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  • Bücher  (37)
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  • Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army  (37)
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  • 1
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-31
    In: Research report / Cold Regions Research and Engineering Laboratory, 31
    Beschreibung / Inhaltsverzeichnis: Summary: Studies were conducted on 58 snow-ice beams (7.5 cm wide, 10.0 cm high, and 56.0 cm long) ranging in density from 0.621 - 0.719 g/cm^3 under varying loads, at uniform loading rates (except for 23 beams which were tested with repeated loading), and at a constant temperature of -5 ± 0.5°C. All beams were tested to failure. The modulus of elasticity of the beams increased with density and loading rate. The modulus of elasticity ranged from 1.35 x 10^4 to 2.22x 10^4 kg/cm^2 for densities of 0.621 - 719 g/cm^3 respectively. A variation in the relative time of deflection from 42 - 23 sec/0.0200 cm gave a variation in the modulus of elasticity from 1.22 x 10^4 to 1.42 x 10^4 kg/cm^2. The modulus of rupture was roughly a linear function of density, increasing from 7.79 - 11.54 kg/cm^2 with density. Failure of the beams was sudden, with a conchoidal fracture occurring in the middle third of the span, and appeared to be a combination of shear and flexure.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 9, A4, B10 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 31
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Method Procedure Test results Tests conducted Data and calculations Discussion of results References Appendix A. Drawings of apparatus Appendix B. Load-deflection and time-deflection curves for snow beams of various densities
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  • 2
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-32
    In: Research report / Cold Regions Research and Engineering Laboratory, 32
    Beschreibung / Inhaltsverzeichnis: Summary: Apparatus was built for deforming ice crystals under hydrostatic pressures up to 350 atmospheres. Single crystals were placed in the mounts in such a way that the deformation occurred by gliding on the basal glide plane. It was found that the shear strain rate increased as the pressure was increased at constant temperature, but that the rate is practically independent of hydrostatic pressure when the difference between the ice temperature and the melting point is kept constant.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 7 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 32
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Test apparatus and experimental procedures Experimental results Conclusions References
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  • 3
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-36
    In: Research report / Cold Regions Research and Engineering Laboratory, 36
    Beschreibung / Inhaltsverzeichnis: Summary: Measurements were made with 22 more or less hydrophobic polymers and lacquers at intervals of 5 or 10 min for periods up to 1 hr. All surfaces were carefully cleaned, and some surfaces were baked. Highest initial (time 0) average contact angles ( 106° - 106.6°) were measured for Foster Snell rain repellant wax, Barrett 25-218 water repellant varnish (air-dried), and Cardolite NRL-7241. After 40 min, contact angles for these substances were 95.6°, 90.9°, and 91.0°. The measurement apparatus is illustrated, and data are tabulated.
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    Seiten: ii, 11 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 36
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Experimental Apparatus Materials Procedure Experimental results References
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  • 4
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-34
    In: Research report / Cold Regions Research and Engineering Laboratory, 34
    Beschreibung / Inhaltsverzeichnis: Summary: The compressive strength of snow cylinders was investigated as a function of age of snow, snow-particle size, and age of the cylinders. The effect of gases such as carbon dioxide, methane, and ammonia on the strength of snow cylinders has also been studied. The experimental results show that the older the snow from which snow cylinders are made, the smaller the compressive strength. The compressive strength of cylinders decreases with the snow particle size. An equation describing the aging curves for snow cylinders is presented. Whereas carbon dioxide and methane in small quantities have no effect on the compressive strength, ammonia appreciably lowers the compressive strength of snow cylinders. All strength measurements were carried out at -10°C.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 16 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 34
    Sprache: Englisch
    Anmerkung: CONTENTS Page Preface Summary Introduction Experimental Materials Apparatus and technique Preparation of snow fractions Experimental results Aging of snow cylinders Compressive strength as a function of particle size Mixture of fractions Influence of gases on the compressive strength of snow Discussion References
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  • 5
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-37
    In: Research report / Cold Regions Research and Engineering Laboratory, 37
    Beschreibung / Inhaltsverzeichnis: Summary: Laboratory experiments on the air permeability of various screened and natural snows are described, and, results are analyzed to determine whether the parameters obtained from the measurements could be used to define a snow type. The permeability of a snow sample of known porosity (calculated from density) was determined over a wide range of air velocities; the sample was then compacted artificially a few mm, its density was determined, and its permeability measured again. The procedure was used to obtain curves for several densities of the same sample. Air flow appeared laminar for velocities less than 5 cm/sec in fine-grained snow (less than 0.8 mm in diam.), 2 cm/sec in medium-grained snow (0.8-1.2 mm diam.), and 1 cm/sec in larger-grained snow. A formula is presented expressing all of the results obtained under laminar-flow conditions in a single relationship, and an equation for estimating grain size from initial permeability and initial porosity is suggested. Snow conversion tables and a discussion of the effect of varying sample porosity on its permeability are appended.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 19, A2, B6 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 37
    Sprache: Englisch
    Anmerkung: CONTENTS Page Preface Summary Introduction Apparatus and method Experimental results and discussion Historical background Range of Darcy's law Effect of porosity on the permeability of snow Bader's equation Conclusion References Appendix I. Snow conversion table: Density to absolute porosity Appendix II. Effect on permeability of varying porosity in the sample Porosity varies with length Porosity varies with cross section
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  • 6
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-33
    In: Research report / Cold Regions Research and Engineering Laboratory, 33
    Beschreibung / Inhaltsverzeichnis: Summary: A series of deformation measurements have been selected for preliminary studies on the plasticity of Greenland glacier ice. The measurements to be reported on were obtained in the Red Rock and TUTO tunnels in Northwest Greenland. Both tunnels were excavated during the summer of 1955 with some additional work done during the summer of 1956. Deformation measurements made up to the end of the 1956 summer season, therefore, are of limited reliability, but certain trends appearing in these data seem worth reporting. The topics discussed are (1) the shearing of an initially vertical peg system at Red Rock, (2) the deformation of core holes at TUTO, and (3) tunnel closure at both sites. These data are analyzed on the basis of laminar flow of the Nye type and certain conclusions are derived.
