什么是疯狗浪?
For centuries, sailors told stories of rogue waves, also called freak waves or killer waves. But scientists have only accepted that they are real in the past few decades.
Scientists call them "extreme storm waves". They are waves that are more than twice the size of the waves around them. They are very hard to predict and often come suddenly from a different direction from the wind and the other waves.
People who have seen rogue waves often describe them as "walls of water". They usually have steep sides, with unusually deep troughs in front of them.
Because these waves are so rare, it is very difficult to measure and study them. Scientists are still investigating exactly how and when they form, but there are several known causes.
The first is called constructive interference. Swells travel across the ocean at different speeds and in different directions. As they pass through one another, their crests and troughs sometimes line up and add together. This can create enormous, towering waves that disappear just as quickly. If the swells are traveling in the same direction, these mountainous waves may last for several minutes.
The second is the focusing of wave energy. When storm waves run into a strong ocean current flowing the other way, the waves are squeezed closer together and can combine into very large rogue waves. This happens in strong currents such as the Gulf Stream in the Atlantic and the Agulhas Current off South Africa. Rogue waves that form this way tend to last longer.
几百年来,水手们一直流传着关于“疯狗浪”的故事,这种浪也被叫作“畸形浪”或“杀人浪”。可是直到最近几十年,科学家才承认它们真的存在。
科学家把它们叫作“极端风暴浪”。这种浪的高度是周围波浪的两倍以上,非常难以预测,而且常常和风向、其他波浪的方向都不一样,突然从别的方向冲过来。
见过疯狗浪的人常常形容它是一堵“水墙”。它们通常浪壁陡峭,前面还有一道异常深的浪谷。
因为这种浪非常罕见,所以很难测量和研究。科学家还在研究它们到底是怎样、在什么时候形成的,不过已经知道了几个原因。
第一个原因叫“相长干涉”。涌浪在海上以不同的速度、朝不同的方向前进。当它们彼此交会时,波峰和波谷有时会刚好对齐、叠加在一起。这样就可能形成高耸的巨浪,但它们消失得也很快。如果涌浪朝着同一个方向前进,这种山一样的巨浪可能会持续好几分钟。
第二个原因是波浪能量的汇聚。当风暴掀起的波浪迎头撞上一股方向相反的强大洋流时,波浪会被挤得更紧密,可能合并成非常大的疯狗浪。这种情况会出现在大西洋的墨西哥湾流、南非外海的厄加勒斯海流这类强大的洋流中。用这种方式形成的疯狗浪,往往持续时间更长。