摘要：
极端气候事件是全球长期气候变化研究中的重要内容.作为世界第三极,青藏高原对气候变化和变异的响应非常敏感.本文基于青藏高原98个气象站(大部分位于海拔4000 m以上)的日值观测数据,包括日气温最大值、最小值和日降水量,计算了1960–2012年间的极端气候指数并分析了其时空变化格局.首先,根据国际气象组织的标准计算了15个核心气温极端指数和8个核心降水极端指数,然后从高原整体、生态区和台站尺度分析了极端指数的时空变化趋势.气温极端指数表明青藏高原整体表现为显著升温趋势,高原的冷日和冷夜时间序列呈下降趋势,每10年分别减少8.9天和17.3天.相应的暖日和暧夜增长趋势分别为7.6 d(10 yr)-1和12.5 d(10 yr)-1.生长季长度以5.3 d(10 yr)-1的速率增加.在站点尺度,大部分台站的气温极端指数存在显著趋势,但是空间分异性显著.生态区的气温极端指数与高原整体的发展趋势一致.高原整体的降水极端指数波动性较大,增长趋势微弱.年总降水增长趋势为2.8 mm(10 yr)-1.时序变化点分析表明极端气候指数的突变主要发生在1980和1990年代.赫斯特指数表明未来各种极端气候指数都将保持研究时间段内的发展趋势.另外,探索了极端气候指数与海拔高度的关系,发现各指数的变化趋势与高程并无显著相关性.总体上高原升温呈现显著的不对称特征,即气温冷指数的上升幅度明显大于暖指数的上升幅度,日最低气温的增长趋势也很显著.大多数降水极端指数表现为微弱的增加趋势(不显著).本研究综合分析了青藏高原极端气候的时空分布格局,可以为高原气候变化研究提供参考.%Extreme climate events play an important role in studies of long-term climate change. As the Earth's Third Pole, the Tibetan Plateau (TP) is sensitive to climate change and variation. In this study on the TP, the spatiotemporal changes in climate extreme indices (CEIs) are analyzed based on daily maximum and minimum surface air temperatures and precipitation at 98 meteorological stations, most with elevations of at least 4000 m above sea level, during 1960–2012. Fifteen temperature extreme indices (TEIs) and eight precipitation extreme indices (PEIs) were calculated. Then, their long-term change patterns, from spatial and temporal perspectives, were determined at regional, eco-regional and station levels. The entire TP region exhibits a significant warming trend, as reflected by the TEIs. The regional cold days and nights show decreasing trends at rates of ?8.9 d (10 yr)-1 (days per decade) and ?17.3 d (10 yr)-1, respectively. The corresponding warm days and nights have increased by 7.6 d (10 yr)-1 and 12.5 d (10 yr)-1, respectively. At the station level, the majority of stations indicate statistically significant trends for all TEIs, but they show spatial heterogeneity. The eco-regional TEIs show patterns that are consistent with the entire TP. The growing season has become longer at a rate of 5.3 d (10 yr)-1. The abrupt change points for CEIs were examined, and they were mainly distributed during the 1980s and 1990s. The PEIs on the TP exhibit clear fluctuations and increasing trends with small magnitudes. The annual total precipitation has increased by 2.8 mm (10 yr)-1 (not statistically significant). Most of the CEIs will maintain a persistent trend, as indicated by their Hurst exponents. The developing trends of the CEIs do not show a corresponding change with increasing altitude. In general, the warming trends demonstrate an asymmetric pattern reflected by the rapid increase in the warming trends of the cold TEIs, which are of greater magnitudes than those of the warm TEIs. This finding indicates a positive shift in the distribution of the daily minimum temperatures throughout the TP. Most of the PEIs show weak increasing trends, which are not statistically significant. This work aims to delineate a comprehensive picture of the extreme climate conditions over the TP that can enhance our understanding of its changing climate.
