ACP Atmospheric Chemistry and Physics ACP Atmos. Chem. Phys. 1680-7324 Copernicus Publications Göttingen, Germany 10.5194/acp-13-7607-2013 Improved simulation of regional CO<sub>2</sub> surface concentrations using GEOS-Chem and fluxes from VEGAS Chen Z. H. 1 Zhu J. 2 Zeng N. 3 International Center for Climate and Environment Science, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China Department of Meteorology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20742-2425, USA 07 08 2013 13 15 7607 7618 Copyright: © 2013 Z. H. Chen et al. 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://acp.copernicus.org/articles/13/7607/2013/acp-13-7607-2013.html The full text article is available as a PDF file from https://acp.copernicus.org/articles/13/7607/2013/acp-13-7607-2013.pdf

CO<sub>2</sub> measurements have been combined with simulated CO<sub>2</sub> distributions from a transport model in order to produce the optimal estimates of CO<sub>2</sub> surface fluxes in inverse modeling. However, one persistent problem in using model–observation comparisons for this goal relates to the issue of compatibility. Observations at a single station reflect all underlying processes of various scales. These processes usually cannot be fully resolved by model simulations at the grid points nearest the station due to lack of spatial or temporal resolution or missing processes in the model. In this study the stations in one region were grouped based on the amplitude and phase of the seasonal cycle at each station. The regionally averaged CO<sub>2</sub> at all stations in one region represents the regional CO<sub>2</sub> concentration of this region. The regional CO<sub>2</sub> concentrations from model simulations and observations were used to evaluate the regional model results. The difference of the regional CO<sub>2</sub> concentration between observation and modeled results reflects the uncertainty of the large-scale flux in the region where the grouped stations are. We compared the regional CO<sub>2</sub> concentrations between model results with biospheric fluxes from the Carnegie-Ames-Stanford Approach (CASA) and VEgetation-Global-Atmosphere-Soil (VEGAS) models, and used observations from GLOBALVIEW-CO<sub>2</sub> to evaluate the regional model results. The results show the largest difference of the regionally averaged values between simulations with fluxes from VEGAS and observations is less than 5 ppm for North American boreal, North American temperate, Eurasian boreal, Eurasian temperate and Europe, which is smaller than the largest difference between CASA simulations and observations (more than 5 ppm). There is still a large difference between two model results and observations for the regional CO<sub>2</sub> concentration in the North Atlantic, Indian Ocean, and South Pacific tropics. The regionally averaged CO<sub>2</sub> concentrations will be helpful for comparing CO<sub>2</sub> concentrations from modeled results and observations and evaluating regional surface fluxes from different methods.

 References Baker, D. F., Law, R. M., Gurney, K. R., Rayner, P., Peylin, P., Denning, A. S., Bousquet, P., Bruhwiler, L., Chen, Y. H., Ciais, P., Fung, I. Y., Heimann, M., John, J., Maki, T., Maksyutov, S., Masarie, K., Prather, M., Pak, B., Taguchi, S., and Zhu, Z.: TransCom 3 inversion intercomparison: Impact of transport model errors on the interannual variability of regional CO<sub>2</sub> fluxes, 1988–2003, Global Biogeochem. Cy., 20, GB1002, <a href="http://dx.doi.org/10.1029/2004gb002439">https://doi.org/10.1029/2004gb002439</a>, 2006. Baker, T. R., Phillips, O. L., Malhi, Y., Almeida, S., Arroyo, L., Di Fiore, A., Erwin, T., Higuchi, N., Killeen, T. J., and Laurance, S. G.: Increasing biomass in Amazonian forest plots, Philos. T. Roy. Soc. London, 359, 353–365, <a href="http://dx.doi.org/10.1098/rstb.2003.1422">https://doi.org/10.1098/rstb.2003.1422</a>, 2004. Bishop, J. K. B. and Rossow, W. B.: Spatial and temporal variability of global surface solar irradiance, J. Geophys. Res., 96, 16839–16858, 1991. Bousquet, P.: Regional Changes in Carbon Dioxide Fluxes of Land and Oceans Since 1980, Science, 290, 1342–1346, <a