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Credit: E. Wiebe

Cloud iridescence can occur when clouds are thin and composed of water droplets with a similar size. Diffraction causes light of similar wavelengths to be bent around droplets of similar size. Where those size occur together and where the geometry of the sun, cloud, and viewer are appropriate the colours are selected and become prominent. Clouds must be thin because otherwise rays of light will be diffracted from multiple droplets and the effect will be cancelled out. The colours are often faint and muted so it can be a challenge to photograph them.

This image is from 2013-06-13 and was taken from the ferry to Denman Island. The ferry's "smokestack" is blocking the sun in the image.

Iridescent cloud examples. Wikipedia.

UVic / SEOS / Climate Group / About Front Page Picture / Cloud Iridescence Last updated: Monday, 31-Mar-2014 15:55:50 PDT
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