Sun pillar in PA

SunPillar_Cirrus_PjJohnson_LancasterCountyPA_5Jul2014

Pj Johnson
Location: Lancaster County, Pennsylvania
Date: 5 July 2014

Patches of cirrus clouds not only make for a colorful sunset as the shorter wavelengths of the sun’s rays (the blues) are scattered away, leaving fiery views, but they can also create other optical phenomena. In this picture, you can see a small, yellow vertical swath of the light above where the sun is setting behind the hills. This is called sun pillar.

A sun pillar isn’t actually a vertical beam of light, but is the collection of light from many ice crystals in the cirrus clouds. Plate-like crystals (like those shown below) gently rock side to side as they slowly fall. The sun’s light is reflected off the horizontal face of these crystals, combining to create this pillar. These can most often be seen at sunrise or sunset when the sun is low in the sky.

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