Spatiotemporal characteristics of regional extreme precipitation in Yangtze River basin

The frequency of extreme precipitation is increasing globally and poses a significant threat to human and natural systems. At the regional scale, these changes are becoming increasingly uncertain. Therefore, it is critical to understand the spatiotemporal evolution of extreme precipitation on a regional scale. In this study, we applied the connected component labelling algorithm to define regional extreme precipitation events (REPEs). This approach considers spatial coverage and its correlation with precipitation. We further investigated the spatiotemporal changes in extreme precipitation in the Yangtze River basin using the empirical orthogonal function and examined their potential relationships with large-scale climate indices, including the El Nino-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). The results show that REPEs in the study area exhibited an increasing trend in both frequency and spatial coverage since 1970. In addition, the integrated effects of PDO and ENSO have a significant impact on REPEs at various scales in summer and at large scales in winter. We also analysed the differences in these events between the current year and the following year for PDO and ENSO combinations and found that the position of REPEs change with different PDO and ENSO combinations in both summer and winter season. The spatiotemporal characteristics of REPEs in the study area reveal the corresponding connections with the East Asian continent-ocean 500-hPa pressure field. Based on our analysis and current predictions of these ocean-atmospheric oscillations, we suggest creating more REPE scenarios for upcoming decades, which may benefit forecasting and water resource management.