Predicting the bump

A forecasting method could help pilots chart new courses around patches of rough but clear air that can cause the sudden bumpiness and violent plummeting of aircraft.

Commercial aircraft encounter severe turbulence about 5,000 times each year, and the majority of these occur 10,000ft above the Earth's surface. The new method gives pilots a way to avoid turbulence that is not associated with nearby thunderstorms or significant cloudiness.

To do so, it predicts energy associated with gravity waves - phenomena in the atmosphere that look like ocean waves but which can occur in clear air.

They can be created by air flow over mountains, frontal boundaries or other causes and result in what's known as Clear Air Turbulence (CAT).

But the type of gravity wave that John Knox, an assistant professor in the department of geography at the University of Georgia's Franklin College of Arts and Sciences identified as a possible source of bumpiness comes from a different source - they are spontaneously generated and associated with jet streams at high altitudes, near cruising levels for aeroplanes.