Item: Measurements of snow straigraphy with fmcw radar: comparison with other snow science instruments
Title: Measurements of snow straigraphy with fmcw radar: comparison with other snow science instruments
Proceedings: Proceedings of the 2004 International Snow Science Workshop, Jackson Hole, Wyoming
Authors: H.P. Marshall, M. Schneebeli, G. Koh, M. Matzl, and C. Pielmeier, Institute of Arctic and Alpine Research and Department of Civil, Environmental, and Architectural Engineering, University of Colorado at Boulder, Boulder, CO
Abstract: The stratigraphy of an alpine snowpack is very important for avalanche danger assessment, as well as interpretation of remote sensing measurements for hydrologic purposes. Since spatial variability is often widespread, due mainly to wind, microclimatic and topographic effects, extrapolating point measurements can be difficult. Radar is an advantageous tool tbr studying spatial variability, as large areas can be covered quickly with high resolution. It is non-intrusive so that spatially and temporally continuous measurements can be made throughout the winter. Many previous studies have shown correlations between snowpit and radar measurements, however signal interpretation remains challenging. We compare measurements from a portable high frequency (8-18 GHz) Frequency Modulated Continuous Wave (FMCW) radar with manual snowpit data (including high resolution (5 cm) density samples), SnowMicroPen (SMP) measurements, and Near-Infrared (NIR) photography. Measurements were made made during the 2003-2004 winter at several sites in Davos, Switzerland. We focus on measurements made during one day when all of the instruments successfully collected data. The radar is very sensitive to large density contrasts, therefore ice-lenses, sun-crusts, and other large changes in hardness cause strong reflections. More subtle or less steep density changes, however, which are resolved well with the SnowMicroPen, cause radar signals which are still difficult to interpret. A large degree of spatial variability, at very small length scales (< 10 cm) along radar traverses was apparent, and measurements of this variability were repeatable. These data indicate that the length scale of variability of crusts may be much smaller than we were previously able to measure, due to the minimum horizontal resolution possible with other instruments. Major stratigraphic horizons, however, could be followed along radar profiles and identified in SMP measurements. A very thin hard crust (0.2-0.4 mm) that was continuous caused strong signals that were identifiable in both the SMP and the radar measurements at five different sites along a 10 meter traverse, however other crusts and layer transitions showed different degrees of variability.
Keywords: snowpack, stratigraphy, snowmicropen, danger
Digital Abstract Not Available