On the Seasonality of the Hadley Cell

Abstract

The annual march of the climatological mean meridional circulations (MMCs) in the NCEP?NCAR reanalyses is dominated by two components of roughly comparable mean-squared amplitude: 1) a seasonally invariant pair of ?Hadley cells? with rising motion centered near and just to the north of the equator and subsidence in the subtropics, and 2) a seasonally reversing, sinusoidally varying ?solsticial? cell with ascent in the outer Tropics of the summer hemisphere and subsidence in the outer Tropics of the winter hemisphere. The meridional structure and seasonal evolution of the solsticial cell are suggestive of a close association with the monsoons. These results are consistent with previous analyses of the mean meridional circulation based on radiosonde data.