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In the framework of an international field program for the study of semi-arid areas, observations were done in the region called ’La Crau’ in southern France. In this paper, the use of the surface radiative temperature for the determination of the sensible heat flux is addressed. We found that, once proper values of the roughness length of momentum (z0) and heat (z0h) are set, the sensible heat flux can be reliably predicted with a one-layer resistance model using standard observations of wind speed and air temperature, together with the surface temperature. The latter quantity has to be known with a precision better than +/-2-degrees-C. From our observations, the value of the parameter B-1 = k-1 In (z0/z0h) was found to be 9.2, which falls between values quoted by Brutsaert (1982) for grass and bluff bodies.