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8. Multi-sensor analysis of monthly gridded snow precipitation on alpine glaciers

Author

Gugerli, Rebecca, Guidicelli, Matteo, Gabella, Marco, Huss, Matthias, and Salzmann, Nadine

Abstract

Accurate and reliable solid precipitation estimates for high mountain regions are crucial for many research applications. Yet, measuring snowfall at high elevation remains a major challenge. In consequence, observational coverage is typically sparse, and the validation of spatially distributed precipitation products is complicated. This study presents a novel approach using reliable daily snow water equivalent (SWE) estimates by a cosmic ray sensor on two Swiss glacier sites to assess the performance of various gridded precipitation products. The ground observations are available during two and four winter seasons. The performance of three readily-available precipitation data products based on different data sources (gauge-based, remotely-sensed, and re-analysed) is assessed in terms of their accuracy compared to the ground reference. Furthermore, we include a data set, which corresponds to the remotely-sensed product with a local adjustment to independent SWE measurements. We find a large bias of all precipitation products at a monthly and seasonal resolution, which also shows a seasonal trend. Moreover, the performance of the precipitation products largely depends on in situ wind direction during snowfall events. The varying performance of the three precipitation products can be partly explained with their compilation background and underlying data basis.

Published
2021

12. Girls on Ice Switzerland – using immersion to inspire interest in science

Author

Naegeli, Kathrin, primary, Bouscary, Chloé, additional, Coch, Caroline, additional, Fridrich, Anja, additional, Gugerli, Rebecca, additional, Habermann, Marijke, additional, Hellmann, Lena, additional, Kronenberg, Marlene, additional, Langhammer, Lisbeth, additional, Mollaret, Coline, additional, Schaub, Yvonne, additional, Schwikowski, Margit, additional, Wee, Julie, additional, and Wenner, Michaela, additional

Published
2020
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13. Continuous and autonomous snow water equivalent measurements by a cosmic ray sensor on an alpine glacier

Author

Gugerli, Rebecca, Salzmann, Nadine, Huss, Matthias, Desilets, Darin, Gugerli, Rebecca, Salzmann, Nadine, Huss, Matthias, and Desilets, Darin

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.

Published
2020

18. Multi-sensor analysis of monthly gridded snow precipitation on alpine glaciers

Author

Gugerli, Rebecca, Guidicelli, Matteo, Gabella, Marco, Huss, Matthias, and Salzmann, Nadine

Subjects
13. Climate action
Abstract

Accurate and reliable solid precipitation estimates for high mountain regions are crucial for many research applications. Yet, measuring snowfall at high elevation remains a major challenge. In consequence, observational coverage is typically sparse, and the validation of spatially distributed precipitation products is complicated. This study presents a novel approach using reliable daily snow water equivalent (SWE) estimates by a cosmic ray sensor on two Swiss glacier sites to assess the performance of various gridded precipitation products. The ground observations are available during two and four winter seasons. The performance of three readily-available precipitation data products based on different data sources (gauge-based, remotely-sensed, and re-analysed) is assessed in terms of their accuracy compared to the ground reference. Furthermore, we include a data set, which corresponds to the remotely-sensed product with a local adjustment to independent SWE measurements. We find a large bias of all precipitation products at a monthly and seasonal resolution, which also shows a seasonal trend. Moreover, the performance of the precipitation products largely depends on in situ wind direction during snowfall events. The varying performance of the three precipitation products can be partly explained with their compilation background and underlying data basis., Advances in Science and Research, 18

19. Continuous and autonomous snow water equivalent measurements by a cosmic ray sensor on an alpine glacier

Author

Gugerli, Rebecca, Salzmann, Nadine, Huss, Matthias, Desilets, Darin, Gugerli, Rebecca, Salzmann, Nadine, Huss, Matthias, and Desilets, Darin

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.

20. Evaluation of continuous and autonomous snow water equivalent measurements by a cosmic ray sensor on a Swiss glacier.

Author

Gugerli, Rebecca, Salzmann, Nadine, Huss, Matthias, and Desilets, Darin

Subjects
*COSMIC rays, *GLACIERS, *MASS budget (Geophysics), *SNOW, *ICE sheets, *SNOW accumulation, *FLOOD control, *HUMIDITY
Abstract

Snow water equivalent (SWE) measurements are crucial in many research fields such as avalanche prediction, flood prevention, runoff simulation, or ice sheet and glacier mass balance modeling. Despite the importance of accurate SWE measurements, continuous and autonomous measurements are difficult to obtain in high mountain regions at a high temporal resolution.The cosmic ray sensor allows inferring SWE directly from neutron counts. Here, we present the analyses of continuous SWE measurements on a Swiss glacier (Glacier de la Plaine Morte). The measurements cover the two winter seasons of 2016/17 and 2017/18 which have been highly different in terms of amount and timing of snow accumulation. During these two winter seasons, the cosmic ray sensor has measured SWE reliably, and thus, we consider it a very robust method to monitor SWE at remote high alpine sites.By combining the SWE values with snow depth measurements, we calculate the mean snow density of the snowpack at a daily resolution. The autonomous measurements of SWE, snow depth and density lie within ±10% of manual field measurements, which were obtained with snow pits and snow probings four, respectively six, times during the two winter seasons. In a first application, we make use of the daily resolution to break down the winter season into days which are dominated by accumulation (solid precipitation, wind drift), ablation (wind drift, melt) or densification. Then, we determine the prevailing meteorological conditions (temperature, wind speeds, wind direction, and relative humidity) of these periods. Even though the two winter seasons were different in terms of amount and time evolution of SWE, the number of days with accumulation and densification processes remain similar for both winters.In a second application, we compare daily SWE amounts to precipitation amounts of three nearby low-elevation stations in close vicinity to the glacier. The ratio of snow accumulation on the glacier over precipitation observed at the nearby station is only consistent for one station over different time scales (daily and monthly). For the other two stations, the variability is higher even though they are located at a similar distance to the glacier. [ABSTRACT FROM AUTHOR]

Published
2019

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