GRE阅读背景材料：厄尔尼诺现象

 　　新gre阅读之厄尔尼诺。下面为大家搜索整理的新gre阅读之厄尔尼诺，对于新gre 阅读考试，考生除了采取题海战术，其实更应该做的就是总结。今天带来的gre 阅读neirong希望对同学们的gre 考试有所帮助，下面一起来看看吧：

　　The recent, apparently¹ successful prediction by mathematical models of an appearance of EI Nino- the warm ocean current that periodically develops along (5) the Pacific coast of South America-has excited researchers. Jacob Bjerknes pointed² out over 20 years ago how winds might create either abnormally warm or abnormally cold water in the eastern (10) equatorial Pacific. Nonetheless, until the development of the models no one could explain why conditions should regularly shift from one to the other, as happens in the periodic oscillations (15) between appearances of the warm EI Nino and the cold so-called anti-El Nino. The answer, at least if the current model that links the behavior of the ocean to that of the atmosphere is (20) correct, is to be found in the ocean. It has long been known that during an El Nino, two conditions exist: (1) unusually warm water extends along the eastern Pacific, principally along the (25) coasts of Ecuador and Peru, and (2) winds blow from the west into the warmer air rising over the warm water in the east. These winds tend to create a feedback mechanism³ by driving the warmer (30) surface water int a "pile" that blocks the normal upwelling of deeper, cold water in the east and further warms the eastern water, thus strengthening the wind still more. The contribution of (35) the model is to show that the winds of an El Nino, which raise sea level in the cast, simultaneously⁴ send a signal to the west lowering sea level. According to the model, that signal is generated (40) as a negative Rossby wave, a wave of depressed⁵, or negative, sea level, that moves westward⁶ parallel to the equator at 25 to 85 kilometers per day. Taking months to traverse the Pacific, Rossby (45) waves march to the western boundary of the Pacific basin,which is modeled as a smooth wall but in reality consists of quite irregular island chains, such as, the Philippines and Indonesia.

　　(50) When the waves meet the western boundary, they are reflected, and the model predicts that Rossby waves will be broken into numerous coastal⁷ Kelvin waves carrying the same negative (55) sea-level signal. These eventually shoot toward the equator, and then head eastward⁸ along the equator propelled by the rotation⁹ of the Earth at a speed of about 250 kilometers per day. When (60) enough Kelvin waves of sufficient amplitude¹⁰ arrive from the western Pacific, their negative sea-level signal overcomes the feedback mechanism tending to raise the sea level, and they begin (65) to drive the system into the opposite cold mode. This produces a gradual shift in winds, one that will eventually send positive sea-level Rossby waves westward, waves that will eventually (70) return as cold cycle-ending positive Kelvin waves, beginning another warming cycle.

　　数学模型最近对“厄尔尼诺”(El Nino)的出现所作出的显然是成功的预测使研究者们兴奋不已。所谓厄尔尼诺，即一股沿南美洲太平洋海岸周期性发展的海洋暖流。早在20年之前，雅各·皮叶克尼斯(Jacob Bjerknes)指出了风何以可能在东部赤道太平洋地区形成反常温暖或反常寒冷的水域。虽然如此，在上述数学模型得以发展之前，还没有任何人能够解释情况为什么应该有规律地从一种转变为另一种，正如在暖厄尔尼诺和冷厄尔尼诺(或所谓的反厄尔尼诺)出现之间周期性的交替变化中所发生的那样。问题的答案--至少如果目前将海洋的行为与大气层的行为联系起来的模型是正确的话--应从海洋中寻找。

　　长期以来众所周知，在厄尔尼诺出现期间，两个条件必须存在：(1)格外温暖的水流沿着东太平洋延伸，主要是沿厄瓜多尔和秘鲁海岸;(2)风从西部吹向在东部温暖的海水上空升起的较暖的空气。这些风倾向于造成一种反馈机制，迫使较为温暖的表层水形成一“堆状物”，阻挡住东部较深层的、寒冷的水的正常上涌，并进一步使东部的水温度上升，从而更进一步增强风的力度。该模型的贡献是旨在证明，致使海平面在东部海域升高的厄尔尼诺水流的风会同步向西部海域发送一信号，导致海平面降低。按照该模型，那一信号作为一种负罗斯比波(Rossby)而被产生形成，即一种致使海平面沉降、或负增长的波浪，此波浪会以每天85公里的速度平行于赤道西行，此海盆被模拟为一堵平滑的墙，但实际上却是由极不规则的群岛系列构成，如菲律宾群岛和印度尼西亚群岛。

