bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interplay of entrainment and rheology in snow avalanches: a numerical study
Authors: Issler Dieter , Pastor Pérez Manuel 
Published: September 2011

AbstractA one-dimensional evolution equation for the slope-normal velocity profile of a streamwise uniform avalanche over an entrainable bed is derived. The boundary conditions are no slip at the bed, a stress-free surface and constant bed shear stress equal to the shear strength of the snow cover. The resulting equation is solved numerically by means of finite differences on a regular grid with a superposed fine grid near the erosion front that is adjusted at each time-step. The first exploratory simulations yield realistic entrainment rates and show that the entrainment rate tends towards a constant value while the flow depth and the velocity increase linearly with time for all investigated rheologies. It is shown that there indeed exists a rheology-independent asymptotic solution to the equation of motion of an entraining slab if the bottom friction is equal to the bed shear strength; the asymptotic acceleration is found to be half the downslope gravitational acceleration. The model can easily be extended to general path profiles, non-uniform flows and variable snow properties.
Variability of atmospheric freezing-level height and its impact on the cryosphere in China
Authors: Zhang Yinsheng , Guo Y. 
Published: September 2011

AbstarctWe used atmospheric air-temperature data from the Chinese radiosonde network to analyze changes in freezing-level heights (FLHs) during the past 48 years and studied their impacts on the cryosphere. We examined radiosonde time-series data from 92 selected Chinese radiosonde network stations. Generally, FLH exhibited a latitudinal zone, declining from the south. The FLH trend during 1958–2005 showed spatial inhomogeneity, most uniform distributions during autumn, and significant upward trends. Temporal variability of FLH in eastern China was briefly associated with El Niño Southern Oscillation events, but the causes of FLH changes in western China require further investigation. FLH in western and northern China has mostly increased since 1958, and might be considered a possible indicator of cryospheric change during the second half of the 20th century. There were significant correlations between FLH and changes in snow cover, glaciers and permafrost.
Sensitivity of snow avalanche simulations to digital elevation model quality and resolution
Authors: Bühler Yves , Christen Marc , Kowalski Julia , Bartelt Perry 
Published: September 2011

AbstractDigital elevation models (DEMs), represent the three-dimensional terrain and are the basic input for numerical snow avalanche dynamics simulations. DEMs can be acquired using topographic maps or remote-sensing technologies, such as photogrammetry or lidar. Depending on the acquisition technique, different spatial resolutions and qualities are achieved. However, there is a lack of studies that investigate the sensitivity of snow avalanche simulation algorithms to the quality and resolution of DEMs. Here, we perform calculations using the numerical avalance dynamics model RAMMS, varying the quality and spatial resolution of the underlying DEMs, while holding the simulation parameters constant. We study both channelized and open-terrain avalanche tracks with variable roughness. To quantify the variance of these simulations, we use well-documented large-scale avalanche events from Davos, Switzerland (winter 2007/08), and from our large-scale avalanche test site, Vallée de la Sionne (winter 2005/06).We find that the DEM resolution and quality is critical for modeled flow paths, run-out distances, deposits, velocities and impact pressures. Although a spatial resolution of ∼25m is sufficient for large-scale avalanche modeling, the DEM datasets must be checked carefully for anomalies and artifacts before using them for dynamics calculations.
Snow avalanche flow-regime transitions induced by mass and random kinetic energy fluxes
Authors: Bartelt Perry , Meier Lorenz , Buser Othmar 
Published: September 2011