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    Seiten: 6 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 33
    Sprache: Englisch
    Anmerkung: CONTENTS Introduction Experimental Analysis The shear of glaciers Tunnel closure Conclusions References
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  • 7
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-41
    In: Research report / Cold Regions Research and Engineering Laboratory, 41
    Beschreibung / Inhaltsverzeichnis: Summary: Laboratory experiments on the creep of sifted snow under uniaxial, hydrostatic, and confined-side compressive stresses are described, and the results are discussed on the basis of an additive theory for combined stresses. Stress (4-40 psi) and temperature (-3.6°C to -13.6°C) dependence was investigated for 35 samples (initial density = 0.4 g/cm^3) subjected to uniaxial and hydrostatic stress for 200-sec time increments. Another series of 104 samples (initial densities 0.36-0.63) was subjected to uniaxial, hydrostatic, and confined-side compressive stresses until an arbitrary change in density was reached. In all cases the applied stress ultimately became a shear stress acting between grains, the open structure reacting differently to combined stresses and separate uniaxial stresses. An activation energy of 13,400 cal/mol was obtained from the first group of tests.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 12 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 41
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Experimental General Apparatus Procedure Theoretical relations Additive theory Relationship between tests run for constant change in density and tests for constant time Results and discussion Group I experiments Group II experiments Stress dependence for group II tests Variability Time dependence Activation energy Relations between creep rates under different stress conditions Density dependence Lateral stress for confined-side tests Conclusions References
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  • 8
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-56
    In: Research report / Cold Regions Research and Engineering Laboratory, 56
    Beschreibung / Inhaltsverzeichnis: Summary: The results of laboratory creep tests in a shear apparatus at -5°C on 2 x2 x 3/8 in. samples of commercial ice, artificial single crystals, and 6 types of ice from the Greenland Ice Cap, at shear stresses of about 0.5-3 kg/cm^2 are reported. Some uniaxial tests were made at stresses from 6-28 kg/cm^2 to supplement the shear tests. Creep data could usually be represented approximately by one or more linear sections on a log-deformation vs log-time plot. The linear sections of the double logarithmic curve imply a creep curve of the form ε=ct^m where ε is the strain. For all samples tested, except single crystals sheared in easy glide, m averaged 0. 5 for shear deformations up to about 1%, and approached unity for more deformation. For single ice crystals oriented for easy glide, m averaged 1.7, implying a strain softening. Single crystals oriented for hard glide behaved similarly to polycrystals, indicating a rate-controlling process such as dislocation climb. For all but single easy-glide crystals, the minimum creep rate was tangent to the deformation curve at the end of the experiment. Creep rates for single easy-glide crystals were several hundred times larger than for the other crystals, the flow laws being similar.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 7 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 56
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Types of ice Experiments Results Creep curves Flow law References
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  • 9
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-59
    In: Research report / Cold Regions Research and Engineering Laboratory, 59
    Beschreibung / Inhaltsverzeichnis: Summary: The deflection expression of an infinite plate subjected to a concentrated force is used with the "method of images" to obtain solutions for 6 plates with simply supported edges. The semi-infinite plate, the wedge-shaped plate, and its special case, the rectangular corner plate, are solved in closed form; and the infinite strip, the semi-infinite strip, and the rectangular plate are solved as rapidly convergent series. Behavior under a concentrated force is studied in more detail for the semi-infinite plate and the rectangular corner plate. Relationships for obtaining bending moments, shear forces and reaction distributions as well as derivatives of the kei-function with respect to ? and ? are given in the appendices.
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    Seiten: iv, 12, [2] Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 59
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Introduction and statement of the problem Solution of the boundary value problems for simply supported boundaries Semi-infinite plate Wedge-shaped plate Rectangular corner plate Infinite strip Semi-infinite strip Rectangular plate Remarks on the problem of arbitrary load distribution References Appendix A Appendix B
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  • 10
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-29
    In: Research report / Cold Regions Research and Engineering Laboratory, 29
    Beschreibung / Inhaltsverzeichnis: Summary: A microscopic method for the determination of particle-size distributions of pulverized snow was worked out. The method gives satisfactory distribution curves, presenting the number of particles as a function of their cross-sectional "areas". The measurements were made by means of a filar micrometer eyepiece, the snow particles being placed on a ruled glass slide, which was submerged in silicone oil to prevent evaporation. The time for the determination of a distribution can be appreciably shortened by estimating the size of the particles instead of measuring them, though the accuracy is not so high in this case.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 8 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 29
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Experimental Snow samples Procedure Experimental results Fraction 150-300 µ Fraction 0-150 µ Mixture of fractions Conclusions
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  • 11
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-27
    In: Research report / Cold Regions Research and Engineering Laboratory, 27
    Beschreibung / Inhaltsverzeichnis: Summary: The results of a study on the feasibility of mapping selected snow-cover characteristics for military purposes, taking into account both current synoptic and average conditions, are reported in detail. Problems associated with the construction of isolines for depicting individual or combination of snow-cover conditions are discussed; the need for other statistical parameters in addition to the means is stressed; and the adaptation of frequency and variability indices is suggested. The use of a regional technique, which identified areas somewhat homogenous or substantially different from adjacent areas, is investigated. Problems in mapping snow density are also considered as well as the possibility of estimating snow density from meteorological data. Three sets of codes for the systematic recording and transmission of data are proposed, including a code for ground observers, a simplified code for use where no instruments or trained personnel are available, and a code for aerial observations.
    Materialart: Schriftenreihen ausleihbar
    Seiten: vi, 92 Seiten , Illustrationen , 27 cm
    Serie: Research report / Cold Regions Research and Engineering Laboratory 27
    Sprache: Englisch
    Anmerkung: TABLE OF CONTENTS PREFACE LIST OF TABLES LIST OF ILLUSTRATIONS INTRODUCTION Chapter I. APPLICATION OF ISOLINES FOR DEPICTING ASPECTS OF THE SNOW COVER Visual Problems Use of a simplified base map Other solutions Substantive Problems Observational errors Sampling errors Bias error Effect of reliability of data on isolines Conclusion The ''reasoned distribution'' Effects of substantive problems Conclusion II. DEVELOPMENT OF OTHER MEASURES, INDICES, AND METHODS FOR DEPICTING SNOW COVER CONDITIONS Examples of Possible Normal Indices of Snow Cover Average snow depth at end of the maximum month Average monthly snow depths by superimposed or located line graphs Time aspects Snowfall Selected Statistical Parameters of a Particular Value Extreme values Frequency values Measures of variability Conclusion III. SNOW REGIONS: AN APPROACH TO MAPPING SNOW COVER Snow Region Concept Descriptions of Snow Regions 1. Pacific Coast and Coastal Valley Region 2. The Mountain Zone 3. Great Plains Region 4. The Mackenzie-Manitoba Region 5. Upper Ontario Region 6. Northern Great Lakes-St. Lawrence Region 7. Labrador Region 8. The Northern Arctic Region 9. Ungava-Baffinland Region Conclusions IV. CURRENT SNOW DATA MAPS Introduction Ground Observer's Code Suggested code for "Ground Observer's Snow Report" Comments Symbols for a comprehensive station model Air Observation Code Comments Station Model for Aircraft Snow Observations A Simplified Snow Observation Report . Introduction Proposed code and symbols for station model based on Simplified Snow Observation Report Conclusion Chapter V. MAPPING SNOW DENSITY Introduction Limitations of Data for Mapping Available data Reliability of the data Natural variations in density Snow Density Maps of Eastern Canada Statistical Investigation of Density: Eastern Canada Test for area differences Estimating regional trends in density: Orthogonal polynomials Regional density changes during the winter Conclusions: Statistical investigations Estimating Snow Density from Meteorological Data Relation of density to wind speed and temperature Application of Dmitrieva's equation Conclusion VI. CONCLUSION Snow Cover Maps: Small Scale Compilations of Various Aspects of Their Parameters Preparation of Synoptic Current Snow Data Maps Snow Density Research Investigation of Drift and Erosional Surfaces Initiation of Systematic Collection and Recording of Snow Data Internationally Research Reports Based on Existing Literature .
