Cryospheric and Polar Processes Seminar

Blew swayed spruce: what can trees blowing in the wind tell us about how much snow is in the canopy?​ by Dr. Mark Raleigh, Research Scientist at NSIDC

Abstract:  Forest canopies influence the accumulation and persistence of snowpack on the ground, with the net effect depending on climate and forest characteristics. New snowfall intercepted in forest canopies may sublimate or melt, thereby reducing snow accumulation on the ground and altering the timing of water availability. Quantifying snow storage in forests has been an outstanding challenge in observations and model verification, with implications for management of forested watersheds. Recent progress has been demonstrated in quantifying rainfall interception with wind-induced tree sway data. Consistent with mechanical theory, the sway frequency of a tree drops as water mass is added to the canopy. However, the relevance of this approach to snowfall interception has received less attention.

In this CPP talk, I will highlight my ongoing experimental work using tree sway data to quantify snowfall interception in coniferous forests. Tree sway can be quantified using low-cost accelerometers. From these acceleration data, tree sway time series are derived from a windowed frequency analysis using Lomb-Scargle periodograms. I will first demonstrate the concept at the Niwot Ridge subalpine forest where I have been monitoring tree sway and snow interception since 2014. I will then compare results from Niwot to other locations in Colorado, including trees that I instrumented as part of the 2016-2017 NASA SnowEx campaign. Finally, I will discuss ideas and pathways for scaling up the methodology to quantify canopy snow storage at the forest stand scale.

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