DATA AVAILABILITY STATEMENT
Used data is freely available in:https://zenodo.org/record/2549310#.XErjW5VYZaQ
REFERENCES
Beaumont, R.T. & Work, R.A. (1963). Snow sampling results from three samplers. Hydrological Sciences Journal , 8(4), 74-78. doi 10.1080/02626666309493359
Beaumont, R.T. (1967). Field Accuracy of Volumetric Snow Samplers at Mt. Hood, Oregon. Physic of Snow and Ice Proceedings, 1(2), 1007-1013.
Berezovskaya, S. & Kane, D.L. (2007). Strategies for measuring snow water equivalent for hydrological applications: Part 1,accuracy of measurements. Proceedings of 16th Northern Research Basin Symposium , Petrozavodsk, Russia, 22–35.
Bindon, H.H. (1964). The design of snow samplers for Canadian snow surveys. In Proceedings of the 21st Annual Meeting of the Eastern Snow Conference, Utica, New York, 23–28.
Boon S., Davis R., Bladon K. & Wagner M. (2009). Comparison of Field Techniques for Measuring Snow Density at a Point. Watershed Management Bulletin, 12 (2), 7-12.
Bühler, Y., Adams, M. S., Bösch, R., & Stoffel, A. (2016). Mapping snow depth in alpine terrain with unmanned aerial systems (UASs): potential and limitations. The Cryosphere , 10, 1075-1088, doi.org/10.5194/tc-10-1075-2016.
Church, J. E. (1933), Snow surveying: Its principles and possibilities.Geogr. Rev., 23(4), 529–563, doi:10.2307/209242.
Dixon, D.& Boon S. (2012). Comparison of the SnowHydro snow sampler with existing snow tube designs. Hydrol. Process. , 26, 2555-2562, 10.1002/hyp.9317
Deems, J.S., Painter T.H.& Finnegan D.C. (2013). Lidar measurement of snow depth: a review. Journal of Glaciology , 59 (215), 467-479.
Doesken, N.J.& Judson, A. (1996). A guide to the science, climatology, and measurement of snow in the United States. Ed. Colorado State University- Fort Collins (US), 87 pp.
Dong, C. (2018). Remote sensing, hydrological modeling and in situ observations in snow cover research: A review. Journal of Hydrology , 561, 573-583.
Farnes, P.F., Goodison, B.E., Peterson, N.R.& Richards, R.P. (1982). Metrication of Manual Snow Sampling Equipment. Final Report Western Snow Conference, Spokane, Washington 106 p.
Fassnacht, S.R., Heun, C.M., López-Moreno J.I.& Latron, J. (2010). Variability of Snow Density Measurements in the Rio Esera Valley, Pyrenees Mountains, Spain. Cuadernos de Investigación Geográfica (Journal of Geographical Research) , 36(1), 59-72.
Fassnacht, S.R., Brown, K.S.J., Blumberg, E.J., López-Moreno, J.I., Covino, T.P., Kappas, M., Huang, Y., Leone, V., & Kashipazha A.H. (2018). Distribution of snow depth variability. Frontiers of Earth Science , 12(4), 10 pages [doi: 10.1007/s11707-018-0714-z].
Fernandes, R., Prevost, C., Canisius, F., Leblanc, S. G., Maloley, M., Oakes, S., Holman, K., & Knudby, A. (2018). Monitoring snow depth change across a range of landscapes with ephemeral snowpacks using structure from motion applied to lightweight unmanned aerial vehicle videos, The Cryosphere , 12, 3535-3550. https://doi.org/10.5194/tc-12-3535-2018.
Fierz, C., Armstrong, R. L., Durand, Y., Etchevers, P., Greene, E., McClung, D. M., Nishimura, K., Satyawali, P. K. and Sokratov, S. A. (2009). The International Classification for Seasonal Snow on the Ground, UNESCO-IHP, Paris, France. [online] Available from:http://www.cryosphericsciences.org/outcomes/snowClassification/snowclass_2009-11-23-tagged-highres.pdf
Freeman, T.G. (1965). Snow survey samplers and their accuracy. InProceedings of the 22nd Annual Meeting of the Eastern Snow Conference , Hanover, New Hampshire, 1–10.
Goodison B.E., Glynn J.E., Harvey K.D. & Slater J.E. (1987) Snow Surveying in Canada: A Perspective. Canadian Water Resources Journal , 12, 27-42, DOI: 10.4296/cwrj1202027.
Haberkorn, A., Helmert, J., Leppänen, L., López-Moreno, J.I., Pirazzini, R. (2019). European Snow Booklet, Haberkorn, A. (Ed.), 363 pp. doi:10.169904/envidat.59.