AbstractWe perform a linear-stability analysis of a system of ordinary differential equations describing the motion of dense flowing avalanches. The depth-averaged equations relate the mean translational velocity of the avalanche to the production of turbulent kinetic energy associated with the random motion of the snow granules. Flow friction is described by an extended Voellmy model, where both the Coulomb and turbulent resistance are related to the random kinetic energy. We identify two snow avalanche flow regimes: (1) an unstable frictional flow regime characterized by low random kinetic energy production and (2) a stable, collisional flow regime at the avalanche front. Flow-regime transitions are governed by the production of random kinetic energy, which is controlled by mass. The unstable regime is characterized by a saddle point which the avalanche encounters at the onset of motion and deposition. Depending on the release mass and/or mass growth, the avalanche head will either fluidize, leading to far-reaching avalanches, or starve and die out. At the tail of the avalanche this saddle point also controls the commencement of deposition and therefore the stopping behaviour of avalanches. We discuss the conditions for flow-regime transitions and the enhanced mobility of snow avalanches.
Measuring snow in 3-D using X-ray tomography: assessment of visualization techniques
Authors: Heggli M. , Köchle B. , Matzl M. , Pinzer B.R. , Riche F. , Steiner S. , Steinfeld D. , Schneebeli M. 
Published: September 2011

AbstarctSnow hides its true structure from easy visual observation. One reason is that ice is transparent, so the three-dimensional (3-D) structure is impossible to disentangle. 3-D reconstruction is essential to understand the physical and mechanical properties of snow. In recent years, the techniques to measure and visualize snow in 3-D have improved tremendously. X-ray microtomography is much more user-friendly than the older microtome sectioning techniques. We show different techniques to measure cast and natural snow samples and the steps necessary to produce high-quality data. The simplest way is 3-D renderings. Imaging snow in 3-D definitively challenges our previous view of a snowpack consisting of particles as traditionally seen on a crystal card.
Freezing experiments on unsaturated sand, loam and silt loam
Authors: Watanabe Kunio , Kito Tetsuya , Wake Tomomi , Sakai Masaru 
Published: September 2011

AbstarctEstimating soil-water flow during ground freezing is important for understanding factors affecting spring farming, soil microbial activity below the frozen soil, and permafrost thawing behavior. In this study, we performed a column freezing experiment using three different unsaturated soils (sand, loam and silt loam) to obtain a detailed dataset of temperature, water-content and pressure-head change under freezing conditions. The liquid water content and pressure head in the three soils decreased with decreasing temperature. Three soil temperature stages were found: unfrozen, stagnating near 0˚C and frozen. The temperature and duration of the stagnation stage differed among the soil types. The changes in liquid water content and pressure head during the freezing process were highly dependent on the soil-water retention curve. Water flowed through the frozen area in silt loam and sand, but no water flux was observed in the frozen loam. The freezing soil columns tended to contain more liquid water than estimated from retention curves measured at room temperature, especially at the early stage of freezing.
Local terrain-topography and thermal-properties influence on energy and mass balance of a snow cover
Authors: Adams E.E. , Slaughter A.E. , McKittrick L. , Miller D.A. 
Published: September 2011

AbstarctSnow’s interaction with the environment is an important area in environmental science, particularly as climatic conditions change. We consider the local influence at the slope or smaller scale. Near-surface properties drive the dynamic interface with the atmosphere and with surrounding terrain. While accounting for topography, complex interactions involving energy and mass transfer at the snow surface are considered, using a computer simulation (RadTherm/RT). Digital elevation maps are used to numerically fabricate terrain features and vegetation, while applying appropriate thermal properties to specified terrain types. Conduction, convection radiation and phase change (for dry snow) are considered. Particularly relevant to this study are longwave infrared and shortwave radiation, which in the model account for shadowing, multiple reflective and emissive contributions. An example of a north-facing 30˚, snow-covered clearing bounded by trees is examined using measured meteorological conditions. Applying the same weather conditions, the model is used to examine the difference if the trees are assumed bare or covered with snow. Results indicate that, for the conditions considered, when trees are covered with snow, the open slope is cooler and the snow mass loss is less. Spatial variability across the slope is also noted. Differences are largely due to topographic radiation exchange.
Recent fluctuations of meteorological and snow conditions in Japanese mountains
Authors: Yamaguchi Satoru , Abe Osamu , Nakai Sento , Sato Atsushi 
Published: September 2011

