综合气象干旱指数改进及其适用性分析

Improvement of comprehensive meteorological drought index and its applicability analysis

为准确开展区域干旱监测,该研究对综合气象干旱指数(Comprehensive Meteorological Drought Index,CI)进行了改进,使其更适用于干旱的长期监测。研究以湖北省区域为典型研究对象,利用高精度气象格网数据以及历史灾情数据,运用游程理论、相关性分析和M-K趋势检验等方法,对几种常用干旱指数的灾害识别能力、干旱演变趋势等进行了分析和比较。结果表明:改进后的综合干旱指数(The Improved Comprehensive Drought Index,CIn)能够识别湖北省的多数历史重大旱灾;CIn与实际的旱灾受灾面积和旱灾成灾面积的相关系数分别达到0.69和0.67,均优于CI指数和SPEI指数;由CIn得到的干旱历时、干旱烈度的空间分布也与文献资料相符合。在湖北省区域内取得的干旱时空演变趋势分析中发现,CIn和SPEI6的M-K测试结果中干旱趋势发生显著变化的面积比例为40.19%和53.99%(P<0.05),明显高于CI和SPEI1指数的26.40%和18.93%,表明CIn和SPEI6对长期的气候变化更为敏感,由此说明,在旱灾趋势分析中应选择合适的干旱监测指标。该研究可为区域气象干旱监测的指标选取提供指导和参考。

Drought is one of the frequent and destructive natural disasters around the world.Drought index can be used to represent the dry and wet condition of the land surface,further to serve as a sound basis for drought monitoring,assessment,and early warning in the subsequent drought research.Therefore,it is of great significance to select the appropriate indicators,in order to understand the real drought scenario,and thereby to predict the trend of drought.Generally,a comparative analysis of several indicators was also made to accurately monitor the regional drought.In this study,a comprehensive meteorological drought index(CI)was modified to make it more suitable for the accurate monitoring the drought.This field study was taken Hubei Province,China,as a typical research area.The reason is that most droughts often occur in various regions and seasons for Hubei Province,located in the central part of China,particularly belonging to a subtropical monsoon climate zone,with the uneven distribution of precipitation during the year,while the large inter-annual variability.The data captured from the China Meteorological Forcing Dataset from 1982-2015,as well as the drought data of Hubei in recent years.Various methods,including the runs theory,correlation analysis and Mann-Kendall(M-K)trend test,were used to compare the accuracy of several common drought indicators,and the evolvement of drought.In the research on the applicability of drought indexes,the results demonstrated that:(1)The improved comprehensive drought index(CIn)can identify the major droughts in this area as a useful indicator.Among 15 major droughts,13 of them can be identified when taking that indicator into consideration.(2)Compared with CI,the CIn index was calculated using the monthly data of precipitation and evaporation,indicating the index changed more steadily with a better correlation with long-term SPEI.The determinant coefficient of CIn and SPEI6 reached 0.45,while that of CI and SPEI6 was only 0.19.(3)Compared with CI index and two SPEI indexes with different time scales,two degrees of drought area that obtained by CIn have the best correlation with the drought area in the statistical data,where the correlation coefficients with the drought-affected area and drought-disaster area were 0.69 and 0.67,respectively.However,none of the other drought indices exceeded 0.65.(4)The spatial distribution of drought duration(DD)and drought severity(DS)obtained by CIn and the runs theory were also consistent with the previous studies.However,the drought duration and severity distribution based on SPEI1 and SPEI6 were not consistent with the actual situation.According to the analysis of temporal and spatial evolution trend of drought,the drought area in Hubei province was slightly increasing,where the drought trend was obvious in northern,northwest,and southwest Hubei,together with the Jianghan Plain,showing a significance level of 0.05.In the M-K test,the changed area proportions of significant drought trend were 40.19%and 53.99%in the CIn and SPEI6,much higher than 26.40%and 18.93%of CI and SPEI1,indicating that the CIn and SPEI6 were more sensitive to the long-term change of climate.Therefore,the appropriate drought monitoring indicators can be selected,and thereby to be considered in trend analysis.This finding can offer a significant reference for the selection of meteorological drought index,and further for the effective implementation of regional meteorological drought monitoring.