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Thread: Blue snow

  1. #1
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    Default Blue snow

    I was very interested in Ryan's photo of the snow that was so dense that it looked blue. In fact, it looked almost as if someone had poured either antifreeze or blue Gatorade onto it. (Just don't get those two mixed up in your household...) I have often noticed myself that snow has a bluish cast under certain conditions, especially where compressed by a footstep on a bright day. So, what I'm wondering is...why does it look blue??

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    I seem to notice it if it is a water-saturated snow. Perhaps the higher content of water absorbs more spectrum of light...except blue, like water does in other locations.

    I guess it could also make sense that if you 'step' on snow you are compressing the air out and thus concentrating the water/volume of snow ratio?

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    "blue snow" is more commonly seen in glacier activity but every once in a while, ice pellets, dense snow, etc can cast this blue tint. A thorough explanation is seen here: http://www.gi.alaska.edu/ScienceForum/ASF7/773.html It's not only seen on Mt washington or parts in the far north/south, It was even recently seen in central NY: http://www.9wsyr.com/news/local/stor...zTtJF5bXQ.cspx. If you can get out climbing in the Whites soon, you can see it even in Pinkham Notch as I saw yesterday as I shoveled my car out. It was everywhere yesterday as well once we got below the cloud base and the snow cat bladed the edge of the road. The key is to look for it. It's not common but currently it can be witnessed.
    Ryan Knapp
    Staff Meteorologist/Night Observer, KMWN (Mt Washington Obs., NH)

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    Thanks for the explanation and the links, Ryan. So it has to do with the light spectrum. The deep snow absorbs colors at one end of the spectrum and reflects back colors at the other end. I suppose that once we get past the red (being absorbed by the snow) and on past the middle colors (yellow, green) and into the blue, some violet might actually be getting reflected back to our eyes, but it's not as bright as the blue, so maybe that's why we don't see it or notice it. (If you look at an image of the spectrum of visible light, you'll see what I mean.)

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