The operational MyOcean global analysis and forecasting system (hereafter referred to as Mercator) consists of the Mercator Océan Nucleus for European Modelling of the Ocean (NEMO) global 1/4° configuration with a 1/12° nested model over the Atlantic and the Mediterranean (Lellouche et al., 2013). Mercator has 50 vertical levels with 1m resolution at the surface, 240m resolution at the bottom, and 22 levels within the upper 100m. The global model bathymetry is ETOPO2 in regions deeper than 300m and GEBCO8 in regions shallower than 200m with a linear interpolation in the 200m to 300m layer (Lellouche et al., 2013).
The assimilation system is the second generation of the Mercator Assimilation System (SAM2) which was built around a Singular Evolutive Extended Kalman (SSEK) filter analysis kernel introduced by Pham et al. (1998). The assimilated observations consist of along-track altimeter SSHA from AVISO, satellite SST from NCEP or NOAA, and temperature and in situ vertical profiles, including Argo. In addition to the quality control procedures performed at data assembly centers, the system performs quality control on the assimilated temperature and salinity vertical profiles to minimize the risk of erroneous observations being integrated in the model (Lellouche et al., 2013). An important difference of MyOcean with respect to more classical forecasting systems is that the analysis is performed in the middle of the 7-day assimilation cycle instead of at the end of the window to provide an estimate of the ocean centered in time (Lellouche et al., 2013).
Atmospheric forcing is from the European Centre for Medium-Range Weather Forecasts (ECMWF). Momentum and heal turbulent surface fluxes are computed from CORE bulk formulae (Large and Yeager, 2009). The system uses the LIM2_EVP ice model. The system does not include tides.
Mercator is run daily and provides 10 days of hourly surface current velocity forecasts and 10 days of daily mean full 3D currents.