Description Cumulus and differences with similar clouds | Previous Top Next

Cumulus
Detached clouds, generally dense and with sharp outlines, developing vertically in the form of rising mounds, domes or towers, of which the bulging upper part often resembles a cauliflower. The sunlit parts of these clouds are mostly brilliant white; their base is relatively dark and nearly horizontal. Sometimes Cumulus is ragged.
Main differences between Cumulus and similar clouds of other genera
(a) Altocumulus and Stratocumulus
Small Cumulus clouds may be so numerous and crowded that they resemble a layer of Stratocumulus or Altocumulus, especially when observed near the horizon. The clouds should be identified as Cumulus so long as their tops remain dome-shaped and their bases are not merged.
(b) Altostratus and Nimbostratus
When a very large precipitating Cumulus cloud is directly above the observer, it may be confused with Altostratus or Nimbostratus. The character of the precipitation may help in distinguishing Cumulus from the latter clouds; if the precipitation is of the showery type, the cloud is Cumulus.
(c) Cumulonimbus
Since Cumulonimbus generally results from the development and transformation of Cumulus, it is sometimes difficult to distinguish Cumulus with a great vertical extent from Cumulonimbus. The cloud should be named Cumulus as long as the sprouting upper parts are everywhere sharply defined and no fibrous or striated texture is apparent. If it is not possible to decide on the basis of other criteria whether a cloud is to be named Cumulus or Cumulonimbus, it should by convention be called Cumulus if it is not accompanied by Lightning, Thunder or Hail.
(d) Ragged Stratus
Ragged Cumulus is distinguished from ragged Stratus by its generally greater vertical extent and its usually whiter and less transparent appearance. Ragged Cumulus, furthermore, sometimes has rounded or dome-shaped tops, which are always lacking in ragged Stratus.