An Eddy-Diffusivity Mass-Flux Parameterization for Modeling Oceanic Convection
Hervé
Giordani
CNRM/CNRS, UMR-3589, Météo-France
Poster
A new one-dimensional parameterization of the vertical mixing has been
developed for ocean general circulation models (OGCMs) in order to properly
represent the diffusive and convective processes in an unified approach.
Our approach is inspired from atmospheric parameterizations of shallow
convection which assumes that in the convective boundary layer, the
subgrid-scale fluxes result from two different mixing scales : small eddies
which are represented by an eddy-diffusivity contribution, and large eddies
associated with thermals which are represented by a mass-flux contribution.
The local (small eddies) and non-local (large eddies) contributions are unified
into an Eddy-Diffusivity-Mass-Flux (EDMF) parameterization which treats
simultaneously the whole vertical mixing.
EDMF is implemented and tested into the community ocean model NEMO.
We will show that the deepening of dense water in 1D analytic cases,
sucessfully reproduced in LES simulations, is significantly better captured
with EDMF than with standard diffusion parameterizations because of a better
representation of the non-local entrainment fluxes which are counter-gradient
in the thermocline.
A preliminary application of EDMF in the tropics will be presented with a focus
on PIRATA moorings.
developed for ocean general circulation models (OGCMs) in order to properly
represent the diffusive and convective processes in an unified approach.
Our approach is inspired from atmospheric parameterizations of shallow
convection which assumes that in the convective boundary layer, the
subgrid-scale fluxes result from two different mixing scales : small eddies
which are represented by an eddy-diffusivity contribution, and large eddies
associated with thermals which are represented by a mass-flux contribution.
The local (small eddies) and non-local (large eddies) contributions are unified
into an Eddy-Diffusivity-Mass-Flux (EDMF) parameterization which treats
simultaneously the whole vertical mixing.
EDMF is implemented and tested into the community ocean model NEMO.
We will show that the deepening of dense water in 1D analytic cases,
sucessfully reproduced in LES simulations, is significantly better captured
with EDMF than with standard diffusion parameterizations because of a better
representation of the non-local entrainment fluxes which are counter-gradient
in the thermocline.
A preliminary application of EDMF in the tropics will be presented with a focus
on PIRATA moorings.
Poster PDF