Radiative transfer model for quality control of above-water hyperspectral downwelling irradiance measurements

Titelangaben

Moradi, Masoud ; Arabi, Behnaz ; Hommersom, Annelies ; van der Molen, Johan ; Samimi, Cyrus:
Radiative transfer model for quality control of above-water hyperspectral downwelling irradiance measurements.
In: Proceedings of SPIE. Bd. 12728 (2023) . - 127280C.
ISSN 0277-786X
DOI: https://doi.org/10.1117/12.2684363

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Abstract

Above-water spectral measurements are a critical component of ocean remote sensing and provide essential information for validating and improving remote sensing algorithms for water quality analysis. The downwelling irradiance (Es) is an essential component of above-water spectral measurements and it is particularly important for water constituent concentration, sea surface temperature, and atmospheric correction algorithms. The atmosphere particles scatter and absorb the direct and diffusive components of the downwelling irradiance, creating a complex and distorted spectrum. We analyzed 6 years of the above-water hyperspectral measurements collected every 15 minutes at the Royal Netherlands Institute for Sea Research (NIOZ) Jetty Station (JNS) installed in the Marsdiep tidal inlet of the Dutch Wadden Sea. The minimum level of solar irradiance and spectral shape of Es(λ) were simulated using Radiative Transfer (RT) to identify optimal Es spectra that could be favorable for remote sensing applications. The RT models were adjusted for the study area using in-situ bio-optical measurements. The spectrum of Es(λ) at the 3-optical depths were simulated to identify the minimum level of Es(λ). The red-shifted spectrum of Es(λ), caused by intense atmospheric scattering and the reddish hue of dusk or dawn radiations, was identified by Support Vector Machine applied to the simulated Es(λ) components. The results indicated that the maximum spectral value of Es(λ)max <= 25 mW m-2 nm-1 identifies the minimum level of above-water solar irradiance, and the ratios of Es(480)/Es(680) ≤ 1 mW m-2 nm-1 and Es(λ)max/Es(865) ≤ 1.25 mW m-2 nm-1 show the red-shifted spectra.