Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 2 2008 10.5194/acp-8-171-2008 http://www.atmos-chem-phys.net/8/171/2008/ http://www.atmos-chem-phys.net/8/171/2008/acp-8-171-2008.html http://www.atmos-chem-phys.net/8/171/2008/acp-8-171-2008.pdf 171 208 2008-01-16 Snow physics as relevant to snow photochemistry F. Domine florent@lgge.obs.ujf-grenoble.fr M. Albert T. Huthwelker H.-W. Jacobi A. A. Kokhanovsky M. Lehning G. Picard W. R. Simpson Laboratoire de Glaciologie et Géophysique de l'Environnement, CNRS et Université Joseph Fourier, BP96, 54 rue Molière, 38402 Saint Martin d'Hères cedex, France Army Cold Regions Research and Engineering Lab, 72 Lyme Road, Hanover, NH 03755-1290, USA Paul Scherer Institute, Laboratory for Radiochemistry and Environmental Chemistry, 5232 Villigen, Switzerland Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany Institute of Environmental Physics, Bremen University, O. Hahn Allee 1, 28334 Bremen, Germany WSL, Eidg. Swiss Federal Institute for Snow and Avalanche Research, SLF Davos, Flüelastrasse 11, 7260 Davos Dorf, Switzerland Department of Chemistry and Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775-6160, USA now at: Laboratoire de Glaciologie et Géophysique de l'Environnement, CNRS et Université Joseph Fourier, BP96, 54 rue Molière, 38402 Saint Martin d'Hères cedex, France Snow on the ground is a complex multiphase photochemical reactor that dramatically modifies the chemical composition of the overlying atmosphere. A quantitative description of the emissions of reactive gases by snow requires knowledge of snow physical properties. This overview details our current understanding of how those physical properties relevant to snow photochemistry vary during snow metamorphism. Properties discussed are density, specific surface area, thermal conductivity, permeability, gas diffusivity and optical properties. Inasmuch as possible, equations to parameterize these properties as functions of climatic variables are proposed, based on field measurements, laboratory experiments and theory. The potential of remote sensing methods to obtain information on some snow physical variables such as grain size, liquid water content and snow depth are discussed. The possibilities for and difficulties of building a snow photochemistry model by adapting current snow physics models are explored. Elaborate snow physics models already exist, and including variables of particular interest to snow photochemistry such as light fluxes and specific surface area appears possible. On the other hand, understanding the nature and location of reactive molecules in snow seems to be the greatest difficulty modelers will have to face for lack of experimental data, and progress on this aspect will require the detailed study of natural snow samples. 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