1. Clouds

2. Cloud formation Large mass of air rises, cools to dew point
Condensation (or deposition) occurs on condensation nuclei
salt, dust, soil, pollutants

3. elevation at which air becomes saturated is lifting condensation level (flat base of clouds)

7. A cloud is a mass of suspended water, supercooled water and/or ice particles.
particles micrometers
Water is supercooled : liquid below freezing

8. < -40oC (-40°F): all ice crystals
< -20oC: predominantly ice crystals
-12o to -20o C: mixture of ice and supercooled water
> -12oC (10°F):
all water

9. Cloud classification (according to shape and altitude)
Shape Classes:
Flat: stratiform
Globular: cumuliform

10. Altitude Families: High Cloud (cirro-): ice crystal clouds
> 6000 m (20,000 ft.)
CIRRUS, CIRROSTRATUS, CIRROCUMULUS

11. cirrus

12. cirrus

14. Cirrostratus (halo around sun or moon)

16. cirrostratus

17. cirrocumulus

19. Altitude Classes: Middle Cloud (alto-)
3000 – 6000 m (10, ,000 ft.)
ALTOSTRATUS, ALTOCUMULUS

20. altostratus

21. altostratus

22. altostratus

23. altocumulus

24. altocumulus

25. altocumulus

26. altocumulus

27. Altitude Classes: Low Cloud (stratus) <3000 m (10,000 ft)
STRATUS, NIMBOSTRATUS, STRATOCUMULUS

28. stratus

29. stratus

31. stratus

32. nimbostratus

33. stratocumulus

34. stratocumulus

35. stratocumulus

36. Altitude Classes:
Vertically developed clouds (CUMULONIMBUS)

37. Vertically Developed Clouds: cumulonimbus

38. cumulonimbus

39. cumulonimbus

40. cumulonimbus

41. mammatus

43. lenticular
Strong wind flow over rugged terrain
often stacked

49. Cumulonimbus pileus

50. Cumulus fractus (small, ragged)

51. Cumulus humilis (smaller vertical extent)

55. Altocumulus translucidus

56. Altostratus translucidus

57. Altocumulus undulatus

58. contrails

59. contrails