Predictability of the summer East Asian upper-tropospheric westerly jet in ENSEMBLES multi-model forecasts
Predictability of the summer East Asian upper-tropospheric westerly jet in ENSEMBLES multi-model forecasts
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DOI：
10.1007/s00376-015-5057-z
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发表时间：
2015-10
影响因子：
5.8
通讯作者：
Chaofan Li;Zhongda Lin
中科院分区：
文献类型：
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作者：
Chaofan Li;Zhongda Lin
东亚对流层上层西风急流（EAJ）的年际变化对东亚夏季气候有重要影响。验证其在模式预报中的表现，可能为我们从对流层上层环流的角度理解东亚夏季气候异常的可预报性提供另一个视角。这项研究提出了一个全面的评估EAJ的回顾性季节性预测的基础上，从5月1日开始，在1960年至2005年期间ENSEMBLES的五个国家的最先进的耦合模型的年度变化。结果表明，耦合模式对东亚急流的年际位移具有一定的描述能力，反映了模式在第一主导经验正交函数（Empirical Orthogonal Function，EAJ）模式下的表现。这种能力主要表现在东亚-日本轴心以南地区。此外，模式一般捕捉到的主要特征的大气环流和SST异常相关的年际EAJ纬向位移。进一步的分析表明，热带东太平洋和北方印度洋同期海温的异常是东亚西风带南移的潜在预报能力的两个主要来源。与此相反，模式是无能为力的，在描述的东亚赤道轴以北地区的变化，与纬向位移，和年际强度变化的东亚赤道，第二个领先的纬向模态，这意味着它仍然是一个挑战，以更好地预测东亚赤道，随后，东亚夏季气候，使用当前耦合模式。
The interannual variation of the East Asian upper-tropospheric westerly jet (EAJ) significantly affects East Asian climate in summer. Identifying its performance in model prediction may provide us another viewpoint, from the perspective of upper-tropospheric circulation, to understand the predictability of summer climate anomalies in East Asia. This study presents a comprehensive assessment of year-to-year variability of the EAJ based on retrospective seasonal forecasts, initiated from 1 May, in the five state-of-the-art coupled models from ENSEMBLES during 1960–2005. It is found that the coupled models show certain capability in describing the interannual meridional displacement of the EAJ, which reflects the models’ performance in the first leading empirical orthogonal function (EOF) mode. This capability is mainly shown over the region south of the EAJ axis. Additionally, the models generally capture well the main features of atmospheric circulation and SST anomalies related to the interannual meridional displacement of the EAJ. Further analysis suggests that the predicted warm SST anomalies in the concurrent summer over the tropical eastern Pacific and northern Indian Ocean are the two main sources of the potential prediction skill of the southward shift of the EAJ. In contrast, the models are powerless in describing the variation over the region north of the EAJ axis, associated with the meridional displacement, and interannual intensity change of the EAJ, the second leading EOF mode, meaning it still remains a challenge to better predict the EAJ and, subsequently, summer climate in East Asia, using current coupled models.