CI综合气象干旱指数在宁夏的本地化修正及应用

利用宁夏20个气象观测站近50a逐日平均气温和降水资料，采用累积频率法对CI综合气象干旱指数进行了本地化修正。通过对比分析，修正后的指数对干旱的演变反映更为合理，对干旱事件的监测效果更好，适宜在宁夏应用。其应用分析表明：麻黄山、海原、固原、西吉4地春季、夏季和秋季各季节的干旱日数均增加，强度均增强；秋季所有地区干旱日数增多，强度增强，且大部分地区秋季干旱日数增加幅度最大；固原及以北地区的干旱增加趋势明显高于南部阴湿地区，且干旱中心向西转移，21世纪以来同心和兴仁变为干旱中心。干旱事件中大部分干旱等级的日数与干旱日数和强度具有相同的变化趋势；春季大部分地区重旱和特旱日数的增加对其干旱日数的增加贡献率最大；夏季，盐池、麻黄山、固原和泾源特旱日数的变化对干旱日数变化贡献率最大；秋季，大部分地区中旱日数的变化对干旱日数变化的贡献率最大。21世纪以来，春夏季大部分地区干旱事件频率达到年代最高或次高值，且中部干旱带频率高于南部山区，大部分地区特旱日数达到年代最大值；秋季干旱事件频率减小，所有地区各干旱等级日数明显少于1980年代和1990年代。

Modification of CI Comprehensive Meteorological Drought Index and Its Application in Ningxia

Based on daily mean temperature and precipitation data in recent 50 years at 20 meteorological stations in Ningxia, the CI in- dex were corrected by using cumulative frequency method. The corrected CI index was more reasonable than the uncorrected one in re- flecting the drought development and better in monitoring the drought events, so it was more suitable for drought monitoring in Ningxia. The applied analysis of corrected CI index indicates that the drought days increased and the intensity enhanced in Mahuangshan, Haiyuan, Guyuan and Xiji in spring, summer and fall. The drought days in all areas increased with a large increment in most areas and the intensity enhanced in fall. The increased trend of drought in Guyuan and its north was more obvious than that in southern humid re- gions in Ningxia, while the drought center transfered to the west, and Tongxin and Xingren had been the drought center since the 21 st century. The change of drought days with most different drought levels were similar to the trend of the drought days and intensity varia- tion. The increase of heavy and extreme drought days in most regions in spring had the largest contribution to drought days, while in summer, the change of the extreme drought days in Yanchi, Mahuangshan, Guyuan and Jingyuan had the largest contribution to drough days variation, and in fall, the middle drought days was the largest. From the 21st century, the frequency of drought events reached the largest or the second largest in many areas in spring and summer, but in middle arid area it was larger than that in southern moun- tain region, and the extreme drought days were also the largest. Moreover, in fall, the frequency of drought events decreased, and the drought days with all levels were less than that in the 1980s and the 1990s.