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United States Department of Agriculture

Agricultural Research Service

Title: Large Eddy Simulation over Heterogeneous Terrain with Remotely Sensed Land Surface Conditions

Authors
item Albertson, John - UNIV OF VIRGINIA
item Kustas, William
item Scanlon, Todd - UNIV OF VIRGINIA

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 25, 2000
Publication Date: N/A

Interpretive Summary: A framework is developed to explore the coupling between the land and the atmospheric boundary layer using a three-dimensional, turbulence, large eddy simulation (LES) model over remotely sensed land surface images. The coupled set of equations is integrated with boundary conditions from a rangeland watershed, and analysis is conducted to quantify the transmission nof surface heterogeneity information into the lower atmosphere. This effor reflects a merging of active lines of research using remotely sensed land surface properties to study water and energy fluxes and the use of LES to study impacts of surface variability on the lower atmosphere. Analysis of the results reveals that the feedback strength between the land and the atmosphere is shown to be scale-dependent for the range of length scales studied. This suggests that significant changes in regional land use and/or agricultural practices could affect local and regional climate. Future research in this area will greatly enhance our understanding of the feedback effects of agricultural and resource management decisions on local and regional climate. This is a fundamental step in addressing the effects of climate change on agricultural resources and will lead to the development of mitigative strategies.

Technical Abstract: A framework is developed to explore the coupling between the land and the atmospheric boundary layer using three-dimensional turbulence simulation over remotely sensed land surface images. The coupled set of equations is integrated with boundary conditions from day 221 of the Monsoon 90 experiment, and analysis is conducted to quantify the transmission of surface heterogeneity information into the Atmospheric Boundary Layer (ABL). The LES model incorporates: radiant energy availability; spatial fields of remotely observed surface cover, temperature, and moisture; and, the ability to account for the separate contributions of soil and vegetation to the mass and energy exchanges. This effort reflects a merging of active lines of research using remotely sensed land surface properties to study water and energy fluxes and the use of LES to study impacts of surface variability on ABL processes. Analysis of the results reveals: (i) spatial patterns in time-averaged air temperature in the lower boundary layer are correlated with surface temperature fields; (ii) the spatial variability in the mean air temperature (at z=7m) is less than 1/10th of the magnitude of the underlying surface temperature variability; (iii) the horizontal standard deviation of mean air temperature decreased logarithmically with height in the atmospheric surface layer; and (iv) the mean air temperature contains spatial variability induced preferentially from the large spatial scale variations in surface temperature. Hence, the feedback strength between the land and the atmosphere is shown to be scale-dependent for the range of length scales studied here.

Last Modified: 9/20/2014
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