Abstract:

Based on the daily and monthly temperature，precipitation and evaporation data from 7 stations of Pingliang during 1965 －2010，the monthly drought indices of each station in recent 46 years were caculated with K index，PDSI，CI and Z index，respectively，and the application of four indices in drought variation，drought degree and range was analyzed and compared． The results show that K index，CI and Z index has close corresponding relationship with precipitation in most time，while PDSI was insensitive to precipitation variation． Each index could reflect the drought occurrence but with different intensity and extension． The intensity and extension reflected by K index was more serious than the other three indices in drought years or ordinary years，while that reflected by Z index was obviously smaller，and PDSI and CI was between K index and Z index． K index was closer to actual drought situation in serious drought years，but the adaptability of Z index was the worst． In ordinary years，PDSI，Z index and CI were more suitable，but the adaptability of CI was worst in winter． Drought is a complex cumulative process，so suitable drought indices should be selected considering moisture conditions in prophase and various factors which influence the occurrence and development of drought．

Key words: drought indices, Pingliang , adaptability, analysis

摘要：

利用平凉市７ 个气象站１９６５ ～ ２０１０ 年逐日、逐月的气温、降水、蒸发等资料，分别采用Ｋ 指数、ＰＤＳＩ、ＣＩ 指数、Ｚ 指数等４ 种干旱指标计算了各站近４６ ａ 逐月的干旱指数，分析比较了这４ 种干旱指标在干旱变化、干旱程度和范围等方面的应用情况，结果表明：Ｋ 指数、ＣＩ 指数和Ｚ 指数在多数情况下与降水对应关系密切，而ＰＤＳＩ 对降水变化的反映并不十分灵敏；各种干旱指标都能反映出区域内干旱的发生，但反映的程度和范围不同，无论在重旱年份或一般年Ｋ 指数计算的干旱程度和范围明显要大于其他３ 种指数，Ｚ 指数则明显偏轻，ＰＤＳＩ 和ＣＩ 指数介于二者之间；重旱年份Ｋ 指数对干旱程度及范围的反映更为接近实际情况，Ｚ 指数最差；一般年份，ＰＤＳＩ、Ｚ 指数和ＣＩ 指数更具有优势，但ＣＩ 指数在冬季的适用性较差。干旱是一个复杂的累积过程，在业务应用中要综合考虑前期水分情况及旱情发生发展的各类影响因素，根据实际情况选择不同的干旱指标。

关键词: 干旱指标, 平凉地区, 适应性