High-level clouds

There are three forms of high-level clouds, Cirrus, Cirrostratus and Cirrocumulus. In all three sub-divisions, cloud particles consist of ice crystals which are dry and widely spread. Therefore icing problems are virtually nil, despite the cold temperatures aloft. Also, there is no precipitation from this cloud. In addition, contrails are another form of high-level cloud.

(image embedded from NASA on 29 May 2009) Video embedded from YouTube on 18 April 2009
Cirrus (CI)
Cirrus, given the prefix CI, comes from the Latin word for a tuft or curl of hair. Cirrus clouds are very wispy and feathery looking. Cirrus is a feather- like type of cloud often of pure white colour covering less than the whole sky. Cirrus generally occurs in fair weather and point in the direction of air movement at their elevation. Generally, the presence of Cirrus clouds indicates high wind speeds aloft and this is reflected in its streaky presence. Unless associated with a jet stream, turbulence is not likely to be more than light to moderate.

Transparent to translucent Cirrus covering most of the sky (image embedded from NASA on 24 March 2009)


Cirrus (image embedded from NASA on 24 March 2009)


Scattered Cirrus

Cirrostratus (CS)
Cirrostratus, given the prefix CS, is of smooth and fibrous appearance like a large veil. It often covers large areas of sky. The sun (and the moon when visible) appears with a halo around it. This type of cloud is often used as an indicator of approaching deteriorating weather if its thickness is substantial. Negligible turbulence is associated with Cirrostratus.



Cirrostratus (image embedded from NASA on 25 March 2009)


Cirrostratus at Night

Cirrocumulus (CC)
Cirrocumulus, given the prefix CC, has a sheep’s wool cover appearance. It can be composed of small ripples covering small areas of sky or it can cover almost the entire sky. Generally, the arrangement is fairly regular in undulation. Unless associated with a jet stream, this cloud does not produce much turbulence, only light to moderate occasionally.

Cirrocumulus (image embedded from NASA on 25 March 2009)


Slowly Dissipating Cirrocumulus (image embedded from NASA on 25 March 2009)


Cirrocumulus at sunset

1. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION (2008). On-Line Cloud Chart. Retrieved from National Aeronautics and Space Administration on 20 March 2009.
2. UNIVERSITY OF ILLINOIS AT URBABA- CHAMPAIGN (2009). Cloud Types. Retrieved from University of Illinois at Urbana-Champaign on 22 March 2009.
3. WIKIPEDIA (2009). List of cloud types. Retrieved from Wikipedia on 20 March 2009.

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