Measurement, analysis and modeling of physical processes in dry snow

• Main Author: Carmagnola, Carlo Maria
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS), Université de Grenoble, Florent Dominé, Samuel Morin
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2014
• Subjects: Snowpack; Metamorphism; Snow microstructure; Specific surface area; Manteau neigeux; Métamorphisme; Microstructure de la neige; Surface spécifique; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Greenland
• Online Access: https://tel.archives-ouvertes.fr/tel-01070005; https://tel.archives-ouvertes.fr/tel-01070005/document; https://tel.archives-ouvertes.fr/tel-01070005/file/38791_CARMAGNOLA_2013_archivage_1_.pdf

Snow is a porous medium whose microstructure is constantly subjected to morphological transformations. These transformations, which take the name of ``metamorphism", are likely to affect the thermal, mechanical and electromagnetic properties of snow at the macroscopic level. Specifically, the exchange of energy and matter within the snowpack and between the snow and the atmosphere above are strongly impacted by the evolution over time of the snow microstructure. Therefore, an adequate representation of metamorphism in snowpack models is crucial. The microstructure of a porous medium can be reasonably described using a reduced number of variables. Indeed, the density, the specific surface area (SSA) and the curvature distribution are able to characterize the microstructure of such a material. However, in the case of snow this approach is still in its infancy and has not yet been systematically applied. Semi-empirical variables, difficult to measure and not directly linked to other relevant physical properties, are still widely used in so-called detailed snowpack models. This work contributes to the attempt to represent the state of the snow using well-defined and easily measurable microstructural variables. Among these variables, we focused particularly on the SSA, which is a key quantity for the study of snow and its temporal evolution. Different evolution laws of SSA were studied, starting from empirical relationships based on experimental data adjustments to physical models that represent the flow of water vapor between snow grains. These laws were initially tested using a simplified snowpack model and then introduced directly into the SURFEX/ISBA-Crocus snowpack model. To this end, the SSA in Crocus was turned into a prognostic variable, replacing other preexisting semi-empirical variables. The different formulations of the temporal evolution of the SSA were compared with field measurements, acquired during two campaigns at Summit (Greenland) and the Col de Porte (France). These measurements were carried out ...