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  3. Many of the most damaging and life threatening types of weather torrential rains, severe thunderstorms, and tornadoes begin quic

Many of the most damaging and life threatening types of weather torrential rains, severe thunderstorms, and tornadoes begin quic

admin2010-01-26  53
问题     Many of the most damaging and life threatening types of weather torrential rains, severe thunderstorms, and tornadoes begin quickly, strike suddenly, and disappear rapidly, destroying small regions while leaving neighbouring areas untouched.  Such event as a tornado struck the northeastern section of Edmonton, Alberta, in July 1987. 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 study carefully the subtle atmospheric changes that come before these storms. In most nations, for example, weather- 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 forecasts, or "Nowcasts," was not feasible. The cost of equipping and operating many thousands of conventional weather stations was extremely high, and the difficulties involved in rapidly collecting and processing the raw weather data from such a network were hard to overcome.  Fortunately, scientific and technological advances have overcome most of these problems. Radar systems, automated weather 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 modem computers can quickly compile and analyze this large volume of weather information. Meteorologists and computer scientists now work together to design computer programs and video 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.
Conventional computer models of the atmosphere fails to predict such a short - lived tornado because______.
选项 A、the computer is not used to forecast specific local events
B、the computers are not advanced enough to predict it
C、the weather data people collect are often wrong
D、weather conditions in some small regions are not available
答案D
解析 第二段指出，“传统的计算机预测大气模式在预测像龙卷风这样的短期风暴方面并没有多大价值。因为可收集到的天气信息不够具体，所以计算机还没来得及研究微妙的天气变化，这样的暴风雨就已经来临了。”接着，文章以天气信息采集现状为例，指出“多数国家每隔几百英里才使用一次气象气球，每次间隔12小时。由于采集到的数据有限，传统的天气预报模式能够较好地预测大范围的总体天气情况而不是具体的局部天气事件。”所以选D。
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