Characterization of wet snow complex permittivity using resonant probes: Methodology and in situ applications

Abstract

This study presents a methodology for measuring complex electric permittivity of snow in the 200 MHz–2 GHz frequency range using resonant probes connected to a portable vector network analyzer (VNA). The methodology was applied during two field campaigns performed in the Alps in June and July 2024 under dense wet snow conditions. Snow liquid water content (LWC) and density were retrieved from dielectric measurements and compared with reference values obtained by melting calorimetry and gravimetric sampling, respectively. Two in situ protocols were adopted: a vertical profiling approach in June and a co-located acquisition protocol in July, in which dielectric, calorimetric and gravimetric measurements were performed at the same sampling points. Complex permittivity values measured by the VNA were compared with predictions from different models available in the literature, using reference LWC and density values as inputs. The results indicate that the Sihvola and Tiuri model provides one of the most consistent overall agreements with the experimental data and highlights the importance of co-located acquisitions for reducing the impact of spatial heterogeneity. The proposed methodology represents a field-deployable evolution of traditional snow dielectric measurements, providing encouraging results for LWC estimation while indicating the need for further validation of density retrievals.