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| Titel |
Technical Note: Spectral representation of spatial correlations in variational assimilation with grid point models and application to the Belgian Assimilation System for Chemical Observations (BASCOE) |
| VerfasserIn |
Q. Errera, R. Ménard |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 21 ; Nr. 12, no. 21 (2012-11-01), S.10015-10031 |
| Datensatznummer |
250011549
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| Publikation (Nr.) |
 copernicus.org/acp-12-10015-2012.pdf |
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| Zusammenfassung |
| The formulation of the background error covariances represented in the
spectral space is discussed in the context of univariate assimilation relying
on a grid point model, leaving out all the aspects of balances between the
different control variables needed in meteorological assimilation. The
spectral transform operations are discussed in the case of a spherical
harmonics basis and we stress that there is no need for an inverse spectral
transform and of a Gaussian grid. The analysis increments are thus produced
directly on the model grid. The practice of producing analysis increments on
a horizontal Gaussian grid and then interpolating to an equally spaced grid is
also shown to produce a degradation of the analysis. The method discussed in
this paper allows the implementation of separable and non-separable spatial
correlations. The separable formulation has been implemented in the Belgian
Assimilation System for Chemical ObsErvations (BASCOE) and its impact on the
assimilation of O3 observed by the Michelson Interferometer for Passive
Atmospheric Sounding (MIPAS) is shown. To promote the use of this method by
other non-meteorological variational systems and in particular chemistry, the
Fortran code developed is made available to the community. |
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