. Nearly all the assessed hyperspectral sensors fail to meet proposed criteria for SNR or uncertainty in remote sensing reflectance (Rrs) for some part of the spectrum, with the most common failures (>20% uncertainty) below 400 nm, but all the sensors were below the proposed 17.5% uncertainty for derived chlorophyll-a. Instrument suites for both in-water and airborne platforms that are capable of exceeding all the proposed thresholds for SNR and Rrs uncertainty are commercially available. Thus, there is a straightforward path to obtaining calibration and validation data for current and next-generation sensors, but the availability of suitable high spectral resolution sensors is limited.

show abstract

Optical closure in highly absorptive coastal waters: significance of inelastic scattering processes

Mukherjee,

Hedley,

Fichot

et al. 2023

Opt. Express

View full text Add to dashboard Cite

In hydrological optics, “optical closure” means consistency between the apparent optical properties (AOPs) determined from radiometric measurements and those derived from radiative transfer modelling based on concurrently measured inherent optical properties (IOPs) and boundary conditions (sea and sky states). Good optical closure not only provides confidence in the data quality but also informs on the adequacy of the radiative transfer parameterization. Achieving optical closure in highly absorptive coastal waters is challenging due to the low signal-to-noise ratio of radiometric measurements and uncertainties in the measurements of IOPs, namely the spectral absorption and backscattering coefficients. Here, we present an optical closure assessment using a comprehensive set of in situ IOPs acquired in highly absorptive coastal waters optically dominated by chromophoric dissolved organic matter (CDOM). The spectral remote sensing reflectance, Rrs(λ), was modeled using the software HydroLight (HL) with measured IOPs and observed boundary conditions. Corresponding in-water in situ Rrs(λ) was derived from radiometric measurements made with a Compact Optical Profiling System (C-OPS; Biospherical). The assessment revealed that the inclusion of inelastic scattering processes in the model, specifically sun-induced CDOM fluorescence (fDOM) and sun-induced chlorophyll fluorescence (SICF) from Chlorophyll-a ([chl]), significantly improved the optical closure and led to good agreement between measured and modeled Rrs (i.e., for 440 ≤ λ ≤ 710 nm with no inelastic processes: R2=0.90, slope=0.64; with inelastic processes: R2=0.96, slope=0.90). The analysis also indicated that fDOM and SICF contributed a substantial fraction of the green-red wavelength Rrs in these waters. Specifically, fDOM contributed ∼18% of the modeled Rrs in the green region and SICF accounted for ∼20% of the modeled Rrs in the red region. Overall, this study points out the importance of accounting for fDOM in remote sensing applications in CDOM-dominated waters.

show abstract

Modeling hyperspectral normalized water-leaving radiance in a dynamic coastal ecosystem

Cited by 4 publications

References 23 publications

Optical closure in highly absorptive coastal waters: significance of inelastic scattering processes

Optical closure in highly absorptive coastal waters: significance of inelastic scattering processes

Expanded Signal to Noise Ratio Estimates for Validating Next-Generation Satellite Sensors in Oceanic, Coastal, and Inland Waters

Optical closure in highly absorptive coastal waters: significance of inelastic scattering processes

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