| Deforestation can affect global and regional climate through biophysical and biochemical mechanisms.Among them,the biophysical mechanism of deforestation is more complex,including the combined effects of albedo,roughness,evapotranspiration and other processes.In order to further understand the biophysical effects of deforestation on climate,the impacts of deforestation on global and regional temperature and land surface energy balance were investigated by using satellite remote sensing data and CMIP6-LUMIP model simulations,and the biophysical mechanism of deforestation on climate was discussed.Secondly,by using the temperature decomposition method,the deforestation-induced surface temperature was attributed to the influence of different biophysical factors,and the contribution of each factor to surface temperature impact was quantified,and the possible reasons for the seasonal difference of biophysical effects of deforestation and model simulation were discussed.The main conclusions are as follows:(1)Based on the observations,there exit zonal and seasonal differences in the response of surface temperature to deforestation.In the tropics,the effect of deforestation on surface temperature is consistent,that is,deforestation increases surface temperature.In contrast,the response of surface temperature at mid-high latitudes exhibits seasonal differences.Deforestation causes surface temperature increase in summer,and its amplitude decreases with latitude.Winter deforestation leads to a decrease in surface temperature,and its amplitude increases with latitude.(2)Based on CMIP6-LUMIP multimodel ensemble results,it is found that the impact of deforestation on surface temperature has the characteristics of zonal and seasonal variations,and there are differences between models in the simulation of surface temperature after deforestation.In the tropics,most models,such as CESM2 and Can ESM5,show a consistent surface temperature response,i.e.deforestation increases surface temperature.In contrast,the ensemble mean of the models in the middle and high latitudes showed cooling,but the variation of surface temperature between the models was quite large,with the cooling amplitude in winter being about twice that in summer.The difference was greatest in North America,where the CESM2 and MPI-ESM1-2-LR had a cooling amplitude difference of 0.94 K.The disturbance of energy balance by different CMIP6 modes shows the consistency of trend and the difference of amplitude.Most models,such as UKESM1-0-LL,consistently exhibit reduced net radiation and turbulent heat flux.However,the energy balance amplitude of different models varies greatly in the middle and high latitudes.At the same time,the turbulent heat flux showed an opposite trend in winter and summer.Deforestation in winter resulted in an increase in the turbulent heat flux,while deforestation in summer resulted in a decrease in the turbulent heat flux.(3)The effects of different biophysical factors(i.e.albedo,Bowen ratio,aerodynamic resistance,incoming shortwave radiation,incoming longwave radiation and atmospheric feedback)are revealed by the IBPM temperature decomposition method.The results of multimodel ensemble mean show that atmospheric feedback is the dominant factor of global surface temperature change caused by deforestation,and the relative contribution rate is about 52～97 %in the mid-latitudes of Eurasia.The relative contribution rate of aerodynamic resistance in tropical regions(South America and central Africa)is stable at 27～31 %,while the effect of albedo in middle and high latitudes cannot be ignored.Especially in winter,the relative contribution rate in North America is about 14～38 %.In addition,in a small number of models such as IPSL-CM6A-LR and MIROC-ES2 L,contributions of aerodynamic resistance,albedo or Bowen ratio can also dominate.In summary,the differences in atmospheric feedback simulations among different CMIP6 models are the main reason for the differences in climate effects of deforestation. |
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