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United States Department of Agriculture

Agricultural Research Service

Title: Estimation of Area-Average Sensible Heat Flux Using a Large Aperture Scintillometer During the Semi-Arid-Land-Surface-Atmosphere (Salsa) Experiment 1258

Authors
item Chehbouni, A - IRD/IMADES, HERMOSILLO
item Kerr, Y - CESBIO, TOULOUSE, FRANCE
item Watts, C - IMADES, HERMOSILLO, MEX
item Hartogensis, O - WAGENINGEN UNIV, NETH.
item Goodrich, David
item Scott, R - UNIV OF ARIZ
item Schieldge, J - JET PROPULSION LAB
item Lee, K - UNIV OF ARIZ
item Shuttleworth, W - UNIV OF ARIZ
item Dedieu, G - CESBIO, TOULOUSE, FRANCE

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 3, 1999
Publication Date: N/A

Interpretive Summary: One of the important components of the energy budget over the land surface is the sensible heat flux. This is the quantity of heat re-radiated back to the atmosphere from the land surface. This is one of the quantities that must be measured to help estimate how much water is being transpired by plants and evaporated from the soil. A new instrument, a scintillometer, is able to measure sensible heat flux over large areas. I this study its ability to estimate the sensible heat flux was measured over two very different surfaces, mesquite and grass. The scintillometer was able to accurately estimate the sensible heat flux over this diverse land cover. This is of interest because this approach offers a reliable means to validate remotely-sensed estimates of the energy budget over distances comparable to those measured by satellite sensors.

Technical Abstract: The use of a large aperture scintillometer to estimate sensible heat flux has been successfully tested before. Most of these investigations, however, have been confined to homogeneous or to sparse single vegetation-type surfaces. The use of the scintillometer over surfaces made up of contrasting vegetation types is problematic because it requires estimates of effective roughness length and effective displacement height in order t derive area-average sensible heat from measurements of the refractive index. In this study, an approach based on a combination of scintillometer measurements and an aggregation scheme has been used to derive area-average sensible heat flux over two adjacent and contrasting vegetation patches: grass and mesquite. The performance of this approach was assessed during the 1997 Semi-Arid-Land-Surface-Atmosphere (SALSA) campaign. The results show that the combined approach performed remarkably well. The correlation coefficient between measured and area-average sensible heat flux was about 0.95. This is of interest because this approach offers a reliable means to validate remotely-sensed estimates of surface fluxes at comparable spatial scales.

Last Modified: 12/24/2014
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