In 2021, water users in the Colorado River Basin experienced an unexpected mismatch between winter snowpack and the resulting spring and summer runoff. By some accounts, snowpack across the headwater basins reached around 80% of average, but snowmelt translated into Colorado River streamflows that were only about 30% of average (not the expected 80%). Where did the water go? Understanding the dynamics of snow sublimation will be an important component in answering this complex question. Snow sublimation occurs when snowpack is lost to the atmosphere, turning directly into water vapor without melting first, bypassing the liquid water phase entirely. Snow sublimation may remove as little as 10% or as much as 90% of snowpack from the ground. However, much about the process is not well understood, and sublimation is one of the largest sources of uncertainty in hydrologic modeling.
The Sublimation of Snow Project (SOS), led by Dr. Jessica Lundquist at the University of Washington and supported by the National Science Foundation, will measure multiple processes related to sublimation. The project goal is to improve and communicate fundamental scientific understanding of when, where, and how much snow leaves the land surface to become water vapor.
The study aims to understand:
The East River Watershed, home to Colorado’s Rocky Mountain Biological Lab (RMBL, pronounced “rumble”) was selected as the SOS project site as the area allows for partnership with other concurrent hydrologic studies, including the Surface Atmosphere Integrated Field Laboratory (SAIL), supported by the US Department of Energy, and the Study of Precipitation, the Lower Atmosphere and Surface for Hydrometeorology (SPLASH), supported by NOAA. The SOS project deployed the Earth Observing Laboratory’s (EOL) Integrated Surface Flux System (ISFS) to measure near-ground atmospheric turbulence, energy exchanges, and snow mass.
The collection of field data and the concurrent discovery process is being documented and used to generate written materials, a course website, videos, frequently asked questions, and other outreach products to facilitate discussions with resource managers, educate students in the sciences, and enrich cross-discipline dialogue.
By collecting targeted measurements of blowing snow conditions, this project will also provide new insights into which processes are most important for understanding snow sublimation and help support research on hydrologic systems needed to model and prepare for future droughts.
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The SOS Project deployed over 100 instruments and 16 instrument types, pictured below. Together, these instruments collected approximately 10 million individual data points per hour, providing extremely high temporal resolution data at the Kettle Ponds study site in Gothic, Colorado, to better understand the phase transition from snow to water vapor.
Click on a square below to learn more about each instrument.
Funding for this work was provided by by the National Science Foundation (NSF) Division of Atmospheric and Geospace Sciences (PD 98-1522), award numbers 2139836 and 2139809.
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