Articles | Volume 10, issue 6
https://doi.org/10.5194/tc-10-2847-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/tc-10-2847-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Research article
| 
21 Nov 2016
Research article |
| 21 Nov 2016
Relating optical and microwave grain metrics of snow: the relevance of grain shape
Quirine Krol
WSL Institute for Snow and Avalanche Research SLF, Flüelastrasse 11, 7260 Davos Dorf, Switzerland
WSL Institute for Snow and Avalanche Research SLF, Flüelastrasse 11, 7260 Davos Dorf, Switzerland
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Anna Braun, Kévin Fourteau, and Henning Löwe
EGUsphere, https://doi.org/10.5194/egusphere-2023-1947, https://doi.org/10.5194/egusphere-2023-1947, 2023
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The specific surface of snow dictates key physical properties and continuously evolves in natural snowpacks, referred to as metamorphism. This work develops a rigorous, physical model for this evolution, which is able to reproduce X-ray tomography measurements without using unphysical tuning parameters. Our results emphasize that snow crystal growth on micrometer scales ultimately controls the pace of metamorphism.
Kévin Fourteau, Johannes Freitag, Mika Malinen, and Henning Löwe
EGUsphere, https://doi.org/10.5194/egusphere-2023-1928, https://doi.org/10.5194/egusphere-2023-1928, 2023
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Understanding the settling of snow under its own weight has applications from avalanche forecast to ice core interpretation. We study how this settling can be modeled using 3D images of snow internal structure and ice deformation mechanics. We found that classical ice mechanics, as used for instance in glacier flow, explains the compaction of dense polar snow, but not that of lighter seasonal snow. How exactly the ice deforms during light snow compaction thus remains an open question.
Benjamin Walter, Hagen Weigel, Sonja Wahl, and Henning Löwe
The Cryosphere Discuss., https://doi.org/10.5194/tc-2023-112, https://doi.org/10.5194/tc-2023-112, 2023
Preprint under review for TC
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The topmost layer of a snowpack forms the interface to the atmosphere and is frequently affected by wind. We performed, for the first time, controlled experiments in a wind tunnel under laboratory conditions to systematically quantify the evolution of the surface snow microstructure for different wind speeds, temperatures, and snow transport durations. Our results have implications for cryospheric processes like radiative transfer, avalanche formation or alpine and polar mass balances.
Julien Brondex, Kevin Fourteau, Marie Dumont, Pascal Hagenmuller, Neige Calonne, Francois Tuzet, and Henning Löwe
Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2023-97, https://doi.org/10.5194/gmd-2023-97, 2023
Revised manuscript under review for GMD
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Vapor diffusion is one of the main processes governing snowpack evolution and must be accounted for in models. Recent attempts to represent vapor diffusion in numerical models have been facing several difficulties regarding computational cost, mass and energy conservation. Here, we develop our own finite-element software to explore numerical approaches enabling to overcome these difficulties. We illustrate capabilities of these approaches on established numerical benchmarks.
Kavitha Sundu, Johannes Freitag, Kévin Fourteau, and Henning Löwe
EGUsphere, https://doi.org/10.5194/egusphere-2023-220, https://doi.org/10.5194/egusphere-2023-220, 2023
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Ice crystals often show a rod-like, vertical orientation in snow and firn, they are said to be anisotropic. The stiffness in vertical direction therefore differs from the horizontal which e.g. impacts the propagation of seismic waves. To quantify this anisotropy we conducted finite element simulations of 395 snow, firn, and ice core microstructures obtained from X-ray tomography. From the results we derived a parametrization that may be employed for advanced seismic studies in polar regions.
Amy R. Macfarlane, Henning Löwe, Lucille Gimenes, David N. Wagner, Ruzica Dadic, Rafael Ottersberg, Stefan Hämmerle, and Martin Schneebeli
EGUsphere, https://doi.org/10.5194/egusphere-2023-83, https://doi.org/10.5194/egusphere-2023-83, 2023
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Snow on sea ice is highly insulating and inhibits sea ice growth in winter. We measured the thermal conductivity of snow for one complete winter season for the first time on Arctic sea ice. We found spatial variability to be extremely high and temporal variability to follow a surprising trend: an increase in thermal conductivity until March and a decrease thereafter. We discuss the possible reasons for this trend.
Ghislain Picard, Henning Löwe, and Christian Mätzler
The Cryosphere, 16, 3861–3866, https://doi.org/10.5194/tc-16-3861-2022, https://doi.org/10.5194/tc-16-3861-2022, 2022
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Microwave satellite observations used to monitor the cryosphere require radiative transfer models for their interpretation. These models represent how microwaves are scattered by snow and ice. However no existing theory is suitable for all types of snow and ice found on Earth. We adapted a recently published generic scattering theory to snow and show how it may improve the representation of snows with intermediate densities (~500 kg/m3) and/or with coarse grains at high microwave frequencies.
Konstantin Schürholt, Julia Kowalski, and Henning Löwe
The Cryosphere, 16, 903–923, https://doi.org/10.5194/tc-16-903-2022, https://doi.org/10.5194/tc-16-903-2022, 2022
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This companion paper deals with numerical particularities of partial differential equations underlying 1D snow models. In this first part we neglect mechanical settling and demonstrate that the nonlinear coupling between diffusive transport (heat and vapor), phase changes and ice mass conservation contains a wave instability that may be relevant for weak layer formation. Numerical requirements are discussed in view of the underlying homogenization scheme.
Anna Simson, Henning Löwe, and Julia Kowalski
The Cryosphere, 15, 5423–5445, https://doi.org/10.5194/tc-15-5423-2021, https://doi.org/10.5194/tc-15-5423-2021, 2021
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This companion paper deals with numerical particularities of partial differential equations underlying one-dimensional snow models. In this second part we include mechanical settling and develop a new hybrid (Eulerian–Lagrangian) method for solving the advection-dominated ice mass conservation on a moving mesh alongside Eulerian diffusion (heat and vapor) and phase changes. The scheme facilitates a modular and extendable solver strategy while retaining controls on numerical accuracy.
