Rogue waves are unusually large, unexpected and suddenly appearing surface waves which are very dangerous to large ships like Ocean liners. The size of the waves larger than the normal waves of the sea or ocean but its sudden appearance with a great force makes it unique among all the waves such as sneaker waves etc. It is popularly known as freak waves, monster waves, episodic waves, killer waves, extreme waves, and abnormal waves.
The appearance of the rogue waves are wall like structure and hence they are categorised as: "Walls of water" travelling up to 10 km (6 mi) through the ocean; "Three Sisters", groups of three waves; Single, giant storm waves, building up to fourfold the storm's waves height and collapsing after some seconds.
Theories related to the formation of Rogue waves
There are numerous theories on the formation of the rogue waves but unable to make concrete document. The most accepted hypothesis is that the rogue waves are the combination of strong current which is accompanied by the high winds, small waves. Some of the famous hypotheses on the formation of rogue waves are discussed below:
1. Diffractive Focusing: According to this hypothesis, the rogue waves are formed by the combination several small waves which give rise to one freak wave.
2. Focusing on Currents or Wave Energy: According to this hypothesis, the rogue waves are formed by the force exerted by the opposing of numerous waves from one current to the normal waves. In other words, it is formed when oncoming waves are compressed together.
3. Nonlinear Effects: This theory opines that the rogue waves are formed by the modulation instability. In other words, when natural non-linear process extract the energy from the adjacent waves and then the waves grows into vertical waves as rogue waves. According to this hypothesis, the phenomenon that soaks energy from the adjacent waves with the backyard then emerged into increase energy waves. This hypothesis equated on the basis of Nonlinear Schrödinger equation (NLS).
4. Constructive Interference: According to this hypothesis, the rogue waves are formed when numerous small swells (undulating movement of the surface of the open sea) moves in same direction pass through each other, their troughs, lengths, and crests collide or alternatively reinforce each other.
5. Freshwater Rogue Waves: It is believe that rogue waves are forms in the deep sea. But an incident of shipwrecks of the 20th century destroyed by the rogue waves in the Lake Superior in North America. In this accident 729-foot ship and the 29 crew were lost due to sudden rise of waves.
6. Wave–current interaction: Some of the oceanographer states that rogue waves are formed by the interaction between surface gravity waves and a mean flow.
Regions Prone to Rogue Waves
1. Bermuda Triangle
2. Triangular region in the Atlantic Ocean stretches off the coast of Bermuda, Florida, and Puerto Rico.
3. Cape Agulhas near the southern tip of the African continent.
4. Indian Ocean, South Atlantic Ocean, and the Southern Ocean.
5. Gulf Stream in the North Atlantic Ocean
Hence, the phenomena of rogue waves are still a matter of research in the oceanographer’s community because numerous theories only postulate the hypothesis without any concrete reason of the formation. It is a topic of research because maritime transport is low-cost and efficient. If we don't predict the rogue waves, then it is so strong that it can disable and sink even the largest ships and oil rigs.