bluuebunny/crossref_metadata_2025_split huggingface dataset:
Avalanche of 18 January 1997 on Brenva glacier, Mont Blanc Group, Western Italian Alps: an unusual process of formation
Authors: Giani Gian Paolo , Silvano Sandro , Zanon Giorgio 
Published: November 2007

AbstractAt 1455 h on 18 January 1997, an airborne powder avalanche with a volume of about 3 × 106 m3 flowed along the tongue of Brenva glacier, high Aosta valley, on the southern flank of Val Veny, Italy It descended 2000 m and covered a distance of 5.5 km, with a rate of movement on the intermediate stretch of > 70 m s–1. It killed two skiers following a valley-bottom piste, damaged a hotel, destroyed a wide belt of woodland on the opposite slope and caused other minor damage. The avalanche occurred immediately after a large rockfall on the southern slope of the Sperone della Brenva (3567 m a.s.L). However, the relationship between the two events can only be considered indirect, since the main mass of the rockfall stopped at the base of the scar, on a large plateau on the glacier surface. The rockfall and subsequent shock caused the contemporaneous detachment of masses of ice and/or firn from hanging glaciers at the head of a nearby cirque, leading to the formation of the avalanche. The complex mechanism of detachment hypothesized was induced from available documentation and from in situ investigations. Its phases also coincide with seismograms recorded at a station 45 km from the avalanche area. Finally, a mathematical model of the avalanche was used to reconstruct its dynamics and path.
Flow of dense avalanches past obstructions
Authors: Tai Y. C. , Gray J. M. N.T. , Hutter K. , Noelle S. 
Published: November 2007

AbstractOne means of preventing areas from being hit by avalanches is to divert the flow by straight or curved walls or tetrahedral or cylindrical-type structures. Thus, there arises the question how a given avalanche flow is changed regarding the diverted-flow depth and flow direction. In this paper a report is given on laboratory experiments performed for gravity-driven dense granular flows down an inclined plane obstructed by plane wall and tetrahedral wedge. It was observed that these flows are accompanied by shocks induced by the presence of the obstacles. These give rise to a transition from super-to subcritical flow of the granular avalanche, associated with depth and velocity changes. It is demonstrated that with an appropriate shock-capturing integration technique for the Savage-Hutter theory, the shock formation for a finite-mass granular flow sliding from an inclined plane into a horizontal run-out zone is well described, as is the shock formation of the granular flow on either side of a tetrahedral protection structure.
The effect of wind direction on drift control by snow fences
Authors: Takeuchi Yukari , Kobayashi Shun’ichi , Sato Takeshi , Izumi Kaoru , Kosugi Kenji , Xin Wang , Jiapin Zhang , Yongheng Peng 
Published: November 2007

AbstractSnowdrifting processes and the wind-velocity profiles around a collector and a blower snow fence were investigated in a cold wind tunnel. The purpose was to ascertain the effect of wind direction on drift control by snow fences. Three different cases were studied for both types of snow fence, and the resultant snowdrifts were compared. In the first case, the snow fence was perpendicular to the wind direction. In the second and third cases, it was tilted by 30° and 45°. When the collector snow fence was tilted, the amounts of snowdrift were much less than when the fence was perpendicular to the wind direction, because the area with low wind velocity was reduced to half behind the tilted fence. On the other hand, the blowing effect of the blower snow fence increased when it was set up at an angle to the wind direction. It is necessary to investigate the position where the blown snow is deposited by the tilted blower snow fence.
Saltation-layer structure of drifting snow observed in wind tunnel
Authors: Sato Takeshi , Kosugi Kenji , Sato Atsushi 
Published: November 2007

