[whataretheysaying] Mary Madigan: For all you storm chasers out there...

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Posted by Mary Madigan:
For all you storm chasers out there...
http://whataretheysaying.powerblogs.com/posts/1205965985.shtml


   New research by NASA-supported scientists shows how atmospheric
   gravity waves, the kind we often see rippling in clouds overhead, can
   hit a thunderstorm and turn it into a deadly tornado.

   [EMBED]

   Via [1]NASA*

     What is an atmospheric gravity wave? Coleman explains: "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 left his job as a TV weather anchor in Birmingham to work
     on his Ph.D. in Atmospheric Science at the University of Alabama in
     Huntsville. "I'm having fun," he says, but his smile and enthusiasm
     already gave that away.

     "You can see gravity waves everywhere," he continues. "When I drove
     in to work this morning, I saw some waves in the clouds. I even
     think about wave dynamics on the water when I go fishing now."

     Gravity waves get started when an impulse disturbs the atmosphere.
     An impulse could be, for instance, a wind shear, a thunderstorm
     updraft, or a sudden change in the jet stream. Gravity waves go
     billowing out from these disturbances like ripples around a rock
     thrown in a pond.

     When a gravity wave bears down on a rotating thunderstorm, it
     compresses the storm. This, in turn, causes the storm to spin
     faster. To understand why, Coleman describes an ice skater spinning
     with her arms held straight out. "Her spin increases when she pulls
     her arms inward." Ditto for spinning storms: When they are
     compressed by gravity waves, they spin faster to conserve angular
     momentum.

   [2]More...

   * Link thanks to Bruce

References

   1. http://science.nasa.gov/headlines/y2008/19mar_grits.htm?list1059711
   2. http://science.nasa.gov/headlines/y2008/19mar_grits.htm?list1059711