Ocean-atmosphere interaction in the lifecycle of ENSO: The coupled wave oscillator
Ocean-atmosphere interaction in the lifecycle of ENSO: The coupled wave oscillator
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DOI：
10.1007/s11401-009-0072-y
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发表时间：
2009-08
期刊：
影响因子：
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通讯作者：
Jialin Lin
中科院分区：
文献类型：
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作者：
Jialin Lin
为了解释厄尔尼诺/南方涛动 (ENSO) 的振荡性质，许多 ENSO 理论强调在太平洋内传播/反射的自由海洋赤道波，或太平洋盆地平均海洋热含量的释放/补给。印度洋和大西洋的 ENSO 信号通常被认为是通过大气遥相关对太平洋海温异常的远程响应。本研究使用长期观测数据集调查赤道附近的 ENSO 生命周期。时空谱分析用于识别和隔离与 ENSO 相关的主要年际海洋和大气波模式。利用Nino3海温异常作为ENSO指数，并利用滞后相关/回归构建复合ENSO生命周期。详细研究了主要波模的传播、结构和反馈机制。结果表明，与ENSO相关的主要海洋赤道波模态不是自由波，而是两种海洋-大气耦合波，包括耦合开尔文波和耦合赤道罗斯贝(ER)波。这些波不仅限于太平洋，而且具有行星尺度，纬向波数为1-2，并在三年多的时间内绕赤道传播一圈，导致ENSO周期超过3年。当经过大陆时，它们变成解耦的大气波。耦合开尔文波比耦合ER波具有更大的方差，使得总信号以东向传播为主。表面纬向风应力 (x) 会减慢波浪速度。这两个耦合波通过边界反射和叠加相互作用，并且还通过边界反射和风应力强迫与北太平洋近赤道罗斯贝波沿15N相互作用。两个耦合波的降水异常在ENSO海温极大值后不久在东太平洋相遇，并激发干燥大气开尔文波，该波快速环绕整个赤道并导致对流层温度的纬向对称信号。印度洋和大西洋中的 ENSO 信号与两个耦合波以及快速大气开尔文波有关。太平洋盆地平均海洋热含量的释放/补给也由两个耦合波贡献。上述结果表明，针对 ENSO 的振荡性质，存在另一种耦合波振荡器机制。
To explain the oscillatory nature of El Nino/Southern Oscillation (ENSO), many ENSO theories emphasize the free oceanic equatorial waves propagating/reflecting within the Pacific Ocean, or the discharge/recharge of Pacific-basin-averaged ocean heat content. ENSO signals in the Indian and Atlantic oceans are often considered as remote response to the Pacific SST anomaly through atmospheric teleconnections. This study investigates the ENSO life cycle near the equator using long-term observational datasets. Space-time spectral analysis is used to identify and isolate the dominant interannual oceanic and atmospheric wave modes associated with ENSO. Nino3 SST anomaly is utilized as the ENSO index, and lag-correlation/regression are used to construct the composite ENSO life cycle. The propagation, structure and feedback mechanisms of the dominant wave modes are studied in detail. The results show that the dominant oceanic equatorial wave modes associated with ENSO are not free waves, but are two ocean-atmosphere coupled waves including a coupled Kelvin wave and a coupled equatorial Rossby (ER) wave. These waves are not confined only to the Pacific Ocean, but are of planetary scale with zonal wavenumbers 1–2, and propagate all the way around the equator in more than three years, leading to the longer than 3-year period of ENSO. When passing the continents, they become uncoupled atmospheric waves. The coupled Kelvin wave has larger variance than the coupled ER wave, making the total signals dominated by eastward propagation. Surface zonal wind stress (x) acts to slow down the waves. The two coupled waves interact with each other through boundary reflection and superposition, and they also interact with an off-equatorial Rossby wave in north Pacific along 15N through boundary reflection and wind stress forcing. The precipitation anomalies of the two coupled waves meet in the eastern Pacific shortly after the SST maximum of ENSO and excite a dry atmospheric Kelvin wave which quickly circles the whole equator and leads to a zonally symmetric signal of troposphere temperature. ENSO signals in the Indian and Atlantic oceans are associated with the two coupled waves as well as the fast atmospheric Kelvin wave. The discharge/recharge of Pacific-basin-averaged ocean heat content is also contributed by the two coupled waves. The above results suggest the presence of an alternative coupled wave oscillator mechanism for the oscillatory nature of ENSO.