Asymmetry in the Southern Hemisphere stratospheric ozone hole is important due to both direct radiative heating and its effect ondynamics. It is also a strong indicator of the underlying quality of the stratospheric dynamics of a climate model. We investigatethe simulation of the zonal asymmetry in ozone in the NIWA-UKCA atmosphere–ocean chemistry–climate model using ellipticaldiagnostics, a methodology used for the first time in this subject area. During spring, the region most depleted in ozone isdisplaced from the pole toward South America based on ERA-Interim and the model output. The model correctly simulates the directionof this displacement but significantly underestimates its magnitude. The model shows that as ozone becomes increasingly depleted overthe late 20th century this asymmetry in the ozone distribution moves west, before moving east as polar ozone recovers over thecourse of the 21st century. Comparison with model runs in which ozone-depleting substances are held fixed at pre-ozone-hole levelsshows that this shift is primarily a function of the magnitude of ozone depletion, although increases in greenhouse gases also have someeffect.
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