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United States Department of Agriculture

Agricultural Research Service

Title: Mapping Surface Energy Fluxes with Radiometric Temperature

Authors
item KUSTAS, WILLIAM
item Norman, John - UNIVERSITY OF WISCONSIN
item Schmugge, Thomas
item Anderson, Martha - UNIVERSITY OF WISCONSIN

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: January 27, 2000
Publication Date: N/A

Interpretive Summary: Surface temperature observations are available from weather satellites and provide a unique surface boundary condition for monitoring regional evapotranspiration. Many remote sensing models do not evaluate the separate contributions from vegetation transpiration and soil evaporation to the total. This leads to large uncertainties in evapotranspiration predictions over heterogeneous surfaces. More reliable results have been obtained using two-source models that consider separating the contributions of soil and vegetation to surface temperature observations and to the evapotranspiration flux. In this chapter, a detailed plant-environment model (Cupid) will be used to investigate surface temperature and evapotranspiration for a wide range of environmental conditions. The predicted surface temperatures from Cupid will be used as input to a simple two-source model that can be applied operationally with satellite observations of surface temperature. Using the Cupid simulations, the capability of the two-source model in predicting relative contributions of soil evaporation and vegetation transpiration under more extreme conditions is evaluated. Uncertainty in evapotranspiration estimation due to significant heterogeneity is examined using the simplified two-source model.

Technical Abstract: Radiometric surface temperature observations are available from weather satellites and provide a unique spatially distributed boundary condition for surface energy balance modeling at regional scales. Many remote sensing models have treated the surface as a single-source, neglecting the partitioning of energy fluxes between the vegetation and soil/substrate, and ignoring the effect of sensor view angle on the surface temperature observation. This can result in large differences between aerodynamic and radiometric surface temperatures. Recent studies have shown that single-source approaches can lead to large uncertainties in surface flux predictions over heterogeneous surfaces, especially landscapes with partial canopy cover. More reliable results have been obtained using two-source models that consider separately the contributions of soil/substrate and vegetation to surface temperature observations and to the turbulent fluxes. In this chapter, a detailed plant-environment (PE) model (Cupid) will be used to investigate the aerodynamic-radiometric temperature relationship for a wide range of environmental conditions. The predicted radiometric temperature from Cupid will be used as input to a simple two-source model that is operational either using single or multiple radiometric surface temperature observations. Using the Cupid simulations, the capability of the two-source model to predict energy flux partitioning between soil and vegetation under more extreme conditions is evaluated. Uncertainty in flux estimation due to significant subpixel heterogeneity is examined using the simplified two-source model.

Last Modified: 9/10/2014
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