Taking in snow requires perspective from space

Snow cover across North America
NASA's SnowEx research project is testing techniques and technologies for measuring snow's water content. One of the technologies used collects images of North American snow cover.
NASA's Goddard Space Flight Center

Mention Minnesota — to anyone, anywhere — and mention of snow is not be far behind.

Snow is the seasonal bedrock of our cultural identity: We snowshoe, snowmobile, ski and sled. We tromp through it, shovel it, brush it off our cars — and complain about it.

But snow serves a vital role beyond our griping: It feeds our crops, keeps the tapwater running, and even gives us clues about distant parts of the universe.

Minnesota's seasonal snows have steadily and predictably replenished our surface and groundwater. But the predictability is changing, as the climate changes. While our warm winters — ahem — are visible reminders of weather's short-term effects, NASA is taking a long view on the state of snow, and how it can help scientists predict the future.

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In a combined approach on the ground, in the air and from orbit, the new five-year NASA SnowEx research campaign has gathered more than 50 scientists working together to quantify how much snow is on the ground at any given time — and how much water is in that snow.

What's so special about snow?

According to NASA, more than a sixth of the world's population relies on water from seasonal snow pack and glaciers. Even those who don't directly rely on those water sources are affected indirectly, through economic forces like agriculture and hydroelectric power.

Usually, snow is a stable "water battery," slowly releasing water as it melts amid rising spring temperatures. The warming climate is setting a trend for weather patterns that change the amount of snow on the ground, when it falls and how it melts.

With those answers come a lot of questions: The climate-based changes include many unknowns that NASA scientists are hoping to answer.

Dalia Kirschbaum, a NASA scientist on the project, said SnowEx research can also offer a local angle on those cosmic questions. What they find could help model how snowpack in northern Minnesota affects spring flooding on the Red River, for instance, and in other places around the world where monitoring is a bit more sparse.

Snow or rain? Why does it matter?

Snow is water. But is it better than rain?

When scientists consider the power of snow, they note its albedo, which is the amount of solar energy reflected back out into space, instead of being absorbed.

Snow has a higher albedo than other precipitation, which means it reflects more solar energy back into space than it absorbs. A high albedo is one of the reasons, for instance, why Venus is so bright in our night sky. The planet's thick, cloud-covered atmosphere reflects most of the solar energy away. The lower the snow cover, the more solar energy is absorbed.

Snow tends to stay put — or, at least, move slowly like a glacier — hitting the pause button on the water cycle. Rain is far more mobile than snow: As soon as it hits the ground, it immediately starts its journey to lakes and rivers and eventually follows those paths to the oceans.

The addition of rain and snow to the water cycle changes its balance — and raises the very questions NASA's SnowEx program is attempting to answer.

"The power of these observations is the ability to look globally and understand that water is finite and we need to know where it's stored and where it's going," Kirschbaum said.

Falling snow or rain releases energy in a specific pattern — thunder and lightning, for instance, are among the most noticeable — but there are many other signature patterns that NASA's sensors can detect and measure. The sensors on orbiting satellites are capable of measuring rain or snowfall, even how much water is coming down, by monitoring those signatures.

Water is water is water

On Earth, on Mars or on distant planets we have yet to discover, water is still water. NASA applies its study of water, snowfall and other precipitation on Earth to the study of the cosmos at large.

Upcoming NASA projects like the James Webb space telescope, which is set to launch next year to search for and study exoplanets, take advantage of what NASA can learn about water on Earth and apply it to our exploration of the space around us.

This study of the cosmos in the hope of finding water on distant worlds might lead new avenues of discovery, perhaps even to a planet not unlike our own.

Seasonal water flows
Seasonal flows on steep Martian slopes, possibly shallow seeps of salty water, the dark streaks on the hillside. This July 21, 2015, image from the orbiter's HiRISE camera shows examples within Mars' Valles Marineris.
NASA| JPL-Caltech | University of Arizona