Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 4 2007 10.5194/acpd-7-9367-2007 http://www.atmos-chem-phys-discuss.net/7/9367/2007/ http://www.atmos-chem-phys-discuss.net/7/9367/2007/acpd-7-9367-2007.html http://www.atmos-chem-phys-discuss.net/7/9367/2007/acpd-7-9367-2007.pdf 9367 9384 2007-07-02 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 poleward expansion of about 2 to 4.5 degrees of latitude since 1979. The three reanalyses along with the MSU data all indicate that the poleward expansion of the Hadley circulation in each hemisphere occurs during its spring and fall seasons. 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