A series of short-period waves bounded by an amplitude envelope of much larger periodicity, corresponding to the superposition of incident waves with slightly differing wave lengths and frequencies.
Incident waves arrive in groups when the wave spectrum contains incident waves with slightly differing wave lengths and frequencies - as is often the case. The superposition of these incident waves forms wave groups, as shown in the figure. Wave groups typically contain 5 - 10 waves. Nonlinear interaction within the wave group generates infragravity waves. Wave groups also cause surf beat.
- OpenUniversity, 1994. Waves, Tides and Shallow-water Processes. Pergamon Press, Oxford