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Global chlorophyll a concentrations of phytoplankton functional types with detailed uncertainty assessment using multi-sensor ocean color and sea surface temperature satellite products
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  • Hongyan Xi,
  • Svetlana Loza (Losa),
  • Antoine Mangin,
  • Philippe Garnesson,
  • Marine Bretagnon,
  • Julien Demaria,
  • Marinana A. Soppa,
  • Odile Hembise Fanton d'Andon,
  • Astrid Bracher
Hongyan Xi
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research

Corresponding Author:[email protected]

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Svetlana Loza (Losa)
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research
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Antoine Mangin
ACRI-ST
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Philippe Garnesson
ACRI-ST
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Marine Bretagnon
ACRI-ST
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Julien Demaria
ACRI-ST
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Marinana A. Soppa
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research
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Odile Hembise Fanton d'Andon
ACRI-ST
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Astrid Bracher
Alfred-Wegener-Institut für Polar und Meeresforschung,Universität Bremen,Universität Bremen
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Abstract

Firstly, we re-tune an algorithm based on empirical orthogonal functions (EOF) for globally retrieving the chlorophyll a concentration (Chl-a) of phytoplankton functional types (PFTs) from multi-sensor merged ocean color (OC) products. The re-tuned algorithm, namely EOF-SST hybrid algorithm, is improved by: (i) using 30% more matchups between the updated global in situ pigment database and satellite remote sensing reflectance (Rrs) products, and (ii) including sea surface temperature (SST) as an additional input parameter. In addition to the Chl-a of the six PFTs (diatoms, haptophytes, dinoflagellates, green algae, prokaryotes and Prochlorococcus), the fractions of prokaryotes and Prochlorococcus Chl-a to total Chl-a (TChl-a), are also retrieved by the EOF-SST hybrid algorithm. Matchup data are further separated for low and high temperature regimes based on different PFT dependences on SST, to establish the SST-separated hybrid algorithms which further shows improved performance as compared to the EOF-SST hybrid algorithm. The per-pixel uncertainty of the retrieved TChl-a and PFT products is estimated by taking into account the uncertainties from both input data and model parameters through Monte Carlo simulations and analytical error propagation. The uncertainty assessment provided within this study sets the ground to extend the long-term continuous satellite observations of global PFT products by transferring the algorithm and its method to determine uncertainties to similar OC products until today. Satellite PFT uncertainty is also essential to evaluate and improve coupled ecosystem-ocean models which simulate PFTs, and furthermore can be used to directly improve these models via data assimilation.