Shallow Meridional Circulation in the Tropical Eastern Pacific*

Based on four independent datasets, this study presents observational evidence of a shallow meridional circulation cell in the eastern tropical Pacific. In this shallow meridional circulation cell the northerly cross-equatorial return flow from the ITCZ into the Southern Hemisphere is found immediately above the atmospheric boundary layer, in contrast to the classic concept of the Hadley-type deep meridional circulation whose northerly return flow resides in the upper troposphere. The strength and depth of this shallow meridional circulation undergo a distinct annual cycle. Possible causes and climatic implications of this shallow meridional circulation are discussed.