Clouds
Chapter 16, Section 1
Clouds
 Cloud
 Collection of millions of tiny water droplets or ice crystals
 Form when warm air rises
 Thinking Question
 How does the temperature of air change as it rises?
 How does this affect the relative humidity of the air?
Forming Clouds
1.
As air rises, it cools.

Air becomes saturated
• lower temp = less water vapor air can hold
2.
Water vapor in air condenses

Above freezing = liquid droplets

Below freezing = ice crystals
3.
Vapor must have surface to condense on

Dust, smoke, salt, etc
Types of Clouds
 Three main types of clouds
 Cumulus
 Stratus
 Cirrus
Cumulus
 Puffy clouds
 Flat bottoms
 Form during fair weather
 BUT produce thunderstorms when larger
 Cumulonimbus cloud
• Nimbus: indicates precipitation might fall
Stratus
 Clouds form in layers
 Low altitudes
 Cover sky - often block sun
 Nimbostratus clouds: produce steady rain
 Fog: stratus cloud formed when water vapor condenses close to ground
Cirrus
 Thin, feathery white clouds
 Middle high altitudes
 Form in strong winds
 Indicate bad weather when they lower in altitude
Cloud Classification
 Classified by altitude at formation
 Cirrus: high clouds
 Alto: describes middle clouds
 Strato: low clouds