Fig. 8.

Average diurnal evolution of trace gases (NO, NO₂, O₃ and the 15 most abundant NHMC's; molecules cm⁻³), temperature (K) and relative humidity (%), with modelled formaldehyde (HCHO; molecules cm⁻³) and methyl glyoxal (MeGly; molecules cm⁻³) and radical species (OH, HO₂ and RO₂; molecules cm⁻³) 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 5-years (i.e. March and April 2018–2019, inclusive; red line). Measurement site: Eltham, south London. Note: in the NO_x panel, NO₂ is given by solid lines and NO by dashed lines; also, in the HCHO/MeGly panel, HCHO is given by solid lines and MeGly by dashed lines. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)