For example, when swell from a Weddell Sea storm propagates northeastward into the southwestward-flowing Agulhas Current off South Africa, high steep waves are formed. When waves propagate into an opposing current, they grow in height. Northwest of Hawaii, on February 7, 1933, the Navy tanker USS Ramapo encountered the largest open-ocean wind waves ever reliably observed with heights that were reported to be at least 34 m (112 ft). Off the west coast of Canada, there have been several measurements of individual waves with heights around 30 m (100 ft). Such systems of very low atmospheric pressure form in the Gulf of Alaska, the region around Iceland and the Weddell Sea. The highest wind waves are produced by large intense storm systems that last for a day or longer. Equations ( 1 ), ( 2 ), and ( 3 ) assume that the waves present were generated by local wind, with no significant swell present. Such waves, generated by distant storms, are called swell. Waves with long periods (typically 10 s or more) can travel thousands of kilometers with little energy loss. See also: Storm surge Tide TsunamiĪpplies, if a wind blows steadily over a known fetch for a period of time.īecause of viscosity, surface waves lose energy as they propagate, short-period waves being dampened more rapidly than long-period waves. Like tides, they are ubiquitous in the ocean and continue to travel well beyond their area of generation. Wind-generated waves, having periods from a fraction of a second to tens of seconds, are called wind waves. Wakes are waves resulting from relative motion of the water and a solid body, such as the motion of a ship through the sea or the rapid flow of water around a rock. Earthquakes or other large, sudden movements of the Earth's crust can cause waves, called tsunamis, which typically have periods of less than an hour. Storm surges are individual waves produced by the wind and dropping barometric pressure associated with storms they characteristically last several hours. They have long periods, usually 12.42 h for the strongest constituent. Tides are ocean waves induced by the varying gravitational influence of the Moon and Sun. Surface gravity waves may be classified according to the nature of the forces producing them.
0 kommentar(er)
