NASA Satellite Measurements Show Global‐Scale Reductions in Free Tropospheric Ozone in 2020 and Again in 2021 During COVID‐19

Abstract

In early 2020, soon after the beginning of the global COronaVIrus Disease 2019 (COVID-19) pandemic, extensive international efforts were taken in attempt to reduce the spread of the virus. These efforts included lockdowns and reduced activities of many private and public businesses, schools, and travel. A result was unprecedented decreases in Northern Hemisphere (NH) pollution including important ozone precursors nitrogen oxides (NO x = nitric oxide [NO] + nitrogen dioxide [NO 2 ]) and Volatile Organic Compounds (VOCs). The decreases in pollution and subsequent changes in tropospheric ozone, particularly in the NH, has led to a large number of published articles on this subject (e.g.,

Diverging Ozone Trends Above Western North America: Boundary Layer Decreases Versus Free Tropospheric Increases

“…The seasonal positive trends over 1995–2019 diminish after the 2020 data are included, but overall, the impact of the 2020 COVID‐19 economic downturn on tropospheric ozone trends is slight in SON above California and more pronounced in other seasons. When the 2021 data are included, the diminished trends persist in DJF and MAM, but there was a rebound of the positive trend in JJA (consistent with the findings from three NASA satellite products (Ziemke et al., 2022)). Above WNA Cooper et al.…”

“…When the 2021 data are included, the diminished trends persist in DJF and MAM, but there was a rebound of the positive trend in JJA (consistent with the findings from three NASA satellite products (Ziemke et al, 2022)).…”

“…(2021) and Ziemke et al. (2022) observed approximately 7% or 4 ppbv ozone reductions at multiple ozone monitoring sites within the 1–8 km column during April–August 2020. By integrating ozonesonde, lidar and commercial aircraft data, Chang et al.…”

“…Studies have shown a weak but consistent ozone drop in the mid-troposphere across the Northern Hemisphere in response to the emissions reduction in 2020 (Bouarar et al, 2021;Chang et al, 2022;Clark et al, 2021;Miyazaki et al, 2021;Steinbrecht et al, 2021). Specifically, Steinbrecht et al (2021) and Ziemke et al (2022) observed approximately 7% or 4 ppbv ozone reductions at multiple ozone monitoring sites within the 1-8 km column during April-August 2020. By integrating ozonesonde, lidar and commercial aircraft data, Chang et al (2022) quantified an overall free tropospheric ozone reduction of 3.6 [±1.8] ppbv above Europe and 2.8 [±1.9] ppbv above western North America (WNA) in 2020 with respect to 1994-2019.…”

The worldwide COVID-19 lockdown impacts on global secondary inorganic aerosols and radiative budget

“…The complex responses of secondary pollutants, including ozone and aerosols, to the reduced concentrations of NO 2 and other primary pollutants during the COVID-19 lockdown have been evaluated on the regional to global scales, taking advantages of the current observing systems and models (16)(17)(18)(19)(20). Nevertheless, technical challenges remain when inferring changes in anthropogenic emissions and their impacts related to the COVID-19 lockdowns.…”