Fog is often described as a cloud that forms at ground level. In ...

[tingc95]

Fog is often described as a cloud that forms at ground level. In what ways are the formation of fog and clouds similar and different?
  What will be an ideal response?

Question 2

List the major height categories of clouds. What differences might you expect to find in clouds that form at these different levels?
  What will be an ideal response?

[fur]

Answer to Question 1

ANSWER: Fog and clouds form in the same way, either by: (1) coolingair is cooled below its saturation point (dew point) or (2) evaporation and mixingwater vapor is added to the air by evaporation and moist air mixes with relatively dry air. Once fog forms it is maintained by new fog droplets, which constantly form on available nuclei. In other words, the air must maintain its degree of saturation either by continual cooling or by evaporation and mixing of vapor into the air. The differences between fog and clouds are that fog is a very local event and is found near the surface, whereas clouds form at considerable elevation and can be widespread.

Answer to Question 2

ANSWER: High clouds in middle and low latitudes generally form above 5000 m (16,000 ft). Because the air at these elevations is quite cold and dry, high clouds are composed almost exclusively of ice crystals and are also rather thin. High clouds usually appear white, except near sunrise and sunset, when the unscattered (red, orange, and yellow) components of sunlight are reflected from the underside of the clouds.

Middle clouds have bases between 2000 and 7000 m (6500 to 23,000 ft) in the middle latitudes. These clouds are composed of water droplets and when the temperature becomes low enough some ice crystals. Precipitation can form in middle clouds if they become thick enough.

Low clouds, with their bases lying below 2000 m (6500 ft), are almost always composed of water droplets; however, in cold weather, they may contain ice particles.

[tingc95]

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