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| Titel |
Long term measurements and modelling of OH and HO2 radicals at a tropical marine location |
| VerfasserIn |
Daniel Stone, Stewart Vaughan, Trevor Ingham, Lisa Whalley, Mathew Evans, Dwayne Heard |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250052269
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| Zusammenfassung |
| The dominant fraction of global methane oxidation occurs in tropical marine regions. Thus
understanding the processes controlling OH concentrations in these regions is important for
understanding the concentrations of species such as CH4 and O3 and thus for our
understanding of climate past, present and future.
Long-term measurements of OH, and the closely coupled HO2 radical, were made using
FAGE (Fluorescence Assay by Gas Expansion) at the Cape Verde Atmospheric Observatory
(16.85 oN, 24.87 oW) on the island of Sao Vicente as part of the Seasonal Oxidant Study
(SOS) in the tropical Atlantic during three distinct seasonal periods; SOS1 during
February-March (generally dry with clear sky), in June during SOS2 (clear and dry), and
SOS3 in September (some sustained periods of heavy rainfall). Preliminary data analysis
suggests mean midday concentrations of OH were 3.6, 3.5 and 4.6 Ã 106 cm-3 for SOS1, 2
and 3, with corresponding mean HO2 noontime concentrations of 1.8, 2.1 and 1.8 Ã 108
cm-3.
The zero dimensional Dynamically Simple Model of Atmospheric Chemical Complexity
(DSMACC), based on the Master Chemical Mechanism (MCM) and incorporating halogen
chemistry and heterogeneous loss to aerosol surfaces, has been used to investigate the
behaviour of OH and HO2 during each campaign. Model calculations successfully replicate
the relative diurnal trends of both OH and HO2, but provide an overestimation in the
concentration of both species, suggesting an overestimation of sources and/or an
underprediction of sinks.
The role of different processes in controlling the OH and HO2 budgets on different
timescales will be discussed and compared to the GEOS-Chem global atmospheric chemistry
transport model. |
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