Etude de la surface océanique, de sa signature radar et de ses interactions avec les flux turbulents de quantité de mouvement dans le cadre de l'experience FETCH

Abstract : This thesis deals with the study of the surface ocean waves and its relationships with the energy turbulent fluxes and radar backscatter. It was conducted in the frame of the FETCH (« Flux, Etat de la mer et Télédétection en Conditions de fetcH limité ») experiment, which took place in the Gulf of Lion, West Mediterranean Sea, in March and April 1998. The analysis of sea state is performed by using in situ measurements (buoys), and remote sensing from air (RESSAC radar) and space (TOPEX and ERS altimeters). Different sea-state conditions (developing sea, mixed sea, or swell) associated with various meteorological situations (Mistral, Tramontane or Marin winds) are detailed. The wave train decomposition in components recognised as wind-sea ( waves generated by local wind) or swell, was used to classify different sea states. The growing law of the ocean waves was established for pure wind sea cases observed at the buoy location.. This law differs significantly from those proposed in the literature. These data sets were used to compare sea state from measurements and from numerical prediction models. This study emphasizes the need, for this coastal region, of high spatial resolution of wind fields and sea-state models. An analysis of the sea state influence on the turbulent flux of momentum was performed using data from the ASIS buoy, and the research vessel L'Atalante. For wind sea cases, exchange coefficients for momentum turbulent fluxes are shown to be dependent on wave age, but not on significant wave slope as it was suggested in other studies discussed in literature. Analysis of radar backscatter at small incidence angle (less than 12°) showed that the sea surface mean square slope is not very sensitive to parameters as wind intensity, wave age or wave slope.
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Céline Gwenaëlle Quentin. Etude de la surface océanique, de sa signature radar et de ses interactions avec les flux turbulents de quantité de mouvement dans le cadre de l'experience FETCH. Physique [physics]. Université Pierre et Marie Curie - Paris VI, 2002. Français. ⟨tel-00010934⟩

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