基于有效干旱指数的锡林郭勒干旱时空分布特征

Characteristics of Spatial and Temporal Distribution of Drought in Xilin Gol Based on Effective Drought Index

[目的]识别锡林郭勒草原干旱事件、干旱频率和干旱强度,明确锡林郭勒气象干旱场,进而为锡林郭勒减轻干旱引发的环境和经济问题。[方法]选取1969—2018年锡林郭勒地区9个气象站点逐月观测数据,计算有效干旱指数(effective drought index,EDI),结合Mann-Kendall检验、经验正交函数(empirical orthogonal function,EOF)分解、干旱定量表征等方法,分析了60年来锡林郭勒干旱时空格局特征。[结果]锡林郭勒地区的年平均EDI指数以0.029/10 a的速度下降,干旱趋势明显增强,平均每年发生0.5次干旱事件。锡林郭勒正常发生的频率为67.17%~72.65%,发生重旱的频率为0.02%~0.99%,发生不同干旱的频率差异性较大,西南部、中部是干旱强度较高的区域。锡林郭勒前2个主要特征向量的方差贡献率分别达52.75%和14.38%,空间模态表现为一致型和东南—西北反位相型。[结论]考虑有效降水的EDI指数在揭示草原干旱时空变化趋势方面更有优势,可以用来识别气象干旱时空模态的变化情况。

[Objective]The aims of this study are to identify drought events,drought frequency and drought intensity in grassland of Xilin Gol,to understand the meteorological drought field in Xilin Gol,and then to alleviate the environmental and economic problems caused by drought in Xilin Gol.[Methods]The month-by-month observation data of nine meteorological stations in Xilin Gol region from 1969 to 2018 were selected to calculate the effective drought index(EDI).The spatial and temporal patterns of drought in Xilin Gol over the past 60 years were analyzed by combining Mann-Kendall test,empirical orthogonal function(EOF)decomposition and quantitative drought characterization methods.[Results]The annual average EDI index of Xilin Gol region decreased at the rate of 0.029/decade,and the drought trend increased significantly,with an average of 0.5 drought events per year.The frequency of normal occurrences in Xilin Gol ranged from 67.17 to 72.65%,and the frequency of severe droughts ranged from 0.02 to 0.99%,with a large variability in the frequency of different droughts,and the southwest and central regions being the regions with higher drought intensity.Contribution of variances of the previous two major characteristic vectors of Xilin Gol reached up to 52.75%and 14.38%,respectively,and the spatial mode showed a consistent type and southeast-northwest inversion phase type.[Conclusion]EDI index considering effective precipitation has more advantages in revealing the spatiotemporal variation trend of drought in grassland,and can be used to identify the spatiotemporal variation of meteorological drought.