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Mountain Cloud Iridescence

Images by Marcella Giulia Pace ( at Cibiana di Cadore in the Italian Dolomites.

Mountains induce cloud formation - orographic clouds. Moist air forced upwards cools and water droplets can then condense out. Wind flowing horizontally around a peak is also cooled on the lee side and causes airflow up from lower altitude - a banner cloud.

Orographic clouds are famous for intense iridescence because their droplets have a similar history and are thus of similar size. The diffraction colours from individual droplets (not like this, it's not even wrong!) overlap and blur less.

Images ©Marcella Giulia Pace, shown with permission