Closely related to the optical effect called a corona, the bands of pastel colours produced by this cloud are known as ‘iridescence’. When the Sun is at the right position, preferably hidden by thicker cloud making observation safer and easier, the cloud’s droplets or ice crystals can diffract the sunlight passing through. The array of microscopic cloud particles bends the coloured constituents of sunlight by different amounts, separating them out into bands.

Iridescence can often occur in Altocumulus and Cirrocumulus clouds, but appears most often in lenticular clouds. The effect tends to be observed at the clouds’ fringes, but it can occasionally appear over large areas, as it has in this fine Cirrocumulus over Perth, Western Australia. Iridescent colours look most dramatic in a young cloud, whose newly formed droplets all tend to be around the same size.

We are genetically programmed to see the beauty in our own children, regardless what little terrors they actually are. But what of baby clouds? Surely everyone loves the iridescent glow of their tender cheeks – especially as they don’t even demand to have their nappies changed.

 

Current Cloud of the Month:
July 2010

Previous Clouds of the Month:
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
Cloud Reflections (December 09)
Numbers in the Clouds (November 09)
Sun Pillar (October 09)
Convection Clouds (September 09)
‘Pile d’Assiettes’ (August 09)
Cumulus congestus (July 09)
‘Asperatus’ (June 09)
Clouds at Night (May 09)
Sundogs (April 09)
Diamond Dust (March 09)
Cloud Streets (February 09)
Crepuscular Rays (Jan 09)
Valley Fog (December 08)
Cloud Shadows (November 08)
Contrails (October 08)
Mamma (September 08)
Kármán Vortex (August 08)
The Summertime Halo (July 08)
The Nor’west Arch (June 08)
Microbursts (May 08)
Irridescent Clouds (April 08)
Northern Lights – Aurora Borealis (March 08)
Ice halos (February 08)
Lightning (January 08)
Roll Cloud (December 07)
Banner Cloud (November 07)
Stratocumulus (October 07)
The Unclassified Cloud (September 07)
Alexander’s Dark Band (August 07)
Fumulus Snail (July 07)
Distrail (June 07)
Altocumulus undulatus (May 07)
Cumulonimbus capillatus (April 07)
Lacunosus (March 07)
Horseshoe Vortex Cloud (February 07)
Jet-Stream Cirrus (Janurary 07)
Altostratus/Altocumulus/Altowhateveritis (December 06)
Anti-Crepuscular Rays (November 06)
Stratocumulus (October 06)
Altocumulus (September ’06)
The Kelvin-Helmholtz Wave Cloud (August ’06)
The ‘Brocken Spectre’ (July ’06)
‘Whale’s Mouth’ (June ’06)
Noctilucent (May ’06)
Cirrus (April ’06)
Cap Cloud (March ’06)
Fallstreak Holes (February ’06)
Nacreous (January ’06)
Cirrostratus (December ’05)
Tuba (November ’05)
Virga (October ’05)
Cirrocumulus (September ’05)
Altostratus (August ’05)
Cumulus (July ’05)
Mamma (June ’05)
Pileus (May ’05)
Lenticularis (April ’05)
Stratus (March ’05)
Cumulonimbus (February ’05)
Contrails (January ’05)


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