Transport of SF6 and 14CO2 in the atmospheric general circulation model ECHAM4

Article English OPEN
KJELLSTRÖM, ERIK ; FEICHTER, JOHANN ; HOFFMAN, GEORG (2011)

Two tracers, SF6 with sources at the earth's surface and 14CO2 with a source in the lower stratosphere, are used to investigate the simulation of global scale transport in an atmospheric general circulation model. The simulated mixing ratios of SF6 in the troposphere are generally in close agreement to observations revealing a realistic description of the large scale tropospheric transport. The interhemispheric exchange time for SF6 is calculated to be 0.9 years, indicating a slightly too strong interhemispheric exchange. In the lowermost stratosphere the simulated vertical gradient of SF6 is in good agreement with observations within the 1st 4 to 5 km above the tropopause indicating that the flux from the troposphere to the lowermost stratosphere is captured by the model. On the other hand, downward transport of 14CO2 from the stratosphere into the troposphere is found to be overestimated. From a comparison with observations it is concluded that it is the downward transport in the subtropics that is overestimated, at high latitudes the vertical gradients in the tropopause region are close to observations. Finally, the tracer tests show that the transport into the uppermost two levels, above 20 km, is underestimated as these levels serve as sponge layers and not as layers with a reasonable transport. Consequently, the tracer concentrations in that altitude interval are underestimated, by up to a factor 2.DOI: 10.1034/j.1600-0889.2000.00882.x
  • References (47)
    47 references, page 1 of 5

    Brinkop, S. and Sausen, R. 1997. A finite diVerence approximation for convective transports which maintains positive tracer concentrations. Beitr. Phys. Atmosph. 70, 245-248.

    Broecker, W., Peng, T.-H., Ostlund, G. and Stuiver, M. 1985. The distribution of bomb radiocarbon in the ocean. J. Geophys. Res. 90, 6953-6970.

    Crutzen, P. 1976. The possible importance of CSO for the sulfate layer of the stratosphere. Geophys. Res. L ett. 3, 73-76.

    DeMore, W. B., Sander, S. P., Golden, D. M., Hampson, R. F., Kurylo, M. J., Howard, C. J., Ravishankara, A. R., Kolb, C. E. and Molina, M. J. 1997. Chemical kinetics and photochemical data for use in stratosphere modeling. Evaluation number 12. JPL publication 97-4, Jet Propulsion Laboratory, Pasadena, Calif., USA.

    Denning, A. S., Holzer, M., Gurney, K. R., Heimann, M., Law, R. M., Rayner, P. R., Fung, I. Y., Fan, S.-M., Taguchi, S., Friedlingstein, P., Balkanski, Y., Taylor, J., Maiss, M. and Levin, I. 1999. Three-dimensional transport and concentration of SF6: a model intercomparison study (Transcom 2). T ellus 51, 266-297.

    Elkins, J. W., Fahey, D. W., Gilligan, J. M., Dutton, G. S., Baring, T. J., Volk, C. M., Dunn, R. E., Myers, R. C., Montzka, S. A., Wamsley, P. R., Hayden, A. H., Butler, J. H., Thompson, T. M., Swanson, T. H., Dlugokencky, E. J., Novelli, P. C., Hurst, D. F., Lobert, J. M., Ciciora, S. J., McLaughlin, R. J., Thompson, T. L., Winkler, R. H., Fraser, P. J., Steele, L. D. and Lucarelli, M. P. 1996. Airborne gas chromatograph for in situ measurements of long-lived species in the upper troposphere and lower stratosphere. Geophys. Res. L ett. 23, 347-350.

    Feichter, J. and Crutzen, P. J. 1990. Parameterization of vertical transport due to deep cumulus convection in a global transport model and its evaluation with 222Radon measurements. T ellus 42, 100-117.

    Geller, L. S., Elkins, J. W., Lobert, J. M., Clarke, A. D., Hurst, D. F., Butler, J. H. and Myers, R. C. 1997. Tropospheric SF6: observed latitudinal distribution and trends, derived emissions and interhemispheric exchange time. Geophys. Res. L ett. 24, 675-678.

    Grewe, V. and Dameris, M. 1996. The large-scale massexchange between stratosphere and troposphere in the ECHAM3 model. In Staniforth, A. (ed.): Research activities in atmospheric and oceanic modelling. CAS/ JSC working group on numerical experimentation. Report No. 23 WMO/TD No. 734.7.21-7.22, Geneva, Switzerland.

    Hall, T. M. and Plumb, R. A. 1994. Age as a diagnostic of stratospheric transport. J. Geophys. Res. 99, 1059-1070.

  • Related Research Results (1)
  • Metrics
    No metrics available
Share - Bookmark