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Estimating Oceanic Primary Productivity: an Evaluation of Ocean Color Algorithms and General Circulation Models

Vincent Sellitto Saba, Virginia Institute of Marine Science, vssaba@vims.edu (Presenting)
Marjorie A.M Friedrichs, Virginia Institute of Marine Science, marjy@vims.edu
Mary-Elena Carr, Columbia University, mcarr@ei.columbia.edu

Modeling oceanic primary productivity (PP) is crucial for biogeochemical studies, especially in order to better understand the carbon cycle on a global scale. We have expanded the PP Algorithm Round-Robin (PPARR) project into its fourth exercise by quantifying the skill of 35 models (including both ocean color algorithms and biogeochemical general circulation models) in reproducing in situ PP data from a wide variety of ecosystems across the globe. They included the Sargasso Sea [Bermuda Atlantic Time-Series (BATS)], Pelagic North Atlantic (NABE), Coastal North Atlantic (NEA), Mediterranean Sea, Arabian Sea, Black Sea, North Pacific Sub-Tropical Gyre [Hawaii Ocean Time-series (HOT)], Antarctic Polar Frontal Zone (APFZ), and the Ross Sea. To assess model skill, we calculated total root mean square difference (RMSD). We also used Target and Taylor diagrams, cumulative distribution functions and other statistical approaches to compare model performance in each region.

Preliminary results among nine regions showed that overall model skill was highest in the APFZ, NABE, and Arabian Sea while lowest in the Ross Sea and MED. High model skill in the APFZ was likely due to the very short time-series of measured PP data thus seasonal variability was not represented in the analysis. All models typically under-estimated PP in pelagic regions and over-estimated PP in coastal regions. In seven of nine regions, ocean color models outperformed general circulation models. Among ocean color models, PP was typically over-estimated at high surface chlorophyll concentrations and under-estimated at low concentrations. Among the two regions with a long time-series at a single station, ocean color models performed considerably better in HOT than in BATS. In two of six regions, in situ chlorophyll, as opposed to SeaWiFS, produced higher model skill. There was higher model skill at BATS when SeaWiFS chlorophyll was used as opposed to in situ.




NASA Carbon Cycle & Ecosystems Active Awards Represented by this Poster:

  • Award: NNX06AF72G and NNG06GA03G
    Start Date: 2005-10-01
     

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