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| Titel |
Ensemble perturbation smoother for optimizing tidal boundary conditions by assimilation of High-Frequency radar surface currents – application to the German Bight |
| VerfasserIn |
A. Barth, A. Alvera-Azcárate, K.-W. Gurgel, J. Staneva, A. Port, J.-M. Beckers, E. V. Stanev |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 6, no. 1 ; Nr. 6, no. 1 (2010-02-04), S.161-178 |
| Datensatznummer |
250003350
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| Publikation (Nr.) |
 copernicus.org/os-6-161-2010.pdf |
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| Zusammenfassung |
| High-Frequency (HF) radars measure the ocean surface currents at various
spatial and temporal scales. These include tidal currents, wind-driven
circulation, density-driven circulation and Stokes drift. Sequential
assimilation methods updating the model state have been proven
successful to correct the density-driven currents by assimilation of
observations such as sea surface height, sea surface temperature and
in-situ profiles. However, the situation is different for tides in
coastal models since these are not generated within the domain, but
are rather propagated inside the domain through the boundary
conditions. For improving the modeled tidal variability it is
therefore not sufficient to update the model state via data
assimilation without updating the boundary conditions. The
optimization of boundary conditions to match observations inside the
domain is traditionally achieved through variational assimilation
methods. In this work we present an ensemble smoother to improve the
tidal boundary values so that the model represents more closely the
observed currents. To create an ensemble of dynamically realistic
boundary conditions, a cost function is formulated which is directly
related to the probability of each boundary condition perturbation. This cost function
ensures that the boundary condition perturbations are spatially smooth and that the
structure of the perturbations satisfies approximately the harmonic
linearized shallow water equations. Based on those perturbations an
ensemble simulation is carried out using the full three-dimensional
General Estuarine Ocean Model (GETM). Optimized boundary values are
obtained by assimilating all observations using
the covariances of the ensemble simulation. |
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