1. H OW D OES T EMPERATURE A FFECT A IR M OVEMENT ? Lesson 2

2. A IR P RESSURE Why do your ears sometimes go shut when you ride in an elevator? What happens to your ears when you take off in an airplane?

3. The earth is surrounded by a layer of air. Air presses down on the earth and on YOU! AI R

4. The amount that air presses down or pushes on anything is air pressure.

5. As you go higher above the earth, the air temperature gets colder.

6. The higher you are above the earth’s surface, the less air there is pushing down on you. The air pressure is lower. Lower Temperature Lower Air Pressure Higher Temperature Higher Air Pressure

7. Air pressure on the earth’s surface also changes. Changes in temperature causes changes in air pressure.

8. H OW T EMPERATURE A FFECTS A IR

9. When air is warm, particles move farther apart. The air becomes lighter and rises. When warm air pushes down on the earth with less pressure it creates a low-pressure area.

10. Cold air is heavier. Particles are pushed closer together. Cold air sinks and pushes down on the earth’s surface with more pressure. It creates a high- pressure area.

11. When cool air sinks to the earth, it causes wind.

12. W IND

13. M EASURING A IR P RESSURE A barometer is a tool that measures air pressure.

14. B AROMETER One type of barometer is made of a hallow tube that is turned upside down in a plate of mercury.

15. B AROMETER Another type of barometer is a circular dial in a sealed box. The outside of the box moves slightly as air pressure changes. It is connected to a spring that moves a pointer on the dial.

16. B AROMETERS

17. M EASURING W IND S PEED AND D IRECTION Wind is invisible, but you can tell its direction by watching things move. What happens if you wet your finger and hold it up in the wind?

18. W IND V ANE A wind vane is a tool that shows wind direction. Wind vanes rotate on top of a pole. The tail swings away from the wind, and the arrow points into the wind. Wind vanes are one of the oldest weather tools.

19. W IND S OCK Wind socks are also used to show wind direction. They can also give a good idea of how fast the wind is blowing.

20. A NEMOMETER Anemometers are tools used to measure wind speed.

21. Wind moves the cups and the gears in the anemometer change the number of spins to wind speed.

22. M EASURING W IND

23. W EATHER T OOLS Air Pressure – Barometer Wind Direction – Wind Vane or Wind Sock Wind Speed - Anemometer