Iridescent Clouds

2013-06-14 20:21:32.000 – Mike Dorfman,  Weather Observer

Iridescent Clouds Behind the Stage Office

A month or two ago, after a long and foggy shift, we were getting in the van to make our way back down the mountain. After a relatively boring sky for our shift, we had views of spectacular lenticulars as we were heading back down the mountain. After glancing up past one of the lenticulars, I saw two relatively large, iridescent clouds. One of them was lime green and the other was a deep red.

After a bit of research, realized that iridescence in clouds is caused by similar cloud droplet size. These similar droplets refract sunlight in the same way, therefore allowing the cloud that they compose to glow a specific color. I found several options as to what the cloud we saw may be. One possible option would be an iridescent lenticular cloud. Although most iridescent lenticular clouds vary dramatically in color within the cloud, this is a possible explanation for our sighting.

Although extremely unlikely to be seen during the day, another iridescent cloud is the rare Nacreous cloud. The cold temperatures in the stratosphere allow this cloud to form at extremely high elevations (between 50,000 and 80,000 feet) compared with everyday clouds. These clouds are extremely rare, and are almost primarily seen at high latitudes, where colder temperatures aid in their formation. They are also much more visible near sunrise and sunset when these thin, wispy clouds are more visible. However, a study has shown that lower pressure and turbulence on the downwind side of a mountain may allow for the additional cooling necessary for the formation of these clouds.

Although it is hard to tell what this cloud may be, one thing is sure; this cloud was one of the most colorful and iridescent clouds I have ever seen (the picture above really doesn’t do it justice).

Observer footnote: Our annual event, Seek the Peak is coming up on July 20th! If you want to hike to the summit and earn some great prizes while supporting the Observatory, then Seek the Peak is just the event for you; and it’s not too late to sign up.


Mike Dorfman,  Weather Observer

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