Horizontal and vertical distribution of wind speed in a vegetation canopy.

Wind speed measurements within a maize row canopy were carried out to investigate the horizontal and vertical variability of the mean wind speed and its standard deviation. Attention was given to finding adequate scaling parameters of the within-canopy wind speed profiles under various atmospheric stratification states. A validation of existing model simulations was also carried out. The horizontal mean wind speed and its standard deviation can vary about 20% from its spatial mean value. During day time and night time the friction velocity appears to be a good scaling parameter. Clear nights, however, are exceptions, when the wind speed above the crop drops to a very low value. Then the free convection velocity appears to be an appropriate scaling parameter for the within-canopy processes. The canopy models of Wilson & Shaw [Journal of Applied Meteorology (1977) 16, 1197-1205] and Li et al. [Boundary-Layer Meteorology (1985) 33, 77-84] were found to simulate the spatially averaged mean wind profile within the range of the horizontal variability. (Abstract retrieved from CAB Abstracts by CABI’s permission)