ABSTRACT
Waves are undulations formed by wind blowing over a water surface. They are caused by turbulence in airflow generating pressure variations on the water. Once formed, waves help to disturb the airflow and are partly self-sustaining. Energy is transferred from the wind to the water within the wave-generation area. The amount of energy transfer depends upon the wind speed, the wind duration (how long the wind blows), and the fetch (the extent of water over which the wind blows). Sea waves are formed by the wind within the generation area. They often have short crests and steep cross-sections, and are irregular. In mid-ocean, prolonged strong winds associated with severe storms and blowing over hundreds of kilometres produce waves more than 20 m high that travel up to 80 km/hr. On passing out of the generation area, sea waves become swell waves (or simply swell) and they are more regular with longer periods and longer crests. They may travel thousands of kilometres across oceans.
