International Symposium on Mitigative Measures against Snow ...

<strong>International</strong> <strong>Symposium</strong> on Mitigative Measures against Snow Avalanches
Egilsstaðir, Iceland, March 11–14, 2008
Figure 1. SM4 attached to a snowdepth-pole.
The SM4 measures snow depth by identifying thermistors buried in the snow based on the
damping of temperature fluctuations that is caused by the snowpack compared with
temperature fluctuations in air.
The IMO has located series of snow depth poles in many starting areas above settlements. The
purpose is to be able to measure the snow depth manually from below with a theodolite.
Attaching SM4 to such poles has been an easy way of installing them.
PRELIMINARY RESULTS FROM THE FIRST WINTER
The Icelandic Meteorological Office (IMO) has used ultrasonic snow depth sensors for some
years for monitoring snow depth in avalanche starting zones. Those instruments provide
important data for the avalanche warning service of IMO. However, due to their sensitivity to
icing and snowdrift, they sometimes do not work for long periods, especially during
avalanche cycles when reliable measurements are particularly important.
The initial plan of POLS and IMO for the winter 2006−2007 was to operate a SM4 snow
sensor together with an ultrasonic sensor in three starting areas. The SM4 was attached to the
towers that keep the ultrasonic sensors in place. However, the towers went down in two of
those areas due to strong winds. Therefore, the avalanche starting area in Traðargil above
Bolungarvík was the only location providing usable data during the winter 2006−2007.
The SM4 unit was connected to the Campbell communication equipment within IMO’s
automatic weather station in Bolungarvík. Also, the SM4 sends the data through the GSM
system and to the Internet.
152 The SM4 snowpack temperature and snow depth sensor