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| Titel |
Convective transport of very short lived bromocarbons to the stratosphere |
| VerfasserIn |
Q. Liang, E. Atlas, D. Blake, M. Dorf, K. Pfeilsticker, S. Schauffler |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 11 ; Nr. 14, no. 11 (2014-06-11), S.5781-5792 |
| Datensatznummer |
250118786
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| Publikation (Nr.) |
 copernicus.org/acp-14-5781-2014.pdf |
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| Zusammenfassung |
| We use the NASA Goddard Earth Observing System (GEOS) Chemistry Climate Model
(GEOSCCM) to quantify the contribution of the two most important brominated
very short lived substances (VSLSs), bromoform (CHBr3) and dibromomethane
(CH2Br2), to stratospheric bromine and its sensitivity to convection
strength. Model simulations suggest that the most active transport of VSLSs
from the marine boundary layer through the tropopause occurs over the
tropical Indian Ocean, the tropical western Pacific, and off the Pacific
coast of Mexico. Together, convective lofting of CHBr3 and CH2Br2
and their degradation products supplies ~8 ppt total bromine to the
base of the tropical tropopause layer (TTL, ~150 hPa), similar to the
amount of VSLS organic bromine available in the marine boundary layer
(~7.8–8.4 ppt) in the active convective lofting regions mentioned
above. Of the total ~8 ppt VSLS bromine that enters the base of the TTL
at ~150 hPa, half is in the form of organic source gases and half in
the form of inorganic product gases. Only a small portion (<10%) of the
VSLS-originated bromine is removed via wet scavenging in the
TTL before reaching the lower stratosphere. On average, globally, CHBr3
and CH2Br2 together contribute ~7.7 pptv to the present-day
inorganic bromine in the stratosphere. However, varying model deep-convection
strength between maximum (strongest) and minimum (weakest) convection
conditions can introduce a ~2.6 pptv uncertainty in the contribution of
VSLSs to inorganic bromine in the stratosphere (BryVSLS). Contrary to conventional wisdom, the minimum convection
condition leads to a larger BryVSLS as the reduced
scavenging in soluble product gases, and thus a significant increase in
product gas injection (2–3 ppt), greatly exceeds the relatively minor
decrease in source gas injection (a few 10ths ppt). |
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