Estimated Snow Parameters for Vehicle Mobility Modeling
in Korea, Germany and Interior Alaska
TIMOTHY HORRIGAN AND ROY E. BATES
INTRODUCTION
Snowfall and snow density are two important
modeling standpoint, since one of the most impor-
factors for mobility modeling and simulation.
tant objectives of such modeling is to define a
plausible worst-case scenario.)
Knowledge of the regional distribution of these
Snow density was one of several properties of
parameters would also contribute materially tow-
the snowpack investigated during the study. This
ard the solution of numerous other winter prob-
was measured by means of density tubes inserted
lems. This report is a result of a request to CRREL
from the Waterways Experiment Station (WES) in
into various layers of the snowpack, and a weight-
Vicksburg, Mississippi, for realistic estimated val-
ed average of the density tube values was used to
ues of the regional variation of snow cover. These
represent the overall density of the snowpack.
values are needed for verifying and validating
These weighted-average snow density values do
WES's mobility prediction models.
not take into account the densities of the ice crusts
and ice lenses within the snowpack. However, the
Three areas of the Northern Hemisphere were
contribution of such ice inclusions to the overall
selected to test and validate current prediction
density should presumably be minor.
algorithms residing within the mobility models:
The average snow density at the nine test sites
interior Alaska, central and southern Germany,
at Fort Greely was 0.233 g/cm3, which represents a
and Korea north of the 38th parallel. The snow
parameters needed are the average and worst-
medium snow density. The lightest snow tended
case monthly and winter snow density (g/cm3)
to be found early in the season and at sites with
and the accumulated snow depth (cm). To accom-
vegetation cover. (Uncovered open areas had
plish this task, average and worst-case values
denser snow because of snow drifts from wind
were estimated by gleaning results from many
packing.) The lightest measured density of the en-
earlier published reports. Much of the data was
tire snowpack came on November 28 at the forest-
selected from a CD-ROM called International Sta-
ed site, when the average snow density was only
0.140 g/cm3.
tion Meteorological Climate Summary (ISMCS) (U.S.
Navy, U.S. Air Force, U.S. Dept. of Commerce
The top layer of the deep snowpack is the most
1992).
important from a mobility modeling viewpoint
(since vehicles travel over the top of the snow).
The newer snow in the top layer is much lighter
INTERIOR ALASKA
than the older snow in the lower layers. Most top-
The results of a study completed at Fort Greely
layer density values were on the order of 0.100
g/cm3, but values as low as 0.038 g/cm3 and as high
by Bilello et al. (1970) are a good starting point for
as 0.424 g/cm3 were observed.
estimating the snow conditions in interior Alaska.
The terrain and climate at Fort Greely is typical of
The worst case for mobility modeling purposes
interior Alaska in general. This study dealt prima-
is most likely to have average snow densities from
approximately 0.350 to 0.500 g/cm3 when travers-
rily with field tests conducted in the winter of
ing upslope. Above 0.500 g/cm3 there would be
196667, which was unusually snowy. (The un-
usually high snowfall is useful from a mobility
little or no vehicle sinkage, and trafficability
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