Spatiotemporal Evolution of Regional Heavy Rainfall Events in Guangdong, South China: Intensification and Expansion Since the Early 1990s

Abstract

Regional heavy rainfall events (RHREs) have shown an increasing trend in Guangdong Province, South China, in recent decades. In order to retrieve a reliable evaluation of the RHREs in this region, this paper proposes an improved method for assessing the overall strength of each RHRE and a workflow for recognising its spatial distribution pattern. Following the identification criteria of China's national standard, 1537 RHREs were identified in Guangdong during 1961–2025 and categorised into four grades: weak, rather strong, strong and extreme strong. Annual analysis indicates a turning point in 1991, showing substantial change in the frequency and magnitude of RHREs: those of weak RHREs declined, whereas those of strong and extreme strong RHREs increased substantially, with extreme strong events rising by 49.1% in occurrence days and 26.4% in total strength from 1961–1990 to 1991–2025. Monthly distributions show that RHREs mainly occurred from April to September, with extreme strong events peaking sharply in June. Spatial depiction of heavy rainfall during RHREs confirms that three geographic regions (Fogang, Enping and Haifeng) have been consistently impacted by RHREs, with extreme strong and strong RHREs further expanded across extended regions. Spatial distribution investigation further revealed that province‐wide events were increasing, underscoring the growing scale and risk posed by RHREs under a warming climate. A warming trend (+0.17°C/decade) during the warm season accompanying a shift towards fewer light‐rain days and more heavy‐rain days provides independent thermodynamic evidence for this intensification.