2° global configuration (ORCA2)

• 1979-2001 forced by ERA40 daily fluxes
• 2001-2007 forced by ECMWF operational analysis

• Earth's sphericity: local gravity directed towards the centre of the Earth
• Relatively shallow water: ocean depth small in relation to the Earth's radius
• Hydrostatic: equilibrium between the vertical pressure gradiant and the floatability
• Boussinesq values: variations in density are not taken into account apart from their contribution to floatability
• Incompressibility: the three-dimensional divergence of the velocity field is considered to be nil
• 1.5 order closure turbulence scheme
• Non-linear equation of state couples the two active trace indices (temperature and salinity)
• Linearised and filtered free surface
• diagnostic ice model (ice " IF ")

• Model state variables : temperature, salinity, zonal and meridian velocity, free surface elevation, vertical diffusivity coefficient
• Atmospheric forcing: zonal and meridional wind stress, penetrating heat flux, solar flux, non solar flux, salt flux, precipitation and runoff minus evaporation budget
• Diagnostic Variables : mixed layer depth (density diagnostics).

• Diffusion: laplacian isopycnal operator (2000 m2/s) + Gent & Mc Williams eddy-induced tracer transport and diffusion.
• Viscosity : bilaplacian horizontal operator (40 000 m2/s reduced to 2000 m2/s at the Equator)
• TKE (turbulent kinetic energy) vertical mixing model
• No slip lateral boundary friction condition
• Non linear bottom friction
• Z vertical coordinate

• Restoring towards the Levitus climatology (T,S) at the Gibraltar Strait exit, in the Gulf of Cadix. This restoring increases from 200 m to 400 m, then remains constant to the bottom. Another restoring towards the Levitus climatology at the Bab El Mandeb Strait, in the Gulf of Aden. This last one increases between 200 m and 400 metres, then remains constant to the bottom
• Restoring towards the Levitus climatology (T,S) all over the globe under the mixed layer with a 3-year restoring time scale (DEMETER-like restoring).

ORCA grid (Arakawa type C), 2° résolution refined in the tropics (1/2° résolution in méridian), in the Mediterranean and in the Red Sea. ORCA grid Arakawa type B for sea ice model. Number of points : 182 x 149.

Orca2 resolution (Km)

31 levels. From 10 m at the surface to 500 m at the bottom.

Flux formulation. The monthly climatological flow of the 120 main rivers is taken into account in the evaporation minus precipitation budget. Daily correction of the global surface fresh water budget. A parameterization of the penetrating heat flux is used.

ERA40 reanalysis (1979-2001) and ECMWF daily operational analysis (2001-2005) journalière. Zonal and meridional wind stress components, wind module, heat penetrating flux, solar flux, non solar flux, salt flux, evaporation minus precipitation minus runoff.

Monthly Levitus temperature and salinity from Levitus 98

Smith et Sandwell, 1997

• 550 MB of memory
• 8 CPU hours
• 10 Gigabytes of output (daily output).

PSY2G2 (without sea ice model)