1. Water in the Atmosphere

2. H2O exists in atmosphere in all three states of matter…

3. Solid:
snow
hail
ice

4. rain and cloud droplets
Liquid:
rain and cloud droplets

5. Gas:
invisible H2O vapor

6. H2O may change from one state to another:

7. Melting:
from solid ice to liquid H2O

8. Freezing:
liquid H2O to solid ice

9. Evaporation:
from liquid H2O to H2O vapor

10. Condensation: from H2O vapor to liquid H2O

11. Sublimation: change from solid to H2O vapor
Example: Dry ice

12. Water vapor enters the atmosphere from the evaporation of water from oceans, lakes, marshes and glaciers

13. Dew point: the temperature at which water vapor condenses
Dew, clouds, and fog forms
If dew point is below freezing, frost will form

14. Warmer the air, the more H2O vapor it can hold
Humidity: water vapor in the air
Relative humidity: the % of moisture the air can hold relative to the amount it can hold at a certain temperature

15. Relative humidity=specific humidity X 100 capacity (saturated)

16. Psychrometer: instruments used to measure relative humidity
Works on principle that evaporation causes cooling
2 thermometers…wet-bulb and dry-bulb
Readings show how dry the air is

17. Clouds: simply high fogs, mist, or haze
Form when air above surface cools below dew point
Shape depends on air movement that forms it

18. -horizontal air movement = layers
-vertical air movement = piles

19. Temperature above freezing – clouds drop water
Temperature below freezing – clouds drop snow crystals

20. Precipitation: Water that falls from the atmosphere to the earth
Occurs when cloud droplets grow into drops heavy enough to fall to Earth

21. Acid precipitation: acid drops that fall to the ground
Acid precipitation: acid drops that fall to the ground - contain nitrate and sulfate particles that come from burning fuels, volcanoes and cars

23. Cloud seeding:
method to cause an increase
in precipitation

24. Condensation nuclei: suspended particles that provide the necessary surfaces for cloud forming condensation.