El Ni?o，La Ni?a，and the nonlinearity of their teleconnections

Hoerling，MP； Kumar，A； Zhong，M

Nonlinearity and asymmetry of ENSO

An，SI； Jin，F(xiàn)F

ENSO as an integrating concept in Earth science

McPhaden，Michael J； Zebiak，Stephen E； Glantz，Michael H

The impact of global warming on the tropical Pacific ocean and El Ni?o

Collins，Mat； An，Soon-ll； Cai，Wenju； et al.

兩類ENSO事件分類的研究進(jìn)展*

董宇佳，孟祥鳳

（中國(guó)海洋大學(xué) 海洋環(huán)境學(xué)院，山東青島266100）

近百年來的ENSO事件及其強(qiáng)度

王紹武，龔道溢

熱點(diǎn)追蹤

厄爾尼諾

·編者按·

按照國(guó)家氣候中心ENSO監(jiān)測(cè)標(biāo)準(zhǔn)，當(dāng)赤道中東太平洋海水表面溫度持續(xù)6個(gè)月以上比常年同期偏高0.5℃以上，則確認(rèn)為一次新的厄爾尼諾事件正式形成.2014年5月到現(xiàn)在（2015年7月），赤道東太平洋海溫距平持續(xù)增暖（超過0.5℃）已經(jīng)達(dá)到15個(gè)月，暖海溫最大中心位于赤道東太平洋，中心強(qiáng)度超過 3.0℃.基于氣候動(dòng)力和統(tǒng)計(jì)模式預(yù)測(cè)以及診斷分析結(jié)果，預(yù)計(jì)當(dāng)前的厄爾尼諾事件將至少持續(xù)發(fā)展到2015/2016年冬季，強(qiáng)度將達(dá)到強(qiáng)厄爾尼諾事件標(biāo)準(zhǔn).這次厄爾尼諾對(duì)全球和我國(guó)的天氣和氣候形成顯著的影響，2015年5月份以來，我國(guó)南方暴雨頻繁，北方出現(xiàn)高溫天氣，今年入汛以來，連續(xù)13輪強(qiáng)降雨襲擊我國(guó)南方，尤其進(jìn)入6月后，特大暴雨在長(zhǎng)江中下游地區(qū)和西南地區(qū)愈演愈烈；印度高溫仍在繼續(xù)，各地的部分地區(qū)氣溫達(dá)到了48℃；2015年3月以來朝鮮半島降水比常年偏少2～6成，旱情不斷發(fā)展；5月底，美國(guó)得克薩斯州休斯敦市遭受強(qiáng)風(fēng)暴襲擊，布蘭科河發(fā)生1929年以來最大洪水，造成多人死亡；經(jīng)歷了近85年來最嚴(yán)重干旱的巴西近日旱澇急轉(zhuǎn)、暴雨成災(zāi).

厄爾尼諾（西班牙語(yǔ)：El Ni?o），又稱圣嬰現(xiàn)象，是秘魯、厄瓜多爾一帶的漁民用以稱呼一種異常氣候現(xiàn)象的名詞.主要指太平洋東部和中部的熱帶海洋的海水溫度異常地持續(xù)變暖，使全球氣候模態(tài)發(fā)生變化，造成一些地區(qū)干旱而另一些地區(qū)又降雨量過多.正常情況下，熱帶太平洋區(qū)域的季風(fēng)洋流是從美洲走向亞洲，使西太平洋海水表面保持溫暖，給印尼周圍帶來熱帶降雨.但這種模態(tài)每2～7年會(huì)發(fā)生一次異?，F(xiàn)象，使赤道太平洋風(fēng)向和洋流發(fā)生逆轉(zhuǎn)，海洋表層的熱流就轉(zhuǎn)而向東走向美洲，隨之便帶走了熱帶降雨，使西太平洋等地區(qū)出現(xiàn)大面積干旱，這就是“厄爾尼諾現(xiàn)象”.拉尼娜（西班牙語(yǔ)：La Ni?a），是厄爾尼諾現(xiàn)象的反相，也稱為“反厄爾尼諾”或“冷事件”，它是指赤道附近東太平洋水溫反常下降的一種現(xiàn)象，表現(xiàn)為東太平洋明顯變冷，同時(shí)也伴隨著全球性氣候異常，總是出現(xiàn)在厄爾尼諾現(xiàn)象之后.

對(duì)厄爾尼諾現(xiàn)象形成的原因，目前學(xué)術(shù)界還沒有定論.但有一點(diǎn)可以肯定，即它們是海-氣相互作用過程中平衡遭到破壞所致，是海-氣系統(tǒng)在全球范圍內(nèi)的異常現(xiàn)象.在正常狀況下，北半球赤道附近吹東北信風(fēng)，南半球赤道附近吹東南信風(fēng).信風(fēng)帶動(dòng)海水自東向西流動(dòng)，分別形成北赤道洋流和南赤道暖流.從赤道東太平洋流出的海水，靠下層上升涌流補(bǔ)充，從而使這一地區(qū)下層冷水上翻，水溫低于四周，形成赤道太平洋東西部海溫差.但是，一旦東南信風(fēng)減弱，就會(huì)造成太平洋地區(qū)的冷水上翻減少或停止，海水溫度就升高，形成大范圍的海水溫度異常增暖.而突然增強(qiáng)的這股暖流沿著厄瓜多爾海岸南侵，使海水溫度劇升，冷水魚群因而大量死亡，海鳥因找不到食物而紛紛離去，漁場(chǎng)頓時(shí)失去生機(jī)，使沿岸國(guó)家遭到巨大損失.目前，對(duì)于厄爾尼諾事件發(fā)展形成的原因以及冷暖位相的轉(zhuǎn)換機(jī)制主要有不穩(wěn)定海氣耦合模態(tài)理論、延遲振子理論、充放電振子理論和隨機(jī)強(qiáng)迫理論.近年來的一些研究還發(fā)現(xiàn)厄爾尼諾事件的發(fā)生與地球自轉(zhuǎn)速度變化有關(guān).

面對(duì)厄爾尼諾，如何趨利避害是全球各國(guó)共同面臨的問題.國(guó)家氣候中心的專家針對(duì)此次厄爾尼諾提出了應(yīng)對(duì)方案：要做好防范極端天氣氣候事件的準(zhǔn)備，各地應(yīng)作好暴雨洪澇、高溫干旱等氣象災(zāi)害以及極端天氣氣候事件的防御準(zhǔn)備；江南、華南部分地區(qū)須加強(qiáng)防范暴雨洪澇，西南、西北部分地區(qū)須防御氣象干旱；應(yīng)該注重綜合監(jiān)測(cè)、預(yù)測(cè)包括厄爾尼諾在內(nèi)的多種因素的變化，防范可能發(fā)生的災(zāi)害，爭(zhēng)取做到趨利避害.

本專題得到了秦大河院士（中國(guó)氣象局）、李維京研究員（中國(guó)氣象局國(guó)家氣候中心）、陳文研究員（中國(guó)氣象局國(guó)家氣候中心）的大力支持.

·熱點(diǎn)數(shù)據(jù)排行·

截至2015年6月20日，中國(guó)知網(wǎng)（CNKI）和Web of Science（WOS）的數(shù)據(jù)報(bào)告顯示，以“厄爾尼諾（El Ni?o）或ENSO暖事件（ENSO Warm Events）”為詞條可以檢索到的期刊文獻(xiàn)分別為1614與1701條，本專題將相關(guān)數(shù)據(jù)按照：研究機(jī)構(gòu)發(fā)文數(shù)、作者發(fā)文數(shù)、期刊發(fā)文數(shù)、被引用頻次進(jìn)行排行，結(jié)果如下.

研究機(jī)構(gòu)發(fā)文數(shù)量排名（CNKI）

研究機(jī)構(gòu)發(fā)文數(shù)量排名（WOS）

作者發(fā)文數(shù)量排名（CNKI）

作者發(fā)文數(shù)量排名（WOS）

期刊發(fā)文數(shù)量排名（CNKI）

期刊發(fā)文數(shù)量排名（WOS）

根據(jù)中國(guó)知網(wǎng)（CNKI）數(shù)據(jù)報(bào)告，以“厄爾尼諾”或“ENSO暖事件”為詞條可以檢索到的高被引論文排行結(jié)果如下.

國(guó)內(nèi)數(shù)據(jù)庫(kù)高被引論文排行

根據(jù)Web of Science統(tǒng)計(jì)數(shù)據(jù)，以“El Ni?o”或“ENSO Warm Events”為詞條可以檢索到的高被引論文排行結(jié)果如下.

國(guó)外數(shù)據(jù)庫(kù)高被引論文排行

·經(jīng)典文獻(xiàn)推薦·

基于Web of Science檢索結(jié)果，利用Histcite軟件選取LCS（Local Citation Score，本地引用次數(shù)）TOP 30文獻(xiàn)作為節(jié)點(diǎn)進(jìn)行分析，得到本領(lǐng)域推薦的經(jīng)典文獻(xiàn)如下.

來源出版物：Geophysical Research Letters，1996，23（1）： 57-60

El Ni?o，La Ni?a，and the nonlinearity of their teleconnections

Hoerling，MP； Kumar，A； Zhong，M

Abstract： The paradigm of an atmospheric system varying linearly with respect to extreme phases of the EI Ni?o-Southern Oscillation is questioned. It is argued that the global response to tropical Pacific sea surface temperature forcing will be inherently nonlinear. A physical basis far this intrinsic nonlinearity is the thermodynamic control on deep convection. Climate statistics for warm and cold events of the tropical Pacific are analyzed separately for the northern winter periods during 1950-1996. Composite analysis of 500-mb heights reveal planetary-scale teleconnection patterns，as noted in earlier studies. A new result is the evidence for an appreciable 35 degrees longitude phase shift between the warm and cold event circulation composites，and the two wave trains appear to have different tropical origins. A large nonlinear component in North American surface climate anomalies is also found，which is consistent with such a phase shift in teleconnections. In the Tropics，rainfall anomalies also show evidence of nonlinear behavior. The maximum rain anomalies along the equator are located east of the date line during warm events，but west of the date line during cold events. The interpretation of this behavior is complicated，however，by the fact that composite warm event SST anomalies are not the exact inverse of their cold event counterparts. Idealized atmospheric general circulation model（AGCM）experiments are performed in order to test the question of whether the observed nonlinearity is an intrinsic property of the atmospheric system. The model is forced with a composite SST anomaly that undergoes a realistic seasonally varying ENSO life cycle，as described by E. Rasmusson and T. Carpenter. Both positive and negative phases of the SST anomaly are used，and a 40-member ensemble of warm and cold event model simulations is conducted. A nonlinear climate response in the AGCM is found that closely resembles the observed composites，including a shift in the equatorial positions of the maxmium rain responses and a phase shift of teleconnection patterns in the upper troposphere. Barotropic model experiments indicate that the inherent nonlinearity in the tropical rain response may itself be responsible for the phase shift in the extratropical teleconnection patterns.

來源出版物：Journal of Climate，1997，10（8）： 1769-1786

Nonlinearity and asymmetry of ENSO

An，SI； Jin，F(xiàn)F

Abstract： El Ni?o events（warm）are often stronger than La Ni?a events（cold）. This asymmetry is an intrinsic nonlinear characteristic of the El Ni?o-Southern Oscillation（ENSO）phenomenon. In order to measure the nonlinearity of ENSO，the maximum potential intensity（MPI）index and the nonlinear dynamic heating（NDH）of ENSO are proposed as qualitative and quantitative measures. The 1997/98 El Ni?o that was recorded as the strongest event in the past century and another strong El Ni?o event in 1982/83 nearly reached the MPI. During these superwarming events，the normal climatological conditions of the ocean and atmosphere were collapsed completely. The huge bursts of ENSO activity manifested in these events are attributable to the nonlinear dynamic processes. Through a heat budget analysis of the ocean mixed layer it is found that throughout much of the ENSO episodes of 1982/83 and 1997/98，the NDH strengthened these warm events and weakened subsequent La Ni?a events. This led to the warm-cold asymmetry. It is also found that the eastward-propagating feature in these two El Ni?o events provided a favorable phase relationship between temperature and current that resulted in the strong nonlinear dynamical warming. For the westward-propagating El Ni?o events prior to the late 1970s（e.g.，1957/58 and 1972/73 ENSOs）the phase relationships between zonal temperature gradient and current and between the surface and subsurface temperature anomalies are unfavorable for nonlinear dynamic heating，and thereby the ENSO events are not strong.

Keywords： Ni?o-southern-oscillation； sea-surface temperature； ocean-atmosphere model； tropical pacific-ocean； El-Ni?o； equatorial pacific； interannual variability； climate variability； coupled model； La-Ni?o

來源出版物：Journal of Climate，2004，17（12）： 2399-2412聯(lián)系郵箱：An，SI； sian@hawaii.edu

ENSO as an integrating concept in Earth science

McPhaden，Michael J； Zebiak，Stephen E； Glantz，Michael H

Abstract： The El Ni?o-Southern Oscillation（ENSO）cycle of alternating warm El Ni?o and cold La Ni?a events is the dominant year-to-year climate signal on Earth. ENSO originates in the tropical Pacific through interactions between the ocean and the atmosphere，but its environmental and socioeconomic impacts are felt worldwide. Spurred on by the powerful 1997-1998 El Ni?o，efforts to understand the causes and consequences of ENSO have greatly expanded in the past few years. These efforts reveal the breadth of ENSO’s influence on the Earth system and the potential to exploit its predictability for societal benefit. However，many intertwined issues regarding ENSO dynamics，impacts，forecasting，and applications remain unresolved. Research to address these issues will not only lead to progress across a broad range of scientific disciplines but also provide an opportunity to educate the public and policy makers about the importance of climate variability and change in the modern world.

Keywords： 1997-1998 EL-NI?O； sea-surface temperatures； southern-oscillation； LA-NINA； multimodel ensembles； climate forecasts；tropical pacific； united-states； ocean； evolution

來源出版物：Science，2006，314（5806）： 1740-1745聯(lián)系郵箱：McPhaden，Michael J； michael.j.mcphaden@noaa.gov

The impact of global warming on the tropical Pacific ocean and El Ni?o

Collins，Mat； An，Soon-ll； Cai，Wenju； et al.

