Naturespeak 

Snow 101

By Heather Beresford,

Whistler Naturalists

This time of the year brings endless speculation about the upcoming ski season and it all centres around how much snow we will get. Until recently, Ullr was a little stingy with the white stuff but redeemed himself with some big dumps last week. The Farmers' Almanac is predicting a big year and I saw a lot of caterpillars crawling across the Valley Trail in the fall, so obviously we're in for a great season.

What we really want is a ton of powder, but not all snow makes great powder. Snow will have different consistencies depending on the shape of the snowflakes and the amount of air space left between the flakes when they fall on top of each other. Also, as we know here on the "wet" coast, moisture and temperature play a big part in the quality of powder. By definition, powder snow has a density of less than 200 kilograms for every cubic metre of snow. In very dry areas, 1 centimetre of water will produce 20 centimetres of snow, but in very moist areas 1 centimetre of water may only produce 6 centimetres of snow.

The basic snow types are individual snow crystals , often with six-fold symmetrical shapes; snowflakes which are collections of snow crystals that can grow up to 10cm across especially when the snow is wet and sticky; rime which is supercooled tiny water droplets; then there are loose collections of frozen water droplets called graupel (those little "styrofoam" pellets); and good, old hail .

There are a variety of snow crystal shapes, such as plates or columns, but the best for powder are plate-like crystals in dendritic form. These crystals have "arms" extending from the centre which leave air space between each crystal making for fluffy, light snow conditions when they pile up on the ground. But it's tough to find a perfect six-sided snowflake. They actually occur less than 25 per cent of the time because of the buffeting they receive from wind, water and other snowflakes on their journey from cloud to earth.

But how do they grow arms? The growth of a snow crystal usually begins with a dust particle, which absorbs some water molecules that form a nucleus for the ice crystal. Faceting then causes the crystal to quickly grow into a tiny hexagonal prism. As the crystal grows larger, the corners often sprout tiny arms, since they stick out a bit further into the supersaturated air and so grow a bit faster. Since the ambient atmospheric conditions are nearly identical across the crystal, all six budding arms grow at roughly the same rate. Crystal growth rates depend strongly on temperature and different shapes result as the crystal blows about in the cloud and descends to earth.

But enough of the science – let's shred!

Christmas Bird Counts:

The Christmas Bird Count (CBC) is an incredible example of what volunteer efforts can achieve. This year marks the 102nd (!) annual CBC. The Count now attracts over 50,000 participants from across North America, Latin America, and the Caribbean. Our area hosts three counts: in Squamish, Whistler, and (for the first year) Pemberton-Mt. Currie. You don’t have to be an expert birder to participate, and you can get involved in either the field counts or by watching your own feeder. For more details, contact the organizers listed below.

Squamish, Saturday, Dec. 15th. Contact Jim Wisnia (604-898-2000).

Whistler, Tuesday, Dec. 18th. Contact Karl Ricker (604-938-1107) or Michael Thompson (604-932-5010).

Pemberton-Mt. Currie, Thursday, Dec. 27th. Contact Hugh Naylor (894-6402), or Karl Ricker (938-1107).

Whistler Naturalists AGM

Thanks to everyone who attended last Thursday’s Annual General Meeting of the Whistler Naturalists. Thanks very much to Andrew Bryant for his informative and entertaining talk on Vancouver Island marmots. Thanks also to Gordon McKeever of Rainbow Retreats Accommodation; Gone Bakery; Whistler One-Hour Photo, and the staff and volunteers of Millennium Place. Special thanks to the two keen (and persuasive) girls from Pemberton who sold marmot plush toys to raise funds for the Vancouver Island Marmot Recovery Project.

Sightings and Memberships: NatureSpeak is prepared by the Whistler Naturalists. To become a member or to report noteworthy sightings of mammals, birds, and other species, contact Bob Brett (604-932-8900; e-mail: snowline@direct.ca).

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