渭河流域气象干旱向农业干旱的传播研究

为探究渭河流域不同子流域和土地利用类型的气象、农业干旱传播规律，基于研究区1980—2014年的气象数据，使用标准化降水指数和标准化土壤湿度指数分别表征气象干旱和农业干旱，采用皮尔逊相关系数和de Martonne干燥度指数，评估气象和农业干旱的传播时间和响应关系，并通过游程理论提取气象干旱与农业干旱历时、烈度，同时利用 Copula 函数度量气象干旱到农业干旱的传播阈值和农业干旱风险特征。结果表明:1)渭河干流和泾河流域气象干旱向农业干旱的传播时间为3个月，北洛河流域的干旱传播时间为2个月；2)水热条件变化对干旱传播有一定影响，这种影响沿干燥度梯度呈分段变化；3)不同子流域和土地利用类型的抗旱性不同，其中各子流域的草地及泾河、北洛河流域的林地干旱传播阈值较小，易发农业干旱；4)各分区气象干旱传播到农业干旱后历时延长、烈度增大，泾河、北洛河流域耕地的扩大作用最强。本研究可为评估不同干旱类型之间的响应关系，构建流域干旱预警系统提供新思路。

Study on the propagation of meteorological drought to agricultural drought in Weihe River Basin

In order to explore the meteorological and agricultural drought propagation laws of different sub-basins and land use types in the Weihe River Basin, based on the meteorological data of the study area from 1980 to 2014, the standardized precipitation index and standardized soil moisture index were used to characterize meteorological and agricultural drought, respectively. Based on Pearson correlation analysis and de Martonne dryness index, the propagation time and response relationship of meteorological drought to agricultural drought were evaluated. The duration and severity of meteorological and agricultural drought were extracted using run length theory, and the drought propagation threshold and risk characteristics were measured by Copula function. The results show that: 1)The propagation time of meteorological drought to agricultural drought in the main stream of the Weihe River and the Jing River Basin is three months, and the propagation time of drought in the Beiluo River Basin is two months; 2)Changes of hydrothermal conditions have a certain effect on the spread of drought, and this effect varies piecewise linearly along the aridity gradient; 3)The drought resistances among different sub-basins and land use types are different. Among them, the grassland in each sub-basin and the forest land in the Jinghe and Beiluo River basins have a small drought propagation threshold, which is prone to agricultural drought; 4)The meteorological drought in each region lasts longer and its intensity increases after spreading to agricultural drought, and the expansion of farmland in the Jing River and Beiluo River basins is the strongest. The research can provide new insights for evaluating the drought response relationship and building a basin drought early warning system.