Further observational evidence of Hadley cell widening in the Southern Hemisphere

Abstract

Various observational and modeling studies have shown that the Hadley cell (HC) has widened during the past few decades. Here we present further observational evidence of the widening of the HC in the Southern Hemisphere by tracking the location of the subtropical ridge. A robust and significant poleward shift of the southern edge of the HC has been observed during the austral summer over the past three decades with a shift of 0.22 degrees per decade between 1980 and 2012, primarily from the South Atlantic Ocean eastward to Australia. In other seasons, significant changes in the southern edge of the HC have not been observed, with a discernable regional trend having only occurred in limited regions. The comparison of these results with those derived from reanalysis data and possible causes for the summer HC expansion in the Southern Hemisphere are briefly discussed.