International Snow Science Workshop 2016, a merging of theory and practice

12 ottobre 2016

Proponiamo qui una selezione di lavori del ISSW16, il più importante convegno, a cadenza biennale, sulla neve e le valanghe, tenutosi a Breckenridge, Colorado, dal 3 al 7 ottobre 2016.

ISSW16

Nella settimana dal 3 al 7 ottobre 2016 si è svolto negli States a Breckenridge, Colorado, l'International Snow Science Workshop 2016 - a merging of theory and practice, il convegno biennale che dal 1976 riunisce professionisti e scienziati, provenienti da tutto il mondo, impegnati nel campo della neve e delle valanghe. Il convegno si presenta da sempre come luogo di incontro tra "teorici" e "pratici" del settore, con lo scopo di promuovere lo scambio di idee, di progetti di ricerca e di introdurre e condividere i più recenti strumenti nell'ambito della previsione delle valanghe e dei prodotti invernali.

Vasta la gamma di argomenti che spaziano dalle proprietà della neve alla stabilità del manto nevoso e alla dinamica delle valanghe, dalle opere di protezione e dalle azioni di prevenzione e sensibilizzazione ai rischi alla gestione delle situazioni di criticità, alle operazioni di soccorso ed alla gestione della problematica valanghiva nei comprensori sciistici. Diversi contributi dell'esperienza valdostana (2 poster ed 1 presentazione orale) sono stati presentati da Fondazione Montagna sicura, nella persona del Coordinatore dell'Ufficio neve e valanghe Paola Dellavedova.

Scelti in diretta durante il convegno, vi proponiamo alcuni lavori, uno per giorno di convegno, che ci sono sembrati interessanti: per chi voglia cimentarsi con un poco di inglese scientifico, di seguito trovate l'abstract o una frase significativa riassuntiva di ciascun lavoro e in allegato i pdf dei relativi articoli estratti dagli Atti del Convegno.

1)      AVALANCHE RELEASE 101

Jürg Schweizer, Benjamin Reuter, Alec van Herwijnen, Johan Gaume

Avalanche release can conceptually be described as a sequence of fracture processes including (i) failure initiation in a weak layer underlying a cohe- sive snow slab, (ii) the onset of crack propagation, (iii) dynamic crack propagation through the weak layer across the slope, and (iv) tensile failure through the slab – equivalent to crack arrest, fol- lowed by sliding of the slab.

This conceptual model applies for natural release as well as artificial triggering. The main difference is that failure initiation in the case of natural re- lease follows from a slow damage process where-as in artificial triggering the rapid localized loading causes the initial crack. Nevertheless, in both cas- es, failure initiation is more likely to occur where the snow cover is locally weaker than average. However, for artificial triggering these weak spots are not areas where the damage process is con- currently going on – but typically areas where the weak layer has lower strength or the slab is thin- ner. Thus, spatial variability provides nucleation points for failure initiation, but changes in snow properties may also prevent initiation, and in partcular crack propagation. 

2)      THE EFFECT OF INCREASING LOAD ON WEAK LAYER FRACTURE

Karl W. Birkeland,* and Alec van Herwijnen

Our results demonstrate that adding load dramatically decreases PST cut lengths and increases crack propagation speeds, helping to explain why avalanche triggering is greatly facilitated by loading. 

3)      MANAGING THE PHYSICAL RISK FROM AVALANCHES IN A HELICOPTER SKIING OPERATION - MERGING AND CONTRASTING TERRAIN USE DATA WITH THE OPERATIONAL GUIDING PERSPECTIVE

Pascal Haegeli and Roger Atkins

Interessante per i professionisti della montagna come le guide alpine, in particolare per chi si occupa di heliski!

4)      SUPPORTING, EVALUATING, AND PLANNING AVALANCHE CONTROL EFFORTS WITH LIDAR-DERIVED SNOW DEPTH MAPS

Jeffrey S. Deems, Ryan Evanczyk, Dominic Vellone, Ethan Greene, Tyler Weldon,

David C. Finnegan, Peter J. Gadomski, Adam LeWinter

Per la sezione strumentazione: the TLS snow depth maps enable more efficient route planning with the multiple objectives of effective start zone targeting and efficient route progression, likely reducing time spent on control routes. 

5)      AVALANCHE RISK IN WINTER BACKCOUNTRY TOURING: STATUS AND RECENT TRENDS IN SWITZERLAND

Kurt Winkler, Adrian Fischer and Frank Techel

We calculated the statistical risk to die in an ava- lanche while backcountry touring. Not considering exposure time, the risk of an active backcountry user to die in an avalanche was about 4.4 x 10-5 per year, and thus very similar to the risk to die in a traffic accident during a year.

6)      INVESTIGATING THE THERMOPHYSICAL PROPERTIES OF THE ICE-SNOW INTERFACE PART II: THERMAL CONTACT RESISTANCE

Kevin Hammonds and Ian Baker

It was found that thermal contact resistance was the primary contributor to the en- hancement of the temperature gradient both above and below the ice lens. This was some- what of a surprising result, as latent heat release was originally expected to be a larger contributor to the observed temperature gradient. 

If considering our laboratory specimen as analo- gous to a natural snowpack, our findings would indicate that the porosity of the snowpack just near the ice-snow interface would be of primary im- portance to kinetic snow metamorphism and sub- sequent weak layer development in this region based on enhancements in the local temperature gradient. For field practitioners, these results sug- gest that although obtaining a measurement of the thermal contact resistance would be difficult, ob- taining porosity measurements as an inverse ana- log to thermal contact resistance could be useful and attainable via hand-hardness or density measurements. We point out, however, that in our experiments we have only studied the effects of coarsened snow grains and lenses of artificially created polycrystalline ice. 

[Contributo di E. Ceaglio - Fondazione Montagna sicura @Ufficio neve e valanghe RAVDA]

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