近44a四川地区极端气候变化趋势及特征分析

Extreme climatic change trend and features in Sichuan for the latest 44 years

利用1971-2014年四川省140个站点逐日气温和降水资料,结合气候变化检测与极端事件指数专家组公布的部分极端气候指数,分析了四川地区近44 a极端气温和极端降水事件的年际变化趋势和空间分布特征,并对部分极端气温指数进行旋转经验正交函数(REOF)分析.结果表明,四川地区的极端暖指数T_(N90)、T_(X90)等分别以0.62和0.7 d/a的变化呈上升趋势,极端冷指数T_(N10)、T_(X10)等分别以-0.56和-0.26 d/a的变化呈下降趋势,表明四川地区变暖趋势明显;日极端气温T_(Xx)(0.04℃/a)、T_(Xn)(0.03℃/a)、T_(Nx)(0.02℃/a)和T_(Nn)(0.03℃/a)均呈微弱上升趋势,表明发生极端气温事件的概率有所增加.四川地区的整体雨量在近44 a略有下降,下降幅度为-0.794 mm/a;从连续干旱日数和连续湿润日数等极端降水指数分析,除川西高原有增湿趋势以外,全川大部分地区有暖干化的趋势;R_(X1d)、R_(X5d)和尼。等指数的下降趋势表明降水的集中程度略微减弱.REOF结果表明大地形对气温变化有显著影响,虽然整体变化趋势一致,但四川西部高原与东部盆地存在明显区别,西部T_(N10)、T_(X90)的变化幅度均弱于盆地地区.

Using daily temperature and precipitation data from 140 stations in Sichuan for the period of1971-2014 and adopting indices of extreme climate published by CCl/CLF/AR/JCOMM expert team on climate change detection and indices,change characteristics and distribution of temperature and precipitation extremes were analyzed and methods of rotated empirical orthogonal function（REOF） were employed to analyze temperature extremes,with the results that the hot extreme indices including TN90,TX90had increased by 0.62 and 0.7 d/a respectively,the cold extreme indices including TN10,TxX10 decreased by-0.56 and-0.26 d/a,respectively.It indicated that Sichuan had shown an obvious warming trend.The weak increase of TXx（0.04 ℃/a）,TXn（0.03 ℃/a）,TNx（0.02 ℃/a） and TNn（0.03 ℃/a） showed that the risks of extreme climate events would be higher.A long-term trend of precipitation in the recent 44 years was decreasing and the decreasing amplitude was-0.794 mm/a.The change of extreme precipitation indices including consecutive dry days and consecutive wet days indicated that most areas of Sichuan had shown a drying trend while the plateau areas had a wetting trend;the decrease of RX1d,RX5d and R20 indicated that precipitation was less concentrated.The result of REOF showed that large orography had a significant impact on the temperature changes.Although the overall changing trend of extreme temperature indices was consistent,there were significantly differences between the western plateau and eastern basin of Sichuan：the magnitudes of changes in Tn10 snd TX90 in the western plateau were obviously lower than in the eastern basin.