AbstractThe saltation-layer structure of drifting snow was investigated using the wind tunnel in a cold room. Experiments were conducted under various snow-temperature and wind-speed conditions over loose and hard snow covers. Snow was seeded at the upwind end of the wind tunnel. Mass-flux profiles of drifting snow were measured with a snow-particle counter. The theoretical expression for the mass flux of saltating sand (Kawamura, 1948) was fitted to the measured profiles, and two parameters in the theoretical expression, saltation height h0 and mass flux at the surface q0, were determined. The main results are as follows: (1) In the case of hard snow cover, snow particles are hardly ejected and drifting snow is maintained by the seeded snow. The value of h0 linearly increases with wind speed and decreases with snow temperature, and q0 decreases with wind speed and is in proportion to seeding rate. (2) In the case of loose snow cover, erosion occurs under high-wind conditions and the contribution of the ejected snow particles to drifting snow is remarkable. The h0 linearly increases with wind speed, but its value is smaller than the value over hard snow cover. Due to erosion, q0 increases with wind speed. Snowdrift transport rate and q0 do not change with seeding rate under low-wind conditions, because the drifting snow is saturated. Under high-wind conditions, however, both snowdrift transport rate and q0 slightly increase with seeding rate.
Creep experiments and numerical simulations of very light artificial snowpacks
Authors: Abe Osamu 
Published: November 2007

AbstractThis paper reports on the measurement of the viscosity coefficient of very light artificial snow with H. density of < 100 kg m−3. The temperature dependency on the viscosity coefficients of the snow was also obtained, and these results were applied to the problem of snow creep. General comparison between experimental and computed results shows good agreement, but differences between the two creep flows along the slope indicate that low-density snow near the freezing point should be considered as an orthotopic material.
Effect of western U.S. snow cover on climate
Authors: Marshall Susan , Oglesby Robert J. , Nolin Anne W. 
Published: November 2007

AbstractThe purpose of this study is to identify characterize and quantify local, regional and remote effects of snow cover on western U. S. climate and water resources. An ensemble of predictability and sensitivity studies was made with the U.S. National Center for Atmospheric Research (NCAR) Community Climate Model, version 3 (CCM3) to investigate the relative roles of snow-cover anomalies and initial atmospheric states in the subsequent accumulation and ablation seasons. The suite of model experiments focuses on the direct effect of snow on regional climate anomalies and ultimately will be used to examine the lagged effect of anomalous snow cover on the climate. The set of ensemble simulations presented here looks at the climate-system response to anomalously high and low snow cover at the start of the ablation season over the western U.S.A. These current results suggest that the initial state of snow cover is more important than the initial state of the atmosphere or of sea-surface temperatures because of direct thermal effects on the surface and subsequent indirect, dynamical effects on the atmospheric circulation.
Prediction of avalanche paths deviated from the stream by center-of-mass model
Authors: Nagasaki Tomoharu , Izumi Kaoru , Kobayashi Shun’ichi , Yamada Takatsugu 
Published: November 2007

AbstractWe developed a method that predicts avalanche paths deviating from a stream on complex surfaces. This method is based on Nohguchi’s center-of-mass model with simple dynamic resistance. Avalanche paths from many starting points were calculated at two sites in Japan where avalanche disasters have occurred, and paths causing unexpected disaster are presented. The characteristics of avalanche paths at these sites are shown. Small differences of the release positions sometimes cause great changes in avalanche meanderings.
Three-dimensional snow images by X-ray microtomography
Authors: Coléou Cécile , Lesaffre Bernard , Brzoska Jean-Bruno , Ludwig Wolfgang , Boller Elodie 
Published: November 2007

AbstractFor the first time, three-dimensional (3-D) high-resolution images of snow were obtained using X-ray absorption tomography. Images with a spatial resolution of 10 μm were taken on four different cylindrical snow samples (9 mm high, 9 mm diameter). About 1000 two-dimensional X-ray absorption images were recorded at angular positions of the object around an axis spanning 180°. An appropriate algorithm was then used for these data to reconstruct a 3-D image. In the case of snow, experimental problems have been solved to prepare the samples and prevent both melting and metamorphism of snow during the experiments. This tomographic method provided 3-D data files from which images of 6003 voxels were extracted Several physical parameters of snow microstructure can be processed from these data. Porosity P and discrete local (3-D) curvature C of the grain/pore interface were computed for the four snow samples. Representative elementary volume (REV, in the sense of porous media) is a relevant index to the significance of the sample size with respect to a given parameter. From each image, the values of P and C are compared for subsamples of different size, as an attempt to assess the REVs for porosity and curvature. Results show that the observed volume of snow is statistically significant to achieve the porosity and the curvature distribution.
Numerical experiments of wind transport over a mountainous instrumented site: I. Regional scale
Authors: Durand Yves , Guyomarc’h Gilbert , Mérindol Laurent 
Published: November 2007