　　当这些波浪抵达西部边缘时，它们被反弹回来，该模型预测，罗斯比波将会被分解成为诸多沿海岸流动的Kelvin波，携带着同样的负海平面信号。这些波最终涌向赤道，然后在地球旋转力量的推动下沿赤道以每天250公里的速度往东前进，当足够数量带有充分幅度的Kelvin波自西太平洋水域到达时，它们的负海面信号会压服那个倾向于提高海面的反馈机制，它们开始迫使整个系统转入相反的寒冷模式。这导致产生风向的逐渐转折变化，这一转折变化最终将正海面罗斯比波送往西部，这些罗斯比波将最终作为寒冷的、终结整个周期的正Kelvin波回来，从而引发另一个增温周期。

　　Which of the following best describesthe organization of the first paragraph?

　　A theory is presented and criticized.

　　A model is described and evaluated.

　　A result is reported and its importance explained.

　　A phenomenon is noted¹¹ and its significance debated.

　　A hypothesis is introduced and contrary evidence presented.

　　答案：(C)

　　According to tile passage, which of the following features is characteristic of an EI Nino?

　　Cold coastal water near Pe

　　Winds blowing from the west

　　Random occurrence

　　Worldwide effects

　　Short duration

　　答案：(B)

 

1 apparently   

adv.显然地；表面上，似乎

参考例句：

• An apparently blind alley leads suddenly into an open space.山穷水尽，豁然开朗。
• He was apparently much surprised at the news.他对那个消息显然感到十分惊异。

2 pointed   

adj.尖的，直截了当的

参考例句：

• He gave me a very sharp pointed pencil.他给我一支削得非常尖的铅笔。
• She wished to show Mrs.John Dashwood by this pointed invitation to her brother.她想通过对达茨伍德夫人提出直截了当的邀请向她的哥哥表示出来。

3 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

4 simultaneously   

adv.同时发生地，同时进行地

参考例句：

• The radar beam can track a number of targets almost simultaneously.雷达波几乎可以同时追着多个目标。
• The Windows allow a computer user to execute multiple programs simultaneously.Windows允许计算机用户同时运行多个程序。

5 depressed   

adj.沮丧的，抑郁的，不景气的，萧条的

参考例句：

• When he was depressed,he felt utterly divorced from reality.他心情沮丧时就感到完全脱离了现实。
• His mother was depressed by the sad news.这个坏消息使他的母亲意志消沉。

6 westward   

n.西方，西部；adj.西方的，向西的；adv.向西

参考例句：

• We live on the westward slope of the hill.我们住在这座山的西山坡。
• Explore westward or wherever.向西或到什么别的地方去勘探。

7 coastal   

adj.海岸的，沿海的，沿岸的

参考例句：

• The ocean waves are slowly eating away the coastal rocks.大海的波浪慢慢地侵蚀着岸边的岩石。
• This country will fortify the coastal areas.该国将加强沿海地区的防御。

8 eastward   

adv.向东；adj.向东的；n.东方，东部

参考例句：

• The river here tends eastward.这条河从这里向东流。
• The crowd is heading eastward,believing that they can find gold there.人群正在向东移去，他们认为在那里可以找到黄金。

9 rotation   

n.旋转；循环，轮流

参考例句：

• Crop rotation helps prevent soil erosion.农作物轮作有助于防止水土流失。
• The workers in this workshop do day and night shifts in weekly rotation.这个车间的工人上白班和上夜班每周轮换一次。

10 amplitude   

n.广大；充足；振幅

参考例句：

• The amplitude of the vibration determines the loudness of the sound.振动幅度的大小决定声音的大小。
• The amplitude at the driven end is fixed by the driving mechanism.由于驱动机构的作用,使驱动端的振幅保持不变。

11 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。