Observed poleward expansion of the Hadley circulation since 1979 Y. Hu1 and Q. Fu2 1Dept. of Atmospheric Sciences, Peking University, Beijing, China 2Dept. of Atmospheric Sciences, University of Washington, Seattle, USA
Abstract. 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. The expansion of
the Hadley circulation implies a poleward expansion of the band of
subtropical subsidence, leading to enhanced mid-latitude tropospheric
warming and poleward shifts of the subtropical dry zone. This would
contribute to an increased frequency of midlatitude droughts in both
Citation: Hu, Y. and Fu, Q.: Observed poleward expansion of the Hadley circulation since 1979, Atmos. Chem. Phys., 7, 5229-5236, doi:10.5194/acp-7-5229-2007, 2007.