渭河流域多尺度干旱时空特征分析

基于渭河流域23个气象站1959—2014年的实测资料,对比分析了标准化降水指数(SPI)和标准化降水蒸散指数(SPEI)在渭河流域的适用性,得出SPEI的稳定性更佳。继而采用标准化降水蒸散指数(SPEI)研究该流域干旱发生频率与干旱强度,分析了近55年渭河流域不同时间尺度干旱的时空变化特征。结果表明:尺度越大,SPEI波动的幅度越小。渭河流域SPEI在1991年发生突变,1991年后干旱加剧,干旱的发生存在14 a和7 a左右周期变化。年尺度干旱的发生频率呈东高西低的分布,中度以上干旱频率最高的地区为西吉、武功和天水周边,频率分别为14.28%、14.28%、12.5%;季尺度上整体的秋旱相比其它季节的干旱发生频率高,中度以上春、秋、冬三季干旱发生的频率天水盆地均最高,频率分别为21.4%、19.6%和8.9%,中度以上夏季干旱发生频率最高的是平凉,其频率为16.1%;月尺度上干旱强度的分布总体上是由东向西减小,其中干旱强度最大的是南部佛坪地区,干旱强度为30%,天水和海源地区近55年发生连续干旱过程的次数最多,可达22 a,该过程中连续干旱的月数大多为3~4个月,而吴旗站存在一次长达9个月的持续干旱过程。

Analysis of spatial-temporal characteristics of drought by multiple scales in Weihe River Basin

Based on the measured data of 23 climate stations during 1959-2014 in Weihe River Basin,compared and analyzed the applicability of the standardized precipitation index (SPI) and standardized precipitation evapotranspi ration index (SPEI) in Weihe River Basin,obtained that stability of SPEI was more better.Afterwards using the SPEI,has researched the drought frequency and intensity,analyzed the spatial and temporal change characteristics of drought in recent 55 years by different time scale in Weihe River Basin.The results showed that:the more time scale,the smaller fluctuation of SPEI.The SPEI was mutated in 1991,hereafter the drought was become severe,and exsisted about 14 years and 7 years changing cycle in Weihe River Basin.The frequency of yearly scale drought was presented the distribution of high in east and low in west,the maximal drought frequency places above moderate drought were around Xiji,Wugong and Tianshui,the frequencies were 14.28％,14.28％ and 14.28％ respectively.From the seasonal scale,the autumn drought frequency was higher than other seasons,the highest frequency of above moderate drought in spring,autumn and winter seasons was in Tianshui Basin,the frequency was 21.4％,19.6％ and 8.9％ respectively.The highest frequency of above moderate drought in summer season was in Pingliang,its frequency was 16.1％.As a whole the distribution of monthly scale drought intensity was decreased from east to west,among them the biggest drought intensity was at the south Foping region,the drought intensity was 30％.In recent 55 years,the Tianshui and Haiyuan Regions were occured the maximal numbers of continuous drought process,can be reached 22 years.The month numbers as continuous drought process were mostly for 3 to 4 months,but there were one time of 9 months long continuous drought process in Wuqi station.Through the research for all kinds of drought characteristics by multiple time scales in this river basin,in order to provide guidance for drought control and resistance.