Spatial-temporal evolution and intrinsic drivers of compound drought and heatwave events in Mainland China

Given the devastating effects and potential rising trends of compound drought and heatwave (CDH) events under the specter of global warming, this study embarks on a comprehensive examination of their spatial and temporal evolution, as well as the intrinsic drivers. This study identified CDH events based on the non-stationary standardized precipitation evapotranspiration index (NSPEI) and the relative threshold method. The study also quantified the spatial and temporal patterns of frequency, intensity, and duration of CDH events across different climatic sub-regions, quantifying the contribution of drought-heatwave interdependence to these events and assessing the impact of single extreme climate events on their proliferation. The study yielded several key findings: 1) The frequency, intensity, and duration of CDH events exhibited high spatial heterogeneity and a significant increasing trend over the study period. 2) A notable positive interdependence was observed between the occurrences of droughts and heatwaves, significantly contributing to the rise in CDH events. 3) Droughts exacerbated the intensity and duration of CDH events compared to heatwaves under non-drought conditions (NDCH). 4) The spatial distribution characteristics and the change indices of heatwaves and CDH events were strikingly similar, indicating a consistent evolution. Notably, the increase in heatwaves had a more pronounced influence on the escalation of CDH events compared to droughts. 5) The West Pacific Subtropical High (WPSH) and the South Asian High (SAH) have had significant impacts on CDH events in mainland China. This research provides vital insights into the dynamics of CDH events, emphasizing their growing frequency and severity in the context of climate change. It offers a crucial perspective for policymakers and disaster management authorities in developing targeted strategies for climate adaptation and mitigation.