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Ocean Science An interactive open-access journal of the European Geosciences Union
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Volume 12, issue 2 | Copyright
Ocean Sci., 12, 577-599, 2016
https://doi.org/10.5194/os-12-577-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 22 Apr 2016

Research article | 22 Apr 2016

Design and validation of MEDRYS, a Mediterranean Sea reanalysis over the period 1992–2013

Mathieu Hamon1, Jonathan Beuvier1,2, Samuel Somot2, Jean-Michel Lellouche1, Eric Greiner3, Gabriel Jordà4, Marie-Noëlle Bouin2, Thomas Arsouze5, Karine Béranger6, Florence Sevault2, Clotilde Dubois1, Marie Drevillon1, and Yann Drillet1 Mathieu Hamon et al.
  • 1Mercator Océan, 10 rue Hermès, 31520 Ramonville-Saint-Agne, France
  • 2Météo France, 42 av. Gaspard Coriolis, 31057 Toulouse CEDEX, France
  • 3CLS, 11 rue Hermès, 31520 Ramonville-Saint-Agne, France
  • 4Department of Ecology and Marine Resources, IMEDEA (CSIC-UIB), Institut Mediterrani d'Estudis Avançats, Esporles (Illes Balears), Spain
  • 5LMD, école Polytechnique, 91128 Palaiseau CEDEX, France
  • 6LTHE, rue de la Piscine, 38400 Saint-Martin d'Hère, France

Abstract. The French research community in the Mediterranean Sea modeling and the French operational ocean forecasting center Mercator Océan have gathered their skill and expertise in physical oceanography, ocean modeling, atmospheric forcings and data assimilation to carry out a MEDiterranean sea ReanalYsiS (MEDRYS) at high resolution for the period 1992–2013. The ocean model used is NEMOMED12, a Mediterranean configuration of NEMO with a 1∕12° ( ∼ 7km) horizontal resolution and 75 vertical z levels with partial steps. At the surface, it is forced by a new atmospheric-forcing data set (ALDERA), coming from a dynamical downscaling of the ERA-Interim atmospheric reanalysis by the regional climate model ALADIN-Climate with a 12km horizontal and 3h temporal resolutions. This configuration is used to carry a 34-year hindcast simulation over the period 1979–2013 (NM12-FREE), which is the initial state of the reanalysis in October 1992. MEDRYS uses the existing Mercator Océan data assimilation system SAM2 that is based on a reduced-order Kalman filter with a three-dimensional (3-D) multivariate modal decomposition of the forecast error. Altimeter data, satellite sea surface temperature (SST) and temperature and salinity vertical profiles are jointly assimilated. This paper describes the configuration we used to perform MEDRYS. We then validate the skills of the data assimilation system. It is shown that the data assimilation restores a good average temperature and salinity at intermediate layers compared to the hindcast. No particular biases are identified in the bottom layers. However, the reanalysis shows slight positive biases of 0.02psu and 0.15°C above 150m depth. In the validation stage, it is also shown that the assimilation allows one to better reproduce water, heat and salt transports through the Strait of Gibraltar. Finally, the ability of the reanalysis to represent the sea surface high-frequency variability is shown.

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The paper describes MEDRYS, a MEDiterranean sea ReanalYsiS at high resolution for the period 1992–2013. The NEMOMED12 ocean model is forced at the surface by a new high resolution atmospheric forcing dataset (ALDERA). Altimeter data, satellite SST and temperature and salinity vertical profiles are jointly assimilated. The ability of the reanalysis to represent the sea surface high-frequency variability, water mass characteristics and transports through the Strait of Gibraltar is shown.
The paper describes MEDRYS, a MEDiterranean sea ReanalYsiS at high resolution for the period...
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