Cirrocumulus
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Cirrocumulus.jpg
A Cirrocumulus is a high-altitude cirriform cloud, occurring at 20,000-40,000 ft or 6000-12,000 m.
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Formation
Cirrocumulus is formed from cirrus or cirrostratus clouds when they are warmed gently from below. The heating process causes air to rise and sink inside the cloud. This is why cirrocumulus is almost always associated with cirrus and cirrostratus. If this is not the case, the cloud is then an altocumulus.
Appearance
Cirrocumulus is responsible for the nice "mackerel sky" feature.
Cirrocumulus and altocumulus sometimes look alike; however, unlike altocumulus, cirrocumulus is higher, therefore cirrocumulus cloudlets appear to be much smaller and the cloud provides no shadowing.
Cirrocumulus can show beautiful coronas and iridescence, especially if appearing under the cirriform lacunosus (net-like) structure.
Structural characteristics
The cloud is made of of thin, white patches (cloudlets), each of which composed of very small granules or ripples. Like all high-level clouds, cirrocumulus consists of ice crystals. These crystals can be vaporized, and gaps between cloudlets appear. The cloud usually presents 2 systems of undulation and fibrous margins.
Varieties of cirrocumulus
Castellanus is the formation that have tower-like protuberances in their superior parts, giving the cloud a crenellated appearance. The towers are from the same basis and arranged in line.
Flocus cloud has the appearance of a cumuliform cluster whose basis is more or less jagged.
Stratiformis formations are extensive horizontally, forming a vast horizontal layer.
Lenticularis formations are lens-like or almond-like, often allongated, with a well-defined circumference showed by an irisation.
External link
- National Science Digital Library - Cirrocumulus (http://www.nsdl.arm.gov/Library/glossary.shtml#Cirrocumulus)fr:Cirrocumulus