Snowpack

Summary

Today the weather forecast is largely based on numerical models. Similarly, the SLF develops models to simulate the surface processes in the mountains. One such model is SNOWPACK, that describes the evolution of the snow cover and its interactions with the environment. SNOWPACK has been primarily designed to support and improve the avalanche warning, but can also be applied to many other fields. SNOWPACK is widely used to answer a large variety of questions related to ecology, climatology, hydrology or winter sports.
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 to bavay@slf.ch.

Snowpack Development

The operational model of the Swiss avalanche warning service is available as an integrated software package.

• 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.

It simulates the evolution of the snow cover based on meteorological input data. International intercomparison studies show that SNOWPACK is successfully applied to alpine, arctic, maritime and continental snow covers.

Fig. 1: SNOWPACK Graintype

What is SNOWPACK?

SNOWPACK solves the mass- and energy balance equations using a Finite Element numerical scheme. It is written in the C programming language. SNOWPACK is delivered with a user-friendly Java interface. The interface is used to drive the model with key input parameters as well as visualise the results. A variety of output and graphical options are available. SNOWPACK is available for windows and all UNIX systems. SNOWPACK parameterises snow microstructure and thus allows a detailed representation of the layered snow structure. The following individual processes are modelled:

• Heat Transfer
• Settling
• Phase Change
• Water Transport
• Metamorphism

The energy- and mass transfer at the surface is modelled by taking into account:

• Precipitation as snow or rain
• Shortwave radiation
• Incoming and outgoing longwave radiation
• Sensible heat flux
• Latent heat flux including surface hoar formation
• Windpumping
• Snow drift

Fig. 2: SNOWPACK Measured and Calculated Snow Temperature

Application of 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 modelled. 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. This is applied to the reconstruction of the formation conditions of ice found in ice cores.

Fig. 3: SNOWPACK Drift Index

Contact

• Michael Lehning