Time and horizontally volume-averaged square-root of the Péclet number compared with the data for the cumulative distribution function F(r_max/R) = 1 − F(Δr_max/R) calculated from the vertical kinetic energy flux. The best fit to this data from simulation YS4 is a Gumbel distribution with the parameters indicated in Table 2. The Péclet number has been normalized and shifted vertically. The dashed line indicates a Péclet number that is also shifted in radius so that the common shape is clear. The heavy vertical black line marks the convective boundary.