Laboratory Test of Snow Wetness Influence on Impulse Radar Amplitude Damping

TitleLaboratory Test of Snow Wetness Influence on Impulse Radar Amplitude Damping
Publication TypeConference Proceedings
Year of Conference2007
AuthorsGranlund, N., Gustafsson D., Feiccabrino J., and Lundberg A.
Conference Name75th Annual Western Snow Conference
Series TitleProceedings of the 75th Annual Western Snow Conference
Date PublishedApril 2007
PublisherWestern Snow Conference
Conference LocationKailua-Kona, HI
KeywordsGround penetrating radar, SWE, liquid water, electric conductivity, dielectric constant, snow wetness

The two-way travel time of impulse (ground penetrating) radar operated from helicopters and snowmobiles is used to determine snow water equivalent for annual snowpacks, glaciers and polar ices. Presence of liquid water in a snowpack creates uncertainties, which for a typical snowpack with 5% (by volume) liquid water can lead to overestimation of the snow water equivalent by about 20%. It would therefore be helpful if the radar could also be used to determine snow wetness. Damping of wave amplitude varies with electric conductivity and the dielectric constant. The dielectric constant can be calculated using the radar pulse travel time and knowledge about the depth, hence studying amplitude damping should reveal how conductivity depends on snow wetness. A laboratory test was set up to study the relationship between conductivity and wetness. Three sets of measurements, two with old and one with new-fallen snow, were made on initially dry one-meter thick snowpacks contained in a plywood box with cross-section area about 0.5m2. Water was stepwise added to the box in between radar measurements. A tentative relationship between conductivity and wetness was found, but further tests including studies of the effect of variations in snow salt concentrations and in experiment design are needed to assess the generality of the relationship.