\documentstyle[preprint,eqsecnum,aps,prb]{revtex}

\begin{document}



\title{High order numerical scheme for higly stratified geophysical flows}
\author{S. Arnoux-Chiavassa, P. Angot, I. Danaila,
 P. Frauni\'e}

\address{$^1$Laboratoire de Sondages Electromagn\'etiques  de  l'Environnement
Terrestre,\\ UPRESA 6017  CNRS, Universit\'e de Toulon et du Var, BP 132,
  83957 La Garde Cedex, France
$^2$IRPHE, 12 Av. G. Leclerc, 13003 Marseille, France}
\baselineskip 15 pt
\maketitle
\narrowtext
\vskip 2cm
Higly stratified flows occur both in ocean and atmosphere due to temperature and
concentration gradients.

Analysis and stability of density fronts is presented for freshwater discharge
in the ocean (river plumes) and stable thermal sheets in the low atmosphere.

 Spatio-temporal complex mechanisms of exchanges
are investigated for  highly stratified  and mixing
situations, from numerical experiments involving  high order discretization.
2D vertical profiles of concentrations and temperature have
been compared to measurements. Depending
on boundary conditions, they exhibit weak to large vertical diffusion patterns
leading to a challenging case for modelization. An overview of several years
experience is given, involving TVD type numerical schemes for density fronts and
Large Eddy Simulation of vertical mixing.


\vskip 2cm
\acknowledgements

This research was supported by the french Programe National d'Oc\'eanographie
C\^oti\`ere and EC Mast III Program FANS (Contract MAS3-CT95-0037).
\end{document}