Application of capacitance instrumentation to the measurement of density and velocity of flowing snow

We describe capacitance instrumentation suitable for the measurement of density and velocity of flowing snow with moderate liquid-phase water content. A wand, consisting of two adjacent sensors protected by guard circuits, produces signals that are related to snow density through calibration. Cross-correlation of the signals permits velocity measurements. Calibration is accomplished using a capacitance device that records the dielectric properties of a snow sample while subjecting it to controlled levels of compaction and volume change. Non-invasive probe geometries are also presented. The instrumentation is tested in artificial and natural avalanches.