Snow science

Claire McArthur
Special to the Tribune

For 75 years, the Central Sierra Snow Lab has studied the Sierra Nevada snowpack

Longtime (and now retired) CSSL director Randall Osterhuber measures the snowpack at the Donner Pass field site. Photo / Central Sierra Snow Lab

Perched atop Donner Pass, well over 7,000 feet, sits the Central Sierra Snow Lab, a research field station responsible for maintaining the longest running snowpack measurement in the West.

Established in 1946 by the U.S. Weather Bureau and Army Corps of Engineers, snow scientists have been manning the station collecting data on precipitation, snowfall, snow depth and air temperature ever since.

“If you combine that with the snow measurements that have been collected from the Southern Pacific Railroad, the record actually goes back to 1879,” says Dr. Robert Rhew, CSSL station manager and professor at U.C. Berkeley, which has managed the facility since 1996.

Across two acres, the station hosts seven buildings and fields of instrumentation for collecting data on other aspects of snow physics and hydrology, meteorology and climatology, from wind speed and solar radiation to snow temperature and relative humidity.

“Just the amount of precipitation might not give you the full story. Just the amount of snow depth might not give you the full story. You have to measure all of these things together, including things that we haven’t measured before just to get a clear understanding of the complexities of climate change in this region,” explains Rhew. “It’s variable on a year-to-year basis, but having a long term record allows you to see changes over a long period of time.”

Understanding the Sierra Nevada snowpack, its water content (known as the snow water equivalent) and the factors impacting how it melts, such as rain on snow events, is vital for the management of California and Nevada’s water supply budgets, which rely heavily on snowmelt.

The CSSL hosts numerous instruments for measuring all aspects of snow hydrology, meteorology and climatology. Photo / Central Sierra Snow Lab

The study of California’s snowpack started in the early 20th century with Dr. James E. Church, known by many as “the father of snow surveying.” Church, a professor at the University of Nevada, Reno, created the first weather observatory on Mt. Rose’s 10,776-foot summit, and in his research, discovered that snow depth does not equate to the amount of water in the powder. He went on to pioneer methods for measuring the snow depth and its water content.

Today, the study of snow has gotten far more complex — though the snow scientists at the lab continue to trudge out after each storm to take core samples of snow for study just as they would have back in the day. The lab relies on tools like snow pillows, antifreeze-filled bladders designed to automatically measure the weight of the snowfall, along with instrumentation from dozens of government agencies, nonprofits and universities collecting data on all weather events. They are also developing new ways of measuring snow water equivalent that could be used around the world, like a gamma-ray sensor that captures data before the snow hits the ground.

Previous research projects at the lab have studied how snow impurities like black soot and other pollutants change the color and reflectivity of the snow, resulting in more sun absorption and a faster melting time.

“We’re hoping to attract more and more of this research as people get interested in the complexities of the winter hydrology of the Sierras and want to do these experiments at a place where we have the most instrumentation of any snow lab out there,” notes Rhew.

Though the details of snow science may seem abstract to a layman, the research conducted at the CSSL has direct implications on our understanding of water supply management and the impacts of climate change.

In 2019, with the retirement of the director and sole operator of the CSSL, Randall Osterhuber, after over 20 years, followed by budget cuts and the pandemic, the future of the snow lab was uncertain. Luckily, Rhew and the partner organizations who benefit from the station’s research wouldn’t let the legacy of the lab end.

“Now we have a new snow scientist at the field station fixing everything up, continuing the legacy of measurements that are happening there, rebuilding all of those ties with the government agencies, and also taking the snow lab in some new directions,” says Rhew.

“A lot of the value of this facility is that it has such a long term data set. We need that perspective to be able to understand what’s happening to our planet.”



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