Sundogs

 

We have been seeing a lot of sundogs this winter. When I see them I am reminded of a conversation I had with a young lady on a bitterly cold morning not long ago. I was quite surprised when she said that it was the first time she had seen sundogs.

She spoke like a Midwesterner, and I didn’t detect even a small hint of a southern accent. My first thoughts were, “Where have you been?” Finally I couldn’t resist it any longer and asked her where she grew up. It turned out to be northern Wisconsin. Then I was wondering “what” she had been doing for all those years.

Apparently some people grow up oblivious of such things. I suppose there could be a couple North Dakotans who have not noticed sundogs, but I doubt it. Most people probably think they know them too well.

Sundogs are obviously different than a rainbow, but the basic principles are similar. We generally see sundogs during the winter when the sun is lower in the sky and ice crystals are more abundant in the atmosphere. They can, however, be observed throughout the year.

Two basic factors are required for sundog formation. The sun must be low in the sky such as around sunrise and sunset. The other requirement is lots of cirrus clouds between the sun and the observer in which the ice crystals, shaped like little hexagonal plates, are horizontally oriented. As the sunlight passes through the ice crystals it is refracted, producing sundogs.

The more the ice crystals deviate from a horizontal orientation the greater the vertical dimension to the sundog. Also, the more the crystals wobble in the atmosphere influences how much color is produced. More wobble means more color, and the red color will be closest to the sun.

Of course we usually see two sundogs flanking the rising or setting sun at 22 degrees on each side. Another way to relate to that distance is that is if you extend your arm out in front of you and raise your hand, the distance is roughly two handbreadths from the sun.

Although it is hard to think warm thoughts when we view sundogs, they really are an interesting aspect of North Dakota winters. So, when you get to see them again, and you will, take a little time to observe them. And if there are some kids around, show them the sundogs too.

Chuck Lura

Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Minot State University-Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.

 

 



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