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| Titel |
Vertical distribution of BrO and aersols at the Dead Sea Valley |
| VerfasserIn |
Robert Holla, Stefan Schmitt, Jutta Zingler, Udo Frieß, Ulrich Corsmeier, Christoph Kottmeier, Ulrich Platt |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250079717
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| Zusammenfassung |
| The Dead Sea Valley (DSV) is known for its unique topographic and atmospheric conditions.
In summer, the meteorological conditions are quite stable. Thus, atmospheric chemistry can
be investigated under reproducible conditions. This and the large abundance of bromine
monoxide (BrO) makes it a perfect natural laboratory to gain insight into the bromine
chemistry in the lower troposphere. Thus the DSV can serve as a model for other salt
lakes or saline soil areas where the boundary conditions are less suitable for field
measurements.
During the last years, several measurements of Reactive Halogen Species (RHS) were
performed in the DSV and at other salt lakes, however, the sources of RHS and the
contributions of different release processes are not fully understood yet. Open questions are:
What are the main sources of the BrO release and to which extent are aerosols involved?
Which meteorological conditions favor the BrO release and what is the impact of NOx on the
bromine chemistry?
Focussed on these questions, an extensive field campaign was performed in the
framework of the DFG project HALOPROC. For the first time vertical profiles of BrO and
NO2 at the Dead Sea were determined and interpreted in terms of the special atmospheric
dynamics in the Dead Sea Valley. This was achieved by combining a Long-path(LP)-DOAS
instrument, situated at Ein Bokek, with three Multi-AXis(MAX)-DOAS instruments, two
stationary (Ein Bokek and Masada Top) and one mounted on a car. Ground level abundances
of BrO and NO2 inferred from MAX-DOAS measurements were validated by LP-DOAS and
show very good agreement. On several days, elevated layers of BrO and aerosols could be
observed in different altitudes by the MAX-DOAS instruments. This could be an indication
for vertical transport barriers induced by convective inversion layers leading to an
enrichment of aerosol within the Dead Sea Valley. These vertical transport barriers
might have an impact on the formation of BrO in two ways: First, BrO emitted by
the sea surface is accumulated directly below the transport barrier, and second,
enhanced relative humidity might favor heterogeneous bromine release from aerosols.
BrO mixing ratios of more than 100 ppt were found close to the ground and in
several hundred meters above ground level. NO2 levels below 1-2 ppb seem to
be a prerequisite for a high BrO production. Our measurements indicate a strong
dependence of BrO release on the topography and local and meso-scale meteorology. |
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