16 Years (2006-2021) of Surface Ozone Measurements in Córdoba (Southern Spain): Trends and the Impact of the COVID-19 Lockdown.

Surface ozone concentrations (O 3 ) during the period 2006-2021 are analysed at Córdoba city (southern Iberian Peninsula) in suburban and urban sampling sites. The aims are to present the levels and temporal variations, to explore trends and to quantity the variation in O 3 concentrations in the context of the COVID-19 lockdown. The O 3 means are higher in the suburban station (62 µg m -3 and 51.3 µg m -3 ), being the information level threshold only exceeded twice during this period. The daily evolution shows a maximum at about 17:00 UTC, whereas the minimum is reached at about 9:00 UTC, with higher levels in the suburban station. The seasonal evolution of this daily cycle also presents monthly differences in shape and intensity between stations. The trends are analysed by means of daily averages and daily 5th and 95th percentiles, and they show a similar increase in all of these parameters, with special emphasis on the daily P95 concentrations, with 0.27 µg m -3 year -1 and 0.24 µg m -3 year -1 . Finally, the impact of the COVID-19 lockdown shows a decline in O 3 concentrations over 10%.