2014年4月托福考试模拟试卷及答案(第四套)_第5页

　　Many of the most damaging and life-threatening types of weather-torrential rains,　severe thunderstorms, and tornadoes--begin quickly, strike suddenly, and dissipate　rapidly, devastating small regions while leaving neighboring areas untouched. One　Line such event, a tornado, struck the northeastern section of Edmonton, Alberta, in July 1987.　(5) Total damages from the tornado exceeded $250 million, the highest ever for any　Canadian storm. Conventional computer models of the atmosphere have limited value　in predicting short-lived local storms like the Edmonton tornado, because the available　weather data are generally not detailed enough to allow computers to discern the subtle atmospheric changes that precede these storms. In most nations, for example, weather-(10) balloon observations are taken just once every twelve hours at locations typically　separated by hundreds of miles. With such limited data, conventional forecasting　models do a much better job predicting general weather conditions over large regions　than they do forecasting specific local events.

　　Until recently, the observation-intensive approach needed for accurate, very short-range　(15) forecasts, or "Nowcasts," was not feasible. The cost of equipping and operating  many thousands of conventional weather stations was prohibitively high, and the　difficulties involved in rapidly collecting and processing the raw weather data from　such a network were insurmountable. Fortunately, scientific and technological　advances have overcome most of these problems. Radar systems, automated weather　(20) instruments, and satellites are all capable of making detailed, nearly continuous　observation over large regions at a relatively low cost. Communications satellites can　transmit data around the world cheaply and instantaneously, and modern computers can　quickly compile and analyzing this large volume of weather information. Meteorologists　and computer scientists now work together to design computer programs and video　(25) equipment capable of transforming raw weather data into words, symbols, and vivid　graphic displays that forecasters can interpret easily and quickly. As meteorologists　have begun using these new technologies in weather forecasting offices, Nowcasting is　becoming a reality.

　　Which of the following would best illustrate Nowcasting?

　　(A) A five-day forecast

　　(B) A warning about a severe thunderstorm on the radio

　　(C) The average rainfall for each month

　　(D) A list of temperatures in major cities