Abstract:Frequent droughts caused serious impacts on ecological resources and agricultural development. In order to reveal the spatial and temporal evolution characteristics of drought in Shanxi Province, based on the month-by-month meteorological data from 24 meteorological stations in Shanxi Province from 1971 to 2020, the annual trends of each meteorological factor were examined by using the improved Mann-Kendall method, and the FAO56 Penman-Monteith formula was used to calculate the reference crop evapotranspiration (ET0) of reference crop emergence, analyze the characteristics of ET0 and its sensitivity to meteorological factors under the changes of individual meteorological factors, and compare the ability of different drought indices (percentage of precipitation anomaly (Pa), standardized precipitation index (SPI), and standardized precipitation evapotranspiration index (SPEI)) in monitoring drought hazards in Shanxi Province at various time scales (monthly, seasonal, and annual scales). The results showed that ET0 was negatively correlated with relative humidity, and the sensitivity of meteorological factors to ET0 was in descending order of relative humidity, daily maximum temperature, wind speed at 2m, daily minimum temperature, daily average temperature, with a fluctuating and decreasing trend of ET0. SPEI was able to reflect the drought condition of Shanxi Province effectively in multiple time scales, which was an effective tool for drought monitoring in this region. Comparing the three drought indices at monthly, seasonal and annual scales, Pa was less effective in detecting droughts, SPI and SPEI differed significantly in some geographic regions, and overall, SPEI performed better in detecting droughts in most regions; at the SPEI-1 scale, the frequency of each drought class in descending order was light drought (14.8%), moderate drought (10.6%), severe drought (5.6%), extreme drought (1.9%), with the highest occurrence rate of drought in March (34%) and the lowest in December (31.8%), and more severe drought conditions in Lüliang City, Jinzhong City, and Datong City; under the SPEI-3 scale, the frequency of seasonal drought, in descending order, was in the fall (33.5%), summer (32.5%), spring (31.9%), and winter (31.4%), and Datong City, Changzhi City had the highest frequency of special drought and the most serious drought, and Xinzhou City, Shuozhou City, and Lüliang City had the highest frequency of light, moderate, and severe drought, respectively; at the SPEI-12 scale, the frequencies of light, moderate, severe, and special drought were 14.8%, 10.5%, 5.4%, and 2.3%, respectively, and SPEI-12 recognized more sites with severe and special drought compared with SPEI-1 and SPEI-3, and based on the travel theory, it was concluded that the frequency of drought in southern Shanxi Province was higher than that of other provinces in China. It was concluded that the frequency of drought was more frequent in the southern part of Shanxi Province, the drought in the eastern part lasted longer and the severity of drought was greater, and the peak of drought mainly occurred in the northern and southern parts of Shanxi Province. Due to the fluctuating decline of the mean annual precipitation and the overall increase of the mean annual temperature, the climate in Shanxi Province tended to be warm and dry, the drought in the southern and northern parts of Shanxi Province would be aggravated, the drought in the central part of Shanxi Province would be slowed down, and the whole-area drought was still very possible.
