Comparison Of The Climate Impact Of Ozone Forcing In CCSM4 And GISS-E2-R Coupled Modes

Ozone is a greenhouse gas that lasts for several weeks.Since 1970,stratospheric ozone began to decline(especially in the antarctic)significantly and tropospheric ozone significantly increased due to the increase of ozone-depleting substances(ODS)and the increase of tropospheric ozone precursors caused by human activities.In the past,studies focused on the effects of antarctic stratospheric ozone depletion on the southern hemisphere summer climate change,or the greenhouse effect of increased tropospheric ozone,but few on the effects of total ozone forcing on global climate change.This paper uses ERA-40 reanalysis data,CMIP5 CCSM4 and GISSR climate model simulation data,firstly comparing reanalysis data and two models to simulate ozone and long life cycle greenhouse gases(GHG)in 1880-1969 and 1970-1999.Then we exam and compare the differences in the contributions of ozone and GHG forcing to global temperature changes in the two models,and the differences of contribution of the two models of ozone forcing to global temperature changes,and exploring possible mechanisms.The main conclusions of this article include:1.The CCSM4 and GISSR models have significant differences in stratospheric ozone depletion and tropospheric ozone increase simulations after 1970.In 1970-1999,the ozone trend in the CCSM4 model showed a decrease in the stratosphere and increased in the troposphere.The most reduced stratosphere is in the SON in the southern hemisphere,with an intensity of less than-500 ppbv,and the reductive region can reach mid-upper troposphere and 60 degrees south latitude.The region with the most tropospheric increase is in Eurasia,with a strength of 7-10 DU.The ozone of GISSR is relatively longer in the duration of stratospheric reduction(widely over 500 ppbv reduction throughout the year),more extensive reduction(can be down to the ground and 40 degrees south latitude),and in the troposphere Increase less(almost 0 in high latitude areas).2.In the CCSM4 model,ozone had little effect on surface air temperature until 1970,with only 9.5%of the well-mixed greenhouse gas warming trend and 13%of the observed warming trend.After 1970,the temperature trend caused by ozone can account for 36%and 43%of the trend induced by well-mixed greenhouse gas and of observations.The analysis shows that ozone forcing affects net radiation is mainly by increasing downward long-wave radiation and reducing upward short-wave radiation(mainly causing sea ice reduction).The proportion of downward longwave radiation forced by ozone and mixed greenhouse gases before and after 1970 is consistent with the temperature ratio(16%VS 9.5%,30%VS 36%),and the spatial distribution of long-wave radiation and temperature,and tropospheric ozone is consistent,indicating that thermal radiative forcing in CCSM4 is the main reason for the temperature increase caused by ozone.Second,because the reduction of stratospheric ozone caused cooling in the polar regions,it resulted in the strengthening of the polar vortex and the increase of the temperature gradient.As a result,the westerlies tend to increase in both hemispheres and move polarward,resulting in warming in the northern hemisphere of Eurasia and the Southern Ocean.The polar cap index explains about 31%of the global warming trend in the winter in the northern hemisphere,suggesting that the dynamic effects of polar stratospheric ozone depletion and mid-latitude tropospheric ozone increase have contributed to warming in winter,but have contributed less in other seasons.3.Ozone forcing in the GISSR model also has a weaker warming effect in the 1880-1969 period,and the global average greenhouse warming rate is about 20%of the mixed greenhouse gas.However,after 1970,ozone forcing in the GISSR model led to a global average of significant surface temperature drop(-0.097K/30 years),which is consistent with negative long-range radiation in long-wave radiation in the GISSR model..Further analysis shows that the strong negative temperature field and height field trend lead to expansion of polar vortex to the mid-latitudes of both hemisphere,and is downward to the upper troposphere,which has a great influence on the cooling trend via stratosphere-troposphere interactions.The negative trend of the polar stratospheric circulation index can explain annual mean global cooling trend.more than 80%.4.Compared with the warming effect of ozone in CCSM4,the GISSR model overestimates the reduction and the reductive duration of stratospheric ozone,and underestimates the increase in tropospheric ozone,leading to a global average temperature cooling trend.It shows that there are many uncertainties in the simulation of the long-term ozone trend in the current climate model,and the importance of the improved chemical model in the simulation of ozone changes.