Wednesday, January 9, 2008

Many splendored thing...

As a transplant to Minnesota from Southern California, I've found winter fascinating. There are so many kinds of snow. One of my favorites is a kind of snow pellets. They're not hard and icy like sleet or hail. They tend to be small, and remind me of the little white Styrofoam balls you find inside some bean bag chairs. They don't happen often, but when they do they're delightful to watch in my easily amused opinion.

After 4 years here, I still hadn't found any local who could tell me what they are called. Some hardly knew what I was describing, which seemed odd to me. I'd been given answers such as "sleet", "angel poo", "snow BBs", and "What? Oh those. No idea. It's a kind of snow."
Chart at
I finally solved the mystery online. I found a chart on showing the various kinds of snow flakes, and good descriptions of how each forms. (Click the thumbnail to see the chart.)

My "snow pellets" are apparently called graupel, and form when a regular snowflake gets "rimed", as described by Kenneth G. Libbrecht of Caltech.
Clouds are made of countless water droplets, and sometimes these droplets collide with and stick to snow crystals. The frozen droplets are called rime. All the different types of snow crystals can be found decorated with rime. When the coverage is especially heavy, so that the assembly looks like a tiny snowball, the result is called graupel.

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