Unusual Atmospheric Occurence and Iridescent Cloud

Reading the August 2011 of the British BBC magazine FOCUS, I came across some spectacular pictures of rainbow clouds over Mont Everest. The photographer, astronomer Oleg Bartunov, took the below images during a Himalayas expedition in Nepal.

Cloud iridescence is the occurrence of colors in a cloud similar to those seen in oil films on puddles, and is similar to irisation. It is a fairly    uncommon phenomenon, most often observed in altocumulus, cirrocumulus and lenticular clouds, and very rarely in Cirrus clouds. The colors are  usually pastel, but can be very vivid. Iridescence is generally produced near the sun, with the sun’s glare masking it, so it is more easily seen by  hiding the sun behind a tree or building. Other aids are dark glasses, or observing the sky reflected in a convex mirror or in a pool of water.    Iridescent clouds are a diffraction phenomenon cause by small water droplets or small ice crystals individually scattering light. Larger ice crystals  produce halos, which are a refraction phenomena rather than iridescence.

Iridescence should similarly be distinguished from the refraction in larger raindrops that makes a rainbow. If parts of clouds have small droplets or     crystals of similar size, their cumulative effect is seen as colors. The cloud must be optically thin, so that most rays encounter only a single                  droplet. Iridescence is therefore mostly seen at cloud edges or in semi-transparent clouds, and newly forming clouds produce the brightest and most  colorful iridescence. When a thin cloud has droplets of similar size over a large extent, the iridescence takes on the structured form of a corona, a  central bright disk around the sun or moon surrounded by one or more colored rings (Source: Wikipedia).

These pictures immediately reminded me of a UFO report that had been collected by the UK Ministry of Defence in 2004, and which was released in March 2011 on their website.  Two striking color photographs, taken in Sri Lanka by a member of the RAF,  of an “unusual atmospheric occurence” (pictures below) were attached to the report.

Comparing today these pictures, I’m persuaded that the described phenomenon represents a high altitude iridescent cloud…rather than a UFO, a type of nuclear explosion or a sort of air burst… Still a very unusual and rare atmospheric phenomenon that would surprise many of us.

Initiated during 2009 and under the framework of the International Year of
Astronomy, The UAP Observations Reporting Scheme is a project aimed at
facilitating the collection of UAP reports from both amateur and professional
astronomers, via a questionnaire to be downloaded from a dedicated website
(www.uapreporting.org)

Read more at UAP Reporting