Strange Doings in the Sky Today. What the Heck is a Circumzenithal Arc?

We live our lives never truly knowing when the day comes that something remarkable happens. I was doing totally normal errands today in the middle of town when I saw a sun dog, a common enough occurrence, but it was so bright I decided to snap a shot. But as I got out of the car, I realized something more complex had become visible, something I'm fairly sure I've never seen before. The sun dogs were connected to a halo around the sun, but at the top was an "upside-down" rainbow, like a giant smile in the sky.

I made use of a highly technological sun-blocking tool that I have in my pockets sometimes to try and bring out the colors a little better. In my capacity as an earth science instructor I generally teach about climate and weather, but phenomena related to the refraction of light off hexagonal ice crystals in the upper atmosphere gets lost in the concerns over global climate change and that sort of thing. So I haven't kept up the finer details of atmospheric refraction effects, and had to get a refresher about what I was seeing.

Source: Meteorology Today by Don Ahrens

There were five phenomena happening at once here, all related to the refraction of light in ice crystals in the upper atmosphere: a 22 degree halo, part of a 46 degree halo, two sun dogs, an upper tangent arc, and high above, the circumzenithal arc (the upside-down "rainbow"). I read that the arcs are not uncommon, but are noticed less because they tend to occur overhead where people don't tend to look. I didn't see it myself until I stopped on the way home to try and catch the arc again. It can be seen in the picture below.

Beautiful things can find you any time. You just need to watch for them!
 

Ice Crystals at Work in the Upper Atmosphere

There were some ice crystals in the upper atmosphere around here over the last two days, so several sky phenomena caught my attention while I was out and about. This morning, light rays from the sun reflecting off of the platy crystals produced a 22° ice halo (above), and a sun dog (below).

Last night I noticed an odd glow in the sky as the sun was nearly setting. It was a sun pillar, which is also a consequence of sunlight reflecting off of horizontal ice crystals.

Picture of My Hand. Oh, and Some Sun Dogs with an Ice Halo

I was out at the San Joaquin National Wildlife Refuge this afternoon, checking on what migrant birds are still hanging around as we approach spring. I noticed some sun dogs in the western sky, and snapped a shot or two, but the bright sun was causing lens flares that were messing up the shots. It finally occurred to me to put my hand in front of the sun and suddenly I saw something I've never seen or noticed before: a 22° ice halo around the sun.

The sun dogs (also called mock suns or phantom suns; scientists call them parahelia) are caused by the refraction of sunlight through hexagonal ice crystals in the upper atmosphere. The rainbow colors in the sun dogs themselves happen because of the prisming effect of the crystals.

Either that, or I have summoned forth the twin solhundes (sun wolves) of Norse mythology...