Community Snow Obs and Space Lasers!

Through CSO, our team is fortunate to meet and work with all sorts of snow researchers and enthusiasts. We are happy to feature a short blog post from Hannah Besso, currently a graduate student at the University of Washington. Hannah recently published a journal article about measuring snow depths with the ICESat-2 satellite and comparing those snow depths with Community Snow Observations snow depth measurements. Please enjoy.

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Did you know that over half of our water supply in the Western US comes from snow? The snow stores our water for free, melting slowly during the spring and summer when supplies are low from lack of rain. Water managers need to predict how much snowmelt will enter reservoirs so they can decide when to release or store water. Most of our snow falls in the mountains, where it’s difficult to take measurements due to road closures, steep slopes, and avalanches. Making things more challenging, snow can be way deeper in some places than in others. Most estimates of ‘snow water equivalent’ (SWE), or the amount of water held in our snowpack, come from a few weather stations in the mountains. Although these measurements are very accurate for their exact location, there aren’t enough stations to provide the full picture.

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That’s where space lasers – yes, you read that right – could come into play. In 2018, NASA launched a satellite called ICESat-2 that uses a green laser to measure the elevation of the earth’s surface. By subtracting snow-off surface elevations from snow-on elevation measurements made with ICESat-2, we can measure snowpack depth. In some cases, ICESat-2’s space laser can measure elevations with under an inch of vertical error, which is incredible considering the satellite orbits 300 miles above the Earth! Unfortunately, that accuracy becomes worse in steep mountain regions. For a study we completed last year, we compared our ICESat-2 measurements of mountain snowdepth to data from weather stations and snow measurements from Community Snow Observations (CSO). We found measurement errors of only about 5-8 inches in the mountains of Washington and California. This makes us hopeful that ICESat-2 snow measurements can be part of a new era of snowpack estimates: an era that combines cutting-edge satellite technology with more established methods like manual snow depth measurements and snowpack modeling. If so, this could be a step in the right direction towards making sure that Western U.S. farmers, fish, and cities have as much water as possible all year long.