Rogue Waves

Abstract

Rogue waves are surface gravity waves whose wave heights are much larger than expected for the sea state. The most common operational definition requires a rogue wave to be at least twice as large as the significant wave height. Wave refraction by water depth and currents may cause difficult wave conditions in certain local areas, but otherwise, the probability of occurrence of rogue waves appears to be consistent with second-order random-wave theory. There are exceptions, however, though it is unclear whether these represent measurement errors, statistical outliers, or are caused by additional nonlinear physics. A clear deviation from second-order theory is found in 2-D numerical simulations and wave flume experiments, where a higher frequency of occurrence is found due to a nonlinear instability. Recent 3-D simulations and wave basin experiments indicate that such deviations are absent for normal oceanic short-crested waves.