Submitted as: model description paper
30 Nov 2021
Submitted as: model description paper |  | 30 Nov 2021
Status: a revised version of this preprint is currently under review for the journal GMD.

Sensitivity of tropospheric ozone to halogen chemistry in the chemistry-climate model LMDZ-INCA vNMHC

Cyril Caram, Sophie Szopa, Anne Cozic, Slimane Bekki, Carlos Cuevas, and Alfonso Saiz-Lopez

Abstract. The atmospheric chemistry of halogenated species (Cl, Br, I) participates in the global chemical sink of tropospheric ozone and perturbs the oxidizing capacity of the troposphere, notably influencing the atmospheric lifetime of methane. Global chemistry-climate models are commonly used to assess the global budget of ozone, its sensitivity to emissions of its precursors, and to project its long-term evolution. Here, we report on the implementation of tropospheric halogens chemistry in the chemistry-climate model LMDZ-INCA and its effects on the tropospheric ozone budget. Overall, the results show that the model simulates satisfactorily the impact of halogens on the photooxidizing system in the troposphere, in particular in the marine boundary layer. To elucidate the mechanisms and quantify the effects, standard metrics representative of the behavior of the tropospheric chemical system (Ox, HOx, NOx, CH4, and NMVOCs) are computed with and without halogen chemistry. Tropospheric halogens in the LMDZ-INCA model lead to a decrease of 22 % in the ozone burden, 8 % in OH, and 33 % in NOx. Additional sensitivity simulations show that the inclusion of halogens chemistry makes ozone more sensitive to perturbations in CH4, NOx, and NMVOCs. Consistent with other global model studies, the sensitivity of the tropospheric ozone burden to changes from pre-industrial to present-day emissions is found to be ~20 % lower when tropospheric halogens are taken into account.

Cyril Caram et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CEC1: 'Comment on gmd-2021-388', Juan Antonio Añel, 30 Dec 2021
    • CC1: 'Reply on CEC1', Sophie Szopa, 04 Jan 2022
  • RC1: 'Comment on gmd-2021-388', Anonymous Referee #1, 10 Jan 2022
  • RC2: 'Comment on gmd-2021-388', Anonymous Referee #2, 13 Jan 2022

Cyril Caram et al.

Cyril Caram et al.


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Short summary
We studied the role of halogenated compounds (containing chlorine, bromine and iodine), emitted by natural processes (mainly above the oceans) on the chemistry of the lower layers of the atmosphere. We introduced this relatively new chemistry in a 3D climate-chemistry model, and looked at how this chemistry will disrupt the ozone. We showed that the concentration of ozone decreases by 22 % worldwide and that of the atmospheric detergent, OH, by 8 %.