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COVID-19 Pandemic Research

2020 - 2024

NOAA and CIRES researchers have led efforts to better understand the atmospheric implications of our global COVID-19 pandemic. Our scientists conducted air quality studies and made observations during multiple phases of the COVID-19 pandemic. These efforts have resulted in scientific findings related to ozone pollution and other air quality challenges. CSL researchers have published or contributed to peer-reviewed science papers on these topics:

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IGAC Activity

• He, J., C. Harkins, K. O'Dell, M. Li, C. Francoeur, K.C. Aikin, S. Anenberg, B. Baker, S.S. Brown, M.M. Coggon, G.J. Frost, J.B. Gilman, S. Kongdragunta, A. Lamplugh, C. Lyu, Z. Moon, B. Pierce, R.H. Schwantes, C.E. Stockwell, C. Warneke, K. Yang, C.R. Nowlan, and G.G. Abad, COVID-19 perturbation on US air quality and human health impact assessment, PNAS Nexus, doi:10.1093/pnasnexus/pgad483 2024. In this work, we develop an emission processing system to produce detailed estimates of air emissions of air pollutants over the US, capable of near real-time emission estimates (1-3 month lag). We demonstrate the reliability of our emission estimates from primary sources during the COVID-19 pandemic lock-down and rebounding periods in a 3-dimensional numerical model in conjunction with surface and satellite observations. We find the COVID-19 pandemic affects US emissions across many energy-dependent and economic activities. The emission reductions due to the COVID-19 pandemic persist to summer 2021 especially for nitrogen oxides, due to the continuous pandemic impacts on traffic and economic activities despite the stay-at-home orders being lifted. We also find changes in meteorological conditions affect air quality differently across the US, which needs to be assessed in a 3-dimensional chemical transport model in order to better understand e mission impacts on regional air quality. The COVID-19 pandemic results in annual decreases of 10-15% in emissions of ozone and fine particle gas-phase precursors, which lead to 3-4% decreases in annual 4th maximum of daily maximum 8-hour average ozone and annual fine particles and therefore a 4-5% decrease in premature mortality attributable to ambient air pollution. The results suggest sustained efforts to control emissions from human activities over long time periods can lower future concentrations of air pollutants and lessen human health impacts in the future.
• Guevara, M., H. Petetin, O. Jorba, H. Denier van der Gon, J. Kuenen, I. Super, C. Granier, T. Doumbia, P. Ciais, Z. Liu, R.D. Lamboll, S. Schindlbacher, B. Matthews, and C. Pérez Garcia-Pando, Towards near-real time air pollutant and greenhouse gas emissions: Lessons learned from multiple estimates during the COVID-19 pandemic, Atmospheric Chemistry and Physics, doi:10.5194/acp-23-8081-2023, 2023. The 2020 COVID-19 crisis caused an unprecedented drop in anthropogenic emissions of air pollutants and greenhouse gases. Given that emissions estimates from official national inventories for the year 2020 were not reported until two years later, new and non-traditional datasets to estimate near-real time emissions became particularly relevant and widely used in international monitoring and modelling activities during the pandemic. This study investigates the impact of the COVID-19 pandemic on 2020 European (the 27 EU Member States and the UK) emissions by comparing a selection of such near-real time emission estimates, with the official inventories that were subsequently reported in 2022 under the Convention on Long-Range Transboundary Air Pollution (CLRTAP) and the United Nations Framework Convention on Climate Change (UNFCCC). Results indicate that annual changes in total 2020 emissions reported by official and near-real time estimates are fairly in line for most of the chemical species, with NOx and fossil fuel CO₂ being reported as the ones that experienced the largest reduction in Europe in all cases. However, large discrepancies arise between the official and non-official datasets when comparing annual results at the sector and country level, indicating that caution should be exercised when estimating changes in emissions using specific near-real time activity datasets, such as time mobility data derived from smartphones.
