Rare cloud sighting
We were very lucky today to spot not one but two rare atmospheric phenomena today – nacreous and noctilucent clouds. Nacreous clouds are found in the stratosphere 15-25km above the surface of the Earth, and are thus high above other ‘normal’ cloud types. They are usually only seen in polar regions when the sun is below the horizon but reflects off the high clouds. The colours are beautiful and shimmering, reminiscent of an aurora. In the photo above, the nacreous clouds are the faint blue pattern on the lower left side. (The white band on top right is the noctilucent cloud – see below).
Noctilucent (or polar mesospheric) clouds are so high they have been labelled as being ‘on the edge of space’, between 80 and 120km above the planet. They are typically blue or white and are seen to shine before dawn and after dusk – or in the polar night when the sun is 6-16° below the horizon. Their origin is an unsolved mystery, as theoretically there should be no ice or water at this level. One theory (by far my favourite) is that dust and ice is shed by small meteors as they enter the planet’s atmosphere… quite something to look at glowing clouds in the dark sky and think they are formed from extraterrestrial ice 🙂 The noctilucent clouds are easily visible in the photo above as a glowing white band.