Thermodynamic Drivers of Rapid Transition From Drought to Flood in Siberia, Russia

Abstract

Abstract Siberia is a warming hotspot under the impact of climate change, and faces growing threats from hydroclimatic extremes. The rapid transition from drought to extreme wet conditions (hereafter RTDFs) could exacerbate compound hazards, as intense rainfall on drought‐weakened surfaces may increase runoff and permafrost instability in vulnerable cold regions. While some studies have examined RTDFs, understanding of them as a continuous physical process, particularly the dynamics of the transition, requires further investigation. Using data from 408 meteorological stations across Russia (1961–2022), we identified RTDFs and examined their characteristics and underlying mechanisms. Results show that a substantial majority of RTDFs occurred in western Siberia, with a marked peak during April–May. Blocking highs play a pivotal yet contrasting role across the region. In western Siberia, intense surface heating during the drought phase reinforces local moisture recycling through a heat‐driven blocking feedback. In eastern Siberia, a pre‐existing blocking high establishes the drought, and its subsequent breakdown triggers the reorganization of atmospheric circulation and the influx of remote moisture that leads to rainfall. Beyond mean temperature, thermal stability during the drought phase, quantified by low temperature variability, is a key modulator of the transition. It allows efficient accumulation of convective available potential energy and total precipitable water, providing the essential convective instability that facilitates the abrupt termination of the drought via a rapid extreme rainfall. This study demonstrates that both the magnitude and stability of antecedent warming are critical for priming RTDFs, providing actionable insights for improving subseasonal forecasting across boreal Asia.