• Peischl, J., K.C. Aikin, B.C. McDonald, C. Harkins, A.M. Middlebrook, A.O. Langford, O.R. Cooper, K.-L. Chang, and S.S. Brown, Quantifying anomalies of air pollutants in 9 U.S. cities during 2020 due to COVID-19 lockdowns and wildfires based on decadal trends, Elementa: Science of the Anthropocene, doi:10.1525/elementa.2023.00029, 2023. COVID-19 lockdowns led to to decreased emissions from cars and trucks since many people worked from home instead of driving to work. As a result, pollution decreased in many U.S. cities. This study quantifies how much of the pollution decreases were due to decreased emissions and how much were due to weather.
• Cao, H., D.K. Henze, K. Cady-Pereira, B.C. McDonald, C. Harkins, K. Sun, K.W. Bowman, T.-M. Fu, and M.O. Nawaz, COVID-19 lockdowns afford the first satellite-based confirmation that vehicles are an under-recognized source of urban NH₃ pollution in Los Angeles, Environmental Science & Technology Letters, doi:10.1021/acs.estlett.1c00730, 2022. Using satellite remote sensing observations, which observed changes in nitrogen dioxide (NO₂) and ammonia (NH₃) over Los Angeles during the COVID-19 pandemic, the vehicular contribution to ammonia is derived from space-borne observations. The study reveals that transportation plays a substantially larger role in the contribution to ammonia than previously thought. Ammonia is an important gas-phase precursor to secondary fine particulate matter (PM_2.5), which impacts human health. The study also demonstrates the first application of NOAA CrIS satellite data in constraining vehicular emissions of NH₃, which can help inform sustainable transportation policies.
• Chang, K.-L., O.R. Cooper, A. Gaudel, M. Allaart, G. Ancellet, H. Clark, S. Godin-Beekmann, T. Leblanc, R.V. Malderen, P. Nedelec, I. Petropavlovskikh, W. Steinbrecht, R. Stubi, D.W. Tarasick, and C. Torres, Impact of the COVID-19 economic downturn on tropospheric ozone trends: an uncertainty weighted data synthesis for quantifying regional anomalies above western North America and Europe, AGU Advances, doi:10.1029/2021AV000542, 2022. The study shows the long term increase of ozone above western North America and Europe since 1994, but with a small but sharp decrease in 2020 due to pandemic impacts on emissions. Read More
• Lopez-Coto, I., X. Ren, A. Karion, K. McKain, C. Sweeney, R.R. Dickerson, B. McDonald, D.Y. Ahn, R.J. Salawitch, H. He, P.B. Shepson, and J.R. Whetstone, Carbon monoxide emissions over the Washington, DC, and Baltimore metropolitan area: Recent trend and COVID-19 anomaly, Environmental Science & Technology, doi:10.1021/acs.est.1c06288, 2022. A downward trend in carbon monoxide (CO) emissions from the Washington, DC - Baltimore, MD metropolitan area is quantified using atmospheric concentration measurements from aircraft and an inverse modeling methodology. The observed trend is consistent with the Environmental Protection Agency estimates for the area based on bottom-up estimation methods. In addition, a significant drop in CO emissions is observed in this urban region during April and May 2020 caused by the reduction in mobility induced by the COVID-19 pandemic response.
• Meidan, D., S.S. Brown, V. Sinha, and Y. Rudich, Nocturnal atmospheric oxidative processes in the Indo-Gangetic Plain and their variation during the COVID-19 lockdowns, Geophysical Research Letters, doi:10.1029/2021GL097472, 2022. The Indo-Gangetic Plain (IGP) is one of the most polluted regions on earth, with poor air quality affecting the majority of the Indian population. The atmospheric chemistry that transforms major regional emissions into harmful secondary pollutants is complex. Researchers quantify, for the first time, several important oxidative processes and show the potential for substantial oxidation of sulfur, biogenic volatile organic compounds (VOCs) and the production of chlorine through unconventional chemistry in the IGP. They further show how these chemical cycles varied due to the emission reductions as a result of COVID-19 lockdowns, findings that might serve to define their sensitivity to future emission changes in the region.
