North Atlantic configuration at 1/3° (MNATL3)

Existing Simulations

Simulations with climatological forcings :


Sea Surface barotropic current fonction (Sv), July mean	Sea Surface height (cm), July mean	Salinity (psu), section at 36°N, between 25W and 5W, July mean

Physics

Overview

OPA8.1 (Madec, Delecluse et al. 1998), The formulation is based on so-called 'primitive' equations. These equations are derived from Navier-Stokes equations in a stratified fluid with following approximations:

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)
Rigid lid approximation

Output data

Model state variables : temperature, salinity, zonal and meridian velocity, barotropic stream function and vertical diffusivity coefficient
Atmospheric forcing: zonal and meridional wind stress, penetrating heat flux, solar flux, retroaction term, precipitation and runoff minus evaporation budget, surface salinity restoring term
Diagnostic Variables : mixed layer depth (two density diagnostics), sea level rise, barotropic height, dynamic height, mass transport by density class through sections, meridional heat transport

Physical parameterization

Diffusion: laplacian isopycnal operator
Viscosity : bilaplacian horizontal operator
Energy and enstrophy conserving advection scheme
TKE (turbulent kinetic energy) vertical mixing model
Partial slip lateral boundary friction condition
Non linear bottom friction
Bottom boundary layer
Z vertical coordinate

Restoring zones

Restoring towards the Reynaud climatology (T,S) at the Gibraltar Strait exit, in the Gulf of Cadix. This restoring increases between 500 m and 1000 metres, then remains constant to the bottom (~30 days).

Geographical extension

North Atlantic 20°S à 70°N.

Resolution

Horizontal resolution

1/3° Mercator grid in Atlantic. Number of points : 358 x 361

Vertical resolution

MNATL vertical resolution (see green cross)

Ocean atmosphere interface

Flux formulation with retroaction between model temperature surface and atmosphere computed from Reynolds SST (40 W/m2) and equivalent restoring towards the climatologic surface salinity (Barnier, Siefridt et al. 1995). The monthly climatological runoff of 18 main rivers is taken into account in the evaporation minus precipitation budget. A parameterization of the penetrating solar flux is used.

Ocean boundary conditions

South boundary at 20°S and North boundary at 70°N: buffer zone where temperature and salinity are restored to Reynaud climatology (relaxation coefficients are between 3 and 100 days).

Imput data

Forcing

ERA40 (1988-2002) or daily operational analysis ECMWF (1998-2006). Zonal and meridional wind stress components, solar flux , total heat flux (solar + infrared + sensitive + latent), evaporation, precipitation.

Climatology

Reynaud

Bathymetry

Smith et Sandwell, 1997

Computing cost

For one year of simulation on IBM Power 4:

4 Gigabytes of memory
50 CPU hours
5 Gigabytes of output (daily output)

Operational

PSY1V1
PSY1V2
MERA-11 reanalysis