Teleconnections between Ethiopian rainfall variability and global SSTs: observations and methods for model evaluation
Teleconnections between Ethiopian rainfall variability and global SSTs: observations and methods for model evaluation
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DOI：
10.1007/s00703-016-0466-9
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发表时间：
2017-04-01
影响因子：
2
通讯作者：
Bewket, Woldeamlak
中科院分区：
文献类型：
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作者：
Degefu, Mekonnen Adnew;Rowell, David P.;Bewket, Woldeamlak
埃塞俄比亚的降雨变率对旱作农业和水力发电有重大影响，因此了解其与缓慢变化的全球海面温度（SSTs）的关系对预测具有潜在的重要意义。我们提供了在埃塞俄比亚这些远程连接的季节性和空间变异性的概述。采用准客观方法确定了埃塞俄比亚海温降水遥相关的连贯季节和区域。我们确定了三个季节（3 - 5月，MAM； 7 - 9月，JAS； 10 - 11月，ON），它们与气候降雨总量相似。我们还确定了三个新的区域（埃塞俄比亚中部和西部，西南埃塞俄比亚；埃塞俄比亚南部，南埃塞俄比亚；埃塞俄比亚东北部，东北埃塞俄比亚），它们与之前基于不同的海温降水遥相关定义的区域相补充，这些区域在预测年际异常时很有用。非洲-埃塞俄比亚上空的JAS降雨与赤道东太平洋和印度洋上空的海温呈负相关。在以前发现的整个东非的区域细节的基础上增加了新的区域细节，特别是南埃塞俄比亚的降水与赤道东太平洋海温和印度洋偶极子（IOD）正相关。此外，其他季节区域的海温与降雨量的相关性，特别是所有地区的MAM，被发现可以忽略不计。在HadGEM2和HadGEM3-GA3.0耦合气候模式中，这些遥相关的表示显示出混合技能。除了HadGEM2和HadGEM3-GA3.0的低分辨率（N96）版本更好地代表IOD与S-Ethiopian ON降雨之间的关系外，这两个模型都不能很好地代表统计学上显著的遥相关。此外，这两种模式都能够反映埃塞俄比亚其他季节和其他地区缺乏海温降水相关性。
Rainfall variability in Ethiopia has significant effects on rainfed agriculture and hydropower, so understanding its association with slowly varying global sea surface temperatures (SSTs) is potentially important for prediction purposes. We provide an overview of the seasonality and spatial variability of these teleconnections across Ethiopia. A quasi-objective method is employed to define coherent seasons and regions of SST-rainfall teleconnections for Ethiopia. We identify three seasons (March-May, MAM; July-September, JAS; and October-November, ON), which are similar to those defined by climatological rainfall totals. We also identify three new regions (Central and western Ethiopia, CW-Ethiopia; Southern Ethiopia, S-Ethiopia; and Northeast Ethiopia, NE-Ethiopia) that are complementary to those previously defined here based on distinct SST-rainfall teleconnections that are useful when predicting interannual anomalies. JAS rainfall over CW-Ethiopia is negatively associated with SSTs over the equatorial east Pacific and Indian Ocean. New regional detail is added to that previously found for the whole of East Africa, in particular that ON rainfall over S-Ethiopia is positively associated with equatorial east Pacific SSTs and with the Indian Ocean Dipole (IOD). Also, SST-to-rainfall correlations for other season-regions, and specifically for MAM in all regions, are found to be negligible. The representation of these teleconnections in the HadGEM2 and HadGEM3-GA3.0 coupled climate models shows mixed skill. Both models poorly represent the statistically significant teleconnections, except that HadGEM2 and the low resolution (N96) version of HadGEM3-GA3.0 better represent the association between the IOD and S-Ethiopian ON rainfall. Additionally, both models are able to represent the lack of SST-rainfall correlation in other seasons and other parts of Ethiopia.