Climate Dynamics

, Volume 40, Issue 3–4, pp 775–803 | Cite as

An assessment of oceanic variability for 1960–2010 from the GFDL ensemble coupled data assimilation

  • You-Soon ChangEmail author
  • Shaoqing Zhang
  • Anthony Rosati
  • Thomas L. Delworth
  • William F. Stern


The Geophysical Fluid Dynamics Laboratory has developed an ensemble coupled data assimilation (ECDA) system based on the fully coupled climate model, CM2.1, in order to provide reanalyzed coupled initial conditions that are balanced with the climate prediction model. Here, we conduct a comprehensive assessment for the oceanic variability from the latest version of the ECDA analyzed for 51 years, 1960–2010. Meridional oceanic heat transport, net ocean surface heat flux, wind stress, sea surface height, top 300 m heat content, tropical temperature, salinity and currents are compared with various in situ observations and reanalyses by employing similar configurations with the assessment of the NCEP’s climate forecast system reanalysis (Xue et al. in Clim Dyn 37(11):2511–2539, 2011). Results show that the ECDA agrees well with observations in both climatology and variability for 51 years. For the simulation of the Tropical Atlantic Ocean and global salinity variability, the ECDA shows a good performance compared to existing reanalyses. The ECDA also shows no significant drift in the deep ocean temperature and salinity. While systematic model biases are mostly corrected with the coupled data assimilation, some biases (e.g., strong trade winds, weak westerly winds and warm SST in the southern oceans, subsurface temperature and salinity biases along the equatorial western Pacific boundary, overestimating the mixed layer depth around the subpolar Atlantic and high-latitude southern oceans in the winter seasons) are not completely eliminated. Mean biases such as strong South Equatorial Current, weak Equatorial Under Current, and weak Atlantic overturning transport are generated during the assimilation procedure, but their variabilities are well simulated. In terms of climate variability, the ECDA provides good simulations of the dominant oceanic signals associated with El Nino and Southern Oscillation, Indian Ocean Dipole, Pacific Decadal Oscillation, and Atlantic Meridional Overturning Circulation during the whole analyzed period, 1960–2010.


Ensemble coupled data assimilation Reanalysis Assessment Oceanic variability 



We greatly appreciate research groups on OAFlux, ISCCP, ERA40, NODC, TAO, OSCAR, AVISO, EN3, and RAPID for providing their analysis based on observations. The availability of NCEP reanalysis, OISST, WOD09, Argo and GTSPP data also makes the ECDA system possible. We thank R. Msadek and X. Yang for their comments on the earlier version of this manuscript. Suggestions made by two anonymous reviewers were very constructive in the revision of this paper.


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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • You-Soon Chang
    • 1
    • 2
    Email author
  • Shaoqing Zhang
    • 1
  • Anthony Rosati
    • 1
  • Thomas L. Delworth
    • 1
  • William F. Stern
    • 1
  1. 1.Geophysical Fluid Dynamics LaboratoryPrincetonUSA
  2. 2.University Corporation for Atmospheric ResearchBoulderUSA

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