Oxidation of low-molecular-weight organic compounds in cloud droplets: global impact on tropospheric oxidants

Abstract. In liquid cloud droplets, superoxide anion (O2(aq)-) is known to quickly consume ozone (O3(aq)), which relatively insoluble. The significance of this reaction as a tropospheric O3 sink sensitive the abundance O2(aq)- and therefore production its main precursor, hydroperoxyl radical (HO2(aq)). aqueous-phase oxidation oxygenated volatile organic compounds (OVOCs) major source HO2(aq) in droplets. Hence, lack explicit chemical kinetics global atmospheric models leads general underestimation clouds sinks. study, importance in-cloud OVOC for composition assessed by using Chemistry As A Boxmodel Application (CAABA) ECHAM/MESSy Atmospheric (EMAC) model, are both capable explicitly representing relevant transformations. For analysis, three different mechanisms employed: (1) one including basic SO2(aq) O3(aq) H2O2(aq), thus represents capabilities most models; (2) more advanced standard EMAC mechanism, includes inorganic chemistry simplified degradation methane products; (3) detailed scheme Jülich Aqueous-phase Mechanism Organic (JAMOC). By EMAC, impact each mechanism focusing mainly on (VOCs), HOx (HOx=OH+HO2), O3. This achieved performing budget analysis gas aqueous phase. resulting changes evaluated against methanol (CH3OH) satellite observations from Infrared Sounding Interferometer (IASI) 2015. general, an overall reduction predicted levels reduces EMAC's overestimation some OVOCs tropics. shifts HO2 result, perturbed with scavenging being enhanced gas-phase losses reduced. With chemistry, about 13 Tg yr−1 scavenged, increases 336 when JAMOC used. highest 12 % upper troposphere–lower stratosphere (UTLS). These free troposphere significantly reduce modelled columns, be generally overestimated other models.