Evaluating The Effects Of Various Forcing Factors On Long-Term Trends Of Surface Temperature And Upper Atmosphere

In most studies,detection and attribution of response of surface temperature long-term trend to external forcing rely on linear assumption,which means that the linear effect of forcing dominates its influence.In the complex land-atmosphere system,however,there could be interaction between various forcing,so it is likely for nonlinear effect works beyond linear effect.Therefore,it is of great significance to detect the contribution of nonlinear interaction between forces.Previous studies have considered the nonlinear effects of two combinations of greenhouse gases and aerosols or greenhouse gases and solar radiation,but it does a little to compare and analyze the effects of multiple linear and nonlinear constraints in the same model.In this paper,we compare observation data and multiple forcing of model data(CESM-CAM5)and use linear trend analysis to evaluate nonlinear contribution of aerosol(AERO),greenhouse gas(GHG),ozone(OZ),land use change(LAND)and solar radiation(SOLAR)of five separate forcing in the two types of tests(such as AERO-Only,hist minus NoAERO)of trends of surface temperature field,the zonal mean height field and temperature field.First of all,comparing the contribution of five kinds of forcing(aerosols,greenhouse gas,land use change,ozone,solar)in the grid scale,the global average scale and the regional scale,we find that 1)greenhouse gas and aerosol forcing still play a dominant role.In both only GHG experiment and hist minus NoGHG experiment,significant warming of greenhouse gas forcing was observed in almost all regions.On the whole,the nonlinear effect weakens the tendency of only GHG forcing.2)The significant cooling effect of aerosol forcing is also shown in all the areas except the Southern Ocean and the maximum value is located in the Arctic Ocean,which is about-2.5 K/50yr.From the distribution point of view,the nonlinear effect makes the space distribution of aerosol cooling effect more uniform.3)The magnitude of the surface changes caused by ozone depletion is lower than that of greenhouse gases and aerosols.In the nonlinear field,the Atlantic India basin and the Queen Maud of Antarctica show a significant cooling trend.It is worth noting that the warming effect of ozone forcing on the surface is broad than we thought.4)The effects of land use change and solar radiation forcing are close.The nonlinear effect is more significant in southern Australia.5)The significant effect of solar radiation forcing is concentrated at 60 degrees north latitude to the North Pole.However,Only SOLAR test and hist minus NoSOLAR test have obviously opposite effect.Therefore,the non-linear effect in the field of northern Eurasia to the Barents Sea is cooling trend,and of North America to the Barents Sea is warming trend.Analyzing nonlinear effects from the global and regional scales,we find that in the global average and all the divided regions,nonlinear effects of all kinds of forcing are less than 0.05 K/decade.Therefore,the significance of nonlinear action cannot be detected.For global average trend,observation and historical test have the same significant warming trend,about 0.1 K/decade.And significant temperature trends of effect of greenhouse gases,aerosols,ozone were about-0.1 K/decade,0.2K/decade,-0.03 K/decade,respectively.In terms of the mechanism causing the nonlinear effects of temperature trend,it has both the influence of dynamic and thermodynamic activities.For the contribution of five forcing and other forcing interactions to the zonal mean height and the zonal mean temperature fields in 1950-2004,we find that,on the whole,the contribution of the nonlinear effect to change of height field and temperature field is small and insignificant.But in the solar radiation forcing,the nonlinear effect is significant in the middle latitude in zonal mean height field,which is about 10m/50yr.Therefore,for different forces,the relative importance of nonlinear effect may be different.