关键词: 标准化降水蒸散指数, 干旱分析, 时空变化, 中亚地区

Abstract: As a core region of the Silk Road,the importance of Central Asia to China is selfevident.With climate change,high dependence on irrigated agriculture,and increasing human disturbance,drought and water resource availability have become a key issue restricting the development and regional stability in Central Asia.This paper focused on five Central Asian countries (Kazakhstan,Kyrgyzstan,Tajikistan,Uzbekistan,and Turkmenistan) to assess the spatial and temporal distribution characteristics using the drought standardized precipitation evapotranspiration index (SPEI),which was calculated based on monthly Climatic Research Unit (CRU) data from 1961 to 2017.Specifically,the CRU grid point data (including monthly precipitation,temperature,and potential evapotranspiration) were used calculating SPEI to better reflect the climate change in Central Asia in terms of data quality and sequence.SPI and PDSI are widely used as drought indices; however,this study proposed the use of SPEI to analyze the drought condition in Central Asia as it can better reflect the effects of climate change on meteorological drought in arid and semiarid regions.The Thornthwaite formula has generally been used in the initial calculation process of SPEI; however,this only considers temperature in the calculation of potential evapotranspiration,and the calculated values may have large errors in arid and semiarid regions.Therefore,the PenmanMonteith formula was used in this paper to calculate potential evapotranspiration in the five Central Asian countries.In contrast to previous studies that mainly focused on a particular region of Central Asia,this paper calculated the SPEI value of each grid point of the five countries as a whole territory,thereby analyzing the spatial and temporal variation drought trends in Central Asia in detail.The results showed the following:(1) With the increase in temperature over the past half a century,precipitation in most parts of Central Asia showed a slow upward trend and potential evapotranspiration increased.The increase was centered in the Aral Sea basin and declined in a circular direction.(2) From 1961 to 2017,the average SPEI index in Central Asia has continuously declined; however,it greatly fluctuated.Annual changes showed a slow downward trend in SPEI value in spring and winter,and a significant downward trend in summer and autumn,indicating that the drought condition increased in summer and autumn in Central Asia.(3) Spatially,drought in most parts of Central Asia mainly increased in summers and autumns,and generally decreased in springs; in winters,drought at the border of Kazakhstan and Uzbekistan increased,and drought decreased in the eastern region.The results calculated using the SPEI drought index in this study were compared with the actual drought events and satisfactory results were obtained,indicating that our analysis and calculation of SPEI can reflect realtime drought situations in Central Asia,both temporally and spatially.Therefore,SPEI can be used as an important reference index of drought in Central Asia and can provide a valuable reference for drought risk assessment and water resources planning in Central Asia.

Key words: SPEI, drought analysis, temporal and spatial variation, Central Asia