Comparison of the geometric momentum estimate Eq. B.1 to the true momentum for the simulated sample of SBs from the SISSI simulation at different points in time, as indicated by the color scheme. A representative error bar corresponding to uncertainties due to different ways of defining the center (geometric center vs. center of mass) of the SBs and their volume (threshold value for passive-scalar tracer-variable) is shown in the upper-left corner. The geometrical momentum estimate is slightly biased towards larger values, by a factor of ∼ 2.