Fig. 6. (a) Time series of hourly observed and simulated O3, CO, NO2 and VOCs concentrations at the Taizhou site. The green dash line refers to the secondary standard for ambient air quality (200 μg m–3). (b) Diurnal variations of observed and simulated O3, CO, NO2 and VOCs concentrations averaged from 28 May to 15 June 2018 at the Taizhou site. The error bars represent standard deviation from the mean.