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Title: THE EFFECT OF LAND-ATMOSPHERE FEEDBACKS ON THE SPATIAL STRUCTURE OF LAND SURFACE FLUXES OVER HETEOGENEOUS TERRAIN

Author
item BERTOLDI, GIACOMO - DUKE UNIVERSITY
item TIMMERMANS, WIM - ITC-THE NETHERLANDS
item ALBERTSON, JOHN - DUKE UNIVERSITY
item Kustas, William - Bill

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 4/25/2006
Publication Date: 9/15/2006
Citation: Bertoldi, G., Timmermans, W.J., Albertson, J.D., Kustas, W.P. 2006. The effect of land-atmosphere feedbacks on the spatial structure of land surface fluxes over heteogeneous terrain. In: Proceedings of the 30th Italian Conference on Hydraulic Engineering (IDRA 2006), September 10-15, 2006, Rome, Italy. Available: http://www.idra2006.it/referee/files/L268.pdf

Interpretive Summary:

Technical Abstract: The ability to understand and accurately map land surface fluxes at the spatial resolutions of human ac-tivity can support efforts to define the impact of anthropogenic induced land cover changes on hydrologi-cal 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 atmos-pheric boundary layer, a procedure now exists for evaluating the typical ecohydrological modeling as-sumption of homogeneous atmospheric variables (i.e. decoupled from surface heterogeneity) over a study region. Ignoring consideration of the feedback effects can lead to erroneous flux estimation since most landscapes are inherently heterogeneous. The LES model of Albertson (1996) has been fully dynamically coupled with an adapted version of the Two-Source Model (TSM) soil vegetation atmosphere transfer scheme described by Norman et al. (1995). The coupled model was applied off-line (i.e. with static uni-form atmospheric variables) and on-line (i.e. with dynamic spatially distributed atmospheric variables) over the Barrax test site in Spain using ASTER soil temperature imagery. In this paper we present a sim-ple scale-dependent method based on wavelet decomposition techniques to account for surface-atmosphere coupling in the estimation of land surface fluxes from remotely sensed data over heterogene-ous terrain. First results of the LES-SVAT simulations confirm the results of Albertson et al., (2001) indi-cating that the correlation between time-averaged surface and air temperatures is dependent on the length scale of the surface features, with a maximum efficiency in the energy transfer at the scale of vari-ability greater than 500 – 1000 m. While the feedback mechanism between surface temperature and air temperature acts to limit the spatial variability in the surface fluxes, as found by Kustas and Albertson (2003), is observed here a more complex interaction between surface properties and surface wind field which tend to increase the spatial variance of surface fluxes.