Tutorial
5(b). Clouds
For basic identification purposes clouds are divided into four families: high
clouds, middle clouds, low clouds and vertically advanced clouds.
Low
Clouds
The low cloud family members are cumulus, fractocumulus,
stratocumulus, stratus, fog,
and fractostratus clouds. These clouds are nearly entirely composed of water,
and sometimes the water is supercooled. Low clouds at temperatures below freezing can also hold snow and ice particles.
The bases of these clouds are usually found near the surface to about 6,500 feet.
Middle Clouds The middle cloud family members are altocumulus,
and altostratus clouds. Lenticular clouds are often
typically included this family. Middle clouds are mainly composed of water, most of which is supercooled. The bases
of these clouds are usually found around 6,500 to 23,000 feet.
High
Clouds
The high cloud (cirriform) family includes cirrus, cirrocumulus,
and cirrostratus. They are made up almost entirely of ice crystals. The bases of
these clouds are usually found around 16,500 to 45,000 feet.
Vertically Advanced Clouds The vertically advanced cloud family members are nimbostratus,
towering cumulus and cumulonimbus clouds. These
clouds usually contain supercooled water above the freezing level. As a cumulus cloud grows to great heights, water
in the upper part of the cloud freezes into ice crystals forming a cumulonimbus. The bases of these vertically
advanced clouds range from 1,000 feet (or lower) to a towering 10,000 feet or higher.
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