Preprints
https://doi.org/10.5194/egusphere-2025-1054
https://doi.org/10.5194/egusphere-2025-1054
01 Apr 2025
 | 01 Apr 2025

Tropospheric Ozone Assessment Report (TOAR): 16-year ozone trends from the IASI Climate Data Record

Anne Boynard, Catherine Wespes, Juliette Hadji-Lazaro, Selviga Sinnathamby, Daniel Hurtmans, Pierre-François Coheur, Marie Doutriaux-Boucher, Jacobus Onderwaater, Wolfgang Steinbrecht, Elyse A. Pennington, Kevin Bowman, and Cathy Clerbaux

Abstract. Assessing tropospheric ozone (O3) variability is essential for understanding its impact on air quality, health, and climate change. The Infrared (IR) Atmospheric Sounding Interferometer (IASI) mission onboard the Metop platforms, has been providing global measurements of O3 concentrations since 2007. This study presents the first comprehensive analysis of the 16-year O3 Climate Data Record (CDR) from IASI/Metop (2008–2023), a homogeneous dataset offering valuable insights into the variability and long-term trends of tropospheric O3. The IASI-CDR ozone product is evaluated against TROPESS (TRopospheric Ozone and its Precursors from Earth System Sounding) O3 retrievals from the Cross-track Infrared Sounder (CrIS). The comparison shows excellent agreement for total ozone (biases < 1.2 %, correlations > 0.97) and good agreement for tropospheric ozone (biases 10–12 %, correlations 0.77–0.91). Comparisons with ozonesonde data indicate that IASI underestimates tropospheric ozone by 2 % in the tropics and by up to 10 % in mid and high latitudes. Spatiotemporal analysis of IASI data from 2008 to 2023 reveals a global negative trend in tropospheric O3 (‑0.40 ± 0.10 % year-1), with the most pronounced decreases observed in the tropics and in Europe. Despite differing from positive trends in ultraviolet (UV) satellite data, both UV and IR satellite instruments show a significant drop in tropospheric ozone starting in 2020, partly due to pandemic-related emission reductions. This study emphasizes the importance of long-term, consistent datasets for tracking ozone trends and the need for improved data retrieval and integration to address regional and temporal discrepancies.

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Journal article(s) based on this preprint

01 Oct 2025
Assessment of 16-year tropospheric ozone trends from the IASI Climate Data Record
Anne Boynard, Catherine Wespes, Juliette Hadji-Lazaro, Selviga Sinnathamby, Daniel Hurtmans, Pierre-François Coheur, Marie Doutriaux-Boucher, Jacobus Onderwaater, Wolfgang Steinbrecht, Elyse A. Pennington, Kevin Bowman, and Cathy Clerbaux
Atmos. Chem. Phys., 25, 11719–11755, https://doi.org/10.5194/acp-25-11719-2025,https://doi.org/10.5194/acp-25-11719-2025, 2025
Short summary
Anne Boynard, Catherine Wespes, Juliette Hadji-Lazaro, Selviga Sinnathamby, Daniel Hurtmans, Pierre-François Coheur, Marie Doutriaux-Boucher, Jacobus Onderwaater, Wolfgang Steinbrecht, Elyse A. Pennington, Kevin Bowman, and Cathy Clerbaux

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2025-1054: TOAR-II guidelines', Martin Schultz, 10 Apr 2025
  • RC1: 'Comment on egusphere-2025-1054', Anonymous Referee #1, 05 May 2025
  • RC2: 'Comment on egusphere-2025-1054', Anonymous Referee #2, 09 May 2025
  • CC2: 'Comment on egusphere-2025-1054: HEGIFTOM perspective', Roeland Van Malderen, 13 May 2025
  • CC3: 'Comment on egusphere-2025-1054', Anne Thompson, 13 May 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2025-1054: TOAR-II guidelines', Martin Schultz, 10 Apr 2025
  • RC1: 'Comment on egusphere-2025-1054', Anonymous Referee #1, 05 May 2025
  • RC2: 'Comment on egusphere-2025-1054', Anonymous Referee #2, 09 May 2025
  • CC2: 'Comment on egusphere-2025-1054: HEGIFTOM perspective', Roeland Van Malderen, 13 May 2025
  • CC3: 'Comment on egusphere-2025-1054', Anne Thompson, 13 May 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Anne Boynard on behalf of the Authors (12 Jul 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (16 Jul 2025) by Jayanarayanan Kuttippurath
RR by Anonymous Referee #2 (23 Jul 2025)
ED: Publish as is (03 Aug 2025) by Jayanarayanan Kuttippurath
AR by Anne Boynard on behalf of the Authors (08 Aug 2025)

Journal article(s) based on this preprint

01 Oct 2025
Assessment of 16-year tropospheric ozone trends from the IASI Climate Data Record
Anne Boynard, Catherine Wespes, Juliette Hadji-Lazaro, Selviga Sinnathamby, Daniel Hurtmans, Pierre-François Coheur, Marie Doutriaux-Boucher, Jacobus Onderwaater, Wolfgang Steinbrecht, Elyse A. Pennington, Kevin Bowman, and Cathy Clerbaux
Atmos. Chem. Phys., 25, 11719–11755, https://doi.org/10.5194/acp-25-11719-2025,https://doi.org/10.5194/acp-25-11719-2025, 2025
Short summary
Anne Boynard, Catherine Wespes, Juliette Hadji-Lazaro, Selviga Sinnathamby, Daniel Hurtmans, Pierre-François Coheur, Marie Doutriaux-Boucher, Jacobus Onderwaater, Wolfgang Steinbrecht, Elyse A. Pennington, Kevin Bowman, and Cathy Clerbaux
Anne Boynard, Catherine Wespes, Juliette Hadji-Lazaro, Selviga Sinnathamby, Daniel Hurtmans, Pierre-François Coheur, Marie Doutriaux-Boucher, Jacobus Onderwaater, Wolfgang Steinbrecht, Elyse A. Pennington, Kevin Bowman, and Cathy Clerbaux

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Short summary
This study analyzes 16 years of global ozone data to assess its impact on air quality and climate. Using satellite measurements, we observed a global decrease in tropospheric ozone, particularly in tropical and European regions. The study highlights the importance of long-term data for tracking trends, especially during events like the pandemic. We emphasize the need for improved data processing and integrating multiple datasets to better understand ozone trends.
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