UW atmospheric scientist participating in field campaign to improve Western snowfall, drought forecasts

University of Washington atmospheric scientist Lynn McMurdie has led campaigns to measure rain and snowfall in places ranging from Washington’s Olympic Peninsula to Argentina to the Eastern U.S. Now she’s among the leaders of a field campaign in Colorado to better understand and forecast snowfall in the mountains of the Western U.S. A scientific expedition this coming winter in Colorado’s Yampa Valley will improve forecasts of snowfall and estimates of how climate change will impact snowpack and water availability in mountainous regions of the West.

McMurdie , a research professor of atmospheric sciences at the UW, is one of the principal investigators on the effort, funded with a $4.8 million grant from the National Science Foundation and led by the University of Michigan. Other participating institutions include the University of Wisconsin, the University of Utah, Colorado State University and Stony Brook University.

The Snow Sensitivity to Clouds in a Mountain Environment experiment, or S2noCliME, will use several radars and snow-sampling instruments to measure the size and shape of snowflakes and aerosol particles. The resulting data will help estimate water availability in the Yampa Valley in northwest Colorado. This area on the northwest side of the Rocky Mountains feeds the Yampa River, the largest free-flowing tributary of the Colorado River. Like Western Washington, it relies on melting snow for its summer water supplies, and faces drought and wildfire risk when these snow reservoirs are lower than normal.

"We hope that our data will ultimately improve winter storm forecasts and tell Western cities when to expect a drought because of insufficient snowpack," said lead investigator  Claire Pettersen , an assistant professor at the University of Michigan.

The team will deploy instruments in the Steamboat Springs region of Colorado’s Park Range, a section of the Rockies that extends from southern Wyoming to northwestern Colorado and is poorly covered by the National Weather Service radar network.

Today’s models of snowfall often struggle in these types of mountainous areas.

"In the West, our forecasting models and satellite estimates of precipitation really underpredict snowfall and often don’t get the distribution right," McMurdie said. "The western U.S. depends on snowpack accumulated during the winter for summer water supply for agriculture, fisheries and municipal water sources. Accurate snowfall prediction and understanding the underlying processes producing mountain snow are critical in order to provide guidance on water availability."

Collecting data over an entire winter will provide the statistical power necessary to more accurately predict snowpack after winter storms and over longer timescales. Data will also be shared directly with the Yampa Basin Rendezvous , a working group that brings together scientists and local water managers.

By combining snow-sampling instruments with radars that indirectly study snow, the researchers will overcome a major challenge of using radar: It’s hard to connect the reflected radar signal with the size, shape and number of snowflakes, which determines the amount of water in the snow.

The team’s radars at Storm Peak Lab will use multiple frequencies for detecting snowflakes of different sizes. At the same time, the team will deploy a portable Polarimetric Radar in Hayden, Colorado. This radar’s view toward Mt. Werner and the surrounding 62 miles will be combined with the National Weather Service’s radars to see how the strength of the storms change as they move from the west toward the Rockies.

The results will be compared with those from earlier projects in the Pacific Northwest, such as the UW-led OLYMPEX In a separate project, UW scientists have been investigating the fate of Colorado’s snowpack. A recent paper showed that sublimation, or transformation into a gas, removes less snow in central Colorado than previously suspected.

"We expect to have some similarities, such as how upstream conditions affect the snow-producing cloud processes during this campaign, as well as some differences since the Colorado region is much drier and more interior than the Olympic Mountains or the Cascades," McMurdie said.

Angela Rowe , an affiliate UW faculty member and former UW postdoctoral researcher who is now a faculty member at the University of Wisconsin-Madison is another of the project’s lead investigators. Peter Blossey , research associate professor of atmospheric sciences at the UW, a UW postdoctoral researcher and one or more UW graduate students will also participate in the campaign.

The first instruments will arrive at Mt. Werner this summer, and the team will begin collecting measurements in December.

For more information, contact McMurdie at lynnm@uw.edu. This article was adapted from a University of Michigan.

Tag(s): College of the Environment o Department of Atmospheric Sciences o Lynn McMurdie o weather