Is It A Sun Dog? Or Is It A 22° Halo?
Have you ever noticed a ring around the sun when you’re out in the mountains? It might be a sun dog, but more likely it is a 22° Halo. It’s a common misconception to think that any ring around the sun is a sun dog, or maybe you know it by its scientific name, parhelion. Sure we probably all have been on a ski tour or on a chairlift and pointed out a sun dog to our buddy. It’s fun to say “sun dog,” but sun dogs are actually just one form of ice halo.
Both sun dogs and 22° Halos are atmospheric phenomenon that are a form of circular halos. A 22° Halo appears as a full ring around the sun or the moon, but a sun dog appears as two bright spots on either side of the 22° arc. Typically the two are interconnected. Often sun dogs are so bright that they obscure the rest of the ice halo and have a reputation for standing alone as blindingly bright spots on either side of the sun. These spots from because of the orientation of the ice crystals as they call through the air. Both sun dogs and 22° Halos can be seen all over the globe at all times of the year. They are easier to see when the sun is low on the horizon.
These beautiful natural ice halos are created by light interacting with millions of randomly oriented ice crystals in the atmosphere. Light is refracted through prism-like, plate shaped hexagonal ice crystals at a minimum deviation of 22°, but can range from 22-50° These ice crystals float in cirrus or cirrostratus clouds high in the upper troposphere – about 3 to 6 miles or 5 to 10 km – above the earth’s surface and often in very cold weather.
It’s all quite scientific stuff that goes beyond the simple life of ski bum. Next time that you spot a sun dog or a 22° Halo, now you can school your friends on what’s what.
Sun dogs and ice halos have a reputation that there is moisture in the air and a powder day is coming soon. Unfortunately this is not always true. A sun dog is not always a tell tale sign of moisture or snow in the immediate forectast. It’s just an optical phenomenon that’s freaking cool.
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