Abstract： The El Ni?o-Southern Oscillation（ENSO）is a naturally occurring fluctuation that originates in the tropical Pacific region and affects ecosystems，agriculture，freshwater supplies，hurricanes and other severe weather events worldwide. Under the influence of global warming，the mean climate of the Pacific region will probably undergo significant changes. The tropical easterly trade winds are expected to weaken； surface ocean temperatures are expected to warm fastest near the equator and more slowly farther away； the equatorial thermocline that marks the transition between the wind-mixed upper ocean and deeper layers is expected to shoal； and the temperature gradients across the thermocline are expected to become steeper. Year-to-year ENSO variability is controlled by a delicate balance of amplifying and damping feedbacks，and one or more of the physical processes that are responsible for determining the characteristics of ENSO will probably be modified by climate change. Therefore，despite considerable progress in our understanding of the impact of climate change on many of the processes that contribute to El Ni?o variability，it is not yet possible to say whether ENSO activity will be enhanced or damped，or if the frequency of events will change.

Keywords： general-circulation model； sea-surface temperature； ENSO amplitude changes； climate-change； coupled models； atmospheric variability； multimodel ensemble； equatorial pacific； instability-wave； part I

來源出版物：Nature Geoscience，2010，3（6）： 391-397聯(lián)系郵箱：Collins，M； matthew.collins@metoffice.gov.uk

·推薦綜述·

兩類ENSO事件分類的研究進(jìn)展*

董宇佳，孟祥鳳

（中國(guó)海洋大學(xué) 海洋環(huán)境學(xué)院，山東青島266100）

厄爾尼諾-南方濤動(dòng)（El Ni?o-Southern Oseillation，即ENSO）是熱帶太平洋上最顯著的海氣藕合信號(hào)，也被認(rèn)為是年際氣候變化中的最強(qiáng)信號(hào)，它對(duì)全球大氣環(huán)流和氣候變化有顯著影響，已經(jīng)引起了各國(guó)政府和科學(xué)家的關(guān)注.Bjerknes［1］最早把厄爾尼諾和南方濤動(dòng)聯(lián)系起來，提出這兩者事實(shí)上是熱帶太平洋大尺度海氣相互作用的一個(gè)現(xiàn)象的兩個(gè)方面，指出應(yīng)該用大氣和海洋雙向藕合的觀點(diǎn)解析ENSO，這一理論為后來的ENSO研究奠定了重要基礎(chǔ).

Rasmusson and Carpenter［2］對(duì)1951—1972年之間發(fā)生的6次El Ni?o事件進(jìn)行合成分析的結(jié)果表明El Ni?o事件發(fā)生時(shí)海溫增暖首先在南美沿岸出現(xiàn)，然后沿赤道向西傳播.符涂斌等［3］指出除增溫首先出現(xiàn)在赤道東太平洋的傳統(tǒng)El Ni?o事件以外，還存在另一種增溫出現(xiàn)在赤道中太平洋的El Ni?o事件.傳統(tǒng)的El Ni?o事件首先從赤道東太平洋南美沿岸海域開始增溫，然后向西傳播至赤道中太平洋，一般情況下不會(huì)超過日界線.但是20世紀(jì)80年代以來的許多El Ni?o事件表現(xiàn)出了不同以往的特點(diǎn)，特別是21世紀(jì)發(fā)生的El Ni?o事件基本上都不同于傳統(tǒng)的El Ni?o事件，主要表現(xiàn)在其增溫首先出現(xiàn)在赤道中太平洋，然后向東傳播至赤道東太平洋南美沿岸.這兩類El Ni?o事件對(duì)全球氣候造成了不同的強(qiáng)烈影響，因而近年來頻繁發(fā)生的非傳統(tǒng)El Ni?o事件成為科學(xué)家們感興趣的熱點(diǎn)問題.有研究認(rèn)為，中太平洋El Ni?o事件是傳統(tǒng)El Ni?o事件發(fā)生發(fā)展的一個(gè)階段［4］，但是更多學(xué)者則認(rèn)為這兩類事件之間是相互獨(dú)立的［5-8］.到目前為止，學(xué)者們針對(duì)兩類ENSO提出了多種不同的分類方法，本文嘗試對(duì)這些分類方法進(jìn)行總結(jié).

1兩類ENSO事件的特征

關(guān)于兩類El Ni?o事件分別有多種不同的命名，一般將傳統(tǒng)El Ni?o事件稱為典型El Ni?o、冷舌El Ni?o或東太平洋El Ni?o；而將非傳統(tǒng)El Ni?o事件稱為El Ni?o Modoki［5］、日界線El Ni?o［6-7］、中太平洋El Ni?o［9-10］或暖池El Ni?o［11］.雖然對(duì)非傳統(tǒng)El Ni?o事件采用的稱呼不一致，但是這些研究基本上描述的是同一現(xiàn)象.

傳統(tǒng)El Ni?o事件的海表增暖（Sea Surface Temperature Anomaly，SSTA）主要出現(xiàn)在赤道東太平洋及南美沿岸附近（圖1a），海溫異常有顯著的傳播特征.這類El Ni?o事件的發(fā)展過程受到整個(gè)太平洋海盆尺度變化的影響，并同熱帶印度洋有很強(qiáng)的遙相關(guān).傳統(tǒng)El Ni?o事件主要以2～7a周期年際變化為主，同時(shí)也存在如1976/1977年氣候躍遷前后的年代際變化［12］.

非傳統(tǒng)El Ni?o事件海表增暖主要出現(xiàn)在赤道中太平洋（圖1b），在赤道中太平洋表現(xiàn)為暖異常.這類El Ni?o事件的海溫異常、表面風(fēng)異常和次表層異常都局限于中太平洋，主要在局地發(fā)生、發(fā)展及消亡，不存在明顯的傳播特征.另外，這類ENSO事件不涉及溫躍層變化，更多的是受大氣驅(qū)動(dòng)的影響.非傳統(tǒng)El Ni?o事件除具有年際時(shí)間尺度的信號(hào)以外還具有年代際時(shí)間尺度的信號(hào)，近年來這類事件的發(fā)生頻率顯著增加，這可能與全球氣候變暖有關(guān)［9］.此外，兩類ENSO事件均有很好的季節(jié)鎖相特征，雖然開始時(shí)間有所不同，但是峰值基本出現(xiàn)在秋末到冬初時(shí)期［13］.

2兩類ENSO事件的判定

2.1定性角度

早期的研究主要從定性角度，通過比較兩類事件海表溫度異常的主要出現(xiàn)區(qū)域、最初發(fā)生時(shí)間、最初開始的位置等特點(diǎn)來粗略判定ENSO事件類型.

符涂斌［3］等比較早的提出了El Ni?o事件存在兩種類型，通過對(duì)Fleet數(shù)值海洋中心的整編資料（FCDS）以及實(shí)時(shí)船舶觀測(cè)資料進(jìn)行分析，得到了El Ni?o事件發(fā)生時(shí)期赤道太平洋存在兩種類型增暖的結(jié)論：一種增暖主要位于東太平洋，稱之為“東部型”；另一種增暖主要位于日界線附近，稱之為“西部型”.減恒范等［14］根據(jù)海溫異常發(fā)生的時(shí)間對(duì)ENSO事件進(jìn)行了分類，將明顯的海溫異常開始于上半年（1～6月）的ENSO事件歸為第一類，將明顯的海溫異常開始于下半年（7～12月）的ENSO事件歸為第二類.Xu等［15］認(rèn)為，春季開始的El Ni?o事件其合成SSTA暖中心位于東赤道太平洋，而夏季開始的El Ni?o事件其合成SSTA暖中心位于赤道中太平洋，即東太平洋El Ni?o事件開始于春季，中太平洋El Ni?o事件開始于夏季.林學(xué)椿等［16］對(duì)ENSO事件進(jìn)行了個(gè)例分析，得到不同海水增（降）溫過程的兩類El Ni?o（反El Ni?o事件）事件，將增（降）溫最先發(fā)生在赤道太平洋130?W以東的ENSO事件定義為東部型，將增（降）溫最先發(fā)生在赤道太平洋130?W以西的ENSO事件定義為中部型.

Ni?o3指數(shù)與Ni?o4指數(shù)分別為SSTA在Ni?o3區(qū)域和Ni?o4區(qū)域的區(qū)域平均值，Kug等［11］基于這兩個(gè)傳統(tǒng)對(duì)兩類事件進(jìn)行了定性劃分，他們指出可以通過比較它們的振幅相對(duì)大小來區(qū)分兩類ENSO事件，當(dāng)兩個(gè)指數(shù)中的任意一個(gè)大于其相應(yīng)的標(biāo)準(zhǔn)偏差時(shí)定義為一次El Ni?o事件，當(dāng)Ni?o3指數(shù)大于Ni?o4指數(shù)時(shí)為冷舌El Ni?o事件，反之為暖池El Ni?o事件.他們還指出，兩類La Ni?a事件SSTA的分布型沒有兩類El Ni?o事件SSTA分布型的差異那么顯著，這是因?yàn)閭鹘y(tǒng)的La Ni?a事件本身就相對(duì)于El Ni?o事件位置更偏西.

曹璐等［17］將Ni?o3指數(shù)和Ni?o4指數(shù)進(jìn)行3個(gè)月滑動(dòng)平均處理后，作為指數(shù)組針對(duì)峰值類型和傳播類型兩方面來對(duì)ENSO事件進(jìn)行分類.峰值類型的判定標(biāo)準(zhǔn)為，當(dāng)ENSO事件達(dá)到峰值時(shí)，若標(biāo)準(zhǔn)化的Ni?o3指數(shù)大于標(biāo)準(zhǔn)化的Ni?o4指數(shù)，定義為東太平洋ENSO（Eastern Pacific-ENSO，EP-ENSO）事件，反之則定義為中太平洋ENSO（Central Pacific-ENSO，CP-ENSO）事件.傳播類型（即傳統(tǒng)意義下的ENSO類型）的判定標(biāo)準(zhǔn)為，若Ni?o3指數(shù)較Ni?o4指數(shù)先達(dá)到閾值（±0.5℃）則定義為EP-ENSO事件，反之定義為CP-ENSO事件.若兩指數(shù)同時(shí)達(dá)到閾值則以強(qiáng)度大小來作為判定標(biāo)準(zhǔn)，當(dāng)Ni?o3指數(shù)大于Ni?o4指數(shù)時(shí)，定義為EP-ENSO事件，反之則定義為CP-ENSO事件.

另外一些研究也采用Ni?o3指數(shù)和Ni?o4指數(shù)相對(duì)大小判定El Ni?o事件的類型［10，18-19］.同時(shí)Kug等［11，19］的研究表明，相對(duì)于兩類El Ni?o事件來說，兩類La Ni?a事件的區(qū)別不那么明顯；而Ren等［12］認(rèn)為，自氣候躍遷以后，當(dāng)去掉強(qiáng)烈的背景年代信號(hào)時(shí)，兩類La Ni?a事件也是能夠明顯區(qū)分開的.

2.2定量角度

唐佑民等［20］采用聚類分析方法，按海溫在El Ni?o事件過程中的演變特征，根據(jù)El Ni?o事件爆發(fā)時(shí)海水增溫首先出現(xiàn)的位置，將El Ni?o事件分為兩類，I類El Ni?o事件增暖最初出現(xiàn)在日界線附近，II類El Ni?o事件最初增暖出現(xiàn)在赤道東太平洋.將El Ni?o事件發(fā)展的不同階段分別進(jìn)行合成分析，他們指出，兩類El Ni?o事件海溫異常的傳播特征存在顯著區(qū)別.唐佑民等［20］的分類結(jié)果與林學(xué)椿等［16］結(jié)果類似，這是因?yàn)樵贓NSO事件中，海溫開始增（降）溫位置的不同，在較大程度上決定了海溫演變過程中的特征存在差異.

另外一些研究則開始通過定義指數(shù)組將其定量化，以期得到更為準(zhǔn)確的分類.例如：Ashok等［5］通過經(jīng)驗(yàn)正交分解（Empirical Orthogonal Function，EOF）方法分析發(fā)現(xiàn)El Ni?o Modoki的熱帶太平洋海溫異常分布呈緯向三極子結(jié)構(gòu)，據(jù)此特點(diǎn)他們定義了El Ni?o Modoki index（EMI指數(shù)）；Li等［21］在此基礎(chǔ)上考慮了不同關(guān)鍵區(qū)的貢獻(xiàn)不同進(jìn)一步定義了IEMI指數(shù)（improved El Ni?o Modoki index）；陳圣劫等［22］通過多變量經(jīng)驗(yàn)正交函數(shù)分解也發(fā)現(xiàn)了三極子的分布結(jié)構(gòu)，同時(shí)他們的研究發(fā)現(xiàn)El Ni?o和El Ni?o Modoki的海氣耦合特征存在顯著差異，故而選取上層熱含量定義了Heat Content El Ni?o Index（HCEI）和Heat Content El Ni?o Modoki Index（HCEMI）指數(shù)來分別反映和區(qū)分兩類El Ni?o事件；Kao等［9］和秦堅(jiān)肇等［23］（待刊）通過聯(lián)合回歸EOF方法定義東太平洋指數(shù)/中太平洋指數(shù)（Eastern Pacific Index/Central Pacific Index，EPI/CPI）；Xu等［24］通過奇異值分解（Singular Value Decomposition，SVD）方法定義東太平洋次表層指數(shù)/中太平洋次表層指數(shù)（Eastern Pacific Subsurface Index/Central Pacific Subsurface Index，EPSI/CPSI）；Ren等［25］對(duì)Ni?o3，Ni?o4指數(shù)進(jìn)行簡(jiǎn)單的非線性變換提出描述冷舌ENSO（Cold Tongue-ENSO，CT-ENSO）和暖池ENSO（warm Pool-ENSO，WP-ENSO）的NCT和NWP指數(shù)；另外，Yu等［13］選取赤道東太平洋和赤道中太平洋次表層海洋溫度定義次表層海溫指數(shù)組.

