Preprints
https://doi.org/10.5194/gmd-2023-35
https://doi.org/10.5194/gmd-2023-35
Submitted as: development and technical paper
 | 
04 Apr 2023
Submitted as: development and technical paper |  | 04 Apr 2023
Status: this preprint is currently under review for the journal GMD.

Rapid assimilations of O3 observations – Part 1: methodology and tropospheric O3 changes in China in 2015–2020

Rui Zhu, Zhaojun Tang, Xiaokang Chen, Zhe Jiang, and Xiong Liu

Abstract. The high computational cost of chemical transport models (CTMs) is a potential bottleneck for the rapid assimilation of ozone (O3) observations. Here we developed a single tracer tagged-O3 mode to build the capability of the GEOS-Chem model for rapid simulation of tropospheric O3. The tagged-O3 mode demonstrates high consistency with GEOS-Chem full-chemistry simulation and dramatic reductions in computational costs by approximately 91–94 %. The tagged-O3 simulation was combined with China Ministry of Ecology and Environment (MEE) and Ozone Monitoring Instrument (OMI) O3 observations to investigate the changes in tropospheric O3 over E. Asia in 2015–2020. The assimilated O3 concentrations demonstrate good agreement with O3 observations: surface O3 concentrations are 42.9, 41.8 and 42.1 ppb; and tropospheric O3 columns are 37.1, 37.9 and 38.0 DU in the simulations, assimilations and observations, respectively. The assimilations indicate rapid increases in surface O3 by 1.60 (spring), 1.16 (summer), 1.47 (autumn) and 0.80 (winter) ppb yr-1 over E. China in 2015–2020, and the increasing trends are underestimated by the a priori simulations. More attention is thus suggested to the rapid increases in O3 pollution in spring and autumn. Furthermore, we find stronger increases in tropospheric O3 columns over highly polluted areas, which may reflect the larger contributions of local emissions. The large discrepancy in the trends in tropospheric O3 columns by assimilating surface and satellite observations further indicates the possible uncertainties in the derived free tropospheric O3 changes. The rapid O3 assimilation capability is a useful tool for the extension and interpretation of atmospheric O3 observations.

Rui Zhu et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2023-35', Anonymous Referee #1, 08 May 2023
  • RC2: 'Comment on gmd-2023-35', Anonymous Referee #2, 26 May 2023

Rui Zhu et al.

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Short summary
A single tracer tagged-O3 mode is developed to build the capability of GEOS-Chem model for rapid simulations of tropospheric O3. It is combined with OMI and surface O3 observations to investigate the changes in tropospheric O3 in China in 2015–2020. The assimilations indicate rapid surface O3 increases that are underestimated by the a priori simulations. We find stronger increases in tropospheric O3 columns over polluted areas and large discrepancy by assimilating different observations.