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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.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 subtly 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 modern computers can quickly compile and analyze this large volume of weather information. Meteorologists(气象学者） 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.1.It can be inferred from the passage that the value of damages from torrential rains, severe thunderstorms and tornadoes is .2.Why do conventional models of the atmosphere fail to predict such a short-lived tornado?3.It can be inferred from the passage that conventional forecasting models are now mostly used for _.4.What does “Nowcasts”mean according to the passage?5.According to the passage, what makes “Nowcasting”a reality.

Researchers have established that when people are mentally engaged, biochemical changes occur in the brain that allow it to act more effectively in cognitive areas such as attention and memory. This is true regardless of age.People will be alert and receptive if they are faced with information that gets them to think about things they are interested in. And someone with a history of doing more rather than less will go into old age more cognitively sound than someone who has not had an active mind.Many experts are so convinced of the benefits of challenging the brain that they are putting the theory to work in their own lives. “The idea is not necessary to learn to memorize enormous amounts of information,”says James Fozard, associate director of the National Institute on Aging. “Most of us don’t need that kind of skill. Such specific training is of less interest than being able to maintain mental alertness.”Fozard and others say they challenge their brains with different mental skills, both because they enjoy them and because they are sure that their range of activities will help the way their brains work.Gene Cohen, acting director of the same institute, suggests that people in their old age should engage in mental and physical activities individually as well as in groups. Cohen says that we are frequently advised to keep physically active as we age, but older people need to keep mentally active as well. Those who do are more likely to maintain their intellectual abilities and to be generally happier and better adjusted. “The point is, you need to do both,”Cohen says, “Intellectual activity actually influences brain-cell health and size.”1.What is the passage mainly about?2.In what areas will the brain act more actively when people are mentally engaged?3.What kind of people are more cognitively healthy?4.According to Fozard’s view, how can people make their brains work more efficiently?5.What does Cohen advise older people to do?