Jay Peak, Vermont Skiers Get Awesome Sky, Impromptu Atmospheric Science Lesson

From @erikosterlund via Twitter, the sky over
Jay Peak, Vermont last Saturday.  

It was the perfect day to ski at the Jay Peak Resort in Vermont, right close to the Canadian border this past Saturday.

The sun came out, the snow was great, the temperature was comfortable.

But what happened in the skies over the mountain Saturday afternoon was worth way more than the price of admission.

Some high, thin clouds, the low angle of the December winter solstice sun, created a spectacular show in the sky.

Skiers at Jay Peak got to witness such atmospheric phenomenon as sun dogs, two sun halos, a sun pillar and something called a circumzenithal arc, among other things.

When there's high, thin clouds, which are made out of ice crystals, you sometimes get halos, sun dogs and the like. But Saturday brought out pretty much all the gorgeous and cool phenomena that cirrus clouds can muster.

Let's explain some of them, for the benefit of those (like me!) who were not lucky enough to be skiing at Jay Peak Saturday afternoon.

We'll start with sun dogs. When the sun shines through the ice crystals in those high thing clouds, a bright spot forms near the sun, at least when the ice crystals are laying flat, in a horizontally.

It's called a sun dog, I think, because it looks like a little companion to the sun, kind of like a dog taking a walk with its owner.

There was also a halo around the sun Saturday afternoon at Jay Peak. Those form when the ice crystals in the high, thin clouds are not all horizonal, but jumbled in different positions.

What must have happened Saturday is a lot of the ice crystals were horizontal, so you got a sun dog, but some of them were more vertical, so you also got a halo around the sun.

In fact, there were two halos around the sun, as you can see in the picture.

Now, what the heck is a circumzenithal arc? Say that five times fast.

A circumzenithal arc forms when sun shines through the top of an ice crystal and is diverted out the side of the crystal instead of going through.

You have to be at the right angle with the sun to see them, and there has to be a relative lack of clouds where the arc forms in order to see it. Jay Peak skiers got lucky.

Circumzenithal arcs are often referred to a upside down rainbows, or, the way I prefer, a grin in the sky.