ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-9-2873-2009 Technical Note: Feasibility of CO<sub>2</sub> profile retrieval from limb viewing solar occultation made by the ACE-FTS instrument Foucher P. Y. 1 Chédin A. 1 Dufour G. 2 Capelle V. 1 Boone C. D. 3 Bernath P. 3 4 Laboratoire de Météorologie Dynamique/Institut Pierre Simon Laplace, Ecole Polytechnique, 91128 Palaiseau, France Laboratoire Inter-universitaire des Systèmes Atmosphériques, Faculté des Sciences et Technologies, 61 avenue du Général de Gaulle, 94010 Créteil, France Department of Chemistry, University of Waterloo, Ontario, N2L3G1, Canada Department of Chemistry, University of York, Heslington, York, YO105DD, UK 30 04 2009 9 8 2873 2890 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.net/9/2873/2009/acp-9-2873-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/2873/2009/acp-9-2873-2009.pdf

Major limitations of our present knowledge of the global distribution of CO<sub>2</sub> in the atmosphere are the uncertainty in atmospheric transport mixing and the sparseness of in situ concentration measurements. Limb viewing space-borne sounders, observing the atmosphere along tangential optical paths, offer a vertical resolution of a few kilometers for profiles, which is much better than currently flying or planned nadir sounding instruments can achieve. In this paper, we analyse the feasibility of obtaining CO<sub>2</sub> vertical profiles in the 5–25 km altitude range from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS, launched in August 2003), high spectral resolution solar occultation measurements. Two main difficulties must be overcome: (i) the accurate determination of the instrument pointing parameters (tangent heights) and pressure/temperature profiles independently from an a priori CO<sub>2</sub> profile, and (ii) the potential impact of uncertainties in the temperature knowledge on the retrieved CO<sub>2</sub> profile. The first difficulty has been solved using the \N collision-induced continuum absorption near 4 μm to determine tangent heights, pressure and temperature from the ACE-FTS spectra. The second difficulty has been solved by a careful selection of CO<sub>2</sub> spectral micro-windows. Retrievals using synthetic spectra made under realistic simulation conditions show a vertical resolution close to 2.5 km and accuracy of the order of 2 ppm after averaging over 25 profiles. These results open the way to promising studies of transport mechanisms and carbon fluxes from the ACE-FTS measurements. First CO<sub>2</sub> vertical profiles retrieved from real ACE-FTS occultations shown in this paper confirm the robustness of the method and applicability to real measurements.

 References Anderson, B., Gregory, G., Collins, J. J., Sachse, G., Conway, T., and Whiting, G.: Airborne observations of spatial and temporal variability of tropospheric carbon dioxide, J. Geophys. Res., 101, 1985–1997, 1996. Andrew, A. E., Boering, K. A., Daube, B. C.,Wofsy, S. C., Loewenstein, M., Jost, H., Podolske, J. R.,Webster, C. R., Herman, R. L., Scott, D. C., Flesch, G. J., Moyer, E. J., Elkins, J. W., Dutton, G. S., Hurst, D. F., Moore, F. L., Ray, E. A., Romashkin, P. A., and Strahan, S. E.: Mean ages of stratospheric air derived from in situ observations of \CO, \CH, and \NX, J. Geophys. Res., 106, 32295–32314, 2001. 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.: TransCom3 inversion intercomparison: Interannual variability of regional \CO fluxes, Global Biogeochem. Cy., 1988–2003, doi:10.1029/2004GB002439, 2006. Bernath, P. F.: Atmospheric Chemistry Experiment (ACE): Analytical Chemistry from Orbit, Trends Anal. Chem., 25, 647–654, 2006. Bernath, P. F., McElroy, C. T., Abrams, M. C., Boone, C. D., Butler, M., Camy-Peyret, C., Carleer, M., Clerbaux, C., Coheur, P.