Whilst they may not know the name, most cloudspotters will have noticed ‘crepuscular rays’. These are the radiating beams of sunlight that appear to burst from behind a Cumulus cloud, or shine down through a hole in a Stratocumulus (e.g. see Angela Cragg’s image in the photo gallery). These appear when the path of sunlight is made visible by atmospheric water droplets too scarce to appear as cloud, but plentiful enough to noticeably scatter the light. The shadows of the clouds give edges to the sunbeams. The perspective, as the rays approach, makes them appear to radiate outwards. Crepuscular rays are a common and beautiful sight.

Much more rare are ‘anti-crepuscular rays’, like the fine example shown above. These appear to emanate not from the sun, but from the point on the horizon directly opposite it. Cloudspotters will, therefore, only see anti-crepuscular rays when they stand with the sun directly behind them. The shadows of individual clouds behind the cloudspotter are cast onto the cloud layer in front. In the photo above, this is a high layer of ice crystals, called a Cirrostratus. As the shadows and rays recede to the horizon, perspective makes them appear to converge at the point opposite the sun even though they are in fact parallel.

Some call crepuscular rays ‘God’s fingers’. Does this mean anti-crepuscular rays are the ‘digits of the Devil’?
We sincerely hope not.

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)


To contribute a Cloud of the Month,
go to our Photograph Submissions page.

Back to home page