Two key parameters for the El Nio continuum: zonal wind anomalies and Western Pacific subsurface potential temperature
Two key parameters for the El Nio continuum: zonal wind anomalies and Western Pacific subsurface potential temperature
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DOI：
10.1007/s00382-015-2550-0
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发表时间：
2015-12-01
期刊：
影响因子：
4.6
通讯作者：
Graf, Hans-F.
中科院分区：
文献类型：
--
作者：
Lai, Andy Wang-Chun;Herzog, Michael;Graf, Hans-F.
最近讨论了不同类型的厄尔尼诺（EN）事件。基于NCEP-NOAA再分析数据，该分析探讨了1980-2013年期间导致一系列EN类型的一些关键参数。根据海表温度异常（SSTA）的时空演变，将ENE事件分为三种类型：中太平洋（CPEN）、东太平洋（EPEN）和混合型（HBEN）。我们发现，EN是一个连续的事件谱与CPEN和EPEN作为终端成员。该谱主要取决于两个关键参数：130 A度E-160 A度E西太平洋5-250米次表层海洋位温距平（通常为1月和2月）约1年前EN事件，和140 A度E-160 A度W累积纬向风距平（ZWA）之间的开始和EN事件的峰值。使用这两个参数，在不同的Nio区域实现的最大SSTA的总方差的大约70%已经可以解释最大SSTA发生之前的6个月。这为ENSO预测提供了相当简单的可能性。作为EPEN演变的必要条件，西太平洋处于补充状态。西太平洋强而持续的西风异常可以触发开尔文波向东太平洋传播。两个参数，位温和纬向风距平，建设性干扰。对于CPEN，这些参数不太重要。开尔文波的传播不参与事件的演变。相反，中太平洋变暖是由纬向平流反馈和当地的海气相互作用引起的，这在以前的研究中已经证明。当两个参数以不同的方式相互干扰时，HBEN就会发生：（1）西太平洋荷电较弱，但西风ZWA较强，使中太平洋赤道上升流减弱，而Kelvin波的触发作用较弱，影响不明显;（2）西太平洋荷电较强，但只有弱西风ZWA发展，因此Kelvin波不能完全延伸到最东太平洋。
Different types of El Nio (EN) events have recently been discussed. Based on NCEP-NOAA reanalysis data this analysis explores a number of key parameters that cause a range of EN types over the period 1980-2013. EN events are divided into three types depending on the spatial and temporal evolution of the sea surface temperature anomalies (SSTA): Central Pacific (CPEN), Eastern Pacific (EPEN), and Hybrid (HBEN). We find that EN is a continuous spectrum of events with CPEN and EPEN as the end members. This spectrum mainly depends on two key parameters: the 130A degrees E-160A degrees E Western Pacific 5-250 m subsurface oceanic potential temperature anomaly about 1 year before the EN peak (typically January and February), and the 140A degrees E-160A degrees W cumulative zonal wind anomaly (ZWA) between onset and peak of the EN event. Using these two parameters, about 70 % of the total variance of the maximum SSTA realised in different Nio regions can already be explained up to 6 months before the maximum SSTA occurs. This offers a rather simple potential for ENSO prediction. A necessary condition for the evolution of an EPEN, the Western Pacific is in the recharged state. Strong and sustained westerly wind anomalies in Western Pacific can then trigger a Kelvin wave propagating to the eastern Pacific. Both parameters, potential temperature and zonal wind anomaly, constructively interfere. For a CPEN, these parameters are much less important. Kelvin wave propagation is not involved in the evolution of the event. Instead, the Central Pacific warming is caused locally by a zonal advection feedback and local air-sea interaction as already demonstrated in previous studies. The HBEN occurs when both parameters interfere in different ways: (1) Western Pacific is weakly charged, but strong westerly ZWA are observed that reduce the equatorial upwelling in the Central Pacific while the triggered Kelvin wave is too weak to have a significant effect; (2) Western Pacific is strongly charged but only weak westerly ZWA develop, so that the resulting Kelvin wave cannot fully extend into the eastern-most Pacific.