ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-12-7677-2012 Eddy covariance measurements of CO<sub>2</sub> and energy fluxes in the city of Beijing Liu H. Z. 1 Feng J. W. 1 Järvi L. 2 Vesala T. 2 LAPC, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China Department of Physics, University of Helsinki, P.O. Box 48, 00014 University of Helsinki, Finland 16 03 2012 12 3 7677 7704 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/12/7677/2012/acpd-12-7677-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/12/7677/2012/acpd-12-7677-2012.pdf

Long-term measurement of carbon dioxide flux (<i>F</i><sub>c</sub>) 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 CO<sub>2</sub> 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 <i>F</i><sub>c</sub> in this urban environment of a developing country. Both on a diurnal and monthly scale, the urban surface acted as a net source for CO<sub>2</sub> and downward fluxes were only occasionally observed. The diurnal pattern of <i>F</i><sub>c</sub> showed dependence on automobile traffic and the typical two peak traffic pattern appeared in <i>F</i><sub>c</sub> diurnal cycle. Also, the <i>F</i><sub>c</sub> was higher on weekdays than on weekends due to the higher traffic volumes on weekdays. On seasonal scale, <i>F</i><sub>c</sub> was generally higher in winter than during other seasons, likely due to domestic heating during colder months. Total annual average CO<sub>2</sub> emissions were estimated to be 4.90 kg C m<sup>−2</sup> y<sup>−1</sup> over the 4-yr period.

 References Aubinet, M.: Eddy covariance CO<sub>2</sub> flux measurements in nocturnal conditions: An analysis of the problem, Ecol. Appl., 18, 1368–1378, 2008. Baldocchi, D., Finnigan, J., Wilson, K., Paw U, K. T., and Falge, E.: On measuring net ecosystem carbon exchange over tall vegetation on complex terrain, Bound-Lay. Meteorol., 96, 257–291, 2000. Baldocchi, D., Falge, E., Gu, L., Olson, R., Hollinger, D., Running, S., Anthoni, P., Bernhofer, C., Davis, K., and Evans, R.: FLUXNET: A new tool to study the temporal and spatial variability of ecosystem-scale carbon dioxide, water vapor, and energy flux densities, B. Am. Meteorol. Soc., 82, 2415–2434, 2001. Bergeron, O. and Strachan, I. B.: CO<sub>2</sub> sources and sinks in urban and suburban areas of a northern mid-latitude city, Atmos. Environ., 45, 1564–1573, 2011. Burri, S., Frey, C., Parlow, E., and Vogt, R.: CO<sub>2</sub> fluxes and concentrations over an urban surface in Cairo/Egypt, The seventh International Conference on Urban Climate, Yokohama, Japan, 2009. Coutts, A. M., Beringer, J., and Tapper, N. J.: Characteristics influencing the variability of urban CO<sub>2</sub> fluxes in Melbourne, Australia, Atmos. Environ., 41, 51–62, 2007. Crawford, B., Grimmond, C. S. B., and Christen, A.: Five years of carbon dioxide fluxes measurements in a highly vegetated suburban area, Atmos. Environ., 45, 896–905, 2011. Falge, E., Baldocchi, D., Olson, R., Anthoni, P., Aubinet, M., Bernhofer, C., Burba, G., Ceulemans, R., Clement, R., Dolman, H., Granier, A., Gross, P., Grunwald, T., Hollinger, D., Jensen, N., Katul, G., Keronen, P., Kowalski, A., Lai, C. T., Law, B. E., Meyers, T., Moncrieff, J., Moors, E., Munger, J. W., Pilegaard, K., Rannik, U., Rebmann, C., Suyker, A., Tenhunen, J., Tu, K., Verma, S., Vesala, T., Wilson, K., and Wofsy, S.: Gap filling strategies for defensible annual sums of net ecosystem exchange, Agr. Forest Meteorol., 107, 43–69, 2001. Foken, T., Göckede, M., Mauder, M., Mahrt, L., Amiro, B., and Munger, W.: Post-field data quality control, in: Handbook of Micrometeorology: A guide for surface flux measurement and analysis, edited by: Lee, X., Massman, W., and Law, B., Kluwer, Dordrecht, 181–208, 2004. Grimmond, C. S. B., King, T., Cropley, F., Nowak, D., and Souch, C.: Local-scale fluxes of carbon dioxide in urban environments: methodological challenges and results from Chicago, Environ. Pollut., 116, S243–S254, 2002. Grimmond, C. S. B., Salmond, J. A., Oke, T. R., Offerle, B., and Lemonsu, A.: Flux and turbulence measurements at a densely built-up site in Marseille: Heat, mass (water and carbon dioxide), and momentum, J. Geophys. Res., 109, D24101, http://dx.doi.org/10.1029/2004JD004936doi:10.1029/2004JD004936, 2004. Helfter, C., Famulari, D., Phillips, G. J., Barlow, J. F., Wood, C. R., Grimmond, C. S. B., and Nemitz, E.: Controls of carbon dioxide concentrations and fluxes above central London, Atmos. Chem. Phys., 11, 1913–1928, http://dx.doi.org/10.5194/acp-11-1913-2011doi:10.5194/acp-11-1913-2011, 2011. Hui, D., Wan S., Su, B., Katul, G., Monson, R., and