© Pauline BennettAn iridescent 'rainbow' cloud photographed above the Molesworth hills.
Pauline Bennett, of Hanmer Springs, took a photo of the iridescent cloud while walking along a ridge above the Clarence River.
She said the cloud hung above the Molesworth hills for about five minutes, giving the trampers a chance to photograph it before the light changed.
MetService meteorologist John Law said Bennett's images were a "great example" of iridescent clouds.
"They are higher-level clouds made of small ice particles or water droplets of similar size which scatter sunlight to give this great effect," he said.
Law said the clouds were rare and hard to spot. "They normally form relatively close to the sun in the sky, so can be hidden by the glare."
The colours on the clouds were caused by diffraction, Law said. Light "bends" around the edge of cloud droplets, diffracting "white" light into the spectrum seen on the clouds.
"As different colours of light are diffracted more than others this is what causes the sunlight to separate into the different colours.
"Because the size of the gap needs to be similar or smaller to the wavelength of light, it is not a phenomenon that happens all the time."
Reader Comments
I call them what they are-"Chemtrails".
Amusing that the metservice here never see them,officially.
Iridescent clouds clouds indeed !
They make aerial oilslicks and quite often drip like too much paint on a wall. Ooh, pretty chemtrails.
I see them very often here - NC - those pretty colors are toxic chemicals reflecting light. Search chemtrails and you'll find more details about which chemicals. Agree with the previous posts re chemtrails.
It was a cloud formed by a plane that spanned across what I calculated at well over 100 kilometres. The colours only reflected red, yellow and green. The green was electric, sort of what you might expect from an oil slick. It did not make my day seeing this.