Poleward Expansion of the Hadley Circulation in CMIP5 Simulations

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 availabl...

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Bibliographic Details
Published in:	Advances in atmospheric sciences 2013-05, Vol.30 (3), p.790-795
Main Author:	胡永云陶利军刘骥平
Format:	Article
Language:	eng
Subjects:	Air pollution Atmospheric circulation Atmospheric models Atmospheric Sciences Climate Computer simulation Earth and Environmental Science Earth Sciences Geophysics/Geodesy Global warming Greenhouse effect Greenhouse gases Hadley circulation Hadley环流 Meteorology Radiative forcing Simulation Widening 南北向历史模拟模拟产生温室气体排放耦合模式观测分析辐射强迫
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Summary:	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.
ISSN:	0256-1530 1861-9533