Observations of diurnal melt-freeze events using time domain reflectometry (TDR) in sesonal snowpack

Understanding seasonal snowpack characteristics is essential for avalanche forecasting and water resource management. As technology advances, instruments continue to be developed to study seasonal snowpack characteristics. These instruments range from ultrasonic snow depth sensors to microwave sensors flown on satellites to sensors based on snow's electrical properties. Few studies have looked at time domain reflectometry's (TDR) applicability to measure dry snow density and daily fluctuations in liquid water content due to diurnal melt-freeze cycles. This study aims to build on previous TDR studies of seasonal snowpack and assess the effectiveness of a TDR system to monitor diurnal changes in snowpack liquid water content. Results are from a test springtime snowpit in Alta, UT. Measured snow densities range from 108kg/m3 to 414kg/m3 with a measurement error of 4%. Through the comparison of manually measured densities and dielectric values from the TDR, insight into the TDR's applicability to density measurements is gained. Daily fluctuations in the TDR probe dielectric measurements indicate the TDR's applicability to study diurnal melt-freeze cycles. Correlation of diurnal dielectric constant measurements with solar radiation and air temperature suggest that the TDR is able to monitor effects of energy fluxes in the snowpack associated with energy received due to daytime temperatures and shortwave radiation. Calculated liquid water content varied from 1.0 to 2.5 vol. % during diurnal fluctuations, consistent with ranges from previous studies indicating TDR's applicability to monitor liquid water content in a wet snowpack during melt-freeze transitions.