2.2.1Ni?o3.4 /Trans-Ni?o Index（TNI）

Trenberth等［4］認(rèn)為，要描述ENSO事件的發(fā)展演變過程以及ENSO事件之間的差異需要至少兩個(gè)自由度，他們指出，可以用Ni?o3.4指數(shù)和TNI來實(shí)現(xiàn)這一目的：Ni?o3.4 SST指數(shù)用來描述中東太平洋平均的SSTA，TNI用來描述ENSO事件期間中、東太平洋SSTA的梯度.TNI定義為標(biāo)準(zhǔn)化的Ni?o l＋2（10?S～0?，8?～90?W）和Ni?o4（5?S～5?N，160?E～150?W）SST指數(shù)之差.兩指數(shù)的超前滯后相關(guān)分析結(jié)果表明它們可以描述過去的100 a間ENSO的發(fā)展演化情況，包括1976/77年的氣候躍遷.Ashok等［5］年的研究認(rèn)為，赤道太平洋SSTA的第一、二EOF模態(tài)分別與Ni?o3.4指數(shù)和TNI分別密切相關(guān)，在所謂的El Ni?o Modoki事件和傳統(tǒng)El Ni?o事件發(fā)生時(shí)期，這兩個(gè)指數(shù)的演變特征是不同的，因此可以用這組指數(shù)描述兩類不同事件.但是TNI的不足之處在于并沒有考慮熱帶西太平洋在描述非傳統(tǒng)El Ni?o事件過程中的重要性.

2.2.2EMI

為了使用單一指數(shù)來表征中太平洋ENSO事件，Ashok［5］等困在考慮熱帶西太平洋SSTA的作用的前提下提出了EMI.對(duì)熱帶太平洋SSTA進(jìn)行EOF分析的結(jié)果表明，前兩個(gè)EOF模態(tài)可以分別代表傳統(tǒng)El Ni?o事件和El Ni?o Modoki事件.第二EOF模態(tài)空間分布型，即El Ni?o Modoki的分布型，表現(xiàn)為赤道中太平洋為暖異常，暖異常中心兩側(cè)的東、西太平洋沿赤道分布有冷異常，且暖異常和冷異常的振幅是相當(dāng)?shù)?；在較高緯度，赤道中太平洋的暖異常在兩半球分別向東擴(kuò)展.可見，在赤道太平洋地區(qū)存在三個(gè)涉及El Ni?o Modoki的關(guān)鍵區(qū).基于SSTA分布獨(dú)特的三極子結(jié)構(gòu)，他們定義了EMI：

公式1右邊的方括號(hào)分別表示SSTA在區(qū)域A（165?E～140?W，10?S～10?N），B（110?W～70?W，15?S～5?N），C（125?E～145?E，10?S～20?N）內(nèi)的平均.區(qū)域A，B，C分別為EOF第二模態(tài)空間分布型的3個(gè)關(guān)鍵區(qū)域，即暖異常區(qū)域和左右兩側(cè)的冷異常區(qū)域.將El Ni?o Modoki事件定義為指數(shù)振幅大于等于0.7倍季節(jié)標(biāo)準(zhǔn)偏差的事件.

相關(guān)性分析結(jié)果表明，EMI同EOF第二模的時(shí)間序列PC2（Principal Component，PC）有很高的相關(guān)性，說明EMI在很大程度上可以捕捉到赤道太平洋SSTA進(jìn)行EOF分解得到的第二個(gè)模態(tài)的分布型，即可以恰當(dāng)?shù)拿枋鯡l Ni?o Modoki事件.EMI同TNI之間的相關(guān)性也很高，兩者都可以用來表示El Ni?o Modoki.但是EMI更加有優(yōu)勢(shì)，主要表現(xiàn)在兩方面，一方面，EMI同PC2的相關(guān)性高于TNI同PC2的相關(guān)性，這使得EMI更有優(yōu)勢(shì)；另一方面，EMI考慮了赤道西太平洋對(duì)于El Ni?o Modoki起到的作用.

2.2.3IEMI

根據(jù)Ashok等［5］的方法，Li等［21］對(duì)EMI進(jìn)行改進(jìn)，提出了IEMI，IEMI表達(dá)方式如下：

公式2中的權(quán)重系數(shù)由線性回歸計(jì)算得到，Ta，A、Ta，B和Ta，C分別代表SSTA在區(qū)域A，B，C中的平均，3個(gè)區(qū)域的范圍同Ashok等［5］提到的區(qū)域范圍一致，分別是與El Ni?o Modoki相關(guān)的3個(gè)關(guān)鍵區(qū).當(dāng)標(biāo)準(zhǔn)化的指數(shù)連續(xù)5個(gè)月大于等于一個(gè)標(biāo)準(zhǔn)偏差時(shí)定義為一個(gè)El Ni?o Modoki事件.相對(duì)于EMI的0.7個(gè)標(biāo)準(zhǔn)偏差來說IEMI將確定El Ni?o Modoki的閡值提高為一個(gè)標(biāo)準(zhǔn)偏差，所以IEMI更能捕捉到El Ni?o Modoki事件，并且排除傳統(tǒng)El Ni?o信號(hào)的干擾.

由公式3和4可以看到，相較于EMI來說，IEMI的改進(jìn)之處在于考慮了El Ni?o Modoki時(shí)期赤道東、西太平洋區(qū)域的SSTA貢獻(xiàn)的差異，即在EMI的基礎(chǔ)上對(duì)各區(qū)域添加了不同權(quán)重.所以IEMI不僅考慮了熱帶西太平洋SSTA在捕捉ElNi?o Modoki中的作用，同時(shí)也考慮到等式右邊兩項(xiàng)（分別與熱帶東、西太平洋相關(guān)）對(duì)EOF第二模態(tài)SSTA方差貢獻(xiàn)率的不同.因此IEMI能明確地識(shí)別出2002/03，2004/05年的El Ni?o Modoki事件，而在嚴(yán)格意義上，EMI是無(wú)法將2002/03，2004/05年確定為El Ni?o Modoki事件的.相關(guān)分析的結(jié)果表明，相比于EMI來說IEMI增加了同PC2的相關(guān)性的同時(shí)也減小了同PC1的相關(guān)性，即IEMI同PC1更加正交，這有效的削弱了El Ni?o信號(hào)的干擾IEMI能更好的區(qū)分兩類El Ni?o事件.

2.2.4EPI/CPI

Kao等［9］認(rèn)為SSTA的第二EOF分布型中同時(shí)包含了Ni?ol＋2和Ni?o4的信息，故不能準(zhǔn)確的描述新型ENSO事件的主要特征，他們同樣基于EOF分析提出了新的指數(shù)來描述新型ENSO事件.

他們采用聯(lián)合回歸EOF方法來分離兩類ENSO事件，即在進(jìn)行EOF分析之前，首先從原始SSTA中減去原始SSTA和Ni?ol＋2指數(shù)的回歸值，對(duì)得到的差值SSTA進(jìn)行EOF分析得到的第一模態(tài)即代表CP-ENSO；同理，在進(jìn)行EOF分析之前，首先從原始SSTA中減去原始SSTA和Ni?o4指數(shù)的回歸值，對(duì)得到的差值SSTA進(jìn)行EOF分析可得到代表EP-ENSO的第一EOF模態(tài).將兩個(gè)EOF第一模態(tài)時(shí)間序列分別定義為CPI和EPI，當(dāng)CPI（EPI）超過一個(gè)標(biāo)準(zhǔn)偏差時(shí)定義為CP（EP）-ENSO.相關(guān)性分析結(jié)果表明，CPI同Ashok等［5］提出的EMI指數(shù)具有很高的相關(guān)性，它們都可以識(shí)別非傳統(tǒng)ENSO事件.CPI和EPI可以較好地描述兩類ENSO事件發(fā)展的演變過程，但是計(jì)算過程卻較為復(fù)雜繁瑣.

秦堅(jiān)肇等［23］基于Kao等［9］提出的聯(lián)合回歸EOF方法，定義了新的EPI（EP-ENSO Index）和CPI（CP-ENSO Index）.

公式5中SSTA［A1］和SSTA［B1］分別表示SSTA在區(qū)域A1（5?S～5?N，110?W～80?W）和區(qū)域B1（5?S～10?N，150?E～180?E）內(nèi)的平均，權(quán)重系數(shù)用于平衡各區(qū)域面積間的比重，權(quán)重系數(shù)EA=2/5，EB=3/5；等式6中SSTA［A2］、SSTA［B2］和SSTA［C］，分別表示SSTA在區(qū)域A2（10?S～10?N，170?E～140?W）、區(qū)域B2（10?S～5?N，130?E～150?E）和區(qū)域C（5?S～10?N，100?W～80?）內(nèi)的平均，權(quán)重系數(shù)CA=10/15，CB=3/15，CC=2/15.他們定義當(dāng)標(biāo)準(zhǔn)化的EPI0.7≧（≦－0.7）且持續(xù)4個(gè)月以上的事件定義為EP-EI Ni?o（La Ni?a）事件；當(dāng)標(biāo)準(zhǔn)化的CPI0.8≧（≦－0.8）且持續(xù)4個(gè)月以上的事件定義為CP-El Ni?o（La Ni?a）事件.EPI和CPI之間的相關(guān)性很小，可以更加清楚的區(qū)分兩類ENSO事件.同時(shí)指數(shù)組可以恰當(dāng)?shù)恼宫F(xiàn)兩類ENSO事件的不同周期，并且能夠指示兩類ENSO發(fā)展演變過程中的各個(gè)階段；兩個(gè)指數(shù)不僅可以很好的描述事件發(fā)生時(shí)熱帶太平洋SSTA的發(fā)展演變過程，準(zhǔn)確的捕捉到兩類ENSO事件，超前滯后相關(guān)分析的結(jié)果也表明，這組指數(shù)可以很好的反映氣候躍遷前后ENSO的變化.因此，用這個(gè)指數(shù)組對(duì)ENSO事件進(jìn)行分類有其合理性.另外，這一指數(shù)組僅涉及到區(qū)域平均值的線性計(jì)算，過程更加簡(jiǎn)單.

2.2.5次表層海溫指數(shù)

Yu等［13］利用1958—2001年海洋同化資料東太平洋（80?W～90?W，5?S～5?N）和中太平洋（160?E～150?W，5?S～5?N）100米以上區(qū)域內(nèi)的平均海溫異常得到東太平洋次表層海溫指數(shù)和中太平洋次表層海溫指數(shù).他們指出，上述次表層指數(shù)較傳統(tǒng)Ni?o指數(shù)具有更強(qiáng)的獨(dú)立性和更大的偏度，更適合于識(shí)別東太型和中太型ENSO特性.基于該指數(shù)識(shí)別的兩類ENSO事件，強(qiáng)El Ni?o事件主要表現(xiàn)出東太型特征，而強(qiáng)La Ni?a事件則更趨向于中太型特征；對(duì)于弱的El Ni?o事件和強(qiáng)La Ni?a事件，則表現(xiàn)出相反的特性.

2.2.6NCP/NWP

由于Ni?o3指數(shù)和Ni?o4指數(shù)之間的相關(guān)性很高，不能有效區(qū)分兩類事件，Ren等［25］提出將Ni?o3指數(shù)和Ni?o4指數(shù)通過變換系數(shù)α進(jìn)行一個(gè)簡(jiǎn)單的非線性變換構(gòu)造兩個(gè)新的Ni?o指數(shù)，即冷舌El Ni?o指數(shù)（NCT）和暖池El Ni?o指數(shù)（NWP），來對(duì)兩類事件進(jìn)行分類.這對(duì)指數(shù)可以方便的描述兩類ENSO事件的主要SSTA分布型、不同位相的傳播特征以及ENSO狀態(tài)的變化情況，兩個(gè)新的Ni?o指數(shù)定義為：

公式7和8中N3和N4分別代表Ni?o3指數(shù)和Ni?o4指數(shù)，新的指數(shù)組僅是Ni?o3指數(shù)與Ni?o4指數(shù)的簡(jiǎn)單非線性組合，但是受到ENSO位相的限制.當(dāng)NWP大于一個(gè)閾值，例如一個(gè)標(biāo)準(zhǔn)偏差時(shí)，視為暖池El Ni?o事件；當(dāng)NCT大于一個(gè)閾值，例如一個(gè)標(biāo)準(zhǔn)偏差時(shí)，視為冷舌El Ni?o事件.相比于Ni?o3指數(shù)和Ni?o4指數(shù)之間很高的相關(guān)性，N3和N4之間的相關(guān)很小，因此，新的指數(shù)能夠更好地區(qū)分兩類ENSO事件.對(duì)兩個(gè)指數(shù)進(jìn)行超前滯后分析，結(jié)果表明在赤道SSTA緯向傳播方面它們可以有效捕捉到氣候躍遷前后ENSO的變化.另外，氣候躍遷之后兩指數(shù)近乎是獨(dú)立的，這也說明了兩類ENSO事件之間的獨(dú)立性.

2.2.7EPSI/CPSI

Xu等［24］對(duì)熱帶太平洋SST和海洋次表層溫度（Subsurface Ocean Temperature，SOT）異常進(jìn)行奇異值分解，結(jié)果表明，SOT的第一、三模態(tài)分別同兩類ENSO事件密切相關(guān)，因此，他們將SOT的第一、三SVD模態(tài)時(shí)間系數(shù)分別定義為EPSI和CPSI.將這組指數(shù)同Kao等［11］和Ren等［25］提出的指數(shù)組進(jìn)行比較，相關(guān)性分析和小波分析的結(jié)果表明，EPSI和NCT具有很高的相關(guān)性，并且可以捕捉到EP-ENSO事件的年際變化，另外，CPSI和CP-ENSO事件之間也有一定的關(guān)系，可以用來表征CP-ENSO事件.

2.2.8Typical El Ni?o Index/Central El Ni?o Index（TENT/CENT）

Li等［26］將SSTA的第一、二EOF模的時(shí)間系數(shù)同去趨勢(shì)的冬季SSTA進(jìn)行回歸處理得到它們的SSTA分布型，定義回歸的第一、二EOF模態(tài)之差為傳統(tǒng)El Ni?o SST分布型，兩者之和為中太平洋El Ni?o SST分布型.相對(duì)于單純的由EOF前兩個(gè)模態(tài)定義兩類事件，新的SSTA分布型更接近于觀測(cè)事實(shí)，且它們之間較高的相關(guān)性也符合兩類事件并不正交這一事實(shí)［10］.將TENT和CENT分別定義為標(biāo)準(zhǔn)化了的去趨勢(shì)冬季SSTA向上述兩類新的分布型的投影系數(shù).當(dāng)TENT大于CENT和0.6℃，且熱帶東太平洋最大SSTA大于1.2℃時(shí)定義為一個(gè)傳統(tǒng)El Ni?o事件；當(dāng)CENT大于TENT和0.6℃，且熱帶中太平洋最大SSTA大于0.9℃時(shí)定義為一個(gè)中太平洋El Ni?o事件.雖然這組指數(shù)可以描述兩類事件的非正交特征以及周期特征，但是計(jì)算過程卻較復(fù)雜.

