Not just frozen water:
Measuring snow’s nitrogen
pulse
Sarah J. Nelson, University of Maine
Hannah Webber, SERC Institute
Ivan Fernandez, University of Maine
“Snow on the ground is a
dynamic medium.”
- Mark Williams, UC Boulder
Snowfall:
• Freshly fallen snow.
• For example, 2.5 inches of snow fell in
Bangor on Feb. 27, 2010.
Snowfall:
Protocol 9
Snowpack:
• Accumulated snow
on the ground.
• E.g., Snowpack was
36 inches on Feb. 26,
2010.
Snowpack:
Protocol 9
Snow Water Equivalent (SWE):
• “the amount of water contained within the
snowpack.
• It can be thought of as the depth of water
that would theoretically result if you melted
the entire snowpack instantaneously.”
Snow water
equivalent:
Protocol 10
Snow Density:
• the ratio of the volume of meltwater that
can be derived from a sample of snow to
the original volume of the sample.
• E.g., 1.2" water equivalent divided by 15" of
snow = .08 density (= 8%).
We will measure snow melt:
Surface runoff produced from melting snow
How much water?
Stream
stage:
Protocol 8
How much nitrogen through
the snowmelt period?
Nitrogen in
stream
water:
Protocol 7
Snowmelt is surface runoff, but
• By the time it’s in the stream, was are also
measuring what has moved through the
watershed (some soil signal, existing
water in the stream)
• Other protocols deal with soils and
watershed characteristics – these give
students’ questions some dimension!
Watershed scale: snow cover
• Which places have snow, and how patchy
is it?
Density & SWE math
• Snow Density = Snow Depth / SWE
 Density must be in decimal form. For
example: 25% = 0.25
 Density is usually specified in kilogram per
cubic meter (kg/m3).
• The density of water is 1000 kg/m3 and snow
density is usually measured as a ratio to this.
• So snow which is 100 kg/m3 is specified as
100/1000, or 10% (of the density of water).
www.avalanche-center.org/Education/glossary
What’s in that snow?
• Like rain, needs a
condensation
nucleus to form
• Then particles and
gases can glom on
as snow forms,
grows, travels