What can altimetry tell us about Rogue waves?

Image of the month - February 2004

Five years of ship accidents due to bad weather. It includes total losses to all propelled sea-going merchant ships in the world of about 100 tons and more. (Credits Lloyd’s Marine Information Service).

"Rogue waves" are believed to be the cause of many accidents at sea. They are mostly individual waves of exceptional height and/or abnormal shape which cannot be detected with altimetry, as it averages measurements over several square kilometers.
Studies were conducted [Toffoli et al., 2003] for the European project MaxWave, to try and link the occurrence of such waves to some sea state properties simulated by a wave model. Altimetry data from Topex/Poseidon, Envisat and Jason-1 were then used to validate the results of wave model simulation . These proved that for two-third of the shipwrecks studied, the significant wave height was below 4 m. This means that if a ship had an accident under those conditions, it is likely that rogue waves were involved.

Comparison between significant wave heights simulated by the ECMWF WAM model and actual wave heights measured by altimletry. Credits Météo-France / Ifremer.

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References

  • Toffoli A., J.-M. Lefevre, J. Montbaliu, H. Savina, E. Bitner, 2003: Freak waves: clues for prediction in ship accidents?, proceedings of the ISOPE conference, Honolulu, Hawaii, USA - May 25-30, 2003