Sensible Heat Flux-Radiometric Surface Temperature Relationship for Eight Semiarid Areas

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  • a Institute use of Hydrology, Wallingford, Oxfordshire, United Kingdom
  • | b USDA-ARS, Hydrology Laboratory, Beltsville, Maryland
  • | c USGS Water Resources Division, Carson City, Nevada
  • | d USDA-ARS, U.S. Water Conservation Laboratory, Phoenix, Arizona
  • | e Agricultural University, Wageningen, the Netherlands
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Abstract

Measurements of sensible heat flux, radiometric surface temperature, air temperature, and wind speed made at eight semiarid rangeland sites were used to investigate the sensible heat flux-aerodynamic resistance relationship. The individual sites covered a wide range of vegetation (0.1–4 m tall) and cover (3%–95% bare soil) conditions. Mean values of kB−1, a quantity related to the resistance of heat versus momentum transfer at the surface, for the individual sites varied between 3.5 and 12.5. A preliminary test of the utility of an excess resistance based on the mean value of kB−1 showed that the difference between the mean estimated and measured sensible heat fluxes varied ±60 W m−2 for the eight semiarid sites. For the eight sites the values of kB−1 were plotted against the roughness Reynolds number. The plot showed considerable scatter with values ranging between and beyond the theoretical curves for bluff rough and permeable rough surfaces.

Abstract

Measurements of sensible heat flux, radiometric surface temperature, air temperature, and wind speed made at eight semiarid rangeland sites were used to investigate the sensible heat flux-aerodynamic resistance relationship. The individual sites covered a wide range of vegetation (0.1–4 m tall) and cover (3%–95% bare soil) conditions. Mean values of kB−1, a quantity related to the resistance of heat versus momentum transfer at the surface, for the individual sites varied between 3.5 and 12.5. A preliminary test of the utility of an excess resistance based on the mean value of kB−1 showed that the difference between the mean estimated and measured sensible heat fluxes varied ±60 W m−2 for the eight semiarid sites. For the eight sites the values of kB−1 were plotted against the roughness Reynolds number. The plot showed considerable scatter with values ranging between and beyond the theoretical curves for bluff rough and permeable rough surfaces.

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