Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 7 19 2007 10.5194/acp-7-5229-2007 http://www.atmos-chem-phys.net/7/5229/2007/ http://www.atmos-chem-phys.net/7/5229/2007/acp-7-5229-2007.html http://www.atmos-chem-phys.net/7/5229/2007/acp-7-5229-2007.pdf 5229 5236 2007-10-10 Observed poleward expansion of the Hadley circulation since 1979 Y. Hu yyhu@pku.edu.cn Q. Fu Dept. of Atmospheric Sciences, Peking University, Beijing, China Dept. of Atmospheric Sciences, University of Washington, Seattle, USA Using three meteorological reanalyses and three outgoing long-wave radiation (OLR) datasets, we show that the Hadley circulation has a significant expansion of about 2 to 4.5 degrees of latitude since 1979. The three reanalyses all indicate that the poleward expansion of the Hadley circulation in each hemisphere occurs during its summer and fall seasons. Results from the OLR datasets do not have such seasonality. 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