Evolution of the mass-weighted LOS velocity dispersion as a function of the imposed LOS–velocity threshold for both simulations and observations. Colored curves show the simulated models, averaged over the corresponding sets of synthetic sky maps, with SN-driven runs shown as colored dotted lines and large-scale turbulent-forcing runs as colored dashed lines. Black curves correspond to the observational H I data from S25: solid for the full dataset, dotted for the outer Galaxy, and dash-dotted for the inner Galaxy.