It’s said on sticky summer days: “It’s not the heat, it’s the humidity.” That holds true in the winter too, and could hold the key to the future of snowpack and water resources in the American West.
In a new study published today in Proceedings of the National Academy of Sciences, University of Utah professor Paul Brooks and University of Nevada Reno professor Adrian Harpold show that changes in humidity may determine how the contribution of snowpack to streams, lakes and groundwater changes as the climate warms. Surprisingly, cloudy, gray and humid winter days can actually cause the snowpack to warm faster, increasing the likelihood of melt during winter months when the snowpack should be growing, the authors report. In contrast, under clear skies and low humidity the snow can become colder than the air, preserving the snowpack until spring.
Climate change, they say, can tweak winter humidity up in some regions and down in others.
“It means that trends and patterns in humidity will be very important to the future of snow,” Harpold says.
Brooks says that researchers have known that a changing climate could have major impacts on snowmelt-derived water resources. “But it has been unclear up to this point,” he says, “why some areas seem to be much more sensitive to change while other locations seem resilient.”
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