1. Chapter 16 Water in our atmosphere

2. Humidity Is a measure of how much water vapor is in the air. It is measured in a percent using a psychrometer . More humidity means more clouds and more likely chance of precipitation.

3. Dew point is the temperature when water vapor condenses to a solid or liquid This forms clouds!

4. http://www.wildlandschool.net Clouds form when the water vapor reaches the dew point. Remember that as you go up in the troposphere, the temperature decreases. Dew point

5. This is the reason clouds look to be about the same height in the sky and flat on the bottom. They are! Dew point temperature is reached .

6. If the dew point temperature is the same as the air temperature on the ground, fog forms! The cloud actually forms on the ground.

7. Precipitation Any form of H 2 O that falls from clouds and reaches the earth's surface.

8. The term rain is restricted to drops of water that fall from a cloud and have a diameter of at least 0.5 millimeter . Drizzle and mist have smaller droplets . The most common form of precipitation is rain.

9. Drizzle droplet raindrop Mist droplet Cloud droplet Droplets come in many sizes

10. As water vapor collects into larger and larger droplets, gravity will cause them to fall to the ground as rain, sleet, hail, or snow.

11. Clouds Form when water vapor condenses to form drops of liquid water or ice crystals. There are three main types of clouds.

12. Cirrus – high, thin, feathery clouds Made of ice crystals

13. Cirrus – highest type of cloud. Due to elevation, made of ice crystals. They indicate that a change in the weather is coming.

14. Cumulus – round, puffy clouds Indicate fair weather

15. They can build up to form storm clouds that contain hail, lightning, and tornadoes.

16. Cumulonimbus clouds often produce bad weather (lightning and hail) Nimbus/nimbo means rain . Notice that it is getting flat on the top. That means the top of the cloud has reached the top of the troposphere and cannot go any higher. http://www.colby.edu/

17. Cumulonimbus

18. Stratus – flat layer of clouds. Often have rain.

19. Nimbostratus clouds often produce rain for many hours. Like stratus clouds, they cover the sky. The only difference is that these are producing rain or snow.

20. Other cloud types

21. Any questions?