Fig. 5.

Average diurnal evolution of trace gases measured by DOAS (μg m⁻³), temperature (°C) and solar radiation (Wm⁻²) during the pandemic lockdown period (starting 24/03/2020; blue line), compared to their average diurnal pattern for the same time period during the preceding 2-years (i.e. March and April 2018–2019, inclusive; red line). The difference between the two datasets (i.e. the 2020 lockdown period and the March and April 2018–2019 baseline) is also shown (green line), along with the O₃/solar radiation ratio (bottom right), coloured by NO₂ concentration (μg m⁻³). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)