Spatiotemporal organization and climatic modulation of anomalous precipitation in the Huaihe River Basin (1961–2019)

Study Region The Huaihe River Basin (HRB) is a flood-prone monsoon basin in eastern China, where anomalous precipitation events frequently trigger severe flooding and pose major challenges for basin-scale flood management. Study Focus Previous index-based analyses mainly characterize long-term precipitation variability but provide limited insight into event-level Spatiotemporal organization. This study conducts an event-level analysis of anomalous precipitation in the HRB using a high-resolution daily precipitation dataset (1 km) spanning 1961–2019. A lightweight encoder–decoder model is developed to detect anomalous precipitation days, followed by qualitative and quantitative analyses to characterize spatial patterns and assess climatic modulation. New Hydrological Insights for the Region A total of 543 anomalous precipitation days are identified and classified into six distinct spatial patterns with contrasting seasonal characteristics, such as the West-type (30.8%, June–August) and the Southeast-type (8.5%, July–September). Significant inter-pattern correlations reveal spatial co-occurrence and compensation effects that may influence basin-wide flood risk distribution. A pronounced absence of anomalous events between mid-August and October during 1983–1998 indicates decadal-scale climatic modulation. Probability-based analysis further demonstrates that variations in the Western North Pacific Subtropical High (WNPSH) and the East Asian Jet (EAJ) substantially alter event likelihoods; for the Southeast-type, a westward-extending WNPSH and a southward-shifted EAJ increase occurrence probability by approximately 36% and 43%, respectively. These findings provide new event-scale hydrological insights and support climate-informed flood risk management in the HRB.