A posteriori validation applied to the 3D-Var ARPEGE and ALADIN data assimilations system
Une validation a-posteriori appliquée au système d'assimilation des données des modèles 3D-Var ARPEGE et ALADIN
Sadiki, W. ; Fischer, C.
Année de publication
2005
In this paper we present results from the application of a posteriori <br>diagnostics on existing data assimilation systems. The systems of <br>interest are the global data assimilation Arpège 3D-VAR of Météo-France,<br> and the limited-area 3D-VAR analysis of Aladin. First, we discuss how <br>the diagnostics can be ported from theory to practical applications, <br>using aggregates of analysis information over time. We then compare the <br>behaviour of the diagnostics in the two different data assimilation <br>systems, with a focus on the properties of the background and <br>observational error variances. Secondly, the a posteriori validation is <br>used for the off-line tuning of two scalar error parameters in the <br>Aladin 3D-VAR. The tuning provides error variances that better fit the <br>statistics of the innovation vector, without loss of quality in the <br>analyses. Finally, the link of this approach with ensemble-based <br>techniques is made. Especially, we propose to couple the a posteriori <br>diagnostics directly with the usual output of ensemble samples, which <br>could be done at no extra cost. If the results are then used to tune <br>error parameters, then an on-line adaptive assimilation system, based on<br> a posteriori considerations, is obtained.</div>
Accès à la notice sur le site du portail documentaire de Météo-France