Cu compared with Ac/Sc

(Section 2.3.9.6.1)

Cumulus is distinguished from most Altocumulus and Stratocumulus by being detached and dome shaped. When viewed from a distance, Cumulus clouds may appear merged, owing to the effect of perspective. Care should be taken not to confuse distant Cumulus with Altocumulus or Stratocumulus.

Cumulus tops may:

• Spread and form Stratocumulus cumulogenitus or Altocumulus cumulogenitus
• Penetrate and pass through existing layers of Stratocumulus or Altocumulus
• Merge with Altostratus or Nimbostratus

The Cumulus clouds that are spreading, penetrating or merging continue to be identified as Cumulus as long as they remain detached from one another or they have relatively considerable vertical extent.