Towards automated ‘Ground truth’ snow measurements—a review of operational and new measurement methods for Sweden, Norway, and Finland

Abstract

Abstract:Manual snow measurements are becoming increasingly expensive and climate-change-imposed snow alterations are affecting run-off and frost patterns; snow observations are included in run-off modelling, making reliable snow observations of utmost importance. Multiple new and modified ground-based techniques for monitoring snow depth, density, snow water equivalent (SWE), wetness, and layering have been tested over the last decade, justifying a review of such methods. Techniques based on snow mass, electrical properties, attenuation of radioactivity, and other miscellaneous properties are reviewed. The following sensors seem suitable for registration of temporal variations: ultrasonic (depth) and terrestrial laser scanning (depth), several snow pillows at the same location (SWE), Cold Regions Research and Engineering Laboratory/Natural Resources Conservation Service weighing sensor (SWE), Snowpower (depth, density, SWE, and wetness), active and passive (cosmic) -ray attenuation (SWE), and adjusted time domain reflectometry probes (density and wetness). Ground-penetrating radar (GPR) is, depending on the design and operation modes, suitable for different purposes; when arrays of antennas are pulled by a snowmobile, the technique is suitable for monitoring of spatial variations in depth, density, and SWE for dry snow. Techniques are under development, which will hopefully improve the accuracy for wet snow measurements. Frequency-modulated continuous wave GPRs seem fit for measurement of snow layering. Some suggested techniques are not operational yet.

Lidar snow cover studies on glaciers in the Ötztal Alps (Austria): comparison with snow depths calculated from GPR measurements

“…Sevruk, 1985;Lundberg et al, 2010) and only insufficient data are available for model calibration and validation of the snow depth distribution on the catchment scale. Thereby the spatial representativeness of individual measurements of snow depths and snow densities derived from direct measurements in terms of snow probings and snow pits (Fierz et al, 2009) and from automatic measurement systems (Lundberg et al, 2010) has to be questioned .…”

“…Rott and Markl, 1989;Hall et al, 2002;Schöber et al, 2010), to date no snow depth or SWE can be obtained from satellite data in a high spatial resolution of at least 100 m (Lundberg et al, 2010;Nolin, 2011), which is required to capture the spatial variability of the mountain snow cover (Blöschl, 1999). In contrast, laser altimetry was recognized to be useful to derive small scale snow depth distributions in mountain areas (Deems et al, 2013).…”

“…In a snowpack, r is a function of the mixing ratio between ice, air and liquid water (e.g. Lundberg et al, 2006). However, the proportion of liquid water in a wet snowpack can alter r and hence the signal velocity in a significant way (Frolov and Macheret, 1999;Sundström et al, 2012).…”

Utilización de técnicas de láser escáner terrestre en la monitorización de procesos geomorfológicos dinámicos: el manto de nieve y heleros en áreas de montaña

“…Sin embargo la principal ventaja del sistema es la adquisición de datos a larga distancia con una elevada resolución espacial, por lo que se dispone de millones de puntos distribuidos en prácticamen-te la totalidad de las zonas de estudio adquiridos desde tan solo dos posiciones de escaneo. Es precisamente esta característica la que hace que la tecnología láser escáner resulte ideal para trabajos de monitorización del manto de nieve para distancias de 500 m y superiores (Lundberg et al, 2008).…”

“…), la estabilidad del sistema o el cambio en las condiciones del manto de nieve (Prockop, 2008). No obstante si se minimizan en la medida de lo posible estos problemas, aplicando rigurosamente la metodología de trabajo seguida en el presente estudio, los láser escáner terrestres de larga distancia son la tecnología con mejores resultados de medición directa del espesor de nieve y hielo para distancias de alrededor de 500 m (Lundberg et al, 2008) e incluso superiores a 2000 m con una error en la medición de espesor inferior a 20 cm en condiciones óptimas de trabajo (Prockop, 2009). …”