Tropical tropospheric ozone trends (1998 to 2023): new perspectives from SHADOZ, IAGOS and OMI/MLS observations

Abstract. Tropospheric ozone trends are important indicators of climate forcing and surface pollution, yet relevant satellite observations are too uncertain for assessments. The assessment project TOAR-II has used multi-instrument, ground-based data for global trends over 2000–2022 (Van Malderen et al., 2025a, b). For the tropics, trends are derived from SHADOZ ozonesonde profiles (Thompson et al., 2021, “T21”; Stauffer et al., 2024) or combinations of satellite, SHADOZ and IAGOS aircraft measurements (Gaudel et al., 2024). We extend T21 that covered 1998–2019, analyzing SHADOZ data at five sites with a Multiple Linear Regression (MLR) model for 1998–2023 and reporting trends for two free-tropospheric (FT) segments, the lowermost stratosphere and the total tropospheric column (TrCOsonde). Trends for the Aura period, 2005–2023, are computed from OMI/MLS TrCOsatellite. We find the following: Extending SHADOZ analyses 4 years shows little change from T21; TrCOsonde trends are small (0.5–1 DU/decade) except over SE Asia. Annual trends for TrCOsonde and OMI/MLS TrCOsatellite agree within uncertainties at four of five sites, with the largest differences at Samoa. Sensitivity tests show the following: (a) Adding thousands of FT IAGOS profiles to SHADOZ yields little change in trends; SHADOZ sampling is sufficient. (b) Quantile Regression (QR) and MLR median trends are both near zero, but QR captures extremes (5th percentile, 95th percentile) with changes up to ±1 DU/decade (p< 0.10). (c) Twelve-year analyses for trends lead to uncertainty changes too large for an assessment. This study and Van Malderen et al. (2025a, b) provide the most reliable TOAR-II trends to date: over the past ∼ 25 years, tropical FT ozone changes have been modest, ∼ (−3–+3) %/decade, except over SE Asia.

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Journal
Atmospheric chemistry and physics
Published
2025-12-19
DOI
https://doi.org/10.5194/acp-25-18475-2025
Primary Topic
Atmospheric Ozone and Climate
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article
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article

Tropical tropospheric ozone trends (1998 to 2023): new perspectives from SHADOZ, IAGOS and OMI/MLS observations

Stéphanie Evan, M. Cazorla, Thumeka Mkololo, Ankie Piters et al.
Atmospheric chemistry and physics
Atmospheric Ozone and Climate
article

Tropical tropospheric ozone trends (1998 to 2023): new perspectives from SHADOZ, IAGOS and OMI/MLS observations

Stéphanie Evan, M. Cazorla, Thumeka Mkololo, Ankie Piters, Christian Félix, B. J. Johnson, Katrin Müller, Pamela K. Benjamin, Patrick Cullis, Bastien Sauvage, Matthew Martinsen, J. R. Ziemke, Anne M. Thompson, Francisco R. da Silva, Darryl Kuniyuki, J. A. Diaz, Gary A. Morris, Shin‐Ya Ogino, J. Brioude, Ninong Komala, Francis S. Mani, Debra E. Kollonige, E. T. Northam, Ambun Dindang, Paweł Wolff, Jean‐Marc Metzger, Ryan M. Stauffer, Mohan Kumar Sammathuria, Gonzague Romanens, Tshidi Machinini, Norazura Binti Zakaria, David Nardini, Igor Nedeljkovic, Truus Warsodikromo, Syprose Nyadida, Yuzaimi B. Mahat, Nguyen Thi Quyen, Miriama Vuiyasawa
article en

Abstract

Abstract. Tropospheric ozone trends are important indicators of climate forcing and surface pollution, yet relevant satellite observations are too uncertain for assessments. The assessment project TOAR-II has used multi-instrument, ground-based data for global trends over 2000–2022 (Van Malderen et al., 2025a, b). For the tropics, trends are derived from SHADOZ ozonesonde profiles (Thompson et al., 2021, “T21”; Stauffer et al., 2024) or combinations of satellite, SHADOZ and IAGOS aircraft measurements (Gaudel et al., 2024). We extend T21 that covered 1998–2019, analyzing SHADOZ data at five sites with a Multiple Linear Regression (MLR) model for 1998–2023 and reporting trends for two free-tropospheric (FT) segments, the lowermost stratosphere and the total tropospheric column (TrCOsonde). Trends for the Aura period, 2005–2023, are computed from OMI/MLS TrCOsatellite. We find the following: Extending SHADOZ analyses 4 years shows little change from T21; TrCOsonde trends are small (0.5–1 DU/decade) except over SE Asia. Annual trends for TrCOsonde and OMI/MLS TrCOsatellite agree within uncertainties at four of five sites, with the largest differences at Samoa. Sensitivity tests show the following: (a) Adding thousands of FT IAGOS profiles to SHADOZ yields little change in trends; SHADOZ sampling is sufficient. (b) Quantile Regression (QR) and MLR median trends are both near zero, but QR captures extremes (5th percentile, 95th percentile) with changes up to ±1 DU/decade (p< 0.10). (c) Twelve-year analyses for trends lead to uncertainty changes too large for an assessment. This study and Van Malderen et al. (2025a, b) provide the most reliable TOAR-II trends to date: over the past ∼ 25 years, tropical FT ozone changes have been modest, ∼ (−3–+3) %/decade, except over SE Asia.

Atmospheric chemistry and physicsVol. 25(24)
University of Hawaiʻi at Mānoa (US), Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung (DE), American Meteorological Society (US), Goddard Space Flight Center (US), National Oceanic and Atmospheric Administration (US), Royal Netherlands Meteorological Institute (NL), Japan Agency for Marine-Earth Science and Technology (JP), Federal Office of Meteorology and Climatology MeteoSwiss (CH), Université Toulouse III - Paul Sabatier (FR), University of Bonn (DE), Kenya Wildlife Service (KE), University of Colorado Boulder (US), Patrick Air Force Base (US), South African Weather Service (ZA), Universidad de Costa Rica (CR), Laboratoire d'Aérologie (FR), Observatoire Midi-Pyrénées (FR), Laboratoire de l'Atmosphère et des Cyclones (RE), Science Systems and Applications (United States) (US), National Research and Innovation Agency (ID), University of the South Pacific (FJ), Universidad San Francisco de Quito (EC), University of Maryland, Baltimore County (US), NOAA Earth System Research Laboratory (US), Morgan State University (US)
Openalex Percentile: Top 55%
Atmospheric Ozone and Climate
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