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Astro Bob

The Sky Is Crystal Clear

1 Feb 2019, 21:58 UTC
The Sky Is Crystal Clear
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Sunlight refracted by prismatic ice crystals in high, thin cirrostratus clouds briefly painted the sky yesterday afternoon. An airplane and its contrail also joined the scene. Besides a halo and sundogs with wispy “tails” you can see the parhelic circle (arc through the sun connecting the sundogs), a Parry arc (rainbow-like arc tangent to the halo) and a diffuse upper tangential arc topping it. Bob King
Skywatching knows no hours. Wherever and whenever you tip your head back, a sight awaits. As I was dashing off to an appointment yesterday, I noticed high clouds and looked up toward the sun to see a brief but lovely display of atmospheric colors. Besides the often-seen halo, there were two sundogs on either side the sun — each with a tail! — a Parry arc, an upper tangential arc and a portion of the parhelic circle.
Two types of ice crystals cause most halos, sundogs and arcs – flat plates and columns or “pencils.”
After all the recent cold weather, a welcome warm front was on its way. Warm fronts announce their arrival with high clouds that gradually yield to lower-altitude types over the next 12 to 24 hours. Whenever you hear of ...

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