Thin, white patch, sheet or layer of cloud without shading, composed of very small elements in the form of grains, ripples, etc., merged or separate, and more or less regularly arranged; most of the elements have an apparent width of less than one degree.
MAIN DIFFERENCES BETWEEN CIRROCUMULUS AND SIMILAR CLOUDS OF OTHER GENERA
Cirrocumulus differs from Cirrus and Cirrostratus in that it is rippled or subdivided into very small cloudlets; it may include fibrous, silky or smooth portions which, however, do not collectively constitute its greater part.
Cirrocumulus differs from Altocumulus in that most of its elements are very small (by definition, of an apparent width less than one degree when observed at an angle of more than 30 degrees above the horizon) and without shading.
CLOUDS FROM WHICH CIRROCUMULUS MAY FORM
Cirrocumulus often forms as a result of the transformation of Cirrus or Cirrostratus (Cc cirromutatus and Cc cirrostratomutatus). Cirrocumulus may also form as the result of a decrease in size of the elements of a patch, sheet or layer of Altocumulus (Cc altocumulomutatus).
Cirrocumulus is composed almost exclusively of ice crystals; strongly supercooled water
droplets may occur but are usually rapidly replaced by ice A corona or irisation may sometimes be observed.
Cirrocumulus in the of lenses or almonds may be produced by local orographic lifting of a of moist air.
In middle and high latitudes, Cirrocumulus is usually associated, in space and time, with Cirrus or Cirrostratus or with both. In low latitudes, Cirrocumulus is less often accompanied by Cirrus or Cirrostratus.
A cloud should not be called Cirrocumulus if it consists of a patch of incompletely developed small elements such as those sometimes observed on the margin of a patch or sheet of Altocumulus or those sometimes present in separate patches at the same levels Altocumulus.
In case of doubt, a cloud should be given the name Cirrocumulus only when it has evolved or is obviously connected with Cirrus or Cirrostratus.