The Role of Climate and Vegetation in Regulating Drought–Heat Extremes

Abstract

Abstract Droughts cause serious environmental and societal impacts, often aggravated by simultaneously occurring heat waves. Climate and vegetation play key roles in the evolution of drought-associated temperature anomalies, but their relative importance is largely unknown. Here, we present the hottest temperature anomalies during drought in subhumid and tree-dominated regions using observation-based, global data over 2001–15. These anomalies are mainly driven by a drought-related net radiation surplus and further amplified by forests’ water-saving strategies that result in diminished evaporative cooling. By contrast, in semiarid and short-vegetation regions, drought-related temperature increases are smaller. The reduction of evaporative cooling is weak and net radiation increases only marginally due to high albedo over drought-stressed vegetation. Our findings highlight the importance of considering all interacting factors in understanding diverse mechanisms of concurrent drought–heat extremes across different climate regimes. Significance Statement Climate and vegetation have a strong influence in regulating temperature anomalies during drought. However, the physical mechanisms behind drought–heat events across different climate–vegetation regimes are not always accurately described in physically based models. Here we use global-scale, observation-based datasets to show the spatial variation of temperature anomalies during drought, with the largest anomalies in subhumid and tree-dominated regions. Further, we present observational evidence for the relative roles of climate and vegetation in shaping drought–heat extremes across space. Our study provides valuable inputs to better understand the drought–heat pathways and their spatial variations, which can inform drought adaptation and mitigation efforts.