2.2.9HCEI/HCEMI

由于ENSO事件發(fā)生時(shí)期，海洋熱力異常信號(hào)不僅出現(xiàn)在海洋表面，同樣存在于海洋內(nèi)部，而且在海洋內(nèi)部的信號(hào)可能更明顯，所以陳圣劫等［22］選取了與海洋表層和次表層海溫有關(guān)的上層海洋熱含量（Heat Content，HC）作為熱力特征量來構(gòu)建區(qū)分El Ni?o事件類型的指數(shù).他們首先對(duì)SST, HC, SLP，850 hPa緯向風(fēng)、850 hPa經(jīng)向風(fēng)、200 hPa位勢(shì)高度和OLR共7個(gè)要素場(chǎng)進(jìn)行多變量經(jīng)驗(yàn)正交函數(shù)分解（Multivariate Empirical Orthogonal Functions MV-EOFs），得到的第一、二模態(tài)可以分別代表傳統(tǒng)El Ni?o事件和中太平洋El Ni?o事件，根據(jù)兩個(gè)模態(tài)的空間分布型來確定對(duì)兩類事件起關(guān)鍵作用的區(qū)域，得到的兩個(gè)指數(shù)計(jì)算公式如下：

公式9和10中IHCE、IHCEM分別表示ICEH和IHCEM，分別用于判定傳統(tǒng)El Ni?o事件和中太平洋El Ni?o事件.下標(biāo)HCA表示熱含量距平，下標(biāo)AE、BE、AEM、BEM、CEM分別代表計(jì)算區(qū)域，其中，AE（10?S～10?N，120?W～80?W）和AEM（15?S～5?N，170?E～14?W）為MV-EOFs得到的前兩個(gè)模態(tài)空間分布型中的正異常值主要分布區(qū)域，而BE（10?S～10?N，120?E～160?E）、BEM（0?～10?N，120?E～140?E）和CEM（20?S～5?S，115?W～80?W）則為負(fù)異常值主要分布區(qū)域.同Kao等［9］、Yu等［13］以及Ren等［25］提出的指數(shù)組相比，IHCE和IHCEM之間的相關(guān)系數(shù)更小，說明由這兩個(gè)指數(shù)分別確定的兩類事件具有更高的獨(dú)立性.另外，這組指數(shù)不僅可以對(duì)El Ni?o事件進(jìn)行分類，同時(shí)它們與兩類事件發(fā)生時(shí)期的海氣耦合過程是緊密聯(lián)系的，可以更好的表征事件發(fā)生時(shí)的海氣耦合特征.這對(duì)指數(shù)對(duì)幾個(gè)有爭(zhēng)議的El Ni?o事件也可以做出更明確的區(qū)分.

2.2.10E/C

Takahashi等［27］采用HadlSST數(shù)據(jù)集對(duì)月平均的SSTA計(jì)算了EOF模，他們指出EOF的前兩個(gè)模態(tài)無(wú)法描述兩類不同的ENSO現(xiàn)象，而是描述了ENSO的非線性演化.基于主EOF模態(tài)，他們定義了兩個(gè)新的正交指數(shù)E和C，這兩個(gè)指數(shù)分別同東赤道太平洋的極端暖事件以及中赤道太平洋的冷事件和包括El Ni?o Modoki及CP-El Ni?o在內(nèi)的中等暖事件相關(guān)，可寫為如下形式：

公式11和12中PC1和PC2分別為第一和第二EOF模的時(shí)間系數(shù)，由于指數(shù)C和E分別同中太平洋SST指數(shù)（Ni?o4）以及東太平洋SST指數(shù)（Ni?o1＋2）有很好的相關(guān)性，因此這組指數(shù)可以近似寫為如下形式：

公式13和14中，Ni?o1+2和Ni?o4分別表示Ni?o1＋2區(qū)域以及Ni?o 4區(qū)域SSTA的區(qū)域平均值.以C和E為坐標(biāo)軸構(gòu)建坐標(biāo)系時(shí)，極端事件沿E軸分布，而中等事件一般沿C軸分布.

3兩類ENSO事件與氣候躍遷

20世紀(jì)70年代后期，伴隨著氣候躍遷ENSO事件也發(fā)生了顯著的變化.氣候躍遷以前以準(zhǔn)4a模為主導(dǎo)，主要是周期為3～4a的冷舌ENSO事件，而暖池ENSO事件是否存在尚有爭(zhēng)議；氣候躍遷以后，主導(dǎo)模態(tài)為準(zhǔn)兩年模與準(zhǔn)四年模共存，暖池ENSO事件出現(xiàn)愈加頻繁，冷舌ENSO事件則具有更大的強(qiáng)度，ENSO冷暖事件都可以被清晰的區(qū)分為兩類事件.因此，當(dāng)除去掩蓋暖池ENSO特征的年代變化時(shí)，兩類ENSO事件可以體現(xiàn)ENSO特征的變化.

對(duì)氣候躍遷以后的海表面溫度場(chǎng)進(jìn)行了經(jīng)驗(yàn)正交分解［5，8］，得到的第一EOF?？臻g分布型表現(xiàn)為異常中心位于赤道東太平洋，并且向赤道中太平洋擴(kuò)展；而第二EOF空間分布型則表現(xiàn)為在熱帶中太平洋為暖SSTA，其兩側(cè)的熱帶東、西太平洋為冷SSTA.由于前兩個(gè)EOF模所解釋的方差可以很好的分離［28］，并且得到了合成分析以及復(fù)雜經(jīng)驗(yàn)正交分解（Complex EOF，CEOF）分析研究結(jié)果的支持，因此這兩種空間分布可以代表氣候變化的不同模.前兩個(gè)EOF模分別對(duì)應(yīng)于溫度異常中心位于赤道東太平洋的典型El Ni?o事件以及異常中心位于赤道中太平洋的El Ni?o Modoki事件.第一EOF模的時(shí)間系數(shù)同Ni?o3指數(shù)的相關(guān)性很高，即第一EOF模可以很好地表征典型El Ni?o事件，而第二EOF模的時(shí)間系數(shù)同Ni?o 3指數(shù)的相關(guān)性很低，即這一EOF模與典型El Ni?o事件無(wú)關(guān).

4總結(jié)

典型El Ni?o事件的正海溫異常主要出現(xiàn)在赤道東太平洋，在赤道西太平洋為負(fù)的海溫異常；El Ni?o Modoki事件的正海溫異常中心則位于赤道中太平洋.兩類ENSO事件海表溫度異常中心位置的不同會(huì)引起不同的環(huán)流異常以及氣候效應(yīng)，因此，在研究EP/CP-ENSO時(shí)對(duì)事件進(jìn)行正確的分類是必要的.

早期的研究主要從定型的角度進(jìn)行分類；在定量研究方面，許多學(xué)者根據(jù)所關(guān)注重點(diǎn)的不同選取了不同指數(shù)組對(duì)兩類事件進(jìn)行分類，一些直接采用Ni?o指數(shù)或者間接用Ni?o指數(shù)的組合或選取非對(duì)稱更顯著區(qū)域的海溫指數(shù)來劃分兩類事件，另一些則通過EOF、聯(lián)合回歸EOF、多元變量EOF、SVD等方法得到能夠描述兩類事件的模態(tài)，進(jìn)而定義能夠區(qū)分兩類事件的指數(shù)組.而從物理意義上來講，基于EOF得來的指數(shù)會(huì)受到數(shù)學(xué)正交性的約束，因此并非區(qū)分兩類事件的理想指數(shù).另外，這些對(duì)兩類事件的區(qū)分能力是有差異的，計(jì)算過程的繁簡(jiǎn)程度也不同，在實(shí)際應(yīng)用的過程中需要根據(jù)自己的需要選取不同的指數(shù)組進(jìn)行研究.相對(duì)于單一指數(shù)來說，指數(shù)組雖然可以更好地區(qū)分兩類事件，但是要將其應(yīng)用于對(duì)ENSO事件進(jìn)行檢測(cè)的實(shí)際業(yè)務(wù)工作中就顯得過于繁瑣了，能否找到可以很好區(qū)分兩類事件的單一指數(shù)以及找到將指數(shù)組方便的應(yīng)用于實(shí)際業(yè)務(wù)預(yù)測(cè)的方法，有待進(jìn)一步研究.

·高被引論文摘要·

被引頻次：225

近百年來的ENSO事件及其強(qiáng)度

王紹武，龔道溢

利用Ni?o3區(qū)、Ni?o C區(qū)海表溫度序列及兩個(gè)SOI序列，同時(shí)考慮SST和SOI建立了1867—1998季分辨率的ENSO指數(shù)序列.根據(jù)ENSO指數(shù)序列，并參考Wright的SOI指數(shù)及其它材料，確認(rèn)了1867—1998年ENSO事件，共確定出32次暖事件（正SST負(fù)SOI）及32次冷事件（負(fù)SST正SOI）對(duì)每次事件的強(qiáng)度分強(qiáng)、中、弱三等進(jìn)行了評(píng)估.雖然1982/1983年暖事件的峰值最高，但從整個(gè)事件的平均強(qiáng)度來看，1997/1998年的暖事件則是130年來最強(qiáng)的一次.近20年是暖事件的多發(fā)期.

ENSO；強(qiáng)度；季分辨率

來源出版物：氣象，1999，25（1）： 9-13

被引頻次：164

厄爾尼諾的發(fā)生與赤道西太平洋暖池次表層海溫異常

李崇銀，穆明權(quán)

摘要：摘要通過資料分析研究了厄爾尼諾事件的爆發(fā)與西太平洋暖池次表層海溫正異常的重要關(guān)系.結(jié)果表明，El Ni?o事件之前暖池次表層海溫都有明顯的持續(xù)升高；這種暖池次表層海溫正距平的出現(xiàn)，尤其是它向赤道中東太平洋的傳播對(duì)El Ni?o事件的爆發(fā)有直接關(guān)系，是導(dǎo)致El Ni?o事件的重要原因.分析還表明，暖池次表層海溫正距平的東移原因在于赤道西太平洋地區(qū)西風(fēng)異常的發(fā)生和向東擴(kuò)展.

關(guān)鍵詞：厄爾尼諾（El Ni?o）；暖池海溫異常

來源出版物：大氣科學(xué)，1999，23（5）： 513-521

被引頻次：106

厄爾尼諾與我國(guó)汛期降水

林學(xué)椿，于淑秋

摘要：本文詳細(xì)地討論了厄爾尼諾與我國(guó)汛期大尺度降水的關(guān)系.指出，厄爾尼諾東部型，北太平洋海溫的三個(gè)主要正負(fù)距平區(qū)的結(jié)構(gòu)具有PNA遙相關(guān)型；厄爾尼諾中部型，北太平洋海溫的三個(gè)主要正負(fù)距平區(qū)分布在赤道東太平洋到千島群島一線上.進(jìn)而指出，厄爾尼諾東部型峰期過后，我國(guó)汛期降水的大尺度特征是長(zhǎng)江流域降水偏少，江南和華北地區(qū)降水偏多.在厄爾尼諾中部型峰期過后則相反，長(zhǎng)江流域降水偏多，江南和華北降水偏少.

關(guān)鍵詞：厄爾尼諾；北太平洋海溫；汛期降水

來源出版物：氣象學(xué)報(bào)，1998，51（4）： 434-441

被引頻次：97

厄爾尼諾現(xiàn)象對(duì)北半球大氣環(huán)流和中國(guó)降水的影響

趙振國(guó)

摘要：本文主要討論了厄爾尼諾現(xiàn)象對(duì)北半球大氣環(huán)流和中國(guó)季風(fēng)降水的影響.研究表明，在厄爾尼諾開始年的春夏季，對(duì)流層上部位勢(shì)高度和副熱帶高壓都處在由弱到強(qiáng)的轉(zhuǎn)變狀態(tài)，我國(guó)東部地區(qū)大范圍少雨；秋季發(fā)生明顯的趨勢(shì)轉(zhuǎn)折，秋季到次年夏季，對(duì)流層上部位勢(shì)高度升高，副高增強(qiáng)西伸，除次年2、3月份全國(guó)大范圍少雨外，其余月份大都為南多北少的分布型，這種分布形態(tài)在開始年秋季最典型.厄爾尼諾開始年、次年，長(zhǎng)江中下游入梅期偏晚.

關(guān)鍵詞：厄爾尼諾；大氣環(huán)流；中國(guó)；降水；入梅

來源出版物：大氣科學(xué)，1996，20（4）： 422-428

被引頻次：93

厄爾尼諾和反厄爾尼諾事件與西北太平洋臺(tái)風(fēng)活動(dòng)

何敏，宋文玲，陳興芳

摘要：用統(tǒng)計(jì)相關(guān)和典型年合成方法分析了厄爾尼諾和反厄爾尼諾事件與西北太平洋臺(tái)風(fēng)活動(dòng)的關(guān)系，指出厄爾尼諾年臺(tái)風(fēng)活動(dòng)減少，反厄爾尼諾年臺(tái)風(fēng)活動(dòng)增加，而且臺(tái)風(fēng)活動(dòng)與厄爾尼諾、反厄爾尼諾事件起始和終止時(shí)間、強(qiáng)度、臺(tái)風(fēng)生成區(qū)域有關(guān).利用厄爾尼諾和反厄爾尼諾年臺(tái)風(fēng)活動(dòng)頻數(shù)的統(tǒng)計(jì)特征，及臺(tái)風(fēng)頻數(shù)與海溫等要素的時(shí)滯相關(guān)關(guān)系，為臺(tái)風(fēng)頻數(shù)的預(yù)測(cè)提供了有益的信息.還應(yīng)用奇異值分解方法，分析了高度場(chǎng)和海溫場(chǎng)的相關(guān)關(guān)系.結(jié)果表明，厄爾尼諾年海氣耦合作用將造成不利于臺(tái)風(fēng)發(fā)展的環(huán)流條件，因此臺(tái)風(fēng)偏少，反厄爾尼諾年則出現(xiàn)相反的情況.

