Spatial-Temporal Variability in Turbulent Fluxes during Spring Snowmelt

Abstract

Turbulent sensible and latent heat exchanges play an important role in melting snow covers, contributing 30–40% of overall melt energy with daily values reaching over 50% on warm, cloudy days (Morris, 1989). The spatial variability of these turbulent fluxes across a basin and the relative importance of the differences is not well known. This paper specifically addresses small-scale variabilities in sensible and latent energy fluxes related to topographically induced wind speed variations. A simple wind model was used to simulate topographic effects on the surface wind field. Hourly wind observations were areally distributed by the model and used to calculate spatially variable sensible and latent turbulent heat fluxes for a small (63 km2) research catchment dominated by open tundra vegetation. Simulations showed that, even though the study area is characterized by relatively low relief (average slope 3°), the small-scale sensible and latent heat fluxes varied considerably throughout the basin. The resulting variations in snowmelt rates play an important role in the development of a patchy snow cover. Overall, turbulent fluxes within the research area varied by as much as 20% from the mean, leading to differences in potential snowmelt of up to 70 mm snow water equivalent over the entire melt period.