The air around Earth is called the atmosphere. It is about 97 kilometers (60 miles) thick. Scientists need instruments to study the atmosphere.

Temperature and Air Pressure

One tool is a thermometer. It tells the temperature, or how hot or cold something is. The first thermometer was made by Galileo Galilei in the 1590s.

About 50 years later, one of his students made a barometer. A barometer tells the air pressure. This is the weight of the atmosphere that presses down on Earth.

When the air pressure is high, the atmosphere is calm. The weather is good. When the air pressure is low, the atmosphere is stormy.

Weather Balloons

The atmosphere is very large. Parts of the atmosphere are very high up. It is very cold. The air is very thin.

Up there, scientists use other instruments. One is the weather balloon.

Weather balloons go high into the atmosphere. They carry a tool called a radiosonde. It records temperature, pressure, and how much water vapor is in the air. The radiosonde sends this information back to scientists. It happens in two seconds. This helps them forecast, or tell, the weather.

Satellites in Space

But a weather balloon can only go so high. Then it pops. Satellites can see Earth from higher up. Satellites fly in space around Earth. They take pictures and send them back.

Satellites monitor, or watch, many things. They track clouds, lightning, and hurricanes. They look for smoke and ash from wildfires and volcanoes. They take the temperature of the sea. They see how much snow and ice is melting. Satellites watch air pollution and greenhouse gases.

Radar and Computers

Radar is another tool to use. It tells what is happening in the atmosphere. It sends out radio waves. The waves bounce off rain and snow. This shows where the rain and snow are. Another kind of radar can tell where it is going. This is called Doppler radar.

Scientists who study the weather are called meteorologists. They use computer programs to predict the weather. These programs are called computer models. They tell what weather is happening now. They can also tell what might happen soon.