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| Titel |
Overview of Reactive Halogen Species in the Marine Boundary Layer observed with different DOAS techniques |
| VerfasserIn |
Johannes Lampel, Jens Tschritter, Denis Pöhler, Katja Grossmann, Martin Horbanski, Udo Frieß, Ulrich Platt |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096051
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| Publikation (Nr.) |
 EGU/EGU2014-11534.pdf |
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| Zusammenfassung |
| Reactive halogen species (RHS) in the in the marine boundary layer have the potential to
influence the ozone budget on a global scale, but their release processes are partly uncertain
and measurements on global scale with the required precision are rare. Their direct
dependence on halogenated compounds as precursors is uncertain as well as the precursors’
fluxes. To clarify these interdependencies various campaigns during the last years with a
broad range of different measured species were performed in the Mauretanian Upwelling,
Cape Verde and the eastern tropical Pacific between 2009 and 2014 mostly within the
SOPRAN project (BMBF Förderkennzeichen 03F0611F). They are used to obtain a picture
of the global distribution of reactive halogen species (RHS) in the marine boundary layer
(MBL) and their driving mechanisms. Cavity-Enhanced (CE) and MAX-DOAS
measurements were performed on several ship and land campaigns. In the later case they
were also accompanied by Longpath (LP)-DOAS measurements. An overview of the
measurement results will be presented.
Iodine monoxide measurements over the open tropical ocean show agreement for
different measurements, most measurement techniques and different campaigns. Especially
during SOPRAN M91 in the Peruvian upwelling region very good agreement for
MAX-DOAS and CE-DOAS inferred IO mixing ratios was found. The good agreement
between the retrieved NO2 and water vapor mixing ratios of the MAX-DOAS and CE-DOAS
measurements further confirms the applied aerosol and trace gas retrieval. Values for BrO
volume mixing ratios in the marine boundary layer apart from so-called ‘BrO-events’
in the upwelling regions of the eastern tropical Atlantic remain challenging. The
limiting factors were often not instrumental limitations, but could rather be found
in measurement errors of literature cross-sections and the way in which spectral
data was analyzed. For coastal studies on Cape Verde LP-DOAS measurements
as well as MAX-DOAS measurements agreed on BrO volume mixing ratios of
2-3ppt, while MAX-DOAS measurements on the open ocean regularly showed lower
values. This indicates that observations at Cape Verde are likely not representative
for open ocean conditions. A reanalysis of ship-borne MAX-DOAS data over the
Atlantic and the Pacific will be presented including first conclusions. Furthermore,
upper limits for glyoxal volume mixing ratios were calculated for two months of
MAX-DOAS data in the tropical Atlantic and eastern tropical Pacific. These 2Ïă upper
limits were found at 4 -
1014 and 7 -
1014 molec/cm2, corresponding roughly to
20-30ppt, which is a factor of four smaller than previous observations on the tropical
Pacific. |
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