Compound dry and hot events in subregions of mainland China and the evolving dynamics from synoptic to sub-seasonal perspective

Study region This study focuses on ten climate-geographical subregions of China, using daily 30-day Standardized Precipitation-Evapotranspiration Index (SPEI) and daily maximum temperature data (1961–2018). Compound dry and hot events (CDHEs) are more frequent in western northeastern China, South China, eastern northwestern China, and Northeast China. Study focus While previous studies have emphasized seasonal or monthly scales, this research addresses the critical gap in understanding CDHEs at the synoptic-subseasonal scale—directly relevant to hydrological disaster prediction and early warning—by analyzing dry/hot/CDHE metrics and evolving processes of long-lasting events with emphasis on land-atmosphere interactions and atmospheric circulations. New hydrological insights for the region Hot days increased nationwide, but CDHE days show no significant trend in most subregions due to compensating dry day reductions, challenging simplistic assumptions about compound extremes under global warming. Mechanistically, distinct land–atmosphere pathways dominate across hydroclimatic zones: latent heat flux (LH) governs energy partitioning in humid/semi-humid areas while sensible heat flux (SH) prevails in arid/semi-arid areas. For large-scale circulations, southeastward migration of anomalous anticyclones dominates northern subregions pre-CDHE, whereas local anomalous anticyclones are more critical in southern subregions. These findings fill key knowledge gaps in synoptic-subseasonal CDHE dynamics, offer novel evidence for heterogeneous regional hydrological responses to global warming, and provide actionable insights for advancing short-to-medium-range hydrological disaster prediction and region-specific water resource management strategies.