Global air quality change during the COVID-19 pandemic: Regionally different ozone pollution responses COVID-19

The explosive spread of the 2019 novel coronavirus (COVID-19) provides a unique chance to rethink the relationship between human activity and air pollution. Though related studies have revealed substantial reductions in primary emissions, obvious differences do exist in the responses of secondary pollutants, like ozone (O3) pollution. However, the regional disparities of O3responses and their causes have still not been fully investigated. To better elucidate the interrelationship between anthropogenic emissions, chemical production, and meteorological conditions, O3responses caused by lockdowns over different regions were comprehensively explored at a global scale. Observational signals of air-quality change were derived from multi-year surface measurements and satellite retrievals. With similar substantial drops in nitrogen dioxide (NO2), ozone shows rising signals in most areas of both East Asia and Europe, even up to ∼14 ppb, while a non-negligible declining signal exists in North America, by about 2–4 ppb. Furthermore, the drivers behind the different O3responses are discussed based on meteorological analysis and O3sensitivity diagnosis. On the one hand, O3responses to NO2declines can be affected by the primary dependence on its precursors. On the other hand, it is also highly dependent on meteorological factors, especially temperature. Our study further highlights the great importance of taking into consideration both the regional disparities and synergistic effects of precursor reductions and meteorological influence for scientific mitigation of O3pollution.