The plane is really getting more and more bumpy, it's not your illusion

Tech 2023-07-21 16:47:44 Source: Network

Image source: UnsplashThe sun was shining brightly and there were no clouds for a thousand miles. The plane rose to cruising altitude

Image source: Unsplash

The sun was shining brightly and there were no clouds for a thousand miles. The plane rose to cruising altitude. After the captain broadcast, the seat belt indicator light went out and passengers began to move back and forth in the cabin. However, suddenly, the plane shook. Out of instinct, you grabbed the armrest of the seat, while the passenger leaving the seat tried to maintain balance, and the baby began to cry.

After a minute, the turbulence stopped. You finally relax and take a deep breath. But the plane started againPlummet like a falling stoneYou feel like your stomach has been kicked into your throat - but strangely, there's no storm outside the window, and you can't even see the clouds. How could the plane still experience severe turbulence in such good weather?

Image source: Unsplash

This situation is calledClear sky turbulenceclear-air turbulence.Clear sky turbulence...

When these Jet stream belts are close to flight routes, airlines like to let aircraft fly in these airflow belts, so as to improve flight speed and shorten flight time. At the same time, if the airflow is not stable enough and forms turbulence, it will impact the aircraft wings. When the impact is strong enough, the plane will bump up and down. In the past 40 years,Clear sky turbulence55%.3060Clear sky turbulence100%~200%.Clear sky turbulence.

When turbulence appears in storms or clouds, pilots can relatively easily detect their presence. Airborne radar can track the dynamics of rainfall in the distance and reveal the movement of the air. Therefore, in this case, the pilot can notify passengers and crew in advance, reminding them to take their seats and fasten their seat belts before the turbulence occurs. However,Clear sky turbulence.Clear sky turbulence.

The turbulence of clouds is generated by the heating effect of the sun. At dawn, the sun begins to shine on the ground, heating the air near the surface. The heated air, due to its lower density than the cold air above, will rise upwards, while the previously cold air above will sink to a lower level. The air circulates and moves in this way, forming so-called convection currents. The convective motion of the atmosphere pushes the wings of an aircraft, and if encountering sudden strong convection, the thrust is greater, and the aircraft will experience turbulence.

Clear sky turbulenceOnly occurring in the rapids zoneMedium. The high-speed flow of air in a jet stream (imagine a rectangular duct) can generate shear forces on the slower flowing air above and below it, disrupting the stability of the upper and lower boundaries of the jet stream and making the boundaries no longer clear. At the same time, due to the Density contrast between the air in the jet stream zone and the air above and below, the boundary will tend to be stable again.

Most of the time, boundaries overcome unstable factors and return to a stable state, allowing people to enjoy a smooth journey. However, if Wind shear increases, instability will prevail, leading toAir turbulenceThe plane bounced up and down.

Image source: Unsplash

Through studying a large number of historical flight data and weather data, Paul Williams of the University of Reading and colleagues found that the frequency of turbulence in the North Atlantic jet belt increased by 17%~55% from 1979 to 2020. Among them,The most severe turbulence category(i.e. turbulence with a G-force greater than 1G) has the highest frequency increase. Under such acceleration, anything that is not fixed on the aircraft - including the human stomach - will float up temporarily, because turbulence causes the downward acceleration of the aircraft to exceed the Gravitational acceleration faster. In this case, the aircraft can quickly descend by several tens of meters, and if the seat belt is not fastened, passengers will detach from their seats.

How will this affect the flights we take? Firstly, severe turbulence occurs relatively infrequently. According to measurement data during flight, only about 0.1% of severe turbulence in the atmosphere occurs at the aircraft's flight altitude. "This means that the average flight time is 8 hours, and only about 30 seconds of severe turbulence can be encountered," explained Atmospheric science professor Williams. It is more likely that for every 10 flights taken, 9 will not encounter severe turbulence, while only 1 will experience a few minutes of turbulence.

..81015Clear sky turbulence.In the coming decades, this level of turbulence will double or even triple.

Author: Katherine Wright, Translator: Li Chengze, Editor: 27

Original link:

https://www.scientificamerican.com/article/yes-airline-flights-are-getting-bumpier-heres-why/

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