href="http://dx.doi.org/10.1126/science.290.5495.1342">https://doi.org/10.1126/science.290.5495.1342</a>, 2000. Bousquet, P., Ciais, P., Peylin, P., Ramonet, M., and Monfray, P.: Inverse modeling of annual atmospheric CO<sub>2</sub> sources and sinks 1. Method and control inversion, J. Geophys. Res., 104, 26161–26126, 1999. Ciais, P., Rayner, P., Chevallier, F., Bousquet, P., Logan, M., Peylin, P., and Ramonet, M.: Atmospheric inversions for estimating CO<sub>2</sub> fluxes: Methods and perspectives, Climatic Change, 103, 69–92, 2010. Chevallier, F., Ciais, P., Conway, T., Aalto, T., Anderson, B., Bousquet, P., Brunke, E., Ciattaglia, L., Esaki, Y., and Fröhlich, M.: CO<sub>2</sub> surface fluxes at grid point scale estimated from a global 21 year reanalysis of atmospheric measurements, J. Geophys. Res., 115, D21307, <a href="http://dx.doi.org/10.1029/2010JD013887">https://doi.org/10.1029/2010JD013887</a>, 2010. Conway, T., Tans, P., Waterman, L., Thoning, K., Kitzis, D., Masarie, K., and Zhang, N.: Evidence for interannual variability of the carbon cycle from the NOAA/CMDL global air sampling network, J. Geophys. Res, 99, 831–822, 1994. DeFries, R. S. and Townshend, J. R. G.: NDVI-derived land cover classifications at a global scale, Int. J. Remote Sens., 15, 3567–3586, 1994. Enting, I. G.: Inverse problems in atmospheric constituent transport, Cambridge Univ. Pr, 2002. Feng, L., Palmer, P. I., Yang, Y., Yantosca, R. M., Kawa, S. R., Paris, J.-D., Matsueda, H., and Machida, T.: Evaluating a 3-D transport model of atmospheric CO<sub>2</sub> using ground-based, aircraft, and space-borne data, Atmos. Chem. Phys., 11, 2789–2803, <a href="http://dx.doi.org/10.5194/acp-11-2789-2011">https://doi.org/10.5194/acp-11-2789-2011</a>, 2011. GLOBALVIEW-CO2: Cooperative Atmospheric Data Integration Project – Carbon Dioxide., NOAA ESRL, Boulder, Colorado, 2010. Gurney, K. R.: Transcom 3 inversion intercomparison: Model mean results for the estimation of seasonal carbon sources and sinks, Global Biogeochem. Cy., 18, GB1010, <a href="http://dx.doi.org/10.1029/2003gb002111">https://doi.org/10.1029/2003gb002111</a>, 2004. Gurney, K. R., Law, R. M., Denning, A. S., Rayner, P. J., Baker, D., Bousquet, P., Bruhwiler, L., Chen, Y. H., Ciais, P., and Fan, S.: Towards robust regional estimates of CO<sub>2</sub> sources and sinks using atmospheric transport models, Nature, 415, 626–630, 2002. Hansen, J., Ruedy, R., Glascoe, J., and Sato, M.: GISS analysis of surface temperature change, J. Geophys. Res., 104, 30997–31022, 1999. Kaminski, T., Heimann, M., and Giering, R.: A global scale inversion of the transport of CO<sub>2</sub> based on a matrix representation of an atmospheric transport model derived by its adjoint, NATO Challenges of Modern Society, 22, 247–258, 1998. Metzl, N., Brunet, C., Jabaudjan, A., Poisson, A., and Schauer, B.: Summer and winter air–sea CO<sub>2</sub> fluxes in the Southern Ocean, Deep Sea Res. Pt. I, 53, 1548–1563, <a href="http://dx.doi.org/10.1016/j.dsr.2006.07.006">https://doi.org/10.1016/j.dsr.2006.07.006</a>, 2006. Mitchell, T. D. and Jones, P. D.: An improved method of constructing a database of monthly climate observations and associated high-resolution grids, Int. J. Climatol., 25, 693–712, 2005. Nassar, R., Jones, D. B. A., Suntharalingam, P., Chen, J. M., Andres, R. J., Wecht, K. J., Yantosca, R. M., Kulawik, S. S., Bowman, K. W., Worden, J. R., Machida, T., and Matsueda, H.: Modeling global atmospheric CO<sub>2</sub> with improved emission inventories and CO<sub>2</sub> production from the oxidation of other carbon species, Geosci. Model Dev., 3, 689–716, <a href="http://dx.doi.org/10.5194/gmd-3-689-2010">https://doi.org/10.5194/gmd-3-689-2010</a>, 2010. Nassar, R., Jones, D. B. A., Kulawik, S. S., Worden, J. R., Bowman, K. W., Andres, R. J., Suntharalingam, P., Chen, J. M., Brenninkmeijer, C. A. M., Schuck, T. J., Conway, T. J., and Worthy, D. E.: Inverse modeling of CO<sub>2</sub> sources and sinks using satellite observations of CO<sub>2</sub> from TES and surface flask measurements, Atmos. Chem. Phys., 11, 6029–6047, <a href="http://dx.doi.org/10.5194/acp-11-6029-2011">https://doi.org/10.5194/acp-11-6029-2011</a>, 2011. New, M., Hulme, M., and