Topographic modulation of drought propagation establishes low-elevation hotspots and mid-elevation climatic refugia in Southern Africa

作者：Minyahel Tilahun, Solomon G. Tesfamichael, Takehiro Sasaki, Ayana Angassa · 发表于：Ecological Indicators · 年份：2026 · DOI：10.1016/j.ecolind.2026.114807 · 被引用次数：1 · 研究领域：Hydrology and Drought Analysis、Climate variability and models、Climate change impacts on agriculture

Drought dynamics across Southern Africa remain poorly understood, particularly regarding the topographic mechanisms that influence their spatial development and ecological consequences. Yet, the mechanisms by which local topography modulates drought propagation across elevation gradients, a key control on regional vulnerability, remain uncertain. We precisely quantify this critical mechanism. This study integrates high-resolution climate data (1950–2022) with future Standardized Precipitation Evapotranspiration Index (SPEI) projections to quantify three key aspects: 1) multi-year drought regimes, 2) topographic controls on drought propagation mechanisms, and 3) identification of hotspots of hydroclimatic vulnerability across various topographical complexities. We found the most severe long-term aridification occurs at higher elevations (2000–2500 m), where SPEI24 trends are strongest ( r = 0.6). In contrast, mid-elevation zones (1000–1500 m) displayed a persistent hydroclimatic buffer, exhibiting the slowest drought propagation rates and a decadal-scale shift toward shorter drought timescales, a pattern projected to intensify, with low-elevation zones accelerating toward more persistent drought conditions. This buffering effect, driven by orographic precipitation and reduced evaporative demand, creates distinct climatic refugia. Regionally, we identified a significant post-2000 expansion in the dominance of short-term droughts (SPEI01, SPEI03), with the fastest drought propag...