1. 24.2 Clouds and Fog

2. OBJECTIVES List conditions that must exist for clouds to form
Identify Types of Clouds
Describe ways that fog may form

3. 24.2 Clouds and Fog
Clouds are a result of the condensation of water vapor throughout a large volume of air.
Which atmospheric layer are most clouds formed in?

4. 24.2 Clouds and Fog Clouds need a surface to form on.
These surfaces include tiny particles of dust and ice, called condensation nuclei.
troposphere

5. F/A 18 forces condensation out of the air approaching the speed of sound

6. 24.2 Clouds and Fog
For clouds to form, the air must be saturated with water vapor.
As the air gets cooler, it takes less water vapor to saturate the air.
There are usually more clouds on cooler days.

7. 24.2 Clouds and Fog
Convective cooling is the vertical circulation of air that occurs when air gets heated from below, by either the ground or ocean water, that has been heated by the sun.
Convection is a possible cause of winds. It causes a cooling of the air.

8. 24.2 Clouds and Fog
Changes in temperature that result directly from the expansion or compression of air are called adiabatic temperature changes.

9. 24.2 Clouds and Fog
The base or bottom of a cloud is found at a level called the condensation level because it is the level where the temperature change required for cloud formation ends.
LCL= lifting condensation level

10. 24.2 Clouds and Fog
Clouds usually surround areas of high elevation such as mountains because these objects force warm air upward.
This temperature change causes cloud formation.

11. 24.2 Clouds and Fog Advective cooling is another way clouds can form.
This is a process in which warm winds blow across cold oceans or cold areas of land.

12. 24.2 Clouds and Fog
Clouds are high fogs, mist, or haze that form when air above Earth’s surface cools below its dew point.
Three main cloud types:
Cirrus: thin feathery or tufted high ice-crystal clouds
Stratus: low sheets or layers, form in stable air (moving upward slowly)
Cumulus: thick fleecy masses formed by vertically rising air currents

13. Types of Clouds
Clouds are classified into a system that uses Latin words to describe the appearance of clouds as seen by an observer on the ground.
Latin Root Translation Example
cumulus heap cumulus
stratus layer altostratus cirrus curl of hair cirrus nimbus rain cumulonimbus
alto mid-level altocumulus

14. Types of Clouds

16. 24.2 Clouds and Fog
Stratus clouds are sheet like or layered clouds found close to the earth’s surface.

17. Stratus Clouds

18. Altostratus Clouds
This is an image of altostratus clouds. Notice the difference in thickness and color in the clouds.
Image courtesy of Keith G. Diem

19. Stratus Clouds
This image of stratus clouds was taken at sunrise in eastern Colorado. Stratus clouds usually cover the entire sky.
Image courtesy of Gregory Thompson

20. 24.2 Clouds and Fog
The term nimbo or nimbus means rain or snow, as in nimbostratus.
The term can be attributed to any type of cloud.
Pic of nimbostratus clouds

21. Nimbostratus Clouds
This image of nimbostratus clouds was taken in Seattle, WA. Notice the rain falling out of the clouds, as well as the rainbow!
Image courtesy of Peggy LeMone

22. 24.2 Clouds and Fog
Cumulus clouds are piled or heaped and are high topped clouds found at varying elevations.

23. Cumulus Clouds
Cumulus clouds are puffy white or light gray clouds that look like floating cotton balls. They have sharp outlines and a flat base.
Image courtesy of Carlye Calvin

24. Cumulus Clouds

25. Cumulonimbus clouds are clouds that are most commonly associated with rain.

26. Cumulonimbus Clouds
This cumulonimbus cloud is well-developed and shows the characteristic anvil-shape.
Image courtesy of Roberta Johnson

27. Cumulonimbus Clouds

28. 24.2 Clouds and Fog
Cirrus clouds are curly clouds that are found at altitudes above 6,000 meters.

29. Cirrus Clouds
Cirrus clouds are composed entirely of ice and consist of long, thin, wispy streamers. They are commonly known as "mare's tails" because of their appearance.
Image courtesy of Lisa Gardiner

30. Cirrus Clouds

31. Cirrus Clouds

32. 24.2 Clouds and Fog
Fog is a result of the condensation of water vapor in the air.
The temperature difference in the air and on the ground causes water vapor to condense and form fog.

33. Fog