'Cloud Curls' Cloud Structure

He has a cloud in's face
William Shakespeare, The Tragedy of Antony and Cleopatra, Act III,|Scene II
Structure Description
Global Occurrence
Observation Diagrams

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"Convective Cells"
"Cloud Curls" Structure (CUS)

Cloud Structures tentatively called Cloud Curls occur rather seldom and mainly above circumpolar waters, most often above the waters situated close to the Antarctic.
Cloud Curls emerge within cloud fields from Stratus and/or Stratocumulus clouds. They usually appear in groups. The size of each curl varies from 40 to 80 km, rarely from 20-30 km to 120-140 km.
Quite often the Cloud Curls top is a little bit lower than the surrounding cloud field top, and the curls themselves have an outer border which is well marked and clearly seen.
An interesting peculiarity of this structure is that the top of the curls' center is often lower than the top of their bulk (forming some kind of a funnel-like relief) and has a greater albedo.
The types of cloudiness within cloud curls (according to the values resulted from the processed MERIS level 2 data) are usually Stratocumulus (on the rims) and Stratus (toward the centre of the structure).

The nature of the rise of such a structure is not clear.
It is possible to assume that the discrepancy in the temperature of the sea surface beneath the cloud cover may stipulate for the initiation of local winds. These winds interacting with the prevailing mesoscale wind and experiencing the Coriolis effect (the cloud curls twist in one and the same direction depending on the hemisphere, and there are no swirls less than 15-20 km in size), which becomes stronger as the cloud approaches the Poles, may form swirls.
The cold air is drawn out from upper atmosphere layers into these swirls, cooling them.
As the result the swirls go down compared with the surrounding cloud field. Cold heavy air that amasses in the center of the funnel cools the remaining clouds, besides the reduction of pressure leads to the rise of the ice-point, so that ice crystals appear (which is accompanied by the increase of their albedo), and pushes them more downward.

Global Occurrence Diagram
Global occurrence of 'Cloud Curls' Structure