Sebastian Hellmann, Melchior Grab, Johanna Kerch, Henning Löwe, Andreas Bauder, Ilka Weikusat, and Hansruedi Maurer
The Cryosphere, 15, 3507–3521, https://doi.org/10.5194/tc-15-3507-2021, https://doi.org/10.5194/tc-15-3507-2021, 2021
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In this study, we analyse whether ultrasonic measurements on ice core samples could be employed to derive information about the particular ice crystal orientation in these samples. We discuss if such ultrasonic scans of ice core samples could provide similarly detailed results as the established methods, which usually destroy the ice samples. Our geophysical approach is minimally invasive and could support the existing methods with additional and (semi-)continuous data points along the ice core.
Neige Calonne, Bettina Richter, Henning Löwe, Cecilia Cetti, Judith ter Schure, Alec Van Herwijnen, Charles Fierz, Matthias Jaggi, and Martin Schneebeli
The Cryosphere, 14, 1829–1848, https://doi.org/10.5194/tc-14-1829-2020, https://doi.org/10.5194/tc-14-1829-2020, 2020
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During winter 2015–2016, the standard program to monitor the structure and stability of the snowpack at Weissflujoch, Swiss Alps, was complemented by additional measurements to compare between various traditional and newly developed techniques. Snow micro-penetrometer measurements allowed monitoring of the evolution of the snowpack's internal structure at a daily resolution throughout the winter. We show the potential of such high-resolution data for detailed evaluations of snowpack models.
Silvan Leinss, Henning Löwe, Martin Proksch, and Anna Kontu
The Cryosphere, 14, 51–75, https://doi.org/10.5194/tc-14-51-2020, https://doi.org/10.5194/tc-14-51-2020, 2020
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The anisotropy of the snow microstructure, given by horizontally aligned ice crystals and vertically interlinked crystal chains, is a key quantity to understand mechanical, dielectric, and thermodynamical properties of snow. We present a model which describes the temporal evolution of the anisotropy. The model is driven by snow temperature, temperature gradient, and the strain rate. The model is calibrated by polarimetric radar data (CPD) and validated by computer tomographic 3-D snow images.
Kévin Fourteau, Patricia Martinerie, Xavier Faïn, Christoph F. Schaller, Rebecca J. Tuckwell, Henning Löwe, Laurent Arnaud, Olivier Magand, Elizabeth R. Thomas, Johannes Freitag, Robert Mulvaney, Martin Schneebeli, and Vladimir Ya. Lipenkov
The Cryosphere, 13, 3383–3403, https://doi.org/10.5194/tc-13-3383-2019, https://doi.org/10.5194/tc-13-3383-2019, 2019
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Understanding gas trapping in polar ice is essential to study the relationship between greenhouse gases and past climates. New data of bubble closure, used in a simple gas-trapping model, show inconsistency with the final air content in ice. This suggests gas trapping is not fully understood. We also use a combination of high-resolution measurements to investigate the effect of polar snow stratification on gas trapping and find that all strata have similar pores, but that some close in advance.
Isabelle Gouttevin, Moritz Langer, Henning Löwe, Julia Boike, Martin Proksch, and Martin Schneebeli
The Cryosphere, 12, 3693–3717, https://doi.org/10.5194/tc-12-3693-2018, https://doi.org/10.5194/tc-12-3693-2018, 2018
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Snow insulates the ground from the cold air in the Arctic winter, majorly affecting permafrost. This insulation depends on snow characteristics and is poorly quantified. Here, we characterize it at a carbon-rich permafrost site, using a recent technique that retrieves the 3-D structure of snow and its thermal properties. We adapt a snowpack model enabling the simulation of this insulation over a whole winter. We estimate that local snow variations induce up to a 6 °C spread in soil temperatures.
Ghislain Picard, Melody Sandells, and Henning Löwe
Geosci. Model Dev., 11, 2763–2788, https://doi.org/10.5194/gmd-11-2763-2018, https://doi.org/10.5194/gmd-11-2763-2018, 2018
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The Snow Microwave Radiative Transfer (SMRT) is a novel model developed to calculate how microwaves are scattered and emitted by snow. The model is built from separate, interconnecting modules to make it easy to compare different aspects of the theory. SMRT is the first model to allow a choice of how to represent the microstructure of the snow, which is extremely important, and has been used to unite multiple previous studies. This model will ultimately be used to observe snow from space.
Silvan Leinss, Henning Löwe, Martin Proksch, Juha Lemmetyinen, Andreas Wiesmann, and Irena Hajnsek
The Cryosphere, 10, 1771–1797, https://doi.org/10.5194/tc-10-1771-2016, https://doi.org/10.5194/tc-10-1771-2016, 2016
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Four years of anisotropy measurements of seasonal snow are presented in the paper. The anisotropy was measured every 4 h with a ground-based polarimetric radar. An electromagnetic model has been developed to measured the anisotropy with radar instruments from ground and from space. The anisotropic permittivity was derived with Maxwell–Garnett-type mixing formulas which are shown to be equivalent to series expansions of the permittivity tensor based on spatial correlation function of snow.
H. Löwe and G. Picard
The Cryosphere, 9, 2101–2117, https://doi.org/10.5194/tc-9-2101-2015, https://doi.org/10.5194/tc-9-2101-2015, 2015
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The paper establishes a theoretical link between two widely used microwave models for snow. The scattering formulations from both models are unified by reformulating their microstructure models in a common framework. The results show that the scattering formulations can be considered equivalent, if exactly the same microstructure model is used. The paper also provides a method to measure a hitherto unknown input parameter for the microwave models from tomography images of snow.
M. Proksch, C. Mätzler, A. Wiesmann, J. Lemmetyinen, M. Schwank, H. Löwe, and M. Schneebeli
Geosci. Model Dev., 8, 2611–2626, https://doi.org/10.5194/gmd-8-2611-2015, https://doi.org/10.5194/gmd-8-2611-2015, 2015
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The measurement of snow properties on global scale relies on microwave remote sensing data. The interpretation of the data is however challenging. Here we introduce MEMLS3&a, an extension of the snow emission model MEMLS, to include a backscatter model for active microwave remote sensing. In MEMLS3&a, snow input parameters can be derived by objective measurement methods, which avoids fitting the scattering efficiency of snow. The model is validated with combined active and passive measurements.
