In early February 2021, the U.S. had its deadliest week for avalanches in more than a century with 15 fatalities. Researchers point to a number of converging factors, from early snowfall followed by drought, to more people skiing in the backcountry because of COVID-19. But underlying all of this is a major problem: Scientists still do not have a sufficient way to figure out how much snow there is in a given area. Although there are satellites that can determine geographically where snow has fallen, they do not yet show how deep the snow is, what the snow characteristics are, nor what the snow water equivalent is (the amount of liquid water in the snow when it melts).
The problem does not just affect avalanche forecasting, though. Seasonal snowpack melt in the mountains is a crucial resource for more than 1 billion people around the world, and in the Western U.S. it provides approximately 70 percent of the water used by humans. This snow water is used for drinking, agriculture and hydropower, and with a changing climate, will only become more important.
Hans-Peter Marshall, a professor at Boise State University, is one of the scientists working on this problem as part of the NASA SnowEx mission. SnowEx is a multiyear project testing different techniques and instrumentation (such as radar, LIDAR and imaging) for mapping snow water equivalent to use in future satellite technology.
“We are trying to develop the best possible approach to getting the snow water equivalent from space,” Marshall said. His team uses a variety of techniques, from ground observation (which often necessitates skiing or snowshoeing into the backcountry) to mounting sensors on drones, airplanes, helicopters and snowmobiles.
In January of 2023, NASA and the Indian Space Research Organization will be launching NISAR, a joint satellite mission to study the Earth’s surface. The SnowEx mission’s terrestrial work will be used to validate the space-based measurements. The different sensors and methods focus on collecting snow properties that, when collected from a satellite, will create a more comprehensive understanding of snow around the world, and subsequently, more accurate snow modeling methods.
Scientists are interested in determining the snow water equivalent, snow structure, depth, temperature, particle size and albedo (the measure of the amount of energy from the sun that is reflected by the Earth’s surface). “
There’s a big feedback system with the snow cover where, as we have less snow cover, the earth is absorbing more energy,” Marshall said. “So knowing when and where the snow is is important from a climate perspective, and we need these tools in place as soon as possible.”
While the information collected by NISAR and future snow and water focused satellites will help avalanche forecasting and monitoring by providing much more snow information than previously available, to accurately model the snow stability will require even more data at a higher spatial and temporal resolution.
Still, researchers at Boise State are working on novel methods to track avalanche movement using infrasound (the study of sound waves below the lower limit of human hearing). Jeffrey Johnson, an infrasound specialist and volcanologist at Boise State, is transferring some of the technology and methodology he has used to track volcano flow movement to the study of avalanches.
“What we’re able to do with our new instrumentation is to more comprehensively monitor these hazardous areas,” Johnson said. “We work with the snow forecasters to monitor activity along hazardous sections of highway and identify when snow avalanches have occurred and assess how big they are.”
Johnson and his team use numerous small microphones placed in the field to record snow (and lava flow) movements, and through triangulation, track and determine how big the activity was and how far it is going.
“You can think of [snow] as the world’s largest natural reservoir which we don’t have a great idea of how much exists there,” Marshall said. “Especially in the face of a changing climate, those patterns are changing. We have increases in population and increases in water needs, and our dams can’t hold all of that water. So as that water gets released earlier in a warming climate, we are going to have to make hard decisions about how much to store in our reservoirs, and how much to let through.”
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