Space-time Measurements of Oceanic Sea States

Fedele, Francesco and Benetazzo, Alvise and Gallego Bonet, Guillermo and Shih, Ping-Chang and Yezzi, Anthony and Barbariol, Francesco and Ardhuin, Fabrice (2013). Space-time Measurements of Oceanic Sea States. "Ocean Modelling", v. 70 ; pp. 103-115. ISSN 1463-5003.


Title: Space-time Measurements of Oceanic Sea States
  • Fedele, Francesco
  • Benetazzo, Alvise
  • Gallego Bonet, Guillermo
  • Shih, Ping-Chang
  • Yezzi, Anthony
  • Barbariol, Francesco
  • Ardhuin, Fabrice
Item Type: Article
Título de Revista/Publicación: Ocean Modelling
Date: October 2013
Volume: 70
Freetext Keywords: Stereo measurement; WASS; Wave number-frequency spectrum; Wave statistics; Space–time extremes
Faculty: E.T.S.I. Telecomunicación (UPM)
Department: Señales, Sistemas y Radiocomunicaciones
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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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.

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Item ID: 19076
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Deposited by: Dr Guillermo Gallego Bonet
Deposited on: 28 Aug 2013 08:34
Last Modified: 21 Apr 2016 17:19
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