'It's Like A Rave In The Sky'

Today we were very fortunate to be treated to a display of rather amazing clouds. Nacreous (or Polar Stratospheric) clouds form during the polar winter at an altitude of between 15,000 and 25,000 metres. Due to their height, they are illuminated for a long time before sunrise and after sunset and are highly iridescent. Some of the clouds, especially the electric blue ones, were so bright that I couldn't look directly at them.

Iridescence occurs as light is diffracted by water droplets or ice crystals, and can be seen in other clouds around the world. I have seen it many times in the UK, especially in Alto cumulus clouds in Autumn, but never as bright as it was in nacreous clouds.

Most people on base came to look and take photos and it was fun to hear people's reactions and description. Our electrician, who has clearly had a far more active social life than I have, said, 'It's like a rave in the sky where all the clouds are taking LSD and tripping out'. Quite.