The Recovery Trend Of Northern Hemisphere Ozone And Its Impact Factors Since 2000

Stratospheric ozone plays a key role in the global radiation budget and energy balance process.Total Column Ozone(TCO)has shown a decreasing trend in the past decades,and began to recover in 2000.Based on several satellite data and meteorological reanalysis data,combined with the Whole Atmosphere Community Climate Model(WACCM3),the effects of temperature,ozone-depleting substances(ODS),Brewer-Dobson circulation and land-sea thermal differences on the recovery trend of stratospheric ozone at different altitudes from 2000 to 2016 and the effects of human emissions of NO_x on the ozone and temperature in the upper troposphere and lower stratosphere(UTLS)were diagnosed and analyzed.1.The recovery trend of TCO during 2000-2016 was analyzed.The effects of stratospheric temperature,ODS,Brewer-Dobson circulation and land-sea thermal differences on TCO were analyzed by correlation analysis.The results show that TCO in the lower latitudes of the Northern Hemispheres and Southern Hemispheres has an obvious increasing trend from 2000 to 2016,which is mainly contributed by the increase of stratospheric ozone at 1-10 hPa.There is a significant trend of ozone increase in the middle and low latitudes of the upper stratosphere,while there is a weak trend of ozone increase in the polar.The increase of upper stratospheric ozone is mainly affected by the decrease of upper stratospheric temperature and decline of ODS concentration.The lower upper stratospheric temperature and ODS resulted in the weakening of ozone depletion reaction which leads to recovery of ozone.In the lower and middle stratosphere,ozone decreases in the tropics and the mid-latitudes of the Southern Hemisphere,which are mainly affected by the dynamic effect:the ascending branch of the Brewer-Doboson circulation in the tropics(0-10°N,10-20hPa)transfers ozone to upper stratosphere,and the ozone concentration in the middle stratosphere decreases.The decrease of ozone in the mid-lower stratosphere of the Southern Hemisphere(20-60°S,50-70 hPa)may be due to the enhancement of the polar branch of the Brewer-Dobson circulation in the Southern Hemisphere,which transports ozone to the polar region and ozone concentration in the region decrease.The trough over the Northwest Pacific and East Asia has a positive trend of potential height,which weakens the trough area.The convergence effect of ozone is weakened,resulting in a reduction in ozone.The ridge area over the Euro-Atlantic Ocean has a negative trend of potential height,which weakens the ridge area.The divergence effect of ozone is weakened,resulting in an increase in ozone.2.Using the ozone Monitoring Instrument(OMI)satellite data and Whole Atmosphere Community Climate Model(WACCM3),the impact of increasing surface emissions of nitrogen oxide(NO_x)in East Asia on ozone and temperature in the upper troposphere and lower stratosphere(UTLS)is investigated.Surface NO_x emissions in East Asia can be transported to the tropics andEast Asia UTLS region during summer and autumn.In summer,the south Asia anticyclone can transport the NO_x in the East Asia UTLS region to the low latitudes.In the UTLS regions,photochemical reactions in the lowlatitudes are enhanced with the increase of surface NO_xemissions in East Asia,resulting in an increasing in the low-latitude ozone concentration which leads to warming in the region in winter;while an intensified cyclic depleting ozone in the middle latitudes resulting in the mid-latitude ozone concentration decreasing which leads to cooling in the region in winter.The meridional gradient of temperature between low latitude and mid-high latitudes in the UTLS regionweakens leading to a weakening subtropical jet.Meanwhile,the enhanced meridional gradient of temperature between polar region and middle and high latitudes leads to an intensive mid-high latitudes westerly jet.The planetary waves entering the stratosphere are inhibited,which is mainly associated with the obviously weakening wave 1 and wave 2 at high latitude.