Projected Changes in Spatiotemporal Propagation of Droughts Over the Loess Plateau: Roles of Climate and Vegetation Change

Abstract

The Loess Plateau (LP) is experiencing amplified warming and greening trends, which complicate the spatiotemporal propagation of droughts in the atmosphere-hydrological-soil system. Investigating how climate and vegetation changes modulate drought propagation processes is crucial for understanding the hydrological responses to environmental change. Using an ensemble of 10 climate models to drive a process-based hydrological model to perform long-term simulations, this study aims to investigate future changes in drought propagation characteristics across the LP under different climate and vegetation change scenarios. Here, a three-dimensional drought identification method was adopted, and results show that meteorological drought duration and severity were projected to decrease. Future soil and hydrological drought projections would exhibit less robust but divergent changes, with hydrological drought duration decreasing while soil drought duration and intensity increasing moderately. Despite large uncertainties in the projections, our analysis demonstrated a significant acceleration in the propagation from meteorological to soil and hydrological droughts under future scenarios. Climate change was expected to dominate the accelerated propagation, indicating an important role of thermal-enhanced soil moisture depletion. The impact of vegetation change was much smaller, which was projected to slightly decrease the propagation time under a moderate emission scenario but increase it under a high emission scenario. These findings reveal distinct responses of soil and hydrological droughts to global change in arid/semi-arid regions and underscore the urgent need for climate mitigation to curb escalating drought risks.