Mechanism 1: nonlinear wave interactions

A rogue wave is an extremely large wave in the wave train. It also can be defined as the maximum wave that exceeds twice the significant wave height, statistically. The occurrence probability of a rogue wave can be estimated in linear random waves, but the third-order nonlinear wave–wave interactions in deep water can enhance it. On the other hand, wave directionality suppressed nonlinear enhancement on the rogue wave generation. The chapter summarizes the occurrence probability of rogue waves, both linear and nonlinear waves focusing on the open ocean, and shows several examples of applications.