AbstarctMeteorological data from mountainous areas of Japan have been collected by the National Research Institute for Earth Science and Disaster Prevention (NIED) for almost 20 years. The collected long-period data indicate that neither a notable increase in mean winter temperature nor a reduction in snow depth has occurred in these areas. The maximum snow depth, SDmax, and maximum snow water equivalent, SWEmax, show similar fluctuation trends, although with large year-to-year variations in value and a larger fluctuation range for SWEmax than for SDmax. This result suggests that monitoring of only SDmax in mountainous areas is not sufficient for understanding the quantitative fluctuation of water resources originating from snow. The SDmax fluctuation trends in mountainous areas sometimes differ from those in flatland areas because mountain SDmax depends more on winter precipitation than on mean winter air temperature, whereas the opposite is true for flatlands. In addition, the dependence ratio of SDmax on fluctuations in winter precipitation changes with altitude because the distributions of precipitation with air temperature change with altitude.
Glacial lake inventory of Bhutan using ALOS data: methods and preliminary results
Authors: Ukita Jinro , Narama Chiyuki , Tadono Takeo , Yamanokuchi Tsutomu , Tomiyama Nobuhiro , Kawamoto Sachi , Abe Chika , Uda Tsuyoshi , Yabuki Hironori , Fujita Koji , Nishimura Kouichi 
Published: September 2011

AbstarctThe Advanced Land Observing Satellite (ALOS) is relatively new. Its optical sensors are capable of making high-resolution digital surface models (DSMs). For the first time, the task of constructing a regional-scale inventory of glacial lakes based on ALOS data has been undertaken. This study presents the data-processing methods and the results of validation and analysis on the ALOS-based glacial lake inventory of Bhutan in the Himalaya. The analysis based on GPS measurements taken at Metatshota lake in the Mangde Chu sub-basin, one of the glacial lakes assessed as presenting a potential flood danger, shows a validation estimate of 9.5 m for the location of the ALOS-based polygon, with a root mean square of 11.7 m. A comparison with digitized data from the International Centre for Integrated Mountain Development (ICIMOD) shows that positioning and evaluation of terrain changes can be significantly improved using ALOS data. Preliminary analysis of the glacial lakes in four sub-basins, Mo Chu, Pho Chu, Mangde Chu and Dangme Chu, reveals that the frequency distribution of lake sizes biases towards smaller lakes. Glacial lakes 0.01–0.05km2 in area account for ~55% of the total number and occupy 13% of the total area. Together our results demonstrate the usefulness of high-resolution ALOS data with accurate DSMs for studying glacial lakes. High priority must be given to continuously improving and updating the glacial lake inventory with high-resolution satellite data.
Parameterization of the shear strength of faceted crystals during equi-temperature metamorphism
Authors: Hirashima Hiroyuki , Abe Osamu , Sato Atsushi 
Published: September 2011

AbstarctChanges in the shear strength of faceted crystals were measured and parameterized under equi-temperature conditions in the laboratory. The air temperature and bottom temperature of the snow layer were controlled to create a large temperature gradient for 8.8 days to make faceted crystals. Subsequently, the temperature gradient was eliminated and the snow was kept under equi-temperature conditions (–5°C and –10°C) for 55 days. During the experiments, the snow density and shear strength were measured six times. The measured shear strength was compared with two empirical relationships based on density. One of these relationships addresses the strength of round grains, whereas the other refers to faceted grains. The measured shear strength approached the calculated value for faceted crystals when the temperature gradient was large, whereas it approached that for rounded grains after the temperature gradient was removed. The dry snow metamorphism factor (DSM factor), which expresses the developmental stage of faceted crystals, was used to model the shear strength increase under equi-temperature conditions. The DSM factor indicates shear strength using an empirical equation based on rounded grains or faceted crystals. It is approximately 0 for rounded grains and 1 for faceted crystals. It decreased from 1.04 to 0.84 and 0.79 at –10°C and –5°C, respectively, in 55 days. These results were incorporated into the numerical snowpack model SNOWPACK, which successfully reproduced the experimentally observed increase in shear strength under equi-temperature conditions.
Interannual changes in sea-ice conditions on the Arctic Sea Route obtained by satellite microwave data
Authors: Shibata Hiroki , Tateyama Kazutaka , Enomoto Hiroyuki , Takahashi Shuuhei 
Published: September 2011

