The Effects Of Pacific SST And Arctic Sea Ice On Arctic Stratospheric Ozone Variations

Using TOMS and MLS satellite observations,MERRA and ERA-Interim reanalysis data,as well as a chemistry transport model(SLIMCAT),the characteristics of Arctic stratospheric ozone variation and the role of chemical process on it are analyzed via model simulations and case analysis.Meanwhile,the effects of Sea Surface Temperature(SST)in the Pacific Ocean,especially ENSO and the SST anomaly in North Pacific,and variations of Arctic stratospheric ozone caused by anomalies of Arctic ice cover and its mechanism are also investigated.The results are as follows:1.By combining ozone concentration data from SLMCAT model simulation,TOMS satellite observation and MERRA reanalysis data,we chose the year 1997 and 2011 as cases of the Arctic stratospheric ozone anomaly.The results show that the values of total column ozone(TCO)were abnormal low over Arctic in both March 1997 and March 2011 which are the lowest in the last three decades.To be specific,the total column ozone(TCO)anomalies over Arctic in both years were ~100 DU and spatial column ozone anomalies between 200 hPa and 30 hPa can account for ~80% of the TCO anomalies.The TCO in 1997 and 2011 began to recover from April,while the recovery rate in 2011 is faster than that in 1997.The analysis about the effect of chemical process on the ozone changes shows that Arctic stratospheric temperature was abnormally low in March in these two years,it led to the formation of polar stratospheric clouds(PSCs)which has high catalytic efficiency to ozone loss and contributed to a large amount of active chlorine being released on PSCs surface,and finally intensified the depletion of ozone.This process is more significant in spring 2011,lower temperature over Arctic region and more PSCs even type II PSCs formed which accelerated ozone chemical loss.2.Using HadlSST and ERA-Interim reanalysis data,the effect of SST anomalies in different regions of Pacific on Arctic stratospheric ozone,the characteristics and mechanism of the impact of ENSO on Arctic stratospheric ozone,and the process and mechanism of Arctic stratospheric ozone influenced by the dynamical anomaly that caused by SST anomaly in North Pacific Ocean are analyzed.It is found that the extremely low Arctic TCO events in 1997 and 2011 are both related to the decrease of planetary waves in stratosphere because of La Ni?a activities in the last winters.The decrease results in stronger Arctic polar vortex,lower stratospheric temperature and more ozone chemical loss.The anomalies of TCO in the Arctic stratospheric between 1 hPa and 30 hPa in both years are mainly caused by dynamical process.Specifically,the weakening of BDC results in the decrease of dynamical transportation from low latitudes to polar in stratosphere.Thus,there is less air with high concentration of ozone being transported from low latitudes to polar,leading to a negative anomaly of TCO between 1 hPa and 30 hPa.Note that the decrease of ozone in UTLS region over Arctic in 2011 is much stronger than that in 1997.It is because that a stronger La Ni?a event in 2010 and a higher SST in North Pacific in 2011 led to a lower Aleutian low.The weaker Aleutian low results in reduced stratospheric wave activities and colder Arctic vortex which induced more PSCs and even type II PSCs and finally accelerated the ozone chemical loss in spring 2011.Our study also shows that low(high)SST in North Pacific corresponds to the weakening(strengthen)of Polar vortex and then increase(decrease)of ozone in Arctic spring.3.Nino3 index,HadlSST and sea ice cover for the period 1979-2011 are used to analyze the impact of the La Ni?a events,the anomalies of the SST over the North Pacific,and sea ice variation over Arctic on Arctic stratospheric ozone.The results show that,dynamic processes such as strong El Ni?o events happened in last winter,the winter SST anomalies in North Pacific and Arctic ice cover anomaly especially over Barents sea and kara sea(B-K)ice loss can result in transport of planetary wave from troposphere to stratosphere decreased,Polar vortex temperature lowered,and the depletion of ozone in the Stratospheric Arctic accelerated.Arctic ice cover increased in 1997 and SST in North Pacific increased in 2011 both led to planetary wave weakened and Arctic Polar vortex strengthened.The strong Arctic stratospheric ozone loss in 1997 and 2011 were attributed by the combined influence of it and La Ni?a.