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- 精华
- 2
- 积分
- 10815
- 天下威望
- 6946 点
- 天下币
- 23557 币
- 贡献
- 17416 点
- 勤奋度
- 191 点
- 维基指数
- 195 点
- 口译指数
- 27 点
- 阅读权限
- 255
    
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lesson 14
http://www.wwenglish.com/t/d/pinpai/nce/nce4/1979.htm
Beyond two or three days, the world’s best weather forecasts are speculative(投机的), and beyond six or seven they
are worthless.
The Butterfly Effect is the reason. For small pieces of weather—and to a global forecaster, small can mean
thunderstorms and blizzards – any prediction deteriorates(恶化) rapidly. Errors and uncertainties multiply(繁殖,增加), cascading(层叠)
upward through a chain of turbulent(狂暴的, 吵闹的) features, from dust devils(魔鬼) and squalls(尖声叫着)up to continent-size eddies(使起漩涡) that only
satellites can see.
The modern weather models work with a grid of points of the order of sixty miles apart, and even so, some
starting data has to be guessed, since ground stations and satellites cannot see everywhere. But suppose the
earth could be covered with sensors spaced one foot apart, rising at one-foot intervals all the way to the top of
the atmosphere. Suppose every sensor gives perfectly accurate readings of temperature, pressure, humidity(湿气,潮湿,湿度), and
any other quantity a meteorologist would want. Precisely at noon an infinitely powerful computer takes all the
data and calculates what will happen at each point at 12.01, then 12.02, then 12.03….
The computer will still be unable to predict whether Princeton, New Jersey, will have sun or rain on a day
one month away. At noon the spaces between the sensors will hide fluctuations that the computer will not
know about, tiny deviations(背离)from the average. By 1.201, those fluctuations will already have created small
errors one foot away. Soon the errors will have multiplied to the ten-foot scale, and so on up to the size of the
globe.
[ 本帖最后由 zf200424 于 2008-9-23 10:03 编辑 ]
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