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Resolving the model-observation discrepancy in the mesospheric and stratospheric HO_x chemistry

Li, King-Fai and Zhang, Qiong and Wang, Shuhui and Sander, Stanley P. and Yung, Yuk L. (2017) Resolving the model-observation discrepancy in the mesospheric and stratospheric HO_x chemistry. Earth and Space Science, 4 (9). pp. 607-624. ISSN 2333-5084. https://resolver.caltech.edu/CaltechAUTHORS:20170905-074402925

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Abstract

We examine the middle atmospheric odd-hydrogen (HO_x) chemistry by comparing the Aura Microwave Limb Sounder (MLS) OH and HO_2 measurements with a photochemical model simulation. The model underestimates mesospheric OH and HO_2 concentrations if the standard chemical kinetic rates are used, whether the model H_2O and O_3 are constrained with observations or not. To resolve the discrepancies, we adjust the kinetic rate coefficients of three key reactions (O + OH → O_2 + H, OH + HO_2 → H_2O + O_2, and H + O_2 + M → HO_2 + M) and the O2photo absorption cross section at Lyman-α (121.57 nm) using the Bayesian optimal estimation. A much better model-observation agreement can be achieved if the kinetic rate coefficients for H + O_2 + M → HO_2 + M is increased by 134–310%, and the O_2 photo absorption cross section at Lyman-α is reduced by 33–54%, while the kinetic rate coefficients for O + OH → O_2 + H and OH + HO_2 → H_2O + O_2 remain consistent with the current laboratory values. The kinetic rate coefficient for H + O_2 + M → HO_2 + M requires a very large adjustment beyond the uncertainty limits recommended in the NASA Data Evaluation, suggesting the need for future laboratory measurements. An alternative explanation is that the radiative association reaction, H + O_2 → HO_2 + hν, plays a significant role, which has never been measured. Our results demonstrate that high quality satellite observations can be used to constrain photochemical parameters and help improve our understanding of atmospheric chemistry.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1002/2017EA000283DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/2017EA000283/abstractPublisherArticle
ORCID:
AuthorORCID
Li, King-Fai0000-0003-0150-2910
Zhang, Qiong0000-0002-8762-0557
Sander, Stanley P.0000-0003-1424-3620
Yung, Yuk L.0000-0002-4263-2562
Additional Information:© 2017 American Geophysical Union. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Received 12 APR 2017; Accepted 28 AUG 2017; Accepted article online 4 SEP 2017; Published online 27 SEP 2017. We thank P. Wennberg, R. -L. Shia, S. Newman, and P. Kopparla for helpful comments. We acknowledge the support of the NASA Aura Science Team. S. W., Q. Z., and Y. L. Y. acknowledge partial support by NASA's LWS Program grant NNX16AK63G. K. F. L. was supported partly by the Jack Eddy Fellowship managed by the University Corporation for Atmospheric Research and partly by the NASA grant NNX14AR40G. We thank the two anonymous reviewers, whose comments significantly improved this manuscript. Additional support was provided by the NASA Upper Atmosphere Research and Tropospheric Chemistry Programs. MLS data are available at https://mls.jpl.nasa.gov/products/oh_product.php.
Group:Astronomy Department
Funders:
Funding AgencyGrant Number
NASANNX16AK63G
University Corporation for Atmospheric ResearchUNSPECIFIED
NASANNX14AR40G
Issue or Number:9
Record Number:CaltechAUTHORS:20170905-074402925
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170905-074402925
Official Citation:Li, K.-F., Zhang, Q., Wang, S., Sander, S. P., & Yung, Y. L. (2017). Resolving the model-observation discrepancy in the mesospheric and stratospheric HOx chemistry. Earth and Space Science, 4, 607–624. https://doi.org/10.1002/2017EA000283
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81117
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:05 Sep 2017 19:44
Last Modified:20 Apr 2020 08:47

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