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(a–c) Spatial distribution of simulated MDA8 O3 concentrations before and during COVID-19 lockdown period. (d–f) Averaged diurnal variations of modeled O3 concentrations in three major cities (Purple squares represent the three weeks before COVID-19 outbreak, yellow squares represent Case 1 in COVID-19 lockdown, and green squares represent Case 2 in COVID-19 lockdown). (g–i) Spatial distributions of O3 production sensitivity before and during COVID-19 lockdown.
