Atmospheric Internal Variability in the Summer Indo–Northwestern Pacific: Role of the Intraseasonal Oscillation
Atmospheric Internal Variability in the Summer Indo–Northwestern Pacific: Role of the Intraseasonal Oscillation
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DOI：
10.1175/jcli-d-19-0794.1
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发表时间：
2020-03
影响因子：
4.9
通讯作者：
Xudong Wang;S. Xie;Z. Guan
中科院分区：
文献类型：
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作者：
Xudong Wang;S. Xie;Z. Guan
夏季印度-西北太平洋（NWP）大气年际变率与热带海表温度（SST）变率耦合。本研究调查的重要性和印度NWP地区的大气内部变率的起源。利用再分析资料和30层大气模式的模拟结果，利用月相关的经验正交函数分析方法，在北半球夏季的印度洋-NWP区域识别出两个与SST相关的年际模态。第一个模态与起源于赤道东太平洋的厄尔尼诺-南方涛动有关，而第二个模态的特征是厄尔尼诺后夏季NWP区域的异常反气旋（AAC），称为印度-西太平洋海洋电容器。SST诱导的模态从6月到8月表现出时间上的持续性。残差变异性是本研究的重点。剩余变率的主导模式显示AAC结构的NWP，但很少逐月持续，表明大气内部动力无关的SST强迫。进一步的研究表明，月内AAC来自夏季季节内振荡（ISO）。ISO的宽波段产生非零的月平均值，强烈地投射到AAC模式上。最后，对2016年夏季降水和低层环流异常进行了分析。2016年7月的AAC到8月的异常气旋的低层环流形势的逆转是由于ISO引起的内部变率。
Summer atmospheric interannual variability in the Indo–northwestern Pacific (NWP) is coupled with tropical sea surface temperature (SST) variability. This study investigates the importance and origin of atmospheric internal variability in the Indo-NWP region. Using the reanalysis and the 30-member atmospheric model simulation, two SST-related interannual modes are identified in the Indo-NWP region during boreal summer with the month-reliant empirical orthogonal function analysis. The first mode is related to concurrent El Niño–Southern Oscillation originating from the eastern equatorial Pacific whereas the second mode features an anomalous anticyclone (AAC) in post–El Niño summers over the NWP region, known as the Indo-western Pacific Ocean capacitor. The SST-induced modes show temporal persistence from June to August. The residual variability is the focus of this study. The dominant mode of the residual variability displays an AAC structure over the NWP but little month-to-month persistence, indicative of atmospheric internal dynamics unrelated to SST forcing. Further investigation suggests the monthly internal AAC arises from the summer intraseasonal oscillation (ISO). The broad band of ISO yields nonzero monthly means that project strongly onto the AAC pattern. Finally, the anomalies of rainfall and low-level circulation in summer 2016 are investigated. The reversal of the low-level circulation pattern from an AAC in July to an anomalous cyclone over the NWP in August 2016 is due to the ISO-induced internal variability.