1. Water in the Atmosphere Chapter 18

2. H 2 O exists in atmosphere in all three states of matter…

3. Solid: snow hail ice

4. Liquid: rain and cloud droplets

5. Gas: invisible H2OH2O vapor

6. H 2 O may change from one state to another:

7. Melting: from solid ice to liquid H 2 O

8. Freezing: liquid H 2 O to solid ice

9. Evaporation: from liquid H 2 O to H 2 O vapor

10. Condensation: from H 2 O vapor to liquid H 2 O

11. Sublimation: change from solid to H 2 O vapor Example: Dry ice

12. a measure of the energy in molecules the more energy the molecules have, the hotter it feels

13. isotherm: lines on a map that connect places that have the same temperature

14. thermometer: instrument that measures temperature alcohol and mercury thermometers used (mercury more accurate)

15. water freezes at: 0ºC or 32 ºF water boils at: 100ºC or 212ºF

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

17. Warmer the air, the more H 2 O 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

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

19. 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

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

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

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

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

24. Three main cloud types:

25. CIRRUS: - thin, feathery, made of ice crystals - form at high altitudes - seen when weather is fair, but can mean rain or snow

26. STRATUS Low sheets or layers; gray and smooth Block out the sun Associated with rain and drizzle

27. CUMULUS Piled in thick, puffy masses Formed by vertically rising air currents Usually mean fair weather

28. Other cloud types:

29. Cirrostratus

30. Stratocumulus

31. Cirrocumulus

32. Altocumulus

33. Nimbostratus

34. Cumulonimbus: large cloud that produce LIGHTNING, THUNDER, HEAVY SHOWERS = Thunderstorms

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

36. FORMS OF PRECIPITATION Drizzle: fine drops, very close together, fall slowly ….less than 0.5mm diameter Rain drops: larger, farther apart, fall faster… 0.5mm to 5mm diameter Snow: falls in clumps of six-sided crystals Sleet: pellets of ice tha fall to the ground when raindrops fall through freezing air

37. Hail: irregular balls or lumps made of layers of ice forms in cumulonimbus clouds-

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

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

41. Rain gauge: instrument used to measure the amount of rainfall

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