Study Of The Impacts Of Dynamical And Chemical Processes On The Antarctic Ozone

Using SLIMCAT three-dimensional offline chemical transport model(CTM),satellite observations and several reanalysis data,we study the mechanisims responsible for the size of Antarctic ozone hole in November,and we revisit the Antarctic ozone recovery during the Antarctic ozone hole period(August to November)from 2000 to2020.The results are as follows.1.By comparing two samples of anomalously large and small November ozone hole with respect to 1980-2017 climatology in November,we study the factors responsible for the size of the Antarctic ozone hole 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 ofOctober to mid-November.During anomalously large November ozone hole events,weaker dynamical ozone transport appears from the end ofOctober to mid-November,which is closely related to planetary wave divergence in the stratosphere between 60°and90°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 ofOctober.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.2.Using SLIMCAT CTM and several satellite observations and reanalysis data,we revisit the Antarctic ozone recovery during the Antarctic ozone hole period(August to November)from 2000 to 2020.Analysis reveals that Antarctic ozone recovery also emerges in August.Moreover,the Antarctic ozone hole area shrinks faster in August than in September.Model simulation shows that total column ozone(TCO)loss(?O₃)in August decreased over 2000-2020,which was attributed to the decrease ofODSs and therefor decrease of chemical ozone loss.However,TCO loss and chemical ozone loss in September still increased over the past two decades.These unexpected trend in September is related to the increase of active cholrine(ClO_x)at 50 and 70 h Pa.Changes of ozone loss rate explain?50%of the positive ClO_x trend in polar cap regions.In addition,changes in the dynamical process can also be a factor responsible for the increasing ClO_x in the polar cap.