Correlating Snow Micro-Structure with Snow Shear Strength (original) (raw)

On the objective analysis of snow microstructure

1987

ABSTRACT It is a long-standing problem to find an appropriate small set of parameters that best describes snow micro structure as observed on sections or thin slices, for the purposes of relating physical properties of snow to its electromagnetic, thermal, or mechanical properties. The stereological parameters point density and intercept length (uniquely related to surface area per unit volume) are likely members of the minimal set of descriptors, but a measure of their distribution, such as the variance, is also needed.

Measured shear rates in large dry and wet snow avalanches

Journal of Glaciology, 2009

We present estimates of internal shear rates of real-scale avalanches that are based on velocity measurements. Optical velocity sensors installed on the instrument pylon at the Swiss Vallée de la Sionne test site are used to measure flow velocities at different flow heights of three large dry and wet snow avalanches. Possible sources of error in the correlation analysis of the time-lagged reflectivity signals measured by optical sensors are identified for real-size avalanches. These include spurious velocities due to noise and elongated peaks. An appropriate choice of the correlation length is essential for obtaining good velocity estimates. Placing restrictions on the maximum possible accelerations in the flow improves the analysis of the measured data. Coherent signals are found only in the dense flowing cores. We observe the evolution of shear rates at different depths between the front and tail of the flowing avalanche. At the front, large shear rates are found throughout the de...