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| Titel |
Controls of carbon dioxide concentrations and fluxes above central London |
| VerfasserIn |
C. Helfter, D. Famulari, G. J. Phillips, J. F. Barlow, C. R. Wood, C. S. B. Grimmond, E. Nemitz |
| 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 ; 11, no. 5 ; Nr. 11, no. 5 (2011-03-02), S.1913-1928 |
| Datensatznummer |
250009438
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| Publikation (Nr.) |
 copernicus.org/acp-11-1913-2011.pdf |
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| Zusammenfassung |
| Eddy-covariance measurements of carbon dioxide fluxes were taken
continuously between October 2006 and May 2008 at 190 m height in central
London (UK) to quantify emissions and study their controls. Inner London,
with a population of 8.2 million (~5000 inhabitants per km2) is
heavily built up with 8% vegetation cover within the central boroughs.
CO2 emissions were found to be mainly controlled by fossil fuel
combustion (e.g. traffic, commercial and domestic heating). The measurement
period allowed investigation of both diurnal patterns and seasonal trends.
Diurnal averages of CO2 fluxes were found to be correlated with traffic
but also exhibited an inverse dependency on atmospheric stability in the
near-neutral range, with higher fluxes coinciding with unstable
stratification during most seasons and perhaps reflecting how changes in
heating-related natural gas consumption and, to a lesser extent,
photosynthetic activity controlled the seasonal variability. Despite
measurements being taken at ca. 22 times the mean building height, coupling
with street level was adequate, especially during daytime. Night-time saw a
higher occurrence of stable or neutral stratification, especially in autumn
and winter, which resulted in data loss in post-processing and caused the
tower to become decoupled from street level. CO2 fluxes observed at
night were not always correlated with traffic counts, probably reflecting
this decoupling, but also the fact that at night heating was always a larger
source than traffic. No significant difference was found between
the annual estimate of net exchange of CO2 for the expected measurement
footprint and the values derived from the National Atmospheric Emissions
Inventory (NAEI), with daytime fluxes differing by only 3%. This
agreement with NAEI data also supported the use of the simple flux footprint
model which was applied to the London site; this also suggests that
individual roughness elements did not significantly affect the measurements
due to the large ratio of measurement height to mean building height. |
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