Küstenforschung

Publications

Lefering, Ina; Utschig, Christian; McKee, David (2017): Uncertainty budgets for liquid waveguide CDOM absorption measurements. Applied Optics. 56. 6357. doi:10.1364/AO.56.006357

Abstract:

Long path length liquid waveguide capillary cell (LWCC) systems using simple spectrometers to determine the spectral absorption by colored dissolved organic matter (CDOM) have previously been shown to have better measurement sensitivity compared to high-end spectrophotometers using 10 cm cuvettes. Information on the magnitude of measurement uncertainties for LWCC systems, however, has remained scarce. Cross-comparison of three different LWCC systems with three different path lengths (50, 100, and 250 cm) and two different cladding materials enabled quantification of measurement precision and accuracy, revealing strong wavelength dependency in both parameters. Stable pumping of the sample through the capillary cell was found to improve measurement precision over measurements made with the sample kept stationary. Results from the 50 and 100 cm LWCC systems, with higher refractive index cladding, showed systematic artifacts including small but unphysical negative offsets and high-frequency spectral perturbations due to limited performance of the salinity correction. In comparison, the newer 250 cm LWCC with lower refractive index cladding returned small positive offsets that may be physically correct. After null correction of measurements at 700 nm, overall agreement of CDOM absorption data at 440 nm was found to be within 5% root mean square percentage error.

 

Hiroyuki Tan, Tomohiko Oishi, Akihiko Tanaka, Roland Doerffer, and Yasuhiro Tan (2017): Chlorophyll-a specific volume scattering function of phytoplankton. Opt. Express 25, A564-A573, DOI: 10.1364/OE.25.00A564

Abstract:

Chlorophyll-A specific light volume scattering functions (VSFs) by cultured phytoplankton in visible spectrum range is presented. Chlorophyll-A specific VSFs were determined based on the linear least squares method using a measured VSFs with different chlorophyll-A concentrations. We found obvious variability of it in terms of spectral and angular shapes of VSF between cultures. It was also presented that chlorophyll-A specific scattering significantly affected on spectral variation of the remote sensing reflectance, depending on spectral shape of b. This result is useful for developing an advance algorithm of ocean color remote sensing and for deep understanding of light in the sea.

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