Why does snow sometimes appear blue?
By Terry Eliasen, WBZ-TV Meteorologist, Executive Weather Producer
BOSTON - OK, we all know that snow, in general, is white in color. But, did you ever stop to think why? Furthermore, have you ever seen blue snow? It is a real thing!
WHY IS SNOW WHITE (no, not the one with the dwarfs):
Snow appears white for the same reason the sky appears blue. It is simply a measure of how much visible light is reflected back and then seen by our naked eyes.
The sky is blue because tiny air molecules in our atmosphere scatter the white light. It just so happens that the shorter, blue waves are scattered more than the other colors, so that is what we see.
Similarly, the snow is white because just about all of the visible light that hits the snow is reflected back.
BLUE SNOW... (not, the same as the yellow snow)
Sometimes the snow can appear blue if you have a rather deep snowpack and are able to look deep within it, perhaps through a hole. This also happens many times looking through deep crevasses in glaciers.
What is going on here?
Essentially the light is traveling down through the snow or ice and as it gets deeper, more and more of the light is scattered. Over a reasonable distance, with enough light being scattered, the particles of light that do emerge from the bottom layer of snow/ice tend to be made up of blue light. Much like the long path through the atmosphere creating the blue sky, the long path through the snow, creates blue snow!
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