WRAL WeatherCenter Blog

Pillar Talk!

Posted January 7, 2015

On the final day of 2014, we had quite a few people send in very nice pictures of sunrise and sunset scenes around our viewing area, and for the sunsets in particular, we noticed that a number of them caught a view of "sun pillars," an atmospheric optical effect that is most commonly caused by plate-like, six-sided ice crystals that have their flat sides more or less parallel to the ground, but with some "wobbling" to that orientation as well.

The tiny plates are most common in and around high cirrus clouds, and both the photos and weather observations from December 31st confirm that we had quite a few of those in our skies that day, but fortunately with enough breaks and thin spots to allow for a good view of the sun. On several of the sunset photos, there is a noticeable column of light extending upward from the sun, and generally showing the same color as the setting sun, since these pillars are produced by reflections of the sun's light off the faces of the crystals, rather than refracted through them, as would be the case with halos, sun dogs, circumferential arcs, and other phenomena that result in a rainbow-like spectrum of colors.

You can see one example of the sun pillar sunsets here, and there are 5 or 6 others among the photos in the gallery at www.wral.com/weather/image_gallery/14321307/, which contains the New Year's Eve 2014 sunrises and sunsets from our viewers. I've also included a link above to the Atmospheric Optics web site, where there is a nice section on sun pillars that includes descriptions, photo examples, and diagrams explaining how they form.


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