關(guān)鍵詞：臺(tái)風(fēng)；厄爾尼諾和反厄爾尼諾；奇異值分解

來源出版物：熱帶氣象學(xué)報(bào)，1999，15（1）： 17-25

被引頻次：84

1998年大氣環(huán)流異常及其對(duì)中國(guó)氣候異常的影響

李維京

摘要：1998年受ENSO事件和青藏高原冬春季積雪多等因素的影響，北半球大氣環(huán)流的主要特征是：500 hPa西太平洋副高強(qiáng)大，夏季副高脊線位置偏南；冬夏季風(fēng)均較弱；赤道輻合帶異常偏弱，在西太平洋生成和登陸影響我國(guó)的臺(tái)風(fēng)和熱帶風(fēng)暴異常偏少；夏季亞洲中高緯度經(jīng)向環(huán)流發(fā)展，其它季節(jié)則以緯向環(huán)流為主；這些環(huán)流異常是影響1998年中國(guó)氣候極其異常的主要原因.

關(guān)鍵詞：厄爾尼諾；環(huán)流異常；氣候異常

來源出版物：氣象，1999，25（4）： 20-25

被引頻次：69

我國(guó)暖冬氣候及其成因分析

孫林海，趙振國(guó)

摘要：重點(diǎn)分析了20世紀(jì)80年代以來，我國(guó)冬季持續(xù)偏暖、出現(xiàn)連續(xù)暖冬的成因.初步分析表明，我國(guó)氣溫存在著大約30年左右的年代際變化趨勢(shì)，厄爾尼諾事件的發(fā)生、東亞冬季風(fēng)減弱、西太平洋副熱帶高壓增強(qiáng)、歐亞大陸積雪面積減小、火山活動(dòng)減少以及溫室效應(yīng)等，都可能是造成我國(guó)冬季持續(xù)偏暖的主要因素.

關(guān)鍵詞：暖冬氣候；成因分析；ENSO；西太平洋副高；東亞冬季風(fēng)

來源出版物：氣象，2004，30（12）： 57-60

被引頻次：64

印度洋海溫偶極子和太平洋海溫異常

李崇銀，穆明權(quán)，潘靜

摘要：用近百年觀測(cè)資料分析了赤道印度洋海溫（SST）變化，其偶極子型振蕩的特征確實(shí)存在.這種偶極子型振蕩在9～11月最強(qiáng)，而在1～4月最弱；還表現(xiàn)出有年際變化和年代際變化.這個(gè)偶極子的正位相型（海溫西高東低）一般強(qiáng)于其負(fù)位相型（海溫東高西低）.盡管在極個(gè)別年赤道印度洋海溫偶極子似乎獨(dú)立于太平洋厄爾尼諾－南方濤動(dòng)（ENSO），但總體而論，赤道印度洋海溫偶極子與赤道太平洋海溫偶極子（類似反ENSO模）有很好負(fù)相關(guān).聯(lián)系它們的主要物理過程主要是赤道大氣緯向（Walker）環(huán)流的異常.

關(guān)鍵詞：印度洋海溫偶極子；太平洋海溫異常；反ENSO模

來源出版物：科學(xué)通報(bào)，2001，46（20）： 1747-1750

被引頻次：64

赤道東太平洋海溫與我國(guó)江淮流域夏季旱澇的成因分析

勵(lì)申申，壽紹文

摘要：對(duì)赤道東太平洋和西太平洋暖池海溫與江淮流域夏季降水的關(guān)系作功率譜分析和相關(guān)分析.指出秋冬季增暖的厄爾尼諾事件對(duì)應(yīng)江淮流域夏季降水偏多，春夏季開始發(fā)展的ENSO事件江淮流域夏季降水偏少.對(duì)兩種在不同季節(jié)增暖的ENSO事件對(duì)應(yīng)的異常流場(chǎng)特征及其對(duì)江淮流域降水的影響用1991年和1994年實(shí)例作對(duì)比分析.不同季節(jié)增暖的ENSO事件在太平洋熱帶地區(qū)環(huán)流調(diào)整的不同階段可能是影響夏季風(fēng)活動(dòng)和東亞夏季天氣氣候異常的主要原因.

關(guān)鍵詞：厄爾尼諾；西太平洋暖池；江淮流域；夏季降水；環(huán)流調(diào)整

來源出版物：應(yīng)用氣象學(xué)報(bào)，2000，11（3）： 331-338

被引頻次：60

1845—1988年期間厄爾尼諾事件與我國(guó)西北旱澇

朱炳瑗，李棟梁

摘要：本文應(yīng)用1958—1988年陜、甘、寧、青四省（區(qū)）3～9月的降水量資料，分析了厄爾尼諾事件當(dāng)年與次年西北降水量的差異性，結(jié)果表明在厄爾尼諾事件當(dāng)年，青海省東部、甘肅有中東部、寧夏全區(qū)和陜北降水量明顯偏少，而在厄爾尼諾事件次年明顯偏多，上述地方降水量差異是顯著的.根據(jù)Quinn等人劃分的歷史厄爾尼諾事件資料及西北各省近500年氣候歷史資料，我們分析了1845—1957年厄爾尼諾事件與西北旱澇的關(guān)系，從這些定性或半定量的資料分析中可以看出，上述結(jié)論在歷史上也是成立的.特別是西北歷史上的幾個(gè)大旱年，基本上出現(xiàn)在連續(xù)發(fā)生厄爾尼諾事件的年份中.

關(guān)鍵詞：厄爾尼諾事件；旱澇；氣候變化

來源出版物：大氣科學(xué)，1992，16（2）： 185-192

被引頻次：702

Pacific-East Asian teleconnection： how does ENSO affect East Asian climate？

Wang，B； Wu，RG； Fu，XH

Abstract： Observational evidence is presented to show a teleconnection between the central Pacific and East Asia during the extreme phases of ENSO cycles. This Pacific-East Asian teleconnection is confined to the lower troposphere. The key system that bridges the warm（cold）events in the eastern Pacific and the weak（strong）East Asian winter monsoons is an anomalous lower-tropospheric anticyclone（cyclone）located in the western North Pacific. The western North Pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures. The anomalies persist until the following spring or early summer，causing anomalously wet（dry）conditions along the East Asian polar front stretching from southern China northeastward to the east of Japan（Kuroshio extension）. Using atmospheric general circulation and intermediate models，the authors show that the anomalous Philippine Sea anticyclone results from a Rossby-wave response to suppressed convective heating，which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central Pacific warming. The development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling. Both the anticyclone and the cooling region propagate slowly eastward. The development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades. The rapid establishment of the Philippine Sea wind and SST anomalies implies the occurrence of extratropical-tropical interactions through cold surge-induced exchanges of surface buoyancy flux. The central Pacific warming plays an essential role in the development of the western Pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone-SST interaction and midlatitude-tropical interaction in the western North Pacific.

Keywords： Ni?o southern oscillation； sea-surface temperature； El-Ni?o； summer monsoon； biennial oscillation； toga coare； precipitation；atmosphere； winter； model

來源出版物：Journal of Climate，2000，13（9）： 1517-1536

被引頻次：667

Increased El Ni?o frequency in a climate model forced by future greenhouse warming

Timmermann，A； Oberhuber，J； Bacher，A； et al.

Abstract： The El Ni?o/Southern Oscillation（ENSO）phenomenon is the strongest natural interannual climate fluctuation（1）. ENSO originates in the tropical Pacific Ocean and has large effects on the ecology of the region，but it also influences the entire global climate system and affects the societies and economies of many countries（2）. ENSO can be understood as an irregular low-frequency oscillation between a warm（El Ni?o）and a cold（La Ni?a）state，The strong EI Ni?os of 1982/1983 and 1997/1998，along with the more frequent occurrences of El Ni?os during the past few decades，raise the question of whether human-induced ‘greenhouse’ warming affects，or willaffect，ENSO3，Several global climate models have been applied to transient greenhouse-gas-induced warming simulations to address this question（4-6）but the results have been debated owing to the inability of the models to fully simulate ENSO（because of their coarse equatorial resolution）（7），Here we present results from a global climate model with sufficient resolution in the tropics to adequately represent the narrow equatorial upwelling and low-frequency waves. When the model is forced by a realistic future scenario of increasing greenhouse-gas concentrations，more frequent El Ni?o-like conditions and stronger cold events in the tropical Pacific Ocean result.

Keywords： interannual variability； ENSO； event； chaos； cycle

來源出版物：Nature，1999，398（6729）： 694-697

被引頻次：567

El Ni?o Modoki and its possible teleconnection

Ashok，Karumuri； Behera，Swadhin K； Rao，Suryachandra A； et al.

Abstract： Using observed data sets mainly for the period 1979-2005，we find that anomalous warming events different from conventional El Ni?o events occur in the central equatorial Pacific. This unique warming in the central equatorial Pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly（SSTA）on both sides along the equator. empirical orthogonal function（EOF）analysis of monthly tropical Pacific SSTA shows that these events are represented by the second mode that explains 12% of the variance. Since a majority of such events are not part of El Ni?o evolution，the phenomenon is named as El Ni?o Modoki（pseudo-El Ni?o）（“Modoki” is a classical Japanese word，which means “a similar but different thing”）. The El Ni?o Modoki involves ocean-atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution，analogous to the Southern Oscillation in the case of El Ni?o. Hence the total entity is named as El Ni?o-Southern Oscillation（ENSO）Modoki. The ENSO Modoki events significantly influence the temperature and precipitation over many parts of the globe. Depending on the season，the impacts over regions such as the Far East including Japan，New Zealand，western coast of United States，etc.，are opposite to those of the conventional ENSO. The difference maps between the two periods of 1979-2004 and 1958-1978 for various oceanic/atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline. This appears to be a cause of more frequent and persistent occurrence of the ENSO Modoki event during recent decades.

Keywords： indian-ocean dipole； sea-surface temperature； pacific decadal variability； tropical pacific； southern-oscillation； equatorial pacific； air-temperature； climate variability； western pacific； global climate

來源出版物：Journal of Geophysical Research-Oceans，2009，112（C11）： C11007聯(lián)系郵箱：Ashok，Karumuri； ashok@apcc21.net

被引頻次：536

Variability of El Ni?o/Southern Oscillation activity at millennial timescales during the Holocene epoch

Moy，CM； Seltzer，GO； Rodbell，DT； et al.

Abstract： The variability of El Ni?o/Southern Oscillation（ENSO）during the Holocene epoch，in particular on millennial timescales，is poorly understood. Palaeoclimate studies have documented ENSO variability for selected intervals in the Holocene，but most records are either too short or insufficiently resolved to investigate variability on millennial scales（1-3）. Here we present a record of sedimentation in Laguna Pallcacocha，southern Ecuador，which is strongly influenced by ENSO variability，and covers the past 12000 years continuously. We find that changes on a timescale of 2-8 years，which we attribute to warm ENSO events，become more frequent over the Holocene until about 1200 years ago，and then decline towards the present. Periods of relatively high and low ENSO activity，alternating at a timescale of about 2000 years，are superimposed on this long-term trend. We attribute the long-term trend to orbitally induced changes in insolation，and suggest internal ENSO dynamics as a possible cause of the millennial variability. However，the millennial oscillation will need to be confirmed in other ENSO proxy records.

Keywords： southern-oscillation； tropical pacific； Ni?o； ecuador； PERU

來源出版物：Nature，2002，420（6912）： 162-165

被引頻次：529

The 1990-1995 El Ni?o Southern Oscillation event： Longest on record

Trenberth，KE； Hoar，TJ

Abstract： 參見本期“經(jīng)典文獻(xiàn)推薦”欄目.

被引頻次：520

Remote sea surface temperature variations during ENSO： Evidence for a tropical atmospheric bridge

Klein，SA； Soden，BJ； Lau，NC

Abstract： In an El Ni?o event，positive SST anomalies usually appear in remote ocean basins such as the South China Sea，the Indian Ocean，and the tropical North Atlantic approximately 3 to 6 months after SST anomalies peak in the tropical Pacific. Ship data from 1952 to 1992 and satellite data from the 1980s both demonstrate that changes in atmospheric circulation accompanying El Ni?o induce changes in cloud cover and evaporation which，in turn，increase the net heat flux entering these remote oceans. It is postulated that this increased heat flux is responsible for the surface warming of these oceans. Specifically，over the eastern Indian Ocean and South China Sea，enhanced subsidence during El Ni?o reduces cloud cover and increases the solar radiation absorbed by the ocean，thereby leading to enhanced SSTs. In the tropical North Atlantic，a weakening of the trade winds during El Ni?o reduces surface evaporation and increases SSTs. These relationships fit the concept of an “atmospheric bridge” that connects SST anomalies in the central equatorial Pacific to those in remote tropical oceans.

Keywords： Asian summer monsoon； southern-oscillation； interannual variability； seasonal-variation； SST anomalies； wind stress； ocean；pacific； circulation； scale

來源出版物：Journal of Climate，1999，12（4）： 917-932

被引頻次：478

On the weakening relationship between the Indian monsoon and ENSO

Kumar，KK； Rajagopalan，B； Cane，MA

Abstract： Analysis of the 140-year historical record suggests that the inverse relationship between the El Ni?o-Southern Oscillation（ENSO）and the Indian summer monsoon（weak monsoon arising from warm ENSO event）has broken down in recent decades. Two possible reasons emerge from the analyses. A southeastward shift in the Walker circulation anomalies associated with ENSO events may Lead to a reduced subsidence over the Indian region，thus favoring normal monsoon conditions. Additionally，increased surface temperatures over Eurasia in winter and spring，which area pail of the midlatitude continental warming trend，may favor the enhanced land-ocean thermal gradient conducive to a strong monsoon. These observations raise the possibility that the Eurasian warming in recent decades helps to sustain the monsoon rainfall at a normal Level despite strong ENSO events.