Helmert, J.; Şensoy Şorman, A.; Alvarado Montero, R.; De Michele, C.; de Rosnay, P.; Dumont, M.; Finger, D.C.; Lange, M.; Picard, G.; Potopová, V.; Pullen, S.; Vikhamar-Schuler, D.; Arslan, A.N. Review of Snow Data Assimilation Methods for Hydrological, Land Surface, Meteorological and Climate Models: Results from a COST HarmoSnow Survey. Geosciences 2018, 8, 489.
INTERACT Station Catalogue (2015). Eds.: Elger, K., Opel, T., Topp-Jørgensen, E., Hansen, J., Tairova, Z. and Rasch, M. DCE - Danish Centre for Environment and Energy, Aarhus University, Denmark. 305 p. (p. 72-75)
Jonas T., Marty C. & Magnusson, J. (2009). Estimating the snow water equivalent from snow depth measurements in the Swiss Alps. J. Hydrol. , 378, 161-167.
Kinar N. J. & Pomeroy J.W. (2015). Measurement of the physical properties of the snowpack, Rev. Geophys. , 53, 481-544. doi:10.1002/2015RG000481.
Komarov A.Y., Seliverstov Y.G., Grebennikov P.B. & Sokratov S.A. (2019). Spatial variability of snow water equivalent – the case study from the research site in Khibiny Mountains, Russia. J. Hydrol. Hydromech ., 67 (1), 110–112. doi: 10.2478/johh-2018-0016
Leppänen, L., Kontu, A. & Pulliainen, J. (2018) Automated Measurements of Snow on the Ground in Sodankylä. Geophysica 53(1), 43-62.
Libois, Q., Picard, G., Arnaud, L., Morin, S., & Brun, E. (2014), Modeling the impact of snow drift on the decameter-scale variability of snow properties on the Antarctic Plateau. J. Geophys. Res. Atmos. , 119 (11),662–11,681, doi:10.1002/2014JD022361.
López Moreno, J.I., Fassnacht, S.R., Beguería, S. & Latron, J. (2011). Variability of snow depth at the plot scale: implications for mean depth estimation and sampling strategies. The Cryosphere, 5, 617-629.
López-Moreno, J.I., Fassnacht, S., Latron, J., Musselman, K., Morán-Tejeda, E. & Jonas, T. (2013). Small scale spatial variability of snow density and depth over complex alpine terrain: implications for estimating snow water equivalent. Advances in Water Research, 55, 40-52.
Kronholm, K., Schneebeli, M. and Schweizer, J. (2004). Spatial variability of micropenetration resistance in snow layers on a small slope. Annals of Glaciology , 38(1), 202–208. doi:10.3189/172756404781815257, 2004.
Marr, J. C. (1940). Snow Surveying. Soil Conservation Service, United States Department of Agriculture, Miscellaneous Publication No. 380, Washington D.C.
Marty, C. (2018). Recent Evidence of Large-Scale Receding Snow Water Equivalents in the European Alps. Journal of Hydrometeorology, 18, 1021-1031.
McCreight JL & Small E.E. (2014). Modeling bulk density and snow water equivalent using daily snow depth observations. The Cryosphere,8, 521-536. doi.org/10.5194/tc-8-521-2014, 2014.
Nitu R., Roulet Y.-A., Wolff M., Earle M., Reverdin A., Smith C., Kochendorfer J., Morin S., Rasmussen R., Wong K., Alastrué J., Arnold L., Baker B., Buisán S., Collado J. L., Colli M., Collins B., Gaydos A., Hannula H.-R., Hoover J., Joe P., Kontu A., Laine T., Lanza L., Lanzinger E., Lee G.W., Lejeune Y., Leppänen L., Mekis E,. Panel J.-M., Poikonen A., Ryu S., Sabatini F., Theriault J., Yang D., Genthon C., van den Heuvel F., Hirasawa N., Konishi H., Nishimura K., Senese A. (2018). Solid Precipitation Intercomparison Experiment 2012-2015, WMO Instruments and Observing Methods Report No. 131.
Pirazzini, R., Leppänen, L., Picard, G., Lopez-Moreno, J.I., Marty, C., Macelloni, G., Kontu, G., von Lerber, A., Melih-Tanis, C., Schneebeli, M., de Rosnay, P. & Arslan, A.N. (2018) European in-situ snow measurements: Practices and purposes. Sensors, 18, 7.
Peterson, N.R. & Brown, A.J. (1975). Accuracy of snow measurements.Proceedings of the Western Snow Conference 577-586 .
Picard, G., Arnaud, L., Panel, J.M. & Morin, S. (2016). Design of a scanning laser meter for monitoring the spatio-temporal evolution of snow depth and its application in the Alps and in Antarctica, The Cryosphere , 10, 1495-1511. doi.org/10.5194/tc-10-1495-2016, 2016
Proksch, M., Löwe, H., & Schneebeli, M. (2015). Density, specific surface area, and correlation length of snow measured by high-resolution penetrometry, Journal of Geophysical Research: Earth Surface , 120(2), 346–362. doi.org/10.1002/2014JF003266.
