Posted on 07/22/2004 10:25:27 PM PDT by uglybiker
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Rare photo of a rogue wave
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Mariners who survived similar encounters have had remarkable stories to tell. In February 1995 the cruiser liner Queen Elizabeth II met a 29-metre high rogue wave during a hurricane in the North Atlantic that Captain Ronald Warwick described as "a great wall of water… it looked as if we were going into the White Cliffs of Dover."
And within the week between February and March 2001 two hardened tourist cruisers – the Bremen and the Caledonian Star – had their bridge windows smashed by 30-metre rogue waves in the South Atlantic, the former ship left drifting without navigation or propulsion for a period of two hours.
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Damage done by a rogue wave
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"The same phenomenon could have sunk many less lucky vessels: two large ships sink every week on average, but the cause is never studied to the same detail as an air crash. It simply gets put down to 'bad weather'."
Offshore platforms have also been struck: on 1 January 1995 the Draupner oil rig in the North Sea was hit by a wave whose height was measured by an onboard laser device at 26 metres, with the highest waves around it reaching 12 metres.
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Giant wave in Bay of Biscay
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The fact that rogue waves actually take place relatively frequently had major safety and economic implications, since current ships and offshore platforms are built to withstand maximum wave heights of only 15 metres.
In December 2000 the European Union initiated a scientific project called MaxWave to confirm the widespread occurrence of rogue waves, model how they occur and consider their implications for ship and offshore structure design criteria. And as part of MaxWave, data from ESA's ERS radar satellites were first used to carry out a global rogue wave census.
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ERS satellite
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ESA's twin spacecraft ERS-1 and 2 – launched in July 1991 and April 1995 respectively – both have a Synthetic Aperture Radar (SAR) as their main instrument.
The SAR works in several different modes; while over the ocean it works in wave mode, acquiring 10 by 5 km 'imagettes' of the sea surface every 200 km.
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Example of an imagette from ERS-2
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"The raw imagettes are not made available, but with their resolution of ten metres we believed they contained a wealth of useful information by themselves," said Rosenthal. "Ocean wave spectra provide mean sea state data but imagettes depict the individual wave heights including the extremes we were interested in.
"ESA provided us with three weeks' worth of data – around 30,000 separate imagettes – selected around the time that the Bremen and Caledonian Star were struck. The images were processed and automatically searched for extreme waves at the German Aerospace Centre (DLR)."
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Giant wave detected in ERS-2 imagette data
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"Having proved they existed, in higher numbers than anyone expected, the next step is to analyse if they can be forecasted," Rosenthal added. "MaxWave formally concluded at the end of last year although two lines of work are carrying on from it – one is to improve ship design by learning how ships are sunk, and the other is to examine more satellite data with a view to analysing if forecasting is possible."
A new research project called WaveAtlas will use two years worth of ERS imagettes to create a worldwide atlas of rogue wave events and carry out statistical analyses. The Principal Investigator is Susanne Lehner, Associate Professor in the Division of Applied Marine Physics at the University of Miami, who also worked on MaxWave while at DLR, with Rosental a co-investigator on the project.
"Only radar satellites can provide the truly global data sampling needed for statistical analysis of the oceans, because they can see through clouds and darkness, unlike their optical counterparts. In stormy weather, radar images are thus the only relevant information available."
So far some patterns have already been found. Rogue waves are often associated with sites where ordinary waves encounter ocean currents and eddies. The strength of the current concentrates the wave energy, forming larger waves – Lehner compares it to an optical lens, concentrating energy in a small area.
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Giant wave in a wave tank
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However the data show rogue waves also occur well away from currents, often occurring in the vicinity of weather fronts and lows. Sustained winds from long-lived storms exceeding 12 hours may enlarge waves moving at an optimum speed in sync with the wind – too quickly and they'd move ahead of the storm and dissipate, too slowly and they would fall behind.
"We know some of the reasons for the rogue waves, but we do not know them all," Rosenthal concluded. The WaveAtlas project is scheduled to continue until the first quarter of 2005.
bump
ping
Walking causes ass cancer.
Bummer, I already hate flying and now giant waves! I guess I'll have to walk everywhere.
****
Don't forget earthquakes....:)
Did anyone wave back?
Please FREEPMAIL me if you want on, off, or alter the "Gods, Graves, Glyphs" PING list --
Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
The GGG Digest -- Gods, Graves, Glyphs (alpha order)
I was about 2 miles off shore of an island in a 21 foot Boston Whaler. Due to a storm miles away, we had swells that measured 20-30 feet crest to trough. The wind was blowing the usual 24 knots and it was sunny. A wave came through that was nearly twice the height of the others and with a blowing whitecap. The Whaler was a light boat and rode over the wave, but we got wet and damned near dirty, if you know what I mean. I wasn’t much of a sailor at the time and didn’t think twice about it, other than thinking it was a freaky wave. It stood out from the others. I can imagine rogue waves that can sink a ship.
"Did anyone wave back?"
After the onster wved I think the satellite wiggled back but it was too small for the monster to see.
The Titanic was big enough to ride three waves and thus was relatively stable in pitch on the open ocean. A rogue wave, though, would be single and if it came from the side might roll the ship severely, maybe beyond the point of stability.
How could a ship sink a monster. I don't get it.
You have big brass ones. I would have moved - to Montana.
Well, I do live in Denver, now.
How odd - I was in Denver this afternoon. Then I was in texas, and now I am in New Mexico.
No cruises for me!
Nope, it's "Nessie" !
: P
I might change my mind about that cruise.
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