Iridescence on A Summer Afternoon

September 23, 2004


Provided by: John A. Adam, Old Dominion University
Summary authors & editors: John A. Adam

The photo above showing cloud irisation was taken in mid August 2004 just south of the Peak District in central England. The morning had been rather wet and drizzly, but in the afternoon the cloud layer broke up, and it became quite sunny and warm. I noticed this cloud out of the corner of my eye and took a sequence of photographs to capture the subtle changes in iridescence as the cloud drifted slowly westward. Irisation or iridescence clouds are essentially detached coronae. They're caused by diffraction of light -- minute water droplets in clouds (usually mid level clouds) interfere with sunlight. Sadly, relatives I was with seemed somewhat reluctant to share my enthusiasm for this delicate and beautiful natural phenomenon.

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