SENSIBLE HEAT-FLUX RADIOMETRIC SURFACE-TEMPERATURE RELATIONSHIP FOR 8SEMIARID AREAS

Measurements of sensible heat flux, radiometric surface temperature, a ir 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 o f kB-1, a quantity related to the resistance of heat versus momentum t ransfer at the surface, for the individual sites varied between 3.5 an d 12.5. A preliminary test of the utility of an excess resistance base d on the mean value of kB-1 showed that the difference between the mea n 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 conside rable scatter with values ranging between and beyond the theoretical c urves for bluff rough and permeable rough surfaces.