S. Schleef, H. Löwe, and M. Schneebeli
The Cryosphere, 8, 1825–1838, https://doi.org/10.5194/tc-8-1825-2014, https://doi.org/10.5194/tc-8-1825-2014, 2014
H. Löwe, F. Riche, and M. Schneebeli
The Cryosphere, 7, 1473–1480, https://doi.org/10.5194/tc-7-1473-2013, https://doi.org/10.5194/tc-7-1473-2013, 2013
Related subject area
Snow Physics
Heterogeneous grain growth and vertical mass transfer within a snow layer under a temperature gradient
Impact of the sampling procedure on the specific surface area of snow measurements with the IceCube
Wind conditions for snow cornice formation in a wind tunnel
Thermal Conductivity of Snow on Arctic Sea Ice
Stochastic analysis of micro-cone penetration tests in snow
A generalized photon-tracking approach to simulate spectral snow albedo and transmittance using X-ray microtomography and geometric optics
Grain-size evolution controls the accumulation dependence of modelled firn thickness
Coherent backscatter enhancement in bistatic Ku- and X-band radar observations of dry snow
Effect of snowfall on changes in relative seismic velocity measured by ambient noise correlation
Orientation selective grain sublimation–deposition in snow under temperature gradient metamorphism observed with diffraction contrast tomography
Recent observations of superimposed ice and snow ice on sea ice in the northwestern Weddell Sea
Experimental and model-based investigation of the links between snow bidirectional reflectance and snow microstructure
Impact of water vapor diffusion and latent heat on the effective thermal conductivity of snow
Enhancement of snow albedo reduction and radiative forcing due to coated black carbon in snow
An exploratory modelling study of perennial firn aquifers in the Antarctic Peninsula for the period 1979–2016
Macroscopic water vapor diffusion is not enhanced in snow
Snow albedo sensitivity to macroscopic surface roughness using a new ray-tracing model
A model for French-press experiments of dry snow compaction
Identification of blowing snow particles in images from a Multi-Angle Snowflake Camera
Modeling snow slab avalanches caused by weak-layer failure – Part 1: Slabs on compliant and collapsible weak layers
Modeling snow slab avalanches caused by weak-layer failure – Part 2: Coupled mixed-mode criterion for skier-triggered anticracks
Modeling the evolution of the structural anisotropy of snow
Motion of dust particles in dry snow under temperature gradient metamorphism
Influence of light-absorbing particles on snow spectral irradiance profiles
Thermal conductivity of firn at Lomonosovfonna, Svalbard, derived from subsurface temperature measurements
Saharan dust events in the European Alps: role in snowmelt and geochemical characterization
On the suitability of the Thorpe–Mason model for calculating sublimation of saltating snow
The influence of layering and barometric pumping on firn air transport in a 2-D model
Surface formation, preservation, and history of low-porosity crusts at the WAIS Divide site, West Antarctica
The significance of vertical moisture diffusion on drifting snow sublimation near snow surface
Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica
A multilayer physically based snowpack model simulating direct and indirect radiative impacts of light-absorbing impurities in snow
Experimental observation of transient δ18O interaction between snow and advective airflow under various temperature gradient conditions
A multiphysical ensemble system of numerical snow modelling
Process-level model evaluation: a snow and heat transfer metric
Near-surface snow particle dynamics from particle tracking velocimetry and turbulence measurements during alpine blowing snow storms
Refinement of the ice absorption spectrum in the visible using radiance profile measurements in Antarctic snow
Anisotropy of seasonal snow measured by polarimetric phase differences in radar time series
Sensitivity of snow density and specific surface area measured by microtomography to different image processing algorithms
Metamorphism during temperature gradient with undersaturated advective airflow in a snow sample
Measurements and modelling of snow particle size and shortwave infrared albedo over a melting Antarctic ice sheet
Microwave scattering coefficient of snow in MEMLS and DMRT-ML revisited: the relevance of sticky hard spheres and tomography-based estimates of stickiness
Microstructure-based modeling of snow mechanics: a discrete element approach
A macroscale mixture theory analysis of deposition and sublimation rates during heat and mass transfer in dry snow
Tomography-based monitoring of isothermal snow metamorphism under advective conditions
Parameterization of single-scattering properties of snow
Study of a temperature gradient metamorphism of snow from 3-D images: time evolution of microstructures, physical properties and their associated anisotropy
Influence of stress, temperature and crystal morphology on isothermal densification and specific surface area decrease of new snow
The growth of sublimation crystals and surface hoar on the Antarctic plateau
Measuring the specific surface area of wet snow using 1310 nm reflectance
Lisa Bouvet, Neige Calonne, Frédéric Flin, and Christian Geindreau
The Cryosphere, 17, 3553–3573, https://doi.org/10.5194/tc-17-3553-2023, https://doi.org/10.5194/tc-17-3553-2023, 2023
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This study presents two new experiments of temperature gradient metamorphism in a snow layer using tomographic time series and focusing on the vertical extent. The results highlight two little known phenomena: the development of morphological vertical heterogeneities from an initial uniform layer, which is attributed to the temperature range and the vapor pressure distribution, and the quantification of the mass loss at the base caused by the vertical vapor fluxes and the dry lower boundary.
Julia Martin and Martin Schneebeli
The Cryosphere, 17, 1723–1734, https://doi.org/10.5194/tc-17-1723-2023, https://doi.org/10.5194/tc-17-1723-2023, 2023
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The grain size of snow determines how light is reflected and other physical properties. The IceCube measures snow grain size at the specific near-infrared wavelength of 1320 nm. In our study, the preparation of snow samples for the IceCube creates a thin layer of small particles. Comparisons of the grain size with computed tomography, particle counting and numerical simulation confirm the aforementioned observation. We conclude that measurements at this wavelength underestimate the grain size.
