Wednesday November 1, 2023

Physics Today

What do salmon, hydroelectric power, and agriculture have in common? They all depend on snowmelt. So do floods and wildfires. “We are seeing more fires because the snow is melting earlier,” says Ana Barros, an engineering professor at the University of Illinois Urbana-Champaign, recalling how swaths of the US were shrouded in smoke from the record fires in Canada this past summer. Early melt can make soil soggy at the wrong time, and less snowmelt can leave soil dry; both force farmers to change their planting strategies to successfully grow crops.

The chief challenge in understanding and predicting seasonal snowmelt is measuring the snowpack. Snow accumulation varies spatially and temporally. It gets deep in mountains and remains shallower on prairies. Snow is porous, and its density varies with air, ice, and liquid-water content. Substrate, vegetation, sun, dust, soot, wind, snow grain size, and other factors affect how snow settles and melts and how sensors respond to snow.

Snow is a gap in the current understanding of the hydrologic cycle, says Barros. “Scientists don’t have the understanding to really be able to assess and improve computer models.” Hans-Peter Marshall, a snow physicist at Idaho’s Boise State University, says that “we have to move to remote sensing, and monitoring snow will take more than one solution.”

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