Abstract
Abstract. Snow water equivalent (SWE) measurements of seasonal snowpack are crucial in many research fields. Yet accurate measurements at a high temporal resolution are difficult to obtain in high mountain regions. With a cosmic ray sensor (CRS), SWE can be inferred from neutron counts. We present the analyses of temporally continuous SWE measurements by a CRS on an alpine glacier in Switzerland (Glacier de la Plaine Morte) over two winter seasons (2016/17 and 2017/18), which differed markedly in the amount and timing of snow accumulation. By combining SWE with snow depth measurements, we calculate the daily mean density of the snowpack. Compared to manual field observations from snow pits, the autonomous measurements overestimate SWE by +2 % ± 13 %. Snow depth and the bulk snow density deviate from the manual measurements by ±6 % and ±9 %, respectively. The CRS measured with high reliability over two winter seasons and is thus considered a promising method to observe SWE at remote alpine sites. We use the daily observations to classify winter season days into those dominated by accumulation (solid precipitation, snow drift), ablation (snow drift, snowmelt) or snow densification. For each of these process-dominated days the prevailing meteorological conditions are distinct. The continuous SWE measurements were also used to define a scaling factor for precipitation amounts from nearby meteorological stations. With this analysis, we show that a best-possible constant scaling factor results in cumulative precipitation amounts that differ by a mean absolute error of less than 80 mm w.e. from snow accumulation at this site.
Highlights
The evolution and amount of seasonal snow accumulation in high mountain regions is a key parameter in many climaterelated research fields such as glaciology or hydrology and climate change impacts, risks and adaptation
Information of the amount of water stored within the annual snowpack in high mountain regions is crucial for avalanche warning (Castebrunet et al, 2014), flood prevention (Jörg-Hess et al, 2015) or mass balance calculations of glaciers (Sold et al, 2013; Pulwicki et al, 2018)
With the cosmic ray sensor (CRS) installed on Plaine Morte, Snow water equivalent (SWE) was measured during two subsequent winter seasons (2016/17 and 2017/18)
Summary
The evolution and amount of seasonal snow accumulation in high mountain regions is a key parameter in many climaterelated research fields such as glaciology or hydrology and climate change impacts, risks and adaptation. Changes in snow accumulation in mountain areas caused by climate change are expected to have major impacts on water supply for adjacent lowlands (Barnett et al, 2005; Viviroli et al, 2007, 2011), hydropower production (Ali et al, 2018) or winter tourism (Marty et al, 2014; Sturm et al, 2017). The cold and windy conditions pose the main challenge for accurate measurements (Sevruk et al, 2009; Rasmussen et al, 2012; Kinar and Pomeroy, 2015).
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