Global air quality responses to the COVID-19 pandemic

Tuesday, 8 December 2020: 07:55
Kevin W Bowman1, Kazuyuki Miyazaki1, Susan Anenberg2, Hansen Cao3, Joost de Gouw4, Daven K Henze3, Dylan B. A. Jones5, Christoph Keller6, K. Emma Knowland7, J F Lamarque8, Randall Martin9, Jessica L. Neu1, Lesley E Ott10, Muye Ru11, Thomas Walker12, Paul O Wennberg13, Helen Marie Worden14 and Yuqiang Zhang15, (1)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (2)George Washington University, Washington, DC, United States, (3)University of Colorado Boulder, Boulder, CO, United States, (4)University of Colorado at Boulder, Department of Chemistry, Boulder, United States, (5)University of Toronto, Department of Physics, Toronto, ON, Canada, (6)NASA Goddard Space Flight Center, Global Modeling and Assimilation Office, Greenbelt, MD, United States, (7)Universities Space Research Association Columbia, Columbia, MD, United States, (8)NCAR, Boulder, CO, United States, (9)Washington University in St. Louis, Energy, Environmental & Chemical Engineering, St. Louis, MO, United States, (10)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (11)Duke University, Earth and Ocean Science, Durham, NC, United States, (12)Carleton University, Department of Civil and Environmental Engineering, Ottawa, ON, Canada, (13)California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, United States, (14)National Center for Atmospheric Research, Atmospheric Chemistry Observations & Modeling Laboratory, Boulder, CO, United States, (15)Duke University, Durham, United States
Extraordinary efforts to stem the spread of COVID-19, i.e., “flattening the curve”, led to global but regionally distinct impacts on atmospheric composition over relatively short-term time periods. While these changes are one of the most readily detectable signals from space, their relationship to emissions generally and COVID-19 specifically are not fully understood.

That uncertainty is due in part to the sensitivity of emissions, subsequent air pollution, and impact on human health to timing, location, natural variability, and policy. Using state-of-the-art observations, modeling, assimilation, and epidemiological tools, we explored the pollution pathways between emissions and concentrations and their potential impact on human health.

We find opposing responses in both aerosol and trace gas pollutants for the same reduction in precursor emissions. The sign and magnitude of these responses are a function of the emission distribution, the local photochemical regime of emissions, and the seasonality. In particular, the first lockdowns in China occurred during the late NH winter, while lockdowns on other continents subsequently occurred during the NH Spring and early Summer. These changes in photochemical regimes play a capital role in explaining the differing regional responses. We furthermore show that differential reductions in precursor emissions due to COVID-19 mitigation led to changes in chemical regimes and the relative efficacy of precursors in secondary pollution formation. These results show that the COVID-19 era represents a unique “scenario-of-opportunity” to test how future sectoral reductions could occur and thus may inform future pollution and climate mitigation strategies.