ORAS4: ECMWF Ocean Reanalysis and derived ocean heat content
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
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)
Key Figures
Ocean basin meridional overturning circulation (source ECMWF).
ORSA4 SST anomaly Sept, 2012 (source ECMWF).
ORSA4 potential temperature anomaly longitude vs depth cross section Sept, 2012 (source ECMWF).
ORSA4 equatorial SST anomalies (source ECMWF).
ORSA4 western Pacific SST anomalies (source ECMWF).
Other Information
3D-Var: assimilation window is 10 days: temperature & salinity profiles, along-track sea-level anomalies, sea-level trends
1x1, 42 levels
- Balmaseda, M. A., Mogensen, K. and Weaver, A. T. (2013), Evaluation of the ECMWF ocean reanalysis system ORAS4. Q.J.R. Meteorol. Soc., 139: 1132–1161. doi: 10.1002/qj.2063
- Balmaseda, M. A., K. E. Trenberth, and E. Källén (2013), Distinctive climate signals in reanalysis of global ocean heat content, Geophys. Res. Lett., 40, 1754–1759, doi:10.1002/grl.50382.
- Balmaseda, M.A. et al (2008): The ECMWF Ocean Analysis System: ORA-S3