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Airplane turbulence? Blame gravity waves.

Posted by Kevin Hartnett  January 2, 2013 05:46 AM

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Thumbnail image for gravity waves.jpegFrom a window seat in coach it often seems like turbulence strikes for no reason. You’re flying through cloudless skies when suddenly the plane shakes and the seatbelt light dings on. It would be nice to think that at least the pilots saw the rough air coming, but often they’re caught by surprise, too.

But that may be about to change. A recent study by the National Center for Atmospheric Research (NCAR) proposes a new explanation for why turbulence crops up. It owes to something called atmospheric “gravity waves.”

Even if you've never heard of gravity waves, you’ve definitely seen them in action. Think of the ripples created when a rock is dropped into a pond: The force of the dropped rock propels the water upwards while gravity pulls the disturbed water back towards its equilibrium state. Or consider waves at the beach: They’re gravity waves, too, produced when the wind whips up the ocean surface and gravity pulls the water back down.

The same principle applies in the earth’s atmosphere. Robert Sharman, author of the NCAR study, explains that atmospheric gravity waves occur when air moving up and down through the atmosphere hits resistance. For example, clouds rise from the troposphere into the more stable air of the stratosphere and the collision, as it were, sends out waves of air around the clouds. Sometimes those waves peter into nothingness and sometimes they run into airplanes, breaking on the body of a 747 the same way ocean waves break when they hit the shore: turbulence happens and you spill your Diet Coke.

Sharman and his team are currently analyzing turbulence data from airplane flight recorders in order to build a model for forecasting gravity waves. If their model gets good enough, pilots will be able to steer around choppy air and you’ll find yourself with more time to move around the cabin.

(As a last point, I was initially confused by the term gravity waves. I assumed it referred to an Einsteinian spacetime phenomenon when it really describes an instance of plain old Newtonian mechanics at work. A little Googling reveals that what I had in mind are called gravitational waves as opposed to gravity waves and it turns out researchers are making progress on that front as well: A team of Princeton astrophysicists recently announced that gravitational waves—which are caused by mega-collisions of space bodies like neutron stars or black holes—are probably a lot more common than we (they) have thought.)

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About brainiac Brainiac is the daily blog of the Globe's Sunday Ideas section, covering news and delights from the worlds of art, science, literature, history, design, and more. You can follow us on Twitter @GlobeIdeas.
Brainiac blogger Kevin Hartnett is a writer in Columbia, South Carolina. He can be reached here.

Leon Neyfakh is the staff writer for Ideas. Amanda Katz is the deputy Ideas editor. Stephen Heuser is the Ideas editor.

Guest blogger Simon Waxman is Managing Editor of Boston Review and has written for WBUR, Alternet, McSweeney's, Jacobin, and others.

Guest blogger Elizabeth Manus is a writer living in New York City. She has been a book review editor at the Boston Phoenix, and a columnist for The New York Observer and Metro.

Guest blogger Sarah Laskow is a freelance writer and editor in New York City. She edits Smithsonian's SmartNews blog and has contributed to Salon, Good, The American Prospect, Bloomberg News, and other publications.

Guest blogger Joshua Glenn is a Boston-based writer, publisher, and freelance semiotician. He was the original Brainiac blogger, and is currently editor of the blog HiLobrow, publisher of a series of Radium Age science fiction novels, and co-author/co-editor of several books, including the story collection "Significant Objects" and the kids' field guide to life "Unbored."

Guest blogger Ruth Graham is a freelance journalist in New Hampshire, and a frequent Ideas contributor. She is a former features editor for the New York Sun, and has written for publications including Slate and the Wall Street Journal.

Joshua Rothman is a graduate student and Teaching Fellow in the Harvard English department, and an Instructor in Public Policy at the Harvard Kennedy School of Government. He teaches novels and political writing.


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