Sun Dog

Even the sun can have a pet:  the sundog.  

And last week, as high clouds streamed in overhead, a good example of this feature was captured by weather videographer extraordinaire Greg Johnson of Skunk Bay Weather.

During a sundog event,  areas of light are seen on both sides of the sun (see example below).  These are the "dogs."    Sundogs are also called "mock suns"

The ancients thought that sundogs were ominous signs, foretelling events such as the death of kings.  Today we know that sundogs generally occur when the sky is filled with a thin veil of ice crystal clouds, generally cirrostratus.

Now let me show you a video captured by Greg Johnson from his location in northern Kitsap County around 6:30 AM last Wednesday.  From his camera, you only see one of the dogs.

The sky at the time of sun dogs was full of high ice crystal clouds, called cirrostratus.    You can see the extensive veil of such clouds from the visible satellite picture taken about this time (see below):

Why sun dogs?     

They occur when ice crystals in the clouds--shaped in six-sided plates--are oriented roughly horizontally.    With that orientation, they preferentially bend the light by 22 degrees, creating two areas of light (22 degrees on both sides of sun), as illustrated by the figure below.

Ice crystals that are smaller and tumbling about create circular halos.

As shown in the picture above, many sundogs have rainbow colors as well, something also illustrated in the picture below. 

These colors are produced by dispersion, the breaking up of visible light into its component wavelengths, as it passes through the ice crystals, not unlike what happens in a prism (see below).

Cirrostratus and associate halos and mock suns are often a sign of an approach weather system, such as a front or cyclone.   Thus, although it may not foretell the death of kings, it can suggest the end of nice weather.

And then there are the "other" sundogs...