Luo, Y.: Gap-filling missing data in eddy covariance measurements using multiple imputation (MI) for annual estimations, Agr. Forest Meteorol., 121, 93–111, 2003. Intergovernmental Panel on Climate Change: IPCC AR4 report, Contribution of working group I to the Fourth Assessment Report of the Intergovermental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2007. Kaimal, J. C. and Finnigan, J. J.: Atmospheric boundary layer flows: Their structure and measurement, Oxford University Press, New York, 289 pp., 1994. Kalnay, E. and Cai, M.: Impact of urbanization and land-use change on climate, Nature, 423, 528–531, 2003. Kordowski, K. and Kuttler, W.: Carbon dioxide fluxes over an urban park area, Atmos. Environ., 44, 2722–2730, 2010. Kormann, R. and Meixner, F. X.: An analytical footprint model for non-neutral stratification, Bound-Lay. Meteorol., 99, 207–224, 2001. Lee, X., Massman, W., and Law, B.: Handbook of micrometeorology: A guide for surface flux measurement and analysis, Kluwer, Dordrecht, 250 pp., 2004. Li, Q., Liu, H. Z., Hu, F, Hong, Z. X., and Li, A. G.: The determination of the aero dynamical parameters over urban land surface, Clim. Environ. Res., 8, 443–450, 2003 (in Chinese). Massman, W. J. and Lee, X.: Eddy covariance flux corrections and uncertainties in long-term studies of carbon and energy exchanges, Agr. Forest Meteorol., 113, 121–144, 2002. Matese, A., Gioli, B., Vaccari, F. P., Zaldei, A., and Miglietta, F.: Carbon dioxide emissions of the city center of Firenze, Italy: measurement, evaluation, and source partitioning, J. Appl. Meteorol. Climatol., 48, 1940–1947, 2009. Moriwaki, R. and Kanda, M.: Seasonal and diurnal fluxes of radiation, heat, water vapor, and carbon dioxide over a suburban area, J. Appl. Meteorol., 43, 1700–1710, 2004. Nemitz, E., Hargreaves, K. J., McDonald, A. G., Dorsey, J. R., and Fowler, D.: Micrometeorological measurements of the urban heat budget and CO<sub>2</sub> emissions on a city scale, Environ. Sci. Technol., 36, 3139–3146, 2002. Pan, J. and Niu, F.: Annual report on urban development of china, Social Science Literature Publishing, Beijing, China, 2010 (in Chinese). Pawlak, W., Fortuniak, K., and Siedlecki, M.: Carbon dioxide flux in the centre of Łódź, Poland – analysis of a 2-year eddy covariance measurement data set, Int. J. Climatol., 31, 232–243, 2011. Satterthwaite, D.: Cities' contribution to global warming: notes on the allocation of greenhouse gas emissions, Environ. Urbanization, 20, 539–549, 2008. Schotanus, P., Nieuwstadt, F. T. M., and Bruin, H. A. R.: Temperature measurement with a sonic anemometer and its application to heat and moisture fluxes, Bound-Lay. Meteorol., 26, 81–93, 1983. Song, T. and Wang, Y. S.: Carbon dioxide fluxes from an urban area in Beijing, Atmos. Res., 106, 139–149, 2012. Stewart, I. D.: Classifying urban climate field sites by "Local Climate Zones", Urban Climate News, 34, 8–11, http://www.urban-climate.org/IAUC034.pdf, 2009. Velasco, E. and Roth, M.: Cities as Net Sources of CO<sub>2</sub>: Review of atmospheric CO<sub>2</sub> exchange in urban environments measured by eddy covariance technique, Geogr. Compass, 4, 1238–1259, 2010. Velasco, E., Pressley, S., Grivicke, R., Allwine, E., Coons, T., Foster, W., Jobson, B. T., Westberg, H., Ramos, R., Hernández, F., Molina, L. T., and Lamb, B.: Eddy covariance flux measurements of pollutant gases in urban Mexico City, Atmos. Chem. Phys., 9, 7325–7342, http://dx.doi.org/10.5194/acp-9-7325-2009doi:10.5194/acp-9-7325-2009, 2009. Vesala, T., JÄRvi, L., Launiainen, S., Sogachev, A., Rannik, Ü., Mammarella, I., Siivola, E., Keronen, P., Rinne, J, Riikonen, A. N. U., and Nikinmaa, E.: Surface-atmosphere interactions over complex urban terrain in Helsinki, Finland, Tellus, 60B, 188–199, 2008. Vickers, D. and Mahrt, L.: Quality control and flux sampling problems for tower and aircraft data, J. Atmos. Ocean. Technol., 14, 512–526, 1997. Vogt, R., Christen, A., Rotach, M. W., Roth, M., and Satyanarayana, A. N. V.: Temporal dynamics of CO<sub>2</sub> fluxes and profiles over a central European city, Theor. Appl. Climatol., 84, 117–126, 2006. Webb, E. K., Pearman, G. I., and Leuning, R.: Correction of flux measurements for density effects due to heat and water vapour transfer, Q. J. Roy. Meteorol. Soc., 106, 85–100, 1980. Wood, C. R., Lacser, A., Barlow, J. F., Padhra, A., Belcher, S. E., Nemitz, E., Helfter, C., Famulari, D., and Grimmond, C. S. B.: Turbulent flow at 190m height above London during 2006–2008: A climatology and the applicability of similarity theory, Bound-Lay. Meteorol., 137, 77–96, 2010.