1. MOISTURE, CLOUDS & PRECIPITATION Chapter 18 * REMINDER - water vapor is the source of all precipitation. Water’s Changes of State 1) Melting- solid to liquid Freezing- liquid to solid Freezing- liquid to solid 2) Evaporation- liquid to gas Condensation- gas to liquid Condensation- gas to liquid 3) Sublimation- solid to gas Deposition- gas to solid Deposition- gas to solid

2. Changes of State

3. Humidity - amount of water vapor in the air * saturation- total amount of water vapor air can hold Expressed 2 ways: 1) Relative Humidity - indicates how near air is to saturation 2) Dew Point - temp. needed to reach saturation

4. Dew on a Spider Web

5. Notes on Humidity - Hygrometer- device used to measure humidity and dew point. and dew point. - warm air holds more water than cold air - decrease temp = increase humidity - increase temp = decrease humidity

6. ?What Happens to Air When it is Compressed or Expanded? Answer:Expanded air cools Compressed air warms Example: Increased Height = Air expansion = Cooling Decreased Height = Air compression = Warming

7. Processes the Lift Air 1) Orographic Lifting - air that lifts over mountains

8. 2) Frontal Wedging - warm air rises over cold air

9. 3) Convergence - air from opposite directions collide and rise

10. 4) Convective Lifting - unequal heating of land causes air to rise

11. CLOUDS FORM WHEN: 1) Saturated air cools to the dew point 2) Matter is present for water to condense on - condensation nuclei -

12. Cloud Types - based on shape and height Forms (shape) 1) Cirrus - high, white, thin clouds

13. 2) Cumulus - round, thick clouds that rise up

14. 3) Stratus - sheets or layers of clouds

15. Types 1) High Clouds - forms above 6000 meters - mostly made of ice crystals 2) Middle Clouds - forms between 2000-6000 meters 3) Low Clouds - forms below 2000 meters - can produce precipitation & storms Fog- cloud formed near Earth’s surface Fog- cloud formed near Earth’s surface - forms by cooling of air on clear nights - forms by cooling of air on clear nights

16. Precipitation Forms 2 ways: 1) Water droplets freeze, become heavy & fall. - as frozen drops fall, they melt, unless the lower air is below freezing. the lower air is below freezing. 2) Water droplets form together, becoming large enough to fall. large enough to fall.Types Rain, snow, sleet, hail, freezing rain.