Turbulence and Horizontal Advection across a Canopy Edge: Measurements and Comparison to Modeled Results

Standard micrometeorological methods rely upon the assumption of horizontal homogeneity. The surface of the earth is characterized by heterogeneity however, and efforts to measure the exchange between representative terrestrial ecosystems and the atmosphere require investigators to work in areas where measurements are compromised by poor fetch. A growing body of work addresses this problem and also provides guidance in site selection. Energy budget closure and horizontal advection estimated during a field campaign performed across a transition from bare ground into a crop canopy elucidate the effects of inhomogeneity on surface-atmosphere exchange. The magnitude of horizontal advection calculated using measurements and simple shape functions remains significant under near-neutral conditions at a distance of 20 canopy heights downwind of the change in surface. Field estimates of scalar and turbulent quantities compare well with results from of a two-dimensional higher-order closure model.