Impact of ENSO events on the interannual variability of Hadley circulationextents in boreal winter

The interannual variability of the boreal winter Hadley circulation extents during the period of 1979e2014 and its links to El Nino-SouthernOscillation （ENSO） were investigated by using reanalysis datasets. Results showed that the El Nino （La Nina） events can induce the shrinking（expansion） of Hadley circulation extent in the Southern Hemisphere. For the Northern Hemisphere, El Ni~no （La Ni~na） mainly leads to shrinking（expansion） of the Hadley circulation extent in the middle and lower troposphere and expansion （shrinking） of the Hadley circulation extent inthe upper troposphere. The ENSO associated meridional temperature gradients have close relationship with the Hadley circulation extents inboth Hemispheres. But in the Northern Hemisphere, the ENSO associated eddy momentum flux divergence plays more important role inaffecting the Hadley circulation extent than the meridional temperature gradient because of the small local Rossby number. In the SouthernHemisphere, as the ENSO induced eddy momentum flux divergence is small, the meridional temperature gradient dominates the change of theHadley circulation extent.