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Article Dans Une Revue Ocean Modelling Année : 2013

Space-time measurements of oceanic sea states

Francesco Fedele
  • Fonction : Auteur
Alvise Benetazzo
  • Fonction : Auteur
Guillermo Gallego
  • Fonction : Auteur
Ping-Chang Shih
  • Fonction : Auteur
Anthony Yezzi
  • Fonction : Auteur
Francesco Barbariol
  • Fonction : Auteur
Fabrice Ardhuin

Résumé

Stereo video techniques are effective for estimating the space-time wave dynamics over an area of the ocean. Indeed, a stereo camera view allows retrieval of both spatial and temporal data whose statistical content is richer than that of time series data retrieved from point wave probes. We present an application of the Wave Acquisition Stereo System (WASS) for the analysis of offshore video measurements of gravity waves in the Northern Adriatic Sea and near the southern seashore of the Crimean peninsula, in the Black Sea. We use classical epipolar techniques to reconstruct the sea surface from the stereo pairs sequentially in time, viz. a sequence of spatial snapshots. We also present a variational approach that exploits the entire data image set providing a global space-time imaging of the sea surface, viz. simultaneous reconstruction of several spatial snapshots of the surface in order to guarantee continuity of the sea surface both in space and time. Analysis of the WASS measurements show that the sea surface can be accurately estimated in space and time together, yielding associated directional spectra and wave statistics at a point in time that agrees well with probabilistic models. In particular, WASS stereo imaging is able to capture typical features of the wave surface, especially the crest-to-trough asymmetry due to second order nonlinearities, and the observed shape of large waves are fairly described by theoretical models based on the theory of quasi-determinism (Boccotti, 2000). Further, we investigate space-time extremes of the observed stationary sea states, viz. the largest surface wave heights expected over a given area during the sea state duration. The WASS analysis provides the first experimental proof that a space-time extreme is generally larger than that observed in time via point measurements, in agreement with the predictions based on stochastic theories for global maxima of Gaussian fields.

Dates et versions

hal-04499430 , version 1 (11-03-2024)

Identifiants

Citer

Francesco Fedele, Alvise Benetazzo, Guillermo Gallego, Ping-Chang Shih, Anthony Yezzi, et al.. Space-time measurements of oceanic sea states. Ocean Modelling, 2013, 70, pp.103-115. ⟨10.1016/j.ocemod.2013.01.001⟩. ⟨hal-04499430⟩
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