Tropospheric Ozone Assessment Report II: South America regional analysis

This study presents the first regional assessment of tropospheric ozone over South America for the early twenty-first century. We use observations from 14 combined satellite records, two atmospheric reanalyses, and model simulations to examine the spatial distribution, source contributions and trends in ozone and its precursors. Satellites and reanalysis data reveal enhanced tropospheric column ozone over the mid-latitudes of the west coast and the subtropical east coast, with 2005-2021 median values (±2σ) ranging from 46 [±11] to 49 [±9] nmol mol-1. By contrast, the lowest ozone levels occur over the northwest (39 [±8]-42 [±8] nmol mol-1) and the southern cone (38 [±11]-40 [±7] nmol mol-1). Tropospheric column ozone trends (±2σ) differ across South America (2005-2021), reflecting substantial subregional and partial column variability. Satellite observations suggest an overall negative trend (low certainty), whereas reanalyses show positive trends with high certainty, ranging from +0.55 [±0.85] to +0.85 [±0.70] nmol mol-1 decade-1. Model simulations identify global background methane as the dominant contributor to the South American tropospheric ozone burden, accounting for 41% (17 of 42 nmol mol-1), followed by global anthropogenically emitted nitrogen oxides (31%). These findings improve our understanding of chemical processes and provide valuable inputs for assessing air quality and climate impacts. This article is part of the theme issue 'Tropospheric Ozone Assessment Report II'.

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Journal
Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences
Published
2026-10-26
DOI
https://doi.org/10.1098/rsta.2025.0273
Primary Topic
Atmospheric chemistry and aerosols
Type
article
Field-Weighted Citation Impact
0.00

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article

Tropospheric Ozone Assessment Report II: South America regional analysis

Pablo Lichtig, Tim Butler, Viktoria Sofieva, Charlie Opazo et al.
Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences
Atmospheric chemistry and aerosols
article

Tropospheric Ozone Assessment Report II: South America regional analysis

Pablo Lichtig, Tim Butler, Viktoria Sofieva, Charlie Opazo, Lucas Castillo, H. M. Worden, Kazuyuki Miyazaki, Tabish Umar Ansari, Daan Hubert, Rodrigo Seguel, Gaëlle Dufour
article en

Abstract

This study presents the first regional assessment of tropospheric ozone over South America for the early twenty-first century. We use observations from 14 combined satellite records, two atmospheric reanalyses, and model simulations to examine the spatial distribution, source contributions and trends in ozone and its precursors. Satellites and reanalysis data reveal enhanced tropospheric column ozone over the mid-latitudes of the west coast and the subtropical east coast, with 2005-2021 median values (±2σ) ranging from 46 [±11] to 49 [±9] nmol mol-1. By contrast, the lowest ozone levels occur over the northwest (39 [±8]-42 [±8] nmol mol-1) and the southern cone (38 [±11]-40 [±7] nmol mol-1). Tropospheric column ozone trends (±2σ) differ across South America (2005-2021), reflecting substantial subregional and partial column variability. Satellite observations suggest an overall negative trend (low certainty), whereas reanalyses show positive trends with high certainty, ranging from +0.55 [±0.85] to +0.85 [±0.70] nmol mol-1 decade-1. Model simulations identify global background methane as the dominant contributor to the South American tropospheric ozone burden, accounting for 41% (17 of 42 nmol mol-1), followed by global anthropogenically emitted nitrogen oxides (31%). These findings improve our understanding of chemical processes and provide valuable inputs for assessing air quality and climate impacts. This article is part of the theme issue 'Tropospheric Ozone Assessment Report II'.

Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering SciencesVol. 384(2332)
NSF National Center for Atmospheric Research (US), California Institute of Technology (US), Finnish Meteorological Institute (FI), Centre National de la Recherche Scientifique (FR), Jet Propulsion Laboratory (US), University of California, Los Angeles (US), Pontificia Universidad Católica de Chile (CL), Université Paris-Est Créteil (FR), Royal Belgian Institute for Space Aeronomy (BE), Université Paris Cité (FR), Centre For Sustainable Urban Development (CL), Research Institute for Sustainability at GFZ (DE), Laboratoire Interuniversitaire des Systèmes Atmosphériques (FR), Center for Climate and Resilience Research (CL), GFZ Helmholtz Centre for Geosciences (DE), NSF NCAR Atmospheric Chemistry Observations & Modeling (US), Freie Universität Berlin (DE), Comisión Nacional de Energía Atómica (AR)
National Science Foundation, National Aeronautics and Space Administration, European Space Agency, Agencia Nacional de Investigación y Desarrollo
Openalex Percentile: Top 21%
Atmospheric chemistry and aerosols
DOIOpen Access PDFOpenAlex
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