• Bouarar, I., B. Gaubert, G.P. Brasseur, W. Steinbrecht, T. Doumbia, S. Tilmes, Y. Liu, T. Stavrakou, A. Deroubaix, S. Darras, C. Granier, F. Lacey, J.-F. Muüller, X. Shi, N. Elguindi, and T. Wang, Ozone anomalies in the free troposphere during the COVID-19 pandemic, Geophysical Research Letters, doi:10.1029/2021GL094204, 2021. The reduction in the emissions of primary air pollutants during the 2020 COVID-19 pandemic has generated perturbations in the chemical state of the atmosphere. A global Earth system model that accounts for chemical, physical and dynamical processes in the atmosphere and for the coupling between the atmosphere, the ocean and the land surface, indicates that the abundance of tropospheric ozone was significantly reduced during the pandemic in response to reduced emissions of primary pollutants associated with restrictions of air traffic and economic activities. These findings are consistent with observed ozone anomalies during the summer of 2020.
• Doumbia, T., C. Granier, N. Elguindi, I. Bouarar, S. Darras, G. Brasseur, B. Gaubert, Y. Liu, X. Shi, T. Stavrakou, S. Tilmes, F. Lacey, A. Deroubaix, and T. Wang, Changes in global air pollutant emissions during the COVID-19 pandemic: A dataset for atmospheric chemistry modeling, Earth System Science Data, doi:10.5194/essd-13-4191-2021, 2021. In order to fight the spread of the global COVID-19 pandemic, most of the world countries took control measures such as lockdowns during a few 30 weeks to a few months. These lockdowns had significant impacts on economic and personal activities in many countries. Global and regional chemistry-transport model studies were performed in order to analyze the impact of these lockdowns on the distribution of atmospheric compounds. In order to provide input for global and regional model simulations, a dataset providing adjustment factors (AFs) that can easily be applied to global and regional emission inventories was developed. This dataset provides, for the January-August 2020 period, gridded AFs at a 0.1x0.1 latitude/longitude degree resolution, on a daily or monthly basis for the transportation, power generation, industry and residential sectors. The emission AFs are applied a global emissions inventory and the changes in emissions of the main pollutants are discussed for different regions of the world.
• Gaubert, B., I. Bouarar, T. Doumbia, Y. Liu, T. Stavrakou, A. Deroubaix, S. Darras, N. Elguindi, C. Granier, F. Lacey, J.-F. Müller, X. Shi, S. Tilmes, T. Wang, and G.P. Brasseur, Global changes in secondary atmospheric pollutants during the 2020 COVID-19 pandemic, Journal of Geophysical Research, doi:10.1029/2020JD034213, 2021. The reduction in the emissions of primary air pollutants during the 2020 COVID-19 pandemic has generated perturbations in the chemical state of the atmosphere. A global Earth system model that accounts for chemical, physical and dynamical processes in the atmosphere and for the coupling between the atmosphere, the ocean and the land surface, indicates that the abundance of tropospheric ozone was significantly reduced during the pandemic in response to reduced emissions of primary pollutants associated with restrictions of air traffic and economic activities. These findings are consistent with observed ozone anomalies during the summer of 2020. Read More
• Gkatzelis, G.I., J.B. Gilman, S.S. Brown, H. Eskes, A.R. Gomes, A.C. Lange, B. McDonald, J. Peischl, A. Petzold, C. Thompson, and A. Kiendler-Scharr, The global impacts of COVID-19 lockdowns on urban air pollution: A review, Elementa: Science of the Anthropocene, doi:10.1525/elementa.2021.00176, 2021. The COVID-19 pandemic was an unprecedented event in 2020 that led to lockdowns in an effort to control the spread of the virus. The resulting reduction in emissions of common air pollutants impacted air quality worldwide. This team reviewed more than 300 papers published on the subject since March 2020 and synthesized their results to summarize the state of the science on the COVID-19 air quality impacts. They also provide a critical review, with recommendations for best use of the data and further research needs, and developed the COVID-19 Air Quality Data Collection. Read More
• Harkins, C., B. C. McDonald, D. K. Henze, and C. Wiedinmyer, A fuel-based method for updating mobile source emissions during the COVID-19 pandemic, Environmental Research Letters, doi:10.1088/1748-9326/ac0660, 2021. Reductions in traffic have been observed globally around the world during the COVID-19 pandemic, and traffic remains an important source of ozone and aerosol precursors. As a response to the need to update emission inventories around the world, new mobility datasets such as from Apple and Google have been used to adjust traffic emission inventories. This study finds that such mobility datasets tend to overestimate the impact of COVID-19 on reduced US on-road nitrogen oxides emissions by a factor of ~2, when compared to fuel sales records and routine traffic monitoring data. Here we provide a comprehensive and gridded emissions inventory of carbon dioxide and all co-emitted air pollutants for mobile source engines under both business-as-usual and COVID-19 impacted scenarios. The sharpest reductions in mobile source emissions occurs in April, and by July the emissions are closer to pre-COVID-19 levels, though remain below normal. The Fuel-Based Inventory for Vehicle Emissions (FIVE) are available for use by the scientific and regulatory communities in studying the effects of COVID-19 on air quality, especially the role of vehicle electrification in the future.
