Subzero mornings may not be friendly to skin and lungs, but they’re great for making ice crystals. Add in sunlight and you never know what you’ll get. Sometimes those crystals form directly in clear air. Other times they need a nudge from a body of water. Lake Superior provided that source earlier today when the air temperature at the beach dipped to 13 below.
I went down to watch how sunrise would color the tens of thousands of slabs of ice piled up along the shore and got more than I bargained for. A red pillar announced the coming of the sun followed seconds later by the solar flame. Fog, which formed as cold air chilled and condensed over the warmer water, lent the scene an end-of-times otherworldliness.
When the sun climbed stood about a thumb over the horizon two very reddened sun dogs flanked either side. It appeared that water vapor steaming from the lake froze into hexagonal (six-sided) plate crystals called diamond dust that float horizontally downward. Light from the sun passing through their flat, shallow sides exits another side to form bright patches of light 22° to the right and left of the sun. Normally, sun dogs show hues of blue and red, but sunrise sunlight, robbed of cooler colors (blue, violet, green) produce red sun dogs!
The rising pillar is also made by flat plate crystals falling horizontally with their broad sides to the ground, but instead of refraction, each crystal acts as a mirror and reflects sunlight downward to the observer. Looking up, all those tiny reflections add up to form a bright column or pillar.
Once the sun rose higher and grew whiter (white is mixture of all colors from violet to red), the sun dogs became much more colorful and brighter, too. A few minutes later, I noticed that the sun appeared to be balanced on a pedestal of light — a lower pillar. A lower pillar forms the same way as the upper from sunlight reflecting from horizontal ice crystals but instead of the bottom flat faces, light reflects from the top faces upward back toward the sun.
Looking more closely, it was obvious that near the base of the pillar, a subsun appeared. Subsuns form when light reflects off ice crystals. They’re normally seen from airplanes below the sun as reflections from ice crystals in cirrus-type clouds.
I would have stuck around to see what might come next, but I had to be at work. If you ever have the opportunity this winter to watch a sunrise on a bitter cold morning stay with the sun to see what develops. Oh – about the title. Some of you might recognize the reference. It comes from one of my favorite Donovan songs, Epistle to Dippy.