Atmospheric Chemistry and Physics Controls of carbon dioxide concentrations and fluxes above central London

Abstract. 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 quan-tify 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 cen-tral boroughs. CO2 emissions were found to be mainly con-trolled by fossil fuel combustion (e.g. traffic, commercial and domestic heating). The measurement period allowed investi-gation of both diurnal patterns and seasonal trends. Diurnal averages of CO2 fluxes were found to be correlated with traf-fic but also exhibited an inverse dependency on atmospheric stability in the near-neutral range, with higher fluxes coin-ciding with unstable stratification during most seasons and perhaps reflecting how changes in heating-related natural ga