Measuring snow microstructure and hardness using a high resolution penetrometer

Using a high resolution snow penetrometer we are able to measure snow penetration resistance and snow meso- and microstructure. The variation of the signal is characteristic for different snow types. The penetrometer can be used in the field as well in the laboratory. The range of snow types which can be tested extends from light new snow (50 kg m(-3)) to very dense snow occurring on ski race tracks (500 kg m(-3)). The displacement resolution of the penetrometer is better than one mm to detect significant changes in resistance, the force signal is measured every 0.004 mm. The constant penetration velocity can be varied between 6 and 20 mm s(-1). A classification is developed to extract textural information of snow from the force signal. The classification is based on experiments with artificially metamorphosed snow and undisturbed snow from the Alps and Alaska. Two weak layers were identified and compared to surface sections, The new instrument makes the measurement of mechanical and stratigraphic features of a snowpack a more objective and easy task than with other methods. The high displacement resolution promises also a better identification of weak layers. (C) 1999 Elsevier Science B.V. All rights reserved.