两种类型的印度洋偶极子外文翻译资料

 2022-11-15 16:40:40

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两种类型的印度洋偶极子

Satoru Endo1 · Tomoki Tozuka1

摘要：印度洋偶极子（IOD）被称为热带印度洋的气候模式，伴随着东部（西部）极在其正相期间的负（正）海表温度（SST）异常。然而，IOD的西部并不总是完全由正SST异常覆盖。因此，在本研究中，基于西部的SST异常，IOD进一步分为两类。第一种类型（以下称“传统型IOD”）与东部（中部到西部）热带印度洋的负（正）SST异常有关。另一方面，第二种类型（以下称“Modoki型IOD”）与东部和西部热带印度洋的负SST异常和中部热带印度洋的正SST异常有关。在综合分析的基础上，发现在传统型IOD中，异常东风覆盖了整个赤道印度洋，因此在东非观测到了正的降雨异常。此外，由于整个海域的东风异常，传统型IOD伴随着强烈的海表面高度（SSH）异常。相反，Modoki型IOD的纬向风异常是在热带印度洋中部汇合，东非没有明显的降水异常。此外，只能看到弱的SSH异常，因为西部的西风异常所引起的赤道下行异常被东部的东风异常所造成的赤道上升异常所抵消。

The Indian Ocean Dipole （IOD） is known as a climate mode in the tropical Indian Ocean accompanied by negative （positive） sea surface temperature （SST） anomalies over the eastern （western） pole during its positive phase. However, the western pole of the IOD is not always covered totally by positive SST anomalies. For this reason, the IOD is further classified into two types in this study based on SST anomalies in the western pole. The first type（hereafter “canonical IOD”） is associated with negative（positive） SST anomalies in the eastern （central to western）tropical Indian Ocean. The second type （hereafter “IODModoki”）, on the other hand, is associated with negative SST anomalies in the eastern and western tropical Indian Ocean and positive SST anomalies in the central tropical Indian Ocean. Based on composite analyses, it is found that easterly wind anomalies cover the whole equatorial Indian Ocean in the canonical IOD, and as a result, positive rainfall anomalies are observed over East Africa. Also, due to the basin-wide easterly wind anomalies, the canonical IOD is accompanied by strong sea surface height （SSH）anomalies. In contrast, zonal wind anomalies converge in the central tropical Indian Ocean in the IOD Modoki, and no significant precipitation anomalies are found over East Africa. Also, only weak SSH anomalies are seen, because equatorial downwelling anomalies induced by westerly wind anomalies in the west are counteracted by equatorial upwelling anomalies caused by easterly wind anomalies in the east.）

