References

ACP

Atmospheric Chemistry and Physics

ACP

Atmos. Chem. Phys.

1680-7324

Copernicus Publications

Göttingen, Germany

10.5194/acp-9-7313-2009

Error correlation between CO2 and CO as constraint for CO2 flux inversions using satellite data

Wang

¹ ² Jacob

D. J.

¹ Kopacz

¹ Jones

D. B. A.

³ Suntharalingam

⁴ Fisher

J. A.

¹ Nassar

³ ⁵ Pawson

⁶ Nielsen

J. E.

⁶

School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA

Smithsonian Astrophysical Observatory, Cambridge, MA, USA

Department of Physics, University of Toronto, Toronto, Ontario, Canada

School of Environmental Sciences, University of East Anglia, Norwich, UK

Department of Geography, University of Toronto, Toronto, Ontario, Canada

NASA Goddard Space Flight Center, Global Modeling and Assimilation Office, Greenbelt, MD, USA

02 10 2009

9 19 7313 7323

2009

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/

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The full text article is available as a PDF file from https://acp.copernicus.org/articles/9/7313/2009/acp-9-7313-2009.pdf

Inverse modeling of CO2 satellite observations to better quantify carbon surface fluxes requires a chemical transport model (CTM) to relate the fluxes to the observed column concentrations. CTM transport error is a major source of uncertainty. We show that its effect can be reduced by using CO satellite observations as additional constraint in a joint CO2-CO inversion. CO is measured from space with high precision, is strongly correlated with CO2, and is more sensitive than CO2 to CTM transport errors on synoptic and smaller scales. Exploiting this constraint requires statistics for the CTM transport error correlation between CO2 and CO, which is significantly different from the correlation between the concentrations themselves. We estimate the error correlation globally and for different seasons by a paired-model method (comparing GEOS-Chem CTM simulations of CO2 and CO columns using different assimilated meteorological data sets for the same meteorological year) and a paired-forecast method (comparing 48- vs. 24-h GEOS-5 CTM forecasts of CO2 and CO columns for the same forecast time). We find strong error correlations (r2>0.5) between CO2 and CO columns over much of the extra-tropical Northern Hemisphere throughout the year, and strong consistency between different methods to estimate the error correlation. Application of the averaging kernels used in the retrieval for thermal IR CO measurements weakens the correlation coefficients by 15% on average (mostly due to variability in the averaging kernels) but preserves the large-scale correlation structure. We present a simple inverse modeling application to demonstrate that CO2-CO error correlations can indeed significantly reduce uncertainty on surface carbon fluxes in a joint CO2-CO inversion vs. a CO2-only inversion.

References 1

Andres, R. J., Marland, G., Fung, I., and Matthews, E.: A 1 degree ×1 degree distribution of carbon dioxide emissions from fossil fuel consumption and cement manufacture, 1950-1990. Global Biogeochem. Cy., 10, 3, 419–429, 1996.

Arellano, A. F., Kasibhatla, P. S., Giglio, L., van der Werf, G. R. and Randerson, J.T.: Top-down estimates of global co sources using MOPITT measurements, Geophys. Res. Lett., 31(12), L12108, https://doi.org/10.1029/2003GL018609, 2004.

Arellano, A. F., Kasibhatla, P. S., Giglio, L., van der Werf, G. R., Randerson, J. T., and Collatz, G. J.: Time-dependent inversion estimates of global biomass-burning co emissions using measurement of pollution in the troposphere (MOPITT) measurements, J. Geophys. Res., $111$, D09303, https://doi.org/10.1029/2005JD006613, 2006.

Baker, D. F., Doney, S. C., and Schimel, D. S.: Variational data assimilation for atmospheric CO2. {Tellus B, 58}(Eq. (5)), 359–365, 2006a.

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 CO2 fluxes, 1988–2003, Global Biogeochem. Cy., $20$(Eq. (1)), GB1002, https://doi.org/10.1029/2004GB002439, 2006b.

