S. E. Strahan, et al.
Using transport diagnostics to understand chemistry climate model ozone simulations
Journal of Geophysical Research: Atmospheres, 116(17), D17302, 2011; doi: 10.1029/2010JD015360
N2O 15NNO N15NO N218O N217O Middle atmosphere General circulation Global climate models composition model evaluation stratospheric transport


[1] We use observations of N2O and mean age to identify realistic transport in models in order to explain their ozone predictions. The results are applied to 15 chemistry climate models (CCMs) participating in the 2010 World Meteorological Organization ozone assessment. Comparison of the observed and simulated N2O, mean age and their compact correlation identifies models with fast or slow circulations and reveals details of model ascent and tropical isolation. This process-oriented diagnostic is more useful than mean age alone because it identifies models with compensating transport deficiencies that produce fortuitous agreement with mean age. The diagnosed model transport behavior is related to a model's ability to produce realistic lower stratosphere (LS) O3 profiles. Models with the greatest tropical transport problems compare poorly with O3 observations. Models with the most realistic LS transport agree more closely with LS observations and each other. We incorporate the results of the chemistry evaluations in the Stratospheric Processes and their Role in Climate (SPARC) CCMVal Report to explain the range of CCM predictions for the return-to-1980 dates for global (60°S–60°N) and Antarctic column ozone. Antarctic O3 return dates are generally correlated with vortex Cly levels, and vortex Cly is generally correlated with the model's circulation, although model Cl chemistry and conservation problems also have a significant effect on return date. In both regions, models with good LS transport and chemistry produce a smaller range of predictions for the return-to-1980 ozone values. This study suggests that the current range of predicted return dates is unnecessarily broad due to identifiable model deficiencies.


  author = "S. E. Strahan and A. R. Douglass and R. S. Stolarski and H. Akiyoshi and S. Bekki and P. Braesicke and N. Butchart and M. P. Chipperfield and D. Cugnet and S. Dhomse and S. M. Frith and A. Gettelman and S. C. Hardiman and D. E. Kinnison and J.-F. Lamarque and E. Mancini and M. Marchand and M. Michou and O. Morgenstern and T. Nakamura and D. Olivié and S. Pawson and G. Pitari and D. A. Plummer and J. A. Pyle and J. F. Scinocca and T. G. Shepherd and K. Shibata and D. Smale and H. Teyssèdre and W. Tian and Y. Yamashita",
  title = "Using transport diagnostics to understand chemistry climate model ozone simulations",
  year = 2011,
  journal = "Journal of Geophysical Research: Atmospheres",
  volume = 116,
  number = 17,
  pages = "D17302",
  month = "Sep",
  keywords = "N2O, 15NNO, N15NO, N218O, N217O, Middle atmosphere, General circulation, Global climate models, composition, model evaluation, stratospheric transport",
  doi = "10.1029/2010JD015360",
  url = ""
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