-F., Colin, R., DeCola, P., DeMaziere, M., Drummond, J. R., Dufour, D., Evans, W. F. J., Fast, H., Fussen, D., Gilbert, K., Jennings, D. E., Llewellyn, E. J., Lowe, R. P., Mahieu, E., Mc- Connel, J. C., McHugh, M., Mcleod, S. D., Michaud, R., Midwinter, C., Nassar, R., Nichitiu, F., Nowland, C., Rinsland, C. P., Rochon, Y. J., Rowlands, N., Semeniuxk, K., Simon, P., Skelton, R., Sloan, J. J., Soucy, M. A., Strong, K., Tremblay, P., Turnbull, D., Walker, K. A., Walkty, I., Wardle, D. A., Wehrle, V., Zander, R., and Zou, T.: Atmospheric Chemistry Experiment (ACE): Misson overview, Geophys. Res. Lett., 32, L15S01, doi:10.1029/2005GLO22386, 2005. Bönisch, H., Hoor, P., Gurk, C., Feng, W., Chipperfield, M., Engel, A., and Bregman, B.: Model evaluation of \CO and §F in the extratropical UT/LS region, J. Geophys. Res., 113, D06101, doi:10.1029/2007JD008829, 2008. Boone, C. D., Nassar, R.,Walker, K. A., Rochon, Y., Mcleod, S. D., Rinsland, C. P., and Bernath, P. F.: Retrievals for the Atmospheric Chemistry Experiment Fourier-Transform Spectrometrer, Appl. Opt., 44, 7218–7231, 2005. Brenninkmeijer, C. A. M., Crutzen, P. J., Fischer, H., Gsten, H., Hans, W., Heinrich, G., Heintzenberg, J., Hermann, M., Immelmann, T., Kersting, D., Maiss, M., Nolle, M., Pitscheider, A., Pohlkamp, H., Scharffe, D., Specht, K., and Wiedensohler, A.: CARIBIC: Civil Aircraft for Global Measurement of Trace Gases and Aerosols in the Tropopause Region, J. Atmos. Ocean. Tech., 16, 1373–1383, 1999. Buchwitz, M., de Beek, R., Noel, S., Burrowsandi, J. P., Bovensmann, H., Bremer, H., Bergamaschi, P., Krner, S., and Heimann, M.: Carbon monoxide, methane and carbon dioxide columns retrieved from SCIAMACHY by WFM-DOAS: year 2003 initial data set., Atmos. Chem. Phys., 5, 3313–3329, 2005. Chédin, A., Serrar, S., Armante, R., Scott, N. A., and Hollingsworth, A.: Signatures of annual and seasonal variations of \CO and other greenhouse gases from comparisons between NOAA/TOVS observations and model simulations, J. Clim., 15, 95–116, 2002. Chédin, A., Serrar S., Scott, N. A., Crevoisier, C., and Armante, R.: First global measurement of mid-tropospheric \CO from NOAA polar satellites : the tropical zone, J. Geophys. Res., 108, 4581, doi:10.1029/2003JD003439, 2003a. Chédin, A., Saunders, R., Hollingsworth, A., Scott, N. A., Matricardi, M., Etcheto, J., Clerbaux, C., Armante, R., and Crevoisier, C.: The feasibility of monitoring \CO from high-resolution infrared sounders, J. Geophys. Res., 108, 4064, doi:10.1029/2001JD00144, 2003b. Crevoisier, C., Heilliette, S., Chédin, A., Serrar, S., Armante, R., and Scott, N. A.: Midtropospheric \CO concentration retrieval from AIRS observations in the tropics, Geophys. Res. Lett., 31, L17106, doi:10.1029/2004GL020141, 2004. Dudhia, A., Jay, V. L., and Rodgers, C. D.: Microwindow selection for high-spectral-resolution sounders, Appl. Opt., 41, 3665–3673, 2002. Engel, A., Bönish, H., Brunner, D., Fischer, H., Franke, H., G¨unter, G., Gurk, C., Hegglin, M., Hoor, P., Königstedt, R., Krebach, M., Maser, R., Parchatka, U., Peter, T., Schell, D., Schiller, C., Schmidt, U., Spelten, N., Szabo, T., Weers, U., Wernli, H., Wetter, T., and Wirth, V.: Highly resolved observations of trace gases in the lowermost stratosphere from the Spurt project: an overview, Atmos. Chem. Phys., 6, 283–301, 2006. Engelen, R. J. and McNally, A. P.: Estimating atmospheric \CO from advanced infrared satellite radiances within an operational four-dimensional variational (4D-Var) data assimilation system: Results and validation, J. Geophys. Res., 110, D18305, doi:10.1029/2005JD005982, 2005. Gelb, A.: Applied Optimal Estimation, M.I.T. Press, 180–229, 1974. 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 \CO\ sources and sinks using atmospheric transport models, Nature, 415, 626–630, 2002. Hegglin, M. I., Boone, C. D., Manney, G. L., Shephered, T. G., Walker, K. A., Bernath, P. F., Daffer, W. H., Hoor, P., and Schiller, C.: Validation of ACE-FTS satellite data in the upper troposphere/lower stratosphere (UTLS) using non-coincident measurements, Atmos. Chem. Phys., 8, 1483–1499, 2008. Horowitz, L. W., Walters, S., Mauzerall, D. L., Emmons, L. K., Rasch, P. J., Granier, C., Tie, X., Lamarque, J. F., Schultz, M. G., Tyndall, G. S., Orlando, J. J., and Brasseu, G. P.: A global simulation of tropospheric ozone and related tracers: Description and evaluation of MOZART, version 2, J. Geophys. Res., 108, 4784, doi:10.1029/2002JD002853, 2003. Jacquinet-Husson, N., Scott, N. A., Chédin, A., Crépeau, L., Armante, R., Capelle, V., Orphal, J., Coustenis, A., Boonne, C., Poulet-Crovisier, N., Barbe, A., Birk, M., Brown, L. R., Camy- Peyret, C., Claveau, C., Chance, K., Christidis, N., Clerbaux, C., Coheur, P. F., Dana, V., Daumont, L., Backer-Barilly, M. R. D., Lonardo, G. D., Flaud, J. M., Goldman, A., Hamdouni, A., Hess, M., Hurley, M. D., Jacquemart, D., Kleiner, I., Kpke, P., Mandin, J. Y., Massie, S., Mikhailenko, S., Nemtchinov, V., Nikitin, A., Newnham, D., Perrin, A., Perevalov, V., Pinnock, S., Rgalia-Jarlot, L., Rinsland, C., Rublev, A., Schreier, F., Schult, L., Smithu, K. M., Tashkun, S. A., Teffo, J. L., Toth, R. A., Tyuterev, V. G., Auwera, J. V., Varanasi, P., and