文档介绍：Part IV prehension (Reading in Depth) (25 minutes)
Section A
Directions: In this section, there is a short passage with 5 questions or plete statements. Read the passage carefully. Then answer the questions plete statements in the fewest possible words. Please write your answers on Answer Sheet 2.
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 neighboring 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.
puter 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 puters to study carefully the subtly atmospheric changes e 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 work were hard to e. Fortunately, scientific and technological advances have e 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