Iridescent Pileus Cloud Over Curitiba, Brazil

January 12, 2016


Photographer: Fabiano B. Diniz
Summary Author: Fabiano B. Diniz

Driving home from work in Curitiba, Brazil, I noticed a beautifully iridescent pileus cloud. When I got home this pileus, though partially hidden by clouds in the foreground, still displayed iridescence. I grabbed my camera to snap a few shots. In thunderstorm updrafts the mass of air that's being forced higher will on occasion form a smooth, rounded cloud if the column of rising air becomes fully saturated.

Iridescent colors are due to diffraction of sunlight by similarly-sized water droplets in a rising air current. As an iridescent cloud is, in essence, a type of corona, it's seen when looking in the vicinity of the Sun (or the Moon). Of course, be sure to protect your eyes whenever viewing the Sun. Photo taken on January 13, 2015.

Photo Details: Camera: Canon EOS REBEL T3i; Lens: EF-S18-135mm f/3.5-5.6 IS; Focal Length: 135mm; Aperture: ƒ/8.0; Exposure Time: 0.0006 s (1/1600); ISO equiv: 100; Software: Adobe Photoshop CS6 (Windows).