Fig. 5. Scatterplots and linear regressions of observed (OBS) and simulated (SIM) mean (a) PM2.5 and (d) O3 concentrations in 367 cities for the Nudging and base simulations during pollution episodes (PM2.5 from 11 to 19 January; O3 from 28 May to 15 June 2018). The mean results of the model simulations with observations overlaid (circle) for PM2.5 ((b), (c)) and O3 ((e), (f)) over China during the studying periods are also shown.