A formula for determination of the roughness height for turbulent heat transfer between the land surface and the atmosphere over bare soil surfaces

Roughness height for heat transfer is a crucial parameter in estimation of heat transfer between the land surface and the atmosphere, especially when radiometric measurements are used. Although many empirical formulations have been proposed, the uncertainties associated with these formulations are shown to be large, especially over sparse canopies. In this contribution, a simple physically based formula is derived for the estimation of the roughness height for heat transfer for bare soil surfaces. The new formula is validated with measurements collected in a filed campaign in Xiaotangshan, near Beijing, China in 2002. The present model in further shown to be able to explain the diurnal variation in the roughness height for heat transfer. The turbulent heat fluxes estimated using radiometric measurements as inputs are markedly improved when this new formula is used.