The impact of intraseasonal oscillations on the 2024 abrupt drought-to-flood transition over central China

In 2024, an exceptionally severe abrupt drought-to-flood transition (ADFT) event occurred over Henan Province in central China, causing substantial economic losses due to its abruptness and limited early warning. Although intraseasonal oscillations (ISOs) can provide precursors for forecasting extremes, previous studies have primarily focused on floods or droughts in isolation, leaving the synergistic impacts of multiple ISO modes on drought-to-flood transitions poorly understood. Here we show that the 2024 ADFT event was jointly modulated by two ISO modes with opposite propagation directions. During the drought stage, Rossby wave train maintained a Ural blocking pattern and displaced the westerly jet southward. This circulation configuration suppressed precipitation while enhancing temperature and sensible heat, leading to persistent drought conditions. During the transition-to-flood stage, both the Rossby wave train and the Western Pacific Subtropical High (WPSH) oscillation acted in concert. The southeastward-propagating Rossby wave train disrupted the blocking, while the WPSH oscillation migrated northwestward. Their combined effects shifted the rain belt northward, strengthened southerly moisture transport, increased latent heating, and ultimately triggered the extreme flood. The synergy between these two ISO modes amplified the transition magnitude by 50%, suggesting that the ADFT event would have been largely suppressed in the absence of their concurrent influence. These results underscore critical role of ISO phase evolution and propagation in ADFT events, and suggest that they may serve as useful precursors for forecasting abrupt transitions.