Diagnosis and tuning of observational error in a quasi-operational data assimilation setting

被引:87
作者
Chapnik, B
Desroziers, G
Rabier, F
Talagrand, O
机构
[1] CNRM, GMAP, OBS, F-31057 Toulouse, France
[2] Inst Pierre Simon Laplace, CNRS, Meteorol Dynam Lab, Paris, France
关键词
degrees of freedom for signal; error tuning; parameter estimation; variational assimilation;
D O I
10.1256/qj.04.102
中图分类号
P4 [大气科学(气象学)];
学科分类号
0706 ; 070601 ;
摘要
Desroziers and Ivanov proposed a method to tune error variances used for data assimilation. The implementation of this algorithm implies the computation of the trace of certain matrices which are not explicitly known. A method proposed by Girard, allowing an approximate estimation of the traces Without explicit knowledge of the matrices, was then used. This paper proposes a new implementation of the Desroziers and Ivanov algorithm, including a new computation scheme for the required traces. This method is compared to Girard's in two aspects: its use in the implementation of the tuning algorithm, and the computation of a quantification of the observation impacts on the analysis known as Degrees of Freedom for Signal. Those results are illustrated by studies utilizing the French data assimilation/numerical weather-predict ion system ARPEGE. The impact of a first quasi-operational tuning of variances on forecasts is shown and discussed.
引用
收藏
页码:543 / 565
页数:23
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