Dynamics of dry-to-wet abrupt alternation events in mainland China from 1961 to 2022: A novel identification method integrating daily soil moisture and precipitation

Study region

This study focuses on mainland China, covering eight subregions.

Study focus

Dry-to-wet abrupt alternation (DWAA) events have become increasingly frequent worldwide, causing significant socioeconomic and environmental impacts. Current DWAA research overemphasizes monthly precipitation while neglecting soil moisture integration, which reduces predictive accuracy in agricultural and monsoon regions where DWAA occur within a single month. This study addresses these gaps by developing a novel identification method combining daily soil moisture with precipitation data across mainland China (1961–2022). Using data from 2474 meteorological stations and ERA5 reanalysis, we investigated DWAA characteristics and atmospheric circulation patterns across different subregions.

New hydrological insights for the region

Results reveal pronounced regional heterogeneity in DWAA distribution. Northern, Central, and Southern China experienced more frequent events, with Southern China showing the highest station average frequency (24.8 events). Northeastern, Northern China, and Eastern Arid regions displayed higher intensity values, while Southern and Southwestern regions exhibited longer durations. Temporal analysis showed distinct seasonal patterns, with summer DWAA events dominating (35.5 %), significantly exceeding winter (16.7 %) and spring (19.2 %). Atmospheric circulation analysis revealed significant tropospheric reconfigurations characterized by pronounced geopotential height changes at various pressure levels. Water vapor flux analysis identified moisture convergence zones along Southern China and the Yangtze River Basin, exhibiting significant positive anomalies of 0.006–0.012 kg/(m·s), establishing preferential corridors for moisture transport into water-deficient areas.