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| Titel |
Meteorological factors controlling low-level continental pollutant outflow across a coast |
| VerfasserIn |
D. L. Peake, H. F. Dacre, J. Methven, O. Coceal |
| 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. 23 ; Nr. 14, no. 23 (2014-12-15), S.13295-13312 |
| Datensatznummer |
250119238
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| Publikation (Nr.) |
 copernicus.org/acp-14-13295-2014.pdf |
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| Zusammenfassung |
| Coastal outflow describes the horizontal advection of pollutants from
the continental boundary layer (BL) across a coastline. The outflow can
ventilate polluted continental BLs and thus regulate air
quality in highly populated coastal regions. This paper investigates
the factors controlling coastal outflow and quantifies their
importance as a ventilation mechanism. Tracers in the Met Office
Unified Model (MetUM) are used to examine the magnitude and
variability of coastal outflow over the eastern United States during
summer 2004. Over the 4 week period examined, ventilation of tracer
from the continental BL via coastal outflow occurs with
the same magnitude as vertical ventilation via convection and
advection. The relative importance of tracer decay rate,
cross-coastal advection rate, and a parameter based on the relative
continental and marine BL heights on coastal outflow is
assessed by reducing the problem to a time-dependent box model. The
ratio of the advection rate and decay rate is a dimensionless
parameter which determines whether tracers are long-lived or
short-lived. Long- and short-lived tracers exhibit different
behaviours with respect to coastal outflow. Short-lived tracers
exhibit large diurnal variability in coastal outflow but long-lived
tracers do not. For short-lived tracers, increasing the advection rate
increases the diurnally averaged magnitude of coastal outflow, but this has
the opposite effect for very long-lived tracers. By using the
box-model solutions to interpret the MetUM simulations, a land width is
determined which represents the distance inland over which emissions
contribute significantly to coastal outflow. A land width of between
100 and 400 km is found to be representative for a tracer with a
lifetime of 24 h. |
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