A practical formulation of snow surface diffusion by wind for watershed-scale applications

Prediction of snow drift is of importance for structure design and traffic management on snowy and windy prairie landscapes. The snow redistribution by wind is also regarded as one of the largest sources of error in hydrologic snowmelt models. In this study, a snow movement equation was generalized and customized for horizontal two‐dimensional watershed‐scale applications by incorporating snow transport, wind snow diffusion, and snow gravitational movement. Then, the snow surface diffusion process by wind turbulence was formulated in terms of the autocorrelation functions of the measurable wind velocity field using G.I. Taylor's theorem. However, analysis of the example wind data suggested a delta correlation in wind turbulent component that resulted from subtracting their moving average values from the original wind speed data. The dynamic model based on the proposed formulation was able to effectively reproduce the observed equilibrium snow profiles affected by wind drifting. A two‐dimensional model simulation using a 10 m digital elevation model in Muddy Gap, Wyoming was also presented for qualitative validation of the model in the watershed‐scale applications. Additionally, the theoretical extension for preferential snow accumulation process was presented in Appendix . These modeling results together with the observations on the prairie suggested the importance of the snow surface diffusion process in addition to the snow transport. Key Points A practical snow movement equation was formulated for watershed‐scale applications The snow diffusion coefficient due to wind turbulence was derived Theoretical extension for preferential snow accumulation was explored