Abstract: Southern Taihang Mountain area is an important part of the key ecological regions along the Yellow River in China. Understanding the climate change trend in this area is of significance for the maintenance of ecological security and the planning and decision-making of major ecological projects in the Yellow River Basin. Taking Jiyuan City in southern Taihang Mountain area as the research area, we analyzed the climate change trend in Jiyuan based on the meteorological data from 1980 to 2019. The results showed that climate in Jiyuan tended to be warmer and wetter during the study period. The change rates of temperature and precipitation were 0.48 ℃·(10 a)^-1 and 14.21 mm·(10 a)^-1, respectively. The rise of temperature in spring and summer was higher than that in autumn and winter. Climate was warmer and drier in spring, while warmer and wetter in the other three seasons. Potential evapotranspiration and aridity index showed increasing and decreasing trends, with the average value of 748 mm and 1.36, respectively. The first and last days ≥10 ℃ were about 3 days in advance and 1 day in delay every 10 years. The change rate of effective accumulated temperature ≥10 ℃, duration days ≥10 ℃ and high temperature days were 116.57 ℃·(10 a)^-1, 4 d·(10 a)^-1, and 5 d·(10 a)^-1, respectively. The 1990s was the driest decade in Jiyuan during the study period, with strongest increases of temperature. Half of the years showed the characteristics of semi-arid climate in that decade. From 2010 to 2019, the trend of climate warming and wetting in Jiyuan had accelerated significantly, which was the warmest and wettest decade. In recent 10 years, duration days ≥10 ℃ and the effective accumulated temperature increased by about 28 days and 389.36 ℃, respectively. The frequency and intensity of high temperature weather also increased significantly in this decade.

Key words: climate change, potential evapotranspiration, aridity index, effective accumulated temperature, high temperature days