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| Titel |
The impact of embedded valleys on daytime pollution transport over a mountain range |
| VerfasserIn |
M. N. Lang, A. Gohm, J. S. Wagner |
| 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 ; 15, no. 20 ; Nr. 15, no. 20 (2015-10-28), S.11981-11998 |
| Datensatznummer |
250120127
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| Publikation (Nr.) |
 copernicus.org/acp-15-11981-2015.pdf |
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| Zusammenfassung |
| Idealized large-eddy simulations were performed to investigate the impact of
different mountain geometries on daytime pollution transport by thermally
driven winds. The main objective was to determine interactions between
plain-to-mountain and slope wind systems, and their influence on the
pollution distribution over complex terrain. For this purpose, tracer
analyses were conducted over a quasi-two-dimensional mountain range with
embedded valleys bordered by ridges with different crest heights and a flat
foreland in cross-mountain direction. The valley depth was varied
systematically. It was found that different flow regimes develop dependent on
the valley floor height. In the case of elevated valley floors, the
plain-to-mountain wind descends into the potentially warmer valley and
replaces the opposing upslope wind. This superimposed plain-to-mountain wind
increases the pollution transport towards the main ridge by an additional
20 % compared to the regime with a deep valley. Due to mountain and
advective venting, the vertical exchange is 3.6 times higher over complex
terrain than over a flat plain. However, the calculated vertical exchange is
strongly sensitive to the definition of the convective boundary layer height.
In summary, the impact of the terrain geometry on the mechanisms of pollution
transport confirms the necessity to account for topographic effects in future
boundary layer parameterization schemes. |
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