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| Titel |
Evaluation of global monitoring and forecasting systems at Mercator Océan |
| VerfasserIn |
J.-M. Lellouche, O. Galloudec, M. Drévillon, C. Régnier, E. Greiner, G. Garric, N. Ferry, C. Desportes, C.-E. Testut, C. Bricaud, R. Bourdallé-Badie, B. Tranchant, M. Benkiran, Y. Drillet, A. Daudin, C. Nicola |
| 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 ; 9, no. 1 ; Nr. 9, no. 1 (2013-01-17), S.57-81 |
| Datensatznummer |
250017451
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| Publikation (Nr.) |
 copernicus.org/os-9-57-2013.pdf |
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| Zusammenfassung |
Since December 2010, the MyOcean global analysis and forecasting system
has consisted of the Mercator Océan NEMO global 1/4° configuration
with a 1/12° nested model over the Atlantic and the Mediterranean.
The open boundary data for the nested configuration come from the global
1/4° configuration at 20° S and 80° N.
The data are assimilated by means of a reduced-order Kalman filter with a
3-D multivariate modal decomposition of the forecast error. It includes an
adaptive-error estimate and a localization algorithm. A 3-D-Var scheme
provides a correction for the slowly evolving large-scale biases in
temperature and salinity. Altimeter data, satellite sea surface temperature
and in situ temperature and salinity vertical profiles are jointly
assimilated to estimate the initial conditions for numerical ocean
forecasting. In addition to the quality control performed by data producers,
the system carries out a proper quality control on temperature and salinity
vertical profiles in order to minimise the risk of erroneous observed
profiles being assimilated in the model.
This paper describes the recent systems used by Mercator Océan and the
validation procedure applied to current MyOcean systems as well as systems
under development. The paper shows how refinements or adjustments to the
system during the validation procedure affect its quality. Additionally, we
show that quality checks (in situ, drifters) and data sources (satellite sea
surface temperature) have as great an impact as the system design (model
physics and assimilation parameters). The results of the scientific
assessment are illustrated with diagnostics over the year 2010 mainly,
assorted with time series over the 2007–2011 period. The validation
procedure demonstrates the accuracy of MyOcean global products, whose
quality is stable over time. All monitoring systems are close to altimetric
observations with a forecast RMS difference of 7 cm. The update of the mean
dynamic topography corrects local biases in the Indonesian Throughflow and
in the western tropical Pacific. This improves also the subsurface currents
at the Equator. The global systems give an accurate description of water
masses almost everywhere. Between 0 and 500 m, departures from in situ
observations rarely exceed 1 °C and 0.2 psu. The assimilation of
an improved sea surface temperature product aims to better represent the
sea ice concentration and the sea ice edge. The systems under development
are still suffering from a drift which can only be detected by means of a 5-yr hindcast, preventing us from upgrading them in real time. This emphasizes
the need to pursue research while building future systems for MyOcean2
forecasting. |
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