Temporal and Spatial Changes of Drought Characteristics in Temperate Steppes in China from 1960 to 2020

To study the change in drought characteristics, it is helpful to explore the dynamics of drought, analyze the rules of drought, and prevent drought. The annual and seasonal standardized precipitation evapotranspiration index (SPEI) was calculated based on the meteorological data of the temperate steppe region of China from 1960 to 2020, and the spatio-temporal variation of drought characteristics was analyzed by combining the run-course theory to identify drought characteristics. The results show that: (1) During 1960–2020, the SPEI of the temperate steppe region fluctuated in the range of −1.5 to 1.5 and decreased significantly at a rate of −0.02·a−1 (p < 0.01). In general, there is an increasing trend of drought in the temperate steppe region. (2) There is little difference in the duration of drought in the four seasons, and the very low duration of drought is about 2 months. The cumulative drought intensity was higher in the semi-arid and semi-humid zones of the temperate zone. (3) The very low value of drought frequency occurred in summer, and the very high value of drought frequency occurred in winter. From SPEI-3 to SPEI-12, that is, from seasonal scale to interannual scale, with the increase of time scale, the distribution of the extreme value of drought frequency moved to the southwest, semi-arid, and arid areas. The frequency of the four drought levels showed light drought > middle drought > severe drought > extreme drought in all time scales and all zones.