Publication Date:
2016-03-11
Description:
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 through the photo-dissociation 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, and show that S is larger than previously assumed. MOM calculates substantially higher OH reactivity from VOC oxidation compared to predecessor models. Further, we find that nighttime OH formation may be significant in the polluted subtropical boundary layer in summer. Globally S exceeds P, most distinctively in the free troposphere. As a consequence, OH is buffered and not sensitive to perturbations by natural or anthropogenic emission changes. Complementary OH formation mechanisms in pristine and polluted environments of the continental and marine troposphere, connected through long-range transport of O3, maintain stable global OH levels.
Electronic ISSN:
1680-7375
Topics:
Geosciences
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