Drifting Snow

Overview

Drifting snow significantly influences snow distribution and consequently avalanche hazard, ecology and hydrology in the Alpine region. With the current drifting snow models we are able to predict the spatial snow distribution relatively well on scales of a few meters. To understand and predict finer scales of snow distribution however, the complex drifting snow process must be better understood. This requires measurements of drifting snow mass flux profiles.

The experiment is designed for three specific aims: we want to compare different drifting snow mass flux sensors; measure vertical profiles of drifting snow (as these measurements are rare in complex terrain); and provide observations to which we can validate a Lagrangian drifting snow model we are currently developing.

Weissfluhjoch Versuchsfeld: The drift stations are located on the right-hand side of the image.

Experimental Setup

We measure drifting snow mass fluxes at a gentle ridge slightly downwind of the Weissfluhjoch Versuchsfeld. The experiment consists of three masts equipped with different sensors.

• Mast 1: 4 cup-anemometers, 4 Wenglor particle counters (photoelectric particle counters) and 3 temperature/humidity sensors, spread over a 2 m-vertical profile.
  
• Mast 2: 2 FlowCapts (acoustic impact sensors), both covering a 1 meter vertical section
• Mast 3: On the this mast we occasionally attach 4 Mellor traps (mechanical traps), distributed over 2 m height. These traps require close observation of the drifting snow and surface conditions and are only exposed during specific events. We focus on events with both strong winds and precipitation and on pure drifting snow events. 

The heights of the sensors on all masts is adjusted according to the snow surface height, but vary with the aim of the particular measurement (e.g. whether we want to measure saltation or precipitation). 

Mast 1 is instrumented with 4 anemometers, 4 particle counters and 3 temperature/humidity sensors (only 2 shown).

Contact

• C. Groot-Zwaaftink
  
• K. Leonard
  
• D. Lussi
  
• R. Meister