A plane regression analysis of 6 h tropospheric wind data from the A/B-scale array during phase III of GATE has been used to produce a 21-day time series of horizontal wind components, divergence and vorticity averaged over the A/B-scale area. Each series has been filtered with nine-point symmetric filters to isolate diurnal and semidiurnal variations in ten 2-day intervals. Phase mean estimations of diurnal amplitude and semidiurnal range and appropriate confidence limits an thus obtained. The time series variance attributable to these signals is compared with that associated with variability on the synoptic time scale. Results show that both diurnal and semidiurnal oscillations contribute significantly to the daily variation in the horizontal vector wind between the surface and 100 mb. The vorticity time series contain only small daily variations, whereas the divergence time series contain a diurnal component of daily variation which is significant at most levels. The corresponding diurnal variability in vertical motion is comparable with the variance associated with time scales greater than the order of 2 days.