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Original Research Papers

A posteriori validation applied to the 3D-VAR Arpège and Aladin data assimilation systems

Authors:

Wafaa Sadiki ,

Direction de la Météorologie Nationale, Casablanca, MA
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Claude Fischer

Météo-France/CNRM/GMAP, 42 avenue Coriolis, 31057 Toulouse, FR
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Abstract

In this paper we present results from the application of a posteriori diagnostics on existing data assimilation systems. The systems of interest are the global data assimilation Arpège 3D-VAR of Météo-France, and the limited-area 3D-VAR analysis of Aladin. First, we discuss how the diagnostics can be ported from theory to practical applications, using aggregates of analysis information over time.We then compare the behaviour of the diagnostics in the two different data assimilation systems, with a focus on the properties of the background and observational error variances. Secondly, the a posteriori validation is used for the off-line tuning of two scalar error parameters in the Aladin 3D-VAR. The tuning provides error variances that better fit the statistics of the innovation vector, without loss of quality in the analyses. Finally, the link of this approach with ensemble-based techniques is made. Especially, we propose to couple the a posteriori diagnostics directly with the usual output of ensemble samples, which could be done at no extra cost. If the results are then used to tune error parameters, then an on-line adaptive assimilation system, based on a posteriori considerations, is obtained.

How to Cite: Sadiki, W. and Fischer, C., 2005. A posteriori validation applied to the 3D-VAR Arpège and Aladin data assimilation systems. Tellus A: Dynamic Meteorology and Oceanography, 57(1), pp.21–34. DOI: http://doi.org/10.3402/tellusa.v57i1.14606
  Published on 01 Jan 2005
 Accepted on 16 Jul 2004            Submitted on 13 Nov 2003

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