Abstract
The recent COVID-19 pandemic with its countermeasures, e.g. lock-downs, resulted in decreases in emissions of various trace gases. Here we investigate the changes of ozone over Europe associated with these emission reductions using a coupled global/regional chemistry climate model. We conducted and analysed a business as usual and a sensitivity (COVID19) simulation. A source apportionment (tagging) technique allows us to make a sector-wise attribution of these changes, e.g. to natural and anthropogenic sectors such as land transport. Our simulation results show a decrease of ozone of 8% over Europe in May 2020 due to the emission reductions. The simulated reductions are in line with observed changes in ground-level ozone. The source apportionment results show that this decrease is mainly due to the decreased ozone precursors from anthropogenic origin. Further, our results show that the ozone reduction is much smaller than the reduction of the total NO x emissions (around 20%), mainly caused by an increased ozone production efficiency. This means that more ozone is produced for each emitted NO x molecule. Hence, more ozone is formed from natural emissions and the ozone productivities of the remaining anthropogenic emissions increase. Our results show that politically induced emissions reductions cannot be transferred directly to ozone reductions, which needs to be considered when designing mitigation strategies.
Highlights
The COVID-19 pandemic has a strong socioeconomic impact [1]
Lower tropospheric ozone response to emission reductions In our analyses we focus on the results of the regional model over the area 15 ◦W–25 ◦E to 35 ◦N–70 ◦N, which is centred over Europe
We conducted a sensitivity experiment (COVID19) to analyse the processes occurring with respect to lower tropospheric ozone in a period of reduced anthropogenic emissions as during the recent COVID-19 pandemic compared to an emission scenario without the impact of the COVID-19 pandemic (BAU)
Summary
The COVID-19 pandemic has a strong socioeconomic impact [1]. As one consequence, in 2020 reduced carbon dioxide (CO2) emissions from various sectors have been noted in many regions worldwide (e.g. [2, 3]). In 2020 reduced carbon dioxide (CO2) emissions from various sectors have been noted in many regions worldwide [2, 3]) Such reductions of CO2 emissions are expected to be related to air quality improvements through reduced co-emission of pollutants. Reductions of particulate matter and nitrogen-dioxide (NO2) have been observed in northern China [4]. In the case of NO2 a reduction has been observed from space in various regions all over the world [5]. It was noted that ozone surface levels have partly increased despite the decrease of emissions of the ozone precursor NO2 It was noted that ozone surface levels have partly increased despite the decrease of emissions of the ozone precursor NO2 (e.g. [4, 6])
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