Snow liquid water content measurement using an open-ended coaxial probe (OECP)

Abstract

AbstractAccurately determining the evolution of the snow liquid water content (LWC) through the snowpack remains a challenge in avalanche risk assessment and microwave snow emission and backscattering modeling. The percolation of rain and/or snowmelt water can lead to instability in the snowpack and increase avalanche risk. Liquid water percolation schemes have recently been integrated into snow metamorphism models, but they require validation. Snow property retrievals from microwave observations (satellite and ground-based) are challenging in wet snow conditions because of the reduced penetration depth, and thus a better quantification of the effect of snow liquid water content on microwave signals would improve satellite products. This study presents a new open-ended coaxial probe (OECP) suitable for in situ snow LWC measurements at L-band frequencies (1–2 GHz). The precision of ±1% of the OECP compared to calorimetric measurements is similar to other available instruments tested (Snow Fork and Time Domain Reflectometry). The OECP is capable of quantifying the LWC of thin percolation accumulation layers because of its small probed volume, while other instruments fail to do because of their bigger probed volume due to their lower frequencies used.