Baker, D. F., Bosch, H., Doney, S. C., and Schimel, D. S.: Carbon source/sink information provided by column CO2 measurements from the Orbiting Carbon Observatory, Atmos. Chem. Phys. Discuss., 8, 20051–20112, 2008.

Bloom, S. da Silva, A., Dee, D., Bosilovich, M., Chern, J.-D., Pawson,S., Schubert, S., Sienkiewicz, M., Stajner, I., Tan, W.-W., and Wu, M.-L.: Documentaion and validation of the Goddard Earth Observing System (GEOS) data assimilation system – Version 4. Technical report series on Global modeling and data assimilation 104606, 26, 2005.

Bowman, K. W., Rodgers, C. D., Kulawik, S. S., Worden, J., Sarkissian, E., Osterman, G., Steck, T., Lou, M., Eldering, A., Shephard, M., Worden, H., Lampel, M., Clough, S., Brown, P., Rinsland, C., Gunson, M., and Beer, R.: Tropospheric emission spectrometer: Retrieval method and error analysis, IEEE T. Geosci. Remote, $44$, 1297–1307, 2006.

Buchwitz, M., de Beek, R., Bramstedt, K., Noel, S., Bovenmann, H., and Burrows, J. P.: Global carbon monoxide from SCIAMACHY by WFM-DOS, Atmos. Chem. Phys., 4, 1954–1960, 2004.

Buchwitz, M., de Beek, R., Burrows, J. P., Bovensmann, H., Warneke, T., Notholt, J., Meirink, J. F., Goede, A. P. H., Bergamaschi, P., Körner, S., Heimann, M., and Schulz, A.: Atmospheric methane and carbon dioxide from SCIAMACHY satellite data: Initial comparison with chemistry and transport models, Atmos. Chem. Phys., 5, 941–962, 2005a.

Buchwitz, M., de Beek, R., Noël, S., Burrows, J. P., Bovensmann, H., Bremer, H., Bergamaschi, P., Körner, S., and Heimann, M.: Carbon monoxide, methane, and carbon dioxide retrieved from SCIAMACHY by WFM-DOAS: year 2003 initial data set, Atmos. Chem. Phys., 5, 3313–3329, 2005b.

Calbet, X., Schlussel, P., Hultberg, T., Phillips, P., and August, T.: Validation of the operational IASI level 2 processor using airs and ECMWF data, {Atmospheric Remote Sensing, Adv. Space Res., 37}(12), 2299–2305, 2006.

Chahine, M., Barnet, C., Olsen, E. T., Chen, L., and Maddy, E.: On the determination of atmospheric minor gases by the method of vanishing partial derivatives with application to CO2. Geophys. Res. Lett., 32(22), L22803, https://doi.org/10.1029/2005GL024165, 2005.

Chahine, M. T., Chen, L., Dimotakis, P., Jiang, X., Li, Q. B., Olsen, E. T., Pagano, T., Randerson, J., and Yung, Y. L.: Satellite remote sounding of mid-tropospheric CO2. Geophys. Res. Lett., 35(17), L17807, https://doi.org/10.1029/2008GL035022, 2008.

Chevallier, F., Breon, F. M., and Rayner, P. J.: Contribution of the orbiting carbon observatory to the estimation of CO2 sources and sinks: Theoretical study in a variational data assimilation framework, J. Geophys. Res., $112$(D9), D09307, https://doi.org/10.1029/2006JD007375, 2007.

Clerbaux, C., Boynard, A., Clarisse, L., George, M., Hadji-Lazaro, J., Herbin, H., Hurtmans, D., Pommier, M., Razavi, A., Turquety, S., Wespes, C. and Coheur, P.-F.: Monitoring of atmospheric composition using the thermal infrared IASI/MetOp sounder. Atmos. Chem. Phys. Discuss., 9, 8307–8339, 2009.

