Etude de l'ajustement hydrostatique suite à un forçage diabatique dans un modèle pleinement élastique

The purpose of this research is to further our understanding of the hydrostatic adjustment process due to diabatic heating. This is achieved by the use of an atmospheric model based on Euler's non-hydrostatic, fully elastic set of equations resolved by the semi-Lagrangian, semi-implicit marching scheme. Such a model thus allows a tri-dimensional, numerical approach of a problem which could, until now, only be addressed within a simplified context (one-dimensional and analytical; bi-dimensional and numerical).The hydrostatic adjustment is the mechanism by which the atmosphere tends to reach a new hydrostatic balance when this one has been upset. This can be the case through a diabatic forcing, such as the sudden latent heat release during the formation of a thunderstorm cell. This is actually the kind of forcing we chose for this study. The problem of the hydrostatic adjustment is tackled through two different contexts: an idealized and a real case. Both are simulated by three different model's versions: fully compressible (PE), quasi-hydrostatic (QH) and quasi-anelastic (QA). These versions differ from each other only by the formulation of the diabatic heating terms.The idealized case makes use of a prescribed heating source. A high resolution, in time and space, allows to show (PE version) how the mass, pressure and energy redistribution process is accomplished by the elastic, Lamb and gravity disturbances. The QH version, which consists in a spreading of the heating over the whole column above the source, inhibits vertically propagating elastic perturbations. The QA version, which considers the omission of the diabatic term in the pressure prognostic equation, shows that only the gravity mode is maintained.The real case simulates a highly convective summer situation. The choice of a long time step brings out only the gravity mode; the hydrostatic adjustment by the fast modes (elastic and Lamb) is taking place quasi instantaneously. Thus this large-scale case doesn't exhibit significant differences between the PE, QH and QA versions