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ORAS4: ECMWF Ocean Reanalysis and derived ocean heat content

Climate Data Guide Image: ORAS4

ECMWF's current ocean reanalysis uses a sophisticated data assimilation methodology which includes a model bias correction. The ocean model used is forced by atmospheric daily surface fluxes, relaxed to SST and bias corrected.

The Balmaseda et al (QJRMS 2013) reference provides excellent peer reviewed documentation and evaluation.

Key Strengths:

  • Improved high quality data assimilation method and model
  • Improved surface forcing and quality control in-situ observations (XBT corrected, Argo blacklists...)
  • Retrospective use of Argo information via bias correction

Key Limitations:

  • First 2 decades should be used with caution (large uncertainties)
  • Atlantic Meridional Circulation (AMOC) at 26N is underestimated
  • Large surface salinity errors

Years of Record

1958/01 to 2013/04
temporal metadataID:

Formats

Timestep

Monthly

Data Time Period Extended?

yes, data set is extended

Domain

Global

Spatial Resolution

1x1, 42 levels

Ocean or Land

Ocean Only

Vertical Levels

Multiple levels

Input Data

3D-Var: assimilation window is 10 days: temperature & salinity profiles, along-track sea-level anomalies, sea-level trends

Earth system components and main variables

Ocean, Ocean Heat Content, Salinity, Sea Level, potential temperature, u, v current components

Key Figures

Click the thumbnails to view larger sizes

Thumbnails

Captions
Climate Data Guide Image: ORAS4 Ocean basin meridional overturning circulation (source ECMWF).
Climate Data Guide Image: ORAS4 ORSA4 SST anomaly Sept, 2012 (source ECMWF).
Climate Data Guide Image: ORAS4 ORSA4 potential temperature anomaly longitude vs depth cross section Sept, 2012 (source ECMWF).
Climate Data Guide Image: ORAS4 ORSA4 equatorial SST anomalies (source ECMWF).
Climate Data Guide Image: ORAS4 ORSA4 western Pacific SST anomalies (source ECMWF).

Cite this page

National Center for Atmospheric Research Staff (Eds). Last modified 13 Oct 2016. "The Climate Data Guide: ORAS4: ECMWF Ocean Reanalysis and derived ocean heat content." Retrieved from https://climatedataguide.ucar.edu/climate-data/oras4-ecmwf-ocean-reanalysis-and-derived-ocean-heat-content.

Acknowledgement of any material taken from this page is appreciated. On behalf of experts who have contributed data, advice, and/or figures, please cite their work as well.