Rare Multi-Coloured Clouds appeared in Britain Sky Due to Polar Vortex. The multi-coloured clouds are sometimes known as ‘mother-of-pearl’ or nacreous clouds because of their shimmering pastel hues which resemble the inner surface of sea shells. Usually the clouds only form over the poles during winter because the air in the upper stratosphere needs to be at least -78C.
The clouds are officially known as ‘Polar stratospheric clouds’ or PSCs and are often seen in more northerly climes such as Scandinavia and northern Canada.
“They are composed of extremely small ice crystals, which are very regular in size,” added Mr Pretor-Pinney.
“This means that they diffract the sunlight significantly as it passes through the cloud, which separates out the light’s constituent wavelengths. The result is beautiful mother-of-pearl colours, which give the cloud its other name: nacreous clouds. “
Even with the freezing conditions, the colourful clouds can only be seen at twilight or just before dawn when the sun is just below the horizon.