Analysis of the Antarctic Ozone Hole in November

The factors responsible for the size of the Antarctic ozone hole in November are analyzed. Comparing two samples of anomalously large and small November ozone holes with respect to 1980-2017 climatology in November, the results show that the anomalously large ozone hole in austral late winter is not a precondition for the anomalously large ozone hole in November. The size of the Antarctic ozone hole in November is mainly influenced by dynamical processes from the end of October to mid-November. During anomalously large November ozone hole events, weaker dynamical ozone transport appears from the end of October to mid-November, which is closely related to planetary wave divergence in the stratosphere between 60 degrees and 90 degrees S. Further analyses indicate that the wave divergence is partially attributed to less upward propagation of planetary waves from the troposphere, which is associated with weak baroclinic disturbances at the end of October. Subsequently, zonal wind speed in the upper stratosphere intensifies, and the distance between the critical layer (U = 0) and wave-reflecting surfaces becomes larger. As a result, more planetary waves are reflected and then wave divergence is enhanced. The processes responsible for the anomalously small Antarctic ozone holes in November are almost opposite to those for the anomalously large Antarctic ozone holes.

Automated summary

The factors influencing the size of the Antarctic ozone hole in November are mainly dynamic processes, with weaker ozone transport related to planetary wave divergence in the stratosphere. Anomalously large ozone holes in November are not always preceded by large holes in late winter, and processes for large and small holes are generally opposite.