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Abstract

With a warming climate and possible stratospheric aerosol Interventions (SAI), the Holton-Tan (HT) relationship (the teleconnection between the Quasi-Biennial Oscillation (QBO) and the Arctic stratospheric polar vortex) may have another mechanism and pathway, compared to the present-day climate (PDC). Our results from an Earth system model indicate that, under both global warming (based on the RCP8.5 emission scenario) and SAI, the HT relationship weakens, although the HT relationship is closer to PDC under SAG than under RCP8.5. While the weakening of the HT relationship under the RCP8.5 scenario is likely due to the weaker QBO wind amplitudes at the equator, another physical mechanism must lead to a weaker HT relationship under the SAI scenario since the amplitude of the QBO wind is comparable to the PDC. While the strength of the polar vortex does not change under RCP85 compared to PDC, it becomes stronger under SAG, and we attribute the weakening of the HT relationship under SAG to such a stronger vortex. In addition, our results show that in the early winter, the composite difference of the gravity wave contribution to the mean meridional circulation extends to high latitudes only for PDC and SAI but this is not the case for the RCP85, and this explains the much weaker HT relationship under RCP85 compared to both SAI and PDC scenarios. In general, the contribution from the unresolved gravity waves in deriving the residual circulation response plays an important role in determining the response of the polar vortex to QBO phases.