| has gloss | eng: An infragravity wave is a long-period oceanic wave generated along continental coastlines by nonlinear wave interactions of storm-forced shoreward-propagating ocean swells. These differ from normal oceanic gravity waves, which are created by wind pushing the surface of the sea. Normal gravity waves typically have a frequency on the order of 50 millihertz (i.e., a period of 20 seconds). Interactions of these waves with coastlines filters out the higher frequencies with periods about 30 seconds, but nonlinear processes convert some of this energy to sub-harmonics with periods ranging from 50 to 350 seconds (20 mHz to 3 mHz). Infragravity waves are these sub-harmonics of the impinging gravity waves. |