Wagner, G.: The GEISA spectroscopic database: Current and future archive for Earth and planetary atmosphere studies, JQSRT, 100, 1043–1059, 2008. Koner, P. K. and Drummond, J. R.: Atmospheric trace gases profile retrievals using the nonlinear regularized total least square method, JQSRT, 109, 2045–2059, doi:10.1016/j.jqsrt.2008.02.014, 2008. Lafferty, W. J., Solodov, A. M., Weber, A., Olson, W. B., and Hartmann, J.-M.: Infrared collision-induced absorption by \N near 4.3 μm for atmospheric applications: measurements and empirical modeling, Appl. Opt., 35, 5911–5917, 1996. Levenberg, K. :A Method for the Solution of Certain Non-Linear Problems in Least Squares. The Quarterly of Applied Mathematics, 2, 164–168, 1944. Matsueda, H., Taguchi, S., Inoue, H. Y., and Ishii, M.: A large impact of tropical biomass burning on \C and \CO in the upper troposphere, Science China Press, 45, 116–125, 2002. Marquardt, D.: An Algorithm for Least-Squares Estimation of Nonlinear Parameters. SIAM J. Appl. Math., 11, 431–441, doi:10.1137/0111030, 1963. Olsen, S. C. and Randerson, J. T.: Differences between surface and column atmospheric \CO and implications for carbon cycle research, J. Geophys. Res., 109, D02301, doi:10.1029/2003JD003968, 2004. Pak, B. C. and Prather, M. J.: \CO source inversions using satellite observations of the upper troposphere, Geophys. Res. Lett., 28, 4571–4574, 2001. Park, J. H.: Atmospheric \CO monitoring from space, Appl. Opt., 36, 2701–2712, 1997. Patra, P. K., Maksyutov, S., Sasano, Y., Nakajima, H., Inoue, G., and Nakazawa, T.: An evaluation of \CO observations with Solar Occultation FTS for Inclined-Orbit Satellite sensor for surface source inversion, J. Geophys. Res., 108(D24), 4759, doi:10.1029/2003JD003661, 2003. Phillips, D. L.:A Technique for the Numerical Solution of Certain Integral Equations of the First Kind, J. Assoc. Comput. Mach., 9, 84–97, 1962. Plumb, R.: A "tropical pipe" model of stratospheric transport, J. Geophys. Res., 301, 3957–3972, 1996. Plumb, R. and Ko, M.: Interrelationships between mixing ratios of long-lived stratosphere constituents, J. Geophys. Res., 97, 10145–10156, 1992. Rodgers, C. D.: Inverse methods for atmospheric sounding. Theory and practice, World scientific, Singapore, 90–98, 2000. Sawa, Y. , Machida, T. and Matsueda, H.: Seasonal variations of CO2 near the tropopause observed by commercial aircraft, J. Geophys. Res., 113, D23301, doi:10.1029/2008JD010568, 2008. Scott, N. A.: A direct method of computation of transmission function of an inhomogeneous gaseous medium : description of the method and influence of various factor, JQSRT, 14, 691–707, 1974. Scott, N. A. and Chédin, A.: A fast line-by-line method for atmospheric absorption computation: The Automatized Atmospheric Absorption Atlas, J.Appl.Meteorol., 20, 801–812, 1981. Shia, R. L., Liang, M. C., Miller, C. E., and Yung, Y. L.: \CO in the upper troposphere: Influence of stratospheretroposphere exchange, Geophys. Res. Lett., 33, L1481, doi:10.1029/2006GL026141, 2006. Steck, T.: Methods for determining regularization for atmospheric retrieval problems, Appl. Opt., 41, 1788-1797, 2002. Tikhonov, A. N.: On the regularization of ill-posed problems. Dokl. Akad. Nauk SSSR, 153, 49–52; MR, 28, 5577; Soviet Math. Dokl., 4, 1624–1627, 1963. Twomey, S.: On the Numerical Solution of Fredholm Integral Equations of the First Kind by the Inversion of the Linear System Produced by Quadrature, J. Assoc. Comp. Mach., 10, 97–101, 1963. von Clarmann, T. and Echle, G.: Selection of optimized microwindows for atmospheric spectroscopy, Appl. Opt., 37, 7661–7669, 1998. von Clarmann, T., Glatthor, N., Grabowski, U., Hopfner, M., Kellmann, S., Kiefer, M., Linden, A., Tsidu, G. M., Milz, M., Steck, T., Stiller, G. P., Wang, D. Y., Fischer, H., Funke, B., and Gil- López-Puerta, S.: Retrieval of temperature and tangent altitude pointing from limb emission spectra recorded from space by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), J. Geophys. Res., 108, 4736–4750, 2003.