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United States Department of Agriculture

Agricultural Research Service

Title: Issues in Monitoring Evapotranspiration with Radiometric Temperature Observations

Authors
item Kustas, William
item Albertson, John - UNIV OF VA, CHARLOTSVL,VA
item Scanlon, Todd - UNIV OF VA, CHARLOTSVL,VA
item Cahill, Anthony - TEXAS A&M, COLL STA, TX

Submitted to: International Association of Hydrological Science
Publication Type: Proceedings
Publication Acceptance Date: June 6, 2000
Publication Date: September 25, 2001

Interpretive Summary: Remotely sensed surface temperature from satellites has the potential of serving as a key boundary condition defining the degree to which surface radiation is used for vegetation growth and plant water use. However, use of remotely sensed surface temperature in standard equations for computing plant water use has not been successful in general because of problems with hexisting approaches. Numerous studies have explored ways to account for deficiencies in existing approaches using experimental data. Field observations, collected during the 1999 Southern Great Plains Experiment over four field sites comprising the major land cover types for this region, are used to evaluate these approaches. The results suggest these schemes need site specific calibration and;therefore, are not useful for regional applications. An alternative approach which is a more physically-based approach, yet simple and reduces the impact of errors in remote sensing surface temperature observations, is presented. Results indicate that this new procedure could provide more reliable plant water use estimates for large areas using satellite data.

Technical Abstract: Surface temperature serves as a key boundary condition defining the degree to which surface radiation is partitioned into sensible and latent heat fluxes. However, use of radiometric surface temperature in standard bulk transport equations for computing heat fluxes has not been successful in general. This has been attributed to the significant differences existing between the radiative and the so-called aerodynamic temperature of the surface. Numerous studies have explored ways of accounting for the discrepancies between radiometric and aerodynamic temperatures by either adjusting parameters in the aerodynamic resistance formulations or developing functional relationships between aerodynamic and radiometric temperatures. Radiometric temperature and surface flux observations, collected during the 1999 Southern Great Plains Experiment over four field sites comprising the major land cover types for this region, are used to evaluate these approaches. The results suggest that these correction schemes need site specific calibrations and; therefore, are not useful for regional applications. An alternative approach which implicitly accounts for the main factors affecting radiometric and aerodynamic temperatures and reduces the impact of errors in radiometric temperature observations is presented.

Last Modified: 4/18/2014
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