ORAS4: ECMWF Ocean Reanalysis and derived ocean heat content

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ORAS4: ECMWF Ocean Reanalysis and derived ocean heat content
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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

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

Key Limitations

First 2 decades should be used with caution (large uncertainties)

Atlantic Meridional Circulation (AMOC) at 26N is underestimated

Large surface salinity errors

Please cite data sources, following the data providers' instructions
Suggested Data Citation
Dataset DOIs
Hosted Climate Index Files
Usage Restrictions

Expert Developer Guidance

Expert Developer Guidance

(a) Some visible events still non-validated, (e.i.: trends Mediterranean outflow waters). (b) Possibility of spurious signals.

11/16/12 3:05 AM, Magdalena Balmaseda (ECMWF)

Cite this page

Acknowledgement of any material taken from or knowledge gained from this page is appreciated:

National Center for Atmospheric Research Staff (Eds). Last modified "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 on 2023-12-04.

Citation of datasets is separate and should be done according to the data providers' instructions. If known to us, data citation instructions are given in the Data Access section, above.

Acknowledgement of the Climate Data Guide project is also appreciated:

Schneider, D. P., C. Deser, J. Fasullo, and K. E. Trenberth, 2013: Climate Data Guide Spurs Discovery and Understanding. Eos Trans. AGU, 94, 121–122, https://doi.org/10.1002/2013eo130001

Key Figures

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).

Other Information

Type of data product

Years of record
Data time period extended
Yes, data set is extended
Input Data

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

Vertical Levels:
Missing Data Flag
Ocean or Land
Ocean Only
Spatial Resolution

1x1, 42 levels

Model Resolution (reanalysis)
Data Assimilation Method
Model Vintage (reanalysis)