基于SPEI的渭河流域干旱时空变化特征分析

Temporal-spatial variation characteristics of drought in the Weihe River Basin based on SPEI

以标准化降水蒸散指数(SPEI)作为评估指标,基于渭河流域28个气象站点1961-2017年实测降水量和气温数据,采用Mann-Kendall(M-K)趋势检验、经验正交函数以及小波变换等方法分析渭河流域干旱时空变化特征,并研究渭河流域干旱与6种大尺度气候因子之间的相关关系,进一步探讨主要气候因子对流域干旱时空分布特征的潜在影响。研究表明:渭河流域在1961-2017年间整体呈现出变旱的趋势。通过经验正交函数分解,渭河流域干旱分布场主要有3种典型模态类型,分别为全局型、西北-东南反向分布型以及东-西反向分布型;同时,大尺度气候因子南方涛动指数SOI与流域干旱分布场具有更好的相关关系,对该区域内干旱变化有较强的影响。

The Weihe River Basin is located in the semiarid and semihumid transition region of northern China and experiences frequent drought events;therefore,study of droughts in the Weihe River Basin is of great importance.Based on the precipitation and temperature data from 28 meteorological stations,the spatial and temporal variation characteristics of dryness were analyzed by using the Mann-Kendall(M-K)trend test,empirical orthogonal functions,and wavelet transform analysis.At the same time,the relationship between drought characteristics and six large-scale climatic factors was studied,and the potential impact of the main factors on the spatial and temporal characteristics of drought was further discussed.According to the research,we obtained results showing that the Weihe River Basin exhibits a drought trend between 1961 and 2017.Particularly,after 1990,the drought degree and number of drought phenomena in the basin increased greatly and the average Standardized Precipitation Evapotranspiration Index(SPEI) decreased from 0.34 during 1961-1990 to-0.37 during 1991-2017.Empirical orthogonal function analysis shows that there are three typical modes in the wet and dry distribution field of the Weihe River Basin.The global type with corresponding modal eigenvalues of 50.43% is characterized by either drought or humidity and is the main control mode of dry distributions in the Weihe River Basin;northwest-southeast reverse distribution type with corresponding modal eigenvalues of 17.35% shows that the northwest and southeast regions have different drought characteristics;east-west reverse distribution type with corresponding modal eigenvalues of 5.06% shows that the eastern and western regions have different drought characteristics.Finally,the research reveals that the Southern Oscillation Index(SOI),which represents ENSO events,exhibits the strongest correlation with drought distribution in the Weihe River Basin and from the perspective of phase analysis,abnormal SOI variations will generally bring more drought events to the Weihe River Basin.