bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wind-Tunnel Experiments on Blowing Snow
Authors: Maeno N. , Naruse R. , Nishimura K. , Takei I. , Ebinuma T. , Kobayabhi S. , Nlshlmura H. , Kaneda Y. , Ishida T. 
Published: September 2017

Blowing snow was produced artificially in a cold wind-tunnel, and various measurements were conducted including particle diameters, concentrations, saltation lengths heat transport and electric charge. The mean diameter of blowing snow particles decreased only slightly with increasing height; in the saltation layer, standard deviation was large and velocities were scattered in a wide range, suggesting the complex dynamic process on taking-off. The mean saltation length ranged from a few cm to 40 cm increasing with wind velocity.When wind blew without snow drifting, the static air pressure on the snow surface was smaller at higher levels, the vertical pressure gradient being negative. The pressure gradient became positive when blowing snow was initiated eg +9.6 Pa/m at 11.2 m/s and -8.3 °C. The magnitude of à downward force acting on a saltating snow partice caused by the pressure gradient was not large enough to explain the downward acceleration found from photographic analyses of particle trajectories.Blowing snow particles were charged negatively the magnitude of charge increased with lowering temperature. Increase in vertical heat transfer was found in blowing snow by measuring the temperature of the air at various levels; the increase is reflected on that in the apparent turbulent diffusion coefficient.
Experimental Studies on Densification and Pressure-Sintering of Ice
Authors: Ebinuma Takao , Maeno Norikazu 
Published: September 2017

Pressure-sintering experiments of ice particles were carried out at pressures between 0.1 and 2.0 MPa and temperatures between -25 and -9°C. At each experiment, logarithm of the strain rate of densification was proportional to the density, and the slope of proportionality changed at a critical density implying the alternation of predominant densification mechanisms. The critical density varied with applied pressure and temperature, but its variation was restricted between 700 and 750 kg/m3.At densities below the critical density, two-dimensional coordination numbers of constituent particles increased though specific areas of internal free surface were almost constant. The result was explained by the predominant contribution of the process of particle rearrangement in this density range. On the other hand, the contribution of dislocation creep was concluded to be dominant at densities above the critical density; the creep caused by boundary diffusion also contributes especially at higher densities.
Characteristics of Flowing Snow and Avalanche Impact Pressures
Authors: McClung D. M. , Schaerer P. A. 
Published: September 2017

Experimental data on avalanche impact pressures and speeds from an avalanche path at Rogers Pass, B.C., are presented for both dry and wet avalanches. Data from small load cells (645 mm2 surface) at various heights through the vertical cross-section of the avalanches show that the frequency of particle impact and hence flow density increases rapidly from top to bottom of the flow.Data from a large circular impact plate (196 000 mm2) just above the ground surface show that dry avalanches have relatively higher peak pressures and relatively lower average pressures than wet avalanches for a given speed. Longitudinal wave-like characteristics in the flow may be seen for both wet and dry avalanches, but they appear to be the exception rather than the rule.Comparison of pressure results with those of other studies shows good agreement for peak pressures, but average pressures are generally less than those of previous studies. This discrepancy is attributed to the past use of cells for which loading surface size approached typical particle size. The size effect may be demonstrated by comparison of small cell data with results from the large impact plate at Rogers Pass.
The influence of humidity on the ablation of continental-type glaciers
Authors: Ohno Hiroyuki , Ohata Tetsuo , Higuchi Keiji 
Published: September 2017

The annual evaporation of a continental-type glacier (43°05’ Ν, 86°48’ E) in the Chinese Tien Shan is estimated, based on data derived from four field observations carried out between summer 1987 and spring 1988, and data from a permanent weather station near the glacier. The evaporation during the melting and non-melting seasons is estimated as 81 mm and negligible, respectively. Assuming that the ablation is equivalent to the annual precipitation (650 mm) in 1987, estimated annual evaporation of 81 mm is 12% of the ablation and consumes 54% of the energy which causes the ablation. It can be said that evaporation suppresses ablation by 50% in comparison with the condition in which there is no evaporation.The influence of fluctuations of air temperature and humidity on the ablation of the glacier were evaluated. Changes in temperature and humidity cause larger changes in ablation of glaciers in a cold and dry climate. The influence of humidity change is very important to glaciers located in a relatively warm environment.
Relation between recent glacier variations and climate in the Tien Shan mountains, central Asia
Authors: Chaohai Liu , Tianding Han 
Published: September 2017

