Temporal dynamics of CO2 fluxes and profiles over a Central European city
In Summer 2002 eddy covariance flux measurements of CO2 were performed over a dense urban surface. The month-long measurements were carried out in the framework of the Basel Urban Boundary Layer Experiment (BUBBLE). Two Li7500 open path analysers were installed at z/z H = 1.0 and 2.2 above a street canyon with z H the average building height of 14.6 m and z the height above street level. Additionally, profiles of CO2 concentration were sampled at 10 heights from street level up to 2 z H . The minimum and maximum of the average diurnal course of CO2 concentration at 2 z H were 362 and 423 ppmv in late afternoon and early morning, respectively. Daytime CO2 concentrations were not correlated to local sources, e.g. the minimum occurred together with the maximum in traffic load. During night-time CO2 is in general accumulated, except when inversion development is suppressed by frontal passages. CO2 concentrations were always decreasing with height and correspondingly, the fluxes – on average – always directed upward. At z/z H = 2.2 low values of about 3 µmol m−2 s−1 were measured during the second half of the night. During daytime average values reached up to 14 µmol m−2 s−1. The CO2 fluxes are well correlated with the traffic load, with their maxima occurring together in late afternoon. Daytime minimum CO2 concentrations fell below regional background values. Besides vertical mixing and entrainment, it is suggested that this is also due to advection of rural air with reduced CO2 concentration. Comparison with other urban observations shows a large range of differences among urban sites in terms of both CO2 fluxes and concentrations.
KeywordsTraffic Load Street Canyon Eddy Covariance Street Level Urban Boundary Layer
Unable to display preview. Download preview PDF.
- Bernhofer C, Aubinet M, Clement R, Grelle A, Grünwald T, Ibrom A, Jarvis P, Rebmann C, Schulze ED, Tenhunen JD (2003) Spruce Forests (Norway and Sitka Spruce, including Douglas Fir): carbon and water fluxes and balances, ecological and ecophysiological determinants. In: Valentini R (ed) Fluxes of Carbon, Water and Energy of European Forests. Ecological Studies, Vol. 163. Berlin: SpringerGoogle Scholar
- Christen A, Bernhofer C, Parlow E, Rotach MW, Vogt R (2003) Partitioning of turbulent fluxes over different urban surfaces. Fifth International Conference on Urban Climate, September 1–5 2003, Lodz, Poland 4pGoogle Scholar
- Pataki DE, Bowling DR, Ehleringer JR (2003) Seasonal cycle of carbon dioxide and its isotopic composition in an urban atmosphere: Anthropogenic and biogenic effects. J Geophys Res 108: D23, 4735Google Scholar
- Fisher, BEA, Kukkonen, J, Schatzmann, M 2002Meteorology applied to urban air pollution problems COST 715.Int J Environ Pollut16560569Google Scholar
- Grimmond, CSB, Oke, TR 1999Aerodynamic properties of urban areas derived from analysis of surface from.J Appl Meteor3812621292Google Scholar
- Rotach, MW, Vogt, R, Bernhofer, C, Batchvarova, E, Christen, A, Clappier, A, Feddersen, B, Gryning, SE, Martucci, G, Mayer, H, Mitev, V, Oke, TR, Parlow, E, Richner, H, Roth, M, Roulet, YA, Ruffieux, D, Salmond, J, Schatzmann, M, Voogt, J 2005BUBBLE – an Urban Boundary Layer Meteorology Project.Theor Appl Climatol81231261CrossRefGoogle Scholar
- Soegaard, H, Møller-Jensen, L 2003Towards a spatial CO2 budget of a metropolitan region based on textural image classification and flux measurements.Remote Sensing Environ87283294Google Scholar
- Takahashi, HA, Konohira, E, Hiyama, T, Minami, M, Nakamura, T, Yoshida, Y 2002Diurnal variation of CO2 concentration, Δ14C and δ13C in an urban forest: estimate of the anthropogenic and biogenic CO2 contributions.Tellus54B97109Google Scholar
- World Meteorological Organisation (2003) WMO WDCGG Data Summary. WMO WDCGG No. 27, 98pp, available from http://gaw.kishou.go.jp/wdcgg.html