Sunday, February 01, 2009

May be or may be not, that is the question!

A paper published in the latest Geophysical Research Letters is making news. Here's the public available abstract:
On 23 June 2008, a fishing boat with 20 crewmembers onboard sank in reportedly moderate sea-state conditions in the Kuroshio Extension region east of Japan. To determine the sea state at the time of the incident, we conducted a hindcast wave simulation, as realistically as possible, using an improved third-generation wave model driven by wind and current reanalysis products. Our results indicated that at the time of the accident, the wave steepness increased and the spectral peakedness narrowed, creating a sea state favorable for freak wave occurrence due to quasi-resonance. Detailed analyses of the spectral evolution revealed that nonlinear coupling of swell and windsea waves was the key to generating the narrow spectrum. Under the influence of rising wind speed, the swell system grew exponentially at the expense of the windsea energy, and the bimodal crossing sea state transformed into a freakish unimodal sea.
The news of the lost of the fishing boat did not seem to get around the international circuit and the abstract did not give much details either. Some immediate questions: What was the fate of the crew members? Was there any indication of freaque waves at the time? Was there any actural wave measurement? Since it was reported "moderate sea-state conditions" why the need for a "hindcast wave simulation"? There has never been an even plausible evidence of any connection between wave models and freaque waves, what does it mean by "bimodal crossing sea state transformed into a freakish unimodal sea?"

Nevertheless, Science Daily seems to have impressed and reported this paper with the title: "Freak Waves May Be Sinking Ships Off The Coast of Japan." Or may be not, and all is a question of speculation. In the era of model almighty, any simulation by an "improved 3rd generation" model and added an ingradient of "nonlinear coupling" will be easily becoming media reality. But the mere truth is: we haven't learned anything new yet!


The case of the Japanese fishing vessel, Suwa Maru No. 58, was actually reported in Intrafish of Norway on June 24, 2008 the day after the happening:


Portsmouth, UK, June 24. Fishing vessel Suwa Maru No.58 (135 gt, built 1999) overturned and sank 330 km from the Pacific coast of Chiba prefecture, Japan, on June 23. According to the Coast Guard, the vessel had a crew of 20 and seven were rescued about an hour after the incident. However, four of them died shortly afterwards. The search for the remaining 13 crew continued. Five Japanese patrol vessels and three aircraft were sent to the area, and these were joined by 34 fishing vessels at the accident site. Equipment from the vessel was recovered on June 24, but not her 13 missing crew. Local media reports said the vessel capsized after she was hit by high waves in rough seas.

But the news had not been well circulated.

On February 16, 2009 a new article by Robert Matthews that was appeared in The National of Abu Dhabi in an effort of discussing freaque waves and reporting on Suwa Maru No. 58 and the GRL paper by Tamura et al., however, was tainted with clear factual error when it reported that "a monster of the sea which claimed the ship and all 22 on board."

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