Evaluation of stratospheric transport in three generations of Chemistry-Climate Models

Abstract. The representation of stratospheric transport in Chemistry-Climate Models (CCMs) is key for accurately reproducing and projecting the evolution of the ozone layer and other radiatively relevant trace gases. We evaluate stratospheric transport in CCMs that have participated in three model intercomparison initiatives (CCMVal-2, CCMI-1, and CCMI-2022) over the last ∼ 15 years using modern satellite datasets and reanalyses. Key long-standing model biases persist across generations, with some worsening in recent simulations. Transport remains overly fast in the models, with a global mean age of air young bias of ∼ 1 year for the CCMI-2022 median. It is argued that this bias could be associated with too fast tropical upwelling in the lower stratosphere and possibly to excessive vertical diffusion, with mixing biases being more uncertain. In the springtime southern polar stratosphere, the final warming is delayed (∼ 3 weeks), downwelling is underestimated (∼ 25 %), and the depth of the ozone minimum is overestimated (∼ 10 DU) on average in the most recent models. The tropopause is too high in all generations, and the tropical cold point tropopause is too warm in the latest generation (∼ 1–2 K). Long-term trends in transport over 1980–1999 are consistent across model generations and highlight the crucial role of ozone depletion in contributing to accelerate the Brewer-Dobson circulation and delaying the southern polar vortex breakdown.

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Journal
Atmospheric chemistry and physics
Published
2026-04-21
DOI
https://doi.org/10.5194/acp-26-5249-2026
Primary Topic
Atmospheric Ozone and Climate
Type
article
Field-Weighted Citation Impact
0.00

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article

Evaluation of stratospheric transport in three generations of Chemistry-Climate Models

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Evaluation of stratospheric transport in three generations of Chemistry-Climate Models

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article en

Abstract

Abstract. The representation of stratospheric transport in Chemistry-Climate Models (CCMs) is key for accurately reproducing and projecting the evolution of the ozone layer and other radiatively relevant trace gases. We evaluate stratospheric transport in CCMs that have participated in three model intercomparison initiatives (CCMVal-2, CCMI-1, and CCMI-2022) over the last ∼ 15 years using modern satellite datasets and reanalyses. Key long-standing model biases persist across generations, with some worsening in recent simulations. Transport remains overly fast in the models, with a global mean age of air young bias of ∼ 1 year for the CCMI-2022 median. It is argued that this bias could be associated with too fast tropical upwelling in the lower stratosphere and possibly to excessive vertical diffusion, with mixing biases being more uncertain. In the springtime southern polar stratosphere, the final warming is delayed (∼ 3 weeks), downwelling is underestimated (∼ 25 %), and the depth of the ozone minimum is overestimated (∼ 10 DU) on average in the most recent models. The tropopause is too high in all generations, and the tropical cold point tropopause is too warm in the latest generation (∼ 1–2 K). Long-term trends in transport over 1980–1999 are consistent across model generations and highlight the crucial role of ozone depletion in contributing to accelerate the Brewer-Dobson circulation and delaying the southern polar vortex breakdown.

Atmospheric chemistry and physicsVol. 26(8)
Karlsruhe Institute of Technology (DE), Universidad Complutense de Madrid (ES), Centre National de la Recherche Scientifique (FR), University of Leeds (GB), Japan Agency for Marine-Earth Science and Technology (JP), Jet Propulsion Laboratory (US), Environment and Climate Change Canada (CA), Johns Hopkins University (US), University of Wuppertal (DE), Forschungszentrum Jülich (DE), Deutscher Wetterdienst (DE), University of Toronto (CA), University of Canterbury (NZ), Université de Versailles Saint-Quentin-en-Yvelines (FR), Royal Belgian Institute for Space Aeronomy (BE), National Institute for Environmental Studies (JP), Tohoku University (JP), Aristotle University of Thessaloniki (GR), University of Cambridge (GB), Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR) (DE), Sorbonne Université (FR), Gentherm (United States) (US), National Centre for Atmospheric Science (GB), Météo-France (FR), Institut Pierre-Simon Laplace (FR), Physikalisch-Meteorologisches Observatorium Davos (CH), National Centre for Earth Observation (GB), NOAA Chemical Sciences Laboratory (US), National Research Council (LK), Laboratoire atmosphères, milieux, observations spatiales (FR), National Institute of Water and Atmospheric Research (NZ), Lancaster University (GB), University of Reading (GB), Ludwig-Maximilians-Universität München (DE)
Ministerio de Ciencia, Innovación y Universidades, European Space Agency, Ministry of Education, Culture, Sports, Science and Technology, Natural Environment Research Council, European Research Council, Agencia Estatal de Investigación, International Space Science Institute
Climate action
Openalex Percentile: Top 14%
Atmospheric Ozone and Climate
DOIOpen Access PDFOpenAlex
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