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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 9 | Copyright
Atmos. Chem. Phys., 18, 6801-6828, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 16 May 2018

Research article | 16 May 2018

Assessing stratospheric transport in the CMAM30 simulations using ACE-FTS measurements

Felicia Kolonjari1, David A. Plummer2, Kaley A. Walker1, Chris D. Boone3, James W. Elkins4, Michaela I. Hegglin5, Gloria L. Manney6,7, Fred L. Moore8,9, Diane Pendlebury10, Eric A. Ray8,9, Karen H. Rosenlof8, and Gabriele P. Stiller11 Felicia Kolonjari et al.
  • 1Department of Physics, University of Toronto, Toronto, Canada
  • 2Climate Research Division, Environment and Climate Change Canada, Montreal, Canada
  • 3Department of Chemistry, University of Waterloo, Waterloo, Canada
  • 4Global Monitoring Division, NOAA Earth System Research Laboratory, Boulder, USA
  • 5Department of Meteorology, University of Reading, Reading, UK
  • 6NorthWest Research Associates, Socorro, USA
  • 7Department of Physics, New Mexico Institute of Mining and Technology, Socorro, New Mexico, USA
  • 8Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, USA
  • 9Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, USA
  • 10Air Quality Research Division, Environment and Climate Change Canada, Toronto, Canada
  • 11Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany

Abstract. Stratospheric transport in global circulation models and chemistry–climate models is an important component in simulating the recovery of the ozone layer as well as changes in the climate system. The Brewer–Dobson circulation is not well constrained by observations and further investigation is required to resolve uncertainties related to the mechanisms driving the circulation. This study has assessed the specified dynamics mode of the Canadian Middle Atmosphere Model (CMAM30) by comparing to the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) profile measurements of CFC-11 (CCl3F), CFC-12 (CCl2F2), and N2O. In the CMAM30 specified dynamics simulation, the meteorological fields are nudged using the ERA-Interim reanalysis and a specified tracer was employed for each species, with hemispherically defined surface measurements used as the boundary condition. A comprehensive sampling technique along the line of sight of the ACE-FTS measurements has been utilized to allow for direct comparisons between the simulated and measured tracer concentrations. The model consistently overpredicts tracer concentrations of CFC-11, CFC-12, and N2O in the lower stratosphere, particularly in the northern hemispheric winter and spring seasons. The three mixing barriers investigated, including the polar vortex, the extratropical tropopause, and the tropical pipe, show that there are significant inconsistencies between the measurements and the simulations. In particular, the CMAM30 simulation underpredicts mixing efficiency in the tropical lower stratosphere during the June–July–August season.

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We used satellite observations and model simulations of CFC-11, CFC-12, and N2O to investigate stratospheric transport, which is important for predicting the recovery of the ozone layer and future climate. We found that sampling can impact results and that the model consistently overestimates concentrations of these gases in the lower stratosphere, consistent with a too rapid Brewer–Dobson circulation. An issue with mixing in the tropical lower stratosphere in June–July–August was also found.
We used satellite observations and model simulations of CFC-11, CFC-12, and N2O to investigate...