High above Earth, more than a hundred weather satellites (卫星) are collecting information. They send pictures of cloud patterns to scientists on Earth. They also take measurements (测量) of weather conditions, such as air temperature, air pollution and lightning strikes. The meteorologists study the pictures. They make mathematical models using the measurements. The models can help meteorologists make forecasts. The models forecast how, when and where the weather will change in a few hours or in several days. They might forecast (预测) rain in your area tomorrow. If so, you might decide to take your umbrella to school.
More important, weather forecasts tell when bad weather is on the way. Floods, tornadoes, thunderstorms, and hurricanes put people in danger. Weather forecast can save lives. For example, satellites pictures taken over time show how fast a hurricane is growing and the path it is taking. People can be ready for the storm. Meteorologists are always working to make better forecasts.
The United States began using weather satellites in 1960. Today's satellites take clearer pictures and collect more information. Satellites collect information about cloud systems. They have a bird's-eye view of smoke from wildfires and of ash clouds from volcanoes (火山). Weather satellites can also follow an oil spill on the ocean's flow. They can watch a cloud of sand blowing from a desert in Africa. Information from weather satellites is sent to supercomputers. These computers are huge, and they make mathematical models quickly.
Planes and ships need to know the weather so they can go around dangerous storms. A weather satellite can also help a ship in trouble. The satellite is part of a search and rescue (救援) system. The satellites can send a warning from the ship in danger to the U.S. Coast Guard. The Coast Guard can send out a rescue team.
