Simulating the Antarctic stratospheric vortex transport barrier: comparing the Unified Model to reanalysis

  • Chris CameronEmail author
  • Gregory E. Bodeker
  • Jonathan P. Conway
  • Stephen Stuart
  • James Renwick


An assessment has been made of the ability of the UK Met Office Unified Model (UM) to simulate the Antarctic stratospheric circumpolar vortex and, in particular, the extent to which the vortex acts as a barrier to meridional transport. It is important that models simulate this barrier well as it determines spatial gradients in radiatively active gases, such as ozone, which then determine the spatial morphology of the radiative forcing field. The assessment was made by comparing metrics of meridional impermeability calculated from dynamical fields extracted from UM simulations and from analogous fields obtained from NCEP-CFSR reanalysis. Two different UM configurations were assessed: global atmosphere 3.0 (GA3.0) using the New Dynamics dynamical core, and GA7.0 using the newer ENDGame dynamical core, with both versions run at N96 resolution (1.25\(^{\circ }\) latitude by 1.875\(^{\circ }\) longitude). The GA7.0 configuration appears to better simulate the dynamical isolation of the Antarctic stratospheric vortex in the lower stratosphere up to about 600 K, while GA3.0 provides a better simulation in the upper stratosphere. However, neither UM configuration simulates the same degree of dynamical isolation suggested by the reanalysis. In particular the UM configurations produce a wider and more poleward meridional band of high wind-speed and steep PV gradients when compared with the NCEP-CFSR reanalysis, leading to a stronger barrier in GA7.0 and a weaker barrier in GA3.0. Possible causes of discrepancies between model simulations and reanalysis and between the two model configurations are discussed. It is pointed out that further work is needed to identify ways of resolving these discrepancies in model simulations.


Antarctic stratospheric circumpolar vortex Meridional impermeability Dynamical isolation Unified Model NCEP-CFSR reanalysis Ozone hole Global climate models Climate change 



We would like to acknowledge the support of the Marsden Fund (contract BDS1401) of the Royal Society of New Zealand in making this research possible. We also acknowledge the contribution of high-performance computing facilities from the New Zealand eScience Infrastructure (NeSI), Sam Dean, Jonny Williams and Olaf Morgenstern from NIWA, and João Teixeira from the UK Met Office. High-resolution SST and sea ice data were provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Bodeker ScientificAlexandraNew Zealand
  2. 2.NIWAWellingtonNew Zealand
  3. 3.Victoria University of WellingtonWellingtonNew Zealand

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