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| Titel |
Quantification of topographic venting of boundary layer air to the free troposphere |
| VerfasserIn |
S. Henne, M. Furger, S. Nyeki, M. Steinbacher, B. Neininger, S. F. J. Wekker, J. Dommen, N. Spichtinger, A. Stohl, A. S. H. Prévôt |
| 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 ; 4, no. 2 ; Nr. 4, no. 2 (2004-03-24), S.497-509 |
| Datensatznummer |
250001607
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| Publikation (Nr.) |
 copernicus.org/acp-4-497-2004.pdf |
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| Zusammenfassung |
| Net vertical air mass export by thermally driven flows from the
atmospheric boundary layer (ABL) to the free troposphere (FT)
above deep Alpine valleys was investigated. The vertical export of
pollutants above mountainous terrain is presently poorly
represented in global chemistry transport models (GCTMs) and needs
to be quantified. Air mass budgets were calculated using
aircraft observations obtained in deep Alpine valleys. The results
show that on average 3 times the valley air mass is exported
vertically per day under fair weather conditions. During daytime
the type of valleys investigated in this study can act as an
efficient "air pump" that transports pollutants upward. The
slope wind system within the valley plays an important role in
redistributing pollutants. Nitrogen oxide emissions in mountainous
regions are efficiently injected into the FT. This could enhance
their ozone (O3) production efficiency and thus
influences tropospheric pollution budgets. Once lifted to the FT
above the Alps pollutants are transported horizontally by the
synoptic flow and are subject to European pollution export.
Forward trajectory studies show that under fair weather conditions
two major pathways for air masses above the Alps dominate. Air
masses moving north are mixed throughout the whole tropospheric
column and further transported eastward towards Asia. Air masses
moving south descend within the subtropical high pressure system
above the Mediterranean. |
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