Table 12. Guide for the identification of the genera of clouds
Legend |
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E |
The feature is essential to the genus |
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U |
The feature is usual |
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P |
The feature is possible, occurring sometimes in certain species |
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S |
The feature may occur only at the summit or upper portion of the clouds |
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Consider these criteria in succession |
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Distinctive features |
Genera in which the features occur |
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Ci | Cc | Cs | Ac | As | Ns | Sc | St | Cu | Cb | |||
General shape and grouping of cloud and cloud elements |
Detected with a flattened appearance |
P |
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More or less developed vertivally |
Detached |
P |
P |
P |
P |
U |
U |
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With a common base |
P |
P |
P |
P |
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Thin, with detached filaments |
U |
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Thin, grouped in sheaves, or ending in a hook or tuft |
U |
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Spread out in a patch, sheet or layer, subdivided into more or less regularly arranged layers or rounded masses, the apparent width of most elements being: |
Less than 1° (< 1 finger) |
E |
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Between 1° and 5° |
U |
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More than 5° (> 3 fingers) |
E |
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Spread out as a veil totally or partially covering the sky |
E |
E |
E |
U |
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Structure and texture |
Silky sheen |
U |
P |
P |
S |
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Fibrous (hair like) |
U |
P |
P |
P |
S |
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Granular |
U |
P |
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Undulated or rippled |
U |
P |
P |
P |
P |
P |
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Ragged |
P |
P |
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Uniform base |
U |
U |
U |
U |
U |
P |
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Diffuse base |
P |
U |
P |
P |
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Optical thickness |
Thin clouds, through which the disc of the Sun or Moon can be seen |
U |
U |
E |
P |
P |
P |
P |
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Translucent clouds, revealing only the position of the Sun or Moon |
P |
P |
U |
U |
P |
P |
P |
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Opaque clouds |
P |
U |
U |
P |
U |
P |
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Shading |
Without shading |
U |
E |
U |
P |
P |
P |
P |
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Partly shaded |
P |
P |
U |
P |
P |
U |
P |
U |
U |
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Shaded throughout |
P |
U |
U |
P |
U |
P |
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Supplementary features and accessory clouds |
S |
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P |
P |
P |
P |
P |
P |
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P |
P |
U |
U |
P |
P |
P |
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Uniform (intermittent or continuous) |
P |
U |
P |
P |
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In the form of showers |
P |
U |
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P |
P |
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P |
P |
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P |
P |
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P |
P |
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P |
U |
P |
U |
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P |
P |
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P |
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P |
P |
P |
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S |
S |
S |
S |
S |
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P |
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P |
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Hydrometeors |
P |
U |
P |
P |
U |
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P |
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P |
P |
P |
P |
P |
P |
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P |
P |
P |
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P |
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P |
P |
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P |
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Photometeors |
P |
U |
P |
P |
S |
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P |
P |
U |
P |
P |
P |
P |
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P |
P |
P |
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P |
P |
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Electrometeors |
P |
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P |
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P |