Impacts Of North Pacific SST And Arctic Oscillation On Interannual Variations Of Arctic Stratospheric Ozone

We respectively examined the relationship between sea surface temperatures anomalies(SST)in the North Pacific and Arctic Oscillation(AO)and the concentration of stratospheric ozone in the northern hemisphere using Modern-Era Retrospective Analysis for Research and Applications version 2(MERRA-2)reanalysis data,Microwave Limb Sounder(MLS)satellite data,and Whole Atmosphere Community Climate Model(WACCM)model.And we also studied the combined effect of SST in the Northern Pacific and AO on the lower stratospheric ozone concentration over the Arctic.The results are given as follows:(1)The concentration of stratospheric ozone can be changed by the principal mode of the North Pacific SST(negative SST anomalies in the North Pacific).During the positive phases of the North Pacific SST,there are negative and zonally asymmetrical ozone anomalies in the lower stratosphere over the Arctic,but positive ozone anomalies in the lower stratosphere at mid-latitudes.SST in the North Pacific could explain about 20% of the variance of ozone concentrations in the Arctic lower stratosphere.Negative SST anomalies(SSTA)in the North Pacific tend to cause a strengthened Western Pacific teleconnection pattern,which results in more planetary wavenumber-1 and-2 waves propagating into the stratosphere.On the one hand,when the phase of SST in the North Pacific is positive,the branch of the Brewer–Dobson circulation(BDC)in the mid-latitude stratosphere strengthens,but its branch in the stratosphere over the Arctic weakens.This leads to decreased ozone anomalies in the Arctic lower stratosphere and increased ozone anomalies in the lower stratosphere at mid-latitudes.On the other hand,the zonally asymmetrical distribution of ozone related to the positive phase of SSTA in the North Pacific may be caused by the shifting and strengthening of the stratospheric Arctic vortex.(2)There are two negative anomaly centers respectively located in the middle stratosphere(?30 h Pa)and upper troposphere-lower stratosphere(UTLS)in every month over the Arctic,but there is a positive anomaly center at 70-100 h Pa in the North Pacific and North Atlantic in December during the positive AO phases on the interannual time scales.Further analysis shows that poleward shifting of 200 h Pa subtropical jet in December and weakening of 200 h Pa subtropical jet in January and February related to the positive AO phase.The planetary wave anomalies accompany with more planetary wavenumber-2 waves in December and less planetary wavenumber-1 waves propagating into the Arctic in the lower stratosphere in January and February during the positive phase of AO.In December,the positive ozone anomalies in70-100 h Pa over the Arctic could be related to the zonal asymmetric part of polar vortex during the positive AO events.But in January and February,the weakening downwelling branch of the Brewer-Dobson circulation and strengthening of the stratospheric Arctic vortex are related to the negative ozone anomalies in the Arctic UTLS associated with the positive phase of AO.(3)The principle mode of the North Pacific SST can regulate the relationship between AO and ozone concentrations in the low stratosphere over the Arctic in February.During the negative phase of the North Pacific SST,the relationship between AO and ozone concentration in the lower stratosphere over the Arctic is significant,but relationship is not significant when the North Pacific SST are in positive phase.We found that the center of AO in the Pacific only appears during the negative phase of the North Pacific SST,which accompanies with the weakening of the subtropical jet stream and decreasing of the planetary waves propogating from troposphere to stratosphere.When the North Pacific SST are in negative phase,BDC weaken over the Arctic and the polar vortex strengths via the adiabatic cooling in the lower stratosphere correspond the negative ozone concentration anomalies during positive AO events.