The last couple of days have been pretty amazing at Summit. Overcast stratus has given away to clear and sunny. The temperature got up to +20F yesterday. Today there were no clouds in the sky, but lots of little ice crystals flowed with the wind. “Diamond dust,” as it is called, seems to be fairly common around here. I’ve seen it on a number of days. Today’s lead to a beautiful optical display with very distinct sun dogs on both sides of the sun and a parahelic circle that passed through the sun and the sun dogs and circled the full sky (below). Halos (like the one to the left that is surrounding me (photo credit: Chris Cox)) are also quite common.
These optical phenomena are due to the reflection and refraction of sunlight from ice crystals of different shapes and orientations.
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