Distinguishing changes in the Hadley circulation edge

Abstract

The studies on poleward expansion of the Hadley circulation have mainly concentrated on linear trends with global warming. There is no consensus on how the edge of the Hadley circulation has been affected by the dynamical linkage to causes of change. Here, this study strives to make a robust assessment of the changes in the edge latitude of the Hadley circulation by comparing two reanalysis datasets and two theoretical models, namely the Held and Hou. J Atmos Res 37: 515-533; (1980) model (HH80) and Held (2000) model (He00). A poleward shift in both hemispheres emerged after the mid-1990s in the two reanalysis datasets, except for the Northern Hemisphere from ERA-Interim. Comparing the edge latitudes of the two reanalysis datasets, HH80 (He00) is seen to be out of phase (in-phase) in the Hadley circulation edge. He00 only shows interdecadal change regarding the poleward expansion of the Hadley circulation. We found that the dominant factors affecting change in the edge latitude of the Hadley circulation were the subtropical static stability and subtropical tropopause height. The changes in the Hadley circulation in the Northern Hemisphere (Southern Hemisphere) are associated with negative ENSO and positive AO (positive SAM).