Understanding the meteorological-soil-hydrological drought propagation characteristics can provide technical supports for the formulation of drought mitigation measures. Taking Inner Mongolia as the research area, we utilized the ERA5-Land soil moisture and surface runoff dataset from the European Centre for Medium-Range Weather Forecasts from 1980 to 2022, coupled with observation data from 115 meteorological stations, to calculate standardized precipitation evapotranspiration index (SPEI), standardized soil moisture index (SSI), and standar-dized runoff index (SRI) at different temporal scales. Then, we used run theory, Theil-Sen median trend analysis, the Mann-Kendall test, and Pearson correlation analysis to investigate the lag effects across different types of droughts and the spatiotemporal distribution of propagation time. The results showed that over 85% of the region showed an intensifying trend for meteorological, soil, and hydrological droughts, with areas showing significant wetting covering less than 1% of the study area. Meteorological drought events were characterized by high frequency, low severity, and short duration, whereas soil drought events exhibited low frequency, high severity, and long duration. Hydrological droughts were dominated by high frequency, low severity, and short-duration events. The response between soil and hydrological drought was stronger than that between meteorological and hydrological drought, implicating that soil moisture deficit induced by soil drought was the primary trigger for hydrological drought. The propagation time for various levels of droughts was predominantly concentrated between two to six months, with higher-grade drought events showing more efficient transition and propagation. The continuity of meteo-rological, soil, and hydrological drought events in central and western Inner Mongolia and soil-hydrological drought events in eastern Inner Mongolia were relatively weak. This research would be of great significance in revealing the mechanisms of regional drought formation and constructing drought propagation models.
开展气象-土壤-水文干旱传播特征研究可为制定抗旱减灾措施提供技术支持。本研究以内蒙古为研究区,基于1980—2022年欧洲中期天气预报中心的ERA5-Land土壤湿度和地表径流数据集,以及内蒙古115个气象站点的观测数据,分别计算不同时间尺度的标准化降水蒸散指数、标准化土壤湿度指数和标准化径流指数;运用游程理论、皮尔逊相关性分析、Theil-Sen median趋势分析和Mann-Kendall检验等方法探究内蒙古各类型干旱之间的时滞效应及传播时间的时空分布特征。结果表明: 1980—2022年,内蒙古至少85%以上的区域气象、土壤、水文干旱均表现为加重趋势,显著变湿区域不到研究区面积的1%;气象干旱事件表现为高频率、低烈度、短历时的特性,土壤干旱事件表现为低频率、高烈度、长历时的特征,水文干旱以较高频率、低烈度、短历时的干旱事件为主;土壤干旱与水文干旱间的响应关系强于气象干旱与水文干旱,土壤干旱导致的土壤水分亏缺是触发水文干旱的主要因素;各类各级干旱传播时间均集中于2～6个月,较高等级的干旱事件间的转换和传播效率更高,内蒙古中西部的气象与水文、土壤干旱事件以及内蒙古东部的土壤-水文干旱事件连续性相对较弱。该研究对于揭示区域干旱形成机理及构建干旱传播模型均具有重要意义。.
Keywords: drought propagation; propagation time; run theory; time-lag effect.