Underway sampling of marine inherent optical properties on the Tara Oceans expedition as a novel resource for ocean color satellite data product validation

© J.Ghiglione/CNRS/Tara Méditerranée

Tara Oceans

P. Jeremy Werdell (a,∗), Christopher W. Proctor (a,b), Emmanuel Boss (c), Thomas Leeuw (c), Mustapha Ouhssain (d,e) 

a. NASA Goddard Space Flight Center, Mail Code 616.2, Greenbelt, MD 20771, USA
b. Science Systems and Applications, Inc., 10210 Greenbelt Road, Suite 600, Lanham, MD 20706, USA
c. School of Marine Sciences, University of Maine, 458 Aubert Hall, Orono, ME 04401, USA
d. UMS 829 – Observatoire Océanologique – Centre National de la Recherche Scientifique,
Villefranche-sur-Mer, France
e. Universite Pierre et Marie Curie, Paris O6, Paris, France

Captured’ecran 2015-01-13a17.00.14

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Developing and validating data records from operational ocean color satellite instruments requires substantial volumes of high quality in situ data. In the absence of broad, institutionally supported field programs, organizations such as the NASA Ocean Biology Processing Group seek opportunistic datasets for use in their operational satellite calibration and validation activities. The publicly available, global biogeochemical dataset collected as part of the two and a half year Tara Oceans expedition provides one such opportunity. We showed how the inline measurements of absorption and attenuation coefficients collected onboard the R/V Tara can be used to evaluate near-surface estimates of chlorophyll-a, spectral particulate backscattering coefficients, particulate organic carbon, and particle size classes derived from the NASA Moderate Resolution Imaging Spectroradiometer onboard Aqua (MODISA). The predominant strength of such flow-through measurements is their sampling rate—the 375 days of measurements resulted in 165 viable MODISA-to-in situ match-ups, compared to 13 from discrete water sampling. While the need to apply bio-optical models to estimate biogeochemical quantities of interest from spectroscopy remains a weakness, we demonstrated how discrete  samples can be used in combination with flow-through measurements to create data records of sufficient quality to conduct first order evaluations of satellite-derived data products. Given an emerging agency desire to rapidly evaluate new satellite missions, our results have significant implications on how calibration and validation teams for these missions will be constructed.