• Kondragunta, S., Z. Wei, B.C. McDonald, D.L. Goldberg, and D.Q. Tong, COVID-19 induced fingerprints of a new normal urban air quality in the United States, Journal of Geophysical Research, doi:10.1029/2021JD034797, 2021. Restrictions on movement due to COVID-19 in the spring of 2020 led to reductions in nitrogen oxides (NOx) emissions from sudden drops in road traffic in U.S. cities nationwide. But even after restrictions were lifted and the flow of traffic resumed, NOx emissions from transportation remained around 20% lower than pre-COVID averages in some cities through the end of the year. Read More
• Liu, Y., T. Wang, T. Stavrakou, N. Elguindi, T. Doumbia, C. Granier, I. Bouarar, B. Gaubert, and G.P. Brasseur, Diverse response of surface ozone to COVID-19 lockdown in China, Science of the Total Environment, doi:10.1016/j.scitotenv.2021.147739, 2021. Ozone (O₃) is a key oxidant and pollutant in the lower atmosphere. Significant increases in surface O₃ have been reported in many cities during the COVID-19 lockdown. This study conducted comprehensive observation and modeling analyses of surface O₃ across China for periods before and during the lockdown, and found that daytime O₃ decreased in the subtropical south, in contrast to increases in most other regions. Meteorological changes and emission reductions both contributed to the O₃ changes, with a larger impact from the former especially in central China. The plunge in nitrogen oxide (NOx) emission contributed to O₃ increases in populated regions, whereas the reduction in volatile organic compounds (VOC) contributed to O₃ decreases across the country. This study highlights the complex dependence of O₃ on its precursors and the importance of meteorology in the short-term O₃ variability.
• Sokhi, R.S., V. Singh, X. Querol, S. Finardi, A.C. Targino, M. de Fatima Andrade, R. Pavlovic, R.M. Garland, J. Massagué, S. Kong, A. Baklanov, L. Ren, O. Tarasova, G. Carmichael, V.-H. Peuch, V. Anand, G. Arbilla, K. Badali, G. Beig, L.C. Belalcazar, A. Bolignano, P. Brimblecombe, P. Camacho, A. Casallas, J.-P. Charland, J. Choi, E. Chourdakis, I. Coll, M. Collins, J. Cyrys, C.M. da Silva, A.D. Di Giosa, A. Di Leo, C. Ferro, M. Gavidia-Calderon, A. Gayen, A. Ginzburg, F. Godefroy, Y.A. Gonzalez, M. Guevara-Luna, S.M. Haque, H. Havenga, D. Herod, U. Hörrak, T. Hussein, S. Ibarra, M. Jaimes, M. Kaasik, R. Khaiwal, J. Kim, A. Kousa, J. Kukkonen, M. Kulmala, J. Kuula, N. La Violette, G. Lanzani, X. Liu, S. MacDougall, P.M. Manseau, G. Marchegiani, B. McDonald, S.V. Mishra, L.T. Molina, D. Mooibroek, S. Mor, N. Moussiopoulos, F. Murena, J.V. Niemi, S. Noe, T. Nogueira, M. Norman, J.L. Pérez-Camaño, T. Petäjä, S. Piketh, A. Rathod, K. Reid, A. Retama, O. Rivera, N.Y. Rojas, J.P. Rojas-Quincho, R.S. José, O. Sánchez, R.J. Seguel, S. Sillanpää, Y. Su, N. Tapper, A. Terrazas, H. Timonen, D. Toscano, G. Tsegas, G.J.M. Velders, C. Vlachokostas, E. von Schneidemesser, R. Vpm, R. Yadav, R. Zalakeviciute, and M. Zavala, A global observational analysis to understand changes in air quality during exceptionally low anthropogenic emission conditions, Environment International, doi:10.1016/j.envint.2021.106818, 2021.