Hongxiang Yu, Guang Li, Benjamin Walter, Michael Lehning, Jie Zhang, and Ning Huang
The Cryosphere, 17, 639–651, https://doi.org/10.5194/tc-17-639-2023, https://doi.org/10.5194/tc-17-639-2023, 2023
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Snow cornices lead to the potential risk of causing snow avalanche hazards, which are still unknown so far. We carried out a wind tunnel experiment in a cold lab to investigate the environmental conditions for snow cornice accretion recorded by a camera. The length growth rate of the cornices reaches a maximum for wind speeds approximately 40 % higher than the threshold wind speed. Experimental results improve our understanding of the cornice formation process.
Amy R. Macfarlane, Henning Löwe, Lucille Gimenes, David N. Wagner, Ruzica Dadic, Rafael Ottersberg, Stefan Hämmerle, and Martin Schneebeli
EGUsphere, https://doi.org/10.5194/egusphere-2023-83, https://doi.org/10.5194/egusphere-2023-83, 2023
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Snow on sea ice is highly insulating and inhibits sea ice growth in winter. We measured the thermal conductivity of snow for one complete winter season for the first time on Arctic sea ice. We found spatial variability to be extremely high and temporal variability to follow a surprising trend: an increase in thermal conductivity until March and a decrease thereafter. We discuss the possible reasons for this trend.
Pyei Phyo Lin, Isabel Peinke, Pascal Hagenmuller, Matthias Wächter, M. Reza Rahimi Tabar, and Joachim Peinke
The Cryosphere, 16, 4811–4822, https://doi.org/10.5194/tc-16-4811-2022, https://doi.org/10.5194/tc-16-4811-2022, 2022
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Characterization of layers of snowpack with highly resolved micro-cone penetration tests leads to detailed fluctuating signals. We used advanced stochastic analysis to differentiate snow types by interpreting the signals as a mixture of continuous and discontinuous random fluctuations. These two types of fluctuation seem to correspond to different mechanisms of drag force generation during the experiments. The proposed methodology provides new insights into the characterization of snow layers.
Theodore Letcher, Julie Parno, Zoe Courville, Lauren Farnsworth, and Jason Olivier
The Cryosphere, 16, 4343–4361, https://doi.org/10.5194/tc-16-4343-2022, https://doi.org/10.5194/tc-16-4343-2022, 2022
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We present a radiative transfer model that uses ray tracing to determine optical properties from computer-generated 3D renderings of snow resolved at the microscale and to simulate snow spectral reflection and transmission for visible and near-infrared light. We expand ray-tracing techniques applied to sub-1 cm3 snow samples to model an entire snowpack column. The model is able to reproduce known snow surface optical properties, and simulations compare well against field observations.
Jonathan Kingslake, Robert Skarbek, Elizabeth Case, and Christine McCarthy
The Cryosphere, 16, 3413–3430, https://doi.org/10.5194/tc-16-3413-2022, https://doi.org/10.5194/tc-16-3413-2022, 2022
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Firn is snow that has persisted for at least 1 full year on the surface of a glacier or ice sheet. It is an intermediate substance between snow and glacial ice. Firn compacts into glacial ice due to the weight of overlying snow and firn. The rate at which it compacts and the rate at which it is buried control how thick the firn layer is. We explore how this thickness depends on the rate of snow fall and how this dependence is controlled by the size of snow grains at the ice sheet surface.
Marcel Stefko, Silvan Leinss, Othmar Frey, and Irena Hajnsek
The Cryosphere, 16, 2859–2879, https://doi.org/10.5194/tc-16-2859-2022, https://doi.org/10.5194/tc-16-2859-2022, 2022
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The coherent backscatter opposition effect can enhance the intensity of radar backscatter from dry snow by up to a factor of 2. Despite widespread use of radar backscatter data by snow scientists, this effect has received notably little attention. For the first time, we characterize this effect for the Earth's snow cover with bistatic radar experiments from ground and from space. We are also able to retrieve scattering and absorbing lengths of snow at Ku- and X-band frequencies.
Antoine Guillemot, Alec van Herwijnen, Eric Larose, Stephanie Mayer, and Laurent Baillet
The Cryosphere, 15, 5805–5817, https://doi.org/10.5194/tc-15-5805-2021, https://doi.org/10.5194/tc-15-5805-2021, 2021
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Ambient noise correlation is a broadly used method in seismology to monitor tiny changes in subsurface properties. Some environmental forcings may influence this method, including snow. During one winter season, we studied this snow effect on seismic velocity of the medium, recorded by a pair of seismic sensors. We detected and modeled a measurable effect during early snowfalls: the fresh new snow layer modifies rigidity and density of the medium, thus decreasing the recorded seismic velocity.
Rémi Granger, Frédéric Flin, Wolfgang Ludwig, Ismail Hammad, and Christian Geindreau
The Cryosphere, 15, 4381–4398, https://doi.org/10.5194/tc-15-4381-2021, https://doi.org/10.5194/tc-15-4381-2021, 2021
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In this study on temperature gradient metamorphism in snow, we investigate the hypothesis that there exists a favourable crystal orientation relative to the temperature gradient. We measured crystallographic orientations of the grains and their microstructural evolution during metamorphism using in situ time-lapse diffraction contrast tomography. Faceted crystals appear during the evolution, and we observe higher sublimation–deposition rates for grains with their c axis in the horizontal plane.
Stefanie Arndt, Christian Haas, Hanno Meyer, Ilka Peeken, and Thomas Krumpen
The Cryosphere, 15, 4165–4178, https://doi.org/10.5194/tc-15-4165-2021, https://doi.org/10.5194/tc-15-4165-2021, 2021
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We present here snow and ice core data from the northwestern Weddell Sea in late austral summer 2019, which allow insights into possible reasons for the recent low summer sea ice extent in the Weddell Sea. We suggest that the fraction of superimposed ice and snow ice can be used here as a sensitive indicator. However, snow and ice properties were not exceptional, suggesting that the summer surface energy balance and related seasonal transition of snow properties have changed little in the past.
