WMOD00389

• Title: Winter Precipitation, Snowpack and Atmospheric Conditions in the Southern Canadian Rockies
• Date: 1/1/1983
• Country: Canada
• Weather Modification - Doc Type: Report

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Page 6

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50

A"

29 Years of Record

10

Snowfall

40
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CD
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g 30
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CD
Ol
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CD
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Curve lor > 0 cm

Curve lor > 2 cm

Curve lor > 4 cm

N

o

F

Curve lor > 8 cm
Curve lor > 16 cm
Curve lor > 32 cm
A

o
s

o

J

M

Month

Figure 3. Percentage frequency of occurrence of snowfall
exceeding given values as a function of month for
Lake Loui see "A" indicates there was snowfall
greater than zero centimetres 43% of the time in
December.

l

To demonstrate differences in seasonal snowfall between stat.ions
east and west of the Divide, a seasonal distribution index is used. For
a given daily snowfall, this index is equal to twice the sum of its
percentage frequenci es for March and April, mi nus the sum of the
percentage frequencies for November, December, January, and February.
Thus, this. index is positive for stations which experience more of the
given snowfall event in the spring, and negative for stations which
experience these events in late fall and mid-win~er. A contoured map of
this index for daily snowfall exceeding eight centimetres is shown in
Figure 4. The index areal pattern for events exceeding 16 centlmetres
per day (not shown) is similar. Apparently, seasonal distribution of
moderate to heavy daily snowfall in the southern Canadian Rockies has
two principal forms. West of and over the Continental Divide, such
snowfalls occur mainly in midwinter; while east of the Divide, these
snowfalls occur more frequently in spring.

The contribution of daily snowfall amounts to the total sno~,fall
from September through April for Lake Louise is shown in Figure 5.
Plots of this kind were produced for all 24 climate stations. When the
shapes of such curves differ from station to station, differences in
snowfall climatology are implied.

Figure 6 presents the percentage contribution of daily snowfall
events exceeding eight centimetres to the total September through April
snowfall. Daily snowfalls of more than eight centimetres per day are
responsible for less than 40% of the seasonal total in the Rocky
Mountain Trench but more than 60% over mountainous areas near the
Continental Divide. Similarly, events exceeding 16 centimetres per day
indicate only a 10% contribution in the Trench and a 20 to 30%
contribution over higher terrain near the Divide.