• Stavrakou, T., J.-F. Muüller, M. Bauwens, T. Doumbia, N. Elguindi, S. Darras, C. Granier, I. De Smedt, C. Lerot, M. Van Roozendael, B. Franco, L. Clarisse, C. Clerbaux, P.-F. Coheur, Y. Liu, T. Wang, X. Shi, B. Gaubert, S. Tilmes, and G. Brasseur, Atmospheric impacts of COVID-19 on NOx and VOC levels over China based on TROPOMI and IASI satellite data and modeling, Atmosphere, doi:10.3390/atmos12080946, 2021. China was the first country to undergo large-scale lockdowns in response to the pandemic in early 2020 and a progressive return to normalization after April 2020. Spaceborne observations of atmospheric nitrogen dioxide (NO₂) and oxygenated volatile organic compounds (OVOCs), including formaldehyde (HCHO), glyoxal (CHOCHO) and peroxyacetyl nitrate (PAN), reveal important changes over China in 2020, relative to 2019, in response to the pandemic-induced shutdown and the subsequent drop in pollutant emissions. Regional model simulations using anthropogenic emissions accounting for the reductions due to the pandemic explain to a large extent the observed changes in lockdown-affected regions. The model results suggest that meteorological variability accounts for a minor but non-negligible part of the observed changes for NO₂, whereas it is negligible for CHOCHO but plays a more substantial role for HCHO and PAN, especially in May. The interannual variability of biogenic and biomass burning emissions also contribute to the observed variations, explaining e.g. the important column increases of NO₂ and OVOCs in February 2020, relative to 2019. These changes are well captured by the model simulations.
• Steinbrecht, W., D. Kubistin, C. Plass‐Dülmer, J. Davies, D.W. Tarasick, P. von der Gathen, H. Deckelmann, N. Jepsen, R. Kivi, N. Lyall, M. Palm, J. Notholt, B. Kois, P. Oelsner, M. Allaart, A. Piters, M. Gill, R. Van Malderen, A.W. Delcloo, R. Sussmann, E. Mahieu, C. Servais, G. Romanens, R. Stübi, G. Ancellet, S. Godin‐Beekmann, S. Yamanouchi, K. Strong, B. Johnson, P. Cullis, I. Petropavlovskikh, J.W. Hannigan, J.L. Hernandez, A.D. Rodriguez, T. Nakano, F. Chouza, T. Leblanc, C. Torres, O. Garcia, A.N. Röhling, M. Schneider, T. Blumenstock, M. Tully, C. Paton‐Walsh, N. Jones, R. Querel, S. Strahan, R.M. Stauffer, A.M. Thompson, A. Inness, R. Engelen, K.L. Chang, and O.R. Cooper, COVID-19 crisis reduces free tropospheric ozone across the northern hemisphere, Geophysical Research Letters, doi:10.1029/2020GL091987, 2021. Worldwide actions to contain the COVID‐19 virus have closed factories, grounded airplanes, and have generally reduced travel and transportation. Less fuel was burnt, and less exhaust was emitted into the atmosphere. Due to these measures, the concentration of nitrogen oxides and volatile organic compounds (VOCs) decreased in the atmosphere. Read More