Keywords： Asian summer monsoon； eurasian snow cover； Ni?o southern oscillation； sea-surface temperatures； air-temperature； rainfall series； variability； climate； model； simulations

來源出版物：Science，1999，284（5423）： 2156-2159

被引頻次：442

Tropical Atlantic sea surface temperature variability and its relation to El Ni?o Southern Oscillation

Enfield，DB； Mayer，DA

Abstract： Past analyses of tropical Atlantic sea surface temperature variability have suggested a dipole behavior between the northern and southern tropics，across the Intertropical Convergence Zone（ITCZ）. By analyzing an improved 43-year（1950-1992）record of SST ［Smith er al.，1996］ and other data derived from the Comprehensive Ocean-Atmosphere Data Set（GOADS），it is shown that the regions north and south of the ITCZ are statistically independent of each other at the seasonal to interannual timescales dominating the data，confirming the conclusions of Houghton and Tourre ［1992］. Some dipole behavior does develop weakly during the boreal spring season，when there is a tendency for SST anomaly west of Angola to be opposite of that in the tropical North Atlantic. It is further shown that tropical Atlantic SST variability is correlated with Pacific El Ni?o-Southern Oscillation（ENSO）variability in several regions. The major region affected is the North Atlantic area of NE trades west of 40 degrees W along 10 degrees N-20 degrees N and extending into the Caribbean. There，about 50-80% of the anomalous SST variability is associated with the Pacific ENSO，with Atlantic warmings occurring 4-5 months after the mature phases of Pacific warm events. An analysis of local surface flux fields derived from GOADS data shows that the ENSO-related Atlantic warmings occur as a result of reductions in the surface NE trade wind speeds，which in turn reduce latent and sensible heat losses over the region in question，as well as cooling due to entrainment. This ENSO connection is best developed during the boreal spring following the most frequent season of maximum ENSO anomalies in the Pacific. A region of secondary covariability with ENSO occurs along the northern edge of the mean ITCZ position and appears to be associated with northward migrations of the ITCZ when the North Atlantic warmings occur. Although easterly winds are intensified in the western equatorial Atlantic in response to Pacific warm events，they do not produce strong local changes in SST. Contrary to expectations from studies based on equatorial dynamics，these teleconnected windanomalies do not give rise to significant correlations of SST in the Gulf of Guinea with the Pacific ENSO. As the teleconnection sequence matures，strong SE trades at low southern latitudes follow the development of the North Atlantic SST anomaly and precede by several months the appearance of weak negative SST anomalies off Angola and stronger positive anomalies extending eastward from southern Brazil along 15 degrees-30 degrees S.

Keywords： Northeast Brazil； ocean； circulation； anomalies； prediction； latitudes； rainfall； droughts； model

來源出版物：Journal of Geophysical Research-Oceans，1997，102（C1）： 929-945

被引頻次：406

El Ni?o，La Ni?a，and the nonlinearity of their teleconnections

Hoerling，MP； Kumar，A； Zhong，M

Abstract： 參見本期“經(jīng)典文獻(xiàn)推薦”欄目.

被引頻次：376

El Ni?o in a changing climate

Yeh，Sang-Wook； Kug，Jong-Seong； Dewitte，Boris； et al.

Abstract： El Ni?o events，characterized by anomalous warming in the eastern equatorial Pacific Ocean，have global climatic teleconnections and are the most dominant feature of cyclic climate variability on subdecadal timescales. Understanding changes in the frequency or characteristics of El Ni?o events in a changing climate is therefore of broad scientific and socioeconomic interest. Recent studies（1-5）show that the canonical El Ni?o has become less frequent and that a different kind of El Ni?o has become more common during the late twentieth century，in which warm sea surface temperatures（SSTs）in the central Pacific are flanked on the east and west by cooler SSTs. This type of El Ni?o，termed the central Pacific El Ni?o（CP-El Ni?o； also termed the dateline El Ni?o（2），El Ni?o Modoki（3）or warm pool El Ni?o（5）），differs from the canonical eastern Pacific El Ni?o（EP-El Ni?o）in both the location of maximum SST anomalies and tropical-midlatitude teleconnections. Here we show changes in the ratio of CP-El Ni?o to EP-El Ni?o under projected global warming scenarios from the Coupled Model Intercomparison Project phase 3 multi-model data set（6）. Using calculations based on historical El Ni?o indices，we find that projections of anthropogenic climate change are associated with an increased frequency of the CP-El Ni?o compared to the EP-El Ni?o. When restricted to the six climate models with the best representation of the twentieth-century ratio of CP-El Ni?o to EP-El Ni?o，the occurrence ratio of CP-El Ni?o/EP-El Ni?o is projected to increase as much as five times under global warming. The change is related to a flattening of the thermocline in the equatorial Pacific.

Keywords： sea-surface temperature； southern oscillation； pacific RIM； ENSO； sensitivity； anomalies； evolution； events； modoki； oceans

來源出版物：Nature，2009，461（4263）： 511-514聯(lián)系郵箱：Yeh，Sang-Wook； swyeh@kordi.re.kr

·推薦論文摘要·

ENSO和北極濤動(dòng)對(duì)東亞冬季氣候異常的綜合影響

陳文，蘭曉青，王林，等

摘要：利用NCEP/DOE再分析資料以及我國(guó)溫度和降水臺(tái)站資料，以厄爾尼諾和南方濤動(dòng)（El Ni?o and Southern Oscillation，ENSO）冷、暖位相的冬季作為背景，結(jié)合北極濤動(dòng)（Arctic Oscillation，AO）的月際異常，對(duì)兩者影響東亞冬季氣候異常的綜合作用進(jìn)行了研究.結(jié)果表明，當(dāng)El Ni?o和AO負(fù)異?；蛘週a Ni?a和AO正異常相互配置時(shí)，我國(guó)北方氣候異常主要受AO影響，南方氣候異常主要受ENSO影響，并且該氣候異常與已經(jīng)認(rèn)識(shí)到的AO和ENSO影響東亞氣候異常的機(jī)理相一致.然而，當(dāng)El Ni?o和AO正異?；蛘週a Ni?a和AO負(fù)異常相互配置時(shí)，盡管我國(guó)北方氣溫仍主要受AO影響，但我國(guó)大部分地區(qū)，特別是南方的氣候異常呈現(xiàn)出與已有認(rèn)識(shí)很不一樣的變化模態(tài).進(jìn)一步的分析認(rèn)為出現(xiàn)這種差異的原因可能在于平流層和對(duì)流層相互作用以及東亞地區(qū)中低緯相互作用的不同，這會(huì)導(dǎo)致在前者的冬季，大氣環(huán)流主要表現(xiàn)為緯向?qū)ΨQ性，中低緯相互作用偏弱，ENSO和AO對(duì)東亞的影響表現(xiàn)出線性的作用；而在后者的冬季，則不利于大氣環(huán)形模態(tài)的維持，導(dǎo)致東亞地區(qū)中低緯相互作用偏強(qiáng)，ENSO和AO對(duì)東亞的影響呈現(xiàn)出非線性的相互疊加.

關(guān)鍵詞：厄爾尼諾和南方濤動(dòng)；北極濤動(dòng)；東亞冬季氣候；氣溫與降水異常；平流層與對(duì)流層；相互作用

來源出版物：科學(xué)通報(bào)，2013，58（8）： 634-641聯(lián)系郵箱：陳文，cw@post.iap.ac.cn

厄爾尼諾衰亡年間南亞夏季風(fēng)在印度洋對(duì)西北太平洋遙強(qiáng)迫中的作用

胡海波，洪曉媛，張媛，等

摘要：已有的大量研究給出了印度洋增暖的氣候效應(yīng)，特別是對(duì)于西北太平洋反氣旋異常的影響.本文利用觀測(cè)數(shù)據(jù)和耦合數(shù)值模式進(jìn)一步分析了厄爾尼諾衰亡年印度洋增暖的氣候效應(yīng)，研究了印度洋海溫異常與西北太平洋反氣旋異常之間的遙強(qiáng)迫形成條件，提出印度洋背景風(fēng)場(chǎng)的季節(jié)性轉(zhuǎn)換對(duì)印度洋增暖效應(yīng)的關(guān)鍵作用.結(jié)果表明，只有在有利的背景風(fēng)場(chǎng)下，即南亞夏季季風(fēng)完全爆發(fā)時(shí)，才更有利于印度洋增暖效應(yīng)的充分體現(xiàn).可能是由于Kelvin波-Ekman輻散機(jī)制，在北印度洋異常增暖所導(dǎo)致的大氣熱源異常的東側(cè)低層大氣中產(chǎn)生了明顯的東風(fēng)異常，這一東風(fēng)異常對(duì)西北太平洋產(chǎn)生遙強(qiáng)迫，使西北太平洋的反氣旋異常加強(qiáng)并維持到厄爾尼諾衰亡年夏季.這對(duì)于東亞夏季季風(fēng)的年變率機(jī)制研究及預(yù)測(cè)有著重要意義.

關(guān)鍵詞：厄爾尼諾衰亡年；印度洋增暖；南亞夏季風(fēng)；西北太平洋反氣旋異常；東亞夏季風(fēng)

來源出版物：中國(guó)科學(xué)：地球科學(xué)，2013，43（2）： 220-231

華南冬季氣溫異常與ENSO的關(guān)系

伍紅雨，潘蔚娟，王婷

摘要：利用1951—2012年華南192個(gè)測(cè)站逐月氣溫資料、NCEP/NCAR再分析月資料、NCC的ENSO監(jiān)測(cè)資料，采用相關(guān)分析和合成分析等方法分析了華南冬季氣溫異常與ENSO的關(guān)系.結(jié)果表明：華南冬季氣溫對(duì)La Ni?a事件的響應(yīng)比對(duì)E1 Ni?o事件顯著，La Ni?a事件當(dāng)年華南冬季氣溫以偏低為主，極強(qiáng)La Ni?a事件對(duì)應(yīng)的華南冬季氣溫顯著偏低，而中部型La Ni?a事件出現(xiàn)過華南冬季氣溫顯著偏高的情況.當(dāng)La Ni?a（El Ni?o）事件為東部型、Ni?o區(qū)海溫異常的峰值月份出現(xiàn)在秋冬季，當(dāng)年華南冬季氣溫易偏低（高）.從年際尺度上，當(dāng)La Ni?a發(fā)生時(shí)，在對(duì)流層低層激發(fā)西太平洋異常氣旋環(huán)流和北風(fēng)異常，對(duì)應(yīng)對(duì)流層中層北太平洋高壓、烏拉爾山高壓脊和東亞大槽南段均加強(qiáng)，西太平洋副熱帶高壓減弱，東亞中高緯經(jīng)向環(huán)流明顯，冬季風(fēng)偏強(qiáng)，導(dǎo)致我國(guó)大部分地區(qū)包括華南冬季氣溫偏冷，反之亦然.El Ni?o事件對(duì)華南冬季氣溫的影響具有年代際差異.對(duì)應(yīng)華南冬季氣溫年代際變化的海溫變化明顯的區(qū)域位于北太平洋，而與ENSO關(guān)系不明顯.

關(guān)鍵詞：冬季氣溫；厄爾尼諾；拉尼娜；海溫距平；華南

來源出版物：氣象，2014，40（10）：1230-1239聯(lián)系郵箱：伍紅雨，wuhy@grmc.gov.cn

黑潮入侵南海的強(qiáng)弱與太平洋年代際變化及厄爾尼諾-南方濤動(dòng)現(xiàn)象的關(guān)系

楊龍奇，許東峰，徐鳴泉，等

摘要：在黑潮入侵南海強(qiáng)弱的問題上，到底是太平洋年代際變化（Pacific Decadal Oscillation，PDO）還是厄爾尼諾浦方濤動(dòng)（El Ni?o-Southern Oscillation，ENSO）現(xiàn)象在起關(guān)鍵作用，目前還存在著較大爭(zhēng)議.本文先以高鹽水作為黑潮入侵強(qiáng)弱的示蹤物，用1200E斷面的高鹽水?dāng)?shù)據(jù)和北赤道流分叉點(diǎn)（North Equator Current Bifurcation，NEC-Y）的南北變動(dòng)進(jìn)行相關(guān)分析，接著，進(jìn)一步用學(xué)者所用的黑潮入侵指數(shù)（KI指數(shù)，Kuroshio intrusion index和NEC指數(shù)，North Equatorial Current index）與北赤道流分叉點(diǎn)南北變動(dòng)進(jìn)行相關(guān)分析.最后，用EMD（Empirical Mode Decomposition）方法和相關(guān)關(guān)系分析法分別分析了PD（指數(shù)、Ni?o3.4指數(shù)與北赤道流分叉點(diǎn)南北變動(dòng)的關(guān)系并用NECP風(fēng)場(chǎng)數(shù)據(jù)探討其影響機(jī)制.結(jié)果表明：（1）通過對(duì)1200E斷面的高鹽水的KI指數(shù)、NEC指數(shù)與NEC-Y的相關(guān)分析，表明了北赤道流分叉點(diǎn)的南北變動(dòng)能夠很好地指代黑潮入侵南海的強(qiáng)弱；（2）通過PD（指數(shù)和Ni?o3.4指數(shù)與北赤道流分叉點(diǎn)的南北變動(dòng)的相關(guān)性分析，發(fā)現(xiàn)PD（指數(shù)、Ni?o3.4指數(shù)與北赤道流分叉點(diǎn)的南北變動(dòng)都具有較好的相關(guān)性，都在0.5水平.這些良好的相關(guān)性表明了PDO和ENSO對(duì)黑潮入侵南海的強(qiáng)弱都具有重要的影響；（3）當(dāng)處于厄爾尼諾年（拉尼娜）時(shí)，赤道太平洋發(fā)生西（東）風(fēng)異常，使得北赤道流分叉點(diǎn)偏北（南），使呂宋島東側(cè)的黑潮流速減弱（加強(qiáng)），黑潮入侵南海增強(qiáng)（減弱）；當(dāng)PDO處于暖（冷）階段時(shí)，會(huì)加強(qiáng)熱帶太平洋的西（東）風(fēng)異常，使得黑潮入侵南海增強(qiáng)（減弱）.

