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Atmos. Chem. Phys. Discuss., 12, 7677-7704, 2012
www.atmos-chem-phys-discuss.net/12/7677/2012/ doi:10.5194/acpd-12-7677-2012 © Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License. |
Eddy covariance measurements of CO2 and energy fluxes in the city of Beijing
1LAPC, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
2Department of Physics, University of Helsinki, P.O. Box 48, 00014 University of Helsinki, Finland
Abstract. Long-term measurement of carbon dioxide flux (Fc) was performed using the eddy covariance (EC) method in the Beijing megacity over a 4-yr period in 2006–2009. The EC setup was installed at a height of 47 m on the Beijing 325-m meteorological tower in the northwest part of the city. Latent heat flux dominated the energy exchange between the urban surface and the atmosphere in summer, while sensible heat flux was the main component in the spring. The source area of the measurements of CO2 is highly heterogeneous, which consists of buildings, parks, and highways. It is valuable for global carbon budget research to study the temporal and spatial variability of Fc in this urban environment of a developing country. Both on a diurnal and monthly scale, the urban surface acted as a net source for CO2 and downward fluxes were only occasionally observed. The diurnal pattern of Fc showed dependence on automobile traffic and the typical two peak traffic pattern appeared in Fc diurnal cycle. Also, the Fc was higher on weekdays than on weekends due to the higher traffic volumes on weekdays. On seasonal scale, Fc was generally higher in winter than during other seasons, likely due to domestic heating during colder months. Total annual average CO2 emissions were estimated to be 4.90 kg C m−2 y−1 over the 4-yr period.
Citation: Liu, H. Z., Feng, J. W., Järvi, L., and Vesala, T.: Eddy covariance measurements of CO2 and energy fluxes in the city of Beijing, Atmos. Chem. Phys. Discuss., 12, 7677-7704, doi:10.5194/acpd-12-7677-2012, 2012.