Proksch, M., Rutter, N., Fierz, C., & Schneebeli, M. (2016). Intercomparison of snow density measurements: bias, precision, and vertical resolution, The Cryosphere , 10, 371-384. doi.org/10.5194/tc-10-371-2016.
Revuelto, J., López-Moreno, J.I., Azorin-Molina, C. & Vicente-Serrano, S.M. (2014). Topographic control on snowpack distribution in a small catchment in the central Pyrenees: intra- and inter-annual persistence.The Cryosphere, 8 (5), 1889-2006.
Schneebeli, M., & Johnson, J. B. (1998). A constant-speed penetrometer for high resolution snow stratigraphy. Ann. Glaciol . 26, 107–111.
Stähli, M., Stacheder, M., Gustafsson, D., Schlaeger, S. & Schneebeli, M. 2004. A new in situ sensor for large-scale snow-cover monitoring.Ann. Glaciol 38: 273–278.
Stuefer S., Kane D.L. & Liston G.L. (2013). In situ snow water equivalent observations in the US Arctic. Hydrology Research , 44 (1), 21-34.
Sturm M., Taras B., Liston G.E., Derksen C., Jonas T. & Lea J. (2010). Estimating snow water equivalent using snow depth data and climate classes. J. Hydrometeorol ., 11 (6), 1380-1394.
Takala, M., Luojus, K., Pulliainen, J., Derksen, C., Lemmetyinen, J., Kärnä, J.P., Koskinen, J., & Bojkov, B. (2011) Estimating northern hemisphere snow water equivalent for climate research through assimilation of space-borne radiometer data and ground-based measurements. Remote Sens. Environ ., 115 (12), 3517–3529. http://dx.doi.org/10.1016/j.rse. 2011.08.014.
Wilcoxon F. (1945). Individual Comparisons by Ranking Methods.Biometrics , 1, 80-83.
Work R.A., Stockwell H, Homer J., Freeman T.G. & Beaumont R.T. (1965). Accuracy of field snow surveys Western United States, including Alaska.CRREL Report, 163, 43 pp.
FIGURE CAPTIONS
Figure 1. Schematic representation of the sampling strategy applied during the two field campaigns. The scheme F1 was applied in Blafjöll (Iceland) and the scheme F2 in Sodankylä (Finland). In Sodankylä, the scheme for Bog and Forest plots was applied also in the Antenna plot, but in one subplot measurements were taken in transects (10 measurements per transect). In Bog and Forest opening sites (F2) the four subplots were measured in the same way. Letters N, O and I inform of the uncertainties contained at each measured spatial scale: Natural, induced by Observer and Instrumental bias respectively. The letter size makes reference to H high, M medium and L low relative influence of each uncertainty source at each site.
Figure 2. Instruments used in the campaigns, snow core samplers from left to right (see Table 1): Korhonen-Melander, Dolfi, VS-43, U.S. Federal, IG PAS, SnowHydro, Custom EV2, Enel-Valtecne EV2 and ETH. In addition, the SnowMicroPen is shown on the far right.
Figure 3. Boxplots showing the distribution of measured snow depth (upper panels), bulk snow density (middle panels), and SWE (lower panels) measured with different snow core samplers along two snow trenches in Iceland. Boxes stand for the 25th and 75th percentiles, vertical bars indicate the 10th and 90th percentiles and the horizontal central line is the median. Triangles at the bottom of some boxes inform about distribution skewness. Numbers above each box is the CV for repeated measurements. Dashed and dotted lines are the average and median, respectively, over all measurements on each plot.
Figure 4. Variability of the bulk snow density for the three plots as obtained from SMP measurements using the Proksch et al. (2015) parameterization (see text). The number above each box is the CV for all measurements on that plot. Boxes inform of the 25th and 75th percentiles, vertical bars indicate the 10th and 90th percentiles and the horizontal central line is the median. Dashed and dotted lines are the average and median over all measurements, respectively.
Figure 5. Variability of the 20 measurements (15 in Antenna plot) of snow depth, bulk snow density and SWE taken at the three plots (composed of 4 subplots each) conducted with different devices. The number above each box is the coefficient of variation among repeated measurements. Boxes inform of the 25th and 75th percentiles, bars indicate the 10th and 90th percentile and central line is the median. Triangles at the bottom of some boxes inform about high skewness of distribution. Dots are outliers. Dashed and dotted lines are the average and median respectively.
Figure 6. Bulk snow density difference of each sampler with respect to the total average of all samplers (in percentage) measured at each subplot for each of the three plots.
Figure 7. Bulk snow density measurements for each sampler when used by experienced observers and untrained observers on Bog and Forest plot. Six measurements were conducted with each sampler. Letters indicate the only pairs with statistically significant differences.
Figure 8. Measurements of snow depth (bottom panel) and bulk snow density (upper panel) along 10 m long transects at the Antenna plot.
Table 1. Summary of all the snow core samplers used during the campaigns and their main characteristics.