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PhD Defense: Oliver GUILLET – “Modelling spatially correlated observation errors in varational data assimilation on unstructured meshes”

  Friday 8 February 2019 at 14h00

  Phd Thesis       Salle JCA, Cerfacs, Toulouse    

In this thesis, we propose a class of methods to represent spatial observation error correlations numerically in variational data assimilation. Based on the existing link between solutions of the time-implicit diffusion equation and Matérn correlation functions, we design correlation operators and inverse correlation operators that are appropriate for large datasets. Discretizing the diffusion equation with the finite element method allows us to account for data that do not necessarily lie on a structured mesh, as is the case with satellite observations assimilated in meteorology. Experiments are carried out using data from the infrared imager Seviri, the images of which are known for containing strong horizontal correlations. We show that the quality of our correlation model may depend locally on the spatial distribution of the observations. Nevertheless, by introducing an auxiliary mesh to perform the finite element computations, we can control this dependency to a large extent. Improving the accuracy of the method this way comes at the expense of making the inverse correlation operator more complicated. Finally, strategies for efficiently modelling the inverse of the correlation operator are proposed.

Jury :

Anthony Weaver           (Cerfacs)                                      Advisor
Michel Yann                  (Météo-France)                            Co Advisor
Marcin Chrust               (ECMWF, UK)                              Examiner
Selime Gürol                (Cerfacs)                                      Examiner
Serge Gratton              (INPT-IRIT)                                   Examiner
Marc Bocquet              (Ecole des Ponts Paris Tech)       Rapporteur
Emmanuel Cosme       (Université Grenoble Alpes)        Rapporteur
Arthur Vidard               (INRIA)                                         Rapporteur
Xavier Vasseur            (ISAE-Supaero)                           Invited member

CALENDAR

Monday

27

May

2024

🎓 PhD Defense: Thibault GIOUD

Monday 27 May 2024From 14h00 at 18h00

  Phd Thesis       Cerfacs, Toulouse, France    

Thursday

30

May

2024

Young PhD day (JDD2024@Cerfacs) – 30/05/2024

Thursday 30 May 2024From 9h00 at 17h00

  Journée des Doctorants       CERFACS     

Monday

03

June

2024

High fidelity simulations of Turbomachinery flows

From Monday 3 June 2024 to Wednesday 5 June 2024

  Training    

ALL EVENTS