Calc American Gods - Shadow thinks of snow

American Gods said:

“What we need,” said Wednesday, suddenly, “is snow. A good, driving, irritating snow. Think ‘snow’ for me, will you?”

“Huh?”

“Concentrate on making those clouds—the ones over there, in the west—making them bigger and darker. Think gray skies and driving winds coming down from the arctic. Think snow.”

“I don’t think it will do any good.”

“Nonsense. If nothing else, it will keep your mind occupied,” said Wednesday, unlocking the car. “Kinko’s next. Hurry up.”

Snow, thought Shadow, in the passenger seat, sipping his hot chocolate. Huge, dizzying, clumps and clusters of snow falling through the air, patches of white against an iron-gray sky, snow that touches your tongue with cold and winter, that kisses your face with its hesitant touch before freezing you to death. Twelve cotton-candy inches of snow, creating a fairy-tale world, making everything unrecognizably beautiful…

Wednesday was talking to him.

“I’m sorry?” said Shadow.

“I said we’re here,” said Wednesday. “You were somewhere else.”

“I was thinking about snow,” said Shadow.

In Kinko’s, Wednesday set about photocopying the deposit slips from the bank. He had the clerk instant-print him two sets of ten business cards. Shadow’s head had begun to ache, and there was an uncomfortable feeling between his shoulder blades; he wondered if he had slept on it wrong, if it was an awkward legacy of the night before’s sofa.

Wednesday sat at the computer terminal, composing a letter, and, with the clerk’s help, making several large-sized signs.

Snow, thought Shadow. High in the atmosphere, perfect, tiny crystals that form about a minute piece of dust, each a lace-like work of unique, six-sided fractal art. And the snow crystals clump together into flakes as they fall, covering Chicago in their white plenty, inch upon inch…

“Here,” said Wednesday. He handed Shadow a cup of Kinko’s coffee, a half-dissolved lump of non-dairy creamer powder floating on the top. “I think that’s enough, don’t you?”

“Enough what?”

“Enough snow. Don’t want to immobilize the city, do we?”

The sky was a uniform battleship gray. Snow was coming. Yes.

“I didn’t really do that?” said Shadow. “I mean, I didn’t. Did I?”

“Drink the coffee,” said Wednesday. “It’s foul stuff, but it will ease the headache.” Then he said, “Good work.”

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We know that pure water density is around 1000 kg (or one tonne) per cubic metre or 62.4 lb per cubic foot. Pure ice is just slightly less dense than pure water at about 917 kg per cubic metre (that is why ice floats on a pond or in our drink). Snow on the other hand has less density because it contains more air in a given volume than the ice. Heavily compacted snow, called firn, can be nearly as dense as ice (around 910 kg per cubic metre) but newly fallen snow more typically weights in at 70 to 150 kg per cubic metre (4.4 to 9.4 lb/cubic foot), but this increases rapidly once snow is on the ground and it begins to compact due to wind, the addition of liquid water and its own weight.

Once on the ground, a snowfall becomes a snowpack unless it quickly melts. The density of the snowpack reflects the conditions during the snowfall and processes that occur to and within the snowpack as it ages. These include compaction by weight and wind, snow melt and cycles of thaw-freeze. Drifted snow is usually denser than undisturbed snow because the crystals are initially smaller and more compact, as I recently rediscovered. Additional rain falling on a snowpack can quickly increase the snow load because a snowpack can absorb rain until it's about 45% saturated. (The snowpack will start melting when the saturation is above 45%.) The density of a snowpack and changes in the density with depth are essential ingredients for avalanche forecasting and danger warnings.

Typically winter snowpacks have a density of 200-300 kg per cubic metre (12.5-18.7 lb per cubic foot), but this can vary with the moisture content of the snow and that can vary across climatic regions. Dave Phillips of Environment Canada reports that one cubic metre of old snowpack in Winnipeg, Manitoba typically weighs around 190 kg (419 lb) and the same volume weights 220 kg (485 lb) in Quebec City. In the wetter climate of British Columbia it is generally higher, at Whistler, BC the same cubic metre may weigh 430 kg (948 lb).

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