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| Titel |
Coherence and predictability of extreme events in irregular waves |
| VerfasserIn |
A. L. Latifah, E. Groesen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 19, no. 2 ; Nr. 19, no. 2 (2012-03-26), S.199-213 |
| Datensatznummer |
250014188
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| Publikation (Nr.) |
 copernicus.org/npg-19-199-2012.pdf |
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| Zusammenfassung |
This paper concerns the description and the predictability of a freak event
when at a certain position information in the form of a time signal is given.
The prediction will use the phase information for an estimate of the position
and time of the occurrence of a large wave, and to predict the measure of
phase coherence at the estimated focussing position. The coherence and the
spectrum will determine an estimate for the amplitude. After adjusting for
second order nonlinear effects, together this then provides an estimate of
the form of a possible freak wave in the time signal, which will be described
by a pseudo-maximal signal. In the exceptional case of a fully coherent
signal, it can be described well by a so-called maximal signal.
We give four cases of freak waves for which we compare results of predictions
with available measured (and simulated) results by nonlinear AB-equation (van Groesen and Andonowati, 2007; van Groesen et al., 2010). The first case deals with dispersive focussing, for which all phases are (designed to be) very coherent at position and time of
focussing; this wave is nearly a maximal wave. The second case is the
Draupner wave, for which the signal turns out to be recorded very close to
its maximal wave height. It is less coherent but can be described in a good
approximation as a pseudo-maximal wave. The last two cases are irregular
waves which were measured at MARIN (Maritime Research Institute Netherlands);
in a time trace of more than 1000 waves freak-like waves appeared
"accidentally". Although the highest wave is less coherent than the other
two cases, this maximal crest can still be approximated by a pseudo-maximal
wave. |
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