APPENDIX C: DETERMINATION OF MICROSTRUCTURAL
VARIABLES BY PLANE SECTION STEREOLOGY
Independent variables measured for snow un-
amples of such variables are measures relating to
dergoing mechanical testing should represent fun-
chains of grains, the number of bonds per grain
damental states or conditions of the snow, includ-
and others.
ing relevant macroscopic and microscopic
Other problems arise because the assumptions
features. Examples of such state variables might
used to convert measurements from plain section
be temperature, density, mean grain size (and or
or thick section images into the desired microstruc-
grain size distribution), mean number and radial
tural parameters are often overly simplified and
cross-sectional area of grain bonds per grain, the
may contain free variables (Gubler 1978a,b; Alley
mean number and length of unsupported chains
1986). In addition, the lack of objective methods
of grains, the mean distance between grains, and
for identifying many structural features in snow
other physically measurable characteristics. While
using plane section and thick section stereology
determining macroscopic state variables can be
has been well recognized (Kry 1975a, Alley 1986,
done reliably, measuring microscopic variables
Dozier et al. 1987).
and determining their significance is problematic.
Stereological methods require relatively large
Attempts to define and determine state vari-
investments in time and effort to construct plane
ables using plane section and thick section stere-
section or thick section samples, obtain good qual-
ology have demonstrated the importance of snow
ity images, and analyze the results. Because of
microstructure on the response of snow to an ap-
these difficulties few experimental studies relat-
plied load (Kry 1975a,b; Gubler 1978a,b; Alley
ing stereological parameters to the deformational
1986; Good 1987; Dozier et al. 1987; Hansen and
behavior of snow have been published since the
Brown 1987; Hansen 1988; Edens and Brown 1991;
work of Voitkovsky et al. (1975) and Kry (1975a,b).
Brown and Edens 1991). However, there are two
Voitkovsky et al. (1975) presented a relationship
difficulties with using stereological methods that
between cohesive force and the number of
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