AbstarctWith decreases in Arctic sea-ice extent in recent years, the Northern Sea Route (NSR) and Northwest Passage (NWP), which we collectively term the Arctic Sea Route (ASR), have become open for navigation more frequently. The ASR connects the Pacific and Atlantic Oceans, with the NSR following the Siberian coast, and the NWP following the north coast of North America. This study evaluated long-term ice concentrations along both routes using microwave data from the SMMR and SSM/I sensors, and analyzed details using data from the AMSR-E passive microwave sensor. The data were used to determine the number of navigable days according to various sea-ice concentrations. Analysis of SMMR and SSM/I data showed a remarkably large number of navigable days on the NSR since 1995. For the NWP, the low resolution of the SMMR and SSM/I data for the Canadian Arctic Archipelago made analysis difficult, but long-term change in the sea-ice distribution on the ASR was indicated. Analysis of the AMSR-E microwave sensor data revealed navigable days along the NSR in 2002 and from 2005 to 2009 (except 2007). For navigation purposes, the sea-ice decrease in specific regions is important, as well as the decrease across the Arctic Ocean as a whole. For the NWP, numerous navigable days were identified in the period 2006–08.
Effects of Pre- and Post-Katrina Nonviolent and Violent Experiences on Male Veterans' Psychological Functioning
Authors: Tharp Andra Teten , Vasterling Jennifer J. , Sullivan Greer , Han Xiaotong , Davis Teri , Deitch Elizabeth A. , Constans Joseph 
Published: September 2011

ABSTRACTBackground: Identifying individuals at risk for mental health problems after a disaster often involves assessing potentially traumatic exposures inherent to the disaster. Survivors of disasters also may have been exposed, both before and during the event, to trauma not directly related to the disaster. A substantial literature suggests exposure to interpersonal violence may have more severe negative outcomes than exposure to non-violent events; however, it is unclear whether violent vs nonviolent exposures before and during a disaster have differential effects on postdisaster psychological functioning.Methods: We examined the associations of violent and nonviolent exposures before and during Hurricane Katrina with postdisaster psychological functioning in a sample of male military veterans.Results: Violent and nonviolent exposures post-Hurricane Katrina as well as pre-Katrina violent exposures were significantly associated with symptoms of posttraumatic stress disorder, panic, and generalized anxiety disorder more than 2 years after the storm. Moreover, veterans who reported violent exposures pre-Katrina were more than 4 times more likely to have reexperienced interpersonal violence during Katrina than those who did not report such exposures.Conclusions: Results suggest assessing disaster-specific experiences in addition to predisaster interpersonal violence may be important for identifying and triaging individuals at risk for postdisaster mental health problems.(Disaster Med Public Health Preparedness. 2011;5:S227-S234)
Building Evidence for Legal Decision Making in Real Time: Legal Triage in Public Health Emergencies
Authors: Hodge James G. , Lant Timothy , Arias Jalayne , Jehn Megan 
Published: September 2011

ABSTRACTSimilar to the triaging of patients by health care workers, legal and public health professionals must prioritize and respond to issues of law and ethics in declared public health emergencies. As revealed by the 2009-2010 H1N1 influenza outbreak and other events, there are considerable inconsistencies among professionals regarding how to best approach these issues during a public health emergency. Our project explores these inconsistencies by attempting to assess how practitioners make legal and ethical decisions in real-time emergencies to further critical public health objectives. Using a fictitious scenario and interactive visualization environment, we observed real-time decision-making processes among knowledgeable participants. Although participants' decisions and perspectives varied, the exercise demonstrated an increase in the perception of the relevance of legal preparedness in multiple aspects of the decision-making process and some key lessons learned for consideration in future repetitions of the exercise and actual, real-time emergency events.(Disaster Med Public Health Preparedness. 2011;5:S242-S251)
Changes in vascular function and structure in juvenile idiopathic arthritis
Authors: Vlahos Antonios P. , Theocharis Paraskevi , Bechlioulis Aris , Naka Katerina K. , Vakalis Konstantinos , Papamichael Nikolaos D. , Alfantaki Sapfo , Gartzonika Konstantina , Mavridis Anestis , Michalis Lampros K. , Siamopoulou Antigoni 
Published: September 2011

