Spatiotemporal characteristics and long-term changes of extreme rainfall events in Taiwan

Extreme rainfall events (EREs, ≥ 80 mm day -1 ) in Taiwan were examined for their spatiotemporal characteristics from 1960 to 2022 using an event-based tracking method. Climatologically, Taiwan experiences approximately 11 EREs annually, with the highest frequency and magnitude occurring during the tropical cyclone (TC) season (July–October, 56%), followed by the early summer season (May–June, 33%). Spatially, EREs exhibit a west-to-east migration from spring to winter, corresponding to the monsoonal transition, with higher-magnitude events predominantly concentrated in the central and southern mountainous regions. EREs demonstrate significant variability on both interannual and secular timescales. Their interannual frequency is strongly modulated by ENSO-related sea surface temperature anomalies. During the summer of El Niño developing years, an anomalous cyclonic circulation in the western North Pacific coincides with an enhanced monsoon flow and higher frequency of landfalling TCs, thereby favoring more frequent EREs. In contrast, the subsequent anticyclonic circulation anomaly in autumn is accompanied by fewer ERE occurrences, with this reduction persisting into the summer of the following decaying years. The long-term evolution of EREs exhibits a significant upward trend in both frequency and intensity. This enhancement is closely associated with a deceleration in TC translation speeds at landfall and a higher proportion of westward-tracking storms making landfall in central Taiwan. Additionally, intensified TC-related ascent is linked to this trend.