Since the Little Ice Age, most glaciers in the Tien Shan mountains have been retreating. Owing to an increase in precipitation in most parts of the mountains during the late 1950s to early 1970s, the percentage of receding glaciers and the speed of retreat have tended to decrease in the 1970s. However, the general trend of continuous glacier retreat remains unchanged, in part because the summer air temperature shows no tendency to decrease.In the Tien Shan mountains, as the degree of climatic continentality increases the mass balance becomes more dependent on summer temperature, and accumulation and ablation tend to be lower. Therefore, the responses of glaciers to climatic fluctuations in more continental areas are not synchronous with those in less continental areas, and the amplitude of the glacier variations becomes smaller.
Friction of melting ice
Authors: Jones Stephen J. , Kitagawa H. , Izumiyama K. , Shimoda H. 
Published: September 2017

The friction of pure ice against various materials was studied at the melting point by pulling plates of the materials of known roughness under a melting ice sample, which was loaded from above, and by maintaining a surrounding air temperature of +2°C (±1°C). Speed was varied over a wide range from 0.05 to 400 mm s−1.Results for an aluminium sheet of roughness Ra = 0.84 μm, showed a maximum in friction coefficient of 0.04 at a speed of 16 mm s−1. Below this speed the friction coefficient dropped to 0.002 at 0.2 mm s −1 and results from different ice samples were very reproducible. Above 16 mm s−1, the friction coefficient initially dropped to about 0.002 at 100 mm s−1, and then increased again to 0.037 at 400 mm s−1. Results at speeds above 16 mm s−1 were much less reproducible than those at lower speeds. Results are given also for the friction of ice on Formica, acrylic, and copper plates.The amount of meltwater produced during a test was measured by weighing an absorbent tissue before and after mopping-up the meltwater. The amount of meltwater was significantly more for aluminium than for Formica or acrylic, showing that the thermal conductivity of the slider was controlling the amount of meltwater. The amount was also a strong function of velocity.
A laboratory study of sediment deformation: stress heterogeneity and grain-size evolution
Authors: Iverson Neal R. , Hooyer Thomas S. , Hooke Roger Leb. 
Published: September 2017

In shearing sediment beneath glaciers, networks of grains may transiently support shear and normal stresses that are larger than spatial averages. Consistent with studies of fault-gouge genesis, we hypothesize that crushing of grains in such networks is responsible for surrounding larger grains with smaller grains. At sufficiently large strains, this should minimize stress heterogeneity, favor intergranular sliding and abrasion rather than crushing, and result in a self-similar grain-size distribution.This hypothesis is tested with a ring-shear device that slowly shears a large annular sediment sample to high strains. Shearing and comminution of weak equigranular (2.0–3.3 mm) sediment resulted in a self-similar grain-size distribution with a fractal dimension that increased with shear strain toward a steady value of 2.85. This value is significantly larger than that of gouges produced purely by crushing, 2.6, but it is comparable to values for tilts thought to be deforming beneath modern glaciers, 2.8 to nearly 3.0. At low strains, under a steady mean normal stress of 84 kPa, variations in normal stress measured locally ranged in amplitude from 50 to 300 kPa with wavelengths that were 100 times larger than the initial grain diameter. Crushing of grains, observed through the transparent walls of the device, apparently caused the failure of grain networks. At shearing displacements ranging from 0.7 to 1.0 m, the amplitude of local stress fluctuations decreased abruptly. This change is attributed to fine sediment that distributed stresses more uniformly and caused grain networks to fail primarily by intergranular sliding rather than by crushing of grains. Sliding between grains apparently produced silt by abrasion and resulted in a fractal dimension that was higher than if there had been only crushing.A size distribution with a fractal dimension greater than 2.6 is probably a necessary but not sufficient condition for determining whether a basal till has been highly deformed. Stress heterogeneity in subglacial sediment that is shearing through its full thickness should contribute to the erosion of underlying rock.
Sliding of till over bedrock: scratching, polishing, comminution and kinematic-wave theory
Authors: Hindmarsh R.C.A. 
Published: September 2017

