1/4° Atlantic and Mediterranean configuration (MNATL4)

Existing simulations

2000-2005 forced by oprational analysis ECMWF :


Sea surface height (m), 2004 average	Vitesse de la glace de mer (cm/s), March 2004 average	Sea ice concentration (% of surface), March 2004 average

Physics

Overview

NEMO (OPA9+LIM) (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)
Linearised and filtered free surface
Nested with LIM sea ice model

Output data

Model state variables : temperature, salinity, zonal and meridian velocity, free surface elevation and vertical diffusivity coefficient
Sea ice variables: thickness ice, ice production, ice concentration, ice temperature, ice/sea interface flux, zonal and meridional ice velocity
Atmospheric forcing: zonal and meridional wind stress, penetrating heat flux, solar flux, non solar flux, salt flux, snow flux, precipitation and runoff minus evaporation budget
Diagnostic variables: mixed layer depth (density diagnostic), mass transport by density class through sections, meridional heat transport.

Physical parameterizations

Diffusion: bilaplacian horizontal operator (300 m2/s1)
Viscosity : bilaplacian horizontal operator -1.5 E11 m2/s)
Energy and enstrophy conserving advection scheme
KE (turbulent kinetic energy) vertical mixing model
Partial slip lateral boundary friction condition
Non linear bottom friction
Partial step vertical coordinate

Restoring zones

A restoring zone towards climatological temperature and salinity is applied in the Gulf of Cadiz.

Geographical extension

North Atlantic from 20°S to 80°N and Mediteranean sea.

Resolution

Horizontal resolution

ORCA 1/4° all over the domain, from 3 to 10 km. Number of spot: 486 x 529

Vertical resoltion

Vertical resolution in MNATL4 (see black diamonds)

Ocean atmosphere interface

Bulk formulation (CLIO). The monthly climatological flow of the main rivers is taken into account in the evaporation minus precipitation budget (Dai and Trenberth, 2002). A parameterization of the penetrating heat flux is used.

Ocean boundary conditions

South boundary at 20°S and North boundary at 80°N: Buffer zone where temperature and salinity are relaxed towards Levitus climatology (relaxation coefficients are between 3 and 100 days).

Input data

Forcing

ECMWF (2000-2005) daily operational analysis. Zonal and meridional wind stress components, wind module, relative humidity, cloud coverage, rain, air temperature.

Climatology

Bathymetry

Bathymétrie (m) dans MNATL4.

Computing cost

For one year of simulation on IBM Power 4:

9 Gigabytes of memory
340 CPU hours
120 Gigabytes of output (daily output)

Operational

no scheduled