黄河流域干旱时空演变的空间格局研究

Research on spatio-temporal evolution of drought patterns in the Yellow River Basin

干旱因子是突变性和连续性并存的复杂地理要素(即空间异质性和相似性并存),理清其空间分布格局,对于深入认识流域水资源演变规律具有重要意义。本文以黄河流域为例,采用标准化降水指数(SPI)分析流域干旱时空演变规律,基于此,运用游程理论方法从标准化降水指数中识别出干旱发生次数、历时和烈度三种属性变量,并分析季尺度干旱因子的空间分布规律;最后,利用全局和局部Moran’s I指数探究了不同特征变量的全局和局部空间自相关性,确立了流域季尺度干旱因子的空间聚集(离散)位置及其空间分布格局。结果表明:(1)黄河流域四季干旱化程度加剧,下游干旱化程度高于上游,随着季节的变化,同一响应单元存在由湿转干再转湿的变化规律;(2)不同季节,流域旱情空间分布格局差异明显,春季西安及周边区域存在区域性干旱现象(干旱次数少、历时长、烈度大);夏季黄河源区旱情严重(历时长、烈度大);秋季黄河下游三门峡、孟津和运城区域存在区域性干旱现象(干旱次数少、历时长、烈度大);冬季宁蒙河段旱情严重,而兰州断面干旱历时和干旱烈度呈现"低高异常"的空间分布格局,旱情可能会加剧。掌握旱情空间分布类型,重点布控"高高聚集"格局区域,可以有效提高旱灾决策的准确度。

Drought factor is a complex geographical feature with both mutant and continuity(i. e. spatial variability and similarity coexist), so it is very important to clarify the spatial distribution pattern of drought factors for understanding the water resources in the basin. In this paper,firstly,the Yellow River Basin is taken as an example to analyze the spatial-temporal evolution characteristics of drought in the basin by using the standardized precipitation index(SPI). Then, the run theory was used to separate the drought duration and intensity from the SPI sequence,and the spatial variability of the drought characteristic variables in the basin was diagnosed. Lastly,the spatial autocorrelation of global and local drought characteristic variables was explored using global and local Moran’s I indicators,and accurately identify the location of the seasonal drought and predicting the evolution trend of its future drought. The results show that the drought is severe in the Yellow River Basin,and the degree of drought in the lower Yellow River is higher than that in the upper reaches of the Yellow River;The spatial distribution pattern of drought conditions in the basin is significantly different in different seasons,the Xi’an and surrounding areas have similar drought conditions(less droughts,longer durations,and high intensity) in the spring,the drought in the source region of the Yellow River in summer is severe(long duration, high intensity), the type of droughts of Sanmenxia,Mengjin and Yuncheng is similar(more droughts,long duration,high intensity) in the autumn,the drought in the Ningmeng section is severe,while the drought duration and drought intensity in the Lanzhou section show a"low and high anomaly"spatial pattern,and the drought may be exacerbated in the winter. Understanding the spatial distribution of drought conditions and focusing on the control of"high and high aggregation"pattern areas can improve the correctness of drought decision-making.