1. Clouds Identify cloud types from photos
Recognize and define prefixes and suffixes for cloud types
Describe different fog types
Associate general weather conditions with cloud types

2. Clouds
Cloud Appreciation Society

3. Stratus

4. Cumulus

5. Cirrus

6. Cirrostratus

7. Cirrostratus

8. Cirrocumulus

9. Altostratus (and cirrus, higher)

10. Altostratus

11. Altocumulus

12. Stratocumulus

13. Nimbostratus

14. Cumulonimbus

16. Mammatus clouds

17. Three kinds of fog Radiation fog Advection fog Evaporation fog
Evaporation fog on the Kentucky River

18. Inland radiation fog

19. California; advection fog

20. Coastal California advection fog

21. Maine evaporation fog

22. Evaporation fog

23. Virga

24. Precipitation
Explain the collision coalescence process and the Bergeron process
Describe how aerosols and dust act as condesation nuclei or freezing nuclei
Explain how supersaturated atmospheric conditions develop
Describe how air pollution impacts cloud formation and precipitation
Explain the logic behind cloud seeding

25. Collision coalescence process
Water droplets collide and increase in size until large enough for gravity to pull them out of the cloud
Occurs in tropics and warmer midlatitudes
Precip leaves cloud as liquid water

26. Collision coalescence process requires presence of condensation nuclei
In clean air, RH must equal 120% for condensation to occur
Air would be considered supersaturated with water vapor
Presence of condensation nuclei allows condensation at 100% humidity

28. Bergeron process of precipitation formation
Also requires “dirty” atmosphere
Supercooled water (-40 degrees C) crystallizes upon contact with freezing nuclei
The air reaches saturation and some of the resulting droplets will come in contact with freezing nuclei (assuming they have reached the activation temperature). We will now have a combination of ice crystals and supercooled water droplets. From the perspective of the supercooled droplets, the air is in equilibrium at saturation, but from the perspective of the ice crystals, the air is supersaturated. Therefore, water vapor will sublimate on the ice crystals. Since the amount of water vapor in the air has decreased, and from the perspective of the supercooled water droplet, the air is subsaturated, the supercooled water will evaporate until the air once again reaches saturation. The process then continues. In short summary, the ice crystal grows through sublimation at the expense of the supercooled water droplet.

29. Bergeron process
Ice crystals form around freezing nuclei and grow through deposition
Precipitation leaves cloud as ice crystal
Occurs in midlatitudes to poles

32. Precipitation under Bergeron conditions
Rain – ice crystal melts and liquid water reaches surface
Sleet – warm layer melts ice but refreezes as “pellet”. Winter phenomena.
Snow – ice crystal falls to ground intact
Freezing rain – supercooled liquid water freezes at surface
Hail – summertime thunderstorm phenomena.

34. Jan 2013

36. Albedo greater in polluted atmosphere
More albedo in polluted air
Albedo greater in polluted atmosphere
Clouds last longer in polluted atmosphere