Rogue waves, long considered rare and mysterious phenomena, have been extensively studied by scientists. A new analysis led by Francesco Fedele at Georgia Tech’s School of Civil and Environmental Engineering sheds light on the physics behind these extreme events.
Researchers assembled 27,500 wave records from 2003 to 2020 in the North Sea, comparing statistics of the largest crests under different sea states. They found that the largest crests match ordinary processes once accounting for direction, frequency spread, and steepness as storms intensify.
Contrary to long-held theories, modulational instability – a mechanism thought to amplify rogue waves – is not a leading explanation in open ocean conditions. Instead, directional spreading plays a central role in dispersing wave energy and disrupting the formation of conditions necessary for modulational instability to dominate.
The study suggests that linear focusing and second-order bound nonlinearities are primary drivers behind the largest observed waves. These mechanisms can boost already tall waves by 15-20 percent relative to linear predictions. The analysis also provides insight into how detection becomes a pattern recognition problem, rather than a physics search.
The findings have implications for ships and offshore structures, highlighting the importance of being prepared for extremes driven by everyday physics. With larger datasets and improved methods, researchers aim to quantify how directional spread, current shear, and depth modulate the chance of constructive alignment without invoking special mechanisms.
Source: https://www.earth.com/news/what-creates-monster-rogue-waves-scientists-identify-a-pattern