Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 5.668 IF 5.668
  • IF 5-year value: 6.201 IF 5-year
    6.201
  • CiteScore value: 6.13 CiteScore
    6.13
  • SNIP value: 1.633 SNIP 1.633
  • IPP value: 5.91 IPP 5.91
  • SJR value: 2.938 SJR 2.938
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 174 Scimago H
    index 174
  • h5-index value: 87 h5-index 87
Discussion papers
https://doi.org/10.5194/acp-2019-925
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2019-925
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 06 Nov 2019

Submitted as: research article | 06 Nov 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).

Impact of atomic chlorine on the modelling of total methane and its 13C : 12C isotopic ratio at global scale

Joël Thanwerdas1, Marielle Saunois1, Antoine Berchet1, Isabelle Pison1, Didier Hauglustaine1, Michel Ramonet1, Cyril Crevoisier2, Bianca Baier3,4, Colm Sweeney4, and Philippe Bousquet1 Joël Thanwerdas et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, IPSL, Gif-sur-Yvette, France
  • 2Laboratoire de Météorologie Dynamique, École Polytechnique, IPSL, Palaiseau, France
  • 3Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado-Boulder, Boulder, CO, USA 80305
  • 4NOAA Earth System Research Laboratory Global Monitoring Division, Boulder, CO, USA 80305

Abstract. Methane (CH4) is the second strongest anthropogenic greenhouse gas after carbon dioxide (CO2) and is responsible for about 20 % of the warming induced by long-lived greenhouse gases since pre-industrial times. Oxidation by the hydroxyl radical (OH) is the dominant atmospheric sink for methane, contributing to approximately 90 % of the total methane loss. Chemical losses by reaction with atomic oxygen (O1D) and chlorine radicals (Cl) in the stratosphere are other sinks, contributing about 3 % to the total methane destruction. Moreover, the reaction with Cl is very fractionating, thus it has a much larger impact on δ13C-CH4 than the reaction with OH. In this paper, we assess the impact of atomic Cl on atmospheric methane mixing ratios, methane atmospheric loss and atmospheric δ13C-CH4. The offline version of the Global Circulation Model (GCM) LMDz, coupled to a chemistry module including the major methane chemical reactions, is run to simulate CH4 concentrations and δ13C-CH4 at the global scale. Atmospheric methane sink by Cl atoms in the stratosphere is found to be 7.32 ± 0.16 Tg/yr. Methane observations from vertical profiles obtained using AirCore samplers above 11 different locations across the globe and balloon measurements of δ13C-CH4 and methane are used to assess the impact of the Cl sink in the chemistry transport model. Above 10 km, the presence of Cl in the model is found to have only a small impact on the vertical profile of total methane but a major influence on δ13C-CH4 values, significantly improving the agreement between simulations and available observations. Stratospheric Cl is also found to have a substantial impact on surface δ13C-CH4 values, leading to a difference of +0.27 ‰ (less negative values) after a 19-year run. As a result, this study suggests that the Cl sink needs to be properly taken into account (magnitude and trends) in order to better understand trends in the atmospheric δ13C-CH4 signal when using atmospheric chemistry transport models for forward or inverse calculations.

Joël Thanwerdas et al.
Interactive discussion
Status: open (until 01 Jan 2020)
Status: open (until 01 Jan 2020)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement
Joël Thanwerdas et al.
Joël Thanwerdas et al.
Viewed  
Total article views: 150 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
109 40 1 150 11 2 0
  • HTML: 109
  • PDF: 40
  • XML: 1
  • Total: 150
  • Supplement: 11
  • BibTeX: 2
  • EndNote: 0
Views and downloads (calculated since 06 Nov 2019)
Cumulative views and downloads (calculated since 06 Nov 2019)
Viewed (geographical distribution)  
Total article views: 98 (including HTML, PDF, and XML) Thereof 98 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Cited  
Saved  
No saved metrics found.
Discussed  
No discussed metrics found.
Latest update: 11 Nov 2019
Publications Copernicus
Download
Short summary
Oxidation by the hydroxyl radical (OH) is the dominant atmospheric sink for methane, contributing to approximately 90 % of the total methane loss. Chemical losses by reaction with atomic oxygen (O1D) and chlorine radicals (Cl) in the stratosphere are other sinks, contributing about 3 % to the total methane destruction. We assess here the impact of atomic Cl on atmospheric methane mixing ratios, methane atmospheric loss and atmospheric isotopic δ13C-CH4 values.
Oxidation by the hydroxyl radical (OH) is the dominant atmospheric sink for methane,...
Citation