10
5
0
10
5
Wind
Speed
Temperature
0
200
Solar
150
100
Relative
50
Humidity
0
1200
Icicles
800
Ice
400
on Wire
0
2
Simple
Model
1
Heat-Balance
Model
0
66
67
Julian Day (GMT)
Figure 8. Time series of the weather conditions and hindcast ice accretions
for the ice storm of 78 March 1990 at the Des Moines airport. The
formation of icicles in the heat-balance model occurs in relatively warm,
humid conditions. In those conditions the results from the heat-balance
model and the simple flux model diverge.
field data can be used to fine-tune the heat-balance
indicates that the modeled ice thicknesses can be
easily extrapolated so that consistent ice thick-
model. Parameters that may have a significant
nesses can be used in the design of structural
effect on the calculated ice load and may need to be
elements with different cross sections. It also shows
adjusted, include a) the 0.64 threshold for incorpo-
that weather data can be used to determine conser-
rating all of the runoff water in the protoicicle, and
vative, but apparently realistic, ice loads using
b) the projected area of the ice accretion that is
assumed to intercept the precipitation flux.
back-of-the-envelope calculations. It will be inter-
The good agreement between the heat-balance
esting to see if this good agreement holds as the
model and the simple flux model is interesting. It
heat-balance model is fine-tuned.
17
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