Abstract
The physical properties of snow, such as its stiffness, reflectivity, and thermal conductivity, are critical components in feedback processes of the Earth’s system and useful proxies for various applications in environmental science, ranging from avalanche forecasting to meteorology. It is therefore important to efficiently and accurately determine snow properties not only in the laboratory, but also during field campaigns. One promising approach is to measure the snow’s optical properties and deduce material properties via theory; from which physical properties can in turn be derived. Most notably, this applies to the determination of the snow’s specific surface area from total diffuse reflectance measurements. The retrieval of another important snow parameter, its mass density, from diffuse reflectance measurements has remained elusive. Here, we outline a theoretical description within the diffusion approximation of the radiative transfer theory to retrieve the density of dry snow from optical measurements via spatial truncation of the diffuse reflectance. Using our model, we determine snow density profiles from partial diffuse reflectance images given prior knowledge of the snow’s specific surface area. Beyond field measurements, our results are mappable to other applications relying on sub-surface light scattering, including remote sensing and biomedical applications.
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Data availability
The experimental data necessary to reproduce Fig. 5 are available at https://doi.org/10.16904/envidat.724.
Code availability
The source code to reproduce Figs. 2–5 is available at https://doi.org/10.16904/envidat.726.
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Acknowledgements
The authors acknowledge the support by Innosuisse under the project number 58741.1 IP-ENG, the Amt für Wirtschaft and Tourismus of the Swiss canton Graubünden, as well as the close technical collaboration with Davos Instruments AG.
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L.M. carried out the research, derived the mathematical expressions, and wrote the article. H.L. participated in all the initial devising of the study and production of the results. M.S. and B.W. devised the experimental concept, supervised the work, and contributed to the discussion of the results.
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The idea leading to this paper has been accepted as a European patent (EP4212848—SNOW DENSITY MEASUREMENT INSTRUMENT, https://register.epo.org/application?number=EP22151594), co-invented by Benjamin Walter, Martin Schneebeli, Henning Löwe, and Lars Mewes. Applicant is the Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft WSL (Zürcherstrasse 111, 8903 Birmensdorf, CH). All authors declare no financial or non-financial interests that could influence the research presented in this article.
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Mewes, L., Löwe, H., Schneebeli, M. et al. Optical determination of snow density via sub-surface scattering. Commun Phys (2026). https://doi.org/10.1038/s42005-026-02490-1
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DOI: https://doi.org/10.1038/s42005-026-02490-1