Marie Dumont, Frederic Flin, Aleksey Malinka, Olivier Brissaud, Pascal Hagenmuller, Philippe Lapalus, Bernard Lesaffre, Anne Dufour, Neige Calonne, Sabine Rolland du Roscoat, and Edward Ando
The Cryosphere, 15, 3921–3948, https://doi.org/10.5194/tc-15-3921-2021, https://doi.org/10.5194/tc-15-3921-2021, 2021
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The role of snow microstructure in snow optical properties is only partially understood despite the importance of snow optical properties for the Earth system. We present a dataset combining bidirectional reflectance measurements and 3D images of snow. We show that the snow reflectance is adequately simulated using the distribution of the ice chord lengths in the snow microstructure and that the impact of the morphological type of snow is especially important when ice is highly absorptive.
Kévin Fourteau, Florent Domine, and Pascal Hagenmuller
The Cryosphere, 15, 2739–2755, https://doi.org/10.5194/tc-15-2739-2021, https://doi.org/10.5194/tc-15-2739-2021, 2021
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The thermal conductivity of snow is an important physical property governing the thermal regime of a snowpack and its substrate. We show that it strongly depends on the kinetics of water vapor sublimation and that previous experimental data suggest a rather fast kinetics. In such a case, neglecting water vapor leads to an underestimation of thermal conductivity by up to 50 % for light snow. Moreover, the diffusivity of water vapor in snow is then directly related to the thermal conductivity.
Wei Pu, Tenglong Shi, Jiecan Cui, Yang Chen, Yue Zhou, and Xin Wang
The Cryosphere, 15, 2255–2272, https://doi.org/10.5194/tc-15-2255-2021, https://doi.org/10.5194/tc-15-2255-2021, 2021
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We have explicitly resolved optical properties of coated BC in snow for explaining complex enhancement of snow albedo reduction due to coating effect in real environments. The parameterizations are developed for climate models to improve the understanding of BC in snow on global climate. We demonstrated that the contribution of BC coating effect to snow light absorption has exceeded dust over north China and will significantly contribute to the retreat of Arctic sea ice and Tibetan glaciers.
J. Melchior van Wessem, Christian R. Steger, Nander Wever, and Michiel R. van den Broeke
The Cryosphere, 15, 695–714, https://doi.org/10.5194/tc-15-695-2021, https://doi.org/10.5194/tc-15-695-2021, 2021
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This study presents the first modelled estimates of perennial firn aquifers (PFAs) in Antarctica. PFAs are subsurface meltwater bodies that do not refreeze in winter due to the isolating effects of the snow they are buried underneath. They were first identified in Greenland, but conditions for their existence are also present in the Antarctic Peninsula. These PFAs can have important effects on meltwater retention, ice shelf stability, and, consequently, sea level rise.
Kévin Fourteau, Florent Domine, and Pascal Hagenmuller
The Cryosphere, 15, 389–406, https://doi.org/10.5194/tc-15-389-2021, https://doi.org/10.5194/tc-15-389-2021, 2021
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There has been a long controversy to determine whether the effective diffusion coefficient of water vapor in snow is superior to that in free air. Using theory and numerical modeling, we show that while water vapor diffuses more than inert gases thanks to its interaction with the ice, the effective diffusion coefficient of water vapor in snow remains inferior to that in free air. This suggests that other transport mechanisms are responsible for the large vapor fluxes observed in some snowpacks.
Fanny Larue, Ghislain Picard, Laurent Arnaud, Inès Ollivier, Clément Delcourt, Maxim Lamare, François Tuzet, Jesus Revuelto, and Marie Dumont
The Cryosphere, 14, 1651–1672, https://doi.org/10.5194/tc-14-1651-2020, https://doi.org/10.5194/tc-14-1651-2020, 2020
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The effect of surface roughness on snow albedo is often overlooked,
although a small change in albedo may strongly affect the surface energy
budget. By carving artificial roughness in an initially smooth snowpack,
we highlight albedo reductions of 0.03–0.04 at 700 nm and 0.06–0.10 at 1000 nm. A model using photon transport is developed to compute albedo considering roughness and applied to understand the impact of roughness as a function of snow properties and illumination conditions.
Colin R. Meyer, Kaitlin M. Keegan, Ian Baker, and Robert L. Hawley
The Cryosphere, 14, 1449–1458, https://doi.org/10.5194/tc-14-1449-2020, https://doi.org/10.5194/tc-14-1449-2020, 2020
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We describe snow compaction laboratory data with a new mathematical model. Using a compression device that is similar to a French press with snow instead of coffee grounds, Wang and Baker (2013) compacted numerous snow samples of different densities at a constant velocity to determine the force required for snow compaction. Our mathematical model for compaction includes airflow through snow and predicts the required force, in agreement with the experimental data.
Mathieu Schaer, Christophe Praz, and Alexis Berne
The Cryosphere, 14, 367–384, https://doi.org/10.5194/tc-14-367-2020, https://doi.org/10.5194/tc-14-367-2020, 2020
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Wind and precipitation often occur together, making the distinction between particles coming from the atmosphere and those blown by the wind difficult. This is however a crucial task to accurately close the surface mass balance. We propose an algorithm based on Gaussian mixture models to separate blowing snow and precipitation in images collected by a Multi-Angle Snowflake Camera (MASC). The algorithm is trained and (positively) evaluated using data collected in the Swiss Alps and in Antarctica.
Philipp L. Rosendahl and Philipp Weißgraeber
The Cryosphere, 14, 115–130, https://doi.org/10.5194/tc-14-115-2020, https://doi.org/10.5194/tc-14-115-2020, 2020
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Dry-snow slab avalanche release is preceded by a fracture process within the snowpack. Recognizing weak layer collapse as an integral part of the fracture process is crucial and explains phenomena such as whumpf sounds and remote triggering of avalanches from low-angle terrain. In this first part of the two-part work we propose a novel closed-form analytical model for a snowpack that provides a highly efficient and precise analysis of the mechanical response of a loaded snowpack.
Philipp L. Rosendahl and Philipp Weißgraeber
The Cryosphere, 14, 131–145, https://doi.org/10.5194/tc-14-131-2020, https://doi.org/10.5194/tc-14-131-2020, 2020
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Dry-snow slab avalanche release is preceded by a fracture process within the snowpack. Recognizing weak layer collapse as an integral part of the fracture process is crucial and explains phenomena such as whumpf sounds and remote triggering of avalanches from low-angle terrain. In this second part of the two-part work we propose a novel mixed-mode coupled stress and energy failure criterion for nucleation of weak layer failure due to external loading of the snowpack.
