Cloud Names & Classifications | RMetS

Cloud names and cloud classifications

How are clouds classified?

RMetS Editor
26 February 2019

The system now used for classifying clouds is based on that originally proposed by pharmacist and amateur meteorologist Luke Howard in December 1802, in his paper "On the modification of clouds" ('modification' meaning 'classification').

In his paper Howard introduced three basic cloud classifications: 

  • Cirrus (meaning curl of hair)
    Cirrus clouds were described as "parallel, flexuous, or diverging fibres, extensible in any or all directions".
  • Cumulus (meaning heap)
    Howard defined cumulus clouds as "convex or conical heaps, increasing upward from a horizontal base".
  • Stratus (meaning something spread)
    Stratus clouds were classified as "a widely extended, continuous, horizontal sheet, increasing from below".

Howard then combined these names to form four more cloud types:

  • Cirrocumulus
    Cirrocumulus were described as "small, well-defined roundish masses, in close horizontal arrangement".
  • Cirrostratus
    Howard defined cirrostratus as "horizontal or slightly inclined masses, attenuated towards a part or the whole of their circumference, bent downward, or undulated, separate, or in groups consisting of small clouds having these characters".
  • Cumulostratus
    Cumulostratus was described by Howard as "the cirrostratus blended with the cumulus, and either appearing intermixed with the heaps of the latter, or super-adding a widespread structure to its base".
  • Cumulocirrostratus or Nimbus
    Howard called nimbus, or cumulocirrostratus, as "the rain cloud". He described it as "a horizontal sheet, above which the cirrus spreads, while the cumulus enters it laterally and from beneath".  

These form the basis of the cloud classification still in use today.

View "The story of how clouds for their names" here >