Conway, T. J., Steele, L. P., and Novelli, P. C.: Correlations among atmospheric CO2, CH4 and CO in the arctic, March 1989, Atmos. Environ. A-Gen., $27$, 2881–2894, 1993.

Crevoisier, C., Chedin, A., and Scott, N. A.: AIRS channel selection for CO2 and other trace-gas retrievals, Q. J. Roy. Meteor. Soc., 129, 2719–274, 2003.

Crisp, D., Atlas, R. M., Breon, F. M., Brown, L. R., Burrows, J. P., Ciais, P., Connor, B. J., Doney, S. C., Fung, I. Y., Jacob, D. J., Miller, C. E., O'Brien, D., Pawson, S., Randerson, J. T., Rayner, P., Salawitch, R. J., Sander, S. P., Sen, B., Stephens, G. L., Tans, P. P., Toon, G. C., Wennberg, P. O., Wofsy, S. C., Yung, Y. L., Kuang, Z., Chudasama, B., Sprague, G., Weiss, B., Pollock, R., Kenyon, D., and Schroll, S.: The orbiting carbon observatory (oco) mission.{ Trace Constitutents in the Troposphere and Lower Stratosphere, Adv. Space Res., 34}(Eq. (4)), 700–709, 2004.

Dils, B., De Maziere, M., Muller, J. F., Blumenstock, T., Buchwitz, M., de Beek, R., Demoulin, P., Duchatelet, P., Fast, H., Frankenberg, C., Gloudemans, A., Griffith, D., Jones, N., Kerzenmacher, T., Kramer, I., Mahieu, E., Mellqvist, J., Mittermeier, R. L., Notholt, J., Rinsland, C. P., Schrijver, H., Smale, D., Strandberg, A., Straume, A. G., Stremme, W., Strong, K., Sussmann, R., Taylor, J., van den Broek, M., Velazco, V., Wagner, T., Warneke, T., Wiacek, A., and Wood, S.: Comparisons between sciamachy and ground-based FTIR data for total columns of CO, CH4, CO2 and N2O, Atmos. Chem. Phys., $6$, 1953–1976, 2006.

Duncan, B. N., Logan, J. A., Bey, I., Megretskaia, I. A., Yantosca, R. M., Novelli, P. C., Jones, N. B., and Rinsland, C. P.: Global budget of CO, 1988–1997: Source estimates and validation with a global model, J. Geophys. Res., $112$(D22), D22301, https://doi.org/10.1029/2007JD008459, 2007.

Emmons, L. K., Edwards, D. P., Deeter, M. N., Gille, J. C., Campos, T., Nedelec, P., Novelli, P., Sachse, G.: Measurements of Pollution In The Troposphere (MOPITT) validation through 2006, Atmos. Chem.Phys., 9(5), 1795–1803, 2009.

Engelen, R. J., Denning, A. S., Gurney, K. R., and TransCom: On error estimation in atmospheric CO2 inversions, J. Geophys. Res., 107(D22), 4635, https://doi.org/10.1029/2002JD002195, 2002.

Engelen, R. J., Denning, A. S., Gurney, K. R., Law, R. M., Rayner, P. J., Baker, D., Bousquet, P., Bruhwiler, L., Chen, Y. H., Ciais, P., Fan, S., Fung, I. Y., Gloor, M., Heimann, M., Higuchi, K., John, J., Maki, T., Maksyutov, S., Masarie, K., Peylin, P., Prather, M., Pak, B. C., Sarmiento, J., Taguchi, S., Takahashi, T., and Yuen, C. W.: On error estimation in atmospheric CO2 inversions, J. Geophys. Res., $111$(D14), D14199, 2006.

Engelen, R. J., Serrar, S., and Chevallier, F.: Four-dimensional data assimilation of atmospheric CO2 using AIRS observations, J. Geophys. Res., 114, D03303, https://doi.org/10.1029/2008JD010739, 2009.

