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| Titel |
Using adjoint sensitivity as a local structure function in variational data assimilation |
| VerfasserIn |
G. Hello, F. Bouttier |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 8, no. 6 ; Nr. 8, no. 6, S.347-355 |
| Datensatznummer |
250005881
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| Publikation (Nr.) |
 copernicus.org/npg-8-347-2001.pdf |
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| Zusammenfassung |
| One approach
recently proposed in order to improve the forecast of weather events, such
as cyclogenesis, is to increase the number of observations in areas
depending on the flow configuration. These areas are obtained using, for
example, the sensitivity to initial conditions of a selected predicted
cyclone. An alternative or complementary way is proposed here. The idea is
to employ such an adjoint sensitivity field as a local structure function
within variational data assimilation, 3D-Var in this instance. Away from
the sensitive area, observation increments project on the initial fields
with the usual climatological (or weakly flow-dependent, in the case of
4D-Var) structure functions. Within the sensitive area, the gradient
fields are projected using all the available data in the zone,
conventional or extra, if any. The formulation of the technique is given
and the approach is further explained by using a simple 1D scheme. The
technique is implemented in the ARPEGE/IFS code and applied to 11 FASTEX
(Fronts and Atlantic Storm-Track Experiment) cyclone cases, together with
the targeted observations performed at the time of the campaign. The new
approach is shown to allow for the desired stronger impact of the
available observations and to systematically improve the forecasts of the
FASTEX cyclones, unlike the standard 3D-Var. |
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