Contributions of World Regions to the Global Tropospheric Ozone Burden Change From 1980 to 2010

Abstract

Tropospheric ozone is recognized as the third most important contributor to the positive radiative forcing, based on its increases since 1750, following carbon dioxide (CO 2) and methane (CH 4 ; Myhre et al., 2013). Ozone is a secondary air pollutant, which is not emitted directly, but is produced through chemical reactions of precursor gases in the atmosphere, such as nitrogen oxides (NO x), carbon monoxide (CO), methane, and non-methane volatile organic compounds (NMVOCs). Ozone precursors are mainly emitted by human activities, such as fossil fuel combustion, residential burning, oil and gas production, agriculture, and biomass burning. Observations from aircraft, ozonesondes, and different satellites show that the tropospheric ozone burden has been increasing in the second half of the 20th century (Gaudel et al., 2018; Hemispheric Transport of Air Pollution [HTAP], 2010). Both satellite ozone measurements and global chemical transport models have found that the largest ozone burden increases-about +6 to +7 Dobson units (i.e., ∼15%-20% of average background ozone) from 1980 to 2016-are over India, Southeast Asia, and East Asia (Ziemke et al., 2019). Previous studies have demonstrated that methane emissions affect global ozone with little dependence on the location of emissions (Fiore et al., 2008). For short-lived ozone precursors, the global tropospheric ozone burden (B O3) responds differently to emission changes from different world regions, with generally

Global tropospheric ozone responses to reduced NO x emissions linked to the COVID-19 worldwide lockdowns

“…Increased surface ozone was seen in our estimates over parts of northern Europe, China, and South Africa, as has already been reported for northern China during the lockdown (10,21). Nevertheless, the obtained ozone production efficiency (OPE, mass of ozone produced per unit mass of NO x emitted) for the monthly mean tropospheric ozone burden (TOB, in TgO 3 unit, integrated from the surface to the tropopause globally) based on the regional emission changes was mostly positive throughout the analysis period (i.e., NO x emission declines reduced TOB), as seen in other modeling studies (39).…”

COVID‐19 Crisis Reduces Free Tropospheric Ozone Across the Northern Hemisphere

“…However, the chemical regime for ozone in the free troposphere is different (e.g., Kroll et al., 2020; Sillman, 1999; Thornton et al., 2002), and free tropospheric ozone reductions are expected after the substantial decrease of precursor emissions due to the COVID‐19 pandemic (e.g. Guevara et al., 2020; Zhang et al., 2020).…”

“…Archibald et al., 2020; Cooper et al., 2014; Gaudel et al., 2018). The Northern Hemisphere free troposphere is dominated by net photochemical ozone production, proportional (albeit nonlinearly) to the availability of ozone precursor gases (e.g., Zhang et al., 2020). In contrast to increases of surface ozone in polluted urban areas after the COVID‐19 emissions reductions, we find significant reductions of ozone in the northern extratropical free troposphere.…”

Did the COVID-19 Crisis Reduce Free Tropospheric Ozone across the Northern Hemisphere?

“…Archibald et al, 2020;Cooper et al, 2014;Gaudel et al, 2018). The Northern Hemisphere free troposphere is dominated by net photochemical ozone production, proportional (albeit nonlinearly) to the availability of ozone precursor gases (e.g., Zhang et al, 2020).…”