Feng, L., Palmer, P. I., Bosch, H., and Dance, S.: Estimating surface CO2 fluxes from space-borne CO2 dry air mole fraction observations using an ensemble Kalman Filter, Atmos. Chem. Phys., 9, 2619–2633, 2009.

Fiore, A. M., Jacob, D. J., Mathhur, R., and Martin, R. V.: Application of empirical orthogonal functions to evaluate ozone simulations with regional and global models, J. Geophys. Res.-Atmos., 108(D19), https://doi.org/10.1029/2002jd003151, 2003.

Gamnitzer, U., Karstens, U., Kromer, B., Neubert, R. E. M., Meijer, H. A. J., Schroeder, H., and Levin, I.: Carbon monoxide: A quantitative tracer for fossil fuel CO2? J. Geophys. Res., 111(D22), D22302, https://doi.org/10.1029/2005JD006966, 2006.

Gurney, K. R., Law, R. M., Denning, A. S., Rayner, P. J., Baker, D., Bousquet, P., Bruhwiler, L., Chen, Y. H., Ciais, P., Fan, S., Fung, I. Y., Gloor, M., Heimann, M., Higuchi, K., John, J., Maki, T., Maksyutov, S., Masarie, K., Peylin, P., Prather, M., Pak, B. C., Randerson, J., Sarmiento, J., Taguchi, S., Takahashi, T., and Yuen, C. W.: Towards robust regional estimates of CO2 sources and sinks using atmospheric transport models, Nature, 415, 626–630, 2002.

Gurney, K. R., Law, R. M., Denning, A. S., Rayner, P. J., Baker, D., Bousquet, P., Bruhwiler, L., Chen, Y. H., Ciais, P., Fan, S. M., Fung, I. Y., Gloor, M., Heimann, M., Higuchi, K., John, J., Kowalczyk, E., Maki, T., Maksyutov, S., Peylin, P., Prather, M., Pak, B. C., Sarmiento, J., Taguchi, S., Takahashi, T. and Yuen, C. W.: Transcom 3 CO2 inversion intercomparison: 1. Annual mean control results and sensitivity to transport and prior flux information, Tellus B, 55(Eq. (2)), 580–595, 2003.

Gurney, K. R., Law, R. M., Denning, A. S., Rayner, P. J., Pak, B. C., Baker, D., Bousquet, P., Bruhwiler, L., Chen, Y. H., Ciais, P., Fung, I. Y., Heimann, M., John, J., Maki, T., Maksyutov, S., Peylin, P., Prather, M. and Taguchi, S.: Transcom 3 inversion intercomparison: Model mean results for the estimation of seasonal carbon sources and sinks, Global Biogeochem. Cy., $18$(Eq. (1)), GB1010, https://doi.org/10.1029/2003GB002111,2004.

Heald, C. L., Jacob, D. J., Jones, D. B. A., Palmer, P. I., Logan, J. A., Streets, D. G., Sachse, G. W., Gille, J. C., Hoffman, R. N., and Nehrkorn, T.: Comparative inverse analysis of satellite (MOPITT) and aircraft (TRACE-P) observations to estimate Asian sources of carbon monoxide, J. Geophys. Res., 109(D23), D23306, https://doi.org/10.1029/2004JD005185, 2004.

Jones, D. B. A., Bowman, K. W., Palmer, P. I., et al.: Potential of observations from the Tropospheric Emission Spectrometer to constrain continental sources of carbon monoxide, J. Geophys. Res.-Atmos., 108(D24), https://doi.org/10.1029/2003JD003702, 2003.

Kopacz, M., Jacob, D. J., Henze, D. K., Heald, C. L., Streets, D. G., and Zhang, Q.: Comparison of adjoint and analytical Bayesian inversion methods for constraining Asian sources of carbon monoxide using satellite (MOPITT) measurements of CO columns, J. Geophys. Res., 114, D04305, https://doi.org/10.1029/2007JD009264, 2009.

