A severe drought event over Eastern China during the winter of 2024/25 and the synergistic effects of the Indo-Pacific SST and Tibetan Plateau

Abstract

Using observational and reanalysis data, this study investigates the severe winter drought event in Eastern China during 2024/25, which is the most extreme in at least four decades. The event featured a record-low Eastern China winter precipitation (ECWP) of 36.24 mm, with over 80 % precipitation deficits in multiple Eastern China regions and numerous stations recording their lowest/second/third-lowest winter precipitation, 39 consecutive days of nearly no measurable precipitation. Statistical analysis and dynamic diagnostics reveal that the ECWP is synergistically influenced by the Indo-Pacific sea surface temperature (SST) and Tibetan Plateau (TP) thermal conditions. The Equatorial-North Pacific (ENP) and Indian Ocean SSTs modulate the ECWP by affecting circulation to regulate moisture transport from the South China Sea and the Bay of Bengal to Eastern China, respectively. The TP thermal effect exerts its effects through cold (warm) temperatures inducing an anomalous cyclone (anticyclone) near the TP, which enhance (suppress) moisture transport to Eastern China and thereby increase (reduce) the ECWP. During the winter of 2024/25, both the Indo-Pacific SST and TP thermal conditions were unfavorable for the ECWP. A multi-factor empirical model for the ECWP, constructed based on the Indo-Pacific SST and TP thermal conditions, exhibits strong simulation capabilities for the ECWP.