How representative is a point? The spatial variability of surface energy fluxes across short distances in a sand-sagebrush ecosystem

Abstract During the summer of 2001, the spatial variation of the surface energy fluxes across short distances, 16 m to 32 m, was examined over a sagebrush steppe ecosystem in northeastern Colorado. Two eddy covariance micrometeorological stations were used to test the hypothesis that fine-scale variations in the physical properties of the site result in significant variation in the surface energy balance. Through a comparative analysis of the flux measurements, it was found that statistically significant variations in the sensible, latent and soil heat fluxes were present at the study site. These variations were linked to small changes in the near-surface soil moisture content and leaf area index. The results of this study suggest there may be substantial uncertainty surrounding a single point measurement when it is used to represent the exchange of heat and moisture over a large area. This uncertainty must be considered when using in-situ measurements to evaluate remote sensing products or numerical models.