Kulawik, S. S., Jones, D. B. A., Nassar, R., et al.: Characterization of Tropospheric Emission Spectrometer (TES) CO2 for carbon cycle science, Atmos. Chem. Phys., in preparation, 2009.

Logan, J. A., Megretskaia, I. A., Nassar, R., Murray, L. T., Zhang, L., Bowman, K. W., Worden, H. M., and Luo, M.: Effects of the 2006 El Niño on tropospheric composition as revealed by data from the Tropospheric Emission Spectrometer (TES), Geophys. Res. Lett., 35, L03816, https://doi.org/10.1029/2007GL031698, 2008.

Lokupitiya, R. S., Zupanski, D., Denning, A. S., Kawa, S. R., Gurney, K. R., and Zupanski, M.: Estimation of global CO2 fluxes at regional scale using the maximum likelihood ensemble filter, J. Geophys. Res., $113$(D20), D20110, https://doi.org/10.1029/2007JD009679, 2008.

Maddy, E. S., Barnet, C. D., Goldberg, M., Sweeney, C., and Liu, X.: CO2 retrievals from the Atmospheric Infrared Sounder: Methodology and validation, J. Geophys. Res., 113, D11301, https://doi.org/10.1029/2007JD009402, 2008.

McMillan, W. W., Barnet, C., Strow, L., Chahine, M. T., McCourt, M. L., Warner, J. X., Novelli, P. C., Korontzi, S., Maddy, E. S., and Datta, S.: Daily global maps of carbon monoxide from nasa's atmospheric infrared sounder, Geophys. Res. Lett., 32(11), L11801, https://doi.org/10.1029/2004GL021821, 2005.

Miller, C. E., Crisp, D., DeCola, P. L., Olsen, S. C., Randerson, J. T., Michalak, A. M., Alkhaled, A., Rayner, P., Jacob, D. J., Suntharalingam, P., Jones, D. B. A., Denning, A. S., Nicholls, M. E., Doney, S. C., Pawson, S., Boesch, H., Connor, B. J., Fung, I. Y., O'Brien, D., Salawitch, R. J., Sander, S. P., Sen, B., Tans, P., Toon, G. C., Wennberg, P. O., Wofsy, S. C., Yung, Y. L. and Law, R.M.: Precision requirements for space-based X$_{\rm CO_2}$ data, J. Geophys. Res., $112$(D10), D10314, https://doi.org/10.1029/2006JD007659, 2007.

Nassar, R., Jones, D. B. A., Kulawik, S. S., and Chen, J. M.: Use of surface and space-based CO2 observations for inverse modeling of CO2 sources and sinks. 2nd NACP All-investigators meeting, San Diego, CA, USA, 2009.

Olsen, S. C. and Randerson, J. T.: Differences between surface and column atmospheric CO2 and implications for carbon cycle research. J. Geophys. Res., 109(D2), D02301, https://doi.org/10.1029/2003JD003968, 2004.

Ott, L. E., Bacmeister, J., Pawson, S., Pickering, K., Stenchikov, G., Suarez, M., Huntrieser, H., Loewenstein, M., Lopez, J., and Xueref-Remy, I.: Analysis of convective transport and parameter sensitivity in a single column version of the Goddard Earth Observation System, Version 5, General Circulation Model, J. Atmos. Sci., 66(Eq. (3)), 627–646, 2009.

Palmer, P. I., Jacob, D. J., Jones, D. B. A., Heald, C. L., Yantosca, R. M., Logan, J. A., Sachse, G. W. and Streets, D. G.: Inverting for emissions of carbon monoxide from Asia using aircraft observations over the western pacific, J. Geophys. Res., 108(D21), 8828, https://doi.org/10.1029/2003JD003397, 2003.

