Global changes in extreme events: regional and seasonal dimension
Global changes in extreme events: regional and seasonal dimension
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DOI：
10.1007/s10584-011-0122-9
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发表时间：
2012-02-01
期刊：
影响因子：
4.8
通讯作者：
Seneviratne, Sonia I.
中科院分区：
文献类型：
--
作者：
Orlowsky, Boris;Seneviratne, Sonia I.
本研究系统地分析了完整的IPCC AR4（CMIP3）集合的GCM模拟在21世纪末的极端事件特征的变化相比，目前的条件。它通过调查更全面的数据库并考虑年度时间尺度之外的季节变化来补充以前的研究。与以前的研究一样，GCM之间的一致性对于与温度有关的极端事件通常很高，表明温暖的日子和热浪长度增加，而寒冷的极端事件减少。然而，我们发现了用于量化热浪长度的指数选择的问题，这些指数总体上不会影响变化的迹象，但会强烈影响热浪特征预测变化的幅度和模式。预测的极端降水量和干燥度的变化比极端气温的变化更不明确，尽管有一些强有力的特征，如地中海地区的干燥度增加和北方高纬度地区的强降水增加。我们还发现，预计的干燥度变化的评估取决于指数的选择，模型显示出较少的协议，土壤水分的变化比常用的“连续干旱日”指数，这是基于降水数据。最后，对极端温度分位数变化与全球、区域和季节变暖的比例关系的分析表明，大部分极端分位数变化是由于区域年平均变暖的季节性比例关系。这强调了季节性时间尺度对极端事件的重要性。在某些区域和季节，陆地尺度上温度极端分位数的变化与全球年平均温度变化的系数超过2，这意味着即使对于通常讨论的全球升温2A摄氏度的目标，几个国家的极端值也会发生很大变化。
This study systematically analyzes the complete IPCC AR4 (CMIP3) ensemble of GCM simulations with respect to changes in extreme event characteristics at the end of the 21st century compared to present-day conditions. It complements previous studies by investigating a more comprehensive database and considering seasonal changes beside the annual time scale. Confirming previous studies, the agreement between the GCMs is generally high for temperature-related extremes, indicating increases of warm day occurrences and heatwave lengths, and decreases of cold extremes. However, we identify issues with the choice of indices used to quantify heatwave lengths, which do overall not affect the sign of the changes, but strongly impact the magnitude and patterns of projected changes in heatwave characteristics. Projected changes in precipitation and dryness extremes are more ambiguous than those in temperature extremes, despite some robust features, such as increasing dryness over the Mediterranean and increasing heavy precipitation over the Northern high latitudes. We also find that the assessment of projected changes in dryness depends on the index choice, and that models show less agreement regarding changes in soil moisture than in the commonly used 'consecutive dry days' index, which is based on precipitation data only. Finally an analysis of the scaling of changes of extreme temperature quantiles with global, regional and seasonal warming shows that much of the extreme quantile changes are due to a seasonal scaling of the regional annual-mean warming. This emphasizes the importance of the seasonal time scale also for extremes. Changes in extreme quantiles of temperature on land scale with changes in global annual mean temperature by a factor of more than 2 in some regions and seasons, implying large changes in extremes in several countries, even for the commonly discussed global 2A degrees C-warming target.