Equilibrium-range constant in wind-generated wave spectra

The equilibrium range in wind-driven wave spectra is characterized to have an f(-4) form in deep water (k(-5/2) shallow-water form). Absolute energy levels for six physically diverse sites are shown to be well fit by an expression involving the wind speed measured at a fraction of a wavelength above the sea surface in combination with the phase speed of the spectral peak. Observed energy levels suggest that nonlinear wave-wave interactions are capable of maintaining the observed energy-flux balance in the equilibrium range.