基于R/S分析和Mann-Kendall检验的定西市气温降水变化特征

黄土丘陵区生态脆弱、环境恶劣，对气候变化的响应复杂而敏感。研究以地处黄土丘陵区西南缘的定西市为研究对象，采用线性方程、5 a滑动平均、Mann-Kendall突变检验、R／S分析等方法，基于逐日气象数据，以此分析定西市1960—2004年间气温和降水的动态变化，以期为该地区合理开展农业生产和植被恢复提供依据。结果表明:（1）温度方面，45 a来，定西市气温呈上升趋势，其Hurst指数H > 0.5，表明在之后的一定时段内气温将持续上升，1994年为定西市气温突变开始的时间；同时，升温速率表现出明显的季节性差异；定西市极端气候变化显著，最大增温趋势出现在冬季，暖冬现象较为明显。（2）降水方面，1960年以来定西市降水量呈下降趋势，且以夏秋季下降为主，降水量变化无明显的突变现象，其Hurst指数H < 0.5，说明未来将呈现反持续性趋势。定西市未来气候将由暖干型向暖湿型转变。

Analysis on the Variation of Temperature and Precipitation in Dingxi Based on R/S and Mann-Kendall Test

The loess hilly region has long been characterized by its fragile ecosystem and deteriorated environment. The local natural conditions are very sensitive to climate change. Dingxi, located in the southwest of the Loess Plateau, was selected as a typical example to detect the basic features of local climate variation. Linear equation, 5-year moving-average, climatic tendency, Mann-Kendall test and R/S analysis methods were used to analyze the meteorological data. Results showed that: (1) the temperature gradually increased during the past 45 years and would continue to increase with the Hurst index greater than 0.5; the temperature was testified to rise by a clear abrupt in 1994; meanwhile, the increase rate of temperature differed in different seasons, extreme climate events were confirmed in Dingxi during the monitored years; it increased sharply in winter, showing an obvious warm-winter phenomenon; (2) the precipitation had decreased gradually since 1960s, particularly during the summer and autumn periods, no abrupt changes were detected, and the Hurst index was less than 0.5, indicating that the precipitation will tend to increase in the forthcoming years. Generally, the climate in Dingxi region possibly will transfer from warm-dry to warm-wet conditions.