干旱指数在中国东北、西南和长江中下游地区适用性分析

Analysis of the Applicability of Drought Indexes in the Northeast,Southwest and Middle-lower Reaches of Yangtze River of China

基于气温、降水、土壤墒情以及历史干旱灾情等资料,从干旱时空分布特征、典型干旱过程诊断、不合理跃变分析以及与土壤墒情、干旱灾情的相关性等方面,分析标准化降水指数(SPI)、标准化降水蒸散指数(SPEI)、相对湿润度指数(MI)、气象干旱综合指数(MCI)在我国东北、西南和长江中下游地区的适用性。结果发现,四种指数对干旱的年际变化诊断基本一致,而对干旱空间分布的诊断,MCI与MI指数与实况更加吻合。针对典型干旱过程的逐日诊断,MCI指数对干旱过程的刻画效果最好,不合理跃变次数较SPI、SPEI和MI指数分别下降82.6%、73.8%和97.8%;各指数在长江中下游地区不合理跃变次数最少,其次为西南地区,东北地区相对较多。与土壤墒情的相关性方面,MCI指数最好,均通过99%的信度检验,较SPI、SPEI和MI指数分别提高9.2%、54.7%和68.8%;西南地区代表站与土壤墒情的相关性最好,其次为长江中下游地区,东北地区相对较差。与干旱受灾面积的相关性方面,MCI指数也是最好的,较SPI、SPEI和MI指数分别提高16.9%、37.1%和27.6%;各指数在东北地区与灾情的相关性优于长江中下游地区,西南地区总体较差。综合来看,MCI指数适用性最好,这与干旱指数的构造方法及其考虑的干旱影响因子、时间尺度、不同时段降水权重等因素密切相关。

Based on the data of temperature,precipitation,soil moisture and historical drought disasters,this paper analyses the applicability of SPI,SPEI,MI and MCI in the northeast,southwest and middle-lower reaches of Yangtze River of China from the aspects of spatial and temporal distribution characteristics of drought,diagnosis of typical drought processes,unreasonable jump times analysis and correlation with soil moisture and drought disasters,etc.The results show that the four indexes are basically the same in diagnosing the interannual variation of drought days,while as to diagnosis of the spatial distribution of drought days,the MCI and MI indexes are more consistent with the actual situation.As far as the daily diagnosis of typical drought processes is concerned,MCI has the best effect on the description of drought process,and the unreasonable jump times are 82.6%,73.8%and 97.8%lower than that of SPI,SPEI and MI respectively.There are the least unreasonable jump times of each index in the middle-lower reaches of Yangtze River,followed by that in the southwest China and the northeast China.Compared to SPI,SPEI and MI,MCI is the best in the correlation with soil moisture,which has passed the confident level of 99%,and increases by 9.2%,54.7%and 68.8%respectively.The correlation between the soil moisture and representative stations in southwest China is the best,followed by that in the middle-lower reaches of Yangtze River,and that in the northeast China is relatively poor.In terms of correlation with drought-affected area,MCI is also the best,which is 16.9%,37.1%and 27.6%higher than SPI,SPEI and MI respectively.The correlation between the indexes and the drought-affected area in northeast China is better than that in the middle-lower reaches of Yangtze River,while that in southwest China is worse.On the whole,the applicability of MCI is the best,which is closely related to the construction methods of drought indexes,drought influence factors,time scales,weight of precipitation in different periods and so on.