AbstractFor about ten winter seasons, the Centre d’Etudes de la Neige and CEMAGREF have performed intensive field measurement campaigns concerning various snow and weather parameters during blowing-snow events. The observation sites are located near the ski resort, Alpe d’Huez, Col du Lac Blanc, France (2700–2800 m a.s.L). Our first objective is to include the main effects of the wind in the operational avalanche-hazard forecast at the massif scale, taking into account the effects of local winds on our snow-cover estimation without simulating the phenomena exactly. Only the effects on snow accumulation or erosion and snow characteristics are measured, without any direct link with a precise field location except for the validation. The underlying numerical simulations have been tested on the instrumented site and include an assessment of the appropriate shear velocity, an evaluation of the occurrence of transport related to the snow characteristics provided by the software PROTEON and an estimation of the transport rates. These different computations are embedded in the new software, SYTRON, which is inserted in the SAFRAN/Crocus/MEPRA operational chain! Different validations of this new application are presented in terms of shear velocities, observed transport periods and snow depths. The encouraging results augur well for an operational implementation next winter
Evaluation of the shear frame test for weak snowpack layers
Authors: Jamieson Bruce , Johnston Colin D. 
Published: November 2007

AbstractThe shear frame allows testing of thin weak snowpack layers that are often critical for slab avalanche release. A shear metal frame with an area of 0.01–0.05 m2 is used to grip the snow a few mm above a buried weak snowpack layer. Using a force gauge, the frame is pulled until a fracture occurs in the weak layer within 1 s. The strength is calculated from the maximum force divided by the area of the frame. Finite-element studies show that the shear stress in the weak layer is concentrated below the cross-members that subdivide the frame and where the weak layer is notched at the front and back of the frame. Placing the bottom of the frame in the weak layer increases the stress concentrations, and results in significantly lower strength measurements than placing the bottom of the frame a few mm above the weak layer. Based on over 800 sets of 7–12 tests in western Canada, coefficients of variation average 14% and 18% from level study plots and avalanche start zones, respectively. Consequently,sets of 12 tests typically yield a precision of the mean of 10% with 95% confidence, which is sufficient for monitoring of strength change of weak layers over time in study plots. With consistent technique, there is no significant difference in mean strength measurements obtained by different experienced shear frame operators using the same approximate loading rate and technique for placing the frame. Although fracture surfaces are usually planar, only one of eleven shapes of non-planar fracture surfaces showed significantly different strength compared to planar fracture surfaces. For weak layers thick enough for density measurements, the shear strength is plotted against density and grain form. From these data, empirical equations are determined to estimate the shear strength of weak snowpack layers.
On the correlation between tensile strength and stress wave velocities of dry coherent snow based on its structural model
Authors: Golubev Vladimir N. , Frolov Anatoly D. 
Published: November 2007

AbstractThe various mechanical properties of dry coherent snow are determined by the same structural peculiarities of this medium, that can be described using the model of regular packed grains connected by rigid bonds. Analytic expressions for the many important snow mechanical parameters density elastic moduli, stress wave velocities, strength, etc.) are derived using the model by introducing three non-dimensional principal structural factors: texture friability, bond rigidity and coordination number. Analytic expressions that relate tensile strength to P and S stress wave velocities are proposed and used to examine the interrelations between the internal structure and tensile strength for snow-ice formations in a wide density range. The theoretically derived results and available experimental data are well correlated and form the basis for the development of non-destructive testing methods to evaluate the strength characteristics of snow, using seismic and acoustic measurements.
Measurements and one-dimensional model calculations of snow transport over a mountain ridge
Authors: Doorschot J. , Raderschall N. , Lehning M. 
Published: November 2007

