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@ARTICLE{Rosanka:902281,
author = {Rosanka, Simon and Sander, Rolf and Franco, Bruno and
Wespes, Catherine and Wahner, Andreas and Taraborrelli,
Domenico},
title = {{O}xidation of low-molecular-weight organic compounds in
cloud droplets: global impact on tropospheric oxidants},
journal = {Atmospheric chemistry and physics},
volume = {21},
number = {12},
issn = {1680-7324},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {FZJ-2021-04144},
pages = {9909 - 9930},
year = {2021},
abstract = {In liquid cloud droplets, superoxide anion (O−2(aq)) is
known to quickly consume ozone (O3(aq)), which is relatively
insoluble. The significance of this reaction as a
tropospheric O3 sink is sensitive to the abundance of
O−2(aq) and therefore to the production of its main
precursor, the hydroperoxyl radical (HO2(aq)). The
aqueous-phase oxidation of oxygenated volatile organic
compounds (OVOCs) is the major source of HO2(aq) in cloud
droplets. Hence, the lack of explicit aqueous-phase chemical
kinetics in global atmospheric models leads to a general
underestimation of clouds as O3 sinks. In this study, the
importance of in-cloud OVOC oxidation for tropospheric
composition is assessed by using the Chemistry As A Boxmodel
Application (CAABA) and the global ECHAM/MESSy Atmospheric
Chemistry (EMAC) model, which are both capable of explicitly
representing the relevant chemical transformations. For this
analysis, three different in-cloud oxidation mechanisms are
employed: (1) one including the basic oxidation of SO2(aq)
by O3(aq) and H2O2(aq), which thus represents the
capabilities of most global models; (2) the more advanced
standard EMAC mechanism, which includes inorganic chemistry
and simplified degradation of methane oxidation products;
and (3) the detailed in-cloud OVOC oxidation scheme Jülich
Aqueous-phase Mechanism of Organic Chemistry (JAMOC). By
using EMAC, the global impact of each mechanism is assessed
focusing mainly on tropospheric volatile organic compounds
(VOCs), HOx (HOx=OH+HO2), and O3. This is achieved by
performing a detailed HOx and O3 budget analysis in the gas
and aqueous phase. The resulting changes are evaluated
against O3 and methanol (CH3OH) satellite observations from
the Infrared Atmospheric Sounding Interferometer (IASI) for
2015. In general, the explicit in-cloud oxidation leads to
an overall reduction in predicted OVOC levels and reduces
EMAC's overestimation of some OVOCs in the tropics. The
in-cloud OVOC oxidation shifts the HO2 production from the
gas to the aqueous phase. As a result, the O3 budget is
perturbed with scavenging being enhanced and the gas-phase
chemical losses being reduced. With the simplified in-cloud
chemistry, about 13 Tg yr−1 of O3 is scavenged, which
increases to 336 Tg yr−1 when JAMOC is used. The
highest O3 reduction of $12 \%$ is predicted in the upper
troposphere–lower stratosphere (UTLS). These changes in
the free troposphere significantly reduce the modelled
tropospheric ozone columns, which are known to be generally
overestimated by EMAC and other global atmospheric models.},
cin = {IEK-8},
ddc = {550},
cid = {I:(DE-Juel1)IEK-8-20101013},
pnm = {2111 - Air Quality (POF4-211)},
pid = {G:(DE-HGF)POF4-2111},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000670319200004},
doi = {10.5194/acp-21-9909-2021},
url = {https://juser.fz-juelich.de/record/902281},
}