Contrasting Eastern-Pacific and Central-Pacific Types of ENSO
Contrasting Eastern-Pacific and Central-Pacific Types of ENSO
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DOI：
10.1175/2008jcli2309.1
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发表时间：
2009-02-01
影响因子：
4.9
通讯作者：
Yu, Jin-Yi
中科院分区：
文献类型：
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作者：
Kao, Hsun-Ying;Yu, Jin-Yi
利用地面观测资料和次表层海洋同化资料，对比了热带太平洋两种不同类型的厄尔尼诺-南方涛动（ENSO）：东太平洋型（EP）和中太平洋型（CP）。采用经验正交函数分析和线性回归相结合的分析方法对这两种类型进行了分离。基于主成分的相关和合成分析，这两种ENSO类型的结构，演变和遥相关进行了研究。EP型ENSO的海温距平中心位于南美洲沿岸的赤道东太平洋。这类ENSO与海盆温跃层和地面风的变化有关，并与热带印度洋有较强的遥相关。相反，CP型ENSO的大部分地面风、SST和次表层异常都局限在中太平洋，并且倾向于原地发生、发展和衰减。这种类型的ENSO似乎与温跃层变化关系不大，可能更多地受大气强迫的影响。与南印度洋有较强的遥相关。在EP-ENSO的异常演变过程中可以识别出位相反转特征，而CP-ENSO的异常演变过程中则不能识别出位相反转特征。这意味着CP-ENSO可能更多地作为事件或时期而不是作为一个周期发生。1976/77年前后，EP-ENSO的年代际变化较强，其海温距平的优势周期由2年移到4年，而CP-ENSO的优势周期则在2年带附近。这两种类型的ENSO爆发时间的不同意味着EP型和CP型ENSO的差异可能是由触发ENSO事件的机制的时间造成的。
Surface observations and subsurface ocean assimilation datasets are examined to contrast two distinct types of El Nino-Southern Oscillation (ENSO) in the tropical Pacific: an eastern-Pacific (EP) type and a central-Pacific (CP) type. An analysis method combining empirical orthogonal function (EOF) analysis and linear regression is used to separate these two types. Correlation and composite analyses based on the principal components of the EOF were performed to examine the structure, evolution, and teleconnection of these two ENSO types. The EP type of ENSO is found to have its SST anomaly center located in the eastern equatorial Pacific attached to the coast of South America. This type of ENSO is associated with basinwide thermocline and surface wind variations and shows a strong teleconnection with the tropical Indian Ocean. In contrast, the CP type of ENSO has most of its surface wind, SST, and subsurface anomalies confined in the central Pacific and tends to onset, develop, and decay in situ. This type of ENSO appears less related to the thermocline variations and may be influenced more by atmospheric forcing. It has a stronger teleconnection with the southern Indian Ocean. Phase-reversal signatures can be identified in the anomaly evolutions of the EP-ENSO but not for the CP-ENSO. This implies that the CP-ENSO may occur more as events or epochs than as a cycle. The EP-ENSO has experienced a stronger interdecadal change with the dominant period of its SST anomalies shifted from 2 to 4 yr near 1976/77, while the dominant period for the CP-ENSO stayed near the 2-yr band. The different onset times of these two types of ENSO imply that the difference between the EP and CP types of ENSO could be caused by the timing of the mechanisms that trigger the ENSO events.