1.引言：

最近，不同类型的气候模式受到越来越多的关注。在热带太平洋，Ashok等人（2007）已经确定了一种新型的厄尔尼诺——南方涛动（ENSO），他们将其命名为ENSO Modoki。与东热带太平洋存在暖海表温度（SST）异常的典型厄尔尼诺相比，Modoki型厄尔尼诺则是与热带太平洋中部的暖海温异常和热带太平洋西部、东部的冷海温异常有关。两种不同种类的ENSO由于其不同的遥相关模式（Weng等人，2007）和对当地海平面变化的影响（Behera和Yamagata，2010）引起了大量的关注。此外，ENSO Modoki的发生或幅度可能会在全球变暖的情况下增加（Yeh等人2009; Ashok和Yamagata 2009; Kim和Yu 2012），尽管最近出现的增加现象可能是自然变率的一部分（Yeh et al.2011; Newman） et al.2011; McPhaden et al.2011; Kim et al.2012）。与热带太平洋的情况相反，不同类型的气候模式，如印度洋偶极子（IOD; Saji等人，1999），在热带印度洋尚未得到很多研究。然而，有一些研究侧重于IOD的演变差异。 Rao和Yamagata（2004）和Rao等人（2009）指出存在“中止的IOD”，其中，IOD的突然终止是由于季节内扰动产生的下行开尔文波。最近，Du等人（2013）根据IOD的演变将IOD事件分为三类。根据他们的定义，正常的IOD事件主要在北半球的秋季发展和成熟，而过早的IOD事件主要在北半球的夏季发展和成熟，延长的IOD事件在北半球的夏季发展并在北半球的秋季成熟。然而，迄今为止没有研究是基于SST异常的空间模式对IOD进行分类的。例如，图1显示了过去几十年中在两个主要IOD事件的峰值阶段观察到的SST异常。尽管在1994年和1997年的事件中苏门答腊都发现了强烈的负SST异常，但在前一次事件中可以在印度洋中部（非洲东部）发现正（负）SST异常，而热带印度洋在后一事件中，正的海温异常覆盖了中部和西部的热带印度洋。由于已知IOD会影响印度洋边缘国家的降水（Behera等人2005; Ummenhofer等人2009; Cai等人2009; Pourasghar等人2012）和偏远地区（Guan和Yamagata 2003; Saji）和Yamagata 2003; Behera等人2013），SST异常模式的差异可能会改变这些气候影响。这是本次研究的主要动机。在这里，我们介绍了一种基于SST异常的空间模式识别两种类型IOD的方法，并描述了与每种类型相关的海洋和大气异常。我们还研究了两种类型的IOD对热带印度洋边缘国家的影响差异。本研究的结构顺序如下。下一节将简要介绍观测数据和同化产物。在第三节，我们根据SST异常的空间模式差异将IOD事件分为两类。然后，我们基于第四节中的综合分析描述了两种类型的IOD。最后一节是总结主要结果。

Different flavors of climate modes have received more and more attentions recently. In the tropical Pacific, Ashok et al. （2007） have identified a new type of El Nintilde;o/Southern Oscillation （ENSO）, which they named ENSO Modoki. In contrast to canonical El Nintilde;o with warm sea surface temperature （SST） anomalies over the eastern tropical Pacific, El Nintilde;o Modoki is associated with warm SST anomalies in the central tropical Pacific and cold SST anomalies in the western and eastern tropical Pacific. Two different flavors of ENSO attracted much attention owing to different teleconnection patterns （Weng et al. 2007） and impacts on local sea level changes （Behera and Yamagata 2010）. Also, occurrence/amplitude of ENSO Modoki may increase under global warming （Yeh et al. 2009; Ashok and Yamagata 2009; Kim and Yu 2012）, although the recent increase may be a part of natural variability （Yeh et al. 2011; Newman et al. 2011; McPhaden et al. 2011;Kim et al. 2012）. In contrast to the situation in the tropical Pacific, different flavors of climate modes, such as the Indian Ocean Dipole （IOD; Saji et al. 1999）, have not been studied much in the tropical Indian Ocean. However, there are some studies focusing on differences in evolution of the IOD. Rao and Yamagata （2004） and Rao et al. （2009） pointed out the existence of “aborted IOD”, in which the IOD was abruptly terminated by downwelling Kelvin waves generated by intraseasonal disturbances. More recently, Du et al. （2013） classified IOD events into three types based on their evolution. According to their definition, normal IOD events develop and mature mostly in boreal fall, whereas unseasonable IOD events develop and mature mostly in boreal summer and prolonged IOD events develop in boreal summer and mature in boreal fall. However, no study to date classified the IOD based on spatial patterns of SST anomalies. Figure 1, for example, shows SST anomalies observed at the peak phase of two major IOD events in the past few decades. Although strong negative SST anomalies are found off Sumatra both in the 1994 and 1997 events, positive （negative） SST anomalies can be found in the central Indian Ocean （off East Africa） in the former event, while positive SST anomalies cover the central and western tropical Indian Ocean in the latter event. Since the IOD is known to influence precipitation over both the Indian Ocean rim countries （Behera et al. 2005; Ummenhofer et al. 2009; Cai et al. 2009; Pourasghar et al. 2012） and remote areas （Guan and Yamagata 2003; Saji and Yamagata 2003; Behera et al. 2013）, differences in SST anomaly patterns may modify these climatic impacts. This is the main motive of this

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