Silvan Leinss, Henning Löwe, Martin Proksch, and Anna Kontu
The Cryosphere, 14, 51–75, https://doi.org/10.5194/tc-14-51-2020, https://doi.org/10.5194/tc-14-51-2020, 2020
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The anisotropy of the snow microstructure, given by horizontally aligned ice crystals and vertically interlinked crystal chains, is a key quantity to understand mechanical, dielectric, and thermodynamical properties of snow. We present a model which describes the temporal evolution of the anisotropy. The model is driven by snow temperature, temperature gradient, and the strain rate. The model is calibrated by polarimetric radar data (CPD) and validated by computer tomographic 3-D snow images.
Pascal Hagenmuller, Frederic Flin, Marie Dumont, François Tuzet, Isabel Peinke, Philippe Lapalus, Anne Dufour, Jacques Roulle, Laurent Pézard, Didier Voisin, Edward Ando, Sabine Rolland du Roscoat, and Pascal Charrier
The Cryosphere, 13, 2345–2359, https://doi.org/10.5194/tc-13-2345-2019, https://doi.org/10.5194/tc-13-2345-2019, 2019
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Light–absorbing particles (LAPs, e.g. dust or black carbon) in snow are a potent climate forcing agent. Their presence darkens the snow surface and leads to higher solar energy absorption. Several studies have quantified this radiative impact by assuming that LAPs were motionless in dry snow, without any clear evidence of this assumption. Using time–lapse X–ray tomography, we show that temperature gradient metamorphism of snow induces downward motion of LAPs, leading to self–cleaning of snow.
Francois Tuzet, Marie Dumont, Laurent Arnaud, Didier Voisin, Maxim Lamare, Fanny Larue, Jesus Revuelto, and Ghislain Picard
The Cryosphere, 13, 2169–2187, https://doi.org/10.5194/tc-13-2169-2019, https://doi.org/10.5194/tc-13-2169-2019, 2019
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Here we present a novel method to estimate the impurity content (e.g. black carbon or mineral dust) in Alpine snow based on measurements of light extinction profiles. This method is proposed as an alternative to chemical measurements, allowing rapid retrievals of vertical concentrations of impurities in the snowpack. In addition, the results provide a better understanding of the impact of impurities on visible light extinction in snow.
Sergey Marchenko, Gong Cheng, Per Lötstedt, Veijo Pohjola, Rickard Pettersson, Ward van Pelt, and Carleen Reijmer
The Cryosphere, 13, 1843–1859, https://doi.org/10.5194/tc-13-1843-2019, https://doi.org/10.5194/tc-13-1843-2019, 2019
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Thermal conductivity (k) of firn at Lomonosovfonna, Svalbard, is estimated using measured temperature evolution and density. The optimized k values (0.2–1.6 W (m K)−1) increase downwards and over time and are most sensitive to systematic errors in measured temperature values and their depths, particularly in the lower part of the profile. Compared to the density-based parameterizations, derived k values are consistently larger, suggesting a faster conductive heat exchange in firn.
Biagio Di Mauro, Roberto Garzonio, Micol Rossini, Gianluca Filippa, Paolo Pogliotti, Marta Galvagno, Umberto Morra di Cella, Mirco Migliavacca, Giovanni Baccolo, Massimiliano Clemenza, Barbara Delmonte, Valter Maggi, Marie Dumont, François Tuzet, Matthieu Lafaysse, Samuel Morin, Edoardo Cremonese, and Roberto Colombo
The Cryosphere, 13, 1147–1165, https://doi.org/10.5194/tc-13-1147-2019, https://doi.org/10.5194/tc-13-1147-2019, 2019
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The snow albedo reduction due to dust from arid regions alters the melting dynamics of the snowpack, resulting in earlier snowmelt. We estimate up to 38 days of anticipated snow disappearance for a season that was characterized by a strong dust deposition event. This process has a series of further impacts. For example, earlier snowmelts may alter the hydrological cycle in the Alps, induce higher sensitivity to late summer drought, and finally impact vegetation and animal phenology.
Varun Sharma, Francesco Comola, and Michael Lehning
The Cryosphere, 12, 3499–3509, https://doi.org/10.5194/tc-12-3499-2018, https://doi.org/10.5194/tc-12-3499-2018, 2018
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The Thorpe-Mason (TM) model describes how an ice grain sublimates during aeolian transport. We revisit this classic model using simple numerical experiments and discover that for many common scenarios, the model is likely to underestimate the amount of ice loss. Extending this result to drifting and blowing snow using high-resolution turbulent flow simulations, the study shows that current estimates for ice loss due to sublimation in regions such as Antarctica need to be significantly updated.
Benjamin Birner, Christo Buizert, Till J. W. Wagner, and Jeffrey P. Severinghaus
The Cryosphere, 12, 2021–2037, https://doi.org/10.5194/tc-12-2021-2018, https://doi.org/10.5194/tc-12-2021-2018, 2018
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Ancient air enclosed in bubbles of the Antarctic ice sheet is a key source of information about the Earth's past climate. However, a range of physical processes in the snow layer atop an ice sheet may change the trapped air's chemical composition before it is occluded in the ice. We developed the first detailed 2-D computer simulation of these processes and found a new method to improve the reconstruction of past climate from air in ice cores bubbles.
John M. Fegyveresi, Richard B. Alley, Atsuhiro Muto, Anaïs J. Orsi, and Matthew K. Spencer
The Cryosphere, 12, 325–341, https://doi.org/10.5194/tc-12-325-2018, https://doi.org/10.5194/tc-12-325-2018, 2018
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Observations at the WAIS Divide site in West Antarctica show that near-surface snow is strongly altered by weather-related processes, such as strong winds and temperature fluctuations, producing features that are recognizable within the WDC06A ice core. Specifically, over 10 000 prominent crusts were observed in the upper 560 m of the core. We show that these crusts develop more often in summers, during relatively low-wind, low-humidity, clear-sky periods with intense daytime sunshine.
