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What is a Sun Dog? | Weather Wise

Sun Dogs, members of the halo family, create optical effects in the sky.

LOUISVILLE, Ky. — Have you ever heard of a sun dog? 

Sounds like some sort of cool rock band, but it’s actually a member of the halo family. These are optical effects in the sky created by a combination of the right sun angle and usually high clouds.

To better understand how the atmosphere produces these bursts of color, we need to understand a little something about light. 

Light is the visible portion of the electromagnetic spectrum. The light we see is composed of all the colors of the rainbow.

Light from the sun is bright white but we can see these colors by using a prism, which breaks visible light apart into its component colors, like reds and violets and everything in between. 

In the sky, under the right conditions, water drops or ice crystals act as a prism. As light passes through the water or ice in high cirrus clouds, it is refracted or reflected and creates halos, sun dogs and sun pillars.

A halo is a ring of light that forms around the sun or moon, while a sun dog, also known as a mock sun, or parhelion, is a colored spot of light that develops due to the refraction or change in direction of light through ice crystals.

Sun dogs are usually 22 degrees left or right of the sun.

Finally, sun pillars appear as a shaft of light extending vertically above the sun, most often around sunrise or sunset. 

They develop as a result of ice crystals slowly falling through the air, reflecting the sun’s rays off of them.

We need high cirrus clouds around to form these optical effects. And the high cirrus clouds can often be moving in ahead of an approaching storm system. 

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