Questions and Extensions
- What is needed to make it snow?
- Moist air comes toward the Puget Sound region from the
West (which is where the Pacific Ocean is located). The surface of the
ocean off the coast is usually around 45° F in the wintertime. What does
this tell you about the possibility of it snowing down at sea level? Remember
the air near the ground wants to take on the temperature of the underlying
- Dry air may come down from the interior of British Columbia
into the Puget Sound region. This air often is well below freezing but
it usually has very little moisture because it had dry ground under it
rather than the ocean. What does this tell you about the possibility of
getting rain or snow out of it?
We have seen that it takes moisture in the atmosphere
at low enough temperatures to produce snow. The Puget Sound region is a
sort of "crossroads" where moist air and cold air were able to
meet. On 18 December 1990 we had the unusual situation where a mass of
air over the Puget Sound area had enough moisture and was cold enough to
produce snow when it was lifted by the action of the convergence zone.
This was then followed by a push of much colder (but also drier) air which
allowed the newly-fallen snow to linger on and create a major problem in
The following are optional. They extend the content of
this curriculum module and require time and resources beyond the primary
scope of this module.
- How much did it snow? Pick the location, time interval,
and information source. The Web can be used as a resource for this information.
- What percentage of snow is liquid water? Is that figure
always the same?
- What atmospheric signs indicate the likelihood of snow?
Develop a "rating" method for the signs that reflects your confidence
in each one as a predictor.
- At what speed do snowflakes fall? Is the speed connected
to the air temperature?
- How does the annual snowfall of polar regions relate
to mid-latitudes? Try to control for variables like how far the land you
examining is from the nearest ocean.
- Gather data on how air temperature varies with altitude.
Try to obtain the data directly using tall buildings, model airplanes and
rockets, etc. Remember to control for the effects of radiation from surfaces
near your thermometer, wind speed, motors, etc.
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