Ning Huang and Guanglei Shi
The Cryosphere, 11, 3011–3021, https://doi.org/10.5194/tc-11-3011-2017, https://doi.org/10.5194/tc-11-3011-2017, 2017
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Snow is an important part of the cryosphere, and blowing snow sublimation is an important method to change the snow distribution. However, in the previous studies blowing snow sublimation near surface was ignored. Herein, we built a blowing snow sublimation model to study the sublimation in near-surface region. The results showed that the mass of snow sublimation near surface accounted for even more than half of the total. Therefore, blowing snow sublimation near surface cannot be neglected.
Tim Carlsen, Gerit Birnbaum, André Ehrlich, Johannes Freitag, Georg Heygster, Larysa Istomina, Sepp Kipfstuhl, Anaïs Orsi, Michael Schäfer, and Manfred Wendisch
The Cryosphere, 11, 2727–2741, https://doi.org/10.5194/tc-11-2727-2017, https://doi.org/10.5194/tc-11-2727-2017, 2017
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The optical size of snow grains (ropt) affects the reflectivity of snow surfaces and thus the local surface energy budget in particular in polar regions. The temporal evolution of ropt retrieved from ground-based, airborne, and spaceborne remote sensing could reproduce optical in situ measurements for a 2-month period in central Antarctica (2013/14). The presented validation study provided a unique testbed for retrievals of ropt under Antarctic conditions where in situ data are scarce.
Francois Tuzet, Marie Dumont, Matthieu Lafaysse, Ghislain Picard, Laurent Arnaud, Didier Voisin, Yves Lejeune, Luc Charrois, Pierre Nabat, and Samuel Morin
The Cryosphere, 11, 2633–2653, https://doi.org/10.5194/tc-11-2633-2017, https://doi.org/10.5194/tc-11-2633-2017, 2017
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Light-absorbing impurities deposited on snow, such as soot or dust, strongly modify its evolution. We implemented impurity deposition and evolution in a detailed snowpack model, thereby expanding the reach of such models into addressing the subtle interplays between snow physics and impurities' optical properties. Model results were evaluated based on innovative field observations at an Alpine site. This allows future investigations in the fields of climate, hydrology and avalanche prediction.
Pirmin Philipp Ebner, Hans Christian Steen-Larsen, Barbara Stenni, Martin Schneebeli, and Aldo Steinfeld
The Cryosphere, 11, 1733–1743, https://doi.org/10.5194/tc-11-1733-2017, https://doi.org/10.5194/tc-11-1733-2017, 2017
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Stable water isotopes (δ18O) obtained from snow and ice samples from polar regions are used to reconstruct past climate variability. We present an experimental study on the effect on the snow isotopic composition by airflow through a snowpack in controlled laboratory conditions. The disequilibrium between snow and vapor isotopes changed the isotopic content of the snow. These measurements suggest that metamorphism and its history affect the snow isotopic composition.
Matthieu Lafaysse, Bertrand Cluzet, Marie Dumont, Yves Lejeune, Vincent Vionnet, and Samuel Morin
The Cryosphere, 11, 1173–1198, https://doi.org/10.5194/tc-11-1173-2017, https://doi.org/10.5194/tc-11-1173-2017, 2017
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Physically based multilayer snowpack models suffer from various modelling errors. To represent these errors, we built the new multiphysical ensemble system ESCROC by implementing new representations of different physical processes in a coupled multilayer ground/snowpack model. This system is a promising tool to integrate snow modelling errors in ensemble forecasting and ensemble assimilation systems in support of avalanche hazard forecasting and other snowpack modelling applications.
Andrew G. Slater, David M. Lawrence, and Charles D. Koven
The Cryosphere, 11, 989–996, https://doi.org/10.5194/tc-11-989-2017, https://doi.org/10.5194/tc-11-989-2017, 2017
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This work defines a metric for evaluation of a specific model snow process, namely, heat transfer through snow into soil. Heat transfer through snow regulates the difference in air temperature versus soil temperature. Accurate representation of the snow heat transfer process is critically important for accurate representation of the current and future state of permafrost. Utilizing this metric, we can clearly identify models that can and cannot reasonably represent snow heat transfer.
Nikolas O. Aksamit and John W. Pomeroy
The Cryosphere, 10, 3043–3062, https://doi.org/10.5194/tc-10-3043-2016, https://doi.org/10.5194/tc-10-3043-2016, 2016
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The first implementation of particle tracking velocimetry in outdoor alpine blowing snow has both provided new insight on intermittent snow particle transport initiation and entrainment in the dense near-surface "creep" layer whilst also confirming some wind tunnel observations. Environmental PTV has shown to be a viable avenue for furthering our understanding of the coupling of the atmospheric boundary layer turbulence and blowing snow transport.
Ghislain Picard, Quentin Libois, and Laurent Arnaud
The Cryosphere, 10, 2655–2672, https://doi.org/10.5194/tc-10-2655-2016, https://doi.org/10.5194/tc-10-2655-2016, 2016
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The absorption of visible light in ice is very weak but its precise value is unknown. By measuring the profile of light intensity in snow, Warren and Brand (2006) deduced that light is attenuated by a factor 2 per kilometer in pure ice at a wavelength of 400 nm. We replicated their experiment on a large number of samples and found that ice absorption is at least 10 times stronger. The paper explores various potential physical and statistical biases that could impact the experiment.
Silvan Leinss, Henning Löwe, Martin Proksch, Juha Lemmetyinen, Andreas Wiesmann, and Irena Hajnsek
The Cryosphere, 10, 1771–1797, https://doi.org/10.5194/tc-10-1771-2016, https://doi.org/10.5194/tc-10-1771-2016, 2016
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Four years of anisotropy measurements of seasonal snow are presented in the paper. The anisotropy was measured every 4 h with a ground-based polarimetric radar. An electromagnetic model has been developed to measured the anisotropy with radar instruments from ground and from space. The anisotropic permittivity was derived with Maxwell–Garnett-type mixing formulas which are shown to be equivalent to series expansions of the permittivity tensor based on spatial correlation function of snow.
