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Home > News > Ph.D. Thesis > Ph.D. Thesis 2009

Soutenance de thèse de Clement Ubelmann


Altimetric scenario study for the ocean circulation control in the tropical Atlantic ocean through data assimilation


The main goal of this thesis is to evaluate the contribution of altimetric satellite data to constrain the ocean circulation of the Tropical Altantic through data assimilation.
An Observing System Simulation Experiments (OSSE) strategy has been used in a twin experiment context with the NEMO circulation model in an embedded configuration with a 0.25° spatial resolution.
These experiments have been distincly performed for two different phenomena in the Tropical Atlantic : the Tropical Instalibity Waves (TIW) and the vortices associated to the North Brazil Current (NBC).
Several altimetric scenarios have been tested, with existing satellites (JASON-1, JASON-2 or ENVISAT ...), planned satellites (SARAL) or future projects like SWOT.
Different orbit options have been considerated.
The main results have shown that if a single satellite is sufficient to constrain the TIW and NBC vortices position, a multi satellite system is necessary to correct their vertical structure.
Some orbits turned out to be more favorable than other to correct TIW or NBC vortices.
Moreover, the existence of specific sampling criteria (repetitivity cycle, sub-cycles) appeared to be decisive for correction.
Improvements with wide swath altimetry assimilation (that should be operational in the next decade) have also been clearly shown.

key-word : altimetry – ocean modeling – data assimilation – OSSE – tropical Atlantic

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