Two things dictate a pending avalanche: Liquid water content in the snow permits slippage, while the height of the powder against the mountain slope creates the pressure for the tumble. For years, scientists have tried to measure these characteristics using infrared scanners or satellites, but these tools work best for large flat areas, such as with melting Arctic sea ice. Expensive laser or ultrasonic sensors on poles can accurately measure snow height, but these fragile devices are easily destroyed or shifted by snow movement on steep slopes. Plus it’s dangerous to jab probes directly into snowpacks in places where loose powder sits ready to plummet. So a team of researchers devised a hands-off way to monitor avalanche-prone peaks on Weissfluhjoch mountain near Davos, Switzerland. Over the course of two consecutive summers (2012 and 2013), they buried a small, upward-facing radar dish and a GPS antenna into the mountain dirt before the winter snows arrived. When the storms hit, they found that the radar could gauge snow height, while interference of the GPS signal provided a readout on liquid water content. Combining the two technologies paralleled the accuracy of laser recordings and other conventional snowpack measurements, the team reports this month in Geophysical Research Letters. The technique also gave daily updates of the melt-freeze cycles in the snow, which could prove useful for predicting possible flash floods.
(Credit for linked PDF: Roger Gut)