The Growth of Bonds and the Increase of Mechanical Strength in a Dry Seasonal Snow-Pack

Keeler, Charles M.

doi:10.3189/s0022143000027027

Cited by 18 publications

(18 citation statements)

References 7 publications

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“…Brown and others (1999) assumed db = d /10 for fresh snow, increasing to 0.15–0.30 after 7 days of isothermal metamorphosis. Keeler (1969) found d b ≤ d /20 for snow 2 days old, but reported no data for snow younger than this. We assume a range of 0.1 ≤ db/d 1 ≤ 0.4, with no correction for density or age, and use this to bracket our prediction.…”

Section: Comparison To Threshold Algorithmsmentioning

confidence: 91%

Snow saltation threshold measurements in a drifting-snow wind tunnel

Clifton¹,

Rüedi²,

Lehning³

2006

J. Glaciol.

116

155

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ABSTRACT. Wind tunnel measurements of snowdrift in a turbulent, logarithmic velocity boundary layer have been made in Davos, Switzerland, using natural snow. Regression analysis gives the drift threshold friction velocity (u Ãt ), assuming an exponential drift profile and a simple drift to friction velocity relationship. Measurements over 15 snow covers show that u Ãt is influenced more by snow density and particle size than by ambient temperature and humidity, and varies from 0.27 to 0.69 m s

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Section: Comparison To Threshold Algorithmsmentioning

confidence: 91%

Snow saltation threshold measurements in a drifting-snow wind tunnel

Clifton¹,

Rüedi²,

Lehning³

2006

J. Glaciol.

116

155

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“…At one time, sieving was widely used in snow studies (Bader and others, 1954; Benson, 1962; Keeler, 1969; Fukue, 1977; Granberg. 1985), but it has seen less use recently because it requires disaggregation of the snow sample, breaking snow grains as well as bonds, creating a bias toward smaller sizes.…”

Section: Methodsmentioning

confidence: 99%

Vapor transport, grain growth and depth-hoar development in the subarctic snow

1997

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ABSTRACT. M easurements from the sub arctic snowpack are used to explore the relation ship hctween grain growth and vapor flow, th e fundamental processes of dry-snow m eta m or phi sm. Du e to extreme temperature grad ients, the suba rctic pack undergoes extensive deplh-hoa r m etamorphi sm. By the end of the winter a fi ve-l ayered stru ctu re with a pronounced weak laye r near th e base of the snow evolves. Grain-size increases by a factor of 2-3, wh i le t he number of g ra i ns per unil mass d ecreases by a fac tor of 10. Obse rved growth rates require significant net inter-particle vapor fluxes. Stable-isoto pe ratios show that there are a lso significa nt net layer-to -I aye r vapor flu xes. Soil moi sture enters the base of th e p ack and mixes wit h the bottom 10 cm of snow, while iso topieally light water vapor fractionates from the basal layer a nd is d eposiled up to 50 cm high er in the p ack. End-of-winter density profi les for snow on the gro und, eomf,ared with snow on tabl es, indi cate th e ne t layer-to-laye r vapor flu x averages 6 x 10 kg m -2 S-I, th ough detail ed measurements show the net flu x is episod ic a nd varies with time and height in the pack, with peak net fl uxes ten tim es higher th a n average. A model, driven by observed temperatu re profiles, reproduces th e layer-lo-layer flu x pattern a nd predicts the observed weak layer at the base of the snow. Calcu lated layer-to-Iaye r vapor fluxes a re ten times higher than inter-particle flu xes, which implies that depth-hoar g rain g rowt h is limited by factors other than the vapor supply. This finding suggesls that gain and loss of water molecules due to sublimation from g rains ta kes place at a rate m a ny times hi gher than th e rate at which gr ains grow, a nd it expl ains why g rain s can meta morphose into different form s so r eadily.

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“…This transfer is apparently much more rapid in the natural snow-pack, presumably due to convection. Keeler (1969) presents data from thin sections of natural dry snow showing that xjR increases from 0.02 for snow two days old to 0.25 by day 47 after precipitation. Beyond that, xjR changed little during the remainder of the snow-pack season.…”

Section: The Analysis For Snowmentioning

confidence: 99%

Threshold Wind-Speeds and Elastic Impact in Snow Transport

Schmidt

1980

J. Glaciol.

125

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Cohesive forces are added to the analysis offorces on sand and soil particles to show that fluid drag, alone, often cannot initiate movement of a snow surface. The impact force of saltating ice spheres, however, can easily provide the force to break cohesive bonds, according to these calculations. The argument suggests a balance between the distribution of bond strengths of exposed surface particles and the distribution of saltation trajectory h eights. RESUME. Seuil des vitesse de vent et [,impact ilastique pOllr le transport de la Ileige. Les forces de cohesion s'ajoutent a l'analyse des forces s'exen;:ant sur les particules de sable ou de sol pour montrer que l'entrinement par le fluide, seul, est souvent insuffisant pour provoquer la mise en mouvement d'une surface de neige. Cependant, la force d'impact d'une sph ere de glace en saltation peut aisement briser les liens de la cohesion, selon ces calculs. La conclusion suggere un bilan entre la distribution des resistances des liens entre les particules des surfaces exposees et la distribution des hauteurs de trajectoire de la saltation. ZUSAMMENFASSUNG. Schwellenwerte der Windgeschwindigkeit ulld elastischer Aufprall beim Schneetrallsport. Als Beweis dafur, dass fliessende Verschleppung alIein oft keine Bewegung einer Schneedecke einleiten kann, werden kohasive Krafte in die Analyse der Kraftwirkung auf Sand-und Bodenpartikel eingefuhrt. Die AufpralIkraft springender Schneekugeln genugt jedoch zur Uberwindung kohasiver Bindungen, wie aus diesen Berechnungen hervo rgeht. Infolgedessen lasst sich ein Gleichgewicht zwischen der Verteilung der Bindungskrafte in exponierten Oberflachenteilch en und jener def Hohen der Sprungbahnen annehmen.

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The Growth of Bonds and the Increase of Mechanical Strength in a Dry Seasonal Snow-Pack

Cited by 18 publications

References 7 publications

Snow saltation threshold measurements in a drifting-snow wind tunnel

Snow saltation threshold measurements in a drifting-snow wind tunnel

Vapor transport, grain growth and depth-hoar development in the subarctic snow

Threshold Wind-Speeds and Elastic Impact in Snow Transport

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