Sundog

I mentioned Goldfield, Nevada recently. There I noticed a street called Sundog Avenue that looked like the kind of place where one could experience a sundog in person. Then I tucked the thought away for a few days until I had more time to explore it.

A sundog describes a specific atmospheric condition that allows a bright spot of light to appear on both sides of the sun. Some people call it a mock sun. Scientifically it’s a parhelion which derives from the Greek, “beside the sun.” Maybe it’s easier to demonstrate visually:

Sundogs and 22 degree Halo. Photo by Ross Thomson; (CC BY-NC-SA 2.0)

This image has sundogs — the two bright spots on the left and right — plus a halo. No wonder the ancients sometimes interpreted this phenomenon as an omen or a sign from God. They’re pretty freaky. The Weather World 2010 Project provides a succinct explanation:

“Sundogs form as sunlight is refracted by hexagonal plate-like ice crystals with diameters larger than 30 micrometers and their flat faces horizontally oriented. Sundogs are visible when the sun is near the horizon and on the same horizontal plane as the observer and the ice crystals. As sunlight passes through the ice crystals, it is bent by 22 degrees before reaching our eyes, much like what happens with 22 degree halos. This bending of light results in the formation of a sundog. The difference between sundogs and halos is the preferential orientation of the ice crystals through which the light passes before reaching our eyes. If the hexagonal crystals are oriented with their flat faces horizontal, a sundog is observed. If the hexagonal crystals are randomly oriented, a halo is observed.”


Etymology

I understand the term parhelion because it makes perfect sense. The etymology of sundog is a bit more shrouded in mystery. Most sources don’t seem to know much more than it’s “obscure.” However, I did find a book published all the way back in 1882 that took a stab at it. I consulted Folk-etymology: A Dictionary of Verbal Corruptions. It’s “the phenomenon of false suns which sometimes attend or dog the true when seen through a mist… dog here is no doubt the same word as dag, dew or mist.”

OK, if you say so, Mr. Folk-etymology Dictionary. I have no means to confirm that interpretation. Thus, feel free to accept or reject that claim, or even create one of your own.


A Possible Recording

Google Street View may have also captured a sundog in the United Kingdom.

Sundog Outside of London. Google Street View image capture; February 2009.

I wish I could take credit for this find but it’s not mine. It comes from a flickr discussion group on sundogs and related phenomena. I took a screen grab because it will disappear the next time Google refreshes its imagery outside of London. It’s still there as of October 2011 when I published this post. Go ahead and ponder it further if you like.


Sundog Used in Place Names

Curiosity gnawed at me. So I decided to see if I could find any sundog place names anywhere. I got positive results in the US Board of Geographic Names database and Natural Resources Canada – Geographical Names Canada database. However the pickings were slim. I also looked in Australia and the UK where I found nothing.

I had much better luck finding streets named after sundogs. I’m sure there are many others because I found these without too much difficulty and I stopped when I got tired of searching. These tend to be located in wide-open spaces where sundogs would be easier to spot, as one would expect.


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4 responses to “Sundog”

  1. Corey Loney Avatar

    No geographical features, but I’ve observed sundogs numerous times in Northern Virginia. On winter days where there are high clouds, driving west from the Beltway on Braddock Rd. late in the day seems to increase one’s chances of seeing sundogs considerably, though I don’t know why. During the winter of the Snowpocalypse, I saw them from there on three or four different occasions.

    1. Twelve Mile Circle Avatar

      Sundogs in my own backyard? Now I really have to keep an eye open for them!

  2. stangetz Avatar
    stangetz

    They happen quite often and all over the place. Most people dont realize they are there because you dont necessarily want to look at the sun, even though these are off to the side. Alos, having polarized sunglasses on helps.

  3. Bill Harris Avatar
    Bill Harris

    FYI, typo in the second line- “could”

    I’ve seen a fair number of sundogs here in Delaware. I can’t say how many times I’ve seen them- enough times to not be surprised but not enough times to not stop and admire them. Like Corey Loney’s experiences, they seem to occur in the winter when there are high clouds in the sky. That makes sense, as those are ideal conditions for ice crystals in the atmosphere.

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