Preprints
https://doi.org/10.5194/acp-2021-476
https://doi.org/10.5194/acp-2021-476

  05 Jul 2021

05 Jul 2021

Review status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Recent ozone trends in the Chinese free troposphere: role of the local emission reductions and meteorology

Gaëlle Dufour1, Didier Hauglustaine2, Yunjiang Zhang2,a, Maxim Eremenko3, Yann Cohen2, Audrey Gaudel4, Guillaume Siour3, Mathieu Lachatre5,b, Axel Bense3, Bertrand Bessagnet6,c, Juan Cuesta3, Jerry Ziemke7, Valérie Thouret8, and Bo Zheng9 Gaëlle Dufour et al.
  • 1Université de Paris and Univ Paris Est Creteil, CNRS, LISA, F-75013 Paris, France
  • 2Laboratoire des Sciences du Climat et de l’Environnement (LSCE), UMR 8212, CEA-CNRS-UVSQ, Gif-sur-Yvette, France
  • 3Univ Paris Est Creteil and Université de Paris, CNRS, LISA, F-94010 Créteil, France
  • 4CIRES, University of Colorado/NOAA Chemical Sciences Laboratory, Boulder, CO, USA
  • 5LMD/IPSL, École Polytechnique, Institut Polytechnique de Paris, ENS, PSL Université, Sorbonne Université, CNRS, Palaiseau, France
  • 6Ecole Polytechnique, Institut Polytechnique de Paris, ENS, PSL Universite, Sorbonne Universite, CNRS, 91128 Palaiseau, France
  • 7NASA Goddard Space Flight Center, and Goddard Earth Sciences Technology and Research (GESTAR), Maryland, USA
  • 8Laboratoire d’Aérologie, Université de Toulouse, CNRS, UPS, France
  • 9Institute of Environment and Ecology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China
  • anow at: School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China
  • bnow at: ARIA Technologies 8-10 rue de la Ferme 92100 Boulogne-Billancourt, France
  • cnow at: European Commission, Joint Research Centre (JRC), Ispra, Italy

Abstract. Free tropospheric ozone (O3) trends in the Central East China (CEC) and export regions are investigated for 2008–2017 using the IASI O3 observations and the LMDZ-OR-INCA model simulations, including the most recent Chinese emission inventory. The observed and modeled trends in the CEC region are −0.07 ± 0.02 DU/yr and −0.08 ± 0.02 DU/yr respectively for the lower free troposphere (3–6 km column), and −0.05 ± 0.02 DU/yr and −0.06 ± 0.02 DU/yr respectively for the upper free troposphere (6–9 km column). The statistical p-value is smaller to 0.01 for all the derived trends. A good agreement between the observations and the model is also observed in the region including Korea and Japan and corresponding to the region of pollution export from China. Based on sensitivity studies conducted with the model, we evaluate at 60 % and 52 % the contribution of the Chinese anthropogenic emissions to the trend in the lower and upper free troposphere, respectively. The second main contribution to the trend is the meteorological variability (34 % and 50 % respectively). These results suggest that the reduction of NOx anthropogenic emissions that occurred since 2013 in China lead to a decrease in ozone in the Chinese free troposphere, contrary to the increase in ozone at the surface. We designed some tests to compare the trends derived by the IASI observations and the model to independent measurements such as IAGOS or other satellite measurements (OMI/MLS). These comparisons do not confirm the O3 decrease and stress the difficulty to analyze short-term trends using multiple datasets with various sampling and the risk to overinterpret the results.

Gaëlle Dufour et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-476', Anonymous Referee #1, 28 Jul 2021
    • AC1: 'Reply on RC1', Gaëlle Dufour, 23 Sep 2021
  • RC2: 'Comment on acp-2021-476', Anonymous Referee #2, 09 Aug 2021
    • AC1: 'Reply on RC1', Gaëlle Dufour, 23 Sep 2021

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-476', Anonymous Referee #1, 28 Jul 2021
    • AC1: 'Reply on RC1', Gaëlle Dufour, 23 Sep 2021
  • RC2: 'Comment on acp-2021-476', Anonymous Referee #2, 09 Aug 2021
    • AC1: 'Reply on RC1', Gaëlle Dufour, 23 Sep 2021

Gaëlle Dufour et al.

Gaëlle Dufour et al.

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Short summary
The IASI observations and the LMDZ-OR-INCA model simulations show negative ozone trends in the Central East China region in the lower free (3–6 km column) and the upper free (6–9 km column) troposphere. Sensitivity studies from the model show that the Chinese anthropogenic emissions contribute to more than 50 % in the trend. The reduction of NOx emissions that occurred since 2013 in China seems to lead to a decrease in ozone in the free troposphere, contrary to the increase at the surface.
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