An Ocean-Colour Time Series for Use in Climate Studies: The Experience of the Ocean-Colour Climate Change Initiative (OC-CCI)

Type Article
Date 2019-10
Language English
Author(s) Sathyendranath Shubha1, Brewin Robert1, Brockmann Carsten2, Brotas Vanda3, Calton Ben4, Chuprin Andrei5, Cipollini Paolo6, Couto André3, Dingle James5, Doerffer Roland7, Donlon Craig8, Dowell Mark9, Farman Alex10, Grant Mike5, Groom Steve5, Horseman Andrew5, Jackson Thomas5, Krasemann Hajo7, Lavender Samantha10, Martinez-Vicente Victor5, Mazeran Constant11, Mélin Frédéric9, Moore Timothy12, Müller Dagmar2, 7, Regner Peter13, Roy Shovonlal14, Steele Chris5, Steinmetz François15, Swinton John10, Taberner Malcolm5, Thompson Adam5, Valente André3, Zühlke Marco2, Brando Vittorio16, Feng Hui12, Feldman Gene17, Franz Bryan17, Frouin Robert18, Gould Richard19, Hooker Stanford17, Kahru Mati18, Kratzer Susanne20, Mitchell B.18, Muller-Karger Frank21, Sosik Heidi22, Voss Kenneth23, Werdell Jeremy17, Platt Trevor5
Affiliation(s) 1 : National Centre for Earth Observation, Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK
2 : Brockmann Consult, Max-Planck-Straße 2, D-21502 Geesthacht, Germany
3 : Marine Environmental Sciences Centre, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
4 : PML Applications Ltd, Prospect Place, Plymouth PL1 3DH, UK
5 : Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK
6 : Telespazio Vega UK for ESA Climate Office, European Space Agency/ECSAT, Harwell Campus OX11 0FD, UK
7 : Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH, Max-Planck-Straße 1, D-21502 Geesthacht, Germany
8 : European Space Agency/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
9 : European Commission, Joint Research Centre (JRC), Via Enrico Fermi, 2749, I-21027 Ispra, Italy
10 : Telespazio VEGA UK Ltd., 350 Capability Green, Luton, Bedfordshire LU1 3LU, UK
11 : Solvo, 3 rue Saint-Antoine, 06600 Antibes, France
12 : 12 Ocean Process Analysis Laboratory, Morse Hall, University of New Hampshire, Durham, NH 03824, USA
13 : European Space Agency, ESRIN, Via Galileo Galilei, Casella Postale 64, 00044 Frascati (Roma), Italy
14 : Department of Geography and Environmental Sciences, University of Reading, Whiteknights, Reading RG6 6DW, UK
15 : HYGEOS, 165 Avenue de Bretagne, 59000 Lille, France
16 : CNR-ISMAR, Via Fosso del Cavaliere, 100, 00133 Roma, Italy
17 : NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
18 : Scripps Institution of Oceanography Mail Code 0218, University of California San Diego, La Jolla, CA 92039-0218, USA
19 : Naval Research Laboratory, Bldg. 1009, Code 7331, Stennis Space Center, MS 39529, USA
20 : Department of Ecology, Environment and Plant Sciences, University of Stockholm, 106 91 Stockholm, Sweden
21 : Institute for Marine Remote Sensing, College of Marine Science, University of South Florida, 140 7th Ave. South St, Petersburg, FL 33701, USA
22 : Biology Department, MS 32, Woods Hole Oceanographic Institution, Woods Hole, MA 02543-1049, USA
23 : Department of Physics, University of Miami, James L. Knight Physics Building, 1320 Campo Sano Dr., Coral Gables, FL 33124, USA
Source Sensors (1424-8220) (MDPI AG), 2019-10 , Vol. 19 , N. 19 , P. 4285 (31p.)
DOI 10.3390/s19194285
WOS© Times Cited 187
Note This article belongs to the Special Issue Remote Sensing of Ocean Colour: Theory and Applications
Keyword(s) ocean colour, water-leaving radiance, remote-sensing reflectance, phytoplankton, chlorophyll-a, inherent optical properties, Climate Change Initiative, optical water classes, Essential Climate Variable, uncertainty characterisation