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  • 12
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-60
    In: Research report / Cold Regions Research and Engineering Laboratory, 60
    Beschreibung / Inhaltsverzeichnis: Summary: This report presents numerical results on the feasibility study of the use of in-ice cooling for a power plant. As a result of this type of arrangement, a water pond under ice is formed. The pond size as a function of time for various operating conditions has been computed. The associated problems such as water temperature, power consumption, etc., are also studied.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 17, A6 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 60
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Open-loop system Method of analysis Time dependence of pond size Temperature of water in the pond Effect of inlet water temperature Effect of convection duct Power consumption for circulation of cooling water Condlusions Closed-loop system Method of analysis Time dependence of pond size Flow conditions of glycol solutions inside coil Discussion and conclusions References Appendix: Examples of calculations
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  • 13
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-62
    In: Research report / Cold Regions Research and Engineering Laboratory, 62
    Beschreibung / Inhaltsverzeichnis: Summary: Adhesive strength of ice for the systems ice/stainless steel and ice/optically flat fused quartz has been investigated as a function of surface roughness of steel surfaces and rates of shear for steel and quartz. The adhesive strength decreases with decreasing roughness of steel surfaces and the force vs time curves for smooth steel plates resemble those of two solids sliding over each other with a liquid layer sandwiched between them. This is particularly so in the case of quartz. The adhesive strength as a function of rate of shear is linear both for ice/stainless steel and ice/quartz; however, there are indications of yield values. The experimental results are in agreement with the assumption of a liquidlike layer on ice. Ratios of viscosity coefficient to the thickness of the layer have been evaluated for both systems and viscosity coefficients are estimated. The importance of interfacial free energy considerations is pointed out.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iii, 10 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 62
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Experimental Materials Apparatus Experimental results Ice/metal interface Ice/quartz interface Discussion References
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  • 14
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-67
    In: Research report / Cold Regions Research and Engineering Laboratory, 67
    Beschreibung / Inhaltsverzeichnis: Summary: The temperature distribution in snow subjected to gamma radiation from an operating nuclear reactor is analyzed mathematically, assuming that the effect of radiation is equivalent to a continuous heat source, the intensity of which is a function of the radial distance from the reactor. Steady-state solutions are derived for two cases: when the radial distance is 13 ft and when it is 19.1 ft. The results indicate that the temperature of the snow in certain regions in the several feet immediately below the foundation will exceed the design limit of 20°F. Increasing the shielding of the reactor will reduce the intensity of the radiation and snow temperature. Other possible ways to reduce the snow temperature include the use of refrigeration coils and the forcing of the atmospheric air through the snow.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iii, 4 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 67
    Sprache: Englisch
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  • 15
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-66
    In: Research report / Cold Regions Research and Engineering Laboratory, 66
    Beschreibung / Inhaltsverzeichnis: Summary: A simple theory is proposed for crack formation and development by soil desiccation on the basis of laboratory experiments utilizing soil samples (Bloomington till) with max particle size of 1 mm diam. held in flat wooden containers. The crack pattern is more dependent on the thickness of the soil sample than on temperature or humidity. Some effect is caused also by differences in the bottom material of the containers. The area of cells made by crack patterns has a log normal size distribution. Total length of cracks decreases with increase in sample thickness. The number of sides of cells also depends on the thickness. Cracking was found to begin from the center of the soil layer and to propagate to the surface or bottom with non-uniform speed.
    Materialart: Schriftenreihen ausleihbar
    Seiten: vi, 48, A4 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 66
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Soil material Soil Preparation of the soil material Containers Temperature and humidity of the air Moisture content and dry density of the soil Experimental procedures and results General procedures Definition of the characteristics of cracking of soil Cracking moisture content Size of cells made by cracking of the soil Length of cracks Number of sides of cells Development of cracks Additional experiments Interfacial fracture markings Method of auxilliary tests on physical properties of the soil Elastic constants of the soil Shrinkage of soil due to desiccation Tests of the adhesion between the soil and the bottom material Results of auxiliary tests Elastic constants of the soil Free shrinkage process of the soil due to desiccation Adhesion between the soil and glass or wood Mechanism of crack formation due to the desiccation of soil Geometric interpretation Mechanical interpretation Conclusions References Appendix: Table of experiments
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  • 16
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-46
    In: Research report / Cold Regions Research and Engineering Laboratory, 46
    Beschreibung / Inhaltsverzeichnis: Summary: The results of studies in the summer of 1957 on ice samples taken from the ice tunnel at TUTO, core samples obtained by drilling in the ice cap at Site 2, and snow samples, using the transverse vibration method and a new portable meter, are reported. Young's modulus was determined from the resonance frequency of flexural vibrations of samples cut in the form of rectangular bars; the loss factor was measured from damping; and the coefficient of viscosity calculated using the Maxwell model. The modulus of elasticity of samples of a density from 0.917 - 0.90 g/cm^3 (tunnel ice) decreased sharply with slight deviations of the density from that of pure ice. At densities from 0.90 - 0.50 g/cm^3 (deep-pit and drill-core samples) the relation between the modulus of elasticity and density was linear, while in the density range from 0.50-0.25 g/cm^3 (surface snow) the modulus of elasticity decreased exponentially. The viscosity-density relation of the samples was similar to that of elasticity vs density. Young's modulus increased slightly with decreasing temperature, while viscosity increased exponentially. The activation energy was calculated as 18.7 kcal/mol for old ice-cap ice, 13.9 kcal/mol for tunnel ice with elongated bubbles, and 13.5 kcal/mol for super-imposed ice.
