title: Upward-looking L-band FMCW radar for snow cover monitoring.
abstract: Forecasting snow avalanche danger in mountainous regions is of major importance for the protection of infrastructure in avalanche run-out zones. Inexpensive measurement devices capable of measuring snow height and layer properties in avalanche starting zones may help to improve the quality of risk assessment. We present a low-cost L-band frequency modulated continuous wave radar system (FMCW) in upward-looking configuration. To monitor the snowpack evolution, the radar system was deployed in fall and subsequently was covered by snowfalls. During two winter seasons we recorded reflections from the overlying snowpack. The influence of reflection magnitude and phase to the measured frequency spectra, as well as the influence of signal processing were investigated. We present a method to extract the phase of the reflection coefficients from the phase response of the frequency spectra and their integration into the presentation of the measurement data. The phase information significantly improved the detectability of the temporal evolution of the snow surface reflection. We developed an automated and a semi-automated snow surface tracking algorithm. Results were compared with independently measured snow height from a laser snow-depth sensor and results derived from an upward-looking impulse radar system (upGPR). The semi-automated tracking used the phase information and had an accuracy of about 6 to 8 cm for dry-snow conditions, similar to the accuracy of the upGPR, compared to measurements from the laser snow-depth sensor. The percolation of water was observable in the radargrams. Results suggest that the upward-looking FMCW system may be a valuable alternative to conventional snow-depth sensors for locations, where fixed installations above ground are not feasible.
authors.affiliation: FH JOANNEUM, Department of Electronic Engineering, Kapfenberg, Austria.
authors.forename: Robert
authors.initials: R
authors.lastname: Okorn
authors.affiliation: FH JOANNEUM, Department of Electronic Engineering, Kapfenberg, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Brunnhofer
authors.affiliation: FH JOANNEUM, Department of Electronic Engineering, Kapfenberg, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Platzer
authors.affiliation: Institute of Environmental Physics IUP, University of Heidelberg, Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Heilig
authors.affiliation: WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland.
authors.forename: Lino
authors.initials: L
authors.lastname: Schmid
authors.affiliation: WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Mitterer
authors.affiliation: WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Schweizer
authors.affiliation: Institute of Environmental Physics IUP, University of Heidelberg, Germany ; Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Olaf
authors.initials: O
authors.lastname: Eisen
keywords: FMCW; Radar; Snow stratigraphy; Snowpack monitoring; Surface tracking