Pascal Hagenmuller, Margret Matzl, Guillaume Chambon, and Martin Schneebeli
The Cryosphere, 10, 1039–1054, https://doi.org/10.5194/tc-10-1039-2016, https://doi.org/10.5194/tc-10-1039-2016, 2016
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The paper focuses on the characterization of snow microstructure with X-ray microtomography, a technique that is progressively becoming the standard for snow characterization. In particular, it rigorously investigates how the image processing algorithms affect the subsequent microstructure characterization in terms of density and specific surface area. From this analysis, practical recommendations concerning the processing X-ray tomographic images of snow are provided.
Pirmin Philipp Ebner, Martin Schneebeli, and Aldo Steinfeld
The Cryosphere, 10, 791–797, https://doi.org/10.5194/tc-10-791-2016, https://doi.org/10.5194/tc-10-791-2016, 2016
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Changes of the porous ice structure were observed in a snow sample. Sublimation occurred due to the slight undersaturation of the incoming air into the warmer ice matrix. Diffusion of water vapor opposite to the direction of the temperature gradient counteracted the mass transport of advection. Therefore, the total net ice change was negligible, leading to a constant porosity profile. However, the strong recrystallization of water molecules in snow may impact its isotopic or chemical content.
R. Pirazzini, P. Räisänen, T. Vihma, M. Johansson, and E.-M. Tastula
The Cryosphere, 9, 2357–2381, https://doi.org/10.5194/tc-9-2357-2015, https://doi.org/10.5194/tc-9-2357-2015, 2015
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We illustrate a method to measure the size distribution of a snow particle metric from macro photos of snow particles. This snow particle metric corresponds well to the optically equivalent effective radius. Our results evidence the impact of grain shape on albedo, indicate that more than just one particle metric distribution is needed to characterize the snow scattering properties at all optical wavelengths, and suggest an impact of surface roughness on the shortwave infrared albedo.
H. Löwe and G. Picard
The Cryosphere, 9, 2101–2117, https://doi.org/10.5194/tc-9-2101-2015, https://doi.org/10.5194/tc-9-2101-2015, 2015
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The paper establishes a theoretical link between two widely used microwave models for snow. The scattering formulations from both models are unified by reformulating their microstructure models in a common framework. The results show that the scattering formulations can be considered equivalent, if exactly the same microstructure model is used. The paper also provides a method to measure a hitherto unknown input parameter for the microwave models from tomography images of snow.
P. Hagenmuller, G. Chambon, and M. Naaim
The Cryosphere, 9, 1969–1982, https://doi.org/10.5194/tc-9-1969-2015, https://doi.org/10.5194/tc-9-1969-2015, 2015
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This paper deals with a mechanical model that exploits a granular description of the snow microstructure. Its originality is that the geometry of the snow grains and of the inter-granular bonding system are explicitly defined from microtomographic data. It enables to model large deformations controlled by grain-rearrangements, which is of particular interest to study the collapse of weak layers or the characterization of the snowpack with an indenter.
A. C. Hansen and W. E. Foslien
The Cryosphere, 9, 1857–1878, https://doi.org/10.5194/tc-9-1857-2015, https://doi.org/10.5194/tc-9-1857-2015, 2015
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We implement a continuum mixture theory to elucidate coupled heat and mass transfer phenomena occurring in a snow cover. The effects of mass transfer near the ground, near the surface including diurnal temperature effects, as well as adjacent to an ice crust are examined. The analysis requires an accurate assessment of thermal conductivity and the mass diffusion coefficient for snow. An analytical model for these parameters is developed, showing remarkable agreement with numerical models.
P. P. Ebner, M. Schneebeli, and A. Steinfeld
The Cryosphere, 9, 1363–1371, https://doi.org/10.5194/tc-9-1363-2015, https://doi.org/10.5194/tc-9-1363-2015, 2015
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Time-lapse X-ray microtomography was used to investigate the structural dynamics of isothermal snow metamorphism exposed to an advective airflow and possible effects on natural snowpacks were discussed. The results showed that isothermal advection with saturated air have no influence on the coarsening rate that is typical for isothermal snow metamorphism. It is driven by sublimation-deposition caused by Kelvin effect and is the limiting factor independently of the transport regime in the pores.
P. Räisänen, A. Kokhanovsky, G. Guyot, O. Jourdan, and T. Nousiainen
The Cryosphere, 9, 1277–1301, https://doi.org/10.5194/tc-9-1277-2015, https://doi.org/10.5194/tc-9-1277-2015, 2015
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While snow grains are distinctly non-spherical, spheres are often assumed in radiative transfer calculations. Here, angular scattering measurements for blowing snow are used to select an optically equivalent snow grain shape model. Parameterizations are then developed for the asymmetry parameter, single-scattering co-albedo and phase function of snow. The parameterizations will help to improve the treatment of snow in radiative transfer applications, including remote sensing and climate models.
N. Calonne, F. Flin, C. Geindreau, B. Lesaffre, and S. Rolland du Roscoat
The Cryosphere, 8, 2255–2274, https://doi.org/10.5194/tc-8-2255-2014, https://doi.org/10.5194/tc-8-2255-2014, 2014
S. Schleef, H. Löwe, and M. Schneebeli
The Cryosphere, 8, 1825–1838, https://doi.org/10.5194/tc-8-1825-2014, https://doi.org/10.5194/tc-8-1825-2014, 2014
J.-C. Gallet, F. Domine, J. Savarino, M. Dumont, and E. Brun
The Cryosphere, 8, 1205–1215, https://doi.org/10.5194/tc-8-1205-2014, https://doi.org/10.5194/tc-8-1205-2014, 2014
J.-C. Gallet, F. Domine, and M. Dumont
The Cryosphere, 8, 1139–1148, https://doi.org/10.5194/tc-8-1139-2014, https://doi.org/10.5194/tc-8-1139-2014, 2014
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Short summary
Optical and microwave modelling of snow involve different metrics of "grain size" and existing, empirical relations between them are subject to considerable scatter. We introduce two objectively defined metrics of grain shape, derived from micro-computed tomography images, that lead to improved statistical models between the different grain metrics. Our results allow to assess the relevance of grain shape in both fields on common grounds.
Optical and microwave modelling of snow involve different metrics of "grain size" and existing,...
