甘肃省季节性干旱综合指数的特征
The characteristics of seasonal drought’s comprehensive index in Gansu Province

利用甘肃省71个气象站1971-2013年月降水量资料，借助Z指数构建了基于干旱频率、干旱强度的干旱综合指数评价指标，从季节性干旱以及季节性连旱着手分析了不同时间尺度的干旱特征。结果表明：研究区季节性趋旱程度（MK<0）和趋旱范围（DR，%）差异显著，其中春季陇东高原为-0.154（100%），重旱为灵台（-0.238*）、宁县（-0.180）、镇原（-0.178）；夏季河西走廊为-0.081（73.7%），重旱为马鬃山（-0.271*）、安西（-0.255*）、敦煌（-0.171）；秋季陇中高原为-0.017（50.9%），重旱在会宁（-0.186）。季节性干旱综合指数重旱时段显示，春季为1995年（陇东0.481），夏季为1997年（陇南0.405），秋季为1972年（甘南0.366），冬季为1998年（陇东0.586）和2009年（甘南0.449）。两季连旱高值区在白银、会宁、古浪、玛曲、灵台、永登、华池、静宁等地（>0.030），其中秋冬连旱最为严重（0.0274）；三季连旱高值区为会宁、古浪、静宁、白银、永登等地（>0.020），其中夏秋冬连旱最为显著（0.017 5）；四季连旱高值区为会宁、古浪、西峰、灵台、泾川等地（>0.015），即除了冬春夏秋连旱外，其余季节性连旱程度均比较显著（>0.009）。
Based on the annual and monthly precipitation of 71 meteorological stations in Gansu province from 1971 to 2013, with the help of the Z index, the drought comprehensive index was constructed as the evaluation index based on the drought frequency and the drought intensity. The drought characteristics at different time scales were analyzed based on the seasonal drought and the seasonal continuous drought. The results showed significant difference in seasonal drought degree (MK<0) and drought range (%). In spring, the Longdong plateau is -0.154 (100%), and the heavy drought areas are Lingtai (-0.238*), Ningxian (-0.180), and Zhenyuan (-0.178); in summer, Gansu corridor is -0.081(73.7%), and the heavy drought areas are Mazongshan (-0.271*), Anxi (-0.255*) and Dunhuang (-0.171); in autumn, Longzhong plateau is -0.017 (50.9%), and the heavy drought area is Huining (-0.186). The seasonal drought comprehensive index of heavy drought period showed spring in 1995 (Longdong, 0.481), summer in 1997 (Longnan, 0.405), autumn in 1972 (Gannan, 0.366), winter in 1998 (Longdong, 0.586) and in 2009 (Gannan, 0.449). The high value areas of the continuous drought in two seasons were in Baiyin, Huining, Gulang, Maqu, Lingtai, Yongden, Huachi, Jingning, etc (>0.030), with the most severe drought in autumn and winter (0.0274). The high value areas of the continuous drought in three seasons were Huining, Gulang, Jingning, Baiyin and Yongdeng, etc (>0.020), among which, the drought degree of summer-autumn-winter is severest (0.017 5). The high value areas of the continuous drought in four seasons were Huining, Gulang, Xifeng, Lingtai, Jingchuan, etc (>0.015). All the seasonal continuous drought were significant (>0.009) except the winter-spring-summer-autumn drought.The research results of the seasonal drought comprehensive index can provide scientific basis for regional drought assessment and disaster prevention and reduction.