Palmer, P. I., Suntharalingam, P., Jones, D. B. A., Jacob, D. J., Streets, D. G., Fu, Q. Y., Vay, S. A., and Sachse, G. W.: Using CO2: CO correlations to improve inverse analyses of carbon fluxes, J. Geophys. Res., $111$ (D12), D12318, https://doi.org/10.1029/2005JD006697, 2006.

Parish, D. F. and Derber, J. C.: The National Meteorological Center's spectral statistical interpolation analysis system, Mon. Weather Rev., 120, 1747–1763, 1992.

Patra, P. K., Gurney, K. R., Denning, A. S., Maksyutov, S., Nakazawa, T., Baker, D., Bousquet, P., Bruhwiler, L., Chen, Y. H., Ciais, P., Fan, S. M., Fung, I., Gloor, M., Heimann, M., Higuchi, K., John, J., Law, R. M., Maki, T., Pak, B. C., Peylin, P., Prather, M., Rayner, P. J., Sarmiento, J., Taguchi, S., Takahashi, T., and Yuen, C. W.: Sensitivity of inverse estimation of annual mean CO2 sources and sinks to ocean-only sites versus all-sites observational networks, Geophys. Res. Lett., 33(Eq. (5)), L05814, https://doi.org/10.1029/2005GL025403,2006.

Peters, W., Miller, J. B., Whitaker, J., Denning, A. S., Hirsch, A., Krol, M. C., Zupanski, D., Bruhwiler, L., and Tans, P. P.: An ensemble data assimilation system to estimate CO2 surface fluxes from atmospheric trace gas observations, J. Geophys. Res., 110(D24), D24304, https://doi.org/10.1029/2005JD006157, 2005.

Peylin, P., Baker, D., Sarmiento, J., Ciais, P., and Bousquet, P.: Influence of transport uncertainty on annual mean and seasonal inversions of atmospheric CO2 data, J. Geophys. Res., 107(D19), 4385, https://doi.org/10.1029/2001JD000857, 2002.

Pfister, G., Hess, P. G., Emmons, L. K., Lamarque, J. F., Wiedinmyer, C., Edwards, D. P., Petron, G., Gille, J. C., and Sachsa, G. W.:Quantifying CO emissions from the 2004 Alaska wildfires using MOPITT CO data, Geophys. Res. Lett., 32(11), L11809, https://doi.org/10.1029/2005GL022995, 2005.

Potosnak, M. J., Wofsy, S. C., Denning, A. S., Conway, T. J., Munger, J. W., and Barnes, D. H.: Influence of biotic exchange and combustion sources on atmospheric CO2 concentrations in new england from observations at a forest flux tower, J. Geophys. Res., $104$, 9561–9569, 1999.

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(4), 535–560, 1997.

Rienecker, M. M., Suarez, M. J., Todling, R., Bacmeister, J., Takacs, L., Liu, H.-C., Gu, W., Sienkiewicz, M., Koster, R. D., Gelaro, R., Stajner, I., and Nielsen, J. E.: The GEOS-5 data assimilation system – Documentation of Versions 5.0.1, 5.1.0 and 5.2.0, Technical report series on global modeling and data assimilation, 27, NASA/TM-2008-104606, Vol. 27, 2008.

Rodenbeck, C., Houweling, S., Gloor, M., and Heimann, M.: CO2 flux history 1982-2001 inferred from atmospheric data using a global inversion of atmospheric transport, Atmos. Chem. Phys., 3, 1919–1964, 2003.

Rodgers, C.D. : Inverse Methods for Atmospheric Sounding, World Sci., Singapore, 2000.

Sawa, Y., Matsueda, H., Makino, Y., Inoue, H. Y., Murayama, S., Hirota, M., Tsutsumi, Y., Zaizen, Y., Ikegami, M., and Okada, K.: Aircraft observation of CO2, CO, O3 and H2 over the north pacific during the pace-7 campaign, Tellus B, 56, 2–20, 2004.

