Spatio-temporal distribution characteristics of different types of compound extreme climate events in the Yangtze River Basin

In the context of global climate warming, the frequencies of extreme climate events and compound extreme events in the Yangtze River Basin have increased. To comprehensively analyze the spatiotemporal distribution characteristics of different types of compound extreme events in the Yangtze River Basin, this study utilized daily temperature and precipitation data from 1961 to 2022. Different threshold-based heatwave indicators, a drought indicator based on 90-day water accumulation, and an improved flood indicator were established. On this basis, the spatiotemporal distribution characteristics of compound heatwave-drought events, compound heatwave-waterlogging events, and regional compound extreme climate events in the upper, middle and lower reaches, and the entire Yangtze River Basin were identified. The results show that the heatwave events identified by relative thresholds occur more frequently in the upper reaches of the Yangtze River Basin, while heatwaves, droughts and floods identified by absolute thresholds occur more frequently in the middle and lower reaches of the Yangtze River Basin. The occurrence area of compound high-temperature drought and high-temperature waterlogging events has expanded at a maximum rate of 2.34 and 2.68% per decade, while the total annual duration has decreased at a maximum rate of -0.06 and − 0.42 days per decade. Furthermore, the occurrence areas of upstream drought and downstream waterlogging events have decreased at rates of -1.5% and − 0.2% per decade respectively, and the number of co-occurrence days has decreased at a rate of -0.2 days per decade. Meanwhile, the occurrence areas of upstream drought and downstream high-temperature events have both increased at a rate of 0.1% per decade, and the number of co-occurrence days has also increased at a rate of 0.2 days per decade. These results provide a scientific basis for water and power resource management and for addressing extreme climate events in the Yangtze River Basin.