Feb 11, 2015 02:34PM
We’re waiting for snow as I write. It’s one of those storms that could bring us a dusting or a foot; we’ll know when it’s over how much we got.
The people native to the far northern regions of the planet purportedly have dozens of names for the different kinds of snow; there are indeed many vagaries to the white stuff, including color. There’s snowman-making snow, and snow you can cut into blocks for creating structures, and snow that’s good for digging out caves. The flakes themselves are sometimes big and fat and affable, their unique shapes easily discernable on a mitten or an upturned cheek. Then they can be needle-like, wind-driven, practically piercing the skin.
Accumulated snow acquires characteristics as it drifts and settles, and will change as its surrounding conditions change. If there’s enough of it on the ground, you can see that the layers freeze, thaw, compact, and become stratified. If you’ve ever scraped snow from the bottom of skis, or picked it from dog’s paws or horse’s hooves, you know how it can bond to the surfaces with which it comes in contact. Gravity and friction play a part in snow’s behavior (think avalanche), as does the snow’s texture and its moisture content. Snow is dry when its “pores” are filled with air rather than liquid water and wet when the opposite is true. Wet snow has less friction than dry because of the way it freezes.
Have you ever seen blue snow? In my experience there needs to be quite a bit of snow on the ground and you need to be shoveling in order to see it. According to Science IQ.com and the National Snow and Ice Data Center (who knew there was such a place?), most of the visible light striking snow or ice is reflected back. Some of the light that penetrates is absorbed and some is scattered; the absorbed light is “preferential”—that is, more red light is absorbed than blue and so more blue photons are left to pop back out. The snow is like a filter through which more blue light travels.
“Watermelon snow” is an alpine region phenomenon caused by algae. The snow turns red or green after it falls and the algae activity creates a faintly watermelon-like fragrance. Wouldn’t that be nice in January? Other not-so-friendly snow colorants and fragrances are produced by pollutants in the air.