Pacific Decadal Oscillation: Tropical Pacific Forcing versus Internal Variability
Pacific Decadal Oscillation: Tropical Pacific Forcing versus Internal Variability
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DOI：
10.1175/jcli-d-18-0164.1
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发表时间：
2018-09
影响因子：
4.9
通讯作者：
Yu Zhang;S. Xie;Y. Kosaka;Jun‐Chao Yang
中科院分区：
文献类型：
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作者：
Yu Zhang;S. Xie;Y. Kosaka;Jun‐Chao Yang
太平洋年代际振荡（PDO）是北太平洋（20°N以北）海表温度（SST）变化的主导模态。南太平洋（20°S以南）对应的是南太平洋十年涛动（SPDO）。利用一个10人集合热带太平洋起搏器试验，研究了热带东太平洋（TEP）SST强迫和内部大气变率对PDO和SPDO的影响。每个成员强迫的历史辐射强迫和观测到的SST异常的TEP区域。在TEP区域之外，海洋和大气完全耦合并自由演变。TEP强迫PDO（54%的方差）和SPDO（46%的方差）在时间上是相关的，并表现出对称的结构，由太平洋-北美（PNA）和太平洋-南美遥相关，分别驱动的赤道。内部PDO类似于TEP强迫分量，但与北方半球环形模态和PNA模式相关的内部阿留申低（AL）变率有关。在阿留申群岛附近的西风急流出口区，正压能量转换使内部变率局部增强。相反，正压能量转换与内部SPDO的联系较弱，导致海平面气压变率的地理偏好性较弱。因此，内部SPDO与TEP强迫分量不同，其特征是与南半球环形模态相关的沿着~60°S的SST异常。从观察隔离内部组件的局限性进行了讨论。具体而言，内部PDO的变化似乎有助于显着的北太平洋政权在20世纪40年代的转变。
The Pacific decadal oscillation (PDO) is the leading mode of sea surface temperature (SST) variability over the North Pacific (north of 20°N). Its South Pacific counterpart (south of 20°S) is the South Pacific decadal oscillation (SPDO). The effects of tropical eastern Pacific (TEP) SST forcing and internal atmospheric variability are investigated for both the PDO and SPDO using a 10-member ensemble tropical Pacific pacemaker experiment. Each member is forced by the historical radiative forcing and observed SST anomalies in the TEP region. Outside the TEP region, the ocean and atmosphere are fully coupled and freely evolve. The TEP-forced PDO (54% variance) and SPDO (46% variance) are correlated in time and exhibit a symmetric structure about the equator, driven by the Pacific–North American (PNA) and Pacific–South American teleconnections, respectively. The internal PDO resembles the TEP-forced component but is related to internal Aleutian low (AL) variability associated with the Northern Hemisphere annular mode and PNA pattern. The internal variability is locally enhanced by barotropic energy conversion in the westerly jet exit region around the Aleutians. By contrast, barotropic energy conversion is weak associated with the internal SPDO, resulting in weak geographical preference of sea level pressure variability. Therefore, the internal SPDO differs from the TEP-forced component, featuring SST anomalies along ~60°S in association with the Southern Hemisphere annular mode. The limitations on isolating the internal component from observations are discussed. Specifically, internal PDO variability appears to contribute significantly to the North Pacific regime shift in the 1940s.