The observed ratio of removal of material by (i) scratches gouged by large clasts and (ii) polishing by debris suggests that the latter is the dominant form of bedrock erosion. We examine this with a multi-stage breakdown model of glacial debris, which includes active erosion by fines. These models suggest that a mother clast can, through the action of its daughter debris, erode several times its own volume of bedrock.Till-sliding over bedrock is likely to be a potent source of scouring. By proposing a till/bedrock sliding law, we investigate the kinematics of sliding till bodies. Ice flow naturally tends to thin and extend till cover, even in the absence of longitudinal gradients in the applied stress. Thicker till cover has an increased effective pressure at its base, a lower sliding velocity and, for larger thicknesses, a decrease in sediment flux with thickness. This implies backward-moving kinematic waves and shocks. It is suggested that this is related to the blunt upstream faces of drumlins, and that drumlinization can be a consequence of debris sliding over bedrock.
Abraded rock landforms (whalebacks) developed under ice streams in mountain areas
Authors: Evans Ian S. 
Published: September 2017

Like many mountain ranges, the Coast Mountains of British Columbia, Canada, have undergone both local and ice-sheet glaciation. Effects of ice sheets are concentrated along major valleys and on adjacent spurs and passes which carried strong flows of diffluent ice. The major valleys are broad glacial troughs with frequent rock basins. Their slopes are broken into rounded, steep-sided bosses whalebacks abraded on all sides: they are of the order of 100 m to 1 km long, and 10 m high. In the southern Coast Mountains, the distribution of these whalebacks is consistent with a proposed pattern of former ice streams 1.0–2.1 km thick, within the Cordilleran ice sheet. They are best developed where geological structures parallel the valley and thus the former ice-flow direction, but they are found on a range of lithologies and some are transverse to structure. The whalebacks provide an impression of glacial streamlining, and occasionally grade into rock drumlins. Roches moutonnées are rare in the major troughs.It is hypothesised that these whalebacks and rock drumlins develop under ice streams of Greenland or East Antarctic type, sliding rapidly over bedrock and exploiting rock weaknesses to produce streamlined features. Lee slopes are abraded when thick ice suppresses bed separation, even with rapid flow; basal ice of low viscosity would aid this suppression. Water pressures under the ice streams may have remained high, so that lee-side plucking was rare; such plucking is most likely where pressure fluctuates dramatically, and especially when lee cavities under active ice reach atmospheric pressure.
Mechanical and structural properties of weak snow layers measured in situ
Authors: Föhn Paul M. B. , Camponovo Christian , Krüsi Georges 
Published: September 2017

Weak layers such as buried surface hoar or depth hoar frequently form the failure plane of slab avalanches. Therefore, the mechanical properties of such layers in relation to their snow structure have been investigated. Since it is difficult to transport samples containing a weak layer into cold rooms, the mechanical measurements have to be made in situ.We investigate strain-rate dependency of shear strength by measuring concurrently strength, deformation and acceleration, using a digital force gauge attached to a 0.05 m2 shear frame to which an accelerometer and a displacement sensor are fixed. In doing so, a dynamic force comparable to a driving skier is applied. The measurements cover a strain-rate range 10-2 to 1 s-1. The samples fail in a brittle manner. The shear-strength values cover the range 0.2–2.8 kPa. The dataset is also used to approximate the coefficient G, the shear modulus, for different weak layers.The snow structure has been analysed macroscopically in the field and for some layers representative snow samples have been extracted in order to prepare, in the cold laboratory, single-sided serial planes with cuts every 0.1 mm recorded by video. The analysis of these snow samples should have given the relation between some mechanical properties (strength, strain) and the structural properties. Due to basic problems in defining the connection between complex snow grains (e.g. surface hoar), we were unable to complete this part in due time. Only preliminary results on this aspect are presented here. Based on our long-term database, containing macroscopic structural and strength data of weak layers, a relationship between snow type and shear strength has been established.
Measurements and numerical simulations of snow-particle saltation
Authors: Nishimura K. , Sugiura K. , Nemoto M. , Maeno N. 
Published: September 2017

