09 El Nino
海洋气学：介绍预测厄尔尼诺海流的数学模型
导读
厄尔尼诺（El Nino）是在太平洋的秘鲁和厄瓜多尔沿岸圣诞节前后发生的一种海水温度异常升高的现象。这是一种大规模的海洋和大气相互作用的现象。本文从海洋气学的角度介绍了预测厄尔·尼诺海流的数学模型。
The recent, apparently successful, prediction
by mathematical models of an appearance of El Nino—the warm ocean current that periodically develops along the Pacific coast of South America—has excited researchers. Jacob Bjerknes pointed out over 20 years ago how winds might create either abnormally warm or abnormally cold water in the eastern 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 between appearances of the warm El Nino and the cold 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 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 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 mechanism by driving the warmer surface water into 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 the model is to show that the winds of an El Nino, which raise sea level in the east, simultaneously send a signal to the west lowering sea level. According to the model, that signal is generated as a negative Rossby wave, a wave of depressed, or negative, sea level, that moves westward parallel to the equator at 25 to 85 kilometers per day. Taking months to traverse the Pacific, Rossby 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.
最近，用数学模型对厄尔尼诺海流（沿南美洲太平洋海岸周期产生的暖洋流）的出现进行显然成功的预报，大大激励了气象研究工作者。雅各布·毕尔克内斯在二十多年前就已经指出，风如何可能在东部赤道附近的太平洋洋域中造成反常的暖水流或者反常的冷水流。然而，直到研究出这个数学模型，人们才有可能解释为什么竟然是从一种状态有规则地转变到另一种状态。这种情况发生在暖厄尔尼诺海流和所谓反（冷）厄尔尼诺海流周期交替出现的时候。问题的答案可以从海洋中找到，至少假如当前联系海洋变化同大气变化的模式是正确的话。
长期以来，气象研究工作者都知道：在发生厄尔尼诺现象期间，存在着两个条件：第一，异常暖和的水流沿东太平洋，主要是沿厄瓜多尔和秘鲁海岸扩展；第二，从西方吹来的风，吹进东方暖水流上空升起的更加暖和的气流中。这些风把洋面较暖和的水流聚成“一堆”，阻止东部深海冷水流正常地向上涌出，使得东部水域更加暖和，因而更加加强了这股风的力量，这样有助于造成一个反馈机制。这个模型的贡献是要表明：厄尔尼诺海流的风提高东部的海平面，同时给西方降低的海平面输送一个信号。按照这个模型，这个信号是作为负罗斯比波而产生。负罗斯比波是压低的或负的海平面波，以每天25到85千米的速度平行于赤道向西运动。罗斯比波花费数月的时间横越太平洋，行进到太平洋盆地的西部边界。这个边界在模型被看做是平滑的墙，但事实上是由诸如菲律宾群岛和印度尼西亚群岛这样很不规则的岛屿链组成的。
Sentence Translation
句子翻译
1. 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 between appearances of the warm El Nino and the cold called anti El Nino.
2. According to the model, that signal is generated as a negative Rossby wave, a wave of depressed, or negative, sea level, that moves westward parallel to the equator at 25 to 85 kilometers per day.
Key
1．然而，直到研究出这个数学模型，人们才有可能解释，为什么竟然是从一种状态有规则地转变到另一种状态。这种情况发生在暖厄尔尼诺海流和所谓反（冷）厄尔尼诺海流周期交替出现的时候。
2．按照这个模型，这个信号是作为负罗斯比波而产生。负罗斯比波是压低的或负的海平面波，以每天25到85千米的速度平行于赤道向西运动。
Emulation
美文自己写得出——学生仿写
仿写范例
Should Pets Be Treated as Family Members?
Throughout history, animals have always been great companions to man. Today, we treat our pets as members of family, playing with them and nursing them when they are sick, and I believe that the relationships that people have with their pets are healthy for many reasons.
Firstly, animals provide companionship for people who are too old to maintain regular friendship. It is most common for one spouse to outlive the other. Frequently, the surviving spouse does not remarry, and eventually, all his or her friends die. When one is elderly, it is difficult to make new friends. In this type of situation, having a pet as a companion is greatly preferable to spending all of one's time alone. While a pet cannot speak, it can understand its master's emotions, and usually responds accordingly.
Secondly, animals have been proven to reduce their master's stress. This is probably because an animal is always happy to see its master, and gives the master unconditional love. As long as the master is kind to his/her pet, the pet will be devoted and faithful. A pet also provides a friendly face after a stressful day. For example, I have a pet dog. After taking an exam, the only thing I want to do is to go home and play with my dog. He always brings me much needed cheer and happiness.
Lastly, having an animal can prepare a young couple for children. A young animal is very difficult to take care of. Let us take the example of a puppy. One can never leave a puppy by itself. A puppy must be constantly taken care of; he must be toilet-trained and disciplined. Raising an animal can make one happy and sociable very much like raising a child to possess the same attributes. While a puppy is obviously easier to take care of than a child, it can show the prospective parents where some of the difficulties will lie when raising a baby.
In conclusion, I think having a very close relationship with a pet is healthy. Having a pet can reduce loneliness, stress, and prepare one for the huge experience of having a child. Pets are often referred to as man's best friend, and for good reason.