The impact of ENSO and the NAO on extreme winter precipitation in North America in observations and regional climate models
The impact of ENSO and the NAO on extreme winter precipitation in North America in observations and regional climate models
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DOI：
10.1007/s00382-016-3148-x
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发表时间：
2017-03
期刊：
影响因子：
4.6
通讯作者：
K. Whan;F. Zwiers
中科院分区：
文献类型：
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作者：
K. Whan;F. Zwiers
利用非平稳广义极值分布，以北大西洋涛动(NAO)和厄尔尼诺-南方涛动(ENSO)指数为协变量，分析了北美冬季降水与北大西洋涛动(NAO)和厄尔尼诺-南方涛动(ENSO)指数的关系。这两个协变量对降水都有显著的影响，两个区域气候模式(RCM)CANRCM4和CRCM5都能很好地模拟这一影响。观测到的NAO对北美东部极端降水的影响最大，在NAO正位相下，北半球出现负位相极端降水事件的可能性减小，南部出现负位相极端降水事件的可能性增加。区域协调机制总体上很好地模拟了这一模式，尽管在影响程度上存在一些差异，特别是在五大湖以南地区。在厄尔尼诺条件下，拉尼娜级别的极端事件更有可能发生在加利福尼亚州和美国南部，而在加拿大大部分地区和五大湖以南地区发生的可能性较小。这一广泛的模式也得到了RCM的很好模拟，但它们没有捕捉到加州增加的可能性。在一些地方，尽管使用了相同的侧边界条件和动力核心，但RCM对来自协变量的外部强迫的极端降水响应具有相反的符号。这证明了模式物理对极端降水遥相关的重要性。
The relationship between winter precipitation in North America and indices of the North Atlantic Oscillation (NAO) and El Niño–Southern Oscillation (ENSO) is evaluated using non-stationary generalized extreme value distributions with the indices as covariates. Both covariates have a statistically significant influence on precipitation that is well simulated by two regional climate models (RCMs), CanRCM4 and CRCM5. The observed influence of the NAO on extreme precipitation is largest in eastern North America, with the likelihood of a negative phase extreme rainfall event decreased in the north and increased in the south under the positive phase of the NAO. This pattern is generally well simulated by the RCMs although there are some differences in the extent of influence, particularly south of the Great Lakes. A La Niña-magnitude extreme event is more likely to occur under El Niño conditions in California and the southern United States, and less likely in most of Canada and a region south of the Great Lakes. This broad pattern is also simulated well by the RCMs but they do not capture the increased likelihood in California. In some places the extreme precipitation response in the RCMs to external forcing from a covariate is of the opposite sign, despite use of the same lateral boundary conditions and dynamical core. This demonstrates the importance of model physics for teleconnections to extreme precipitation.