    Materialart: Schriftenreihen ausleihbar
    Seiten: v, 29, A4 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 46
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Principle of measuring the visco-elastic nature of snow and ice by the vibration method Experimental method for determination of visco-elastic properties of snow and ice Visco-elastic properties of tunnel ice Elastic properties of snow samples from the deep pit Elastic properties of core samples obtained by drilling Elastic properties of snow near the ice-cap surface Vertical variation of Young's modulus near the surface Wind-packed snow Peter snow Relation between Young's modulus and density of snow Relation between Young's modulus and density over the range from surface snow to ice Supplementary experiments on the elastic nature of snow and ice at Site 2 Anisotropy of Peter snow Age hardening Temperature dependence of Young's modulus of core ice Viscosity measurement of snow and ice in Greenland Further experiments on the elastic nature of tunnel ice Temperature dependence of Young's modulus Frequency dependence of Young's modulus Further experiments on the viscous nature of tunnel ice Temperature dependence of loss factor Activation energy Frequency dependence of loss factor and viscosity Relation between viscosity and density Conclusions References Appendix: Experimental data
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  • 17
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-51
    In: Research report / Cold Regions Research and Engineering Laboratory, 51
    Beschreibung / Inhaltsverzeichnis: Summary: The study was made in order to simulate the deformation of a tunnel in glacier ice and compare the results with the theoretical value derived from compression or tension tests. The plastic deformation of commercial polycrystalline ice and manufactured snow-ice was determined by measuring the discharge of oil from the cavity of closed hollow ice cylinders subjected to high external pressure in an oil-filled pressure chamber. The deformation vs time curves were similar to those obtained in compression or tension tests. The relationships between minimum strain rate and applied pressure, or between minimum strain rate and the circumferential stress at the surface of the inner cavity, were found to differ from the power law ϵ ̇= ασⁿ, the value of n being an increasing function of stress. Analysis of time deformation curves indicates that viscoelastic models proposed by former investigators do not apply to the mechanism of the plastic deformation of ice.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 10 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 51
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Apparatus Specimens Experimental procedures and results Analysis of the data Discussion References
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  • 18
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-52
    In: Research report / Cold Regions Research and Engineering Laboratory, 52
    Beschreibung / Inhaltsverzeichnis: Summary: The results of studies on the physical properties of fog whiteout, as it occurred at Site 2 on the Greenland Ice Cap in the summers of 1956 and 1957, are reported and compared with the results of other studies; the instruments, methods of measurement, and data-reduction techniques used are described; and attempts at dissipating whiteout by AgI (silver iodide) seeding are discussed briefly. Emphasis was given to measurements of fog-particle size distribution, liquid-water content, relative humidity, visibility, and atmospheric nuclei. The data are tabulated. The synoptic situations for 2 selected cases of fog whiteout at relative humidities of less than 100% (possibly because of the presence of salt solutions) are described; and the balance between the rate at which water is made available in the air as it is lifted over the Ice Cap and the rate of water flux to the snow surface is computed using various equations. Efforts at fog dispersal by AgI seeding from the ground were inconclusive.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 18, A1 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 52
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Definition of whiteout Scope of this study Instrumentation and observations Location of project: Fog particle measurements Atmospheric humidity measurements Visibility measurements Air temperature measurements Radiation measurements Atmospheric nuclei Observations of fog whiteout Conditions prior to onset of whiteout Conditions at time of arrival and during whiteout Micro-structure of fog whiteout Analysis of moisture balance during two selected cases Synoptic situation for case 1 Synoptic situation for case 2 Computations Attempts at fog whiteout dispersal References Appendix A - Freezing nuclei observations Appendix B - Absolute humidity gradient data
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  • 19
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-53
    In: Research report / Cold Regions Research and Engineering Laboratory, 53
    Beschreibung / Inhaltsverzeichnis: Summary: The results of investigations on the structural changes of Greenland snow during age-hardening in the first 49 hr after ejection by a Peter snow miller from a trench 4.7 ft deep are reported, and the method of study is described. The samples of snow were taken at various distances from the trench 1, 3, 14, 25, and 49 hr after deposition, and their changes were studied as a function of time and distance from the trench. The porosity remained constant at an average of 50 ± 3%. The number of grains/cm^2 decreased with time and increased with distance from the trench because of the different speeds of sedimentation and wind sifting. The mean grain cross-section showed a similar dependence. The relative length of grain boundaries increased with time and slightly with distance from the trench, while the mean length of new grain-to-grain boundaries increased with age and decreased with distance from the trench. The mean number of adjacent grains per grain vs. relative length of grain boundaries showed a linear relation. A slight increase of new boundaries with increasing number of neighbors was also observed. Suggestions for a precise study of the age-hardening process of snow are made.
    Materialart: Schriftenreihen ausleihbar
    Seiten: v, 15, A5 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 53
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Methods of testing Sampling Preparation of samples Preparation of structure pictures Results Influence of time and place Porosity Number of grains/cm2 Mean grain cross section Relative length of grain boundaries (KM ratio) Mean number of adjacent grains per grain Number of new boundaries/cm 2 Mean length of new grain-to-grain boundaries Some interrelations of the structure data Structure of a 1-yr old Peter snow Suggestions for an exact study of the age-hardening process of snow References Appendix: Structure pictures
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  • 20
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-55
    In: Research report / Cold Regions Research and Engineering Laboratory, 55
    Beschreibung / Inhaltsverzeichnis: Summary: Experiments were performed to investigate the processes involved in the formation of sorted patterns which occur naturally in unconsolidated sandy gravel deposits covering the edge of the ice cap southeast of Thule, northwest Greenland. Four different glacier ice surfaces were covered with various thicknesses of sandy gravel in order to observe the effect of differential melting on the formation of sorted patterns. The different stages of pattern formation were recorded by photographs taken at 7-day intervals. A thin gravel cover of 2 in. allowed more rapid melting than did a cover of 6 in., with the result that depressions and mounds were formed. Coarse particles were segregated in the depressions by natural sorting of the various particle sizes when set in motion by differential melting and resulting uneven collapse of the gravel cover. The sorting produced well-developed stone rings in three of the areas, caused directly by the differential insulation provided by the gravel cover. In the fourth area a uniform gravel cover over a smooth ice surface produced no sorted nets, although a poorly developed stone stripe was formed in a melt-stream channel. A stone stripe was also formed in a stream channel cut into the ice along the edge of the test area. This stripe was composed of coarse particles which rolled down from the better insulated heights of the test area. It is therefore possible that sorted nets and stripes occurring naturally in the moraine deposits on the edge of the ice cap could have been formed by mechanical sorting induced by differential melting of the ice under a non-uniform layer of sandy gravel.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 15 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 55
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Procedure Preparation of test plots Measurements of ice and gravel surfaces Composition of the gravel covering Results Sorting in a smooth layer of sandy gravel over an uneven ice surface Sorting in a uniform layer of sandy gravel over depressions in the ice surface Sorting in a uniform layer of sandy gravel over a uniform ice surface Sorting in a non-uniform layer of sandy gravel over a uniform ice surface Discussion and recommendations Conclusions References
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  • 21
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-26
    In: Research report / Cold Regions Research and Engineering Laboratory, 26
    Beschreibung / Inhaltsverzeichnis: Summary: The results of temperature, density, ram-hardness and grain-size measurements at 118 test sites along a 300-mi. traverse, ranging in elevation from 2000 to 8000 ft, are reported in detail, and their meteorological and climatic implications are discussed. Four types of diagenetically produced facies were recognized: ablation facies, extending from the snout of the glacier to the firn line; soaked facies, extending from the firn line to the saturation line; percolation facies, extending from the saturation line to the dry-snow line; and dry-snow facies, extending across the glacier above the dry-snow line. The well defined saturation line shows marked discontinuities in temperature, density, and ram hardness, while the dry-snow line is a transition 1 zone 10-20 mi. wide. The recognition of facies allows greater resolution of glacier characteristics than Ahlmann's classification, permitting quantitative subdivision of all types of large glaciers. Regional precipitation (entirely from cyclonic storms) is about 5 times greater than at Thule; and the prevailing katabatic winds control the vertical component of the temperature gradient in the snow and firn. The depth density curve of the firn at elevations where melt is negligible is invariant with time, as in Sorge's law, so that the densification can be treated as a steady-state situation with load as the only significant variable.
