Sublimation of Snow (SOS) Project

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.

Project Overview

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:

  1. What controls the mixing of air near the snow surface with air higher up in the atmosphere in cold and often windy mountain environments?
  2. How do these environmental conditions change the amount of snow that is lost directly to the atmosphere?  
  3. What is the best way to measure this? 
The SOS Project field research is captured in this AGCI-produced video, Vanishing Snow: The Hunt for the Missing Water, shot at the Rocky Mountain Biological Laboratory field study site and featuring interviews with the research team.

A Unique Partnership of Scientists, Funders, and Acronyms

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.

Sublimation of Snow Project principal investigator Jessica Lundquist (University of Washington) and co-principal investigator Julie Vano (AGCI) install a snow pillow, while members of the National Center for Atmospheric Research team install instrumentation on a 20 meter/70 ft tower at the Rocky Mountain Biological Laboratory in Gothic, Colorado. Photo: Emilio Mateo/AGCI

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. 

A time lapse video comprising daily snapshots of the Sublimation of Snow study site from October 2022 to June 2023 reveals snow patterns across the entire winter season.

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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SOS Instrument Library

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.

Sublimation of Snow Project Team

Jessica Lundquist

University of Washington

Julie Vano

Aspen Global Change Institute (AGCI)
Research Director

Ethan Gutmann

National Center for Atmospheric Research (NCAR)

Daniel Hogan

University of Washington
Graduate Student

Eli Schwat

University of Washington
Graduate Student

Michael Haugeneder

WSL Institute for Snow and Avalanche Research SLF
Graduate Student

Elise Osenga

Aspen Global Change Institute (AGCI)
Community Science Manager

Liz Carver

Aspen Global Change Institute (AGCI)
Communications Manager

Emilio Mateo

Aspen Global Change Institute (AGCI)
Climate Science Fellow

Steven Oncley

National Center for Atmospheric Research (NCAR)
Scientist III

Chris Roden

National Center for Atmospheric Research (NCAR)
Engineer, NCAR EOL

Will Nicewonger

National Center for Atmospheric Research (NCAR)
Flux Tower Technician, NCAR EOL

Antonio Vigil

National Center for Atmospheric Research (NCAR)
RF Technician, NCAR EOL

Tony Wiese

National Center for Atmospheric Research (NCAR)
Electrical Mechanical Technician, NCAR EOL


National Center for Atmospheric Research
Lawrence Berkeley National Laboratory, Department of Energy
Physical Sciences Laboratory, NOAA
WSL Institute for Snow and Avalanche Research SLF
Laboratory of Cryospheric Sciences, EPFL
National Center for Atmospheric Research
Rocky Mountain Biological Laboratory


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.