In-situ monitoring of the time evolution of the effective thermal conductivity of snow

We report on a 3-month long time series of in-situ measurements of the effective thermal conductivity (keff) of snow at 6 heights in an Alpine snowpack in the Mont-Blanc mountain range, France, at an altitude of 2400 m. Measurements were carried out automatically every 2 days using heated-needle probes embedded in the snowpack. The experimental procedure used is presented in detail and demonstrates the applicability of single heated-needle probes for the evaluation of keff in snow, both for long-term measurements within the snowpack and occasional use in the field. Results based on 139 automatically collected data show keff values ranging between 0.04 and 0.35 W m− 1 K− 1, and a consistent pattern of effective thermal conductivity increase throughout the measurements campaign. The temporal rate of change of keff varies up to 0.01 W m−1 K− 1day− 1, with maximum values just after snowfall.