The Role of Stratospheric Polar Vortex Breakdown in Southern Hemisphere Climate Trends

ABSTRACT: This paper investigates the connection between the delay in the final breakdown of the stratospheric polar vortex, the stratospheric final warming (SFW), and Southern Hemisphere climate trends. We first analyze ERA-Interim reanalysis and three climate model outputs with different climate forcings. Climate trends appear when there is a delay in the timing of SFWs. When regressed onto the SFW dates (which reflects the anomaly when the SFW is delayed for one standard deviation of its onset dates), the anomaly pattern bears a resemblance to the observed climate trends, for all the model outputs, even without any trends. This suggests that the stratospheric and tropospheric circulations are organized by the timing of SFWs, in both the interannual time scale and climate trends due to external forcings.We further explore the role of the SFW using a simplified dynamical model, in which the ozone depletion is mimicked by a springtime polar stratospheric cooling. The responses of zonal-mean atmospheric circ…

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