Reasons for the observed tropospheric ozone weakening over south-western Europe during COVID-19: Strict lockdown versus the new normal.

In this work we investigate the variation in tropospheric ozone concentrations in south-western Europe in March and April 2020 in the context of COVID-19 disease, and to what extent the former situation was recovered one year after the pandemic outbreak. To carry this study, data from 15 regional background sites in Spain, from 2010 onwards, are used. Historic (2010-2019) and most recent tropospheric ozone concentrations are compared. March and April 2020 ozone concentrations declined over 15% in most cases, rising to 23-28% at sites facing the Mediterranean. Most of the decay was related to the reduction of hemispheric background concentrations, but those sites downwind continental emissions from the Iberian Peninsula and neighbouring countries experienced an additional lessening. By exploring O

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Déclaration de conflit d'intérêts

Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.