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S'COOL: Observing Cloud Type

Observing Resources

	Print a 1-page cloud identification chart for S'COOL.
	Visit an on-line cloud chart with additional examples of each cloud type.
	View our cloud type tutorial
	Read Lin's tips for S'COOL Observers
	See more tips on cloud identification.
	See some cloud type schematics for further information.
	Try using a Dichotomous Key for Cloud Identification (developed by Dr. Tina Cartwright in West Virginia)
	Take a Cloud Quiz

Other excellent web resources for background on observing clouds include

• University of Illinois
• Plymouth State University
• Australian Severe Weather Group

Still not quite sure what kind of cloud that is? Read here for a discussion of how accurate you need to be.

Identifying and classifying clouds

The material below on identifying and classifying clouds is adapted from the workbook of the GLOBE Project.

Clouds are identified for S'COOL in twelve type classes. The names used for the clouds are based on three factors: their shape, the altitude at which they occur, and whether they are producing precipitation.

1. Clouds come in three basic shapes:
   • cumulus clouds (heaped and puffy)
   • stratus clouds (layered)
   • cirrus clouds (wispy)
2. Clouds occur in three altitude ranges (specifically, the altitude of the cloud base):
   • High clouds (base above 6,000 m); designated by "cirrus" or "cirro-"
     • Cirrus
     • Cirrocumulus
     • Cirrostratus
   • Middle clouds (base between 2,000 - 6,000 m); designated by "alto-"
     • Altocumulus
     • Altostratus
   • Low clouds (base below 2,000 m); no prefix
     • Stratus
     • Nimbostratus
     • Cumulus
     • Stratocumulus
     • Cumulonimbus
     • Fog is a cloud so low it touches the ground
3. Clouds whose names incorporate the word "nimbus" or the prefix "nimbo-" are clouds from which precipitation is falling.
4. Contrails are clouds formed around the small particles (aerosols) which are in aircraft exhaust. When these persist after the passage of the plane they are indeed clouds, and are of great interest to researchers. Under the right conditions, clouds initiated by passing aircraft can spread with time to cover the whole sky. The presence of contrails should be specifically flagged in your observations. A Fact Sheet on contrails is available from the US EPA.

NOTE: While both cumulus and cumulonimbus clouds may have their bases starting below 2,000 m, they often grow thick enough to extend into the middle or even high range. Thus, they are often referred to as "clouds of vertical development". Viewed from satellites, which see the top of clouds, these will generally be classified as mid- or high-level clouds. Finding such occurrences is one potential use of the S'COOL data.

S'COOL What to Observe Report Form Glossary