Temperature Gradient Weakening in Snow PDF Download

Author: R. A. Sommerfeld
Publisher:
ISBN:
Category : Depth hoar
Languages : en
Pages : 6

View

Book Description

Author: R. A. Sommerfeld
Publisher:
ISBN:
Category : Depth hoar
Languages : en
Pages : 0

View

Book Description

Author: Xuan Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 242

View

Book Description
Investigation of snow properties can be applied to understand a range of issues including climate change and snow avalanche prediction. Most of the snow properties, i.e. thermal and mechanical, are directly linked to the microstructure of snowpack and those properties evolve simultaneously with deformation of the snow and its metamorphism. Thus, this dissertation primarily explores the characterization of snow microstructural evolution under the effects of temperature gradient and overburden. Snow structural evolution was monitored by the techniques of scanning electron microscopy (SEM), X-ray computed microtomography (micro-CT) and numerical simulation. The temperature gradient setup constructed for this work, commercial compression stage and commercial cooling stage were used to simulate the natural boundary conditions within snow layers. Of the different types of metamorphism that may occur in snow layers, temperature gradient metamorphism (TGM) is perhaps the most significant one. The snow layer undergoing TGM will lose its strength and transform into a weak layer, which is the microstructural cause of avalanches. 1-D arrays of ice spheres were used as a reproducable approach to observe snow microstructural evolution and investigate the mass transfer process. By controlling temperatures on both sides of ice spheres, different vapor transfer directions were studied. Our experiments demonstrated the mass transfer processes and microstructural evolutions under alternating and unidirectional temperature gradient. We also investigated the effects of temperature gradient on natural snow. The specific surface area (SSA) was used to characterize the TGM. The temperature gradient magnitude and the initial snow type both influence the evolution of the SSA. The trend in the SSA is controlled by two mechanisms, grain growth and the formation of complex surfaces. For the relationship between the structure of snow and its mechanical properties, we focused on investigating how the structure of snow evolves under an applied load. Micro-CT images, complemented with SEM images, demonstrate that the mechanical properties of snow depend on the density, the SSA, and bond formation. During our interrupted compression tests, the SSA decreased more rapidly than that determined for snow metamorphism without an overburden. It is clearly evident that pressure sintering of snow contributes to accelerated sintering and coarsening processes.

Author: A. S. Kondratʹeva
Publisher:
ISBN:
Category : Snow
Languages : en
Pages : 20

View

Book Description

Author: United States. Rocky Mountain Forest and Range Experiment Stations, Fort Collins, Colo
Publisher:
ISBN:
Category : Forests and forestry
Languages : en
Pages : 360

View

Book Description

Author:
Publisher:
ISBN:
Category : Forests and forestry
Languages : en
Pages : 184

View

Book Description

Author: Patrick Joseph Staron
Publisher:
ISBN:
Category : Avalanches
Languages : en
Pages : 372

View

Book Description
In the presence of a sufficient temperature gradient, snow evolves from an isotropic network of ice crystals to a transversely isotropic system of depth hoar chains. This morphology is often the weak layer responsible for full depth avalanches. Previous research primarily focused on quantifying the conditions necessary to produce depth hoar. Limited work has been performed to determine the underlying reason for the microstructural changes. Using entropy production rates derived from nonequilibrium thermodynamics, this research shows that depth hoar forms as a result of the snow progressing naturally toward thermal equilibrium. Laboratory experiments were undertaken to examine the evolution of snow microstructure at the macro scale under nonequilibrium thermal conditions. Snow samples with similar initial microstructure were subjected to either a fixed temperature gradient or fixed heat input. The metamorphism for both sets of boundary conditions produced similar depth hoar chains with comparable increases in effective thermal conductivity. Examination of the Gibbs free energy and entropy production rates showed that all metamorphic changes were driven by the system evolving to facilitate equilibrium in the snow or the surroundings. This behavior was dictated by the second law of thermodynamics. An existing numerical model was modified to examine depth hoar formation at the grain scale. Entropy production rate relations were developed for an open system of ice and water vapor. This analysis showed that heat conduction in the bonds had the highest specific entropy production rate, indicating they were the most inefficient part of the snow system. As the metamorphism advanced, the increase in bond size enhanced the conduction pathways through the snow, making the system more efficient at transferring heat. This spontaneous microstructural evolution moved the system and the surroundings toward equilibrium by reducing the local temperature gradients over the bonds and increasing the entropy production rate density. The employment of nonequilibrium thermodynamics determined that the need to reach equilibrium was the underlying force that drives the evolution of snow microstructure. This research also expanded the relevance of nonequilibrium thermodynamics by applying it to a complicated, but well bounded, natural problem.

Author: Bruce Tremper
Publisher: The Mountaineers Books
ISBN: 1594853371
Category : Sports & Recreation
Languages : en
Pages : 322

View

Book Description
CLICK HERE to download the sample chapter "Weather" from Staying Alive in Avalanche Terrain * Provides easy-to-follow instructions on crucial avalanche safety skills * Completely revised with all of the most recent data and techniques * Ideal for snowmobilers, snowboarders, snowshoers, skiers, climbers, hunters, hikers "No one who plays in mountain snow should leave home without having studied this book." -Rocky Mountain News Winter recreation in the backcountry has increased steadily over the years and so has the number of deaths and injuries caused by avalanches. As search and rescue teams are increasingly strapped for funding, self-education has become a larger necessity for snow-sport enthusiasts. The new edition of Bruce Tremper's seminal book is organized according to the structure of American Avalanche Association classes and all chapters have been updated and reviewed by peer experts.

Author: Marcel de Quervain
Publisher:
ISBN:
Category :
Languages : en
Pages : 15

View

Book Description

Author: Wilfried Haeberli
Publisher: Elsevier
ISBN: 0128171308
Category : Science
Languages : en
Pages : 786

View

Book Description
Snow and Ice-Related Hazards, Risks, and Disasters, Second Edition, provides you with the latest scientific developments in sea level rise, permafrost degradation, rock/ice avalanches, glacier surges, glacial lake outburst floods, ice shelf collapses, climate change implications, causality, impacts, preparedness and mitigation. The book takes a geo-scientific approach to the topic while also covering current thinking about directly related social scientific issues that can affect ecosystems and global economies. Special emphasis is placed on the rapidly progressing effects from global warming on the cryosphere, perspectives for the future and latest scientific advances, and technological developments. - Presents the latest research on causality, glacial surges, ice-shelf collapses, sea level rise, climate change implications, and more - Contains numerous tables, maps, diagrams, illustrations and photographs of hazardous processes - Features new insights on the implications of climate change, including increased melting, collapsing, flooding, methane emissions, and sea level rise