流域气象-水文干旱传递过程的多维度识别与定量分析研究

Drought propagation can be viewed as the migration phenomenon of moisture deficit signal moving along with the hydrological cycle process, which to some extent can reveal the inherent connections among different drought types and their mutual transformation behaviors. The objective of this program is to explore the propagation mechanism between meteorological and hydrological droughts. Specifically, the routine hydro-meteorological observations, remote sensing products and hydrological model simulations will be used to analyze the variations of hydro-meteorological variables and reconstruct drought time series. On this basis, meteorological and hydrological drought characteristics in the three dimensions (time-latitude-longitude), combined with their relationships could be recognized and established through an integrated “fast clustering-regression decision tree” drought analysis technique. Then the variation of multiple drought characteristics, transformation patterns among key elements (e.g., evapotranspiration and soil moisture) in different development phases, and the effects of climatic driving factors and catchment characteristics will be detected. To explore the nonlinear response of hydrological drought to meteorological drought, the joint and conditional probability functions will be used to describe the dependence structure between two drought types, portray the evolution of compound meteorological and hydrological drought events, and deduce the critical condition for the occurrence of hydrological drought. The expected progress could provide some scientific supports for drought prediction, drought risk assessment and adaptive management of water resources.

干旱传递描述的是水分亏缺信号随流域水循环过程运移的现象，可反映不同干旱类型之间的成因联系及转化机制。本项目以认知流域气象-水文干旱传递过程及其内在机理为目标，基于站点观测、遥感影像及分布式模拟等多源数据，集成快速聚类分析、回归决策树模型等多项技术，从时空三维(时间-经度-纬度)角度识别干旱特征属性，建立气象-水文干旱成因联系；分析干旱演进过程中多特征属性的变化规律，探明旱情不同发展阶段蒸散发、土壤水等关键要素转换作用及其气候驱动因子、流域特性因子的影响机制，解译干旱传递过程及其内在作用机理；基于联合、条件概率分布函数定量描述气象-水文干旱传递关系，刻画历史干旱事件复合重现规律，推求触发水文干旱的临界条件，进而揭示水文干旱对气象干旱的非线性响应机理。本项目可为开展流域干旱预测、旱灾风险评估和水资源适应性管理提供技术支持。

干旱传递描述的是陆面水文系统对气象干旱的响应过程，即由气象干旱引发土壤水干旱或水文干旱，可反映不同干旱类型之间的成因联系及转化机制。本项目以认知流域气象-水文干旱传递过程及其内在机理为导向，采用地面站点观测、水文模型模拟、遥感和陆面同化数据，基于三维视角分析了气象干旱和水文干旱的多维度属性特征及其时空分布，深入剖析了干旱传递的气象驱动机制和流域调节作用，构建了量化气象-水文干旱传递关系的定量评估方法，取得的研究成果主要包含3个方面：①基于时空连续的干旱识别方法，实现了从三维立体空间追踪气象干旱与水文干旱的时空演进过程，在流域尺度上系统分析了流域气象干旱和水文干旱在干旱历时、烈度、影响面积、旱情运移轨迹、多属性特征的联合概率及重现期的区别与联系；②基于典型干旱事件，深入剖析旱情初期水分衰减规律，探明了降水、蒸散发、土壤含水量等关键气象水文要素在旱情不同发展阶段的变化规律及其对干旱传递的影响机制，明晰了流域特性因子对水文干旱历时、烈度等不同属性特征的影响作用；③基于Copula函数构建了量化气象干旱和水文干旱传递关系的概率统计模型，分析了不同气象干旱情景下水文干旱的发生概率及可能规模，探明了触发水文干旱的临界水分条件，并从干旱指数选择、统计时段、数据样本等方面评估了量化方法的不确定性。研究成果可为深入认识干旱形成与发展机理，客观认识区域干旱情势，科学评估干旱风险提供理论与方法支撑。