Intraseasonal variability of the tropical Pacific subsurface temperature in the two flavors of El Niño
Intraseasonal variability of the tropical Pacific subsurface temperature in the two flavors of El Niño
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两种厄尔尼诺现象中热带太平洋地下温度的季节内变化
DOI：
10.1002/joc.4389
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Dunxin Hu
中科院分区：
文献类型：
--
作者：
Junqiao Feng;Qingye Wang;Shijian Hu;Dunxin Hu
利用观测资料和1.5层线性简化重力模型，研究了赤道太平洋两种El Niño（即典型或东太平洋（EP） El Niño和中太平洋（CP） El Niño）相关的次表层海洋温度（STA）季节内变率（ISV）的空间结构和时间演变。结果表明，虽然两种El Niño都以季节内赤道开尔文波（IEKW）的形式沿温跃层振荡，但其ISV特征存在一定的差异，该开尔文波是在热带太平洋西部由与Madden-Julian涛动（MJO）相关的纬向风应力激发的。首先，在CP El Niño期间，STA ISV的优势模态周期大致分布在50 ~ 80天，光谱峰值出现在60 ~ 65天。EP El Niño期间STA ISV谱在75 ~ 80天内出现峰值。这表明CP El Niño中的波速比EP El Niño中的波速快。第二，ISV活动在EP El Niño发育阶段的前一个春季达到高峰，而在CP El Niño成熟期最活跃。③EP El Niño期间，最强的IEKW发生在日线附近的太平洋，在130 W以东由于强涡粘耗散而迅速衰减，而EP El Niño期间的IEKW则以相对弱的扩散从西太平洋向东太平洋有效传播。
ABSTRACT The spatial structure and temporal evolution of the intraseasonal variability (ISV) of the subsurface ocean temperature (STA) in the equatorial Pacific associated with the two flavours of El Niño [ie the canonical or eastern Pacific (EP) El Niño and the central Pacific (CP) El Niño] are investigated using observations and 1.5-layer linear reduced gravity model. Results suggest that the ISV characteristics show some differences in the two types of El Niño, although both oscillate along the thermocline in the form of the intraseasonal equatorial Kelvin wave (IEKW), which is excited in the western tropical Pacific by the zonal wind stress associated with the Madden-Julian oscillation (MJO). First, the period of dominant mode of the STA ISV during CP El Niño broadly distributes in 50-80 days with the spectra peaking in 60-65 days. By contrast, the spectrum of STA ISV during EP El Niño shows a peak in 75-80-day period. This indicates that the wave speed is faster in the CP El Niño than in EP El Niño. Second, the ISV activity peaks in previous spring during the developing phase of EP El Niño, whereas during CP El Niño it becomes the most active during the mature phase. Third, the strongest IEKW occurs in the CP around the dateline during CP El Niño and attenuates quickly east of 130 W due to strong eddy viscosity dissipation, while the IEKW during the EP El Niño propagates efficiently from the western to the eastern Pacific with a relative weak diffusion.