A shift toward more severe and persistent compound hot–dry extremes across the Mongolian Plateau

Abstract

Climate extremes have become increasingly frequent and severe worldwide under global warming. Among them, compound hot–dry events pose particularly acute threats to ecosystems, water resources, and agricultural systems, often producing greater impacts than heatwaves or droughts occurring alone. Using the ERA5-Land reanalysis dataset, we constructed a daily standardized compound dry and hot index (SCDHI) to investigate the spatiotemporal evolution of compound events across the Mongolian Plateau from 1995 to 2024. We revealed a pronounced intensification of compound hot–dry conditions on the Mongolian Plateau, particularly in the western and southern regions, where SCDHI trends ranged from approximately −0.2 to −0.4 decade −1 . Although low-intensity events generally became less frequent and shorter in duration, heavy and extreme events increased markedly, with their frequencies locally rising by approximately 1.8–5 events decade −1 and their durations increasing by 6–12 days decade −1 . These changes indicate a systematic shift from frequent low-intensity events toward events dominated by greater intensity and persistence. Sensitivity analysis showed that the mean response of SCDHI to SAPEI (0.57) was higher than that to STI (0.43). These findings highlight an increase in compound climate risks across the Mongolian Plateau, underscoring the urgent need for improved monitoring, early-warning systems, and adaptive land and water management strategies.