    Materialart: Schriftenreihen ausleihbar
    Seiten: vii, 62, A4, B2, C2 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 26
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Chapter I. Introduction Greenland Glaciers and stratigraphy The Greenland ice sheet - a rock formation Region of investigation Chapter II. Methods of investigation Stratigraphy Accumulation measurements Work program at pit stations General description of pits Temperature Hardness Density, stratigraphy, and grain size Accuracy of density measurements Photography Core drilling Air permeability and mechanical tests Elevation measurements Barometric altimetry Transit leveling Chapter III. Basic concepts and definitions Summer melt Soaking Complete soaking Localized percolation Stability Diagenetic facies Chapter IV. Presentation and discussion of results Grain size and morphology Grain size Morphology Temperature Seasonal variation and mean annual temperature Thermal effect of an open pit Constancy of climate Facies in terms of temperature data Hardness Continuity of strata Effect of wind Increase in R with depth below snow surface Facies in terms of hardness data Density Depth vs density data Depth vs load data Attempts to formulate depth vs density Facies in terms of density data Glacier facies - a classification of glaciers Chapter V. Stratigraphy and accumulation Stratigraphy Stratigraphic interpretation at station 1-0 Correlation between stratigraphic and meteorological records Accumulation Integrated qepth-density curves Measurement of accumulation on surface marker plates Pole-marker measurements Stratigraphic correlation Selection of a reference datum in the annual stratigraphic sequence Correlation across the traverse Effects of topography Chapter VI. Meteorological and climatological implications Winds Precipitation Annual heat exchange References Appendix A: Stratigraphy, meteorology and glaciology Appendix B: Logistics and development of the research program Appendix C: Tables
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  • 22
    Signatur: ZSP-202-74
    In: Research report / Cold Regions Research and Engineering Laboratory, 74
    Beschreibung / Inhaltsverzeichnis: Summary: The heat exchange of a snow cover was studied with respect to the effects of heat transfer processes on metamorphic action within the snow cover and the prediction of heat fluxes and the resulting changes in snow cover characteristics from standard meteorological information. Data collected at the USA SIPRE Keweenaw Field Station, Houghton, Michigan, were used to determine heat transfer by thermal radiation, convection, and conduction. The percent of daily incident solar radiation at the outer limits of the earth's atmosphere which reaches the snow surface ranged from 94 with clear skies to less than 20 with an overcast less than 1000 ft high and precipitation. Average diurnal patterns of total solar radiation may be estimated for various cloudiness. Total solar radiation with overcast clouds less than 5000 ft high averaged about 70% of the clear-sky radiation. Atmospheric radiation related to temperatures during clear nights gave a curve paralleling the black body radiation curve, although about 7 ly/hr lower in absolute values. Atmospheric radiation during clear skies was about 9 ly/hr less than that with low overcast conditions with no snow falling. In the presence of falling snow, total hemispherical radiation was about 5 ly/hr greater than with no snow falling but with' similar low overcast cloudiness. With low overcast cloudiness, the net long-wave exchange averaged about -17 ly/day in January and -8 ly/day in February. With clear skies the net long-wave exchange averaged about -128 ly/day in January and -120 ly/day in February. The net radiation exchange with clear skies during midday remained slightly negative in January and became increasingly positive through February. The highest positive values of net radiation occurred during the day with low overcast or broken cloudiness and precipitation. The largest net radiational loss of 9 ly/hr occurred at night with clear skies and nearly calm winds. The average magnitude of surface temperature inversions over snow was related to observations of cloudiness and wind speeds for both day and night. With winds of 12 knots or greater, the temperature difference in the first 10m was usually near adiabatic even with clear skies at night. During the day inversions seldom exceeded 1-2°C, and a slight lapse commonly occurred during low overcast conditions and moderate winds. The Liljequist method for computing turbulent heat transfer and conductive heat transfer in snow was used. Average air temperature is shown to exert a pronounced effect upon snow heat conduction, cold content and temperature profile. Average temperature differences through the snow, responsible for metamorphic action leading to the formation of depth hoar, can be estimated by a knowledge of the previous 20-hr average temperature. Snow hardness distributions, indicators of supporting capacity of snow, can be estimated graphically from snow density and depth observations.
    Materialart: Schriftenreihen ausleihbar
    Seiten: v, 73 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 74
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Part 1. Data analysis Introduction Estimating snow temperature distributions from meteorological information Radiative heat transfer Short-wave radiation Long-wave radiation Net radiation exchange Convective heat transfer Liljequist method Monin-Obukhov method Conductive heat transfer Heat transfer in soil Heat transfer in snow Direct relationships Measurement of snow properties Cold content of snow Vertical temperature gradient in snow and its effects Snow hardness Summary of the analysis Thermal radiative heat transfer Convective heat transfer Heat transfer processes in soil and snow Part II. Tabulated data for Keweenaw Field Station Description of data Location and periods of measurement Instrumentation Data processing Explanation of tables Thermal radiation data, Keweenaw Field Station References
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  • 23
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-61
    In: Research report / Cold Regions Research and Engineering Laboratory, 61
    Beschreibung / Inhaltsverzeichnis: Summary: The results of experiments on the bonding of polished and microtomed surfaces of bubble-free ice samples at -5°C with various loads are reported. Only a small part of the available surface area appeared to be bonded, this area increasing with the bonding load. Surfaces apposed immediately after preparation showed an appreciably higher force of separation than those joined after a time interval. The force of separation for surfaces placed together at 0% relative humidity was higher than that at 100% relative humidity. A simplified theory of bonding of irregular ice surfaces is formulated in the appendix. The calculations are based on the assumption of a distribution of small ice cylinders of equal cross sections but different heights located on a non-deformable plate. The cylinders are deformed by a constant force which is applied by another completely non-deformable flat plate. The deformation as a function of force and time and the force of separation as a function of load are derived, assuming that the distribution of heights is given by a box distribution (i.e., frequency of heights is constant).
