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Gravity Waves in the Atmosphere can Energize Tornados (Video)

Gravity waves propagating through the atmosphere from the Australian coast (credit: University of Edinburgh)
Gravity waves are global events. Much like the ripples on a massive pond, these large-scale waves can propagate from an atmospheric disturbance over thousands of miles. These waves are maintained by the gravitational force of Earth pulling down and the buoyancy of the atmosphere pushing up. Until now it has been hard to link atmospheric gravity waves with other atmospheric phenomena, but new research suggests that gravity waves passing over storms can spin up highly dangerous and damaging tornados… Suddenly gravity waves become very important and may help to forecast where and when tornados may strike…

In a nutshell, meteorologist Tim Coleman of the National Space Science and Technology Center in Huntsville (Alabama) sums up what gravity waves are:

They are similar to waves on the surface of the ocean, but they roll through the air instead of the water. Gravity is what keeps them going. If you push water up and then it plops back down, it creates waves. It’s the same with air.” – Coleman

A large number of things may cause gravity waves (not to be confused with gravitational waves, the ripples in space-time), including intense disturbances caused by storm systems, a sudden change in jet stream location or wind shear. The strong oscillation will then travel for hundreds or even thousands of miles.

Still from a movie of a gravity wave passing over Tama, Iowa in 2006 (credit: Iowa Environmental Mesonet Webcam)

See a gravity wave in action over Iowa…

Far from gravity waves being a mild curiosity, it seems that they have a large part to play with other atmospheric dynamics down here on the ground.

Tim Coleman and colleagues have found that the passage of gravity waves over the top of storms could intensify or even create tornados. It is all down to the angular momentum of the spinning storm. When storms are large, they slowly rotate. If for some reason they shrink in scale, the spin will increase (imagine an ice-skater spinning on the ice with her arms outstretched, as she brings her arms in, she spins faster). This is the fundamental rule of angular momentum conservation, as the size of a storm contracts, the faster it spins. Ultimately, if the conditions are right, intense tornados can be generated, a huge amount of angular momentum in a tiny volume.

Now gravity waves are believed to have a part to play. As they pass over a storm, the pressure of the overlying gravity wave propagation will compress the storm. As this occurs, a vast amount of angular momentum is forced into a smaller volume. The seeding of baby tornados is therefore possible. Gravity waves also come in sets; one wave will follow another, each periodically compressing the storm, intensifying tornado generation.

So keep your eyes peeled for incoming gravity waves during a storm… tornados may spin to life…

Source: NASA

Comments on this entry are closed.

  • TobiasMar March 19, 2008, 3:56 PM

    I think it would have been better to call these “atmospheric waves” or “air waves” because “gravity waves” may cause a lot of confusion.

  • chewy March 20, 2008, 3:53 AM

    But airwave is a trademark already.
    So gravity wave sounds cooler.

    It gives a much better feeling, a notion of something huge and powerful and scary.

    Just like tornado sounds scary and powerful.

  • nathan March 20, 2008, 4:45 AM

    Are these the same type Gravitational Waves that are trying to be detected coming from colliding black holes and such? Or are these completely different beast. I was under the impression that science has never actually detected gravity waves yet?

    Thanks

  • Dark Gnat March 20, 2008, 5:31 AM

    Nope, entirlry different activity.

  • Vicky Pollard March 20, 2008, 5:44 AM

    That name must be an American-ism. In other parts of the world, these waves aren’t called the confusing name ‘gravitational waves’, they’re called ‘undular bore waves’.

  • Michael Huster March 20, 2008, 6:05 AM

    Actually “gravity waves” in reference to these is not a new term at all. It is the general term for waves in a fluid for which the restoring force is gravity. I don’t think this is an americanism. There is a further distinction between “surface gravity waves” (the waves (ocean) surfers ride), and “internal waves” that are an oscillation in the volume of a fluid. This story is about internal atmospheric waves.

    Internal waves have been well studied in both the atmosphere and in the ocean for a long time. (I think the US Navy has been looking for internal waves caused by submarines.)

    In contrast I think “bore waves” are singular waves, often caused by tides. But I’m not sure about this term.

  • smart ass March 20, 2008, 11:20 AM

    gravity waves and gravitational waves

  • Brian March 20, 2008, 11:46 AM

    Maybe we should use something similar to Star Trek’s technobabble generator to name stuff like this.

  • joker March 20, 2008, 3:13 PM

    Well – many universe today articles ARE technobabble or maybe sciencebabble

  • Raven March 20, 2008, 3:57 PM

    Is there any correlation between these gravitational waves in the air and rogue waves in the ocean?

  • Chris Coles March 21, 2008, 3:42 AM

    Glider pilots have for many years been using standing waves in the atmosphere as a means to flying great heights and distances. The hight record was broken recently taking it to something over 50,000 ft http://www.perlanproject.com/recent_news.php?date=2006-08-30 and distance is now 3,008 Kms in a single day flying these waves. They are very well known and documented and very well researched. But they are not described as gravity waves. It seems to me that people with no answers to why their gravity research has not produced any identifiable answers are now clutching at any straw in the wind. The correct title for these waves relates to their location and are either Lee Waves when in the lee of a mountain for example or they are called Frontal waves when they appear at the edge of a weather system.

  • HolyAvengerOne March 25, 2008, 5:35 PM

    Hmm the nomenclature of these are very confusing… but I think it does differ from other more traditionally understood phenomenon as they are actually maintained by Earth’s gravitational field…

    Ian ?

  • Chris March 27, 2008, 2:18 PM

    I think several readers skipped over this paragraph:

    “A large number of things may cause gravity waves (not to be confused with gravitational waves, the ripples in space-time), including intense disturbances caused by storm systems, a sudden change in jet stream location or wind shear. The strong oscillation will then travel for hundreds or even thousands of miles.”

  • holyavengerone March 28, 2008, 8:10 PM

    Chris, I didn’t skip it and I’m still confused with the nomenclature used here !

  • azorus April 1, 2009, 5:41 AM

    Has anyone thought to relate any of these waves to larger astronomical bodies, say the moon?

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