COVID‐19 Induced Fingerprints of a New Normal Urban Air Quality in the United States

Abstract

As the 2019 novel Corona virus (COVID-19) spread from China to other parts of the world, various countries imposed lockdown measures one by one. Reports of improved air quality from ground and satellite observations of aerosol optical depth (AOD) and nitrogen dioxide (NO 2 ) soon followed in the media as documented by Kondragunta et al. (2020). The precipitous drops seen in the tropospheric vertical column NO 2, (trop-NO 2 here onward) measured by the Sentinel 5P TROPOspheric Monitoring Instrument (TROPOMI) were substantial, especially during the strict lockdown period for each country (Gkatzelis et al., 2021). Goldberg et al. (2020) reported that in the United States (US), tropNO 2 decreased by 9.2%-45% in 26 cities from March 15 to April 30, 2020 compared to the same period in 2019; these reported reductions account for the influence of the weather. Other researchers reported similar findings, mainly reductions of tropNO 2 attributed to reductions in traffic emissions both in the US and across the globe in major urban areas of Europe, India,

NO2 retrievals from NOAA-20 OMPS: Algorithm, evaluation, and observations of drastic changes during COVID-19

“…Satellite observations show a drastic decline in tropospheric NO 2 vertical column density over China following the outbreak of COVID-19, reflecting reduced fossil fuel usage due to decreases in economic activity and restrictions on travel ( Huang and Sun, 2020 ; Liu et al, 2020 ). Similar declines have also been seen over Italy ( Bauwens et al, 2020 ), India ( ESA, 2020 ), North America ( Goldberg et al, 2020 ; Kondragunta et al, 2021 ; Tzortziou et al, 2021 ) as observed by the TROPOspheric Monitoring Instrument (TROPOMI) and the Ozone Monitoring Instrument (OMI). These satellite-based studies illustrate the importance of spaceborne observations for providing timely and continuous air quality monitoring.…”

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

“…Precursor emissions and ozone levels in 2020 were anomalous and it is too early to know if emissions will return to their pre‐pandemic levels (Kondragunta et al., 2021 ). Therefore we do not know if the positive ozone trends in the free troposphere above Europe and western North America since 1994 have stopped or if they will resume in the coming years.…”

“…The resulting COVID‐19 pandemic triggered a worldwide economic downturn in 2020 which reduced emissions of ozone precursor gases. These emissions reductions appeared to be related to a range of impacts on observed levels of ozone and particulate matter at the surface and in the free troposphere (Bauwens et al., 2020 ; Clark et al., 2021 ; Cooper et al., 2021 ; Cristofanelli et al., 2021 ; Gkatzelis et al., 2021 ; Keller et al., 2021 ; Kondragunta et al., 2021 ; Le et al., 2020 ; Liu et al., 2020 ; Shi & Brasseur, 2020 ; Sokhi et al., 2021 ; Steinbrecht et al., 2021 ). In general, surface observations from monitoring networks in many nations showed that urban areas with NOx‐limited regimes (e.g., Rio de Janeiro and South African urban areas) experienced ozone decreases, while urban areas with VOC‐limited regimes experienced ozone increases (e.g., urban areas in South Korea and Colombia; Sokhi et al., 2021 ).…”

COVID-19 and Beyond: COVID-19 Interventions and Power Plant Emissions in the United States

“…Concurrent with the lockdowns, air quality was reported to have improved in many parts of the United States, although air quality changes differed by location. U.S.-based studies have identified certain sourcesin particular, mobile sources and wildfiresthat contributed to air pollution variability during the lockdown period and post-lockdown period in 2020. ,− However, based on the existing literature on air quality responses to the COVID-19 lockdown (Table S1), it is unclear the extent to which EGU emissions were impacted by mobility and economic changes associated with COVID-19 public health interventions. Since stationary EGUs remain a major contributor to air pollution and greenhouse gas emissions in the United States and previous work has linked mobile emissions changes due to mobility patterns, policymakers will benefit from an understanding of how EGU emissions changed with and after pandemic-initiated shifts.…”