The Effect of Land-Atmosphere Feedbacks on the Spatial Structure of Land Surface Fluxes over Complex Terrain

The ability to understand and accurately map land surface fluxes at the spatial resolutions of human activity can support efforts to define the impact of anthropogenic induced land cover changes on hydrological and ecological processes. While remote sensors can map the surface states, the scientific problem arises from an incomplete knowledge of how heterogeneous surface states excite heterogeneity in the states of the lower atmosphere, which feedback on the exchange rates of mass, energy, and momentum across these heterogeneous land surfaces. Through the development and implementation of a framework for merging remotely sensed land surface data into a Large Eddy Simulation (LES) model of the atmospheric boundary layer, a procedure now exists for evaluating the typical ecohydrological modeling assumption of homogeneous atmospheric variables (i.e. decoupled from surface heterogeneity) over a study region. The strength of the feedback effects (or surface-air state coupling), with particular attention to the effect of variability of surface states on atmospheric properties in the surface layer, has been shown in our previous work to depend on both the length scales of the surface features [Albertson et al., 2001] and the magnitude of the contrast in surface states across the features [Kustas and Albertson, 2003]. Ignoring consideration of the feedback effects can lead to erroneous flux estimation since most landscapes are inherently heterogeneous. In this talk we examine new results and present a simple scale-dependent means to account for surface-atmosphere coupling in the estimation of land surface fluxes from remotely sensed data over complex terrain.