AbstractWind transport of snow can cause an additional snow load on leeward slopes, which often has a considerable influence on avalanche danger. For a quantitative assessment of this process, a model is proposed which calculates the snow transport over a two-dimensional mountain ridge, based on input measurements of wind speed and precipitation. Since the topography is idealized, the model is focused on the snow mass that is transported over the ridge, and no statements are made about the exact snow distribution over the slopes. Three transport modes are distinguished: snow transport in saltation, snow transport in Suspension, and preferential deposition of precipitation. Suspension is modelled with a one-dimensional diffusion equation, and for the saltation layer a newly developed model, based on the microscale physical processes, is implemented. The effect of speed-up of the wind over the ridge is included by assuming an analytical wind profile with a maximum wind speed at a few meters above the ridge Advective effects are taken into account in a parameterization of the turbulent shear stress profile. The model is compared with measurements taken at the experimental snowdrift site Gaudergrat in the Parsenn area, Switzerland, and good agreement is obtained between calculated and measured results.
Photogrammetric avalanche volume measurements at Vallée de la Sionne, Switzerland
Authors: Vallet Juauien , Gruber Urs , Dufour François 
Published: November 2007

AbstractDuring winter 1999 three large avalanche events were triggered by explosives at SLF’s avalanche test site, Vallée de la Sionne, canton Valais, Switzerland. One important goal of these large-scale field experiments was to measure the release and deposition volumes of avalanches by photogrammetric methods. In this paper, the photogrammetric measurements of all three avalanches are summarized. For one avalanche event it was possible to realize the whole measuring procedure as planned, and to obtain volume measurements before and after the avalanche triggering In the other two avalanche events, the photographs before the triggering of the avalanche failed. Nevertheless the photographs taken after the avalanche provide valuable information on the fracture depth at the fracture line. The mean fracture depth of the largest avalanche was about 2.10 m, varying between 1 and 3.5 m over a width of > 1000 m. The total volume of the deposition of all three avalanche events was about 1300 000 m3. The deposits are distributed over a length of > 1000 m with depths up to 30 m. The difference between the released and deposited volumes proved that avalanches entrain a large amount of snow along the avalanche track. Furthermore, the snow distribution in the deposition zone provides important information about the behaviour of a dense flowing avalanche in the runout zone.
Distribution of slushflows in northern Europe and their potential change due to global warming
Authors: Sidorova T. , Belaya N. , Perov V. 
Published: November 2007

AbstractThe distribution of slushflows in northern Europe is described. Schematic maps of the beginning and ending periods of slushflow risk are presented. The months with maximum slufhflow activity are also shown. Potential changes in the geographic and temporal distribution of slushflows due to global warming were analyzed for this region. Calculations for the year 2050 were done on the basis of climatic changes given by three global circulation models. The method of calculation was based on the general relationships between climatic parameters and the geographical and temporal distribution of slushflows. Schematic maps of potential distribution of slushflows show changes when calculated according to the most extreme of the three climatic-change scenarios.
A glacio-chemical characterization of the new EPICA deep-drilling site on Amundsenisen, Dronning Maud Land, Antarctica
Authors: Göktas Fidan , Fischer Hubertus , Oerter Hans , Weller Rolf , Sommer Stefan , Miller Heinz 
Published: November 2007

AbstractIn the framework of the European Project for Ice Coring in Antarctica (EPICA) a glacio-chemical pre-site survey was carried out in Dronning Maud Land (DML), Antarctica, to investigate seasonal and spatial variations. All ion species show pronounced seasonal cycles with the exception of nitrate, which is subject to post-depositional alterations. Sea salt reaches maximum concentrations in late winter/spring, while sulphate, being mainly of marine biogenic origin, shows a double peak with high concentrations both in autumn and in late spring/summer. Methanesulphonate (MSA) also shows a strong autumn peak but only slight indications of a second peak in late spring/summer, as seen for sulphate. Due to post-depositional changes, the seasonal cycle of MSA vanishes further down in the firn. These changes are also reflected in the spatial distribution of MSA. While surface MSA concentrations decline with altitude and higher accumulation rates, concentrations of aged snow show a strong increase with higher accumulation rates in our ice cores. Non-sea-salt sulphate shows a 40% decrease with an increase in snow accumulation of about 80% in recent and aged snow. While the geographical variation is negligible for average nitrate concentrations, sea salt shows an exponential decline with altitude. the outcome of this study confirms that the data of the new EPICA deep drilling site in DML (75˚00.10’ S, 0˚04.07’ E) will be representative for this region, and high-resolution analytical methods will allow accurate stratigraphic dating of a deep ice core.
Lithium in Greenland ice cores measured by ion chromatography
Authors: Siggaard-Andersen Marie-Louise , Steffensen Jørgen Peder , Fischer Hubertus 
Published: November 2007

