Altocumulus stratiformis

Altocumulus stratiformis is the most common species of the Altocumulus genus of clouds.[1] They tend to form broad layers of individual, cell-like clumps, often separated from each other, though they sometimes can coagulate into a larger individual cloud. They often have a vertical extent of less than 500 m.[2] Due to their formation dynamics, they are commonly associated with the imminent arrival of precipitation.

Altocumulus stratiformis
Altocumulus stratiformis over Germany in 2011
AbbreviationAc str
GenusAltocumulus (high, heaped)
Speciesstratiformis
Variety
  • perlucidus
  • undulatus
Altitude2,000 - 6,000 m
(6,500 - 20,000 ft)
ClassificationFamily B (Medium-level)
AppearancePatchy and shallow; often semi-transparent.
Precipitation cloud?Uncommon

Formation

The presence of stratiformis clouds in the mid-levels of the atmosphere is indicative of some instability at that level;[3] atmospheric pressure falls, often associated with nearby systems of low pressure, can depress the altitude of stratiformis into the lower atmosphere, often evolving into Nimbostratus clouds, which precipitate. [4] Altocumulus stratiformis clouds may also form when a cold front is approaching, due to the difference in air masses.

References
  1. "Altocumulus stratiformis (Ac str)". International Cloud Atlas.
  2. "Altocumulus Stratiformis Clouds - EPOD - a service of USRA". epod.usra.edu.
  3. "Altocumulus clouds". Met Office.
  4. "Nimbostratus Clouds: dark, low-level clouds with precipitation". ww2010.atmos.uiuc.edu.


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