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| Titel |
Identifying emission source regions and transport pathways of very short-lived halogens over the Western Pacific |
| VerfasserIn |
Robyn Butler, Paul Palmer, Liang Feng, Neil Harris, Lucy Carpenter, Steve Andrews, Elliot Atlas, Ross Salawitch, Laura Pan, Valeria Donets, Sue Schauffler |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250128140
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| Publikation (Nr.) |
 EGU/EGU2016-8093.pdf |
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| Zusammenfassung |
| Deep, tropical convective systems lead to the rapid transport of very short-lived halogenated
substances (VSLS) to the tropical tropopause layer (TTL). They are then subsequently
transported to the lower stratosphere and chemically broken down to release the
constituent halogens that catalytically destroy ozone. Although the oceans are known to
represent the largest VSLS source, the relative contribution of geographical regions
through emission and transport is poorly understood. We present a study on the origin
and variability of VSLS over the Western Pacific using data collected during the
CAST and CONTRAST measurement campaigns, January/February 2014. We have
developed a version of the GEOS-Chem atmospheric chemistry transport model
that tags emissions of bromoform (CHBr3) and dibromomethane (CH2Br2) from
different geographical regions. We focus the source regions on land and (coastal
and open) oceanic emissions. We have also developed a similar tagged method
to calculate the physical age of air parcels from these source regions to quantify
the speed of vertical transport. Using this approach we have quantified relative
contributions of source regions and show that open oceanic emission regions are the
dominant source of VSLS gases during the measurement campaigns. By looking at
variability over the region, we see that this is caused by direct convection of marine
emissions over the open ocean leading to increased contribution to CHBr3 and CH2Br2
mixing ratios from this source region. Open oceanic emissions are transported to the
TTL within the average atmospheric lifetime of CHBr3, the shorter lived species,
whereas emissions from coastal ocean and land source regions have an older physical
age at the TTL. The relative contribution from island land masses in the campaign
region have no impact over the vertical profile but does impact local mixing ratios. |
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