C_H = 2

(a) TECHNICAL SPECIFICATION

Cirrus spissatus, in patches or entangled sheaves, that usually do not increase and sometimes appear to be the remains of the upper part of a Cumulonimbus; or Cirrus castellanus or Cirrus floccus.

(b) EXPLANATION

(i) Cirrus corresponding to C_H = 2 are of the species spissatus non-cumulonimbogenitus, Cirrus castellanus, Cirrus floccus, or a combination of all these.

(ii) Cirrus spissatus consist of patches of sufficient optical thickness to appear greyish when viewed towards the Sun. They sometimes have borders of entangled filaments (variety intortus), and may give the erroneous impression that they are the remains of the upper part of a Cumulonimbus.

(iii) Cirrus castellanus show small fibrous turrets or rounded protuberances, rising from a common base; Cirrus floccus have the form of more or less isolated tufts, often with trails.

(iv) The above-mentioned clouds may be accompanied by Cirrus fibratus or Cirrus uncinus; however, the sky cover of Cirrus spissatus non-cumulonimbogenitus, Cirrus castellanus or floccus or of any combination of these clouds is greater than the combined sky cover of Cirrus fibratus and uncinus.