Research Article
Analysis of the Evolution Characteristics of Drought-Flood Abrupt Alternation in the Pearl River Delta, China
Issue:
Volume 15, Issue 6, December 2026
Pages:
252-264
Received:
13 October 2026
Accepted:
22 October 2026
Published:
12 November 2026
Abstract: Drought-flood abrupt alternation (DFAA) is a compound extreme that is particularly consequential in densely populated deltas, yet its long-term behaviour in the Pearl River Delta (PRD) remains poorly resolved. Using the AgERA5 daily gridded precipitation dataset, this study identified DFAA events with the standardized weighted average precipitation (SWAP) index combined with run theory and analyzed their spatiotemporal evolution with the Theil-Sen slope estimator. The annual mean SWAP declined weakly and not significantly (β=−0.0040 SWAP a-1, P=0.061), and the decline was essentially a spring signal, as spring decreased significantly (β=−0.0153 SWAP a-1, P=0.001) and determined the sign of the annual trend, whereas summer, autumn, and winter showed no significant trend. Significant spring drying covered most of the delta and was steepest in the northwest, while no grid cell was significant in the other seasons. DFAA events affected 7.55% of grid cells in an average year with spring dominating the event season, accounting for 61.4% of grid cells and 51.7% in March alone, followed by summer, whereas December formed a secondary peak (8.4%) and autumn was least active (below 6%). Frequency, probability, intensity, and duration were spatially coupled, all peaking along the urbanized coast (southwestern Jiangmen, western Zhuhai, central Zhongshan, and Huizhou) and all lowest in northern Zhaoqing and on the offshore islands, while the longest episodes (60-85 days) occurred in the southwest. DFAA in the PRD is therefore a spring, pre-flood-season hazard with a coastal signature, so monitoring and water-management schedules keyed to the typhoon season would miss most events.
Abstract: Drought-flood abrupt alternation (DFAA) is a compound extreme that is particularly consequential in densely populated deltas, yet its long-term behaviour in the Pearl River Delta (PRD) remains poorly resolved. Using the AgERA5 daily gridded precipitation dataset, this study identified DFAA events with the standardized weighted average precipitation...
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,
Yingyi Tan
