Temporal evolution of the average vertical velocity in depth, from −1500 km to +500 km, the surface being at 0 km, computed from 48 exploding granules at their center. On the surface Vz is at 0.9 km s⁻¹, but there is a peak at 3 km s⁻¹ at 200 km below the surface at the birth of the granule. The different curves correspond first to the onset of granule parent at t(birth)−1 min up to t(birth)+30 min. We observe a clear increase in the upflow velocity just before the birth of the exploding granule at z = 0 (surface) and then a monotonic decrease in time of the Vz component.