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Publications

  • Bartelt, P. and M. Lehning (2002). A physical SNOWPACK model for Avalanche Warning Services. Part I: numerical model. Link
  • Lehning M., P.B. Bartelt, R.L. Brown, C. Fierz, P. Satyawali (2002). A physical SNOWPACK model for the Swiss Avalanche Warning Services. Part II: Snow Microstructure. Link
  • Lehning, M, Bartelt, P.B., Brown, R.L., Fierz, C., Satyawali, P., (2002). A physical SNOWPACK model for the Swiss Avalanche Warning Services. Part III: Meteorological Boundary Conditions, Thin Layer Formation and Evaluation. Link
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SNOWPACK

  • Do you want to know how the snow cover develops in the course of the winter?
  • Are you interested in the mass- and energy interaction in the atmosphere - snow - soil system?

Then you should take a look at SNOWPACK.

SNOWPACK is developed primarily for the purpose of avalanche warning. It's strength is the description of the snow cover layering and snow microstructure. Crucial weak layers and interfaces such as surface hoar, depth hoar or ice lenses are modeled. Because of its accurate mass- and energy balance, SNOWPACK is also increasingly used for climatological research. A new feature is the possibility to also model layers of soil or rock (to a variable depth). This is used for permafrost simulations. SNOWPACK has also a detailed description of the interaction with the atmospheric boundary layer. It deals with complex processes such as wind pumping and snow drift. Special attention is also given to including shortwave radiation penetration of the snow. Therefore, SNOWPACK is suitable for a detailed analysis of the energy- and mass fluxes between the atmospheric boundary layer and the cryosphere.

Use cases

SNOWPACK is widely used for research purposes all around the world in more than 35 institutions by more than 200 researchers. The model has been successfully applied to the Alps, Scandinavia, Northern America, Japan, Russia, China, India, Chile, even Antarctica. It has lead (together with Alpine3D, its spatially distributed derivative) to more than 60 ISI publications. It has been used for hydrological studies, climate change impact studies, snow stability questions, road weather applications, permafrost research, snow farming...

Physical processes

SNOWPACK    
Principal physical processes included in the SNOWPACK model    

A graphical review of the physical processes described by the SNOWPACK model is given in the above figure. SNOWPACK is based on a Lagrangian finite element implementation and solves the instationary heat transfer and settlement equations. Phase changes and transport of water vapor and liquid water are included. Special attention is paid to the metamorphism of snow and its connection to mechanical properties such as thermal conductivity and viscosity. At present, SNOWPACK is the most advanced snow cover models worldwide in terms of microstructural detail. Therefore, first attempts are being made to estimate snow cover stability from SNOWPACK simulations.

Structure of the physical modeling

Model Foundations
SNOWPACK    
The SNOWPACK soil/snow/canopy column
   

The SNOWPACK model is built around a 1D soil/snow/canopy column (see figure above). This in effect neglects lateral transfers and only considers vertical gradients and transfers. The snow is modeled as a three phase porous medium (ice/liquid water/water vapor) but can also contain an arbitrary amount of soil in order to simulate from purely soil layers to snow layers, including ice lenses, permafrost, ponding, etc. An arbitrary number of layers can be simulated, according to needs. Because of its lagragian grid, SNOWPACK can simulate very thin layers if needed (ice crust, hoar).

Operational usage experience

SNOWPACK runs operationally on a network of high Alpine automatic weather and snow measurement stations. Presently approximately 160 sites are in operation. These stations measure wind, air temperature, relative humidity, snow depth, surface temperature, ground (soil) temperature, reflected short wave radiation and three temperatures within the snowpack. The measurements are hourly transferred to the SLF and drive the model. SNOWPACK produces supplementary information regarding the state of the snowpack at the sites of the automatic stations. The model is connected to a relational data base which stores the measurements as well as the model results. Validations of SNOWPACK suggest that the calculations are reliable in terms of the mass balance and the energy budget. The implemented snow metamorphism formulations yield reasonable grain types and are able to reproduce important processes such as the formation of depth or surface hoar.

Other uses

In addition to the stand-alone applications, SNOWPACK is increasingly used in a distributed way. SNOWPACK has been coupled with atmospheric flow and snow drift modules as well as with spatial energy balance models. The coupled models are used to investigate snow deposition and snow cover development in steep terrain and to forecast ski run conditions for racing (however, the current version of SN_GUI does not include the visualization of distributed SNOWPACK calculations).

How to get SNOWPACK

The operational model of the Swiss avalanche warning service is available as an integrated software package. SNOWPACK is now open source and available under LGPL version 3 or above, see www.gnu.org. In order to ease its integration into other models, it is now structured as a library (libsnowpack) and an application that uses the library to perform simulations (snowpack) and can be found at https://models.slf.ch, after registering and requesting access.