24th Pacific Science Congress (PSC-24)

The Southern Hemisphere (SH) atmospheric circulation is crucial for regulating global climate change. In the late 20th century, driven by stratospheric ozone depletion, it underwent major adjustments: the summer Southern Annular Mode (SAM) exhibited a pronounced positive trend, the westerly jet poleward and intensified, and the edge of the Hadley circulation’s descending branch expanded southward. Since the 21st century, with stratospheric ozone recovery, these trends have reversed.This study quantifies such trend changes using ERA5 and JRA-55 reanalysis data. Diagnostic analyses show ozone recovery induces springtime mid-lower stratospheric warming anomalies over the SH, restructuring the stratospheric pressure field, slowing polar vortex intensification and advancing its collapse. Through stratosphere-troposphere dynamic coupling, this regulates summer tropospheric pressure and wind fields. The circulation trend difference between recovery and depletion phases has distinct spatial patterns, weakening SAM’s intensification, slowing the jet stream’s poleward shift and intensification, and decelerating the southward expansion of the Hadley circulation’s descending edge. This provides observational evidence that ozone recovery offsets SH circulation anomalies previously driven by ozone depletion and greenhouse gases, which is of significance for climate change’s understanding and prediction.
 

Ozone Recovery ·Southern Annular Mode (SAM) · Westerly Jet · Hadley Circulation · Trend Shifts