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Techniques de contrôle optimal pour un modèle quasi-géostrophique de circulation océanique. Application à l'assimilation variationnelle des données altimétriques satellitaires

Abstract : This thesis is concerned with the implementation of the optimal control numerical method applied to the data assimilation problem in oceanography. In this study, the question of the feasibility of this method is addressed for the case of a large dimension and turbulent model (turbulence is a prominent dynamical feature of mid-latitude circulation). We use a multilayered quasi-geostrophic circulation model. The assimilated data are altimeter satellite measurements (the surface topography). These data are given in the surface layer only. The control vector is the initial state for all layers of the dynamical system. We studied theoretically: - the existence and uniqueness of the solution of linearized equation; - the existence and uniqueness of the adjoint state; - the convergence of the control method using the minimizing sequences. A key issue is to assess the ability of assimilating surface-only altimeter data to control deep flows. We consider different strategies of splitting the assimilation period (sequential, incremental,...). The second order analysis of the cost-function allows the estimation of the identification error and the evaluation of the identification quality for the deep flows. The generalized cross-validation method is applied to this problem in order to determine the regularization parameter.
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Submitted on : Tuesday, February 24, 2004 - 2:46:58 PM
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Bruno Luong. Techniques de contrôle optimal pour un modèle quasi-géostrophique de circulation océanique. Application à l'assimilation variationnelle des données altimétriques satellitaires. Modélisation et simulation. Institut National Polytechnique de Grenoble - INPG, 1995. Français. ⟨tel-00005055⟩

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