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@ARTICLE{Rosanka:902278,
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 / Discussions},
volume = {},
issn = {1680-7367},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {FZJ-2021-04141},
pages = {},
year = {2020},
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 tropospheric
O3 sink is sensitive to the abundance of O−2(aq) and
therefore to the production of its main precursor,
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 atmospheric model ECHAM/MESSy (EMAC),
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) via 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 of predicted OVOCs 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 a−1 of O3 are scavenged, which
increases to 336 Tg a−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},
doi = {10.5194/acp-2020-1041},
url = {https://juser.fz-juelich.de/record/902278},
}