Abstract:

Based on the daily precipitation and temperature data at 8 weather stations in Xiangxi autonomous prefecture of Hu’nan during 1960-2013, the composite index (CI) of meteorological drought was calculated, firstly. And the drought days and intensity index of annual and seasonal drought were statistically done according to drought process method. The spatial and temporal distribution characteristics of drought intensity and drought days in Xiangxi autonomous prefecture were analyzed by using the trend analysis, Mann-Kendall test and wavelet analysis. The results are as follows: (1) Due to the differences in geographical location and terrain of Xiangxi of autonomous prefecture Hu’nan, there were some differences in drought intensity, drought days and frequency in different seasons, and the drought in summer and autumn had great impacts on the annual drought. (2) The drought in Xiangxi autonomous prefecture during 1960-2013 existed several significant activity period, but there had been some fluidity in different seasons. (3) The drought strengthened in Xiangxi autonomous prefecture in spring and summer during 1960-2013, while that slightly weakened in winter. (4) Although the anuual drought in Xiangxi autonomous prefecture increased in the past 54 years, the mutation wasn’t happened. And the drought in spring and summer was no mutation too, however that in autumn mutated in 1989 for drought intensity and in 1970 for drought days, and mutated with weakening trend in 1989 in winter.

Key words: Xiangxi autonomous prefecture, composite index (CI), trend analysis, wavelet analysis, Mann-Kendall test

摘要：

利用湖南省湘西自治州8个气象台站1960～2013年逐日气温和降水资料，计算逐日CI干旱指数，按照干旱过程方法统计年、季的干旱天数及强度指数，运用趋势分析、M-K检验、小波分析等方法，统计分析湘西自治州的干旱时空变化特征。结果表明：由于地理位置及地形的差异，湘西自治州年干旱强度、干旱天数、出现频率因季节不同而存在一定的差异，其中夏秋季干旱对年干旱的影响最大；干旱存在多个显著的活动周期，但不同季节也有所差异；年干旱变化有加强趋势，而春、夏季干旱也表现出加强趋势，仅冬季干旱略有减弱。M-K突变检验显示，年干旱有加强趋势，但未出现显著性突变；春、夏季干旱变化不存在突变；秋季，干旱强度经历了由明显偏弱到波动较大再转为偏强的突变过程，突变年份为1989年，而干旱天数经历了偏少到偏多的突变过程，突变年份为1970年；冬季干旱强度存在明显减弱的突变现象，突变年份为1989年。

关键词: 湘西自治州, CI指数, 趋势分析, 小波分析, M-K检验