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 6, A4 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 61
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Materials Apparatus and procedure Results Discussion References Appendix: Compression of an assembly of cylinders
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  • 24
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-63
    In: Research report / Cold Regions Research and Engineering Laboratory, 63
    Beschreibung / Inhaltsverzeichnis: Summary: Experiments have been carried out on the plastic deformation of thick-walled snow-ice cylinders under hydrostatic pressure as a function of pressure and temperature. At constant circumferential stress and temperature the natural strain rate of closure is a constant. This constant varies with the circumferential stress according to a sine function and is exponentially dependent on temperature with an energy of activation of 14.1 kcal/mole at an average circumferential stress of 3.1 kg/cm^2. The mechanism of the plastic flow is in agreement with a mechanism proposed previously, that is, flow between grain boundaries takes place.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 7 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 63
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Experimental Materials Apparatus Experimental results Deformation under constant hydrostatic pressure Deformation as a function of hydrostatic pressure Deformation as a function of temperature at constant pressure Discussion References
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  • 25
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-69
    In: Research report / Cold Regions Research and Engineering Laboratory, 69
    Beschreibung / Inhaltsverzeichnis: Summary: The relations between rate of snow accumulation, snow density, snow age, and depth below the surface are formulated in terms of a compactive viscosity factor, which is assumed to be a function of only density and temperature, with parameters which will vary with the snow-type sequences of different climatic areas of high polar glaciers. The theory could be useful in an analysis of the data obtained from the large number of snow pits in Greenland, Ellesmere Island,and Antarctica.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 8 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 69
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction The Sorge depth-density curve Generalization for time-variable rate of accumulation Path of a particle on the surface y=B(h,t) Effect of temperature Computational procedure Densification under high loads References
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  • 26
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-64
    In: Research report / Cold Regions Research and Engineering Laboratory, 64
    Beschreibung / Inhaltsverzeichnis: Summary: The distribution of temperature throughout an idealized ice cap is studied. The idealized ice cap is considered as one with a constant growth rate, without internal movement, subject to a linear climatic change and to a constant geothermal influx. The problem is treated as a Stefan-type problem and the solution is obtained by the principle of superposition. The results indicate that the temperature at the base of the ice cap rises with time and eventually would reach the melting point of the ice. Under such conditions, it is concluded that the ice cap is not resting on a permafrost base as suggested by previous investigation.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 8 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 64
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Mathematical development Method of solution Discussion of results Base temperature Minimum temperature Effect of rate of growth Effect of geothermal influx Comparison with observed results References
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  • 27
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-71
    In: Research report / Cold Regions Research and Engineering Laboratory, 71
    Beschreibung / Inhaltsverzeichnis: Summary: The depth-density relationship of the surface snow to 30-ft depth at three locations on the Greenland Ice Cap east of Thule is presented. Rates of accumulation and densification deduced from the pit studies are used in elementary mathematical expressions developed in this report. These expressions describe a densification process applicable to continuously accumulating polar snow, between the depths of 10 and 40 ft. Loads, densities, and rates of densification are presented in relation to depth and time and applied to problems of undersnow military construction.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 10 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 71
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Field investigations Application of profile data Densification theory Engineering applications References
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  • 28
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-70
    In: Research report / Cold Regions Research and Engineering Laboratory, 70
    Materialart: Schriftenreihen ausleihbar
    Seiten: 93 Seiten , Karten
    Serie: Research report / Cold Regions Research and Engineering Laboratory 70
    Sprache: Englisch
    Anmerkung: CONTENTS: Preface. - Summary. - Chapter I. Introduction. - Operations and logistics. - Chapter II. Methods of investigation. - Region of investigation. - Pit studies. - Elevation measurements. - Chapter Ill. Stratigraphy and accumulation. - Introduction. - Diagenesis without melt. - Diagenesis with melt. - Diagenetic facies defined on glaciers. - Grain size. - Description of three stratigraphic features. - Principles of stratigraphic interpretation. - Selection of a reference datum in the annual stratigraphic sequence. - Stratigraphic correlation. - Distribution of annual accumulation. - Independent checks on the stratigraphic interpretations. - Chapter IV. Temperature distribution. - Seasonal temperature variation on the snow surface. - Seasonal temperature variation below the snow surface. - Distribution of mean annual temperature on the ice sheet. - Chapter V. Diagenetic facies- a classification of glaciers. - Temperature. - Hardness. - Density. - Glacier facies - a classification of glaciers. - Chapter VI. Densification of snow and firn. - Load-volume relationship. - Depth-density relationship. - Chapter VII. Climatological implications. - Introduction. - Katabatic winds and accumulation. - Annual heat exchange. - The balance of the Greenland Ice Sheet. - References. - Appendix A: Stratigraphy, meteorology and glaciology. - Appendix B: Mean annual temperature. - Appendix C: The data sheets.
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  • 29
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-30
    In: Research report / Cold Regions Research and Engineering Laboratory, 30
    Beschreibung / Inhaltsverzeichnis: Summary: Deformations occurring in a tunnel, two trenches, and a 30 m deep pit excavated in the Greenland névé in the summer of 1954 have been measured over a period of 2 years. The experimental results indicate that closure rates increase with lateral distance from a restraining boundary up to distances of about 1 m. At larger distances, the effect of the boundary is not appreciable. Closure rates for deep excavations are not found to be strongly depth-dependent. This is due to a roughly parallel increase of viscosity and pressure with depth. Vertical compaction results from the pit agree well with those calculated from the depth-density relation using Sorge's Law. A theoretical calculation for the tunnel and pit closure, which is a modification of existing theories for the deformation of an elastic, compressible, thick-walled cylinder, is in fair agreement with the observed deformations. From this agreement it appears that the flow behavior of the névé can be described on the basis of a Newtonian viscosity. The trench closure is described as the-squeezing out of horizontal layers, fixed at some distance from the trench, and modified only slightly by the drag of neighboring layers. Measurements will be continued during future summers.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 14 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 30
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Measurements and results Tunnel North-south trench East-west trench Deep pit Theoretical development Sorge's Law Deformation of acylindrical tunnel in a viscous compressible medium Discussion Tunnel Trenches Deep pit References Appendix
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  • 30
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-39
    In: Research report / Cold Regions Research and Engineering Laboratory, 39
