Abstract:

Based on the measured data from ground monitoring meteorological stations in Gansu province, this paper used the standardized precipitation evaporation index (SPEI) to explore the temporal and spatial evolution characteristics of meteorological drought at the annual and seasonal scales in Gansu. Scatter plots and correlation coefficients were used to reveal the correlation between drought changes and climatic factors. The Gumbel−copula function was selected to construct a joint distribution model of SPEI and precipitation at the annual scale in Gansu province, to explore and identify the spatio−temporal evolution characteristics of drought and the driving climatic factors, and to clarify the possibility of precipitation influencing dry and wet changes. The results showed that: (1) from 1984 to 2019, the change in precipitation (P) was not significant, while the average temperature (T) showed a significant upward trend, and potential evapotranspiration (ET₀) showed a significant increase in Gansu province. (2) The annual−scale drought index in Gansu showed a non−significant downward trend, and it tended to become drier over the years. The overall drought trend tended to be stable. The severity of drought in the Hexi region was more severe than in other areas of Gansu province, and the area around Zhangye had suffered the most severe droughts for many years. (3) The order of drought severity in the four seasons was spring, summer, autumn and winter. The drought in spring was the most severe. The drought severity in the Hexi region was more severe in summer and autumn than in spring and winter, while the Longdong region and Longnan region showed more severe drought in spring and winter. (4) During the research period, the increase in precipitation across the province had raised the possibility of less severe droughts. The possibility of the maximum values of annual−scale SPEI and precipitation occurring simultaneously was 91.60%, showing a high degree of correlation. The maximum possibilities of light drought, moderate drought, severe drought and extreme drought were 80.38%, 61.15%, 38.62% and 18.81%, respectively. 

Key words: Gansu province, Meteorological drought, Spatiotemporal variation, Climatic factor, Response characteristics