Quantifying the drought-flood abrupt alternation events over Wei River Basin: Dynamic evolution characteristics, driving factors and inherent mechanism

The acceleration of the global water cycle has led to a remarkable increase in the frequency of extreme disasters such as droughts and floods under changing environment. Drought-flood abrupt alternation (DFAA) events, as compound events more destructive than a single flood and drought event, pose severe threats to the sustainable development of ecosystem and society. This study applied the short-cycle drought-flood abrupt transition index (SDFAI) to identify extreme DFAA events in the Wei River Basin (WRB), the largest tributary of the Yellow River Basin of China, extracting their spatiotemporal evolution and non-stationary characteristics. By integrating meteorological factors and teleconnection indices, the drivers and inherent mechanism of DFAA events were ascertained. The results indicate that: (1) Flood-to-drought (FTD) were more severe than drought-to-flood (DTF) during the rainy season. DTF events are projected to dominate after 2016, and prominent mutations in the SDFAI, Min-FTD, and Max-DTF occurring around 1980 and 1995–2001, respectively. (2) Under the main oscillation period, the periods of extreme FTD and DTF events in the WRB were concentrated at 18–30 years and 10–30 years, respectively. (3) Both meteorological factors and teleconnection indices significantly affected the DFAA events. The teleconnection indices mainly associated with the sub-basins were Southern Oscillation Index, Arctic Oscillation, and North Atlantic Oscillation, which exhibited significant resonance periods with extreme FTD and DTF events. The combined contribution of meteorological factors to DFAA events was more susceptible, and the joint effects of teleconnection indices exerted a greater influence on the contribution rate of meteorological factors.