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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Discussion papers | Copyright
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 29 May 2018

Research article | 29 May 2018

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This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Chemistry and Physics (ACP).

Monitoring Global Tropospheric OH Concentrations using Satellite Observations of Atmospheric Methane

Yuzhong Zhang1,2, Daniel J. Jacob1, Joannes D. Maasakkers1, Melissa P. Sulprizio1, Jian-Xiong Sheng1, Ritesh Gautam2, and John Worden3 Yuzhong Zhang et al.
  • 1School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
  • 2Environmental Defense Fund, USA
  • 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

Abstract. The hydroxyl radical (OH) is the main tropospheric oxidant and is the largest sink for atmospheric methane. The global abundance of OH has been monitored for the past decades with the methyl chloroform (CH3CCl3) proxy. This approach is becoming ineffective as atmospheric CH3CCl3 concentrations decline. Here we propose that satellite observations of atmospheric methane in the shortwave infrared (SWIR) and thermal infrared (TIR) can provide an effective replacement method. The premise is that the atmospheric signature of the methane sink from oxidation by OH is distinct from that of methane emissions. We evaluate this method in an observing system simulation experiment (OSSE) framework using synthetic SWIR and TIR satellite observations representative of the TROPOMI and CrIS instruments, respectively. The synthetic observations are interpreted with a Bayesian inverse analysis optimizing both gridded methane emissions and global OH concentrations with detailed error accounting, including errors in meteorological fields and in OH distributions. We find that the satellite observations can constrain the global tropospheric OH concentrations with a precision better than 1% and an accuracy of about 3% for SWIR and 7% for TIR. The inversion can successfully separate contributions from methane emissions and OH concentrations to the methane budget and its trend. We also show that satellite methane observations can constrain the interhemispheric difference in OH. The main limitation to the accuracy is uncertainty in the spatial and seasonal distribution of OH.

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Yuzhong Zhang et al.
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Short summary
We propose to use satellite observations of atmospheric methane to monitor global tropospheric OH concentration, a key parameter characterizing the oxidizing power of the atmosphere.
We propose to use satellite observations of atmospheric methane to monitor global tropospheric...