英语时差：飞机如何平稳飞行？（上）

Flying through turbulence in an airplane is usually something of a nuisance; when that fasten-your-seatbelts sign comes on, you know you’re in for a bumpy ride. On today’s Moment of Science, we’ll learn how airplanes use technology to avoid turbulence in the air ahead, and about systems that can help make flying a smoother, and safer, experience. Much turbulence is “convective turbulence,” and it’s the result of air motion associated with storm clouds. To help detect and avoid convective turbulence, airliners use radar, which sends a radio signal ahead of the airplane. If there are raindrops or ice in the air ahead, these radio signals bounce back, letting the pilot know where turbulence might be. A more sophisticated system uses the same radar to determine the motion of the rain and ice particles as well as their location.