Changes and driving factors of compound agricultural droughts and hot events in eastern China

Compound droughts and hot events (or hot droughts) have attracted increasing attention due to their far-reaching impacts. Previous studies on these events mostly focused on the concurrence of meteorological droughts and hot extremes. The compound agricultural droughts and hot events (CADHEs), which have direct impacts on agricultural production, have received limited attention to their variability and driving factors. In this study, we defined CADHEs based on summer temperature and soil moisture from the Global Land Data Assimilation System (GLDAS) and investigated their changes and potentially driving factors for the period 1949–2014 in eastern China. Results showed increases in the frequency of CADHEs in Northeast China, North China, and South China (with increases of 125%, 160%, and 83%, respectively) except for Central China (with a decrease of 39%). Furthermore, we analyzed the contributions from individual variables (i.e., soil moisture and temperature) and their dependence on CADHEs changes in quantitative manners. For most regions, the increased temperature was the dominant driving factor of increased CADHEs. Strengthened soil moisture-temperature dependence was shown to play an important role in the increase of CADHEs in Northeast China, highlighting the contributions of dependence changes on the variability of compound events. This study can improve the understanding of changes in compound droughts and hot extremes and provide useful insights for mitigation measures of agricultural losses under global warming.