5种干旱指数在西藏高原地区的适用性评估

为了解不同干旱指标在西藏高原地区的适用性,本文通过利用Pa、MI、SPI、CI和FAO P-M干旱指数对西藏高原月尺度旱情等级进行评估,分析了各指标在描述旱情时的异同,并统计出各种指数的一致性及等级差异。结果表明:近20 a干旱过程中,MI、FAO P-M指数未监测出轻旱等级,而对于中旱、重旱等级,FAO P-M指数表现较好。从空间分布来看,FAO P-M指数在各个地区表现较好。从时间分布来看,FAO P-M指数在不同干旱过程期间,描述的干旱强度和中心位置与实际情况更接近;其次是Pa指数,其他指数综合表现相对较差。5种干旱指数在衡量西藏地区干旱程度上的一致性并不好;从两两指数之间反映干旱程度上出现一致性频次上看出,Pa-FAO P-M指数出现的次数最多,其次是Pa-SPI-CI指数的出现次数,MI-CI指数的出现次数最少。通过差异性分析得出,全区干旱指数不一致率平均大于20%,阿里地区和林芝地区的干旱指数整体不一致率最高,拉萨地区的干旱指数整体不一致率最低。

Applicability evaluation of five drought indices in the Tibetan Plateau

In order to understand the applicability of different drought indexes in the Tibetan Plateau (TP), Pa, MI, SPI, CI and the FAO P-M drought index were used to evaluate the monthly drought level in TP. The similarities and differences of each indicator in describing the drought were analyzed, and the consistency and grade differences of various indicators were calculated. Results show that MI and FAO P-M index did not monitor the grade of light drought in the past 20 years, but the FAO P-M index shows better performance in the grade of medium drought and heavy drought. From the perspective of spatial distribution, FAO P-M index performs well in all regions. From the perspective of time distribution, FAO P-M index was closer to the actual situation in describing drought intensity and central location during different drought processes, followed by Pa index, and other indexes has relatively poor comprehensive performance. The five drought indexes were not consistent in measuring the degree of drought in TP. As can be seen from the consistent frequency of reflecting drought degree between two indexes, PA-FAO P-M appeared the most, followed by PA-SPI-CI, and MI-CI appeared the least. Based on the difference analysis, it was concluded that the overall inconsistency rate of drought index in the whole region was more than 20% on average. The overall inconsistency rate of drought index in Ali region and Nyingchi region was the highest and that in Lhasa was the lowest.