On the Differences and Climate Impacts of Early and Late Stratospheric Polar Vortex Breakup

The stratospheric polar vortex breakup (SPVB) is animportant phenomenon closely related to the seasonal transition ofstratospheric circulation. Inthis paper, 62-year NCEP/NCAR reanalysis data were employed to investigatethe distinction between early and late SPVB. The results showed that theanomalous circulation signals extending from the stratosphere to thetroposphere were reversed before and after early SPVB, while thestratospheric signals were consistent before and after the onset of lateSPVB. Arctic Oscillation (AO) evolution during the life cycle of SPVB alsodemonstrated that the negative AO signal can propagate downward after earlySPVB. Such downward AO signals could be identified in both geopotentialheight and temperature anomalies. After the AO signal reached the lowertroposphere, it influenced the Aleutian Low and Siberian High in thetroposphere, leading to a weak winter monsoon and large-scale warming at midlatitudes in Asia. Compared to early SPVB, downward propagation was notevident in late SPVB. The high-latitude tropospheric circulation in theNorthern Hemisphere was affected by early SPVB, causing it to enter a summercirculation pattern earlier than in late SPVB years.