AbstractIon chromatography (IC) is a widely used technique for analyzing ice cores for ions like Na+, NH4+, K+, Mg2+, Ca2+, F–, MSA–, Cl–, NO2– and SO42– that are present in polar ice cores at ppb level. By using sample preconcentration and an optimized separation technique, we have been able to detect Li+ in ice-core samples in concentrations as low as 0.0001 μeq kg–1 or 0.7 ppt by IC. During routine analysis of ions in ice cores, the lithium content has been evaluated and recorded. the IC technique used in these measurements and some exemplary IC data from the Greenland Icecore Project (GRIP) and the North Greenland Icecore Project (NorthGRIP) ice cores are presented. By these data we introduce Li+ concentration as a new parameter in the analysis of ice cores. Like other ions, Li+ reflects climatic changes and shows seasonal cycles. on the basis of the geochemistry of lithium, we suggest that Li+ measured in the Greenland ice cores is derived from mineral dust. However, data from the NorthGRIP ice core representing the 8.2 kyr BPHolocene cold event show a strong Li+ signal that does not correlate with any other ionic component measured. This means that the lithium content in ice cores is a signal with its own pattern, which is not yet understood.
Mass balance and ice flow along the north-northwest ridge of the Greenland ice sheet at NorthGRIP
Authors: Hvidberg Christine Schøtt , Keller Kristian , Gundestrup Niels S. 
Published: November 2007

AbstractThe North Greenland Icecore Project (NorthGRIP) deep drilling site (75˚05’47’’N, 42˚19’42’’ W) is located at the north-northwest ridge of the Greenland ice sheet, 320 km from Summit. A strain net has been established around the NorthGRIP site and surveyed with global positioning system. Our results show that ice flows with a horizontal surface velocity of 1.329 ±0.015ma–1 along the ridge. Estimated principal surface strain rates at NorthGRIP are and in the directions along and transverse to the north-northwest ridge, respectively, i.e. ice is compressed along the ridge but stretched transverse to the ridge. Possible implications of the observed flow pattern for the stratigraphy are discussed. the average thickening rate in the strain-net area is found to be ∂H/∂t = 0.00 ±0.04ma– 1, in agreement with previous estimates of mass balance in high-elevation areas of Greenland.
Past 43 year oxalate record: Ürümqi glacier No. 1, Tien Shan, China, and its link with Far East Rongbuk Glacier, Qomolangma (Mount Everest)
Authors: Xinqing Lee , Dahe Qin , Jiawen Ren , Keqin Duan , Shichang Kang , Hui Zhou 
Published: November 2007

AbstractA 43 year oxalate record has been recovered in a 14.08m ice core from Ürümqi glacier No. 1 (43˚06’N, 86˚49’ E), a mid-latitude glacier at Ürümqi river head, Tien Shan, western China. Averaging 3.6±9.2 ng g–1 the oxalate has a background level <2 ng g–1 with sporadic concentration enhancements. Most of the spikes reach beyond 10 ng g–1 and have durations 51 year. the oxalate variation correlates with that in Far East Rongbuk Glacier (27˚59’N, 86˚55’ E), Qomolangma (Mount Everest), which is located 1600 kmawayacross the Qinghai–Tibetan Plateau and Taklimakandesert. Although the concentration enhancement in the latter is much higher, and lasts longer, oxalate reaches its highest concentration in both cores at the same time, during winter. the correlation of oxalate records suggests that the two areas may have had the same kind of local sources, but with a much larger (COO)22– flux in the Qomolangma area, or that they may have had a common source in the Indian subcontinent through the longitudinal atmospheric circulation. the concentration variation in the past 40 years coincides with industrial/economic development in southern Asia, and is mainly due to anthropogenic pollution.