First, wind-tunnel experiments were carried out to measure the trajectories of saltating snow particles with varying friction velocity. Trajectories of saltating particles were recorded by a video system with a laser sheet and trajectory statistics, such as ejection and impact velocities and angles, were obtained for each particle. Parabolic trajectories are considerably elongated with an increase in the friction velocity; impact angle was approximately the same but ejection angle decreased with increasing friction velocity. Furthermore, it should be noted that the gradient of flux decay with height decreased with friction velocity. In the experiments, a snow-particle counter, which can sense not only the number of particles but also their diameters, was introduced. The flux distribution and the transport rate obtained as a function of the particle size gave a new insight into the relationship with the friction velocity.Trajectories of saltating grains were computed, using the measurements of the initial ejection velocities, angles and the mean velocity profile of the air. The results agreed reasonably with our measurements. Using the measured probability distribution of the ejection velocities, an ensemble of trajectories was computed and thence the vertical profiles of stream-wise fluxes. The exponential decay of the flux on height was obtained in all cases and it supports the basic validity of the model, although agreement is less than expected.
The development of a rule-based spatial model of wind transport and deposition of snow
Authors: Purves R. S. , Barton J. S. , Mackaness W. A. , Sugden D. E. 
Published: September 2017

This paper describes the early stages in the development and testing of a spatio-temporal rule-based model of snow transport by wind over complex terrain. The model uses a cell-based approach and takes into account a range of meteorological, snow-pack and topographic variables. Simple rules are used to determine movement of material from cell-to-cell within the model.A geographic information system is utilized in modelling wind vectors and the influence of topography upon those vectors, and creating the resulting pattern of snow accumulation at a resolution of 50 m. These patterns of accumulation have been compared with empirical work in the field and, although field data were limited, a good qualitative correlation has been found; for example, modelled accumulations correlate with known areas of accumulation such as gullies and hollows.
Snowdrift modelling in a wind tunnel: vertical and horizontal variation of the snow flux
Authors: Naaim-Bouvet Florence , Naaim Mohamed 
Published: September 2017

This paper deals with the influence of the vertical and horizontal variation of Aeolian snow flux on estimations of snow-storm duration and on snowdrift patterns simulated in a wind tunnel.First of all, we shall review recent developments, including our own simulations, concerning the horizontal increase of mass flux until drifting-snow saturation has been reached.Next, after a critical examination of various snowdrift-modelling criteria, we present the results of an experiment undertaken in our wind tunnel: We studied cross-section drill-area changes behind a small-scale snow fence as a function of time for different fetches but for the same mean wind speed at the beginning of the testing section. For each fetch, we carried out vertical profiles of sand particles using image processing and we studied the geometrical parameters of the drift. We conclude dial changes in the cross-section drift area depend on the ablation length and if particle saturation is not reached, the use of a storm-duration scale leads to Overevaluation of prototype storm duration. Moreover, we point out that drift pattern vary as a function of the concentration profiles.
Experimental mass-flux measurements: a comparison of different gauges with estimated theoretical data
Authors: Font D. , Mases M. , Vilaplana J.M. 
Published: September 2017

