Research on the Identification and Spatiotemporal Evolution Characteristics of Meteorological Drought Events in Shaanxi Province

基于1961~2024年陕西省100个气象站逐日观测数据，采用Penman-Monteith公式估算潜在蒸散量，构建标准化降水蒸散指数(SPEI)，从时间演变、空间分布及干旱事件识别与迁移特征等方面，系统分析陕西省气象干旱的时空变化特征及其主控因子。结果表明，陕西省年平均SPEI自1980年代起持续下降，干旱程度显著加剧，2015~2019年达到极端重旱水平。季节上表现为“冬春偏干、夏季湿润、秋季再干”的年内变化。空间上，冬季干旱最严重，夏季则受季风影响显著转湿。相关性分析显示，不同气象因子对SPEI的影响存在显著区域差异，气温、地温在陕北与SPEI呈正相关，而相对湿度则在全省表现为正相关。通过三维空间聚类识别出22次典型干旱事件，发现其呈现“持续时间长 + 覆盖范围广”的演变特征，2000年后干旱事件持续性显著增强，干旱空间迁移以南北向为主，有明显的方向性扩展趋势。研究结果揭示了区域干旱演变特征，可为干旱监测与风险防控提供科学依据。Based on daily observational data from 100 meteorological stations in Shaanxi Province from 1961 to 2024, potential evapotranspiration was estimated using the Penman-Monteith equation, and the Standardized Precipitation Evapotranspiration Index (SPEI) was constructed. The spatiotemporal variation characteristics and controlling factors of meteorological drought in Shaanxi Province were systematically analyzed from the perspectives of temporal evolution, spatial distribution, and drought event identification and migration features. The results show that the annual mean SPEI in Shaanxi Province has continuously decreased since the 1980s, with drought severity significantly intensifying and reaching extreme-to-severe levels during 2015~2019. Seasonally, intra-annual variation manifests as “drier in winter and spring, wetter in summer, and drier again in autumn”. Spatially, winter drought is most severe, whereas summer conditions become significantly wetter under monsoon influence. Correlation analysis indicates marked regional differences in the impact of meteorological factors on SPEI: air temperature and 5 cm soil temperature in northern Shaanxi are positively correlated with SPEI, while relative humidity exhibits a positive correlation across the entire province. Through three-dimensional spatial clustering, 22 typical drought events were identified, revealing an evolution characterized by “long duration and wide coverage”. After 2000, drought event persistence significantly increased, and spatial migration of droughts primarily followed a north-south trajectory, exhibiting a clear directional expansion trend. These findings elucidate the regional evolution characteristics of drought and provide a scientific basis for drought monitoring and risk prevention and control.