關(guān)鍵詞：黑潮入侵；北赤道流分叉點(diǎn)；太平洋年代際變化；厄爾尼諾—南方濤動(dòng)

來源出版物：海洋學(xué)報(bào)，2014，36（7）： 17-26聯(lián)系郵箱：許東峰，xudongfengyh@yahoo.com

熱帶印度洋-太平洋三極模態(tài)的理論探討

連濤，陳大可，YouMin TANG

摘要：熱帶太平洋的厄爾尼諾-南方濤動(dòng)（El Ni?o-Southern Oscillation，ENSO）現(xiàn)象是過去幾十年里海洋與氣候研究的重點(diǎn).隨著近年來印度洋偶極子模態(tài)（Indian Ocean Dipole，IOD）的提出，熱帶印度洋中的短期氣候變化也逐步被重視.然而，人們對(duì)這些現(xiàn)象的研究更多的是局限在單個(gè)的海盆之內(nèi)，而不是將其作為一個(gè)整體來思考.觀測(cè)表明，在年際間尺度上，熱帶印度洋和熱帶太平洋的海表溫度異常（Sea Surface Temperature Anomaly，SSTA）和海表高度異常（Sea Surface Height Anomaly，SSHA）等物理量的有著很明顯的反向變化趨勢(shì).對(duì)這種反向變化可以給出一個(gè)簡(jiǎn)單的解釋：由于雙圈沃克環(huán)流在暖池區(qū)幅聚上升，海表風(fēng)場(chǎng)在熱帶印度洋為西風(fēng)，在熱帶太平洋為東風(fēng)；它們通過驅(qū)動(dòng)海水的上翻使得熱帶西印度洋與東太平洋SSTA變冷，SSHA變低，同時(shí)也通過暖水的堆積使得暖池區(qū)SSTA升高，SSHA增加.這樣就在整個(gè)熱帶印度洋-太平洋地區(qū)形成了一個(gè)SSTA和SSHA的三極子結(jié)構(gòu).隨著熱帶印度洋-太平洋上空沃克環(huán)流圈的增強(qiáng)或減弱，兩個(gè)海洋之間的反向梯度關(guān)系也會(huì)隨之做相應(yīng)的調(diào)整，并通過梯度與沃克環(huán)流之間的正反饋?zhàn)饔玫靡跃S持.這一振蕩模態(tài)被稱為印-太三極子（Indo-Pacific Tripole，IPT）.本文將通過資料分析和一個(gè)簡(jiǎn)單的概念模型來討論IPT模態(tài)的發(fā)展和變化機(jī)制，并著重考慮ENSO與IOD對(duì)IPT模態(tài)的影響.該模型包含了最基本的海洋與大氣的物理變量和他們之間的相互作用，可以為更深層次地理解和研究熱帶地區(qū)短期氣候變化提供重要參考.

關(guān)鍵詞：厄爾尼諾；印度洋偶極子；印-太三極子

來源出版物：中國(guó)科學(xué)：地球科學(xué)，2014，44（1）： 169-186

與厄爾尼諾和拉尼娜相聯(lián)系的中國(guó)南方冬季降水的年代際異常特征

袁媛，李崇銀，楊崧

摘要：利用 NCEP/NCAR再分析大氣環(huán)流資料、哈得來中心海溫資料、中國(guó)700多站降水資料以及全球格點(diǎn)降水資料，詳細(xì)分析了中國(guó)南方冬季降水異常的特征，并揭示了其所對(duì)應(yīng)的歐亞大氣環(huán)流和東亞冬季風(fēng)異常與ENSO事件的聯(lián)系，以及ENSO暖/冷位相對(duì)其影響的非對(duì)稱性.研究進(jìn)一步證明了厄爾尼諾是導(dǎo)致中國(guó)南方冬季降水偏多的重要外強(qiáng)迫因子，并指出拉尼娜對(duì)中國(guó)南方冬季降水的影響表現(xiàn)出明顯的年代際變化特征.1980年之前的拉尼娜年冬季，東亞冬季風(fēng)顯著偏強(qiáng)，東亞大槽偏深，西北太平洋副熱帶高壓偏弱偏東，中國(guó)南方受一致偏北風(fēng)影響，氣溫偏低，降水偏少，多表現(xiàn)為冷干的氣候特征.但1980年之后的拉尼娜年冬季，東亞大槽偏弱，印緬槽偏強(qiáng)，同時(shí)在菲律賓以西激發(fā)出異常氣旋性環(huán)流，使得異常偏東風(fēng)控制中國(guó)南方，有利于熱帶水汽輸送增強(qiáng)，因此降水偏多.同時(shí)，1980年之后的拉尼娜事件還使得東亞副熱帶西風(fēng)急流偏強(qiáng)偏北，中國(guó)南方處于急流人口區(qū)的右側(cè)，通過二級(jí)環(huán)流使得中國(guó)南方上空的上升運(yùn)動(dòng)偏強(qiáng)，有利于降水偏多.因此，1980年之后的拉尼娜年冬季，中國(guó)南方易表現(xiàn)出冷濕的氣候特征，有時(shí)也容易發(fā)生低溫雨雪冰凍災(zāi)害.進(jìn)一步分析表明，1980年以后拉尼娜成熟期海溫異常空間分布型的變化，以及北半球大氣環(huán)流的年代際變化可能是導(dǎo)致拉尼娜對(duì)東業(yè)大氣環(huán)流的影響在1980年之后發(fā)生變化的重要原因.

關(guān)鍵詞：東亞冬季風(fēng)；冬季降水；厄爾尼諾和拉尼娜；非對(duì)稱性；年代際變化

來源出版物：氣象學(xué)報(bào)，2014，72（2）： 237-255聯(lián)系郵箱：袁媛，yuany@cma.gov.cn

Roles of ENSO and PDO in the link of the East Asian winter monsoon to the following summer monsoon

Wen Chen； Juan Feng； Renguang Wu

Abstract： The present study investigates the roles of El Ni?o-Southern Oscillation（ENSO）and the Pacific decadal oscillation（PDO）in therelationship between the East Asian winter monsoon（EAWM）and the following East Asian summer monsoon（EASM）. The variability of the EAWM is divided into an ENSO-related part named EAWM EN and an ENSO-unrelated part named EAWM res. Corresponding to a weak EAWM EN，an anomalous low-level anticyclone forms over the western North Pacific（WNP）and persists from winter to the following summer. This anticyclone enhances southerlies over the coast of East Asia in summer. Hence，a weak EAWM EN tends to be followed by a strong EASM and vice versa. As such，a link is established between the EAWM EN and the EASM. The persistence of this WNP anticyclone may be mainly attributed to the sea surface temperature anomalies associated with the ENSO-related EAWM part in the tropical Indian Ocean and the extratropical North Pacific. In contrast，corresponding to a weak EAWM res，the anomalous WNP anticyclone is only seen in winter，and there is no obvious relationship between the EAWM res and the following EASM. Therefore，the observed EAWM-EASM relationship is dominated by the winter monsoon variability associated with ENSO. It is found that the EAWM EN-EASM relationship is modulated by the PDO. There tends to be a much stronger EASM after a weak EAWM EN during the positive PDO phases than during the negative PDO phases.

來源出版物：Journal of Climate，2013，26（2）： 622-635

A new paradigm for the predominance of standing Central Pacific Warming after the late 1990s

Xiang，Baoqiang； Wang，Bin； Li，Tim

Abstract： Canonical El Ni?o has a warming center in the eastern Pacific（EP），but in recent decades，El Ni?o warming center tends to occur more frequently in the central Pacific（CP）. The definitions and names of this new type of El Ni?o，however，have been notoriously diverse，which makes it difficult to understand why the warming center shifts. Here，we show that the new type of El Ni?o events is characterized by： 1）the maximum warming standing and persisting in the CP and 2）the warming extending to the EP only briefly during its peak phase. For this reason，we refer to it as standing CP warming（CPW）. Global warming has been blamed for the westward shift of maximum warming as well as more frequent occurrence of CPW. However，we find that since the late 1990s the standing CPW becomes a dominant mode in the Pacific； meanwhile，the epochal mean trade winds have strengthened and the equatorial thermocline slope has increased，contrary to the global warming-induced weakening trades and flattening thermocline. We propose that the recent predominance of standing CPW arises from a dramatic decadal change characterized by a grand La Ni?a-like background pattern and strong divergence in the CP atmospheric boundary layer. After the late 1990s，the anomalous mean CP wind divergence tends to weaken the anomalous convection and shift it westward from the underlying SST warming due to the suppressed low-level convergence feedback. This leads to a westward shift of anomalous westerly response and thus a zonally in-phase SST tendency，preventing eastward propagation of the SST anomaly. We anticipate more CPW events will occur in the coming decade provided the grand La Ni?a-like background state persists.

Keywords： Central Pacific Warming； La Ni?a-like mean state change； Convection； Low-level convergence feedback

來源出版物：Climate Dynamics，2013，41（2）： 327-340聯(lián)系郵箱：Xiang，Baoqiang； baoqiang@hawaii.edu

Late-twentieth-century emergence of the El Ni?o propagation asymmetry and future projections

Santoso，Agus； McGregor，Shayne； Jin，F(xiàn)eifei； et al.

Abstract： The El Ni?o/Southern Oscillation（ENSO）is the Earth’s most prominent source of interannual climate variability，exerting profound worldwide effects（1-7）. Despite decades of research，its behaviour continues to challenge scientists. In the eastern equatorial Pacific Ocean，the anomalously cool sea surface temperatures（SSTs）found during La Ni?a events and the warm waters of modest El Ni?o events both propagate westwards，as in the seasonal cycle（7）. In contrast，SST anomalies propagate eastwards during extreme El Ni?o events，prominently in the post-1976 period（7-10），spurring unusual weather events worldwide with costly consequences（3-6，11）. The cause of this propagation asymmetry is currently unknown（10）. Here we trace the cause of the asymmetry to the variations in upper ocean currents in the equatorial Pacific，whereby the westward-flowing currents are enhanced during La Ni?a events but reversed during extreme El Ni?o events. Our results highlight that propagation asymmetry is favoured when the westward mean equatorial currents weaken，as is projected to be the case under global warming（12-14）. By analysing past and future climate simulations of an ensemble of models with more realistic propagation，we find a doubling in the occurrences of El Ni?o events that feature prominent eastward propagation characteristics in a warmer world. Our analysis thus suggests that more frequent emergence of propagation asymmetry will be an indication of the Earth’s warming climate.

Keywords： tropical pacific； ENSO dynamics； ocean； model； simulations； evolution； ensemble； feedback； events； impact

來源出版物：Nature，2013，504（7478）： 126-130聯(lián)系郵箱：Santoso，Agus； a.santoso@unsw.edu.au

Sea surface temperature in the north tropical Atlantic as a trigger for El Ni?o/Southern Oscillation events

Ham，Yoo-Geun； Kug，Jong-Seong； Park，Jong-Yeon； et al.

Abstract： El Ni?o events，the warm phase of the El Ni?o/Southern Oscillation（ENSO），are known to affect other tropical ocean basins through teleconnections. Conversely，mounting evidence suggests that temperature variability in the Atlantic Ocean may also influence ENSO variability（1-5）. Here we use reanalysis data and general circulation models to show that sea surface temperature anomalies in the north tropical Atlantic during the boreal spring can serve as a trigger for ENSO events. We identify a subtropical teleconnection in which spring warming in the north tropical Atlantic can induce a low-level cyclonic atmospheric flow over the eastern Pacific Ocean that in turn produces a low-level anticyclonic flow over the western Pacific during the following months. This flow generates easterly winds over the western equatorial Pacific that cool the equatorial Pacific and may trigger a La Ni?a event the following winter. In addition，El Ni?o events led by cold anomalies in the north tropical Atlantic tend to be warm-pool El Ni?o events，with a centre of action located in the central Pacific（6，7），rather than canonical El Ni?o events. We suggest that the identification of temperature anomalies in the north tropical Atlantic could help to forecast the development of different types of El Ni?o event.

Keywords： NI?O-southern-oscillation； indian-ocean； warm pool； variability； ENSO； pacific； SST； circulation； rainfall； climate

來源出版物：Nature Geoscience，2013，6（2）： 112-116聯(lián)系郵箱：Ham，Yoo-Geun； jskug@kiost.ac

Improved El Ni?o forecasting by cooperativity detection

Ludescher，Josef； Gozolchiani，A； Bogachev，Mikhail I； et al.

Abstract： Although anomalous episodic warming of the eastern equatorial Pacific，dubbed El Ni?o by Peruvian fishermen，has major（and occasionally devastating）impacts around the globe，robust forecasting is still limited to about 6 mo ahead. A significant extension of the prewarning time would be instrumental for avoiding some of the worst damages such as harvest failures in developing countries. Here we introduce a unique avenue toward El Ni?o prediction based on network methods，inspecting emerging teleconnections. Our approach starts from the evidence that a large-scale cooperative mode-linking the El Ni?o basin（equatorial Pacific corridor）and the rest of the ocean-builds up in the calendar year before the warming event. On this basis，we can develop an efficient 12-mo forecasting scheme，i.e.，achieve some doubling of the early-warning period. Our method is based on high-quality observational data available since 1950 and yields hit rates above 0.5，whereas false-alarm rates are below 0.1.

Keywords： climate； cross-correlations； dynamic networks； ENSO； spring barrier

來源出版物：Proceedings of the National Academy of Sciences of the United States of America，2013，110（29）： 11742-11745

Impact of East Asian winter and Australian summer monsoons on the enhanced surface westerlies over the western tropical Pacific Ocean preceding the El Ni?o onset

Zheng，Yangxing； Zhang，Renhe； Bourassa，Mark A.

Abstract： Composite analysis from NCEP-NCAR reanalysis datasets over the period 1948-2007 indicates that stronger East Asian winter monsoons（EAWM）and stronger Australian summer monsoons（ASM）generally coexist in boreal winters preceding the onset of El Ni?o，although the EAWM tend to be weak after 1990，probably because of the decadal shift of EAWM and the change in El Ni?o events from cold-tongue type to warm-pool type. The anomalous EAWM and ASM enhance surface westerlies over the western tropical Pacific Ocean（WTP）. It is proposed that the enhanced surface westerlies over the WTP prior to El Ni?o onset are generally associated with the concurrent anomalous EAWM and ASM. A simple analytical atmospheric model is constructed to test the hypothesis that the emergence of enhanced surface westerlies over the WTP can be linked to concurrent EAWM and ASM anomalies. Model results indicate that，when anomalous northerlies from the EAWM converge with anomalous southerlies from the ASM，westerly anomalies over the WTP are enhanced. This result provides a possible explanation of the co-impact of the EAWM and the ASM on the onset of El Ni?o through enhancing the surface westerly over the WTP.

Keywords： atmospheric circulation； forcing； dynamics； monsoons； wind

來源出版物：Journal of Climate，2014，27（5）： 1928-1944

Cold Tongue and Warm Pool ENSO Events in CMIP5： Mean State and Future Projections

Taschetto，Andrea S； Sen Gupta，Alexander； Jourdain，Nicolas C； et al.

