71 El Niño

When you live in an area for a while, you get used to its climate. You know about how cold and wet it will be in March and how warm in August. Sometimes, though, weather conditions occur that create big changes in temperature and rainfall. One of these is called El Niño.

In an El Niño situation the surface water in the eastern Pacific Ocean, near the coast of Peru, gets unusually warm. (This warming occurs around Christmas; “El Niño” is Spanish for “Christ Child.”) Rainfall seems to follow the warm water, so that areas around Peru get floods. But the weather change doesn’t stop there. Regions to the west of the warm water, such as Australia, get very little rain and so experience drought. El Niño also influences the United States. Usually California gets very severe rains. The middle and eastern parts of the country have winters that are much warmer than normal.

El Niños have been occurring for hundreds of years, but people didn’t understand what was happening. It was only in the 1960s that scientists found definite proof that warming in the Pacific affected weather elsewhere. Computers are continuing to compile information about how an El Niño works. We know, for instance, that the condition occurs every two to seven years. Usually it lasts for several months, though sometimes it can last for years. And its effects can vary: some El Niños are much stronger than others. Often an El Niño year is followed by one with a condition called La Niña. In this situation, the Pacific waters get very cold and the weather patterns of El Niño tend to be reversed.

71 厄尔尼诺现象

当你在一个地区生活一段时间后，就会习惯那里的气候。你知道三月会有多冷多湿，八月会有多热。不过，有时会出现导致气温和降雨量发生巨大变化的天气状况，其中一种就是厄尔尼诺现象。

在厄尔尼诺现象发生时，秘鲁海岸附近的东太平洋表层海水会异常变暖。（这种变暖现象发生在圣诞节前后；“El Niño”在西班牙语中是“圣婴”的意思。）降雨似乎会跟随暖水移动，因此秘鲁周边地区会发生洪水。但天气变化并未就此停止。暖水西侧的地区，比如澳大利亚，降雨量极少，因此会遭遇干旱。厄尔尼诺也会影响美国：通常加利福尼亚会出现强降雨，美国中部和东部地区的冬季会比正常情况温暖得多。

厄尔尼诺现象已经存在了数百年，但人们过去并不明白这是怎么回事。直到20世纪60年代，科学家们才找到确切的证据，证明太平洋的变暖会影响其他地区的天气。计算机仍在持续收集关于厄尔尼诺运作方式的信息。例如，我们知道这种现象每2到7年发生一次，通常持续数月，不过有时也会持续数年。它的影响程度各不相同：有些厄尔尼诺现象比其他的要强得多。通常在厄尔尼诺年之后，会出现一种名为拉尼娜的现象，此时太平洋海水会变得非常寒冷，厄尔尼诺的天气模式往往会逆转。