海-陆-气相互作用-第三讲(ENSO1)

J. Bjerknes (1969) recognized that El Niñ o is the product of
interaction between the ocean and atmosphere: A positive oceanatmosphere feedback.
Anomaly
ENSO形成的可能机制
1、海气相互作用理论（Bjerknes, 1969）
2、信风张弛理论（Wyrtki, 1975, 1982） 3、不稳定海洋波动理论（ McCreary, 1984; Hirst, 1986; Chao, 1993; ….）；热带波
动理论（ Philander, 1984; Gill, 1993;



No stronger trade winds prior to 1982. No warming off the coast of South America in early 1982. Warming starts in the western Pacific. Interannual anomalies propagate eastward. ENSO is the largest climate phenomenon in the instrumental record. ENSO impacts global climate, weather, hurricanes, and so on.
海-陆-气相互作用
周顺武、智海
南京信息工程大学大气科学学院
热带太平洋海气相互作用
热带太平洋海洋—大气耦合系统的年际变化
——ENSO
ENSO 现象及研究历史
ENSO 发生时大气海洋变化 ENSO 监测 ENSO 事件的差异性 ENSO 形成的早期信号 ENSO 对气候的影响 ENSO 预测现状、研究存在的主要问题
After the seminal work of J. Bjerknes (1969), scientists recognize
that El Niñ o and the Southern Oscillation are simply aspects of the same coupled ocean-atmosphere mode. They are two sides of the same coin.
Jacob Bjerknes Mechanism
Weaker trade winds——stronger west wind
anomalies
Weaker upwelling——deeper thermocline depth
Stronger convection
Stronger westerly wind
研究历史
Walker (1923, 1924) discovered the Southern Oscillation (SO): A seesaw in SLP between the Western and Eastern Hemispheres Walker’s SO Presented by Berlage (1957): Correlation of global SLP with SLP at Djakarta, Indonesia
注意：位于赤道以南的东南太平洋的东南大西洋的冷水区的高云量为层云的云量
ENSO study is a major focus after the 1980s: Why?

The intense 1982-83 El Niñ o surprises the scientific community. It was not recognized until it was well developed. The 1982-83 El Niñ o is not consistent with the results of Wyrtki (1975) and Rasmusson and Carpenter (1982):
热带海洋—大气耦合系统的平均状态 和两个重要的维持机制 1. 赤道东太平洋SST东西不对称：西
高东低？
2. 赤道中东太平洋和大西洋ITCZ年平均 位置在赤道以北？
1. 赤道太平洋海域SST东西不对称：西高东低？ 2. 赤道中东太平洋和大西洋ITCZ年平均位置在
赤道以北？
赤道太平洋（大西洋）Bjerknes）正反馈机制示意图
Eastern Pacific Indian & Western Pacific The pattern is centered in the Southern Hemisphere; This is why Walker called it SO.
J. Bjerknes (1969) named the “Walker Circulation” since it is
SST at Canton Island
The 1957/58 El Niño
The 1972/73 El Niño
Wyrtki’s (1975) Sea Level Buildup in the Western Pacific
High sea level in 1954-56
High sea level in 1970-71
Latitude–depth section of ocean temperature along 90W in the eastern Pacific.
越赤道风-上升流正反馈机制：越赤道南风气流可引起赤道上的强混合
以及赤道以南东边界处的上升流增强，进而导致温跃层上凸，冷水上翻增 强，上翻的冷水在表层风应力作用下向北输送，在赤道以北堆积、下沉， 形成了越赤道的经向翻转环流，导致温跃层在赤道以南较浅和赤道以北较 深的现象，增加赤道南北SST经向梯度，从而进一步加强越赤道南风。
El Niñ o should be credited with arranging a successful merger of meteorology and oceanography, two traditionally separate and independent fields.
A cold phase of ENSO was recently named La Niñ a (Philander 1990).
These high sea levels correspond to the 1957/58 and 1972/73 El Niños.
Wyrtki’s (1975) “Build来自百度文库p” Mechanism
Strong trade wind
West
East
Normal sea level
Sea level with Strong trade wind
Strong easterly wind before El Niño. High sea level in the western Pacific before El Niñ o. A “trigger” is a rapid collapse of easterly wind. He recognized that coastal warming is not a local phenomenon.
Warmer SSTA
Sir Gilbert Thomas Walker, 1868-1958)
Carl Bjerknes
(1825-1903)
Vilhelm Bjerknes (1862-1951) Jacob Berknes (1897-1975)
Jacob Berknes (1897-1975)
So, there exists at least two types of warm events in the
tropical Pacific: one with its warm center located in the east equatorial Pacific near the South America coast, another in the central equatorial Pacific.
….）, 1985）
ENSO形成的可能机制
4、时滞振子（ Battisti ,1988; Suarez, 1988; Neelin, 1991; ….) 5、西风异常对ENSO的影响（Li, 1988, 1990,
1996; ….)
6、印度洋－太平洋齿轮耦合与厄尔尼诺 其他解释……
气候平均态
29
频率在2~7a 之间的结论是一致的。
美国哥伦比亚大学教授，开发了简单海气耦合模式，是第一个用 于ENSO预测的动力模式，成功预报了1986/87和1991/92 EL Nino
事件，但对1994，1997和2002三次 El Nino事件预测不成功。
Zebiak-Cane ENSO预报模式
two types of ENSO
part of the mechanism of Walker’s Southern Oscillation (SO)
Walker’s SO Low SLP Indian Pacific Atlantic Warm Water High SLP Cold Water
Bjerknes also recognized that the gradient of SST along the equator is the cause of the Walker Circulation
（ENSO观测系统）
From Tropical Atmosphere & Ocean
4个ENSO监测区
Nino 3.4 区SST及SOI 功率谱分析
上图给出1856 —2002 年SST及1866 —2002 年SOI 的功率谱。可 以看出，主要峰值集中于年际变化。这与多数学者认为ENSO 的

Wyrtki’s (1975) sea level buildup A strong easterly wind before El Niño
Strong Easterly Wind
Wind Stress (4°N-4°S， 100-140°W)
Wind Stress (4°N-4°S， 140-180°W)
SST
Walker Cell
Surface Wind
Time
For the coupled system to oscillate, a negative feedback is needed.
During that time, J. Bjerknes did not know what causes a turnabout from a warm phase to a cold phase.
Then, scientists study the El Niñ o and the Southern
Oscillation together in what we now call “ENSO”.
El Niñ o: Oceanic Warm SST Southern Oscillation: Atmospheric SLP Seesaw
warm pool El Niñ o (Kug and Jin, 2008).
ENSO Modoki 概念的提出
From Ashok et al. (2007)
两类 ENSO 示意图
From Ashok et al. (2007)
ENSO Indices
Nino3.4
Wang et al. (1999a)
赤道东太平洋和赤道东大西洋附近的越赤道风—上升流正反馈机制示意图
(等值线为沿90W断面年平均（1950—2010年）的等温线，单位：℃)，取自Xie，1998
层云-SST反馈机制: 海温越低，海面边界层越稳定，层云量越多， 海面得到的短波辐射越少，导致海温进一步降低
气候平均（1950—2010年）热带东太平洋和热带大西洋的海平面温度和风场(a)、 云量(b)的空间分布
Some previous studies called the second warm event
date line El Niñ o (Larkin and Harrison, 2005), El Niñ o modoki (Ashok et al. 2007),
central Pacific El Niñ o (Kuo and Yu, 2008),