Deriving Global OH Abundance and Atmospheric Lifetimes for Long-Lived Gases: A Search for CH
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Liang_et_al_2017_Journal_of_Geophysical_Research_Atmospheres.pdf
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Author(s)
Liang, Qing
Chipperfield, Martyn P.
Fleming, Eric L.
Abraham, N. Luke
Braesicke, Peter
Burkholder, James B.
Daniel, John S.
Dhomse, Sandip
Fraser, Paul J.
Hardiman, Steven C.
Date Issued
December 2017
Journal
Journal of Geophysical Research: Atmospheres
Publisher
American Geophysical Union (AGU)
Citation
Liang, Qing et al. “Deriving Global OH Abundance and Atmospheric Lifetimes for Long-Lived Gases: A Search for CH₃CCl₃ Alternatives.” Journal of Geophysical Research: Atmospheres 122, 21 (November 2017): 11,914–11,933 © 2017 American Geophysical Union
Version
Final published version
Abstract
An accurate estimate of global hydroxyl radical (OH) abundance is important for projections of air quality, climate, and stratospheric ozone recovery. As the atmospheric mixing ratios of methyl chloroform (CH₃CCl₃) (MCF), the commonly used OH reference gas, approaches zero, it is important to find alternative approaches to infer atmospheric OH abundance and variability. The lack of global bottom-up emission inventories is the primary obstacle in choosing a MCF alternative. We illustrate that global emissions of long-lived trace gases can be inferred from their observed mixing ratio differences between the Northern Hemisphere (NH) and Southern Hemisphere (SH), given realistic estimates of their NH-SH exchange time, the emission partitioning between the two hemispheres, and the NH versus SH OH abundance ratio. Using the observed long-term trend and emissions derived from the measured hemispheric gradient, the combination of HFC-32 (CH₂F₂), HFC-134a (CH₂FCF₃, HFC-152a (CH₃CHF₂), and HCFC-22 (CHClF₂), instead of a single gas, will be useful as a MCF alternative to infer global and hemispheric OH abundance and trace gas lifetimes. The primary assumption on which this multispecies approach relies is that the OH lifetimes can be estimated by scaling the thermal reaction rates of a reference gas at 272 K on global and hemispheric scales. Thus, the derived hemispheric and global OH estimates are forced to reconcile the observed trends and gradient for all four compounds simultaneously. However, currently, observations of these gases from the surface networks do not provide more accurate OH abundance estimate than that from MCF. Keywords: hydroxyl; CH₃CCl₃; lifetime; OH
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1002/2017JD026926
