【英语时差8,16】飞机为什么会颠簸？

Airplane bumps are caused by regions of air moving at different speeds–for example, a layer of fast-moving windy air rubbing against a layer of relatively¹ still air. Where the two masses of air rub against each other, you get turbulence², a chaotic³ and unpredictable mixing of wind. This happens frequently near storm clouds, where a plume⁴ of warm air and clouds rises into cooler, upper layers. It can also happen above mountain ranges, when mountains deflect⁵ the surface wind upward, pushing dense⁶ air high into the thinner atmosphere. As a plane flies through the boundary layer of turbulence, it will encounter sudden, random⁷ changes in wind speed. A strong tailwind might turn into a strong headwind, or an updraft might suddenly turn downward. Because the airplane is immersed in this air, you experience these wind changes as bumps. Imagine driving a car along a perfectly⁸ smooth and flat highway, except the highway itself is moving unpredictably, lurching forward and backward, up and down. While mild turbulence is to be expected on many flights, severe turbulence, though rare, can cause injury or even death. On our next program, we’ll learn how turbulence can be predicted, and avoided.

1 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

2 turbulence   

n.喧嚣，狂暴，骚乱，湍流

参考例句：

• The turbulence caused the plane to turn over.空气的激流导致飞机翻转。
• The world advances amidst turbulence.世界在动荡中前进。

3 chaotic   

adj.混沌的，一片混乱的，一团糟的

参考例句：

• Things have been getting chaotic in the office recently.最近办公室的情况越来越乱了。
• The traffic in the city was chaotic.这城市的交通糟透了。

4 plume   

n.羽毛；v.整理羽毛，骚首弄姿，用羽毛装饰

参考例句：

• Her hat was adorned with a plume.她帽子上饰着羽毛。
• He does not plume himself on these achievements.他并不因这些成就而自夸。

5 deflect   

v.(使)偏斜，(使)偏离，(使)转向

参考例句：

• Never let a little problem deflect you.决不要因一点小问题就半途而废。
• They decided to deflect from the original plan.他们决定改变原计划。

6 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

7 random   

adj.随机的；任意的；n.偶然的(或随便的)行动

参考例句：

• The list is arranged in a random order.名单排列不分先后。
• On random inspection the meat was found to be bad.经抽查，发现肉变质了。

8 perfectly   

adv.完美地，无可非议地，彻底地

参考例句：

• The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
• Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。