SNOW IN THE WORLD
People think of snow as white and fluffy, and it is sometimes compactible (good for
snowfall fights and snowmen). Often it is thought of as beautiful, great to ski on, a joy to play in,
but a pain to shovel. When it falls for the first time and while playing in it or on it, it is fun, but
after a long winter, especially as it begins to melt, it can become ugly and a nuisance. Snow is a
big part of living in Canada, but few people know much about it.
- formation and snowfall
Snow falls for the same reason that rain falls. The sun evaporates water in lakes and
oceans, and on the ground. The water is lifted into the air, condenses (goes back to water) and
forms cloud droplets. A group of cloud droplets make up a cloud. If the cloud is lifted, due to
mountains or other clouds, the clouds becomes too heavy and must drop some of the cloud
droplets. It then rains.
Snowfall is the same, except instead of the clouds being made up of cloud droplets, the
evaporated water sublimates to ice and ice crystals form. Many ice crystals together can also
form a cloud. The air temperature at which the ice crystals form determine the shape of ice
crystal (see below). As the ice crystals fall, they grow larger and become snowflakes. At an air
temperature of -15oC, flat star shaped snowflakes are formed, whereas at -5oC,
long thin needle shaped flakes are formed.
As the snowflakes fall through the air, they may fall through a layer of water droplets.
The snowflakes are larger and colder than these water droplets. The water droplets can freeze
onto the snowflakes. Sometimes so much water freezes on the snowflakes that by the time the
flakes reach the ground, it is really hard to tell what shape of flake fell.
- accumulation and snowpack changes
When snow falls, lands on the ground, collects, and does not melt, a snowpack develops.
Over the winter, the wind blows the snow into drifts. As new snow falls, the snow on the ground
becomes harder. Some of the snow melts and refreezes. As the winter progresses, the snow
flakes become rounder and larger and look like little balls of ice.
Due to the continuous snowpack changes over the winter, layers form. These layers show
the history of snowfall.
- melt
When climatic conditions are appropriate and there is enough energy input to the
snowpack, melting can being. Melitn is the phase change from solid to liquid.
Snowmelt is of great importance to flood forecasting and water management practices. It
should also be noted that not all snow that melts ends up in our rivers; some of the snow
infiltrates into the ground and other melt waters evaporate.
BRIEF HISTORY OF SNOW RESEARCH
(see Colbeck, S.C., 1987. History of Snow-cover Research.
Journal of Glaciology :S60-S65; and
Murphy, C., 1995. In Praise of Snow.
The Atlantic Monthly, January 1995,
275(1): 45-58.)
srf@cnr.colostate.edu
COPYRIGHT ©1996-2002 S.R. Fassnacht
Last update: SRF, 2002.X.02