Reversal of the Tibetan snow-India Burma trough relationship

Variations in the winter India-Burma trough (IBT) are associated with local cyclonic anomalies over the Bay of Bengal and modulated by mid-latitude teleconnections. However, spring IBT variability remains poorly understand, despite trough-base precipitation being substantially greater than in winter. Here, we identify a reversal in the spring IBT-Tibetan Plateau snow cover (TPS) relationship around the year 2000. This shift corresponds to eastward displacement of the trough-base before 2000, followed by a retreat toward the Bay of Bengal. Snow-perturbation experiments and moist potential vorticity diagnostics show that during 1979–1999, high TPS enhances atmospheric disturbances ahead of the trough and weakens them near its base. This process hence triggers an eastward displacement of the IBT. During 2000–2020, high TPS exerts largely opposite effects. Furthermore, the Pacific Decadal Oscillation (PDO) modulates this IBT-TPS linkage reversal. In the coming decades, a projected shift to a positive PDO phase is expected to promote IBT eastward displacement, enhancing spring precipitation in East Asia while increasing drought risk over the Indochina Peninsula. Our results hence provide a basis for improving seasonal projections and assessing climate risks across monsoon Asia.