基于Z指数的陇东黄土高原干旱特征分析

Aridity characteristics in East Gansu's loess plateau area based on Z index analysis

选取甘肃陇东地区10个代表站1961-2008年48年逐月降水量资料,根据计算出的Z指数按旱涝等级划分标准,把Z指数划分成7个等级,确认陇东干旱强度,研究发现在过去48 a中,陇东年Z指数有显著的下降趋势,即陇东地区近48 a来总的趋势是向干旱发展的,20世纪90年代干旱强度明显增强。春秋干旱严重,总趋势为增多,夏冬干旱较轻,总趋势为减少。分片干旱特征显示48 a中的Z指数变化有显著的下降趋势,年干旱具有连续性,综合分析春、夏、秋冬四季最严重的干旱都发生在90年代,1997年春夏秋冬四旱相连,对农业的危害最重。

Selecting 10 weather stations＇ precipitation data（1961～2008） in East Gansu Province,we calculate Z index and divide it into seven levels of drought intensity. The results show that the annual Z index has a significant decreasing trend in the past 48 years,which means this area becomes increasingly dry,especially in 1990s.Drought becomes severe in spring and autumn,while it gets less in summer and winter.The regional drought characteristics show that Z index has been decreasing obviously in the past 48 years,with the annual drought presenting a continuous trend.We conclude that the most damaging drought in each season（spring,summer,autumn,and winter） all happened in 1990s.In 1997,the drought lasted all through the four seasons,which did the worst harm to agriculture.