Poleward Expansion of the Hadley Circulation in CMIP5 Simulations  

作　　者：胡永云 陶利军 刘骥平 

机构地区：[1]Laboratory for Climate and Ocean-Atmosphere Sciences, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University [2]State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences

出　　处：《Advances in Atmospheric Sciences》2013年第3期790-795,共6页大气科学进展（英文版）

基　　金：supported by the National Natural Science Foundation of China(NSFC Grant No.41025018);the National Basic Research Program of China(973 Program,Grant No.2010CB428606);supported by NSFC(Grant No.41176169)

摘　　要：Observational analyses have demonstrated that the Hadley circulation has expanded poleward in recent decades. Important issues are what caused the widening of the Hadley circulation and whether the observed widening is related to anthropogenic forcing. In the present study, we use currently available simulations of the Coupled Model Intercomparison Project Phase-5 （CMIP5） to analyze changes in the width of the Hadley circulation. It is found that CMIP5 historical simulations with greenhouse gas （GHG） forcing generate a total widening of ,-0.15°±0.06°in latitude （10 yr）-1 for the period 1979-2005, and the widening in CMIP5 historical simulations with all forcings is -0.17°± 0.06° per decade. Similar to that in CMIP3, the simulated poleward expansion in CMIP5 is much weaker than the observational reanalyses. In CMIP5 projection simulations for the 21st century, magnitudes of widening of the Hadley circulation increase with radiative forcing. For the extreme projected radiative forcing of RCP8.5, the total annual-mean widening of the Hadley circulation is -0.27°±0.04° （10 yr）-1 in the 21st century. Although CMIP5 underestimates observed poleward expansion of the Hadley circulation, the results of this study suggest that the observed trends in the width of the Hadley circulation are caused by anthropogenic forcing and that increasing GHGs play an important role in the observed poleward expansion of the Hadley circulation, in addition to other foreings emphasized in previous studies.Observational analyses have demonstrated that the Hadley circulation has expanded poleward in recent decades. Important issues are what caused the widening of the Hadley circulation and whether the observed widening is related to anthropogenic forcing. In the present study, we use currently available simulations of the Coupled Model Intercomparison Project Phase-5 （CMIP5） to analyze changes in the width of the Hadley circulation. It is found that CMIP5 historical simulations with greenhouse gas （GHG） forcing generate a total widening of ,-0.15°±0.06°in latitude （10 yr）-1 for the period 1979-2005, and the widening in CMIP5 historical simulations with all forcings is -0.17°± 0.06° per decade. Similar to that in CMIP3, the simulated poleward expansion in CMIP5 is much weaker than the observational reanalyses. In CMIP5 projection simulations for the 21st century, magnitudes of widening of the Hadley circulation increase with radiative forcing. For the extreme projected radiative forcing of RCP8.5, the total annual-mean widening of the Hadley circulation is -0.27°±0.04° （10 yr）-1 in the 21st century. Although CMIP5 underestimates observed poleward expansion of the Hadley circulation, the results of this study suggest that the observed trends in the width of the Hadley circulation are caused by anthropogenic forcing and that increasing GHGs play an important role in the observed poleward expansion of the Hadley circulation, in addition to other foreings emphasized in previous studies.

关 键 词：global warming Hadley circulation increasing greenhouse gases CMIP5 

分 类 号：P434[天文地球—大气科学及气象学]