Aerodynamic parameters and sensible heat flux estimates for a semi-arid ecosystem

Aerodynamic parameters of roughness length (z0) and displacement height (d0) for semi-arid grassland, mixed grass–mesquite and mesquite rangeland were computed from eddy covariance measurements of sensible heat flux (H), standard deviations of vertical velocity and air temperature (σw and σT), and mean wind speed (u) within the framework of Monin–Obukhov similarity theory. Reasonable estimates of z0 were obtained for all sites but unrealistic d0 values resulted for most sites except mesquite. Independent estimates of z0 and d0 were also determined at the mesquite site with a traditional wind speed profile method and compared with results computed from an approach using laser altimeter data. Results showed good agreement among approaches. Also, within the framework of flux–variance using, σT, and derived z0, d0 with u, computed H fluxes were evaluated and compared to eddy covariance measurements.