Weather+Instruments

= __ Using Instruments to Study the Weather __ = ==Studying and predicting weather is called METEOROLOGY. Knowing what weather is on the way is important to people. For instance, farmers will not plant crops if they are expecting frost or heavy rain. And everyone wants to know what to wear so they will be comfortable during the day. ==   In the past, people have used signs in nature, such as the color of the sky at certain times of the day, to predict weather. Today, we use many different instruments to tell us about weather conditions. == A //weather vane// shows wind direction. It has a moving arrow which points in the direction from which the wind is coming. It also has a fixed base marked with the cardinal directions. ==

== An // anemometer // measures wind speed. The cups catch the wind and make the center spin. The number of times it rotates every minute gives the wind speed. ==  

When air presses down on the metal box, a series of springs and levers move the needle . [[image:p55_aneroid.jpg width="495" height="331"]]
== **//Thermometers//** measure air temperature. As this changes, the liquid inside the tube expands or contracts. Expanding liquid moves up the tube and contracting liquid moves down. ==