Ocean colour is recognised as an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS); and spectrally-resolved water-leaving radiances (or remote-sensing reflectances) in the visible domain, and chlorophyll-a concentration are identified as required ECV products. Time series of the products at the global scale and at high spatial resolution, derived from ocean-colour data, are key to studying the dynamics of phytoplankton at seasonal and inter-annual scales; their role in marine biogeochemistry; the global carbon cycle; the modulation of how phytoplankton distribute solar-induced heat in the upper layers of the ocean; and the response of the marine ecosystem to climate variability and change. However, generating a long time series of these products from ocean-colour data is not a trivial task: algorithms that are best suited for climate studies have to be selected from a number that are available for atmospheric correction of the satellite signal and for retrieval of chlorophyll-a concentration; since satellites have a finite life span, data from multiple sensors have to be merged to create a single time series, and any uncorrected inter-sensor biases could introduce artefacts in the series, e.g., different sensors monitor radiances at different wavebands such that producing a consistent time series of reflectances is not straightforward. Another requirement is that the products have to be validated against in situ observations. Furthermore, the uncertainties in the products have to be quantified, ideally on a pixel-by-pixel basis, to facilitate applications and interpretations that are consistent with the quality of the data. This paper outlines an approach that was adopted for generating an ocean-colour time series for climate studies, using data from the MERIS (MEdium spectral Resolution Imaging Spectrometer) sensor of the European Space Agency; the SeaWiFS (Sea-viewing Wide-Field-of-view Sensor) and MODIS-Aqua (Moderate-resolution Imaging Spectroradiometer-Aqua) sensors from the National Aeronautics and Space Administration (USA); and VIIRS (Visible and Infrared Imaging Radiometer Suite) from the National Oceanic and Atmospheric Administration (USA). The time series now covers the period from late 1997 to end of 2018. To ensure that the products meet, as well as possible, the requirements of the user community, marine-ecosystem modellers, and remote-sensing scientists were consulted at the outset on their immediate and longer-term requirements as well as on their expectations of ocean-colour data for use in climate research. Taking the user requirements into account, a series of objective criteria were established, against which available algorithms for processing ocean-colour data were evaluated and ranked. The algorithms that performed best with respect to the climate user requirements were selected to process data from the satellite sensors. Remote-sensing reflectance data from MODIS-Aqua, MERIS, and VIIRS were band-shifted to match the wavebands of SeaWiFS. Overlapping data were used to correct for mean biases between sensors at every pixel. The remote-sensing reflectance data derived from the sensors were merged, and the selected in-water algorithm was applied to the merged data to generate maps of chlorophyll concentration, inherent optical properties at SeaWiFS wavelengths, and the diffuse attenuation coefficient at 490 nm. The merged products were validated against in situ observations. The uncertainties established on the basis of comparisons with in situ data were combined with an optical classification of the remote-sensing reflectance data using a fuzzy-logic approach, and were used to generate uncertainties (root mean square difference and bias) for each product at each pixel.

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Sathyendranath Shubha, Brewin Robert, Brockmann Carsten, Brotas Vanda, Calton Ben, Chuprin Andrei, Cipollini Paolo, Couto André, Dingle James, Doerffer Roland, Donlon Craig, Dowell Mark, Farman Alex, Grant Mike, Groom Steve, Horseman Andrew, Jackson Thomas, Krasemann Hajo, Lavender Samantha, Martinez-Vicente Victor, Mazeran Constant, Mélin Frédéric, Moore Timothy, Müller Dagmar, Regner Peter, Roy Shovonlal, Steele Chris, Steinmetz François, Swinton John, Taberner Malcolm, Thompson Adam, Valente André, Zühlke Marco, Brando Vittorio, Feng Hui, Feldman Gene, Franz Bryan, Frouin Robert, Gould Richard, Hooker Stanford, Kahru Mati, Kratzer Susanne, Mitchell B., Muller-Karger Frank, Sosik Heidi, Voss Kenneth, Werdell Jeremy, Platt Trevor (2019). An Ocean-Colour Time Series for Use in Climate Studies: The Experience of the Ocean-Colour Climate Change Initiative (OC-CCI). Sensors, 19(19), 4285 (31p.). Publisher's official version : , Open Access version :