Sensitivity of turbulent fluxes to wind speed over snow surfaces in different climatic settings

• Published in: Advances in water resources 2013-05, Vol.55, p.178-189
• Main Authors: Dadic, Ruzica, Mott, Rebecca, Lehning, Michael, Carenzo, Marco, Anderson, Brian, Mackintosh, Andrew
• Format: Article
• Language: English
• Subjects: Aerodynamics; Computational fluid dynamics; Energy balance; Fluxes; Glacier mass balance; Relative humidity; Snow; Snow and Ice; Stability; Turbulence; Turbulent uxes sensitivity; Wind speed
• ISSN: 0309-1708; 1872-9657
• DOI: 10.1016/j.advwatres.2012.06.010

► Sensitivity of modeled turbulent fluxes to wind speed increases with air temperature and relative humidity. ► Sensitivity is highest when the stability parameter ζ=1 and exponentially decreases either side of that range. ► The peak in sensitivity is caused by the atmospheric stability correction. ► ζ=1 occurs at wind speeds typical for glacierized catchments (3–5ms−1). ► Enhanced turbulent fluxes over areas with high wind speed can lead to an earlier melt onset and to more melt. Local wind speed variations influence the energy and mass fluxes over snow through snow accumulation, sublimation of drifting and blowing snow, or variations in turbulent fluxes over static snow and ice surfaces. We use idealized model experiments to analyze the sensitivity of turbulent fluxes over static snow surfaces to variations in wind speed under different climatic conditions. We find that the sensitivity (change in the turbulent flux per change of unit wind speed) increases with increasing air temperature and relative humidity. The sensitivity of turbulent fluxes to wind speed is highest when the stability parameter ζ=1, which occurs at wind speeds typical for glacierized catchments (3–5ms−1), and exponentially decreases either side of that range. That peak in sensitivity is caused by atmospheric stability corrections in the model, and occurs independently of the flux-profile relationships we tested. Our results quantify the significant effect of local wind speed variations on turbulent fluxes over snow and ice and can be used to estimate potential model uncertainties in different climates, especially for the typical assumption in distributed hydrological models that the wind speed is spatially constant.