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Theses

Significant wave height variability and meso- and submesoscale current properties

Abstract : In this thesis, we show the effects of the surface current on the wave field with a particular interest in the significant wave height (Hs) variability and how Hs spatial gradients are related to the underlying current gradients. With a theoretical and idealized framework, we show that the current-induced refraction leads to a spatial redistribution of the wave action resulting in an inhomogeneity in the Hs field. Then, this inhomogeneity is described in an idealized numerical framework in an isolated mesoscale eddy. The nonlocal effects of the current in the Hs field have been highlighted in this study. Also, the variability of the Hs field is much more important in an eddy field dynamical at the meso- and the submesoscale range than in an eddy with a Gaussian shape. As eddies are not isolated in the ocean, we studied Hs gradients in a realistic framework in the Agulhas current. The sharp Hs gradients monitored by the new filtered altimeter data, are, on average, reproduced by the numerical wave models if forcing currents are sufficiently resolved. It proved the importance of small scale currents in the wave action spatial redistribution. The proportionality between the spatial gradients of the surface Kinetic Energy and Hs has been verified both by the numerical outputs and altimeter data at the mesoscale range. The directional data from SWIM sensors have shown first results motivating for future studies of current effects on the waves.
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Submitted on : Friday, September 23, 2022 - 12:25:17 PM
Last modification on : Saturday, September 24, 2022 - 3:53:44 AM

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  • HAL Id : tel-03784757, version 1

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Gwendal Maréchal. Significant wave height variability and meso- and submesoscale current properties. Oceanography. Université de Bretagne occidentale - Brest, 2022. English. ⟨NNT : 2022BRES0001⟩. ⟨tel-03784757⟩

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