Strengthening of the Linkage Between the Stratospheric Polar Vortex and Winter Compound Cold‐Wet Events in the Yangtze River Basin After the Late 1990s

Abstract

Based on the observational and reanalysis data for winters (December‐January‐February, DJF) of 1962–2022, this study addressed the relationship between the stratospheric polar vortex (SPV) and compound cold‐wet events (CCWEs) in the Yangtze River Basin (YRB). It is found that their relationship varies from an insignificant correlation to a significant negative correlation in the late 1990s. During the latter period, the winter SPV anomaly can excite an Atlantic‐Eurasian teleconnection wave train in the troposphere, which then triggers downstream responses. On one hand, the Siberian high intensifies and the polar front jet weakens, directing strong cold airs southward into the YRB. On the other hand, a baroclinic and meridional dipole‐like pattern of geopotential height anomalies appears over East Asia, with negative geopotential height anomalies extending southward from East Asia to the Indochina Peninsula and the Indian subcontinent. Together with the subtropical jet, this configuration provides favorable conditions for the formation of an inversion layer and dynamic forcing for precipitation, ultimately influencing the CCWE occurrence in the YRB. Further investigation from both observation analyses and model simulations reveals that the interdecadal shift in the dipole pattern of September Arctic sea ice concentration (SIC) from the positive phase to the negative phase (i.e., above‐average SIC in the Barents–Kara Seas and below‐average SIC in the Beaufort‐Chukchi‐East Siberian Seas) plays an important role in the interdecadal strengthening of the stratosphere‐CCWEs relationship since the late 1990s.