Have you ever been on a flight on a clear, blue day, and suddenly you experience turbulence? Many wonder why this happens since there is no cloud cover in sight to cause that bounce in the air. Well, now scientists have found the “invisible” culprit behind that turbulent air; gravity waves.
The phenomenon was explained more in detail at the annual meeting of the American Geophysical Union. "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 aircraft."
Gravity waves form when air travels up and down in the atmosphere, and hits something. For example, when clouds rise in the lower levels of the atmosphere air mixes freely, but eventually bumps into the more stable air in the upper atmosphere levels (typically 25,000ft. or higher), which forms ripples in the process. These ripples, or gravity waves, can travel up to 180 miles before finally coming to a stop.
"They're waves running around in the atmosphere all the time," explains Robert Sharman, a meteorologist at the National Center for Atmospheric Research (NCAR), who conducted the study.
Prior to this, scientists and pilots believed that airplanes moving up and down in the jet stream caused the turbulence. What they found instead was that gravity waves "break" on the surfaces of planes, just like ocean waves breaking on the beach or a large boat.
Mountains, such as the Rockies, often form gravity waves on their own as air flows over the mountains and then overshoots as it reaches the other side. Thankfully the gravity waves don't span a large height in the atmosphere, so it's pretty easy for airplanes to avoid them by either climbing over them, or going beneath them.
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