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Determination of sensible heat flux over sparse canopy using thermal infrared data

William P. Kustas·B. J. Choudhury·M. S. Moran·R. J. Reginato·R. D. Jackson·L. W. Gay·H. L. Weaver
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Abstract

Surface temperatures, T s , were estimated for a natural vegetative surface in Owens Valley, California, with infrared thermometric observations collected from an aircraft. The region is quite arid and is composed primarily of bushes (∼30%) and bare soil (∼70%). Application of the bulk transfer equation for the estimation of sensible heat, H , gave unsatisfactory values when compared to Bowen ratio and eddy correlation methods over a particular site. This was attributed to the inability with existing data to properly evaluate the resistance to heat transfer, r ah . To obtain appropriate r ah -values the added resistance to heat transfer, kB −1 , was allowed to vary although there is both theoretical and experimental evidence that kB −1 for vegetative surfaces can be treated as constant. The present data indicate that for partial canopy cover under arid conditions kB −1 may be a function of T s measured radiometrically. The equation determining kB −1 was simplified and tested over another arid site with good results; however, this had a limited data set (i.e., 6 data points). The dimensionless kB −1 equation is simplified for use over full canopy cover and is shown to give satisfactory estimates of H over a fully-grown wheat crop.

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William P. Kustas, B. J. Choudhury, M. S. Moran, R. J. Reginato, R. D. Jackson, L. W. Gay, H. L. Weaver. 1989. Determination of sensible heat flux over sparse canopy using thermal infrared data. https://doi.org/10.1016/0168-1923(89)90017-8

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