In experimental snowdrifting mass-flux measurements many different instruments have been tested (Takeuchi, CEMAGREE Mases, etc.). Very often the results obtained are a function of the gauge used. However, in order to compare data from different instruments, orders of magnitude have to be similar.Since 1992, snowdrifting has been studied at an experimental plot at La Molina ski resort (eastern Spanish Pyrenees). The alpine site, characterized by a plateau topography, is located at 2250 m.In this paper, different gauges used to measure snowdrifting mass flux at this site are presented: one snow-collector column and two types of snow traps. Snow-collector columns (prismatic boxes) are permanent installations and are used to measure the mass-flux episode. Snow traps (Takeuchi, 1980: modified) are lighter and more mobile, and they are used for short experiments during a wind episode during which mass-flux data are obtained.The three different gauges are compared and the rate of trapping efficiency is suggested from a comparison of the field data with estimated mass-flux data deduced from empirical formulae (Mellor and Fellers, 1986; Naaim-Bouvet and others, 1996). The mass-flux values obtained at the experimental site are lower than the estimated values.
Empirical model for snowdrift distribution in avalanche-starting zones
Authors: Mases M. , Buisson L. , Frey W. , Martí G. 
Published: September 2017

Field data from Stillberg (Switzerland), provided by SFISAR, have been analysed in order to understand the spatial distribution of snow transported by wind in avalanche-starting zones. The results have been used to develop a new empirical model for snowdrift distribution. This model constitutes the “snow-wind module” of the knowledge-based computer system called ELSA.The model is based on an empirical parameter called the wind or “aeolien” coefficient. It represents the relation between two snow heights at a given place: the snow accumulated at the end of a wind period (or wind episode) and the snow available for transport at the beginning of the wind period. The wind coefficient has been established using field data from the Stillberg site.
Density, velocity and friction measurements in a dry-snow avalanche
Authors: Dent J.D. , Burrell K.J. , Schmidt D. S. , Louge M.Y. , Adams E.E. , Jazbutis T.G. 
Published: September 2017

A small avalanche path near the Bridger Bowl ski area in southwestern Montana has been instrumented to measure density, velocity and dynamic friction in a flowing avalanche. These measurements, made by an array of sensors mounted in the avalanche path, have been carried out for several dry-snow avalanches. Measurements of density were made using a capacitance probe that measures the dielectric constant of any material that passes in front of it. Through a calibration procedure, the dielectric constant of a given type of snow can be related to the density of that snow. Optical sensors were used to measure light reflected from the avalanche as it passed by the sensors. Signals from adjacent optical sensors were cross-correlated to determine velocity. Density and velocity measurements were made at several heights in the avalanche, with particular attention directed near the running surface. Results indicate that avalanche deformation is concentrated near the running surface where the snow density is found to be largest. Upward from the surface, the velocity gradient falls off greatly while the density also declines.Finally, the dynamic-friction coefficient at the base of the avalanche was found by measuring shear and normal forces on a roughened 23 cm × 28 cm aluminum plate mounted parallel and flush with the avalanche running surface. The ratio of the shear force to normal force on the plate provides a measure of the dynamic-friction coefficient at the base of the avalanche.
Measurement of snow-hardness distribution
Authors: Takeuchi Yukari , Nohguchi Yasuaki , Kawashima Katsuhisa , Izumi Kaoru 
Published: September 2017

Disitributions of snow hardness minutely measured with a bandy-type digital load-gauge (push–pull gauge) are demonstrated. This push-pull gauge is of compact design and is useful for precise measurement of tension and compression loads. It can measure the maximum strength of a snowpack when it is destroyed by the attachment pushed horizontally into the side of the pit. Because it takes only a few seconds for one measurement, snow-hardness distribution can be measured at very small space intervals more quickly and with less effort than by using any previous hardness meter, such as a rammsonde, Canadian gauge, Kinosita-type hardness meter, and so on.Snow-pit observations were made at Saiho, Sapporo and Minakami, Japan, in the winter seasons of 1996 and 1997. The snow hardness was measured with the push-pull gauge at regular intervals of 5 cm vertically and 10 cm horizontally. Some weak layers between harder layers could be detected with the push-pull gauge whereas they could not be using the rammsonde. The hardness of snow was observed to be almost uniform horizontally before snowmelt. Once meltwater infiltrated into the snowpack, its distribution became heterogeneous. It was revealed that the hardness of the fine-grained compacted snow layer with grain-sizes less than 0.5 mm showed a high correlation with the fourth power of the snow density.