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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 17, issue 11
Ann. Geophys., 17, 1463–1477, 1999
https://doi.org/10.1007/s00585-999-1463-9
© European Geosciences Union 1999
Ann. Geophys., 17, 1463–1477, 1999
https://doi.org/10.1007/s00585-999-1463-9
© European Geosciences Union 1999

  30 Nov 1999

30 Nov 1999

Turbulent viscosity optimized by data assimilation

Y. Leredde1, J.-L. Devenon2, and I. Dekeyser1 Y. Leredde et al.
  • 1Centre d'Océanologie de Marseille, Université de la Méditerranée, Campus de Luminy-Case 901-F 13288 Marseille Cedex 9, France
  • e-mail: leredde@com.univ-mrs.fr
  • 2LSEET, Université de Toulon et du Var, BP 132-F 83957 La Garde Cedex, France

Abstract. As an alternative approach to classical turbulence modelling using a first or second order closure, the data assimilation method of optimal control is applied to estimate a time and space-dependent turbulent viscosity in a three-dimensional oceanic circulation model. The optimal control method, described for a 3-D primitive equation model, involves the minimization of a cost function that quantifies the discrepancies between the simulations and the observations. An iterative algorithm is obtained via the adjoint model resolution. In a first experiment, a k + L model is used to simulate the one-dimensional development of inertial oscillations resulting from a wind stress at the sea surface and with the presence of a halocline. These results are used as synthetic observations to be assimilated. The turbulent viscosity is then recovered without the k + L closure, even with sparse and noisy observations. The problems of controllability and of the dimensions of the control are then discussed. A second experiment consists of a two-dimensional schematic simulation. A 2-D turbulent viscosity field is estimated from data on the initial and final states of a coastal upwelling event.

Key words. Oceanography: general (numerical modelling) · Oceanography: physical (turbulence · diffusion · and mixing processes)

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