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| Titel |
First results of MEDRYS, a 1992-2013 Mediterranean Sea reanalysis |
| VerfasserIn |
Jonathan Beuvier, Mathieu Hamon, Jean-Michel Lellouche, Antoinette Alias, Thomas Arsouze, Mounir Benkiran, Karine Béranger, Yann Drillet, Florence Sevault, Samuel Somot |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092862
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| Publikation (Nr.) |
 EGU/EGU2014-7226.pdf |
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| Zusammenfassung |
| The French research community on the Mediterranean Sea and the French operational ocean forecasting center Mercator Océan are gathering their skills and expertises in physical oceanography, ocean modelling, atmospheric forcings and data assimilation, to carry out a MEDiterranean Sea ReanalYsiS (MEDRYS) at high resolution for the period 1992-2013. The reanalysis is used to have a realistic description of the ocean state over the recent decades and it will help to understand the long-term water cycle over the Mediterranean basin in terms of variability and trends, contributing thus to the HyMeX international program.
The ocean model used is NEMOMED12 [Lebeaupin Brossier et al., 2011, Oc. Mod., 2012, Oc. Mod.; Beuvier et al., 2012a, JGR, 2012b, Mercator Newsl.], a Mediterranean configuration of NEMO [Madec and the NEMO Team, 2008], with a 1/12° (~ 7 km) horizontal resolution and 75 vertical z-levels with partial steps. It is forced by the atmospheric fluxes coming from an ALADIN-Climate simulation at 12 km of resolution [Herrmann et al., 2011, NHAES], driven by the ERA-Interim atmospheric reanalysis. The exchanges with the Atlantic Ocean are performed through a buffer zone, with a damping on 3D theta-S and on sea level towards the ORA-S4 oceanic reanalysis [Balmaseda et al., 2012, QJRMS]. This model configuration is used to carry a 34-year free simulation over the period 1979-2013. This free simulation is the initial state of the reanalysis in 1992. It is also used to compute anomalies from which the data assimilation scheme derives required characteristic covariances of the ocean model.
The first version of MEDRYS uses the current Mercator Océan operational data assimilation system [Lellouche et al., 2013, Oc.Sci.]. In a second time, we will improve it and/or make it more specific to the Mediterranean area. The current operational data assimilation system uses a reduced order Kalman filter with a 3D multivariate modal decomposition of the forecast error. A 3D-Var scheme corrects biases in temperature and salinity for the slowly evolving large-scale. Altimeter data, satellite SST and temperature and salinity vertical profiles are jointly assimilated. The reanalysis also benefits from the intensive observational field campaigns carried out during the HyMeX Special Observation Periods in fall 2012 and winter 2013 in the north-western Mediterranean Sea.
We assess the ability of MEDRYS to reproduce the general circulation and the water masses in the Mediterranean Sea. Diagnostics of the misfit between the reanalysis and the assimilated observations, as well as differences between the reanalysis and its twin free simulation, allow to discriminate the relative impact of the oceanic model and the assimilation system on the results of the reanalysis. |
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