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Lecture

Spatial Variability of Snow Properties

In course

ENV-525: Physics and hydrology of snow

This course covers principles of snow physics, snow hydrology, snow-atmosphere interaction, and snow modeling. It transmits detailed understanding of physical processes within the snow and at its interfaces with the atmosphere and the ground, and presents ...

Description

This lecture explores the spatial variability of snow properties, including snow water equivalent, density, and depth, and discusses the motivation behind studying snow heterogeneity, the physical processes creating it, and the measurement techniques used to capture it. Real-world examples from Davos and Calgary are presented, highlighting the impact of heterogeneous snow cover on melt timing and volume. The lecture also covers the external drivers and scales influencing snow variability, as well as the processes at the snow-atmosphere interface. Various methods of quantifying snow, such as remote sensing and point measurements, are discussed, along with the challenges in capturing spatio-temporal variability in snow properties.

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Instructors (3)

Wolf Hendrik Huwald

Dr. Hendrik Huwald is a scientist at the Laboratory of Cryospheric Sciences (CRYOS) and a lecturer at the Environmental Sciences and Engineering Section (SSIE) of the Swiss Federal Institute of Technology in Lausanne (EPFL). He completed his PhD in 2003 at the Swiss Federal Institute of Technology in Zürich (ETHZ), developing a numerical model for sea ice and studying energy transfer processes in the Arctic. Between 2005 and 2012 he was a post-doctoral fellow and scientist at the Laboratory of Environmental Fluid Mechanics and Hydrology (EFLUM) of EPFL working on Alpine snow-atmosphere interaction, and energy balance-related research mainly in mountain regions. During this time, he designed, led and participated in numerous large field experiments in different environments. In 2013 he joined the newly founded CRYOS laboratory where he conducted research in the domains of snow science, hydrology, boundary layer meteorology and environmental sensing. He has extensive experience with project management both on national and international level.

Johan Alexandre Philippe Gaume

I started my scientific career in 2008 at the Grenoble University in the IRSTEA laboratory where I did my master's thesis on the rheology of dense granular materials using the discrete element method. In the same lab, I followed with a PhD on the numerical modeling of the release depth of extreme avalanches using a combined mechanical-statistical approach and spatial extreme statistics. In 2013 I obtained a postdoc position at the WSL Institute for Snow and Avalanche Research SLF in Davos where I was in charge of developing and applying numerical models to improve the evaluation of avalanche release conditions and thus avalanche forecasting. While my PhD was mostly theoretical and numerical, my postdoc in Davos allowed me to gain a practical expertise by participating in laboratory and field experiments which helped to validate the models I develop. In 2016, I was awarded a SNF grant to work as a research and teaching associate in CRYOS at EPFL on the multiscale modeling of snow and avalanche processes. I developed discrete approaches to model snow micro-structure deformation and failure in order to evaluate constitutive snow models to be used at a larger scale in continuum models. I also developed numerical models for wind-driven snow transport. In 2017, I was a Visiting Scholar at UCLA to work on a Material Point Method (MPM) to simulate both the initiation and propagation of snow avalanches in a unified manner. The UCLA MPM model was initially developed for the Disney movie "Frozen" and has been modified and enriched based on Critical State Soil Mechanics to model the release and flow of slab avalanches. The results of this collaboration have been published in Nature Communications. In 2018, I was awarded the SNF Eccellenza Professorial Fellowship and became professor at EPFL and head of SLAB, the Snow and Avalanche Simulation Laboratory. At SLAB, we study micro-mechanical failure and fracture propagation of porous brittle solids, with applications in snow slab avalanche release. We also simulate avalanche dynamics and flow regime transitions over complex 3D terrain through the development of new models (depth-resolved and depth-averaged) based on MPM.In 2020, I obtained a SPARK grant to develop a new approach to simulate and better understand complex process chains in gravitational mass movements, including permafrost instabilities, rock, snow and ice avalanches and transitions to debris flows.

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Related concepts (12)

Snow

Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout its life cycle, starting when, under suitable conditions, the ice crystals form in the atmosphere, increase to millimeter size, precipitate and accumulate on surfaces, then metamorphose in place, and ultimately melt, slide or sublimate away.

Remote sensing

Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Earth and other planets. Remote sensing is used in numerous fields, including geophysics, geography, land surveying and most Earth science disciplines (e.g. exploration geophysics, hydrology, ecology, meteorology, oceanography, glaciology, geology); it also has military, intelligence, commercial, economic, planning, and humanitarian applications, among others.

Water vapor

Water vapor, water vapour or aqueous vapor is the gaseous phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Water vapor is transparent, like most constituents of the atmosphere. Under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is less dense than most of the other constituents of air and triggers convection currents that can lead to clouds and fog.

Graupel

Graupel (ˈɡraʊpəl; ˈɡʁaʊpl̩), also called soft hail, hominy snow, or snow pellets, is precipitation that forms when supercooled water droplets in air are collected and freeze on falling snowflakes, forming balls of crisp, opaque rime. Graupel is distinct from hail and ice pellets in both formation and appearance. However, both hail and graupel are common in thunderstorms with cumulonimbus clouds, though graupel also falls in winter storms, and at higher elevations as well. The METAR code for graupel is GS.

Snowmelt

In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many parts of the world, in some cases contributing high fractions of the annual runoff in a watershed. Predicting snowmelt runoff from a drainage basin may be a part of designing water control projects. Rapid snowmelt can cause flooding.

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