    Beschreibung / Inhaltsverzeichnis: Summary: An analysis of snow-cover density, temperature, and hardness data, measured over a period of several years at five stations in Alaska and six stations in the Canadian Arctic, shows the snow cover in the Canadian Archipelago to be colder, denser, and harder than in the interior of Alaska. A series of nomographs were developed to estimate average monthly snow-cover density from mean monthly air temperature and wind velocity. The nomographs are applicable for the months November through March, for the Alaskan and Canadian area north of 62°N latitude, and for elevations below 1500 ft. A comparison of observed snow-cover densities with those derived from the nomographs indicates that the method will provide a reliable regional estimate of snow-cover density. Studies of the relation between snow-cover temperature and air temperature from November through March disclosed the snow to be on the average from 4°C to 9°C warmer than the air at the Alaskan stations and 4.5°C warmer at the Canadian Archipelago stations. An investigation of snow-cover hardness revealed regional variations similar to that for density. Measured snow hardness during the period of no melting was found to be related to densities between 0.15 and 0.36 g/cm^3.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 9 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 39
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Climatic parameters which may affect arctic snow-cover density Results of study Regional variations in snow-cover density Prediction of average monthly snow-cover density in the arctic from air temperature and wind velocity Comparison of observed snow-cover density with density computed from the nomographs Relation between snow-cover temperature and air temperature Relation between hardness and density of the snow cover References
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  • 31
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-42
    In: Research report / Cold Regions Research and Engineering Laboratory, 42
    Beschreibung / Inhaltsverzeichnis: Summary: The results of petrofabric studies in the laboratory on five samples of high-density snow collected in 1954 and 1955 at depths of 8.0, 15.5, 23.0, 34.2, and 46.3 m in a pit at Site 2 are reported. The porosity of the samples, the number of grains/cm^2, the mean number of adjacent grains per grain, the mean grain cross section, the size distribution of grain cross sections, and the orientation of c-axes were determined from enlarged photomicrographs of thin sections, using reflected light and transmitted polarized light. The number of adjacent grains per grain, the ratio of free to occupied grain surface, and the sphericity clearly depended on porosity and on each other. There was no strong relation between these data and the number of grains/cm^2. Hence, the structure of high density snow can be satisfactorily described by the porosity and the number of grains/cm^2 . Conclusions from a two-dimensional thin section can be applied to a spatial sample only if the sample is isotropic by strata.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 24 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 42
    Sprache: Englisch
    Anmerkung: CONTENTS Page Preface Summary Introduction Methods of preparation Measurements of structural properties Measurements on homogeneity and isotropy Results Structure data Orientation of c-axes Analysis of the distribution of the orientation of c-axes Preferred directions of the fabric Distribution of grain cross sections Size and shape of the counting areas Interrelations of the structure, data Conclusions Recommendations for further studies References
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  • 32
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-43
    In: Research report / Cold Regions Research and Engineering Laboratory, 43
    Beschreibung / Inhaltsverzeichnis: Summary: Charts of mean annual air temperature and precipitation over the ice cap are constructed on the basis of snow-profile studies at 8 locations, data collected for several years after 1953 at two U.S. Air Force weather stations, and records from expeditions since 1930. The warming trend in the Arctic appears to have occurred to a lesser degree on the ice cap, possibly because of the effect of the snow cover. The lowest mean annual temperature in South Greenland is estimated to occur within the area bounded by the 2500 m contour and the -18°C isotherm; mean annual temperature at 2700 is estimated as -20.9°C. In North Greenland, the mean annual temperature at 1700 m is estimated at -22°C. The presence of ice glands in the snow and daily max summer temperatures, estimated from records of coastal stations, indicate a potentially high incidence of melting at about 1300 m elevation and some melting at 1700 m in North Greenland, and melting up to 2700 m in the South. Annual accumulation is 2-3 times as great at 2500 m on the west side of the ice cap as at the crest. South of 66°N, precipitation may be about twice as great on the east side of the crest as in the west.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 9 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 43
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Derivation of mean annual air temperature data Annual accumulation References
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  • 33
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-18
    In: Research report / Cold Regions Research and Engineering Laboratory, 18
    Beschreibung / Inhaltsverzeichnis: Summary: Various strength properties of naturally compacted high-density snows, in the density range of from 0.40 to 0.75 g/cm^3, are reported. Test results are given for: unconfined compression; unconfined and confined double shear; ring, flexural, and centrifugal tensile strength; torsional shear; and work of disaggregation. The work of disaggregation per unit volume was related to crushing, tensile, and shear strength at various lateral pressures, using the same empirical relationship. The results of the various tests measuring the tensile strength of the snow compare favorably with each other. An attempt was made to use the direct shear strength results in Coulomb’s equation for the determination of Mohr’s envelope of rupture for snow. These tests yield higher values than those obtained in unconfined compression tests. However, angles of internal friction obtained considering Mohr’s envelope to be straight line seem to agree with measurements taken on an unconfined compression specimen.
    Materialart: Schriftenreihen ausleihbar
    Seiten: 19 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 18
    Sprache: Englisch
    Anmerkung: CONTENTS Page Preface Summary Introduction Temperature correction factors Crushing strength Tensile strength · Shear strength Torsional shear strength Work of disaggregation of snow Angle of internal friction and apparent unit cohesion Discussion of results References
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  • 34
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-17
    In: Research report / Cold Regions Research and Engineering Laboratory, 17
    Beschreibung / Inhaltsverzeichnis: Summary: The ice-cored moraine which occurs on the margin of the Greenland Ice Cap, east of Thule Air Base, was investigated during the summers of 1954 and 1955. A synthesis of the field data gathered leads to the following conclusions: 1.) The outer zone of the ice margin is composed of stagnant ice which acts as a barrier to movement of mobile ice from the interior. 2.) The mobile ice overrides the barrier zone in a series of high angle imbricate shears. 3.) These shears carry old ground moraine from the subglacial floor toward the surface. 4.) Differential ablation on the surface results in the formation of ice-cored moraine ridges, parallel to the strike of the shear. 5.) Recent stagnation and recession of the ice margin in the Thule area has resulted in the formation of a belt of successive shear moraines. 6.) Geomorphic processes in addition to ablation (particularly wind action) control the surface expression of the shear moraines. 7.) Subglacial topography is the primary control on the trend of both ice edge and moraine ridges. 8.) The complex Thule Ramp shear moraine has resulted from a faster-moving ice mass to the north overriding the Thule Ramp ice. 9.) The prominent ice cliffs are manifestations of erosion by wind and water. 10.) The tunnel in the Thule Ramp ice cliff indicates a former development of shear moraine in the area. 11.) Structural and geomorphic features indicate glacial cycles in the area of both long and short duration. 12.) The shear moraines in the Thule area offer a possible explanation for the mode of ground moraine deposition in some areas of continental glaciation during the late Pleistocene. The work done in 1954 and 1955 was in the nature of a glacial geomorphologic reconnaissance. Intensive study remains to be done, particularly in the Thule Ramp area, on ice structure, movement, and ablation before a complete understanding of both present and past glacial regimes can be reached.
