310
identical to the Gaussian grid of the atmospheric model (2.8 0 for the T42
model). At low latitudes the meridional spacing is gradually decreased
down to 0.5 0 at the equator. The reason to this is the requirement to
resolve equatorial waves, required to reproduce EI Nino phenomena realistically. Vertically, 11 interior layers and special mixed surface layer are
used. The model for the interior ocean uses the primitive equation in the
flux form of the conservation laws for momentum, mass, heat and salt at
isopycnal layers. These quantities are the prognostic variables together
with sea level height. Horizontal mixing of momentum is a function of the
local Rossby deformation radius, while horizontal diffusion of temperature
and salinity depends on the deformation of the flow. Vertical mixing follows
the concept of entrainment and detrainment for which budgets of turbulence and mean potential energy are being solved. A standard convective
adjustment scheme is employed which instantaneously removes vertical instabilities. The model for the interior ocean is coupled to a mixed layer
model, since the isopycnal coordinates break down near the surface when
strong turbulence is present. A special mixed layer model calculates fluxes
in and out of the uppermost isopycnal layer according to the budget for
turbulent kinetic and mean potential energy. Wind stirring, surface buoyancy due to heat and fresh water fluxes, sub-surface stability and flow shear
affect these calculations. The sea-ice model calculates the thickness and
concentration of ice and its momentum. The amount of snow on ice is also
calculated. A viscous-plastic rheology is used to parameterize the stress
tensor, while the thicknesses of ice and snow and the concentration of ice
are computed from respective continuity equations. Further parameterization relates the heat fluxes to changes in ice and snow thickness as well as to
lead size and to changes in salinity due to brine rejection. The conversion
of snow to ice and the surpression of snow is included in a parametric form.
The thermodynamic part consists of a prognostic computation of the temperature profile, taking into account the heat capacity and conductivity of
the slab and the net surface flux.
4.3
The coupling
Prior to the coupling the oceanic model has been integrated for about
1000 years by prescribing a combination of observed variables and simulated fluxes (with the atmospheric model). The dynamical components
such as wind stress and friction velocity have been derived from the atmo-
identical to the Gaussian grid of the atmospheric model (2.8 0 for the T42
model). At low latitudes the meridional spacing is gradually decreased
down to 0.5 0 at the equator. The reason to this is the requirement to
resolve equatorial waves, required to reproduce EI Nino phenomena realistically. Vertically, 11 interior layers and special mixed surface layer are
used. The model for the interior ocean uses the primitive equation in the
flux form of the conservation laws for momentum, mass, heat and salt at
isopycnal layers. These quantities are the prognostic variables together
with sea level height. Horizontal mixing of momentum is a function of the
local Rossby deformation radius, while horizontal diffusion of temperature
and salinity depends on the deformation of the flow. Vertical mixing follows
the concept of entrainment and detrainment for which budgets of turbulence and mean potential energy are being solved. A standard convective
adjustment scheme is employed which instantaneously removes vertical instabilities. The model for the interior ocean is coupled to a mixed layer
model, since the isopycnal coordinates break down near the surface when
strong turbulence is present. A special mixed layer model calculates fluxes
in and out of the uppermost isopycnal layer according to the budget for
turbulent kinetic and mean potential energy. Wind stirring, surface buoyancy due to heat and fresh water fluxes, sub-surface stability and flow shear
affect these calculations. The sea-ice model calculates the thickness and
concentration of ice and its momentum. The amount of snow on ice is also
calculated. A viscous-plastic rheology is used to parameterize the stress
tensor, while the thicknesses of ice and snow and the concentration of ice
are computed from respective continuity equations. Further parameterization relates the heat fluxes to changes in ice and snow thickness as well as to
lead size and to changes in salinity due to brine rejection. The conversion
of snow to ice and the surpression of snow is included in a parametric form.
The thermodynamic part consists of a prognostic computation of the temperature profile, taking into account the heat capacity and conductivity of
the slab and the net surface flux.
4.3
The coupling
Prior to the coupling the oceanic model has been integrated for about
1000 years by prescribing a combination of observed variables and simulated fluxes (with the atmospheric model). The dynamical components
such as wind stress and friction velocity have been derived from the atmo-