Atmos. Chem. Phys. Discuss., 10, 12665-12712, 2010
www.atmos-chem-phys-discuss.net/10/12665/2010/
doi:10.5194/acpd-10-12665-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
CO2 and its correlation with CO at a rural site near Beijing: implications for combustion efficiency in China
Y. Wang1, J. W. Munger2, S. Xu1, M. B. McElroy2, J. Hao1, C. P. Nielsen3, and H. Ma1
1Department of Environmental Science and Engineering and State Key Joint Laboratory of Environment Simulation and Pollution, Tsinghua University, Beijing, China
2Department of Earth and Planetary Sciences and School of Engineering and Applied Sciences. Harvard University, Cambridge, Massachusetts, USA
3Harvard China Project and School of Engineering and Applied Sciences. Harvard University, Cambridge, Massachusetts, USA

Abstract. Although China has surpassed the United States as the world's largest carbon dioxide emitter, in situ measurements of atmospheric CO2 have been sparse in China. This paper analyzes hourly CO2 and its correlation with CO at Miyun, a rural site near Beijing, over a period of 51 months (December 2004 through February 2009). The CO2-CO correlation analysis binned by local time is shown to provide useful information with statistical significance even in the growing seasons. We found that the intercept, representing initial condition imposed by global distribution of CO2 with influence of photosynthesis and respiration, exhibits diurnal cycles differing by season. The background CO2 (CO2,b) derived from Miyun observations is comparable to CO2 observed at an upwind baseline station. Annual growth of overall mean CO2 at Miyun is estimated at 2.7 ppm yr−1 while that of CO2,b−1 similar to the mean growth rate at northern mid-latitude background stations. This suggests relatively faster increase in the regional CO2 sources in China than the global average, consistent with bottom-up studies of CO2 emissions. For air masses with trajectories through the northern China boundary layer, mean winter CO2/CO correlation slopes (dCO2/dCO) increased by 2.8±0.9 ppmv/ppmv or 11% from 2005–2006 to 2007–2008. The increase in dCO2/dCO indicates improvement in overall combustion efficiency over northern China after winter 2007, attributed to pollution reduction measures associated with the 2008 Beijing Olympics. Observed CO2/CO ratio at Miyun is 25% higher than the bottom-up CO2/CO emission ratio, suggesting a contribution of respired CO2 from urban residents in the observations and uncertainty in the emission estimates.

Citation: Wang, Y., Munger, J. W., Xu, S., McElroy, M. B., Hao, J., Nielsen, C. P., and Ma, H.: CO2 and its correlation with CO at a rural site near Beijing: implications for combustion efficiency in China, Atmos. Chem. Phys. Discuss., 10, 12665-12712, doi:10.5194/acpd-10-12665-2010, 2010.
 
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