    Materialart: Schriftenreihen ausleihbar
    Seiten: vi, 46, [2] Seiten , Illustrationen , 27 cm
    Serie: Research report / Cold Regions Research and Engineering Laboratory 17
    Sprache: Englisch
    Anmerkung: CONTENTS Introduction I. Physiographic description of study area II. Structure of the marginal zone of the ice cap III. Geomorphologic processes IV. Recent glacial history of the ice margin
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  • 35
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-20
    In: Research report / Cold Regions Research and Engineering Laboratory, 20
    Beschreibung / Inhaltsverzeichnis: Summary: Investigations on sea ice at Hopedale, Labrador, March 1956, included: small beam tests and in-place cantilever beam tests for flexural strength; ring tensile-strength tests; unconfined compression tests, with stress-strain studies to determine "Young's modulus"; and double shear tests. The results exhibit a great deal of scatter, primarily due to the inhomogeneity of sea ice. Ring tensile strength values range between 3.3 kg/cm^2 and 22.3 kg/cm2 between -2.5°C and -19.1°C. The small beam tests give flexural strength values from 0.5 to 17.3 kg/cm^2 in a similar temperature range. The in-place pull-up cantilever beam tests give flexural strength values of 2.2 to 4.0 kg/cm^2, with much less scatter. Crushing strength values range from 26.3 to more than 107 kg/cm^2 in the range -4.9°C to -18.3°C. Values for Young's modulus obtained from the slope of the straight line portion of the stress-strain curves in compression ranged between 4520 and 10,225 kg/cm^2. There is a temperature dependence, explained by the effect of change in brine content, on sea-ice structure. The double shear tests give values of 7.8 to 34.2 kg/cm^2 in the range -5.5°C to -12.8°C. These are higher than the tensile-strength values. These failures occurred normal to the direction of growth, while the tensile strength was obtained with failure parallel to it.
    Materialart: Schriftenreihen ausleihbar
    Seiten: 15 Seiten , Illustrationen
    Serie: Research report / Cold Regions Research and Engineering Laboratory 20
    Sprache: Englisch
    Anmerkung: CONTENTS Page Preface Summary Introduction Ring tensile strength Flexural strength of small beams Flexural strength of inplace beams Crushing strength Shear strength Discussion of results References
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  • 36
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-19
    In: Research report / Cold Regions Research and Engineering Laboratory, 19
    Beschreibung / Inhaltsverzeichnis: Abstract: Measurements were made of global and net radiation between 6 July and 7 August 1955 at a site on the Greenland Ice Cap located near 78°N latitude and at an elevation of 6800 ft. Snow-surface temperatures during this period were below 0°C and mean cloudiness was 0.7. Total incident global radiation measured during the 33-day period amounted to 20,628 ?? of which only 3059 ??, or about 15%, were absorbed by the snow cover. Most of the absorbed global radiation was re-emitted as long-wave radiation, so the net gain during the observation period amounted to not more than 7.6 ??/day. Diffuse sky radiation amounted to only 19% of all incoming global radiation measured at the ice-cap research site. In the temperate zone, diffuse sky radiation amounts to 30% or more of the incoming radiation. The small amount of diffuse sky radiation indicates low atmospheric turbidity in this polar climatic zone. Incident global radiation was reduced by 6% in the presence of a 0.5 cloud cover. Under full overcast conditions the snow surface received 65% of the global radiation measured on clear days. In the temperate zone as little as 30% of global radiation reaches the earth under full cloud cover. The large amount of global radiation received in the Arctic under full cloud cover is the primary cause of one form of arctic white-out. Accompanying the small decrease in global radiation caused by cloudiness is a large decrease in effective outgoing long-wave radiation, with an increase in the net radiation balance. This condition contributes to a greater potential ablation of the snow and ice cover during cloudy seasons. The long-wave radiation balance at this site on the ice cap was always negative during the period covered by this study. Errors associated with the measurement of solar radiation at the low sun angles which prevailed at the research site were found to be about -3%. No correction was applied to the basic data, however, since there were insufficient data to establish the consistency of this error over the period of observation. During periods of blowing and drifting snow, 6% more global radiation was measured at 1.25 m above the snow surface than at 5.7 m elevation. The increase may be due to multiple reflection within the layer of blowing snow. The atmospheric transmission coefficient at the ice-cap site was found to be 0.968. This high value was associated with the low atmospheric turbidity. The heat balance of the snow cover as computed from the radiation measurements and a temperature profile in the snow was found to be 7.6 ??/day at the ice-cap site. This is a negligible heat gain when compared with the 400 ??/day gain by a spring snow pack in the Sierra Nevada of California. For the entire season when the sun is above the horizon, the estimated net gain by the ice cap is 1000 ??, no more than a 2-1/2-day heat supply used in melting the snow of the High Sierra. Some measurements made with a silicon solar battery similar to those developed by the Bell Telephone Laboratories indicate that it may have a significantly higher efficiency on the ice cap than in the more temperate zone. Verification of this apparent increase in efficiency and the causes for it require further study of the performance of the p-n junction cells in the Arctic.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 20, [2] Seiten , Illustrationen , 27 cm
    Serie: Research report / Cold Regions Research and Engineering Laboratory 19
    Sprache: Englisch
    Anmerkung: CONTENTS I. Introduction II. Instrumentation Recording of data III. Results Global radiation Albedo of snow Diffuse sky radiation Effect of clouds on radiation Atmospheric and terrestrial radiation Effect of low sun angle on measured radiation Global radiation gradient Atmospheric transmission coefficient Heat balance of snow cover Applied use of solar energy References. Appendix
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  • 37
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    Wilmette, Ill. : Snow Ice and Permafrost Research Establishment, Corps of Engineers, U.S. Army
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    Signatur: ZSP-202-21
    In: Research report / Cold Regions Research and Engineering Laboratory, 21
    Beschreibung / Inhaltsverzeichnis: Limited studies of white-outs on the Greenland Ice Cap indicate that five major types of low visibility have been reported as white-out. They are: 1.) Overcast white-out, caused by a continuous cloud cover. 2.) Water-fog white-out, produced by supercooled water droplets in the air. 3.) Ice-fog white-out, produced by ice crystals suspended in the air. 4.) Blowing snow white-out, produced by wind-driven, wind-eroded snow. 5.) Precipitation white-out, produced by falling snow. The first three types are interrelated and appear to be produced by upslope, convective lifting of warm maritime air and the advective transport of the cooled saturated air over the cold snow field. Radiation heat losses from the snow surface may contribute to more rapid formation of the white-out. The fact that there is a shift in the prevailing wind direction prior to the development of a white-out indicates that certain changes in upper air circulation may be associated with white-out formation and duration. There is reason to believe that upper air and surface observations might make it possible to forecast white-outs on the Greenland Ice Cap with some degree of reliability.
    Materialart: Schriftenreihen ausleihbar
    Seiten: iv, 12 Seiten , Illustrationen , 27 cm
    Serie: Research report / Cold Regions Research and Engineering Laboratory 21
    Sprache: Englisch
    Anmerkung: CONTENTS Preface Summary Introduction Results at Site 2 Discussion References
    Standort: AWI Archiv
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