CERFACS Ocean Analysis Disclaimer

The ocean reanalysis produced by CERFACS for the ENSEMBLES Stream 2 integrations was built using a 3-dimensional variational assimilation system for the OPA/NEMO ocean circulation model (Weaver et al., 2005; Daget et al., 2008). The model has a resolution of 2° on average, with a latitudinal refinement in the tropics. The integrations, forced by ERA40 heat fluxes and corrected water fluxes, is strongly restored towards observed sea surface temperature, with a relaxation coefficient of 200 W/m**2/°C. From September 2002 onwards, when ERA40 terminates, ECMWF operational surface fluxes were used as forcing. Quality-controlled temperature and salinity profiles from the EN3 (Ingleby and Huddleston, 2007) oceanographic data base are assimilated every 10 days from January 1960 to December 2005. Note that, for the sake of consistency with the model formulation, the mean sea level (global averaged) is kept constant throughout the period. Eight additional integrations were produced by perturbing wind stress, surface temperature and surface water fluxes.

More information on the system can be found in Daget, Weaver and Balmaseda (ECMWF Tech Memo 562).

Daget, N., A. T. Weaver and M. A. Balmaseda, 2008. An ensemble three- dimensional variational data assimilation system for the global ocean: sensitivity to the observation- and background-error variance formulation. Quart. J. Roy. Meteor. Soc., submitted.

Ingleby, B. and M. Huddleston, 2007. Quality control of ocean temperature and salinity profiles - historical and real-time data. J. Mar. Sys., 65, 148–175.

Weaver A. T., C. Deltel, E. Machu, S. Ricci and N. Daget, 2005. A multivariate balance operator for variational ocean data assimilation. Quart. J. Roy. Meteor. Soc., 131, 3605–3625.