Average speed (top) and divergence (bottom) maps for the first (left) and last (right) hour of the time series computed using a time cadence of Δt = 60 s and a Gaussian sampling window with an FWHM = 1200 km. The direction and magnitude of the horizontal flows are plotted over the divergence maps as arrows, for which a velocity of 0.5 km s^-1 corresponds to exactly the grid spacing. The values displayed at the top are the mean speed and its standard deviation σ_v for the one-hour averaged flow maps.