基于CI指数和K指数的近40a贵州安顺区域干旱演变特征

The Nearly 40-Year Drought Evolution Characteristics of Anshun Municipality Assessed by CI and K Drought Indexes

利用综合气象干旱指数(CI指数)和K干旱指数,对贵州安顺地区1971-2011年41a来气象干旱的时空分布状况、演变特征及突变情况进行了比较分析.结果表明:对严重的干旱时段,两种指数均能表现出来,对历年干旱过程及灾害的评定结果基本一致;CI指数对干旱的评定更为精细,但K指数延续性更好;分季节的干旱分析中,两种指数对于夏季出现干旱概率较小的结论一致,对各季节平均干旱长度的评判基本一致.对时间演变的线性变化趋势以及M-K检验结果对比分析表明,春季和秋季干旱强度增强、夏季干旱强度减弱、年度平均干旱长度及春、秋季干旱长度增加的这几个趋势,两种方法两种指数结果一致,结论被认为是可信度较高的.M-K曲线检测表明:年度干旱长度在2008年后为增加的趋势,20世纪90年代以来春季干旱强度增强,20世纪末以来夏季干旱强度趋于减轻,秋季干旱强度增强,1970年代中期后春季干旱长度有增加的趋势,秋季干旱长度在20世纪80年代中期到90年代后增加的趋势可能发生了突变.年度干旱强度存在12～14a的长周期和年度干旱长度4～6a的短周期较为可信.

In this paper, the meteorological drought indexes CI and K were used to analyze the spatial and temporal distribution, evolution characteristics and abrupt changing of meteorological drought from 1971-2011 in Anshun Municipality of Guizhou Province. It is found that for severe drought process, the two indexes are all able to recognize;for the drought process the recognized results are consistent with real process over the years;the CI is more accurate and the K has better continuity. The seasonal drought analysis found some consistent conclusions. For example, the drought probability is smaller in summer, and the average drought length of all seasons are basically the same. The linear evolution trend analysis and the M-K test results found that the summer drought intensity was decreasing, spring and autumn drought intensity was increasing, annual drought length was also increasing. These consistent findings are considered of high credibility. From the M-K curves the above changing trends are detected. From the M-K curves the whether abrupt changing are also detected. Annual drought length has increased since 2008. Summer drought intensity has mitigated and autumn drought intensity has increased since the end of last century. The length of the spring drought has increased since the mid-1970s. Autumn drought length increased from the mid-1980s to the 1990s, followed by a mutation. According to the Mexican hat wavelet analysis, it is believed that there are a changing period of 12~13 years for the annual drought intensity and a period of 4~6 years for the annual drought length.