Abstract
Satellite-based radar measurement are increasingly important for the
detection of avalanche activity and the characterization of the snow
cover properties on a regional scale. However, they operate with a
temporal resolution of several days, which can detect major avalanche
cycles, but changes induced by melt-freeze cycles, rain-on-snow events,
snow fall, avalanche events and alike are more challenging to deduce. We
present a ground-based radar system that measured the snow cover of a
complete mountain slope during the winter season 2020-2021 with an
hourly resolution and records flowing avalanches with 50Hz sampling. The
observed mountain in Austria is a steep slope of southern aspect with
avalanche control measures and corresponding artificial avalanche
releases after every significant snow fall. We observe significant
changes in the radar backscatter signal on different time scales: The
rapid avalanche movement is analyzed by means of moving target
identification filtering which suppresses the background signal from the
resting snow cover, but enhances the rapid signal variations of the
flow. Avalanche activity and their deposits can be identified by
comparing the radar signal before and after avalanche events. And longer
variations like diurnal changes in the backscatter signal are associated
with meteorological influences, such as absorption of solar radiation
and warming of the snow cover. We analyze the backscatter signal in
terms of the flowing avalanches, immediate changes from fresh avalanche
deposits and put these into relation to the magnitude of backscatter
changes caused by the meteorological factors. We find that the
backscatter signal of avalanche deposits can fluctuate significantly
across the runout area, which is in accordance with satellite-based
avalanche detection procedures that cluster deposits as regions with
large radar signal variation. In the future, the developed radar may be
used as ground-truth to support snow cover characterization with
satellite-based radar missions.