Abstract： The representation of the El Ni?o-Southern Oscillation（ENSO）under historical forcing and future projections is analyzed in 34 models from the Coupled Model Intercomparison Project phase 5（CMIP5）. Most models realistically simulate the observed intensity andlocation of maximum sea surface temperature（SST）anomalies during ENSO events. However，there exist systematic biases in the westward extent of ENSO-related SST anomalies，driven by unrealistic westward displacement and enhancement of the equatorial wind stress in the western Pacific. Almost all CMIP5 models capture the observed asymmetry in magnitude between the warm and cold events（i.e.，El Ni?os are stronger than La Ni?as）and between the two types of El Ni?os： that is，cold tongue（CT）El Ni?os are stronger than warm pool（WP）El Ni?os. However，most models fail to reproduce the asymmetry between the two types of La Ni?as，with CT stronger than WP events，which is opposite to observations. Most models capture the observed peak in ENSO amplitude around December； however，the seasonal evolution of ENSO has a large range of behavior across the models. The CMIP5 models generally reproduce the duration of CT El Ni?os but have biases in the evolution of the other types of events. The evolution of WP El Ni?os suggests that the decay of this event occurs through heat content discharge in the models rather than the advection of SST via anomalous zonal currents，as seems to occur in observations. No consistent changes are seen across the models in the location and magnitude of maximum SST anomalies，frequency，or temporal evolution of these events in a warmer world.

Keywords： climate change； climate variability； ENSO； climate models； atmosphere-ocean interaction； model evaluation/performance

來源出版物：Journal of Climate，2014，27（8）： 2861-2885聯(lián)系郵箱：Taschetto，Andrea S； a.taschetto@unsw.edu.au

Holocene history of ENSO variance and asymmetry in the eastern tropical Pacific

Carre，Matthieu； Sachs，Julian P； Purca，Sara； et al.

Abstract： Understanding the response of the El Ni?o-Southern Oscillation（ENSO）to global warming requires quantitative data on ENSO under different climate regimes. Here，we present a reconstruction of ENSO in the eastern tropical Pacific spanning the past 10000 years derived from oxygen isotopes in fossil mollusk shells from Peru. We found that ENSO variance was close to the modern level in the early Holocene and severely damped similar to 4000 to 5000 years ago. In addition，ENSO variability was skewed toward cold events along coastal Peru 6700 to 7500 years ago owing to a shift of warm anomalies toward the Central Pacific. The modern ENSO regime was established similar to 3000 to 4500 years ago. We conclude that ENSO was sensitive to changes in climate boundary conditions during the Holocene，including but not limited to insolation.

Keywords： El-Ni?o/southern-oscillation； southern-oscillation； Ni?o； PERU； variability； climate； record； reconstructions； simulations；midholocene

來源出版物：Science，2014，345（6200）： 1045-1048聯(lián)系郵箱：Carre，Matthieu； matthieu.carre@univ-montp2.fr

Different impacts of various El Ni?o events on the Indian Ocean Dipole

Wang，Xin； Wang，Chunzai

Abstract： Our early work（Wang and Wang in J Clim 26：1322-1338，2013）separates El Ni?o Modoki events into El Ni?o Modoki I and II because they show different impacts on rainfall in southern China and typhoon landfall activity. The warm SST anomalies originate in the equatorial central Pacific and subtropical northeastern Pacific for El Ni?o Modoki I and II，respectively. El Ni?o Modoki I features a symmetric SST anomaly distribution about the equator with the maximum warming in the equatorial central Pacific，whereas El Ni?o Modoki II shows an asymmetric distribution with the warm SST anomalies extending from the northeastern Pacific to the equatorial central Pacific. The present paper investigates the influence of the various groups of El Ni?o events on the Indian Ocean Dipole（IOD）. Similar to canonical El Ni?o，El Ni?o Modoki I is associated with a weakening of the Walker circulation in the Indo-Pacific region which decreases precipitation in the eastern tropical Indian Ocean and maritime continent and thus results in the surface easterly wind anomalies off Java-Sumatra. Under the Bjerknes feedback，the easterly wind anomalies induce cold SST anomalies off Java- Sumatra，and thus a positive IOD tends to occur in the Indian Ocean during canonical El Ni?o and El Ni?o Modoki I. However，El Ni?o Modoki II has an opposite impact on the Walker circulation，resulting in more precipitation and surface westerly wind anomalies off Java-Sumatra. Thus，El Ni?o Modoki II is favorable for the onset and development of a negative IOD on the frame of the Bjerknes feedback.

Keywords： sea-surface temperature； tropical circulation； walker circulation； pacific climate； coupled GCM； variability； ENSO； rainfall；modok I； mode

來源出版物：Climate Dynamics，2014，42（3-4）： 991-1005聯(lián)系郵箱：Wang，Chunzai； chunzai.wang@noaa.gov

Nonlinear precipitation response to El Ni?o and global warming in the Indo-Pacific

Chung，Christine T. Y； Power，Scott B； Arblaster，Julie M； et al.

Abstract： Precipitation changes over the Indo-Pacific during El Nio events are studied using an Atmospheric General Circulation Model forced with sea-surface temperature（SST）anomalies and changes in atmospheric CO2concentrations. Linear increases in the amplitude of the El Ni?o SST anomaly pattern trigger nonlinear changes in precipitation amounts，resulting in shifts in the location and orientation of theIntertropical Convergence Zone（ITCZ）and the South Pacific Convergence Zone（SPCZ）. In particular，the maximum precipitation anomaly along the ITCZ and SPCZ shifts eastwards，the ITCZ shifts south towards the equator，and the SPCZ becomes more zonal. Precipitation in the equatorial Pacific also increases nonlinearly. The effect of increasing CO2levels and warming SSTs is also investigated. Global warming generally enhances the tropical Pacific precipitation response to El Ni?o. The precipitation response to El Ni?o is found to be dominated by changes in the atmospheric mean circulation dynamics，whereas the response to global warming is a balance between dynamic and thermodynamic changes. While the dependence of projected climate change impacts on seasonal variability is well-established，this study reveals that the impact of global warming on Pacific precipitation also depends strongly on the magnitude of the El Ni?o event. The magnitude and structure of the precipitation changes are also sensitive to the spatial structure of the global warming SST pattern.

Keywords： El-Ni?o Southern Oscillation； global warming； climate change； climate variability

來源出版物：Climate Dynamics，2014，42（7-8）： 1837-1856聯(lián)系郵箱：Chung，Christine T. Y； c.chung@bom.gov.au

Very early warning of next El Ni?o

Ludescher，Josef； Gozolchiani，Avi ； Bogachev，Mikhail I； et al.

Abstract： The most important driver of climate variability is the El Ni?o Southern Oscillation，which can trigger disasters in various parts of the globe. Despite its importance，conventional forecasting is still limited to 6 mo ahead. Recently，we developed an approach based on network analysis，which allows projection of an El Ni?o event about 1 y ahead. Here we show that our method correctly predicted the absence of El Ni?o events in 2012 and 2013 and now announce that our approach indicated（in September 2013 already）the return of El Ni?o in late 2014 with a 3-in-4 likelihood. We also discuss the relevance of the next El Ni?o to the question of global warming and the present hiatus in the global mean surface temperature.

Keywords： dynamic networks； ENSO； spring barrier

來源出版物：Proceedings of the National Academy of Sciences of the United States of America，2014，111（6）： 2064-2066

聯(lián)系郵箱：Schellnhuber，Hans Joachim； john@pik-potsdam.de

Seasonal Predictability over Europe Arising from El Ni?o and Stratospheric Variability in the MPI-ESM Seasonal Prediction System

Domeisen，Daniela I. V； Butler，Amy H； Froehlich，Kristina； et al.

Abstract： Predictability on seasonal time scales over the North Atlantic-Europe region is assessed using a seasonal prediction system based on an initialized version of the Max Planck Institute Earth System Model（MPI-ESM）. For this region，two of the dominant predictors on seasonal time scales are El Ni?o-Southern Oscillation（ENSO）and sudden stratospheric warming（SSW）events. Multiple studies have shown a potential for improved North Atlantic predictability for either predictor. Their respective influences are however difficult to disentangle，since the stratosphere is itself impacted by ENSO. Both El Ni?o and SSW events correspond to a negative signature of the North Atlantic Oscillation（NAO），which has a major influence on European weather. This study explores the impact on Europe by separating the stratospheric pathway of the El Ni?o teleconnection. In the seasonal prediction system，the evolution of El Ni?o events is well captured for lead times of up to 6 months，and stratospheric variability is reproduced with a realistic frequency of SSW events. The model reproduces the El Ni?o teleconnection through the stratosphere，involving a deepened Aleutian low connected to a warm anomaly in the northern winter stratosphere. The stratospheric anomaly signal then propagates downward into the troposphere through the winter season. Predictability of 500-hPa geopotential height over Europe at lead times of up to 4 months is shown to be increased only for El Ni?o events that exhibit SSW events，and it is shown that the characteristic negative NAO signal is only obtained for winters also containing major SSW events for both the model and the reanalysis data.

Keywords： quasi-biennial oscillation； low-top versions； sudden warmings； southern-oscillation； northern winter； CMIP5 simulations；weather regimes； forecast skill； climate model； ENSO

來源出版物：Journal of Climate，2015，28（1）： 256-271聯(lián)系郵箱：Domeisen，Daniela I. V； daniela.domeisen@zmaw.de

Impacts of variations in the strength and structure of El Ni?o events on Pacific rainfall in CMIP5 models

Murphy，Bradley F； Ye，Hua； Delage，F(xiàn)rancois

Abstract： El Ni?o-Southern Oscillation（ENSO）plays a dominant role in interannual climate variability in Pacific island countries，directly affecting lives there. Many countries show different rainfall responses depending on the sea surface temperature（SST）structure of different types of El Ni?o events. El Ni?o events are classified into three types based on previous studies： those with strongest SST anomalies in theeastern Pacific Cold Tongue region（CTE），in the Western Pacific Warm Pool region（WPE），and those in between，a “Mixed” El Ni?o（MxE），and results from 30 CMIP5 models are investigated. These models accurately reproduce observed SST and precipitation anomalies for the three El Ni?o types and La Ni?a. CMIP5 models simulate much larger ranges in the strength of ENSO events than observed. Results clarify the roles of both the different structures of El Ni?o SST anomalies and their magnitudes on rainfall in the Pacific，and demonstrate that each of the three El Ni?o types has different impacts on rainfall in the region. These impacts vary with location，with WPE and CTE producing very different impacts in most Pacific island countries. There is a linear intensification of both the mean and maximum rainfall anomalies in the equatorial Pacific as the events become stronger. Equatorial rainfall shifts eastward in CTE and MxE，westward in La Ni?a. Both the South Pacific and Intertropical Convergence Zones（SPCZ and ITCZ）shift equatorward in El Ni?oand poleward in La Ni?a，the shifts increasing as events strengthen. WPE show different behaviour to other events，with little east-west shift in equatorial rainfall，and the orientation angle of the convergence zones increases. Identification of models with no erroneous westward bias in SST anomalies has clarified the effect of strong CTE events producing “zonal” SPCZ and shifting rainfall away to the east from western equatorial countries.

Keywords： El Ni?o； Pacific rainfall； climate variability； CMIP5

來源出版物：Climate Dynamics，2015，44（11-12）： 3171-3186聯(lián)系郵箱：Murphy，Bradley F； B.Murphy@bom.gov.au

Strong influence of westerly wind bursts on El Ni?o diversity

Chen，Dake； Lian，Tao； Fu，Congbin； et al.

Abstract： Despite the tremendous progress in the theory，observation and prediction of El Ni?o over the past three decades，the classification of El Ni?o diversity and the genesis of such diversity are still debated. This uncertainty renders El Ni?o prediction a continuously challenging task，as manifested by the absence of the large warm event in 2014 that was expected by many. We propose a unified perspective on El Ni?o diversity as well as its causes，and support our view with a fuzzy clustering analysis and model experiments. Specifically，the interannual variability of sea surface temperatures in the tropical Pacific Ocean can generally be classified into three warm patterns and one cold pattern，which together constitute a canonical cycle of El Ni?o/La Ni?a and its different flavours. Although the genesis of the canonical cycle can be readily explained by classic theories，we suggest that the asymmetry，irregularity and extremes of El Ni?o result from westerly wind bursts，a type of state-dependent atmospheric perturbation in the equatorial Pacific. Westerly wind bursts strongly affect El Ni?o but not La Ni?a because of their unidirectional nature. We conclude that properly accounting for the interplay between the canonical cycle and westerly wind bursts may improve El Ni?o prediction.

Keywords： sea-surface temperature； southern oscillation； tropical pacific； equatorial pacific； conceptual-model； warm pool； La-Nina；ENSO； events； predictability

來源出版物：Nature Geoscience，2015，8（5）： 339-345聯(lián)系郵箱：Chen，Dake； dchen@sio.org.cn

編輯：衛(wèi)夏雯

The tendency for more frequent El Ni?o events and fewer La Ni?a events since the late 1970’s has been linked to decadal changes in climate throughout the Pacific basin. Aspects of the most recent warming in the tropical Pacific from 1990 to 1995，which are connected to but not synonymous with El Ni?o，are unprecedented in the climate record of the past 113 years. There is a distinction between El Ni?o（EN），the Southern Oscillation（SO）in the atmosphere，and ENSO，where the two are strongly linked，that emerges clearly on decadal time scales. In the traditional El Ni?o region，sea surface temperature anomalies（SSTAs）have waxed and waned，while SSTAs in the central equatorial Pacific，which are better linked to the SO，remained positive from 1990 to June 1995. We carry out several statistical tests to assess the likelihood that the recent behavior of the SO is part of a natural decadal-timescale variation. One test fits an autoregressive-moving average（ARMA）model to a measure of the SO given by the first hundred years of the pressures at Darwin，Australia，beginning in 1882. Both the recent trend for more ENSO events since 1976 and，the prolonged 1990-1995 ENSO event are unexpected given the previous record，with a probability of occurrence about once in 2000 years. This opens up the possibility that the ENSO changes may be partly caused by the observed increases in greenhouse gases.

SEA-surface temperature； extratropical response； southern oscillation； northern winter； pacific； organization； atmosphere；transients； anomalies； models

典

文章題目第一作者來源出版物1The 1990-1995 El Ni?o Southern Oscillation event： Longest on recordTrenberth，KEGeophysical Research Letters，1996，23（1）：57-60 2 El Ni?o，La Ni?a，and the nonlinearity of their teleconnections Hoerling，MP 4 ENSO as an integrating concept in Earth science McPhaden，Michael J

The 1990-1995 El Ni?o Southern Oscillation event： Longest on record

Trenberth，KE； Hoar，TJ

*摘編自《海洋環(huán)境科學(xué)》2015年34卷3期：473～480頁(yè)，圖、表、參考文獻(xiàn)已省略.