Estimation of chromophoric dissolved organic matter and non-algal particulate absorption coefficients of seawater in the ultraviolet by extrapolation from the visible spectral region

• DOI: 10.1364/oe.486354
• Publication Date: 2023-04-27T16:00:27Z
• Authors: Matthew D. Kehrli; Dariusz Stramski; Rick A. Reynolds; Ishan D. Joshi
• Keywords: Spectral slope; Ultraviolet; Visible spectrum; Ocean color

Extending the capabilities of optical remote sensing and inverse algorithms, which have been commonly focused on visible (VIS) range electromagnetic spectrum, to derive properties seawater in ultraviolet (UV) is important advancing understanding various optical, biological, photochemical processes ocean. In particular, existing remote-sensing reflectance models that total spectral absorption coefficient seawater, a(λ), partitioning partition a(λ) into component coefficients phytoplankton, aph(λ), non-algal (depigmented) particles, ad(λ), chromophoric dissolved organic matter (CDOM), ag(λ), are restricted VIS range. We assembled a quality-controlled development dataset hyperspectral measurements ag(λ) (N = 1294) ad(λ) 409) spanning wide values across ocean basins, evaluated several extrapolation methods extend adg(λ) ≡ + near-UV region by examining different sections as basis for extrapolation, functions, sampling intervals input data VIS. Our analysis determined optimal method estimate at wavelengths (350 400 nm) relies an exponential from 400-450 nm The initial obtained difference between extrapolated estimates ag(λ). Additional correction functions based differences measured were defined obtain improved final then sum ad(λ). model provides very good agreement when blue available 1 or 5 intervals. There negligible bias modeled all three median absolute percent (MdAPD) small, e.g., < 5.2% 10.5% with dataset. Assessment independent concurrent 149) yielded similar findings only slight reduction performance MdAPD remaining below 6.7% 11% These results promising integration operating