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The “Design Wave Philosophy’’ Calculation of the design wave

Remote-Sensing of Sea Conditions. The “Design Wave Philosophy’’ Calculation of the design wave Wave forces on semi-submersible platforms Wave forces and bending moments in FPSO-ships Platform movements in large waves Examples of heavy weather damage What is a Rogue Wave ?

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The “Design Wave Philosophy’’ Calculation of the design wave

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  1. Remote-Sensing of Sea Conditions The “Design Wave Philosophy’’ Calculation of the design wave Wave forces on semi-submersible platforms Wave forces and bending moments in FPSO-ships Platform movements in large waves Examples of heavy weather damage What is a Rogue Wave ? Why, where and when ? Shall we design against Rogue and Freak Waves ? What can a platform master do against Rogue and Freak Waves ? ***** Remote-sensing of sea conditions ***** Search And Rescue and emergency operations Decision making in an emergency

  2. Remote-Sensing of Sea Conditions

  3. Remote-Sensing of Sea Conditions • Satellite measurements • Merging remote-sensing and forecasts • Comkiss and Cammeo projects results • Remote-sensing and rogue waves

  4. Remote-Sensing of Sea Conditions Satellites can measure many ocean parameters: colour,

  5. Waves,

  6. Effects of bathymetry on ocean surface,

  7. Wind,

  8. Remote-Sensing of Sea Conditions How can a satellite measure waves ? • A side-product of the altimeter noise, or • A side-product of the imaging synthetic aperture radar. • Keep in mind that the sensors were designed for other purposes than wave measurement

  9. Remote-Sensing of Sea Conditions Altimeter

  10. Remote-Sensing of Sea Conditions Scatterometer

  11. Remote-Sensing of Sea Conditions Synthetic aperture radar (SAR)

  12. Remote-Sensing of Sea Conditions Synthetic aperture radar (SAR)

  13. Remote-Sensing of Sea Conditions Synthetic aperture radar (SAR)

  14. Remote-Sensing of Sea Conditions

  15. Some problems: Altimeter returns are noisy Altimeter return signal is lower when winds are higher Scatterometer winds require model “first guess” to get the direction.

  16. Problem: One does not get a measurement where and when it would be needed

  17. Problems: SAR inversion is a complex process, no unique solution, and requiring a first guess. SAR imagettes are frequently unusable SAR misses all waves below 45m wavelength and some longer ones in the azimuth direction

  18. Remote-Sensing of Sea Conditions • Satellite measurements • Merging remote-sensing and forecasts • Comkiss and Cammeo projects results • Remote-sensing and rogue waves

  19. Measurements w.r.t. Forecasts • Problem: • It takes several hours to • retrieve the data from the satellite • process them • validate them • make them available to service providers • In addition, ESA would like to make money out of them, so the question arises of what improvement over conventional forecasts ?

  20. Measurements w.r.t. Forecasts An example: San Francisco-Guam cable laying

  21. Measurements w.r.t. Forecasts An example: San Francisco-Guam cable laying

  22. Measurements w.r.t. Forecasts Agreement: service of little use to shipmaster

  23. Measurements w.r.t. Forecasts Disagreement:

  24. Measurements w.r.t. Forecasts Warning

  25. Measurements w.r.t. Forecasts Conclusions: Warning was not fetched and thus arrived too late Sending forecasts and corrections to them is not a good option, one should rather send the best forecast possible

  26. Remote-Sensing of Sea Conditions • Satellite measurements • Merging remote-sensing and forecasts • Comkiss and Cammeo projects results • Remote-sensing and rogue waves

  27. Remote-Sensing of Sea Conditions • Other Comkiss and Cammeo projects results: • Several reliable sources provide surface currents • Several reliable sources provide wave climate databases (DNV has pushed to acceptance of satellite databases for design) • Improvement of the databases used for fatigue • http://www.ifremer.fr/metocean/shipping/shipping.html

  28. Remote-Sensing of Sea Conditions • Other Comkiss and Cammeo projects results: • High Speed Crafts operations (and thus offshore operations too) planning and conducting are not significantly improved. • Forecast enhancement from satellite as well as from platform motion measurements is not yet mature. • http://www.ifremer.fr/metocean/shipping/shipping.html

  29. Remote-Sensing of Sea Conditions • Satellite measurements • Merging remote-sensing and forecasts • Comkiss and Cammeo projects results • Remote-sensing and rogue waves

  30. Remote-Sensing of Sea Conditions Some scientists claim that they can see rogue waves on SAR images or imagettes.

  31. One should be aware that: • SAR measurements, on the opposite to altimeter ones, show a great deal of uncertainty on Hs

  32. uncertainty on the individual wave height measured by a satellite is very high

  33. the maximum wave height over an area is theoretically higher than when observing waves passing by a fixed point

  34. Conclusions • Altimeter measurements of Hs are reliable • Wind measurements are reliable, except in extreme conditions • Forecast enhancement from satellite data is not yet mature • Rogue wave detection is still a topic for academic research.

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