Many Western communities rely on snow from mountain forests as a source of drinking water – but for scientists and water managers, accurately measuring mountain snowpack has long been problematic. Satellite imagery is useful for calculating snow cover across open meadows, but less effective in forested areas, where the tree canopy often obscures the view of conditions below. Now, a new technique for measuring snow cover using a laser-based technology called aerial lidar offers a solution, essentially allowing researchers to use lasers to “see through the trees” and accurately measure the snow that lies beneath the forest canopy.
From Desert Research Institute
In a new study published in Remote Sensing of the Environment, an interdisciplinary team of researchers from Desert Research Institute (DRI), the University of Nevada, Reno (UNR), the California Institute of Technology’s Jet Propulsion Laboratory, and California State University described the first successful use of lidar to measure snow cover under forested canopy in the Sierra Nevada.
“Lidar data is gathered by laser pulses shot from a plane, some of which are able to pass light through the tree canopy right down to the snow surface and create a highly accurate three-dimensional map of the terrain underneath,” explained lead author Tihomir Kostadinov, Ph.D., of California State University San Marcos, who completed the research while working as a postdoctoral researcher at DRI. “Passive optical satellite imaging techniques, which are essentially photographs taken from space, don’t allow you to see through the trees like this. We are only starting to take full advantage of all the information in lidar.”
In this study, researchers worked with NASA’s Airborne Snow Observatory to collect lidar data in the Sagehen Creek watershed of the Sierra Nevada by aircraft on three dates during the spring of 2016 when snow was present.
Analysis of the datasets revealed that the lidar was, in fact, capable of detecting snow presence or absence both under canopy and in open areas, so long as areas with low branches were removed from the analysis. On-the-ground measurements used distributed temperature sensing with fiber optic cables laid out on the forest floor to verify these findings.
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