气候变化下SPEI指数在嘉陵江流域的干旱评估应用

基于嘉陵江流域1962~2010年实测月降水和月平均气温数据,利用不同时间尺度(3、6、9、12个月)的SPI和SPEI指数分析了近50a来流域干旱趋势的时空演变规律。对不同时间尺度的SPI及SPEI指数分析表明,1962~2010年嘉陵江流域整体呈干旱增加趋势,特别是流域西部和北部呈现出明显的干旱增加趋势,而流域东部的干旱增加趋势并不明显,个别站点附近还呈现出微弱的干旱减少趋势。SPI及SPEI指数的变化还表明,嘉陵江流域在大时间尺度上的干旱增加趋势更为明显,大时间尺度的干旱事件主要由降雨量决定,而气温变化对干旱趋势的影响则在小时间尺度上更为显著。此外,对于相同的时间尺度,SPEI指数相较于SPI指数检验出更为明显的干旱增加趋势,表明考虑气温影响的SPEI干旱指数更能够检测干旱事件的变化规律,因此SPEI干旱指数更适用于气候变化条件下流域干旱演变特征分析。

APPLICATION OF SPEI FOR THE CHANGES OF DROUGHT IN JIALING RIVER BASIN UNDER CLIMATE CHANGE

In order to scientifically analyze spatial and temporal changes of drought,this paper selects the Jialing river Basin as the research basin and SPI and SPEI indices are used as indices of drought.To analyze the spatial and temporal changes of drought in the Jialing River basin,both SPI and SPEI drought indices for time scales of 3,6,9 and 12 months are calculated first,based on observed monthly precipitation data and monthly average temperature data from the basin.The data covers the period from 1962 to 2010.Subsequently,the MK test is used to detect the trend of SPI and SPEI series.The SPI and SPEI indices of most stations are characterized by negative MK values for different time scales.Furthermore most of the stations pass significant test at ＞95 ％ confidence level,some of them even pass significant test at ＞99 ％ confidence level.The MK values of SPI and SPEI drought show that drought has an increasing trend in most of the basin.The spatial changes of drought show that significant drought increasing trend is detected by the MK values of both SPI and SPEI in the western and northern basin,while drought doesn't have obvious increasing trend in eastern basin,even several stations in eastern basin show a slight decreasing tendency for drought.Mathematically,the SPEI is very similar to the SPI,but it includes the role of temperature.The SPI and SPEI variations on different time scales also show that the Jialing River Basin has a more obvious increasing trend for drought on the large time scale.The SPI and SPEI indices show obvious differences in detecting spatial changes of drought trend for time scales of 3 and 6 months.The drought trend detected by SPEI is more significant which shows temperature changes has an important influence on drought for small time scales.However,the difference in the SPI and SPEI indices is smaller for time scales of 9 and 12 months which indicates that trend of drought on the large time scale is dominated by the precipitation mainly.In addition,for the same time scale,drought in the Jialing River basin shows a more severe increasing trend by applying SPEI index compared to SPI,which shows SPEI index considering the effects of temperature can test out the increasing trend of drought in a more effective way.Therefore,SPEI index is more suitable for the analysis of drought evolution characteristics of river basin under the condition of climate change.