Top: histogram of the vertical velocity component in disk model D2G_e-4. The mean value of the distribution is at zero and the FWHM is ≈ 127 ms^-1. The distribution is close to a log-normal distribution. Bottom: contour plot of the vertical RMS velocity component in disk model D2G_e-2. Dotted lines correspond to optical depth τ_z = 1 lines along the vertical direction for an opacity of κ_gas = 100,10,1,0.1,cm²/ g. The line of sight of an observer is indicated by an eye sketch.