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Dynamics of snow metamorphism: observations of physical and chemical processes and microstructural multi-phase numerical simulation

English title Dynamics of snow metamorphism: observations of physical and chemical processes and microstructural multi-phase numerical simulation
Applicant Schneebeli Martin
Number 108219
Funding scheme Project funding (Div. I-III)
Research institution WSL - Institut für Schnee- und Lawinenforschung SLF
Institution of higher education Swiss Federal Institute for Forest, Snow and Landscape Research - WSL
Main discipline Climatology. Atmospherical Chemistry, Aeronomy
Start/End 01.11.2005 - 31.10.2008
Approved amount 284'988.00
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Keywords (10)

snow chemistry; global change; snow; numerical modeling; metamorphism; adaptive finite elements; phase-change; front tracking; climate; atmospheric chemistry

Lay Summary (English)

Lead
Lay summary
Snow metamorphism is driven by temperature gradients and shapeminimization in the snow cover. The energy and mass balance of thesnow-covered landscape, the interpretation of ice cores, and the formationof snow avalanches are known processes which are strongly influenced bysnow metamorphism.Natural snow is an important active player in the chemistry of the Earth’satmosphere. Snow surfaces are connected to the production of halogencontaining species, which catalyze the ozone destruction in the polar andarctic regions. The snowpack is a vigorous chemical reactor. The processesinside the snowpack are driven by both photochemistry and heterogeneousinteraction of the trace gases with ice.Chemical reactions depend on the morphology of the snowpack. Diurnal andseasonal temperature cycles continuously drive the snow metamorphism.Thus, the porous snowpack is highly dynamic and there is a continuousformation of fresh ice surface area inside the porous snow. Little isknown about how heterogeneous chemical processes on a surface areaffected, if the hosting surface is continuously changing its nature. Theimpact of snow metamorphism on chemical processes in snow will beinvestigated.The formation of snow avalanches originates in snow metamorphism. Thecomplex structural changes in the snow due to snow metamorphism modifythermal, mechanical, and physical properties in a way that is poorlyunderstood. Reliable forecast models for snow properties will require amore physically based model than is available now. Properties like thestrength of snow, effective heat conductivity, and albedo, can onlypartially be modeled. This research shall improve the fundamentalunderstanding of the evolution of the snow micro-structure.The objective is to create well-defined experiments of controlled snowmetamorphism, to make simultaneous structural, physical, and chemicalmeasurements with high temporal resolution, and to understand theprocesses by numerical simulation. The complexity of these tasks can onlybe accomplished by joining forces between different institutes, each witha high reputation in its discipline. The project combines time-lapse X-raymicro-tomography of metamorphosing snow samples, chemical uptakeexperiments, and micro-structural numerical simulations of the energy andmass conservation with phase change occuring during metamorphism, combinedwith chemical transport processes, on nature-identical snow. Becausenatural snow is highly variable in its physical and chemical properties,artificial snow grown in the vapor phase will be used, which can bemanufactured under defined conditions and also traced with chemicallyrelevant acids.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
155999 The impact of the physical micro-environment of impurities in snow on their re-distribution during metamorphism, chemical reactivity, and transfer to ice core archives. 01.05.2015 Project funding (Div. I-III)
140400 The uptake of peroxynitric acid on ice surfaces: The role of grain boundaries and of dissociation 01.06.2012 Project funding (Div. I-III)
121857 The uptake of peroxynitric acid on ice surfaces: The role of grain boundaries and of dissociation 01.06.2009 Project funding (Div. I-III)
121779 Microchemistry of HONO in snow under non-equilibrium conditions 01.11.2008 Project funding (Div. I-III)
125179 Structure-chemistry interaction during snow metamorphism 01.05.2009 Project funding (Div. I-III)

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