E Wouldn’t it be great if you could just look up at the sky and read the weather forecast right away? Well, you can. The forecast is written in clouds. If you can read that writing, you can tell something about the atmosphere. With some practice, you can become a pretty good weather forecaster. Who knows, you might even do as well as meteorologists. Meteorologists use much more information than just the appearance of the clouds to make their forecasts. They collect data from all over the world. Then they put it into powerful, high-speed computers. This does give meteorologists an advantage, because they can track weather patterns as they move from west to east across the country. But you have an advantage, too. You can look at the sky and get your data directly. A meteorologist uses a computer forecast that takes several hours to make a local forecast. What are you seeing when you look at a cloud? “A picture of what moisture is doing in the atmosphere,” says meteorologist Peter Leavitt. There’s moisture throughout the atmosphere. Most of the time you don’t see it ,because it’s in the form of an unseen gas called water vapor. Sometimes, the temperature of the air gets cold enough to cause the water vapor to change into liquid water. That’s called condensation, and we see it happen all the time(for example, when damp air hits the cold glass of a mirror). When enough water vapor condenses, tiny drops form in the air. These drops spread light. A cloud is seen. Watching clouds over a day or two tells you a lot more than a single cloud about the weather to come. Changes in clouds show changes in the atmosphere. You should begin to notice patterns. Certain clouds, following each other in order, can signal a coming storm. But don’t take our word for it; see for yourself. 57．This passage mainly tells us about how to_______. A．become a meteorologist B．keep an eye on the weather C．be an assistant to a meteorologist D．change water vapor into liquid water 58．According to the passage, ordinary people might do as well as meteorologists in weather forecast________. A．with the help of the high-speed computers B．through a complex process of calculation C．with simple practice looking up at the sky D．asking for information from weather station 59．Your advantage in weather forecasts is that______. A．you have more powerful computers at home B．your brain works as well as a high-speed computer C．you observe the sky and obtain your data directly D．meteorologists give their data to you as soon as they get them 60．What causes vapor to change into water? A．A lot of moisture. B．Thick clouds. C．Warm atmosphere. D．Cold air temperature. |