a) Cuts through the maps of the circulation velocity v^ac for the average supergranule outflow region at 40° latitude (shown in Fig. 6), at y = 0. The TD and LCT maps were derived from HMI Dopplergrams and intensity images. The thin lines denote estimates of the variability of the data as obtained from dividing the 336 datasets into eight parts. The 1σ level is shown. b) As a), but for the average supergranule inflow region at 40° latitude.