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| Titel |
Importance of reactive halogens in the tropical marine atmosphere using WRF-chem |
| VerfasserIn |
Alba Badia, Claire E. Reeves, Alex Baker, Rainer Volkamer, Eric Apel, Alfonso Saiz-Lopez, Roland von Glasow |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143991
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| Publikation (Nr.) |
 EGU/EGU2017-7767.pdf |
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| Zusammenfassung |
| Halogen species (chlorine, bromine and iodine) are known to play an important
role in the chemistry and oxidizing capacity of the troposphere, particularly in the
marine boundary layer (MBL). Reactive halogens participate in catalytic reaction
cycles that efficiently destroy O3, change the HOX and NOX partitioning, affect the
oxidation of volatile organic compounds (VOCs) and mercury, reduce the lifetime
of methane, and take part in new particle formation. Numerical models predicted
that reactive halogen compounds account for 30% of O3 destruction in the MBL
and 5-20% globally. Up to 34% of O3 loss in the tropical East Pacific is due to I
and Br combined. Recent studies have highlighted the key role that heterogeneous
chemistry plays in explaining observations of BrO and IO abundances in the tropical
troposphere.
The main objective of this study is to investigate the atmospheric chemistry in the tropical
East Pacific with a focus on reactive halogens using the Weather Research and Forecasting
model coupled with Chemistry (WRF-Chem) and field data from the TORERO campaign.
Our reaction mechanism in WRF-Chem is based on the MOZART mechanism and has been
extended to include bromine, chlorine and iodine chemistry. Heterogeneous recycling
reactions involving sea-salt aerosol and other particles have been included into the model,
along with oceanic emissions of important OVOCs and halocarbons. Sea surface emissions
of inorganic iodine are calculated using the parameterisation of Carpenter et al.,
2013.
Focusing on TORERO observations from the ships and a selected number of flights we
present the tropospheric impacts of halogens (BrO, IO) in the tropospheric chemistry
of relevant species (O3, OH and OVOCS). Sensitivity runs are made in order to
study the impact of heterogeneous chemistry in the iodine and bromine species
partitioning. A comparison between the online calculation of Very Short Lived
Halocarbons (VSLH) oceanic emissions with prescribed oceanic emissions is also
presented.
Results show that a better performance in O3 concentrations is obtained with the
inclusion of halogens. We see a big impact on the Bry partitioning with an improvement of
modelled BrO when the heterogeneous chemistry is included. An improvement of our model
results is seen when online oceanic emissions are computed. |
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