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Shallow Meridional Circulation in the Tropical Eastern Pacific

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  • 1 Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida
  • | 2 Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, Washington
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Abstract

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.

Corresponding author address: Dr. Chidong Zhang, RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149-1098. Email: czhang@rsmas.miami.edu

Abstract

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.

Corresponding author address: Dr. Chidong Zhang, RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149-1098. Email: czhang@rsmas.miami.edu

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