Smiles in the Sky

There will not be many days where I look up and spot a circumzenithal arc, so today's blip selects itself.

This optical phenomenon, sometimes referred to as the "cloud smile", is associated with cirrus clouds, and is caused by sunlight refracting through horizontal ice crystals. This is a similar phenomenon to sun dogs, which I've blipped previously. They are usually a quarter circle, and appear at the zenith. The colours run from blue at the zenith through to red on the horizon side. They are brightest when the sun is 22 degrees above the horizon, it was about 15 degrees at 14:00 today, when we spotted this one. Richard Hamblyn's The Cloud Book is, as always, my source of cloud lore and science.

It wasn't the only smile in the sky when this was taken. 4yo is in silhouette, so you can't make out her beaming grin as she tackles the playground high-wire.

bright ice crystal smile
an intrepid sky walker
wanders overhead