每天坚持背默
Beyond two or three days,the world’s best weather forecasts are speculative,and beyond six or seven days 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 rapidly.Errors and uncertainties multiply,cascading upward through a chain of turbulent features,from dust devils and squalls to a continent-size eddies that only satellites can see.
The modern weather models work with a grid of points of the order of sixty mails apart,and even so,some starting data has to be guessed,because ground stations and satellites cannot see everywhere.But suppose the earth could be covered with sensors spaced one foot apart,and rising at one-foot intervals all the way up to the top of the atmosphere.Suppose every sensor gives perfectly accurate readings of tempreture ,pressure and humidity,and any other quantitiy a meteorologist would want.Precisely at noon an infinitely powful computer takes （all the）data and caculate what will happen at each point at 12:01,then 12:02,then 12:03…
The computer will still be unable to predict whether Priceton （Princeton）,New Jersey,will be（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 diviations from the average.By 12:01,those fluctuations will have already created small errors one foot away.Soon the error will have multiplied to the ten-foot scale,and so on up to the （size of the）globe.
