Some aerodynamic features of a cotton canopy

Analysis of profiles measured over irrigated cotton in the Sudan Gezira showed that the crop boundary layer remained stable throughout most of the day. The shape of wind profiles measured within the canopy suggested that momentum was absorbed mostly in the upper layers of the canopy, with the lower regions remaining isolated from the microclimate above. A similarity analysis based on dynamic scaling factors yielded a generalized wind profile from which momentum diffusivities and mixing lengths were calculated. The analysis showed that aerodynamic features of the upper layers of the canopy were characterized by the friction velocity and the height of the zero-plane displacement