Causes of the 2011-14 California Drought*
Causes of the 2011-14 California Drought*
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DOI：
10.1175/jcli-d-14-00860.1
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发表时间：
2015-09-01
影响因子：
4.9
通讯作者：
Henderson, Naomi
中科院分区：
文献类型：
--
作者：
Seager, Richard;Hoerling, Martin;Henderson, Naomi
利用7个大气模式的观测资料和集合模拟，分析了2011/12-2013/14年11 - 4月加州干旱的成因。从历史上看，干燥的加州冬季通常与西海岸的山脊有关，但没有明显的SST强迫。潮湿的冬季通常与西海岸的槽和厄尔尼诺事件有关。七个模型中的许多模型都捕捉到了干燥和潮湿冬季的这些属性。根据这些模型，SST强迫可以解释加州冬季降水方差的三分之一。SST强迫是维持西海岸高压脊和抑制三个冬季降水的关键。在2011/12年，这是对拉尼娜事件的响应，而在2012/13年和2013/14年，它似乎与热带西冷东太平洋海温模式有关。所有模式都包含一种将这种热带太平洋SST异常与北美西海岸外的一个带脊波列联系起来的变率模式。这种模态解释的方差小于ENSO和太平洋年代际变率，其在2012/13和2013/14年的重要性是不寻常的。CMIP（CMIP 5）第5阶段的模型预测温室气体的增加将导致加州整个冬季降水量的变化，与最近的干旱异常相比，这种变化非常小。然而，长期变暖趋势可能导致干旱期间地表水分不足。因此，干旱期间的降水量不足主要是由自然变率，这一结论是通过讨论观测到的和模拟的热带SST趋势之间的差异得出的。
The causes of the California drought during November-April winters of 2011/12-2013/14 are analyzed using observations and ensemble simulations with seven atmosphere models forced by observed SSTs. Historically, dry California winters are most commonly associated with a ridge off the west coast but no obvious SST forcing. Wet winters are most commonly associated with a trough off the west coast and an El Nino event. These attributes of dry and wet winters are captured by many of the seven models. According to the models, SST forcing can explain up to a third of California winter precipitation variance. SST forcing was key to sustaining a high pressure ridge over the west coast and suppressing precipitation during the three winters. In 2011/12 this was a response to a La Nina event, whereas in 2012/13 and 2013/14 it appears related to a warm west-cool east tropical Pacific SST pattern. All models contain a mode of variability linking such tropical Pacific SST anomalies to a wave train with a ridge off the North American west coast. This mode explains less variance than ENSO and Pacific decadal variability, and its importance in 2012/13 and 2013/14 was unusual. The models from phase 5 of CMIP (CMIP5) project rising greenhouse gases to cause changes in California all-winter precipitation that are very small compared to recent drought anomalies. However, a long-term warming trend likely contributed to surface moisture deficits during the drought. As such, the precipitation deficit during the drought was dominated by natural variability, a conclusion framed by discussion of differences between observed and modeled tropical SST trends.