Content provided by Tia Ghose, LiveScience
Gravity waves, mysterious waves that ripple unseen throughout the
atmosphere, may be a major source of airplane turbulence, a new study
suggests.
The new findings, presented Tuesday (Dec. 4) at the annual meeting of the American Geophysical Union,
may help explain why planes get shaky in apparently clear skies.
Forecasting those waves may allow planes to reroute around them.
"Just like waves on the ocean, as they approach a beach, they can
amplify and break. Gravity waves in the atmosphere can amplify and
break, and we're finding now that's a major contributor to turbulence in
the atmosphere that affects aircrafts."
form when air traveling up and down in the atmosphere meets resistance.
For instance, clouds rising in the troposphere, the lower level of the
atmosphere where air mixes freely, will bump up against the boundary of
the much more stable stratosphere, forming ripples in the process. These
waves can travel up to 180 miles (300 kilometers) before breaking, said
Robert Sharman, a meteorologist at the National Center for Atmospheric
Research (NCAR), who conducted the study.
"They're waves running around in the atmosphere all the time," Sharman told LiveScience.
Sharman and his colleagues wanted to understand when and where these
waves occur. They collected data from commercial aircraft flight
recorders, which record the location, duration and intensity of
turbulence.
Then they recreated these turbulent events using a computer simulation
that models the atmosphere. They found that gravity waves "break" on the
surfaces of planes, just like ocean waves breaking on the beach,
causing much of the turbulence that occurs out of the blue in clear air.
In the past, pilots thought airplanes moving up and down in the jet
stream caused such turbulence.
Many of the waves were formed in storm clouds that tracked the jet
stream, but traveled miles away and broke in areas where airplanes were
flying. Big mountains like the Colorado Rockies often form gravity waves as air flows over the mountains and then overshoots as it reaches the other side.
Luckily, gravity waves don't span a large height in the atmosphere, so it's pretty easy for airplanes to avoid such waves, Sharman said.
"They could either climb over it or go beneath it," he said.
The team is now using their simulations to forecast gravity waves
throughout the world. While the forecasts can predict the waves'
occurrence most of the time, they would need to reach about 85 percent
accuracy before pilots would use such predictions to avoid choppy air,
he said.
"Anytime they change course, it costs the airlines fuel. They have to
be pretty certain that that forecast is right before they'll make any
deviation," he said.
Copyright 2012 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
