Controls of carbon dioxide concentrations and fluxes above central London

Helfter, C. ORCID: https://orcid.org/0000-0001-5773-4652; Famulari, D.; Phillips, G.J.; Barlow, J.F.; Wood, C.R.; Grimmond, C.S.B.; Nemitz, E. ORCID: https://orcid.org/0000-0002-1765-6298. 2011 Controls of carbon dioxide concentrations and fluxes above central London. Atmospheric Chemistry and Physics, 11 (5). 1913-1928. https://doi.org/10.5194/acp-11-1913-2011

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Abstract/Summary

Eddy-covariance measurements of carbon dioxide fluxes were taken continuously between October 2006 and May 2008 at 190m 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.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.5194/acp-11-1913-2011
Programmes:	CEH Topics & Objectives 2009 - 2012 > Biogeochemistry > BGC Topic 1 - Monitoring and Interpretation of Biogeochemical and Climate Changes > BGC - 1.1 - Monitor concentrations, fluxes, physico-chemical forms of current and emerging pollutants ...
UKCEH and CEH Sections/Science Areas:	Billett (to November 2013)
ISSN:	1680-7316
Additional Pages:	Supplement, corrigendum
Additional Information. Not used in RCUK Gateway to Research.:	Open Access article - click on the Official URL link for full text. NB. There is a Corrigendum to this paper in Atmospheric Chemistry and Physics, 2011, 11, 2081 - click on Related URL to access.
NORA Subject Terms:	Atmospheric Sciences
Related URLs:	Other Discussion paper
Date made live:	07 Sep 2011 15:02 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/15049

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