ECMWF estimation of ocean state via OCEAN5 system

ECMWF estimates the state of the global ocean via the operational system OCEAN5. The OCEAN5 system is a global eddy-permitting ocean-sea ice ensemble (5 members) reanalysis-analysis system. It comprises a Behind-Real-Time (BRT) component, that was used for production of Ocean ReAnalysis System 5 (ORAS5) and provides an estimate of the historical ocean state from 1979 to present (with a few days delay); and a Real-Time (RT) component, that provides the latest ocean conditions for NWP applications. A backward extension of ORAS5 is also available from 1958 onwards, for ensemble 0 (OPA0). The OCEAN5 system replaced the OCEAN4 system and now provide ocean and sea-ice initial conditions for all ECMWF coupled forecasting systems.

Attention! The interpolated r1x1 degree data in both ORAS5 and ORAS5 backward extension are affected by a land-sea-mask issue during interpolation, and exhibit some anomalous points near coast/ocean bottom. By using the correct LSM, you can mask out all these anomalous points in r1x1 archived data as described in this Correction to ORA S5 r1x1 files manual. Data assimilated: reprocessed SST from HadISST2 + OSTIA operational; reprocessed sea-ice concentration from OSTIA + OSTIA operation; reprocessed in-situ profiles from EN4 with XBT/MBT correction (Gouretski and Reseghetti, 2010) + GTS operational; AVISO reprocessed DT2014 SLA + NRT, with revised MDT; Global mean sea-level changes are constrained using AVISO DT2014 L4 MSLA + NRT
Ensemble: 5 ensemble members (opa0-4, with opa0 as the control member without perturbation), generated using perturbed initial conditions (see Zuo et al., 2018) + observation and forcing perturbations (see Zuo et al., 2017).
Assimilation method: 3DVar-FGAT as in ORAP5 + ensemble-based a-priori bias correction scheme + stability check for bias correction + updated observation QC + revised parametrizations
Forcing and relaxation used: ERA-40 (before 1979), ERA-Interim (1979-2015), ECMWF NWP (2015-present), bulk formula + revised wave forcing
Disclamer: ORAS5 was produced with ECMWF NWP forcing (from January 2015 onwards) and GTS opertional observations (from June 2015 onwards), therefore can be affected by incidents associated to the real-time operations.
ECMWF contact: Hao Zuo (hao.zuo (at), Magdalena Balmaseda, Magdalena.Balmaseda (at)

References: Zuo, H., Balmaseda, M. A., Tietsche, S., Mogensen, K., and Mayer, M., The ECMWF operational ensemble reanalysis-analysis system for ocean and sea-ice: a description of the system and assessment, Ocean Sci. Discuss.,, in review, 2019.

Zuo, H., Balmaseda, M. A., de Boisseson, E., Hirahara, S., Chrust, M., and De Rosnay, P., A generic ensemble generation scheme for data assimilation and ocean analysis. ECMWF Tech Memo.,, 2017.

sea surface temperature (c), zonal current (m/s), salinity (psu), potential temperature (c), meridional current (m/s), wind stress along i-axis (n/m2), net upward water flux (kg/m2/s), sea surface height (m), ice thickness (m), ice velocity u (m/s), ice velocity v (m/s), ice concentration (fraction), depth of 20c isotherm (m), heat content column (j/m2), wind stress along j-axis (n/m2), mixed layer depth 0.01 (m), sea surface salinity (psu)
Zonal Global by 1.0 deg
Meridional Global by 1.0 deg
Temporal Jan 1979 to Dec 2018 by 1 month(s)
Extension: Jan 1958 to Dec 2018 (Meridional and Zonal Currents: Jan 1975 to Dec 2018) for OPA0
Static? no
Volume 196GB
Server public:
Acquired Apr 26, 2019 (March 2020)
APDRC contact