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Description Cirrostratus and differences with similar clouds
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Cirrostratus
Transparent, whitish cloud veil of fibrous (hairlike) or smooth appearance, totally or partly
covering the sky, and generally producing Halo phenomena.
Main differences between Cirrostratus and similar clouds of other genera
Cirrostratus is distinguished from Cirrus by the fact that it occurs in the form of a veil which is
usually of great horizontal extent.
Cirrostratus has a diffuse general aspect and does not exhibit such features as grains, ripples,
laminae, rounded masses, rolls, etc., which are characteristic of Cirrocumulus and
Altocumulus.
Cirrostratus differs from Altostratus by its thinness and by the fact that it may show Halo
phenomena. Cirrostratus near the horizon may he mistaken for Altostratus. The slowness of
the apparent movement and the slowness of the variations in thickness and in appearance,
both characteristic of Cirrostratus, give useful guidance in distinguishing this cloud from
Altostratus and also from Stratus.
Cirrostratus may he confused with very thin Stratus which, at angular distances of less than 45
degrees from the sun, may appear very white. Cirrostratus differs, however, from Stratus by
being whitish throughout, and by the fact that it may have a fibrous appearance. Moreover
Cirrostratus often displays Halo phenomena, whereas Stratus does not, except occasionally at
very low temperatures.
Cirrostratus differs from a veil of haze by the fact that the latter is opalescent or has a dirty
yellowish to brownish colour. It is sometimes difficult to discern Cirrostratus through haze.