Spatio-temporal patterns and driving factors of the compound drought and heatwave events across the Yellow River Basin

Study area The Yellow River Basin (YRB), China Study focus Climate change has increased the occurrence of extreme climate events worldwide, particularly compound drought and heatwave events (CDHE). The YRB is an ecologically sensitive area that plays a crucial role in supporting industrial and agricultural activities in China. Thus, it is essential to conduct a comprehensive study on CDHE in the YRB. New hydrological insights for the region This study developed a compound drought and heatwave magnitude index (CDHMI) using meteorological data to investigate the historical changes in CDHE within the YRB. Additionally, we examined the relationships between drought and heatwaves in CDHE, exploring their contributing factors and potential influences. Lastly, we combined CMIP6 models to assess their applicability to the YRB and projected future changes in CDHE. The results show that: (1) CDHE is more likely to occur in the middle and lower reaches of the YRB, with a mean frequency and duration of 1.09 events/year and 5.12 days/year, respectively. (2) Droughts and heatwaves in the YRB are generally positively correlated, and the connection between droughts and heatwaves is strengthening, especially in duration. The contribution of CDHE is primarily influenced by heatwaves, with ET being the key factor affecting CDHE, accounting for 20.6 ± 0.79% of the relative importance. (3) There are notable differences in CDHE among the 23 different global climate models, with the INM-CM4–8 being optimally modelled at YRB, followed by FGOALS-g3. CDHE significantly increased with rising SSP, with the largest magnitude in the SSP5–8.5 scenario.