Four-year (2006–2009) eddy covariance measurements of CO2 flux over an urban area in Beijing 1LAPC, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
03 Sep 2012
2Department of Physics, University of Helsinki, P.O. Box 48, 00014 University of Helsinki, Finland
Received: 25 Nov 2011 – Published in Atmos. Chem. Phys. Discuss.: 16 Mar 2012Abstract. Long-term measurements of carbon dioxide flux (Fc) and
the latent and sensible heat fluxes were performed using the eddy covariance
(EC) method in Beijing, China 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. Winter and
autumn were two transition periods of the turbulent fluxes. The source area
of Fc was highly heterogeneous, which consisted of buildings, parks, and
highways. It was of interest to study of the temporal and spatial
variability of Fc in this urban environment of a developing country.
Both on 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 traffic and the typical two
peak traffic patterns appeared in the diurnal cycle. Also 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 from the neighborhood of the tower
were estimated to be 4.90 kg C m−2 yr−1 over the 4-yr period.
Total vehicle population was the most important factor controlling the
inter-annual variability of Fc in this urban area.
Revised: 22 Aug 2012 – Accepted: 22 Aug 2012 – Published: 03 Sep 2012
Citation: Liu, H. Z., Feng, J. W., Järvi, L., and Vesala, T.: Four-year (2006–2009) eddy covariance measurements of CO2 flux over an urban area in Beijing, Atmos. Chem. Phys., 12, 7881-7892, doi:10.5194/acp-12-7881-2012, 2012.