Putting air turbulence into perspective.


New York (AirGuide - Inside Air Travel) It must have been a harrowing experience being on board the Air Canada plane flying between Shanghai and Toronto on New Year's Eve. The aircraft was forced to make an emergency landing after it hit some terrifying air turbulence over Alaska. Twenty-one passengers were taken to hospital, some after being thrown around the cabin like rag dolls. One passenger spoke of a sleeping girl "flying up" into the ceiling. It would only be human if, for those few minutes, a good number aboard the flight started to make their peace with God. But should air turbulence put the wind up flyers? According to Lauren Reid, aviation-business development manager at the Met Office in Britain, there are three main types of naturally occurring air turbulence that affect planes flying at altitude. The first, convective turbulence, is caused by localised thunderstorms. This is relatively easy for planes to avoid because the weather is visible, says Ms Reid. The most common is clear-air turbulence (CAT). This is caused by wind shear-streams of air travelling at different speeds or in different directions. This can jostle planes from side to side as well as up and down. The last, mountain-wave turbulence, is similar to wind shear, and occurs downstream from a mountain range. The terrain can sometimes cause the wind to oscillate, resulting mostly in up-down movement of the plane. As meteorologists have become better at predicting the likely location of bad turbulence, so relatively fewer passengers now experience it. The Met Office, which is one of two global centres providing forecast information for long-haul flights, says that over the past ten years its models, backed by greater computing power, have improved markedly. But, while planes have access to better information in order to avoid potential turbulence, the phenomena themselves may be becoming more common. Although there is no consensus amongst academics-"scientific papers go either way" says Ms Reid-some believe that global warming is making matters worse. A warming planet potentially means that jet streams are becoming more intense, increasing the likelihood of CAT. This is not a particular problem for the planes themselves. Aircraft are well-engineered and robust pieces of machinery. Even in the bumpiest conditions, wings do not shear off and fuselages do not get flipped upside down. Indeed those sudden, sickening drops, when you are sure you have plunged hundreds of feet,...

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