Jones, P.: Representing twentiethcentury space–time climate variability. Part I: development of a 1961–90 mean monthly terrestrial climatology, J. Climate, 12, 829–856,1999. Olsen, S. C.: Differences between surface and column atmospheric CO<sub>2</sub> and implications for carbon cycle research, J. Geophys. Res., 109, D02301, <a href="http://dx.doi.org/10.1029/2003jd003968">https://doi.org/10.1029/2003jd003968</a>, 2004. Peylin, P., Baker, D., Sarmiento, J., Ciais, P., and Bousquet, P.: Influence of transport uncertainty on annual mean and seasonal inversions of atmospheric CO<sub>2</sub> data, J. Geophys. Res, 107, 4385, <a href="http://dx.doi.org/10.1029/2001JD000857">https://doi.org/10.1029/2001JD000857</a>, 2002. Piao, S., Ciais, P., Friedlingstein, P., Peylin, P., Reichstein, M., Luyssaert, S., Margolis, H., Fang, J., Barr, A., Chen, A., Grelle, A., Hollinger, D. Y., Laurila, T., Lindroth, A., Richardson, A. D., and Vesala, T.: Net carbon dioxide losses of northern ecosystems in response to autumn warming, Nature, 451, 49–52, <a href="http://dx.doi.org/10.1038/nature06444">https://doi.org/10.1038/nature06444</a>, 2008. Raich, J .W. and Potter, C. S.: Global patterns of carbon dioxide emissions from soils, Global Biogeochem. Cy., 9, 23–36, 1995. Randerson, J. T., Thompson, M. V., Conway, T. J., Fung, I. Y., and Field, C. B.: The contribution of terrestrial sources and sinks to trends in the seasonal cycle of atmospheric carbon dioxide, Global Biogeochem. Cy., 11, 535–560, 1997. Rödenbeck, C., Conway, T. J., and Langenfelds, R. L.: The effect of systematic measurement errors on atmospheric CO<sub>2</sub> inversions: a quantitative assessment, Atmos. Chem. Phys., 6, 149–161, <a href="http://dx.doi.org/10.5194/acp-6-149-2006">https://doi.org/10.5194/acp-6-149-2006</a>, 2006. Shea, D. J.: Climatological atlas: 1950–1979, Technical Note NCAR TN-269+STR, Nat. Cent. for Atmos. Res., Boulder, Colorado, 1986. Sitch, S., Huntingford, C., Gedney, N., Levy, P., Lomas, M., Piao, S., Betts, R., Ciais, P., Cox, P., and Friedlingstein, P.: Evaluation of the terrestrial carbon cycle, future plant geography and climate-carbon cycle feedbacks using five Dynamic Global Vegetation Models (DGVMs), Glob. Change Biol., 14, 2015–2039, 2008. Stephens, B. B., Gurney, K. R., Tans, P. P., Sweeney, C., Peters, W., Bruhwiler, L., Ciais, P., Ramonet, M., Bousquet, P., and Nakazawa, T.: Weak northern and strong tropical land carbon uptake from vertical profiles of atmospheric CO<sub>2</sub>, Science, 316, 1732, <a href="http://dx.doi.org/10.1126/science.1137004">https://doi.org/10.1126/science.1137004</a>, 2007. Suntharalingam, P.: Improved quantification of Chinese carbon fluxes using CO<sub>2</sub>/CO correlations in Asian outflow, J. Geophys. Res., 109, D18S18, <a href="http://dx.doi.org/10.1029/2003jd004362">https://doi.org/10.1029/2003jd004362</a>, 2004. Suntharalingam, P.: Influence of reduced carbon emissions and oxidation on the distribution of atmospheric CO<sub>2</sub>: Implications for inversion analyses, Global Biogeochem. Cy., 19, GB4003, <a href="http://dx.doi.org/10.1029/2005gb002466">https://doi.org/10.1029/2005gb002466</a>, 2005. Tans, P. P., Conway, T. J., and Nakazawa, T.: Latitudinal distribution of the sources and sinks of atmospheric carbon dioxide derived from surface observations and an atmospheric transport model, J. Geophys. Res., 94, 5151–5172, 1989. Tans, P. P., Fung, I. Y., and Takahashi, T.: Observational constraints on the global atmospheric CO<sub>2</sub> budget, Science, 247, 1431–1438, 1990. Xie, P. and Arkin, P. A.: Analyses of global monthly precipitation using gauge observations, satellite estimates, and numerical model predictions, J. Climate, 9, 840–858, 1996. Zeng, N.: Glacial-interglacial atmospheric CO<sub>2</sub> change – The glacial burial hypothesis, Adv. Atmos. Sci., 20, 677–693, 2003. Zeng, N., Mariotti, A., and Wetzel, P.: Terrestrial mechanisms of interannual CO<sub>2</sub> variability, Global Biogeochem. Cy., 19, GB1016, <a href="http://dx.doi.org/10.1029/2004GB002273">https://doi.org/10.1029/2004GB002273</a>, 2005. Zobler, L. A.: World soil file for global climate modeling, NASA Tech. Memo., 87802, 32 pp., 1986.