I n s t r u m e n t s

a n d

M e t h o d s

Photo 1: View of a part
ofthe apparatus above
the "Col du Lac Blanc"
location.

Photo 2: Photograph of
a heavy frost period.

sentedbythe 7sensormeasurements inordertoobtain
consistent dataanda general viewof the snow profile along
the slope. This processing follows four steps: afirst smooth-
ing of extreme data, checkingof real presenceof at least 4
sensor'sdata,missingvaluesarereplaced byamoving
averagemethod (only if no more than one value is missing
after another) andafinal smoothing by theprevious method
forthe whole period (figure 4).
In addition to this processing, some statistical parameters
can be analysed. For example, it is interesting to compare
each sensordata with the smoothing average in orderto

display theirparticularity. On the otherhand,the stand-
ard-deviation of the snow-depth profile can be calculated
ateach timeinterval.Itappearsthat when thestandard
deviation is high, the behaviour of the sensors is obviously
different.Thesnowsurface doesnotundergothesame
modifications all along the slope.

Focus on a blowing snow period

The major aim of this test is to get information on the cor-

Figure. 2: scheme of our "profileur" installation.

Figure3 : synoptic diagram of the apparatus.

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