TRANSLATING WIND MEASUREMENTS FROM WEATHER STATIONS TO AGRICULTURAL CROPS

Logarithmically based functions were used to translate wind-speed measurements from weather stations to cropped fields. The translations adjusted the wind measurements for both instrument siting height and effects of vegetation height and roughness. The roughness of the original measurement site, of the vegetation for which wind data were desired and of the general region, were considered. The transfer function is necessary for wind measurements over clipped grass in order to directly predict evapotranspiration from agricultural crops using the Penman-Monteith equation. Differences in crop height and roughness between clipped grass and taller agricultural crops can reduce wind speed over the taller crops by as much as 50% in the lower internal boundary layer.