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United States Department of Agriculture

Agricultural Research Service

Title: Aerodynamic Parameters and Sensible Heat Flux Estimates for a Semi-Arid Ecosystem

Authors
item Prueger, John
item Kustas, William
item Hipps, L - UTAH STATE UNIVERSITY
item Hatfield, Jerry

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 2, 2004
Publication Date: June 15, 2004
Citation: Prueger, J.H., Kustas, W.P., Hipps, L.E., Hatfield, J.L. 2004. Aerodynamic Parameters and Sensible Heat Flux Estimates for a Semi-Arid Ecosystem. Journal of Arid Environments. 57:87-100.

Interpretive Summary: In semi-arid ecosystems there is little water available for evaporation. The lack of water for evaporation causes the available energy to be divided into either heating the air or the soil. One of the problems is the lack of information about semi-arid plant communities that could help understand how these surfaces change throughout the year and the role they play in the global energy balance. A study was conducted on how semi-arid plant communities of grassland, mixed grass and mesquite, and mesquite were different in their aerodynamic parameters. This study was conducted in the Jornada Experimental Range near Las Cruces, New Mexico using different techniques to quantify the energy exchanges. We found that the combination of the shape of plant community and the rolling nature of the landscape created differences in the energy exchanges. These parameters are critical to regional models of energy exchange needed for global studies and this information will help other scientists understand the changes that occur over these large areas of semi-arid vegetation.

Technical Abstract: Aerodynamic parameters of roughness length (z0) and displacement height (d0) for semi-aris grassland, mixed grass-mesquite and mesquite rangeland were computed from eddy covariance measurements of sensible heat flux, standard deviations of vertical velocity and air temperature and mean wind speed within the framework of Monin-Obukhov similarity theory. Reasonable estimates of z0 were obtained for all sites but unrealistic d0 values resulted for most sites except mesquite. Independent estimates for z0 and d0 were also determined at the mesquite site with a traditional wind speed profile method and compared with results computed from an approach using laser altimeter data. Results showed good agreement among approaches. Also, within the framework of flux-variance using, 0t, and derived z0, d0 with u, computed H fluxes were evaluated and compated to eddy covariance measurements.

Last Modified: 11/26/2014
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