Often unpredictable and increasing, what is turbulence?

Often unpredictable and increasing, what is turbulence?
Often unpredictable and increasing, what is turbulence?

It’s a phenomenon that often crystallizes fears when flying. Atmospheric turbulence, like that which caused the death of a passenger on a Singapore Airlines flight on Tuesday, is sometimes difficult to predict and is increasing with climate change.

According to experts, they are linked to a change in air currents affecting the stability of a flight. They can be caused by thunderstorms, air movements around mountains, cold or warm air fronts, or even jet streams – bands of strong winds circulating around the Earth.

“Unexpected turbulence may occur”

“Although meteorologists have excellent tools for forecasting turbulence, they are not perfect, and unexpected turbulence can occur,” said Thomas Guinn, a professor at Embry-Riddle Aeronautical University.

Concerning Tuesday’s dramatic flight, “the first elements seem to indicate clear air turbulence, the most dangerous type of turbulence”, according to the Association of Flight Attendants-CWA, representing several tens of thousands of flight attendants.

These are defined as “sudden and significant turbulence occurring in cloud-free areas and causing violent shaking of the aircraft”, specifies the American civil aviation regulator (FAA). They are “particularly problematic because they are often encountered unexpectedly and frequently without visual cues warning pilots.” This type of turbulence can particularly occur near jet streams and is commonly associated with a wind shear phenomenon (sudden changes in wind speed and/or direction).

Very rare deaths

Above all, according to a 2021 report from the US National Transportation Safety Board, turbulence continues to be “a significant cause of accidents and injuries”. However, “deaths linked to turbulence on commercial flights are fortunately very rare,” notes Paul Williams, professor of atmospheric sciences at the University of Reading. “There has not been a fatality linked to turbulence on a commercial flight since 2009.”

His research shows, on the other hand, that the climate crisis aggravates their frequency because it “increases the temperature difference between the cold poles and the hot tropics”. “This effect causes more shear in the jet stream, which generates more turbulence. » Severe “clear air” turbulence in the North Atlantic has already increased by 55% since 1979.

fasten your seatbelts

“Our latest projections are a doubling or even tripling of severe turbulence in jet streams in the coming decades, if the climate continues to warm as expected,” adds Paul Williams. For Thomas Guinn, airplane passengers should therefore keep their seat belts on board as much as possible because in this case “there is much less risk of accident. »

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