AbstractObjectiveChronic inflammatory diseases in adults have been associated with increased cardiovascular risk and impaired vascular function. We aimed to assess the presence of early vascular dysfunction in patients with juvenile idiopathic arthritis (JIA) and investigate the role of inherent inflammatory process of JIA in vascular health.MethodsThirty patients with JIA (age range 7–18 years) were compared to 33 age‐ and sex‐matched controls. Endothelial function (brachial artery flow‐mediated dilation [FMD]), carotid intima‐media thickness (IMT), and arterial stiffness were examined. Endothelial inflammation was assessed by intercellular adhesion molecule 1 (ICAM‐1) and P‐selectin measurements.ResultsPatients with JIA showed decreased FMD compared to controls (P = 0.001), independent of age (P = 0.9 among age subgroups). Baseline differences in erythrocyte sedimentation rate, ICAM‐1, and glucose between the 2 groups accounted for the difference in FMD. The presence of systemic JIA was associated with greater IMT compared to patients with oligoarticular disease, polyarticular disease, or controls (P = 0.014, P = 0.069, and P = 0.046, respectively). The difference in IMT between systemic versus oligoarticular/polyarticular JIA was attributed to the following risk factors: age, body mass index, blood pressure, disease activity, and corticosteroids use. There were no differences in arterial stiffness indices between JIA patients and controls or between patients with systemic versus nonsystemic disease.ConclusionEndothelial function is impaired in patients with JIA at a very young age, while IMT is increased only in the presence of systemic JIA. Vascular dysfunction may be partly attributed to the effects of disease‐related characteristics (inflammation, disease activity, and medications).
Identifying common trajectories of joint space narrowing over two years in knee osteoarthritis
Authors: Bartlett Susan J. , Ling Shari M. , Mayo Nancy E. , Scott Susan C. , Bingham Clifton O. 
Published: September 2011

AbstractObjectiveLittle is known about the natural history of knee osteoarthritis (OA). We sought to identify common patterns of joint space narrowing (JSN) in well‐characterized knee OA patients in the placebo arm of a 2‐year international study.MethodsWe performed secondary data analyses of 622 adults ages 39–80 years in North America (n = 310) and Europe (n = 312) with symptomatic knee OA. Fluoroscopically positioned semiflexed anteroposterior radiographs were obtained at 0, 12, and 24 months. Group‐based trajectory modeling was used to identify distinctive groups of individuals with similar trajectories of JSN, taking into account sex, age, and body mass index.ResultsSeven groups were identified. Four exhibited joint space width (JSW) stability over 2 years representing the most common trajectory (71%), which was unrelated to initial JSW. Atypical courses included slow, rapid, and moderate progressors; most had significant JSN at study entry. Slow progressors (20%) had a mean JSN of 0.2 mm over 2 years. Only 2% of the sample demonstrated rapid JSN (2.1 mm), while 7% had JSN of 0.7 mm. Rapid progressors tended to be men, while slow and moderate progressors were older and heavier.ConclusionMost (70%) people with OA demonstrated no significant JSN over 2 years; 20% showed slow progression, 7% had moderate, and 2% had rapid JSN. Progressors tended to have less JSW at study entry and were older and heavier; rapid progressors were more likely to be men. Understanding common patterns of the course of knee OA may offer new opportunities to target those at greatest risk of disability.