Numéro : 2436 - Year : 2004
Hypothesis study about rogue waves compared with North Sea statistics
Michel OLAGNON, Centre IFREMER – Brest (France)
Anne Karin MAGNUSSON, Marine Forecasting Centre, Met.no – Bergen (Norvège)
There are no doubts that some waves exceed in height and severity common expectations derived from the sea conditions prevailing when they occur. Nevertheless, the link is still missing between on one hand the measurements that could be obtained and the theories that can be fit to them, and on the other hand, the global characteristics of the sea-states where they were observed. Such a correlation is an unavoidable stage in the construction and operation of real-time warning systems, and more generally on the way to risk lessening and avoidance.
The paper presents a study of some parameters that characterize sea conditions (significant wave hei¬ght, spectral width, Benjamin-Feir instability index, etc.), chosen because of their presumed capacity to take part in the generating mechanisms that are considered to theoretically explain the occurrence of rogue waves. Those parameters are computed for some noteworthy North Sea storms and their time-histories are studied. Statistical aleatory variability is estimated, so as to determine the significance of deviations from normal values. Meteorological configurations are also studied, with the intent to find connections between forecasts that can be put at the disposal of maritime industries and the hydrodynamic conditions favouring the occurrence of rogue waves. From those analyses, perspectives for the development of warning systems for maritime industries are revisited.
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