International Cloud Atlas
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Coding instructions CL

(Section 2.8.3.1)
  1. If at least a part of one Cumulonimbus present is of the species capillatus, the coding is CL = 9
  2. If a Cumulonimbus has not yet become clearly fibrous or striated, the coding is CL = 3
  3. If Stratocumulus formed by spreading out of Cumulus is present, the coding is CL = 4
  4. If simultaneous occurrence of Cumulus and Stratocumulus with bases at different levels are present, the coding is CL = 8
  5. If there are Cumulus mediocris or congestus, all having their bases at the same level, the coding is CL = 2
  6. If none of the above are applicable, then choose the cloud that predominates from the following:
    • If Stratus fractus or Cumulus fractus of wet weather predominates, use code figure CL = 7
    • If Stratus nebulosus/fractus of dry weather predominates, use code figure CL = 6
    • If Stratocumulus non-cumulogenitus predominates, use code figure CL = 5
    • If Cumulus humilis/fractus of dry weather predominates, use code figure CL = 1
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The text enclosed in grey-shaded boxes, like this example, comprises Annex I to the Technical Regulations (WMO-No. 49) and has the legal status of standard practices and procedures.

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