Observing Resources
Other excellent web resources for background on observing clouds include
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.
- Clouds come in three basic shapes:
- cumulus clouds (heaped and puffy)
- stratus clouds (layered)
- cirrus clouds (wispy)
- 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-"
- Low clouds (base below 2,000 m); no prefix
- Stratus
- Nimbostratus
- Cumulus
- Stratocumulus
- Cumulonimbus
- Fog is a cloud so low it touches the ground
- Clouds whose names incorporate the word "nimbus" or the prefix "nimbo-" are
clouds from which precipitation is falling.
- 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 [PDF] 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.
