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

Abstract

Aerodynamic parameters of roughness length ( z 0) and displacement height ( d 0) 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 ( σ w and σ T ), and mean wind speed ( u) within the framework of Monin–Obukhov similarity theory. Reasonable estimates of z 0 were obtained for all sites but unrealistic d 0 values resulted for most sites except mesquite. Independent estimates of z 0 and d 0 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, σ T , and derived z 0, d 0 with u, computed H fluxes were evaluated and compared to eddy covariance measurements.