Schmitgen, S., Geiss, H., Ciais, P., Neininger, B., Brunet, Y., Reichstein, M., Kley, D., and Volz-Thomas, A.: Carbon dioxide uptake of a forested region in southwest france derived from airborne co2 and co measurements in a quasi-lagrangian experiment, J. Geophys. Res., 109(D14), D14302, https://doi.org/10.1029/2003JD004335, 2004.

Stavrakou, T. and Muller, J. F.: Grid-based versus big region approach for inverting CO emissions using measurement of pollution in the troposphere (MOPITT) data, J. Geophys. Res., 111(D15), D15304, https://doi.org/10.1029/2005JD006896, 2006.

Strow, L. L. and Hannon, S. E.: A 4-year zonal climatology of lower tropospheric CO2 derived from ocean-only Atmospheric Infrared Sounder observations, 113(D18), D18302, https://doi.org/10.1029/2007JD009713, 2008.

Suntharalingam, P., Jacob, D. J., Palmer, P. I., Logan, J. A., Yantosca, R. M., Xiao, Y. P., Evans, M. J., Streets, D. G., Vay, S. L., and Sachse, G. W.: Improved quantification of Chinese carbon fluxes using CO2/CO correlations in Asian outflow, Global Biogeochem. Cy., 109(Eq. (4)), GB4003, https://doi.org/10.1029/2005GB002466, 2005.

Takahashi, T., Feely, R. A., Weiss, R. F., Wanninkhof, R. H., Chipman, D. W., Sutherland, S. C. and Takahashi, T. T.: Global air-sea flux of CO2: An estimate based on measurements of sea-air pCO2 difference, {P. Natl. Acad. Sci. USA, 94}(16), 8292–8299, 1997.

Takegawa, N., Kondo, Y., Koike, M., Chen, G., Machida, T., Watai, T., Blake, D. R., Streets, D. G., Woo, J. H., Carmichael, G. R., Kita, K., Miyazaki, Y., Shirai, T., Liley, J. B. and Ogawa, T.: Removal of NOx and NOy in Asian outflow plumes: Aircraft measurements over the western pacific in January 2002, J. Geophys. Res., 109(D23), D23S04, https://doi.org/10.1029/2004JD004866, 2004.

Tiwari, Y. K., Gloor, M., Engelen, R. J., Chevallier, F., Rodenbeck,C., Korner, S., Peylin, P., Braswell, B. H., and Heimann, M.: Comparing CO2 retrieved from Atmosperic Infrared Sounder with model predictions: Implications for constraining surface fluxes and lower-to-upper troposphere transport, J. Geophys. Res., 111, D17106, https://doi.org/10.1029/2005JD006681, 2006.

van der Werf, G. R., Randerson, J. T., Giglio, L., Collatz, G. J., Kasibhatla, P. S., and Arellano, A. F.: Interannual variability in global biomass burning emissions from 1997 to 2004, Atmos. Chem. Phys., $6$, 3423–3441, 2006.

Washenfelder, R. A., Toon, G. C., Blavier, J. F., Yang, Z., Allen, N. T., Wennberg, P. O., Vay, S. A., Matross, D. M., and Daube, B. C.: Carbon dioxide column abundances at the Wisconsin Tall Tower site, {J. Geophys. Res., 111}(D22), D22305, https://doi.org/10.1029/2006JD007154, 2006.

Yevich, R. and Logan, J. A.: An assessment of biofuel use and burning of agricultural waste in the developing world, Global Biogeochem. Cy., 17(Eq. (4)), 1095, https://doi.org/10.1029/2002GB001952, 2003.

Zupanski, D., Denning, A. S., Uliasz, M., Zupanski, M., Schuh, A. E., Rayner, P. J., Peters, W., and Corbin, K. D.: Carbon flux bias estimation employing maximum likelihood ensemble filter (MLEF), J. Geophys. Res., 112(D17), D17107, https://doi.org/10.1029/2006JD008371, 2007.