An investigation of poleward expansion of the Hadley circulation using cloud cover

Abstract

Amongst the issues associated with global climate change, the expansion of the tropics has become increasingly important. This expansion is normally demonstrated in the form of changes in the Hadley circulation. In this study the changes of the Hadley circulation were investigated using high cloud cover from the ERA-Interim reanalysis data. Trends of zonal-mean cloud cover computed over the period 1979-2017 in both hemispheres show that poleward expansion of the Hadley circulation is about 1.6 and 1.2 degree of latitude per 39 years in northern hemisphere and southern hemisphere, respectively. In addition, the expansion for all four seasons was also analysed. The analysis results show that poleward expansion occurs mostly in all seasons and the expansion of the Hadley circulation results in a poleward expansion of the subtropical dry regions.