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 8cm 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.
Highlights
Continuous upward-looking radar has proven to be a successful technique for monitoring the temporal evolution of snow stratigraphy
In order to compare the snow height determined with the radar with values from the laser, we assumed a constant wave speed of v = 0.23 m/ns (Mitterer et al, 2011a) which for dry snow corresponds to a bulk density of 360 kg/m3 (Kovacs et al, 1995)
We developed a low-cost upward-looking frequency modulated continuous wave (FMCW) radar, which allowed for continuous monitoring of the snow cover
Summary
Continuous upward-looking radar has proven to be a successful technique for monitoring the temporal evolution of snow stratigraphy This specific radar setup operates from underneath the snowpack at a fixed location and records quasi-continuously snow-related signal reflections over the course of a season (Gubler and Hiller, 1984; Gubler and Weilenmann, 1987; Heilig et al, 2009, 2010; Mitterer et al, 2011a; Schmid et al, 2014). Heilig et al (2009, 2010) presented feasibility studies on using impulse radar systems (upGPR) from beneath the snowpack with vertically moving antennas to distinguish system related noise from snowpack-related reflection signals Applying such a system, Mitterer et al (2011a) showed that it is feasible to determine the snow height during dry-snow conditions and to estimate the bulk volumetric liquid water content (θW) as well as to monitor the position of the wetto-dry transition over an entire season. It operated during two winter seasons and recorded reflections from the overlaying snowpack
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
