Detectable Changes in the Frequency of Temperature Extremes
Detectable Changes in the Frequency of Temperature Extremes
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DOI：
10.1175/jcli-d-11-00678.1
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发表时间：
2013-03-01
影响因子：
4.9
通讯作者：
Christidis, Nikolaos
中科院分区：
文献类型：
--
作者：
Morak, Simone;Hegerl, Gabriele C.;Christidis, Nikolaos
这项研究确定了最近观察到的陆地上冷热极端频率的变化是否可以用气候变率来解释，或者它们是否对外部影响表现出可检测的反应。作者分析了中极端日温度频率的变化，即超过日最低温度（分别为tn 90和tn 10）和日最高温度（分别为tx 90和tx 10）第90百分位数的天数和未达到第10百分位数的天数，包括冷季和暖季。分析是在一系列的空间尺度上进行的，并分别为北方寒冷和温暖的季节数据。外部强迫的指纹来自哈德利中心全球环境模式第1版（HadGEM 1）的模拟集合，包括人为和自然强迫。观测结果显示，在两个季节和几乎所有地区，暖极端事件增加，冷极端事件减少，模型通常很好地捕捉到了这一点。模式和观测之间的某些区域差异可能是由于当地强迫或气候动力学的变化。检测分析，使用优化和非优化的指纹，表明外部强迫的影响是可检测的观测的寒冷和温暖的极端，寒冷和温暖的季节，在1951-2003年期间在5%的水平。在北方和南方半球以及分析的大多数区域中也可分别检测到。该模型显示出一种倾向，显着高估了白天极端温暖的变化，特别是在夏季。
This study determines whether observed recent changes in the frequency of hot and cold extremes over land can be explained by climate variability or whether they show a detectable response to external influences. The authors analyze changes in the frequency of moderate-to-extreme daily temperatures-namely, the number of days exceeding the 90th percentile and the number of days not reaching the 10th percentile of daily minimum (tn90 and tn10, respectively) and maximum (tx90 and tx10, respectively) temperature-for both cold and warm seasons. The analysis is performed on a range of spatial scales and separately for boreal cold- and warm-season data. The fingerprint for external forcing is derived from an ensemble of simulations produced with the Hadley Centre Global Environmental Model, version 1 (HadGEM1), with both anthropogenic and natural forcings. The observations show an increase in warm extremes and a decrease in cold extremes in both seasons and in almost all regions that are generally well captured by the model. Some regional differences between model and observations may be due to local forcings or changes in climate dynamics. A detection analysis, using both optimized and nonoptimized fingerprints, shows that the influence of external forcing is detectable in observations for both cold and warm extremes, and cold and warm seasons, over the period 1951-2003 at the 5% level. It is also detectable separately for the Northern and Southern Hemispheres, and over most regions analyzed. The model shows a tendency to significantly overestimate changes in warm daytime extremes, particularly in summer.