Global tropospheric hydroxyl distribution, budget and reactivity.

Lelieveld, Jos, Gromov, Sergey, Pozzer, Andrea and Taraborrelli, Domenico (2016) Global tropospheric hydroxyl distribution, budget and reactivity. Open Access Atmospheric Chemistry and Physics, 16 (19). pp. 12477-12493. DOI 10.5194/acp-16-12477-2016.

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Supplementary data:


The self-cleaning or oxidation capacity of the atmosphere is principally controlled by hydroxyl (OH) radicals in the troposphere. Hydroxyl has primary (P) and secondary (S) sources, the former mainly through the photodissociation of ozone, the latter through OH recycling in radical reaction chains. We used the recent Mainz Organics Mechanism (MOM) to advance volatile organic carbon (VOC) chemistry in the general circulation model EMAC (ECHAM/MESSy Atmospheric Chemistry) and show that S is larger than previously assumed. By including emissions of a large number of primary VOC, and accounting for their complete breakdown and intermediate products, MOM is mass-conserving and calculates substantially higher OH reactivity from VOC oxidation compared to predecessor models. Whereas previously P and S were found to be of similar magnitude, the present work indicates that S may be twice as large, mostly due to OH recycling in the free troposphere. Further, we find that nighttime OH formation may be significant in the polluted subtropical boundary layer in summer. With a mean OH recycling probability of about 67%, global OH is buffered and not sensitive to perturbations by natural or anthropogenic emission changes. Complementary primary and secondary OH formation mechanisms in pristine and polluted environments in the continental and marine troposphere, connected through long-range transport of O3, can maintain stable global OH levels.

Document Type: Article
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/acp-16-12477-2016
ISSN: 1680-7316
Projects: PalMod
Date Deposited: 12 Sep 2018 07:21
Last Modified: 01 Feb 2019 15:16

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