Intensifying Short‐Interval Heatwave‐To‐Rainfall Compound Extremes and Associated Exposure in the Indus Basin

ABSTRACT

Short‐interval sequences from heatwaves to heavy rainfall are an important compound hazard for irrigation‐dependent basins, exposing irrigated cropland and populations to rapid shifts from heat stress to heavy‐rainfall hazards. This study examines such sequences across the Indus Basin, defining sHW–HR events as heavy rainfall on the heatwave end day or within the following 2 days. Historical variability and trends during 1979–2025 were assessed using ERA5, with CHIRPS precipitation used for sensitivity testing, and future changes were projected using a skill‐filtered ensemble of NEX‐GDDP‐CMIP6 models under SSP2‐4.5 and SSP5‐8.5. Basin‐mean annual sHW–HR frequency increased by 0.15 events yr. ⁻¹ decade ⁻¹ during 1979–2025, with higher frequencies in the northern basin. Projections indicate further intensification. By 2071–2100, basin‐mean frequency is projected to reach 3.05 and 3.85 events yr. ⁻¹ under SSP2‐4.5 and SSP5‐8.5, respectively. Mean heatwave duration is projected to increase from 5.41 days event ⁻¹ in the historical ensemble to 11.63 and 22.61 days event ⁻¹ , accompanied by increases in trigger‐day rainfall. The corresponding irrigation‐ and population‐weighted exposures reach 62.8–93.3 × 10 ⁶  ha·events yr. ⁻¹ and 2.89–3.63 × 10 ⁹ people·events yr. ⁻¹ , respectively. These results identify where intensifying short‐interval heat‐to‐rainfall sequences increasingly occur in areas with irrigated cropland or populations across the Indus Basin.