Gradually Disappearing Cross-Seasonal Teleconnection Between ENSO and Tibetan Plateau Upper-Level Westerlies

Changes in the Tibetan Plateau upper-level westerlies (TPUW) and El Niño-Southern Oscillation (ENSO) are crucial in regulating local hydrological cycles and large-range climate. Here we report a gradual disappearance of the cross-seasonal ENSO-TPUW teleconnection since the early-2000s, with correlation decreasing from 0.75 to near zero. Before the early-2000s, the anomalous western North Pacific (WNP) anticyclone (WNPAC) induced by ENSO can last from winter to summer under the maintenance of Indo-western Pacific surface seawater temperature gradient (IWPSSTG), prompting the WNP subtropical high to expand and strengthen toward South Asia, attracting the Tibet Plateau subtropical high southward, thereby causing the subtropical westerly jet to move southward and forming a cross-seasonal ENSO-TPUW teleconnection. However, given the prominent tropical WNP warming since the early-2000s, the early-summer outage of IWPSSTG and WNPAC disrupts the ENSO-TPUW chain. This discontinuity poses severe challenges to the improvement of short-term climate predictions in the Tibetan Plateau and surrounding areas.