Why flights are getting bumpier

“What an airplane experiences when it’s bumping around is actually small wind fluctuations that cause the airplane to go up and down,” Lane said.

“It’s not changes in the horizontal wind, it’s updrafts and downdrafts that push the plane up and down, creating a ‘bump’.

“The eddy dissipation rate measures the energy of these small wind fluctuations.”

EDR data is collected from various types of aircraft, including commercial aircraft.

What causes turbulence?

Thunderstorms are a common but easily avoidable source of turbulence because they can be seen by pilots through windshields and on flight radar.

Lane said the Sydney-Brisbane route is likely to have secured first place due to the high number of La Niña thunderstorms in recent years (2022 was Sydney’s wettest year on record and Brisbane recorded nearly double its annual precipitation).

“If I were to speculate, I’d say it’s probably related to the storms. Both Sydney and Brisbane are experiencing fairly severe thunderstorms,” ​​Lane said.

He’s currently studying thunderstorm turbulence and said storm cells can create clear air turbulence far away by creating “ripples” throughout the atmosphere.

“A thunderstorm creates these waves in the wind that spread away from the storms into the clear air. These waves are invisible and are waves, just like waves in the ocean. When these waves break, they can create turbulence at least 100 kilometers from the storm.”

Retired pilot Ali Al-Wahabi knows this well. In his 45-year career, he flew international commercial aircraft around the world. His most memorable bout of turbulence occurred while entering Hong Kong’s infamous Kai Tak Airport.

“[The turbulence] was very, very severe,” said Al-Wahabi, now head of ground theory at Sydney Flight College. “In the end, after four tries, we managed to get it on the ground. It was caused by a typhoon brewing 150 kilometers from Hong Kong.”

Another important source of turbulence is jet streams, flows of fast winds at the top of the troposphere (the first layer of the atmosphere, averaging about 12 kilometers high). They are formed by rising warm air from the tropics meeting cool polar air, and the winds are pushed east by Earth’s centrifugal force.

Eastbound planes using these streams can shave several hours off flight time. But at the edge of jet streams there is a lot of wind shear and turbulence. (As one pilot put it, imagine the churning edges of a fast-moving river as the water swirls against the riverbank.)

The wind in jet streams can reach 400 kilometers per hour. Increasing temperature gradients between the equator and the poles at the altitude where jet streams flow have destabilized wind flows and increased vertical wind shear, resulting in clearer air turbulence.

Mountains and islands also disrupt wind flow and can create oscillating waves in the atmosphere that cause turbulence. Rising hot air parcels can also shake aircraft through so-called convective turbulence.

Can we do something about the increasing turbulence?

The latest study on the impact of climate change on turbulence found that the annual duration of mild turbulence has increased from 466.5 to 546.8 hours, a 17 percent increase since 1979. Moderate turbulence increased 37 percent and severe turbulence 55 percent, although that is from a low base – it rose from 17.7 hours to 27.4 hours.

When pilots encounter a difficult spot, they slow the plane to the “turbulent air penetration speed,” a speed halfway between an airplane’s maximum and minimum speeds, Al-Wahabi said.

“You don’t want top speed to be reached as that could affect the structure of the aircraft. And they don’t want you to get into the low end of flyable speed, as that will get you closer to the plane’s stall speed. So the next [middle speed] will give you a very comfortable pillow.”

Airplanes are built to withstand loads far greater than they are likely to ever experience during decades of flight. A pilot’s primary concern is usually the passengers and crew frolicking behind them – turbulence is the leading cause of in-flight injuries from unbelted passengers and falling luggage.

Turbulence alone cannot break up planes or cause them to crash. However, damage to the interior cabin can occur and increase wear and tear on the aircraft, requiring more frequent repairs. The damage and delays caused by turbulence cost the US airline industry between $150 million and $500 million annually.

Sitting in the middle of the plane over the wings increases your chances of a smoother flight (the rear end of the cabin handles the worst of the bumps). Al-Wahabi said flights are generally quieter earlier in the morning and late in the evening when the heat of the day isn’t a factor causing additional bustle.

While clear air turbulence is difficult to predict and avoid (usually not detected until someone flies through it and alerts other pilots), Lane expects our detection capabilities to improve in the years to come.

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“I would suspect that improving forecasts and turbulence avoidance techniques will actually be faster and more effective than any changes in turbulence,” Lane said.

“If anything, even as atmospheric turbulence increases, we will experience less turbulence on airplanes in the coming decades due to improved avoidance methods.”

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