It's a foggy fall morning, and University of Washington researcher Susan Dickerson-Lange pokes her index finger into the damp soil beneath a canopy of second-growth conifers. The tree cover is dense here, and little light seeps in among the understory of the Cedar River Municipal Watershed about 30 miles east of Seattle.
She digs a small hole in the leaf-litter soil, then pushes a thumb-sized device, called an iButton, about an inch beneath the surface. If all goes well, this tiny, battery-powered instrument will collect a temperature reading every hour for 11 months. Researchers hope this tool and a handful of other instruments will help them map winter temperatures throughout the watershed as they track snow accumulation and melt.
This fieldwork piggybacks on a recent finding by Jessica Lundquist, a UW associate professor of civil and environmental engineering, and her lab that shows that tree cover actually causes snow to melt more quickly on the western slopes of the Pacific Northwest's Cascade Mountains and other warm, Mediterranean-type climates around the world. Alternatively, open, clear gaps in the forests tend to keep snow on the ground longer into the spring and summer. Lundquist and her colleagues published their findings online this fall in Water Resources Research.
Common sense says that the shade of a tree will help retain snow, and snow exposed to sunlight in open areas will melt. This typically is the case in regions where winter temperatures are below freezing, such as the Northeast, Midwest and most of central and eastern Canada. But in Mediterranean climates where the average winter temperatures usually are above 30 degrees Fahrenheit a different phenomenon occurs. Snow tends to melt under the tree canopy and stay more intact in open meadows or gaps in a forest.
This happens in part because trees in warmer, maritime forests radiate heat in the form of long-wave radiation to a greater degree tha
|Contact: Michelle Ma|
University of Washington