Collaborative Research: Sublimation of Snow (SOS)

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Snowpack plays a vital role in water resources, especially for regions that get water from the seasonal melt of mountain snowfall. However, melting is not the only way that the snowpack is depleted. Sublimation of snow refers to the process by which snow changes directly to water vapor. The impact of sublimation is not well understood, nor are the specific atmospheric conditions that lead to more or less sublimation. This project will help to address questions related to those topics by deploying a set of advanced instrumentation in Colorado in the 2022-23 winter season. The result of this project will be a dataset that can be used to determine whether numerical models are handling sublimation correctly, and if not, how to improve them. The research team will communicate with relevant stakeholder groups, such as water managers, and develop short videos that explain difficult concepts in clear language accessible to the general public. Students will be directly involved in the field campaign, thereby training the next generation of observational and data analysis scientists.The research team will conduct the Sublimation of Snow (SOS) field campaign in Kettle Ponds, Colorado during the 2022-23 winter season. Snow sublimation plays a significant role in water resources but the physics that govern rates of sublimation are not fully understood. This project will focus on the role of wind in sublimation, both in low-wind conditions where turbulence is crucial, and in higher-wind conditions when blowing snow factors in. The SOS field campaign is embedded within a larger DOE-sponsored campaign called the Surface Atmosphere Integrated Field Laboratory (SAIL) which will provide remote sensing measurements from radars and lidars. SOS will contribute four flux towers (NCAR Integrated Surface Flux Systems, ISFS) for turbulence and latent heat flux measurements, along with a number of other instruments that will provide snow depth, density, and water content, soil and snowpack temperatures, and blowing snow characteristics. Three key science questions will be addressed: What governs the characteristics of the near-surface boundary layer over snow in complex terrain, and how these characteristics evolve through time? Over a winter season, how frequently do different boundary layer regimes occur, how much snow sublimation occurs during each, and how does this affect the total seasonal mass and energy balance? What measurement and analysis strategies are most robust for quantifying snow sublimation in a mountain valley?This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.