Abstract:Gansu Province is located in an ecologically fragile area, with complex climate conditions, high probability and wide range of drought. In order to better study the temporal and spatial variation characteristics of drought in Gansu Province, it was divided into four climate zones according to the climate type and geographical characteristics: the continental climate area of Hexi (Region Ⅰ), the monsoon climate area in the northern of Longzhong (Region Ⅱ), the monsoon climate area of Longnan and the south of Longzhong (Region Ⅲ) and the alpine climate area of Gannan (Region Ⅳ). The meteorological data of 26 national meteorological stations in Gansu Province were used to calculate the standardized precipitation evapotranspiration index on monthly, quarterly and annual scales（SPEI-1, SPEI-3 and SPEI-12）in the past 60 years (1960—2019). The spatiotemporal evolution characteristics of drought in Gansu Province in recent 60 years were discussed by means of climate tendency rate, Mann-Kendall〖JP〗 mutation test and spatial interpolation. The results showed that the SPEI values of different time scales showed a decreasing trend from the perspective of time process, and the fluctuation range of SPEI values was smaller as the time scale was increased. For seasonal factor, in spring, summer and autumn, the SPEI values showed a downward trend in fluctuations in all climate regions of Gansu Province. And the downward trend was obvious, indicating a significant drying trend. In winter, the SPEI values showed a rising trend in fluctuations in various climate regions, indicating a trend of wetting. Spatially, it showed a humid trend in Region Ⅰ of Gansu Province, but it was dire in Region Ⅱ, Ⅲ and Ⅳ of Gansu Province. And in spring, the drought in various climate regions of Gansu Province had an obvious trend of aggravation, followed by summer and autumn, while in winter, the drought was basically slowed down. The frequency of occurrence of different levels of drought in different climate regions of Gansu Province was very different and uneven, and the drought frequency from smallest to largest was extreme drought, moderate drought, heavy drought and mild drought.
